1 HXCOMM Use
DEFHEADING() to define headings
in both help text and rST
.
2 HXCOMM Text between SRST and ERST is copied to the rST version and
3 HXCOMM discarded from C version
.
4 HXCOMM
DEF(option
, HAS_ARG
/0, opt_enum
, opt_help
, arch_mask
) is used to
5 HXCOMM construct option structures
, enums and help message
for specified
7 HXCOMM HXCOMM can be used
for comments
, discarded from both rST and C
.
9 DEFHEADING(Standard options
:)
11 DEF("help", 0, QEMU_OPTION_h
,
12 "-h or -help display this help and exit\n", QEMU_ARCH_ALL
)
18 DEF("version", 0, QEMU_OPTION_version
,
19 "-version display version information and exit\n", QEMU_ARCH_ALL
)
22 Display version information and exit
25 DEF("machine", HAS_ARG
, QEMU_OPTION_machine
, \
26 "-machine [type=]name[,prop[=value][,...]]\n"
27 " selects emulated machine ('-machine help' for list)\n"
28 " property accel=accel1[:accel2[:...]] selects accelerator\n"
29 " supported accelerators are kvm, xen, hax, hvf, nvmm, whpx or tcg (default: tcg)\n"
30 " vmport=on|off|auto controls emulation of vmport (default: auto)\n"
31 " dump-guest-core=on|off include guest memory in a core dump (default=on)\n"
32 " mem-merge=on|off controls memory merge support (default: on)\n"
33 " aes-key-wrap=on|off controls support for AES key wrapping (default=on)\n"
34 " dea-key-wrap=on|off controls support for DEA key wrapping (default=on)\n"
35 " suppress-vmdesc=on|off disables self-describing migration (default=off)\n"
36 " nvdimm=on|off controls NVDIMM support (default=off)\n"
37 " memory-encryption=@var{} memory encryption object to use (default=none)\n"
38 " hmat=on|off controls ACPI HMAT support (default=off)\n"
39 " memory-backend='backend-id' specifies explicitly provided backend for main RAM (default=none)\n"
40 " cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity]\n"
41 " zpcii-disable=on|off disables zPCI interpretation facilities (default=off)\n",
44 ``
-machine
[type
=]name
[,prop
=value
[,...]]``
45 Select the emulated machine by name
. Use ``
-machine help`` to list
48 For architectures which aim to support live migration compatibility
49 across releases
, each release will introduce a
new versioned machine
50 type
. For example
, the
2.8.0 release introduced machine types
51 "pc-i440fx-2.8" and
"pc-q35-2.8" for the x86\_64
/i686 architectures
.
53 To allow live migration of guests from QEMU version
2.8.0, to QEMU
54 version
2.9.0, the
2.9.0 version must support the
"pc-i440fx-2.8"
55 and
"pc-q35-2.8" machines too
. To allow users live migrating VMs to
56 skip multiple intermediate releases when upgrading
, new releases of
57 QEMU will support machine types from many previous versions
.
59 Supported machine properties are
:
61 ``accel
=accels1
[:accels2
[:...]]``
62 This is used to enable an accelerator
. Depending on the target
63 architecture
, kvm
, xen
, hax
, hvf
, nvmm
, whpx or tcg can be available
.
64 By
default, tcg is used
. If there is more than one accelerator
65 specified
, the next one is used
if the previous one fails to
68 ``vmport
=on|off|auto``
69 Enables emulation of VMWare IO port
, for vmmouse etc
. auto says
70 to select the value based on accel
. For accel
=xen the
default is
71 off otherwise the
default is on
.
73 ``dump
-guest
-core
=on|off``
74 Include guest memory
in a core dump
. The
default is on
.
77 Enables or disables memory merge support
. This feature
, when
78 supported by the host
, de
-duplicates identical memory pages
79 among VMs
instances (enabled by
default).
81 ``aes
-key
-wrap
=on|off``
82 Enables or disables AES key wrapping support on s390
-ccw hosts
.
83 This feature controls whether AES wrapping keys will be created
84 to allow execution of AES cryptographic functions
. The
default
87 ``dea
-key
-wrap
=on|off``
88 Enables or disables DEA key wrapping support on s390
-ccw hosts
.
89 This feature controls whether DEA wrapping keys will be created
90 to allow execution of DEA cryptographic functions
. The
default
94 Enables or disables NVDIMM support
. The
default is off
.
96 ``memory
-encryption
=``
97 Memory encryption object to use
. The
default is none
.
100 Enables or disables ACPI Heterogeneous Memory Attribute Table
101 (HMAT
) support
. The
default is off
.
103 ``memory
-backend
='id'``
104 An alternative to legacy ``
-mem
-path`` and ``mem
-prealloc`` options
.
105 Allows to use a memory backend as main RAM
.
110 -object memory
-backend
-file
,id
=pc
.ram
,size
=512M
,mem
-path
=/hugetlbfs
,prealloc
=on
,share
=on
111 -machine memory
-backend
=pc
.ram
114 Migration compatibility note
:
116 * as backend id one shall use value of
'default-ram-id', advertised by
117 machine
type (available via ``query
-machines`` QMP command
), if migration
118 to
/from old
QEMU (<5.0) is expected
.
119 * for machine types
4.0 and older
, user shall
120 use ``x
-use
-canonical
-path
-for-ramblock
-id
=off`` backend option
121 if migration to
/from old
QEMU (<5.0) is expected
.
126 -object memory
-backend
-ram
,id
=pc
.ram
,size
=512M
,x
-use
-canonical
-path
-for-ramblock
-id
=off
127 -machine memory
-backend
=pc
.ram
130 ``cxl
-fmw
.0.targets
.0=firsttarget
,cxl
-fmw
.0.targets
.1=secondtarget
,cxl
-fmw
.0.size
=size
[,cxl
-fmw
.0.interleave
-granularity
=granularity
]``
131 Define a CXL Fixed Memory
Window (CFMW
).
133 Described
in the CXL
2.0 ECN
: CEDT CFMWS
& QTG _DSM
.
135 They are regions of Host Physical
Addresses (HPA
) on a system which
136 may be interleaved across one or more CXL host bridges
. The system
137 software will assign particular devices into these windows and
138 configure the downstream Host
-managed Device
Memory (HDM
) decoders
139 in root ports
, switch ports and devices appropriately to meet the
140 interleave requirements before enabling the memory devices
.
142 ``targets
.X
=target`` provides the mapping to CXL host bridges
143 which may be identified by the id provied
in the
-device entry
.
144 Multiple entries are needed to specify all the targets when
145 the fixed memory window represents interleaved memory
. X is the
148 ``size
=size`` sets the size of the CFMW
. This must be a multiple of
149 256MiB
. The region will be aligned to
256MiB but the location is
150 platform and configuration dependent
.
152 ``interleave
-granularity
=granularity`` sets the granularity of
153 interleave
. Default
256KiB
. Only
256KiB
, 512KiB
, 1024KiB
, 2048KiB
154 4096KiB
, 8192KiB and
16384KiB granularities supported
.
160 -machine cxl
-fmw
.0.targets
.0=cxl
.0,cxl
-fmw
.0.targets
.1=cxl
.1,cxl
-fmw
.0.size
=128G
,cxl
-fmw
.0.interleave
-granularity
=512k
162 ``zpcii
-disable
=on|off``
163 Disables zPCI interpretation facilties on s390
-ccw hosts
.
164 This feature can be used to disable hardware virtual assists
165 related to zPCI devices
. The
default is off
.
168 DEF("M", HAS_ARG
, QEMU_OPTION_M
,
169 " sgx-epc.0.memdev=memid,sgx-epc.0.node=numaid\n",
173 ``sgx
-epc
.0.memdev
=@
var{memid
},sgx
-epc
.0.node
=@
var{numaid
}``
174 Define an SGX EPC section
.
177 DEF("cpu", HAS_ARG
, QEMU_OPTION_cpu
,
178 "-cpu cpu select CPU ('-cpu help' for list)\n", QEMU_ARCH_ALL
)
181 Select CPU
model (``
-cpu help``
for list and additional feature
185 DEF("accel", HAS_ARG
, QEMU_OPTION_accel
,
186 "-accel [accel=]accelerator[,prop[=value][,...]]\n"
187 " select accelerator (kvm, xen, hax, hvf, nvmm, whpx or tcg; use 'help' for a list)\n"
188 " igd-passthru=on|off (enable Xen integrated Intel graphics passthrough, default=off)\n"
189 " kernel-irqchip=on|off|split controls accelerated irqchip support (default=on)\n"
190 " kvm-shadow-mem=size of KVM shadow MMU in bytes\n"
191 " split-wx=on|off (enable TCG split w^x mapping)\n"
192 " tb-size=n (TCG translation block cache size)\n"
193 " dirty-ring-size=n (KVM dirty ring GFN count, default 0)\n"
194 " notify-vmexit=run|internal-error|disable,notify-window=n (enable notify VM exit and set notify window, x86 only)\n"
195 " thread=single|multi (enable multi-threaded TCG)\n", QEMU_ARCH_ALL
)
197 ``
-accel name
[,prop
=value
[,...]]``
198 This is used to enable an accelerator
. Depending on the target
199 architecture
, kvm
, xen
, hax
, hvf
, nvmm
, whpx or tcg can be available
. By
200 default, tcg is used
. If there is more than one accelerator
201 specified
, the next one is used
if the previous one fails to
204 ``igd
-passthru
=on|off``
205 When Xen is
in use
, this option controls whether Intel
206 integrated graphics devices can be passed through to the guest
209 ``kernel
-irqchip
=on|off|split``
210 Controls KVM
in-kernel irqchip support
. The
default is full
211 acceleration of the interrupt controllers
. On x86
, split irqchip
212 reduces the kernel attack surface
, at a performance cost
for
213 non
-MSI interrupts
. Disabling the
in-kernel irqchip completely
214 is not recommended except
for debugging purposes
.
216 ``kvm
-shadow
-mem
=size``
217 Defines the size of the KVM shadow MMU
.
220 Controls the use of split w^x mapping
for the TCG code generation
221 buffer
. Some operating systems require
this to be enabled
, and
in
222 such a
case this will
default on
. On other operating systems
, this
223 will
default off
, but one may enable
this for testing or debugging
.
226 Controls the
size (in MiB
) of the TCG translation block cache
.
228 ``thread
=single|multi``
229 Controls number of TCG threads
. When the TCG is multi
-threaded
230 there will be one thread per vCPU therefore taking advantage of
231 additional host cores
. The
default is to enable multi
-threading
232 where both the back
-end and front
-ends support it and no
233 incompatible TCG features have been
enabled (e
.g
.
236 ``dirty
-ring
-size
=n``
237 When the KVM accelerator is used
, it controls the size of the per
-vCPU
238 dirty page ring
buffer (number of entries
for each vCPU
). It should
239 be a value that is power of two
, and it should be
1024 or
bigger (but
240 still less than the maximum value that the kernel supports
). 4096
241 could be a good initial value
if you have no idea which is the best
.
242 Set
this value to
0 to disable the feature
. By
default, this feature
243 is
disabled (dirty
-ring
-size
=0). When enabled
, KVM will instead
244 record dirty pages
in a bitmap
.
246 ``notify
-vmexit
=run|internal
-error|disable
,notify
-window
=n``
247 Enables or disables notify VM exit support on x86 host and specify
248 the corresponding notify window to trigger the VM exit
if enabled
.
249 ``run`` option enables the feature
. It does nothing and
continue
250 if the exit happens
. ``internal
-error`` option enables the feature
.
251 It raises a internal error
. ``disable`` option doesn
't enable the feature.
252 This feature can mitigate the CPU stuck issue due to event windows don't
253 open up
for a specified of
time (i
.e
. notify
-window
).
254 Default
: notify
-vmexit
=run
,notify
-window
=0.
258 DEF("smp", HAS_ARG
, QEMU_OPTION_smp
,
259 "-smp [[cpus=]n][,maxcpus=maxcpus][,sockets=sockets][,dies=dies][,clusters=clusters][,cores=cores][,threads=threads]\n"
260 " set the number of initial CPUs to 'n' [default=1]\n"
261 " maxcpus= maximum number of total CPUs, including\n"
262 " offline CPUs for hotplug, etc\n"
263 " sockets= number of sockets on the machine board\n"
264 " dies= number of dies in one socket\n"
265 " clusters= number of clusters in one die\n"
266 " cores= number of cores in one cluster\n"
267 " threads= number of threads in one core\n"
268 "Note: Different machines may have different subsets of the CPU topology\n"
269 " parameters supported, so the actual meaning of the supported parameters\n"
270 " will vary accordingly. For example, for a machine type that supports a\n"
271 " three-level CPU hierarchy of sockets/cores/threads, the parameters will\n"
272 " sequentially mean as below:\n"
273 " sockets means the number of sockets on the machine board\n"
274 " cores means the number of cores in one socket\n"
275 " threads means the number of threads in one core\n"
276 " For a particular machine type board, an expected CPU topology hierarchy\n"
277 " can be defined through the supported sub-option. Unsupported parameters\n"
278 " can also be provided in addition to the sub-option, but their values\n"
279 " must be set as 1 in the purpose of correct parsing.\n",
282 ``
-smp
[[cpus
=]n
][,maxcpus
=maxcpus
][,sockets
=sockets
][,dies
=dies
][,clusters
=clusters
][,cores
=cores
][,threads
=threads
]``
283 Simulate a SMP system with
'\ ``n``\ ' CPUs initially present on
284 the machine type board
. On boards supporting CPU hotplug
, the optional
285 '\ ``maxcpus``\ ' parameter can be set to enable further CPUs to be
286 added at runtime
. When both parameters are omitted
, the maximum number
287 of CPUs will be calculated from the provided topology members and the
288 initial CPU count will match the maximum number
. When only one of them
289 is given then the omitted one will be set to its counterpart
's value.
290 Both parameters may be specified, but the maximum number of CPUs must
291 be equal to or greater than the initial CPU count. Product of the
292 CPU topology hierarchy must be equal to the maximum number of CPUs.
293 Both parameters are subject to an upper limit that is determined by
294 the specific machine type chosen.
296 To control reporting of CPU topology information, values of the topology
297 parameters can be specified. Machines may only support a subset of the
298 parameters and different machines may have different subsets supported
299 which vary depending on capacity of the corresponding CPU targets. So
300 for a particular machine type board, an expected topology hierarchy can
301 be defined through the supported sub-option. Unsupported parameters can
302 also be provided in addition to the sub-option, but their values must be
303 set as 1 in the purpose of correct parsing.
305 Either the initial CPU count, or at least one of the topology parameters
306 must be specified. The specified parameters must be greater than zero,
307 explicit configuration like "cpus=0" is not allowed. Values for any
308 omitted parameters will be computed from those which are given.
310 For example, the following sub-option defines a CPU topology hierarchy
311 (2 sockets totally on the machine, 2 cores per socket, 2 threads per
312 core) for a machine that only supports sockets/cores/threads.
313 Some members of the option can be omitted but their values will be
314 automatically computed:
318 -smp 8,sockets=2,cores=2,threads=2,maxcpus=8
320 The following sub-option defines a CPU topology hierarchy (2 sockets
321 totally on the machine, 2 dies per socket, 2 cores per die, 2 threads
322 per core) for PC machines which support sockets/dies/cores/threads.
323 Some members of the option can be omitted but their values will be
324 automatically computed:
328 -smp 16,sockets=2,dies=2,cores=2,threads=2,maxcpus=16
330 The following sub-option defines a CPU topology hierarchy (2 sockets
331 totally on the machine, 2 clusters per socket, 2 cores per cluster,
332 2 threads per core) for ARM virt machines which support sockets/clusters
333 /cores/threads. Some members of the option can be omitted but their values
334 will be automatically computed:
338 -smp 16,sockets=2,clusters=2,cores=2,threads=2,maxcpus=16
340 Historically preference was given to the coarsest topology parameters
341 when computing missing values (ie sockets preferred over cores, which
342 were preferred over threads), however, this behaviour is considered
343 liable to change. Prior to 6.2 the preference was sockets over cores
344 over threads. Since 6.2 the preference is cores over sockets over threads.
346 For example, the following option defines a machine board with 2 sockets
347 of 1 core before 6.2 and 1 socket of 2 cores after 6.2:
354 DEF("numa", HAS_ARG, QEMU_OPTION_numa,
355 "-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=node]\n"
356 "-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=node]\n"
357 "-numa dist,src=source,dst=destination,val=distance\n"
358 "-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]\n"
359 "-numa hmat-lb,initiator=node,target=node,hierarchy=memory|first-level|second-level|third-level,data-type=access-latency|read-latency|write-latency[,latency=lat][,bandwidth=bw]\n"
360 "-numa hmat-cache,node-id=node,size=size,level=level[,associativity=none|direct|complex][,policy=none|write-back|write-through][,line=size]\n",
363 ``-numa node[,mem=size][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]``
365 ``-numa node[,memdev=id][,cpus=firstcpu[-lastcpu]][,nodeid=node][,initiator=initiator]``
367 ``-numa dist,src=source,dst=destination,val=distance``
369 ``-numa cpu,node-id=node[,socket-id=x][,core-id=y][,thread-id=z]``
371 ``-numa hmat-lb,initiator=node,target=node,hierarchy=hierarchy,data-type=tpye[,latency=lat][,bandwidth=bw]``
373 ``-numa hmat-cache,node-id=node,size=size,level=level[,associativity=str][,policy=str][,line=size]``
374 Define a NUMA node and assign RAM and VCPUs to it. Set the NUMA
375 distance from a source node to a destination node. Set the ACPI
376 Heterogeneous Memory Attributes for the given nodes.
378 Legacy VCPU assignment uses '\ ``cpus``\
' option where firstcpu and
379 lastcpu are CPU indexes. Each '\ ``cpus``\
' option represent a
380 contiguous range of CPU indexes (or a single VCPU if lastcpu is
381 omitted). A non-contiguous set of VCPUs can be represented by
382 providing multiple '\ ``cpus``\
' options. If '\ ``cpus``\
' is
383 omitted on all nodes, VCPUs are automatically split between them.
385 For example, the following option assigns VCPUs 0, 1, 2 and 5 to a
390 -numa node,cpus=0-2,cpus=5
392 '\ ``cpu``\
' option is a new alternative to '\ ``cpus``\
' option
393 which uses '\ ``socket
-id|core
-id|thread
-id``\
' properties to
394 assign CPU objects to a node using topology layout properties of
395 CPU. The set of properties is machine specific, and depends on used
396 machine type/'\ ``smp``\
' options. It could be queried with
397 '\ ``hotpluggable
-cpus``\
' monitor command. '\ ``node
-id``\
'
398 property specifies node to which CPU object will be assigned, it's
399 required
for node to be declared with
'\ ``node``\ ' option before
400 it
's used with '\ ``cpu``\
' option.
407 -smp 1,sockets=2,maxcpus=2 \
408 -numa node,nodeid=0 -numa node,nodeid=1 \
409 -numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
411 Legacy '\ ``mem``\
' assigns a given RAM amount to a node (not supported
412 for 5.1 and newer machine types). '\ ``memdev``\
' assigns RAM from
413 a given memory backend device to a node. If '\ ``mem``\
' and
414 '\ ``memdev``\
' are omitted in all nodes, RAM is split equally between them.
417 '\ ``mem``\
' and '\ ``memdev``\
' are mutually exclusive.
418 Furthermore, if one node uses '\ ``memdev``\
', all of them have to
421 '\ ``initiator``\
' is an additional option that points to an
422 initiator NUMA node that has best performance (the lowest latency or
423 largest bandwidth) to this NUMA node. Note that this option can be
424 set only when the machine property 'hmat
' is set to 'on
'.
426 Following example creates a machine with 2 NUMA nodes, node 0 has
427 CPU. node 1 has only memory, and its initiator is node 0. Note that
428 because node 0 has CPU, by default the initiator of node 0 is itself
434 -m 2G,slots=2,maxmem=4G \
435 -object memory-backend-ram,size=1G,id=m0 \
436 -object memory-backend-ram,size=1G,id=m1 \
437 -numa node,nodeid=0,memdev=m0 \
438 -numa node,nodeid=1,memdev=m1,initiator=0 \
439 -smp 2,sockets=2,maxcpus=2 \
440 -numa cpu,node-id=0,socket-id=0 \
441 -numa cpu,node-id=0,socket-id=1
443 source and destination are NUMA node IDs. distance is the NUMA
444 distance from source to destination. The distance from a node to
445 itself is always 10. If any pair of nodes is given a distance, then
446 all pairs must be given distances. Although, when distances are only
447 given in one direction for each pair of nodes, then the distances in
448 the opposite directions are assumed to be the same. If, however, an
449 asymmetrical pair of distances is given for even one node pair, then
450 all node pairs must be provided distance values for both directions,
451 even when they are symmetrical. When a node is unreachable from
452 another node, set the pair's distance to
255.
454 Note that the
-``numa`` option doesn
't allocate any of the specified
455 resources, it just assigns existing resources to NUMA nodes. This
456 means that one still has to use the ``-m``, ``-smp`` options to
457 allocate RAM and VCPUs respectively.
459 Use '\ ``hmat
-lb``\
' to set System Locality Latency and Bandwidth
460 Information between initiator and target NUMA nodes in ACPI
461 Heterogeneous Attribute Memory Table (HMAT). Initiator NUMA node can
462 create memory requests, usually it has one or more processors.
463 Target NUMA node contains addressable memory.
465 In '\ ``hmat
-lb``\
' option, node are NUMA node IDs. hierarchy is
466 the memory hierarchy of the target NUMA node: if hierarchy is
467 'memory
', the structure represents the memory performance; if
468 hierarchy is 'first
-level\|second
-level\|third
-level
', this
469 structure represents aggregated performance of memory side caches
470 for each domain. type of 'data
-type
' is type of data represented by
471 this structure instance: if 'hierarchy
' is 'memory
', 'data
-type
' is
472 'access\|read\|write
' latency or 'access\|read\|write
' bandwidth of
473 the target memory; if 'hierarchy
' is
474 'first
-level\|second
-level\|third
-level
', 'data
-type
' is
475 'access\|read\|write
' hit latency or 'access\|read\|write
' hit
476 bandwidth of the target memory side cache.
478 lat is latency value in nanoseconds. bw is bandwidth value, the
479 possible value and units are NUM[M\|G\|T], mean that the bandwidth
480 value are NUM byte per second (or MB/s, GB/s or TB/s depending on
481 used suffix). Note that if latency or bandwidth value is 0, means
482 the corresponding latency or bandwidth information is not provided.
484 In '\ ``hmat
-cache``\
' option, node-id is the NUMA-id of the memory
485 belongs. size is the size of memory side cache in bytes. level is
486 the cache level described in this structure, note that the cache
487 level 0 should not be used with '\ ``hmat
-cache``\
' option.
488 associativity is the cache associativity, the possible value is
489 'none
/direct(direct
-mapped
)/complex(complex cache indexing
)'. policy
490 is the write policy. line is the cache Line size in bytes.
492 For example, the following options describe 2 NUMA nodes. Node 0 has
493 2 cpus and a ram, node 1 has only a ram. The processors in node 0
494 access memory in node 0 with access-latency 5 nanoseconds,
495 access-bandwidth is 200 MB/s; The processors in NUMA node 0 access
496 memory in NUMA node 1 with access-latency 10 nanoseconds,
497 access-bandwidth is 100 MB/s. And for memory side cache information,
498 NUMA node 0 and 1 both have 1 level memory cache, size is 10KB,
499 policy is write-back, the cache Line size is 8 bytes:
505 -object memory-backend-ram,size=1G,id=m0 \
506 -object memory-backend-ram,size=1G,id=m1 \
507 -smp 2,sockets=2,maxcpus=2 \
508 -numa node,nodeid=0,memdev=m0 \
509 -numa node,nodeid=1,memdev=m1,initiator=0 \
510 -numa cpu,node-id=0,socket-id=0 \
511 -numa cpu,node-id=0,socket-id=1 \
512 -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=5 \
513 -numa hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=200M \
514 -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=10 \
515 -numa hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=100M \
516 -numa hmat-cache,node-id=0,size=10K,level=1,associativity=direct,policy=write-back,line=8 \
517 -numa hmat-cache,node-id=1,size=10K,level=1,associativity=direct,policy=write-back,line=8
520 DEF("add-fd", HAS_ARG, QEMU_OPTION_add_fd,
521 "-add-fd fd=fd,set=set[,opaque=opaque]\n"
522 " Add 'fd
' to fd 'set
'\n", QEMU_ARCH_ALL)
524 ``-add-fd fd=fd,set=set[,opaque=opaque]``
525 Add a file descriptor to an fd set. Valid options are:
528 This option defines the file descriptor of which a duplicate is
529 added to fd set. The file descriptor cannot be stdin, stdout, or
533 This option defines the ID of the fd set to add the file
537 This option defines a free-form string that can be used to
540 You can open an image using pre-opened file descriptors from an fd
546 -add-fd fd=3,set=2,opaque="rdwr:/path/to/file" \\
547 -add-fd fd=4,set=2,opaque="rdonly:/path/to/file" \\
548 -drive file=/dev/fdset/2,index=0,media=disk
551 DEF("set", HAS_ARG, QEMU_OPTION_set,
552 "-set group.id.arg=value\n"
553 " set <arg> parameter for item <id> of type <group>\n"
554 " i.e. -set drive.$id.file=/path/to/image\n", QEMU_ARCH_ALL)
556 ``-set group.id.arg=value``
557 Set parameter arg for item id of type group
560 DEF("global", HAS_ARG, QEMU_OPTION_global,
561 "-global driver.property=value\n"
562 "-global driver=driver,property=property,value=value\n"
563 " set a global default for a driver property\n",
566 ``-global driver.prop=value``
568 ``-global driver=driver,property=property,value=value``
569 Set default value of driver's property prop to value
, e
.g
.:
573 |qemu_system_x86|
-global ide
-hd
.physical_block_size
=4096 disk
-image
.img
575 In particular
, you can use
this to set driver properties
for devices
576 which are created automatically by the machine model
. To create a
577 device which is not created automatically and set properties on it
,
580 -global driver
.prop
=value is shorthand
for -global
581 driver
=driver
,property
=prop
,value
=value
. The longhand syntax works
582 even when driver contains a dot
.
585 DEF("boot", HAS_ARG
, QEMU_OPTION_boot
,
586 "-boot [order=drives][,once=drives][,menu=on|off]\n"
587 " [,splash=sp_name][,splash-time=sp_time][,reboot-timeout=rb_time][,strict=on|off]\n"
588 " 'drives': floppy (a), hard disk (c), CD-ROM (d), network (n)\n"
589 " 'sp_name': the file's name that would be passed to bios as logo picture, if menu=on\n"
590 " 'sp_time': the period that splash picture last if menu=on, unit is ms\n"
591 " 'rb_timeout': the timeout before guest reboot when boot failed, unit is ms\n",
594 ``
-boot
[order
=drives
][,once
=drives
][,menu
=on|off
][,splash
=sp_name
][,splash
-time
=sp_time
][,reboot
-timeout
=rb_timeout
][,strict
=on|off
]``
595 Specify boot order drives as a string of drive letters
. Valid drive
596 letters depend on the target architecture
. The x86 PC uses
: a
, b
597 (floppy
1 and
2), c (first hard disk
), d (first CD
-ROM
), n
-p
598 (Etherboot from network adapter
1-4), hard disk boot is the
default.
599 To apply a particular boot order only on the first startup
, specify
600 it via ``once``
. Note that the ``order`` or ``once`` parameter
601 should not be used together with the ``bootindex`` property of
602 devices
, since the firmware implementations normally
do not support
603 both at the same time
.
605 Interactive boot menus
/prompts can be enabled via ``menu
=on`` as far
606 as firmware
/BIOS supports them
. The
default is non
-interactive boot
.
608 A splash picture could be passed to bios
, enabling user to show it
609 as logo
, when option splash
=sp\_name is given and menu
=on
, If
610 firmware
/BIOS supports them
. Currently Seabios
for X86 system
611 support it
. limitation
: The splash file could be a jpeg file or a
612 BMP file
in 24 BPP
format(true color
). The resolution should be
613 supported by the SVGA mode
, so the recommended is
320x240
, 640x480
,
616 A timeout could be passed to bios
, guest will pause
for rb\_timeout
617 ms when boot failed
, then reboot
. If rb\_timeout is
'-1', guest will
618 not reboot
, qemu passes
'-1' to bios by
default. Currently Seabios
619 for X86 system support it
.
621 Do strict boot via ``strict
=on`` as far as firmware
/BIOS supports
622 it
. This only effects when boot priority is changed by bootindex
623 options
. The
default is non
-strict boot
.
627 #
try to boot from network first
, then from hard disk
628 |qemu_system_x86|
-boot order
=nc
629 # boot from CD
-ROM first
, switch back to
default order after reboot
630 |qemu_system_x86|
-boot once
=d
631 # boot with a splash picture
for 5 seconds
.
632 |qemu_system_x86|
-boot menu
=on
,splash
=/root
/boot
.bmp
,splash
-time
=5000
634 Note
: The legacy format
'-boot drives' is still supported but its
635 use is discouraged as it may be removed from future versions
.
638 DEF("m", HAS_ARG
, QEMU_OPTION_m
,
639 "-m [size=]megs[,slots=n,maxmem=size]\n"
640 " configure guest RAM\n"
641 " size: initial amount of guest memory\n"
642 " slots: number of hotplug slots (default: none)\n"
643 " maxmem: maximum amount of guest memory (default: none)\n"
644 "NOTE: Some architectures might enforce a specific granularity\n",
647 ``
-m
[size
=]megs
[,slots
=n
,maxmem
=size
]``
648 Sets guest startup RAM size to megs megabytes
. Default is
128 MiB
.
649 Optionally
, a suffix of
"M" or
"G" can be used to signify a value
in
650 megabytes or gigabytes respectively
. Optional pair slots
, maxmem
651 could be used to set amount of hotpluggable memory slots and maximum
652 amount of memory
. Note that maxmem must be aligned to the page size
.
654 For example
, the following command
-line sets the guest startup RAM
655 size to
1GB
, creates
3 slots to hotplug additional memory and sets
656 the maximum memory the guest can reach to
4GB
:
660 |qemu_system|
-m
1G
,slots
=3,maxmem
=4G
662 If slots and maxmem are not specified
, memory hotplug won
't be
663 enabled and the guest startup RAM will never increase.
666 DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
667 "-mem-path FILE provide backing storage for guest RAM\n", QEMU_ARCH_ALL)
670 Allocate guest RAM from a temporarily created file in path.
673 DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
674 "-mem-prealloc preallocate guest memory (use with -mem-path)\n",
678 Preallocate memory when using -mem-path.
681 DEF("k", HAS_ARG, QEMU_OPTION_k,
682 "-k language use keyboard layout (for example 'fr
' for French)\n",
686 Use keyboard layout language (for example ``fr`` for French). This
687 option is only needed where it is not easy to get raw PC keycodes
688 (e.g. on Macs, with some X11 servers or with a VNC or curses
689 display). You don't normally need to use it on PC
/Linux or
692 The available layouts are
:
696 ar de
-ch es fo fr
-ca hu ja mk no pt
-br sv
697 da en
-gb et fr fr
-ch is lt nl pl ru th
698 de en
-us fi fr
-be hr it lv nl
-be pt sl tr
700 The
default is ``en
-us``
.
704 HXCOMM Deprecated by
-audiodev
705 DEF("audio-help", 0, QEMU_OPTION_audio_help
,
706 "-audio-help show -audiodev equivalent of the currently specified audio settings\n",
710 Will show the
-audiodev equivalent of the currently specified
711 (deprecated
) environment variables
.
714 DEF("audio", HAS_ARG
, QEMU_OPTION_audio
,
715 "-audio [driver=]driver,model=value[,prop[=value][,...]]\n"
716 " specifies the audio backend and device to use;\n"
717 " apart from 'model', options are the same as for -audiodev.\n"
718 " use '-audio model=help' to show possible devices.\n",
721 ``
-audio
[driver
=]driver
,model
=value
[,prop
[=value
][,...]]``
722 This option is a shortcut
for configuring both the guest audio
723 hardware and the host audio backend
in one go
.
724 The driver option is the same as with the corresponding ``
-audiodev`` option below
.
725 The guest hardware model can be set with ``model
=modelname``
.
727 Use ``driver
=help`` to list the available drivers
,
728 and ``model
=help`` to list the available device types
.
730 The following two example
do exactly the same
, to show how ``
-audio``
731 can be used to shorten the command line length
:
735 |qemu_system|
-audiodev pa
,id
=pa
-device sb16
,audiodev
=pa
736 |qemu_system|
-audio pa
,model
=sb16
739 DEF("audiodev", HAS_ARG
, QEMU_OPTION_audiodev
,
740 "-audiodev [driver=]driver,id=id[,prop[=value][,...]]\n"
741 " specifies the audio backend to use\n"
742 " Use ``-audiodev help`` to list the available drivers\n"
743 " id= identifier of the backend\n"
744 " timer-period= timer period in microseconds\n"
745 " in|out.mixing-engine= use mixing engine to mix streams inside QEMU\n"
746 " in|out.fixed-settings= use fixed settings for host audio\n"
747 " in|out.frequency= frequency to use with fixed settings\n"
748 " in|out.channels= number of channels to use with fixed settings\n"
749 " in|out.format= sample format to use with fixed settings\n"
750 " valid values: s8, s16, s32, u8, u16, u32, f32\n"
751 " in|out.voices= number of voices to use\n"
752 " in|out.buffer-length= length of buffer in microseconds\n"
753 "-audiodev none,id=id,[,prop[=value][,...]]\n"
754 " dummy driver that discards all output\n"
755 #ifdef CONFIG_AUDIO_ALSA
756 "-audiodev alsa,id=id[,prop[=value][,...]]\n"
757 " in|out.dev= name of the audio device to use\n"
758 " in|out.period-length= length of period in microseconds\n"
759 " in|out.try-poll= attempt to use poll mode\n"
760 " threshold= threshold (in microseconds) when playback starts\n"
762 #ifdef CONFIG_AUDIO_COREAUDIO
763 "-audiodev coreaudio,id=id[,prop[=value][,...]]\n"
764 " in|out.buffer-count= number of buffers\n"
766 #ifdef CONFIG_AUDIO_DSOUND
767 "-audiodev dsound,id=id[,prop[=value][,...]]\n"
768 " latency= add extra latency to playback in microseconds\n"
770 #ifdef CONFIG_AUDIO_OSS
771 "-audiodev oss,id=id[,prop[=value][,...]]\n"
772 " in|out.dev= path of the audio device to use\n"
773 " in|out.buffer-count= number of buffers\n"
774 " in|out.try-poll= attempt to use poll mode\n"
775 " try-mmap= try using memory mapped access\n"
776 " exclusive= open device in exclusive mode\n"
777 " dsp-policy= set timing policy (0..10), -1 to use fragment mode\n"
779 #ifdef CONFIG_AUDIO_PA
780 "-audiodev pa,id=id[,prop[=value][,...]]\n"
781 " server= PulseAudio server address\n"
782 " in|out.name= source/sink device name\n"
783 " in|out.latency= desired latency in microseconds\n"
785 #ifdef CONFIG_AUDIO_SDL
786 "-audiodev sdl,id=id[,prop[=value][,...]]\n"
787 " in|out.buffer-count= number of buffers\n"
789 #ifdef CONFIG_AUDIO_SNDIO
790 "-audiodev sndio,id=id[,prop[=value][,...]]\n"
793 "-audiodev spice,id=id[,prop[=value][,...]]\n"
795 #ifdef CONFIG_DBUS_DISPLAY
796 "-audiodev dbus,id=id[,prop[=value][,...]]\n"
798 "-audiodev wav,id=id[,prop[=value][,...]]\n"
799 " path= path of wav file to record\n",
802 ``
-audiodev
[driver
=]driver
,id
=id
[,prop
[=value
][,...]]``
803 Adds a
new audio backend driver identified by id
. There are global
804 and driver specific properties
. Some values can be set differently
805 for input and output
, they
're marked with ``in|out.``. You can set
806 the input's property with ``
in.prop`` and the output
's property with
807 ``out.prop``. For example:
811 -audiodev alsa,id=example,in.frequency=44110,out.frequency=8000
812 -audiodev alsa,id=example,out.channels=1 # leaves in.channels unspecified
814 NOTE: parameter validation is known to be incomplete, in many cases
815 specifying an invalid option causes QEMU to print an error message
816 and continue emulation without sound.
818 Valid global options are:
821 Identifies the audio backend.
823 ``timer-period=period``
824 Sets the timer period used by the audio subsystem in
825 microseconds. Default is 10000 (10 ms).
827 ``in|out.mixing-engine=on|off``
828 Use QEMU's mixing engine to mix all streams inside QEMU and
829 convert audio formats when not supported by the backend
. When
830 off
, fixed
-settings must be off too
. Note that disabling
this
831 option means that the selected backend must support multiple
832 streams and the audio formats used by the virtual cards
,
833 otherwise you
'll get no sound. It's not recommended to disable
834 this option unless you want to use
5.1 or
7.1 audio
, as mixing
835 engine only supports mono and stereo audio
. Default is on
.
837 ``
in|out
.fixed
-settings
=on|off``
838 Use fixed settings
for host audio
. When off
, it will change
839 based on how the guest opens the sound card
. In
this case you
840 must not specify frequency
, channels or format
. Default is on
.
842 ``
in|out
.frequency
=frequency``
843 Specify the frequency to use when
using fixed
-settings
. Default
846 ``
in|out
.channels
=channels``
847 Specify the number of channels to use when
using fixed
-settings
.
848 Default is
2 (stereo
).
850 ``
in|out
.format
=format``
851 Specify the sample format to use when
using fixed
-settings
.
852 Valid values are
: ``s8``
, ``s16``
, ``s32``
, ``u8``
, ``u16``
,
853 ``u32``
, ``f32``
. Default is ``s16``
.
855 ``
in|out
.voices
=voices``
856 Specify the number of voices to use
. Default is
1.
858 ``
in|out
.buffer
-length
=usecs``
859 Sets the size of the buffer
in microseconds
.
861 ``
-audiodev none
,id
=id
[,prop
[=value
][,...]]``
862 Creates a dummy backend that discards all outputs
. This backend has
863 no backend specific properties
.
865 ``
-audiodev alsa
,id
=id
[,prop
[=value
][,...]]``
866 Creates backend
using the ALSA
. This backend is only available on
869 ALSA specific options are
:
871 ``
in|out
.dev
=device``
872 Specify the ALSA device to use
for input and
/or output
. Default
875 ``
in|out
.period
-length
=usecs``
876 Sets the period length
in microseconds
.
878 ``
in|out
.try-poll
=on|off``
879 Attempt to use poll mode with the device
. Default is on
.
881 ``threshold
=threshold``
882 Threshold (in microseconds
) when playback starts
. Default is
0.
884 ``
-audiodev coreaudio
,id
=id
[,prop
[=value
][,...]]``
885 Creates a backend
using Apple
's Core Audio. This backend is only
886 available on Mac OS and only supports playback.
888 Core Audio specific options are:
890 ``in|out.buffer-count=count``
891 Sets the count of the buffers.
893 ``-audiodev dsound,id=id[,prop[=value][,...]]``
894 Creates a backend using Microsoft's DirectSound
. This backend is
895 only available on Windows and only supports playback
.
897 DirectSound specific options are
:
900 Add extra usecs microseconds latency to playback
. Default is
903 ``
-audiodev oss
,id
=id
[,prop
[=value
][,...]]``
904 Creates a backend
using OSS
. This backend is available on most
907 OSS specific options are
:
909 ``
in|out
.dev
=device``
910 Specify the file name of the OSS device to use
. Default is
913 ``
in|out
.buffer
-count
=count``
914 Sets the count of the buffers
.
916 ``
in|out
.try-poll
=on|of``
917 Attempt to use poll mode with the device
. Default is on
.
920 Try
using memory mapped device access
. Default is off
.
923 Open the device
in exclusive
mode (vmix won
't work in this
924 case). Default is off.
926 ``dsp-policy=policy``
927 Sets the timing policy (between 0 and 10, where smaller number
928 means smaller latency but higher CPU usage). Use -1 to use
929 buffer sizes specified by ``buffer`` and ``buffer-count``. This
930 option is ignored if you do not have OSS 4. Default is 5.
932 ``-audiodev pa,id=id[,prop[=value][,...]]``
933 Creates a backend using PulseAudio. This backend is available on
936 PulseAudio specific options are:
939 Sets the PulseAudio server to connect to.
942 Use the specified source/sink for recording/playback.
944 ``in|out.latency=usecs``
945 Desired latency in microseconds. The PulseAudio server will try
946 to honor this value but actual latencies may be lower or higher.
948 ``-audiodev sdl,id=id[,prop[=value][,...]]``
949 Creates a backend using SDL. This backend is available on most
950 systems, but you should use your platform's native backend
if
953 SDL specific options are
:
955 ``
in|out
.buffer
-count
=count``
956 Sets the count of the buffers
.
958 ``
-audiodev sndio
,id
=id
[,prop
[=value
][,...]]``
959 Creates a backend
using SNDIO
. This backend is available on
960 OpenBSD and most other Unix
-like systems
.
962 Sndio specific options are
:
964 ``
in|out
.dev
=device``
965 Specify the sndio device to use
for input and
/or output
. Default
968 ``
in|out
.latency
=usecs``
969 Sets the desired period length
in microseconds
.
971 ``
-audiodev spice
,id
=id
[,prop
[=value
][,...]]``
972 Creates a backend that sends audio through SPICE
. This backend
973 requires ``
-spice`` and automatically selected
in that
case, so
974 usually you can ignore
this option
. This backend has no backend
977 ``
-audiodev wav
,id
=id
[,prop
[=value
][,...]]``
978 Creates a backend that writes audio to a WAV file
.
980 Backend specific options are
:
983 Write recorded audio into the specified file
. Default is
987 DEF("device", HAS_ARG
, QEMU_OPTION_device
,
988 "-device driver[,prop[=value][,...]]\n"
989 " add device (based on driver)\n"
990 " prop=value,... sets driver properties\n"
991 " use '-device help' to print all possible drivers\n"
992 " use '-device driver,help' to print all possible properties\n",
995 ``
-device driver
[,prop
[=value
][,...]]``
996 Add device driver
. prop
=value sets driver properties
. Valid
997 properties depend on the driver
. To get help on possible drivers and
998 properties
, use ``
-device help`` and ``
-device driver
,help``
.
1002 ``
-device ipmi
-bmc
-sim
,id
=id
[,prop
[=value
][,...]]``
1003 Add an IPMI BMC
. This is a simulation of a hardware management
1004 interface processor that normally sits on a system
. It provides a
1005 watchdog and the ability to reset and power control the system
. You
1006 need to connect
this to an IPMI
interface to make it useful
1008 The IPMI slave address to use
for the BMC
. The
default is
0x20. This
1009 address is the BMC
's address on the I2C network of management
1010 controllers. If you don't know what
this means
, it is safe to ignore
1014 The BMC id
for interfaces to use
this device
.
1017 Define slave address to use
for the BMC
. The
default is
0x20.
1020 file containing raw Sensor Data
Records (SDR
) data
. The
default
1024 size of a Field Replaceable
Unit (FRU
) area
. The
default is
1027 ``frudatafile
=file``
1028 file containing raw Field Replaceable
Unit (FRU
) inventory data
.
1029 The
default is none
.
1032 value
for the GUID
for the BMC
, in standard UUID format
. If
this
1033 is set
, get
"Get GUID" command to the BMC will
return it
.
1034 Otherwise
"Get GUID" will
return an error
.
1036 ``
-device ipmi
-bmc
-extern,id
=id
,chardev
=id
[,slave_addr
=val
]``
1037 Add a connection to an external IPMI BMC simulator
. Instead of
1038 locally emulating the BMC like the above item
, instead connect to an
1039 external entity that provides the IPMI services
.
1041 A connection is made to an external BMC simulator
. If you
do this,
1042 it is strongly recommended that you use the
"reconnect=" chardev
1043 option to reconnect to the simulator
if the connection is lost
. Note
1044 that
if this is not used carefully
, it can be a security issue
, as
1045 the
interface has the ability to send resets
, NMIs
, and power off
1046 the VM
. It
's best if QEMU makes a connection to an external
1047 simulator running on a secure port on localhost, so neither the
1048 simulator nor QEMU is exposed to any outside network.
1050 See the "lanserv/README.vm" file in the OpenIPMI library for more
1051 details on the external interface.
1053 ``-device isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val]``
1054 Add a KCS IPMI interafce on the ISA bus. This also adds a
1055 corresponding ACPI and SMBIOS entries, if appropriate.
1058 The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern
1062 Define the I/O address of the interface. The default is 0xca0
1066 Define the interrupt to use. The default is 5. To disable
1067 interrupts, set this to 0.
1069 ``-device isa-ipmi-bt,bmc=id[,ioport=val][,irq=val]``
1070 Like the KCS interface, but defines a BT interface. The default port
1071 is 0xe4 and the default interrupt is 5.
1073 ``-device pci-ipmi-kcs,bmc=id``
1074 Add a KCS IPMI interafce on the PCI bus.
1077 The BMC to connect to, one of ipmi-bmc-sim or ipmi-bmc-extern above.
1079 ``-device pci-ipmi-bt,bmc=id``
1080 Like the KCS interface, but defines a BT interface on the PCI bus.
1082 ``-device intel-iommu[,option=...]``
1083 This is only supported by ``-machine q35``, which will enable Intel VT-d
1084 emulation within the guest. It supports below options:
1086 ``intremap=on|off`` (default: auto)
1087 This enables interrupt remapping feature. It's required to enable
1088 complete x2apic
. Currently it only supports kvm kernel
-irqchip modes
1089 ``off`` or ``split``
, while full kernel
-irqchip is not yet supported
.
1090 The
default value is
"auto", which will be decided by the mode of
1093 ``caching
-mode
=on|off``
(default: off
)
1094 This enables caching mode
for the VT
-d emulated device
. When
1095 caching
-mode is enabled
, each guest DMA buffer mapping will generate an
1096 IOTLB invalidation from the guest IOMMU driver to the vIOMMU device
in
1097 a synchronous way
. It is required
for ``
-device vfio
-pci`` to work
1098 with the VT
-d device
, because host assigned devices requires to setup
1099 the DMA mapping on the host before guest DMA starts
.
1101 ``device
-iotlb
=on|off``
(default: off
)
1102 This enables device
-iotlb capability
for the emulated VT
-d device
. So
1103 far virtio
/vhost should be the only real user
for this parameter
,
1104 paired with ats
=on configured
for the device
.
1106 ``aw
-bits
=39|
48``
(default: 39)
1107 This decides the address width of IOVA address space
. The address
1108 space has
39 bits width
for 3-level IOMMU page tables
, and
48 bits
for
1109 4-level IOMMU page tables
.
1111 Please also refer to the wiki page
for general scenarios of VT
-d
1112 emulation
in QEMU
: https
://wiki.qemu.org/Features/VT-d.
1116 DEF("name", HAS_ARG
, QEMU_OPTION_name
,
1117 "-name string1[,process=string2][,debug-threads=on|off]\n"
1118 " set the name of the guest\n"
1119 " string1 sets the window title and string2 the process name\n"
1120 " When debug-threads is enabled, individual threads are given a separate name\n"
1121 " NOTE: The thread names are for debugging and not a stable API.\n",
1125 Sets the name of the guest
. This name will be displayed
in the SDL
1126 window caption
. The name will also be used
for the VNC server
. Also
1127 optionally set the top visible process name
in Linux
. Naming of
1128 individual threads can also be enabled on Linux to aid debugging
.
1131 DEF("uuid", HAS_ARG
, QEMU_OPTION_uuid
,
1132 "-uuid %08x-%04x-%04x-%04x-%012x\n"
1133 " specify machine UUID\n", QEMU_ARCH_ALL
)
1141 DEFHEADING(Block device options
:)
1144 The QEMU block device handling options have a long history and
1145 have gone through several iterations as the feature set and complexity
1146 of the block layer have grown
. Many online guides to QEMU often
1147 reference older and deprecated options
, which can lead to confusion
.
1149 The recommended modern way to describe disks is to use a combination of
1150 ``
-device`` to specify the hardware device and ``
-blockdev`` to
1151 describe the backend
. The device defines what the guest sees and the
1152 backend describes how QEMU handles the data
.
1156 DEF("fda", HAS_ARG
, QEMU_OPTION_fda
,
1157 "-fda/-fdb file use 'file' as floppy disk 0/1 image\n", QEMU_ARCH_ALL
)
1158 DEF("fdb", HAS_ARG
, QEMU_OPTION_fdb
, "", QEMU_ARCH_ALL
)
1163 Use file as floppy disk
0/1 image (see the
:ref
:`disk images` chapter
in
1164 the System Emulation Users Guide
).
1167 DEF("hda", HAS_ARG
, QEMU_OPTION_hda
,
1168 "-hda/-hdb file use 'file' as IDE hard disk 0/1 image\n", QEMU_ARCH_ALL
)
1169 DEF("hdb", HAS_ARG
, QEMU_OPTION_hdb
, "", QEMU_ARCH_ALL
)
1170 DEF("hdc", HAS_ARG
, QEMU_OPTION_hdc
,
1171 "-hdc/-hdd file use 'file' as IDE hard disk 2/3 image\n", QEMU_ARCH_ALL
)
1172 DEF("hdd", HAS_ARG
, QEMU_OPTION_hdd
, "", QEMU_ARCH_ALL
)
1181 Use file as hard disk
0, 1, 2 or
3 image (see the
:ref
:`disk images`
1182 chapter
in the System Emulation Users Guide
).
1185 DEF("cdrom", HAS_ARG
, QEMU_OPTION_cdrom
,
1186 "-cdrom file use 'file' as IDE cdrom image (cdrom is ide1 master)\n",
1190 Use file as CD
-ROM
image (you cannot use ``
-hdc`` and ``
-cdrom`` at
1191 the same time
). You can use the host CD
-ROM by
using ``
/dev
/cdrom``
1195 DEF("blockdev", HAS_ARG
, QEMU_OPTION_blockdev
,
1196 "-blockdev [driver=]driver[,node-name=N][,discard=ignore|unmap]\n"
1197 " [,cache.direct=on|off][,cache.no-flush=on|off]\n"
1198 " [,read-only=on|off][,auto-read-only=on|off]\n"
1199 " [,force-share=on|off][,detect-zeroes=on|off|unmap]\n"
1200 " [,driver specific parameters...]\n"
1201 " configure a block backend\n", QEMU_ARCH_ALL
)
1203 ``
-blockdev option
[,option
[,option
[,...]]]``
1204 Define a
new block driver node
. Some of the options apply to all
1205 block drivers
, other options are only accepted
for a specific block
1206 driver
. See below
for a list of generic options and options
for the
1207 most common block drivers
.
1209 Options that expect a reference to another
node (e
.g
. ``file``
) can
1210 be given
in two ways
. Either you specify the node name of an already
1211 existing
node (file
=node
-name
), or you define a
new node
inline,
1212 adding options
for the referenced node after a dot
1213 (file
.filename
=path
,file
.aio
=native
).
1215 A block driver node created with ``
-blockdev`` can be used
for a
1216 guest device by specifying its node name
for the ``drive`` property
1217 in a ``
-device`` argument that defines a block device
.
1219 ``Valid options
for any block driver node
:``
1221 Specifies the block driver to use
for the given node
.
1224 This defines the name of the block driver node by which it
1225 will be referenced later
. The name must be unique
, i
.e
. it
1226 must not match the name of a different block driver node
, or
1227 (if you use ``
-drive`` as well
) the ID of a drive
.
1229 If no node name is specified
, it is automatically generated
.
1230 The generated node name is not intended to be predictable
1231 and changes between QEMU invocations
. For the top level
, an
1232 explicit node name must be specified
.
1235 Open the node read
-only
. Guest write attempts will fail
.
1237 Note that some block drivers support only read
-only access
,
1238 either generally or
in certain configurations
. In
this case,
1239 the
default value ``read
-only
=off`` does not work and the
1240 option must be specified explicitly
.
1243 If ``auto
-read
-only
=on`` is set
, QEMU may fall back to
1244 read
-only usage even when ``read
-only
=off`` is requested
, or
1245 even
switch between modes as needed
, e
.g
. depending on
1246 whether the image file is writable or whether a writing user
1247 is attached to the node
.
1250 Override the image locking system of QEMU by forcing the
1251 node to utilize weaker shared access
for permissions where
1252 it would normally request exclusive access
. When there is
1253 the potential
for multiple instances to have the same file
1254 open (whether
this invocation of QEMU is the first or the
1255 second instance
), both instances must permit shared access
1256 for the second instance to succeed at opening the file
.
1258 Enabling ``force
-share
=on`` requires ``read
-only
=on``
.
1261 The host page cache can be avoided with ``cache
.direct
=on``
.
1262 This will attempt to
do disk IO directly to the guest
's
1263 memory. QEMU may still perform an internal copy of the data.
1266 In case you don't care about data integrity over host
1267 failures
, you can use ``cache
.no
-flush
=on``
. This option
1268 tells QEMU that it
never needs to write any data to the disk
1269 but can instead keep things
in cache
. If anything goes
1270 wrong
, like your host losing power
, the disk storage getting
1271 disconnected accidentally
, etc
. your image will most
1272 probably be rendered unusable
.
1275 discard is one of
"ignore" (or
"off") or
"unmap" (or
"on")
1276 and controls whether ``discard``
(also known as ``trim`` or
1277 ``unmap``
) requests are ignored or passed to the filesystem
.
1278 Some machine types may not support discard requests
.
1280 ``detect
-zeroes
=detect
-zeroes``
1281 detect
-zeroes is
"off", "on" or
"unmap" and enables the
1282 automatic conversion of plain zero writes by the OS to
1283 driver specific optimized zero write commands
. You may even
1284 choose
"unmap" if discard is set to
"unmap" to allow a zero
1285 write to be converted to an ``unmap`` operation
.
1287 ``Driver
-specific options
for file``
1288 This is the protocol
-level block driver
for accessing regular
1292 The path to the image file
in the local filesystem
1295 Specifies the AIO
backend (threads
/native
/io_uring
,
1299 Specifies whether the image file is protected with Linux OFD
1300 / POSIX locks
. The
default is to use the Linux Open File
1301 Descriptor API
if available
, otherwise no lock is applied
.
1302 (auto
/on
/off
, default: auto
)
1308 -blockdev driver
=file
,node
-name
=disk
,filename
=disk
.img
1310 ``Driver
-specific options
for raw``
1311 This is the image format block driver
for raw images
. It is
1312 usually stacked on top of a protocol level block driver such as
1316 Reference to or definition of the data source block driver
1317 node (e
.g
. a ``file`` driver node
)
1323 -blockdev driver
=file
,node
-name
=disk_file
,filename
=disk
.img
1324 -blockdev driver
=raw
,node
-name
=disk
,file
=disk_file
1330 -blockdev driver
=raw
,node
-name
=disk
,file
.driver
=file
,file
.filename
=disk
.img
1332 ``Driver
-specific options
for qcow2``
1333 This is the image format block driver
for qcow2 images
. It is
1334 usually stacked on top of a protocol level block driver such as
1338 Reference to or definition of the data source block driver
1339 node (e
.g
. a ``file`` driver node
)
1342 Reference to or definition of the backing file block device
1343 (default is taken from the image file
). It is allowed to
1344 pass ``
null``
here in order to disable the
default backing
1348 Whether to enable the lazy refcounts
feature (on
/off
;
1349 default is taken from the image file
)
1352 The maximum total size of the L2 table and refcount block
1353 caches
in bytes (default: the sum of l2
-cache
-size and
1354 refcount
-cache
-size
)
1357 The maximum size of the L2 table cache
in bytes (default: if
1358 cache
-size is not specified
- 32M on Linux platforms
, and
8M
1359 on non
-Linux platforms
; otherwise
, as large as possible
1360 within the cache
-size
, while permitting the requested or the
1361 minimal refcount cache size
)
1363 ``refcount
-cache
-size``
1364 The maximum size of the refcount block cache
in bytes
1365 (default: 4 times the cluster size
; or
if cache
-size is
1366 specified
, the part of it which is not used
for the L2
1369 ``cache
-clean
-interval``
1370 Clean unused entries
in the L2 and refcount caches
. The
1371 interval is
in seconds
. The
default value is
600 on
1372 supporting platforms
, and
0 on other platforms
. Setting it
1373 to
0 disables
this feature
.
1375 ``pass
-discard
-request``
1376 Whether discard requests to the qcow2 device should be
1377 forwarded to the data
source (on
/off
; default: on
if
1378 discard
=unmap is specified
, off otherwise
)
1380 ``pass
-discard
-snapshot``
1381 Whether discard requests
for the data source should be
1382 issued when a snapshot
operation (e
.g
. deleting a snapshot
)
1383 frees clusters
in the qcow2
file (on
/off
; default: on
)
1385 ``pass
-discard
-other``
1386 Whether discard requests
for the data source should be
1387 issued on other occasions where a cluster gets freed
1388 (on
/off
; default: off
)
1391 Which overlap checks to perform
for writes to the image
1392 (none
/constant
/cached
/all
; default: cached
). For details or
1393 finer granularity control refer to the QAPI documentation of
1400 -blockdev driver
=file
,node
-name
=my_file
,filename
=/tmp
/disk
.qcow2
1401 -blockdev driver
=qcow2
,node
-name
=hda
,file
=my_file
,overlap
-check
=none
,cache
-size
=16777216
1407 -blockdev driver
=qcow2
,node
-name
=disk
,file
.driver
=http
,file
.filename
=http
://example.com/image.qcow2
1409 ``Driver
-specific options
for other drivers``
1410 Please refer to the QAPI documentation of the ``blockdev
-add``
1414 DEF("drive", HAS_ARG
, QEMU_OPTION_drive
,
1415 "-drive [file=file][,if=type][,bus=n][,unit=m][,media=d][,index=i]\n"
1416 " [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n"
1417 " [,snapshot=on|off][,rerror=ignore|stop|report]\n"
1418 " [,werror=ignore|stop|report|enospc][,id=name]\n"
1419 " [,aio=threads|native|io_uring]\n"
1420 " [,readonly=on|off][,copy-on-read=on|off]\n"
1421 " [,discard=ignore|unmap][,detect-zeroes=on|off|unmap]\n"
1422 " [[,bps=b]|[[,bps_rd=r][,bps_wr=w]]]\n"
1423 " [[,iops=i]|[[,iops_rd=r][,iops_wr=w]]]\n"
1424 " [[,bps_max=bm]|[[,bps_rd_max=rm][,bps_wr_max=wm]]]\n"
1425 " [[,iops_max=im]|[[,iops_rd_max=irm][,iops_wr_max=iwm]]]\n"
1426 " [[,iops_size=is]]\n"
1428 " use 'file' as a drive image\n", QEMU_ARCH_ALL
)
1430 ``
-drive option
[,option
[,option
[,...]]]``
1431 Define a
new drive
. This includes creating a block driver
node (the
1432 backend
) as well as a guest device
, and is mostly a shortcut
for
1433 defining the corresponding ``
-blockdev`` and ``
-device`` options
.
1435 ``
-drive`` accepts all options that are accepted by ``
-blockdev``
.
1436 In addition
, it knows the following options
:
1439 This option defines which disk
image (see the
:ref
:`disk images`
1440 chapter
in the System Emulation Users Guide
) to use with
this drive
.
1441 If the filename contains comma
, you must double
it (for instance
,
1442 "file=my,,file" to use file
"my,file").
1444 Special files such as iSCSI devices can be specified
using
1445 protocol specific URLs
. See the section
for "Device URL Syntax"
1446 for more information
.
1449 This option defines on which type on
interface the drive is
1450 connected
. Available types are
: ide
, scsi
, sd
, mtd
, floppy
,
1451 pflash
, virtio
, none
.
1453 ``bus
=bus
,unit
=unit``
1454 These options define where is connected the drive by defining
1455 the bus number and the unit id
.
1458 This option defines where the drive is connected by
using an
1459 index
in the list of available connectors of a given
interface
1463 This option defines the type of the media
: disk or cdrom
.
1465 ``snapshot
=snapshot``
1466 snapshot is
"on" or
"off" and controls snapshot mode
for the
1467 given
drive (see ``
-snapshot``
).
1470 cache is
"none", "writeback", "unsafe", "directsync" or
1471 "writethrough" and controls how the host cache is used to access
1472 block data
. This is a shortcut that sets the ``cache
.direct``
1473 and ``cache
.no
-flush``
options (as
in ``
-blockdev``
), and
1474 additionally ``cache
.writeback``
, which provides a
default for
1475 the ``write
-cache`` option of block guest
devices (as
in
1476 ``
-device``
). The modes correspond to the following settings
:
1478 ============= =============== ============ ==============
1479 \ cache
.writeback cache
.direct cache
.no
-flush
1480 ============= =============== ============ ==============
1481 writeback on off off
1483 writethrough off off off
1484 directsync off on off
1486 ============= =============== ============ ==============
1488 The
default mode is ``cache
=writeback``
.
1491 aio is
"threads", "native", or
"io_uring" and selects between pthread
1492 based disk I
/O
, native Linux AIO
, or Linux io_uring API
.
1495 Specify which disk format will be used rather than detecting the
1496 format
. Can be used to specify format
=raw to avoid interpreting
1497 an untrusted format header
.
1499 ``werror
=action
,rerror
=action``
1500 Specify which action to take on write and read errors
. Valid
1501 actions are
: "ignore" (ignore the error and
try to
continue),
1502 "stop" (pause QEMU
), "report" (report the error to the guest
),
1503 "enospc" (pause QEMU only
if the host disk is full
; report the
1504 error to the guest otherwise
). The
default setting is
1505 ``werror
=enospc`` and ``rerror
=report``
.
1507 ``copy
-on
-read
=copy
-on
-read``
1508 copy
-on
-read is
"on" or
"off" and enables whether to copy read
1509 backing file sectors into the image file
.
1511 ``bps
=b
,bps_rd
=r
,bps_wr
=w``
1512 Specify bandwidth throttling limits
in bytes per second
, either
1513 for all request types or
for reads or writes only
. Small values
1514 can lead to timeouts or hangs inside the guest
. A safe minimum
1515 for disks is
2 MB
/s
.
1517 ``bps_max
=bm
,bps_rd_max
=rm
,bps_wr_max
=wm``
1518 Specify bursts
in bytes per second
, either
for all request types
1519 or
for reads or writes only
. Bursts allow the guest I
/O to spike
1520 above the limit temporarily
.
1522 ``iops
=i
,iops_rd
=r
,iops_wr
=w``
1523 Specify request rate limits
in requests per second
, either
for
1524 all request types or
for reads or writes only
.
1526 ``iops_max
=bm
,iops_rd_max
=rm
,iops_wr_max
=wm``
1527 Specify bursts
in requests per second
, either
for all request
1528 types or
for reads or writes only
. Bursts allow the guest I
/O to
1529 spike above the limit temporarily
.
1532 Let every is bytes of a request count as a
new request
for iops
1533 throttling purposes
. Use
this option to prevent guests from
1534 circumventing iops limits by sending fewer but larger requests
.
1537 Join a throttling quota group with given name g
. All drives that
1538 are members of the same group are accounted
for together
. Use
1539 this option to prevent guests from circumventing throttling
1540 limits by
using many small disks instead of a single larger
1543 By
default, the ``cache
.writeback
=on`` mode is used
. It will report
1544 data writes as completed as soon as the data is present
in the host
1545 page cache
. This is safe as long as your guest OS makes sure to
1546 correctly flush disk caches where needed
. If your guest OS does not
1547 handle volatile disk write caches correctly and your host crashes or
1548 loses power
, then the guest may experience data corruption
.
1550 For such guests
, you should consider
using ``cache
.writeback
=off``
.
1551 This means that the host page cache will be used to read and write
1552 data
, but write notification will be sent to the guest only after
1553 QEMU has made sure to flush each write to the disk
. Be aware that
1554 this has a major impact on performance
.
1556 When
using the ``
-snapshot`` option
, unsafe caching is always used
.
1558 Copy
-on
-read avoids accessing the same backing file sectors
1559 repeatedly and is useful when the backing file is over a slow
1560 network
. By
default copy
-on
-read is off
.
1562 Instead of ``
-cdrom`` you can use
:
1566 |qemu_system|
-drive file
=file
,index
=2,media
=cdrom
1568 Instead of ``
-hda``
, ``
-hdb``
, ``
-hdc``
, ``
-hdd``
, you can use
:
1572 |qemu_system|
-drive file
=file
,index
=0,media
=disk
1573 |qemu_system|
-drive file
=file
,index
=1,media
=disk
1574 |qemu_system|
-drive file
=file
,index
=2,media
=disk
1575 |qemu_system|
-drive file
=file
,index
=3,media
=disk
1577 You can open an image
using pre
-opened file descriptors from an fd
1583 -add
-fd fd
=3,set
=2,opaque
="rdwr:/path/to/file" \\
1584 -add
-fd fd
=4,set
=2,opaque
="rdonly:/path/to/file" \\
1585 -drive file
=/dev
/fdset
/2,index
=0,media
=disk
1587 You can connect a CDROM to the slave of ide0
:
1591 |qemu_system_x86|
-drive file
=file
,if=ide
,index
=1,media
=cdrom
1593 If you don
't specify the "file=" argument, you define an empty
1598 |qemu_system_x86| -drive if=ide,index=1,media=cdrom
1600 Instead of ``-fda``, ``-fdb``, you can use:
1604 |qemu_system_x86| -drive file=file,index=0,if=floppy
1605 |qemu_system_x86| -drive file=file,index=1,if=floppy
1607 By default, interface is "ide" and index is automatically
1612 |qemu_system_x86| -drive file=a -drive file=b"
1614 is interpreted like:
1618 |qemu_system_x86| -hda a -hdb b
1621 DEF("mtdblock", HAS_ARG, QEMU_OPTION_mtdblock,
1622 "-mtdblock file use 'file
' as on-board Flash memory image\n",
1626 Use file as on-board Flash memory image.
1629 DEF("sd", HAS_ARG, QEMU_OPTION_sd,
1630 "-sd file use 'file
' as SecureDigital card image\n", QEMU_ARCH_ALL)
1633 Use file as SecureDigital card image.
1636 DEF("snapshot", 0, QEMU_OPTION_snapshot,
1637 "-snapshot write to temporary files instead of disk image files\n",
1641 Write to temporary files instead of disk image files. In this case,
1642 the raw disk image you use is not written back. You can however
1643 force the write back by pressing C-a s (see the :ref:`disk images`
1644 chapter in the System Emulation Users Guide).
1647 DEF("fsdev", HAS_ARG, QEMU_OPTION_fsdev,
1648 "-fsdev local,id=id,path=path,security_model=mapped-xattr|mapped-file|passthrough|none\n"
1649 " [,writeout=immediate][,readonly=on][,fmode=fmode][,dmode=dmode]\n"
1650 " [[,throttling.bps-total=b]|[[,throttling.bps-read=r][,throttling.bps-write=w]]]\n"
1651 " [[,throttling.iops-total=i]|[[,throttling.iops-read=r][,throttling.iops-write=w]]]\n"
1652 " [[,throttling.bps-total-max=bm]|[[,throttling.bps-read-max=rm][,throttling.bps-write-max=wm]]]\n"
1653 " [[,throttling.iops-total-max=im]|[[,throttling.iops-read-max=irm][,throttling.iops-write-max=iwm]]]\n"
1654 " [[,throttling.iops-size=is]]\n"
1655 "-fsdev proxy,id=id,socket=socket[,writeout=immediate][,readonly=on]\n"
1656 "-fsdev proxy,id=id,sock_fd=sock_fd[,writeout=immediate][,readonly=on]\n"
1657 "-fsdev synth,id=id\n",
1661 ``-fsdev local,id=id,path=path,security_model=security_model [,writeout=writeout][,readonly=on][,fmode=fmode][,dmode=dmode] [,throttling.option=value[,throttling.option=value[,...]]]``
1663 ``-fsdev proxy,id=id,socket=socket[,writeout=writeout][,readonly=on]``
1665 ``-fsdev proxy,id=id,sock_fd=sock_fd[,writeout=writeout][,readonly=on]``
1667 ``-fsdev synth,id=id[,readonly=on]``
1668 Define a new file system device. Valid options are:
1671 Accesses to the filesystem are done by QEMU.
1674 Accesses to the filesystem are done by virtfs-proxy-helper(1).
1677 Synthetic filesystem, only used by QTests.
1680 Specifies identifier for this device.
1683 Specifies the export path for the file system device. Files
1684 under this path will be available to the 9p client on the guest.
1686 ``security_model=security_model``
1687 Specifies the security model to be used for this export path.
1688 Supported security models are "passthrough", "mapped-xattr",
1689 "mapped-file" and "none". In "passthrough" security model, files
1690 are stored using the same credentials as they are created on the
1691 guest. This requires QEMU to run as root. In "mapped-xattr"
1692 security model, some of the file attributes like uid, gid, mode
1693 bits and link target are stored as file attributes. For
1694 "mapped-file" these attributes are stored in the hidden
1695 .virtfs\_metadata directory. Directories exported by this
1696 security model cannot interact with other unix tools. "none"
1697 security model is same as passthrough except the sever won't
1698 report failures
if it fails to set file attributes like
1699 ownership
. Security model is mandatory only
for local fsdriver
.
1700 Other
fsdrivers (like proxy
) don
't take security model as a
1703 ``writeout=writeout``
1704 This is an optional argument. The only supported value is
1705 "immediate". This means that host page cache will be used to
1706 read and write data but write notification will be sent to the
1707 guest only when the data has been reported as written by the
1711 Enables exporting 9p share as a readonly mount for guests. By
1712 default read-write access is given.
1715 Enables proxy filesystem driver to use passed socket file for
1716 communicating with virtfs-proxy-helper(1).
1719 Enables proxy filesystem driver to use passed socket descriptor
1720 for communicating with virtfs-proxy-helper(1). Usually a helper
1721 like libvirt will create socketpair and pass one of the fds as
1725 Specifies the default mode for newly created files on the host.
1726 Works only with security models "mapped-xattr" and
1730 Specifies the default mode for newly created directories on the
1731 host. Works only with security models "mapped-xattr" and
1734 ``throttling.bps-total=b,throttling.bps-read=r,throttling.bps-write=w``
1735 Specify bandwidth throttling limits in bytes per second, either
1736 for all request types or for reads or writes only.
1738 ``throttling.bps-total-max=bm,bps-read-max=rm,bps-write-max=wm``
1739 Specify bursts in bytes per second, either for all request types
1740 or for reads or writes only. Bursts allow the guest I/O to spike
1741 above the limit temporarily.
1743 ``throttling.iops-total=i,throttling.iops-read=r, throttling.iops-write=w``
1744 Specify request rate limits in requests per second, either for
1745 all request types or for reads or writes only.
1747 ``throttling.iops-total-max=im,throttling.iops-read-max=irm, throttling.iops-write-max=iwm``
1748 Specify bursts in requests per second, either for all request
1749 types or for reads or writes only. Bursts allow the guest I/O to
1750 spike above the limit temporarily.
1752 ``throttling.iops-size=is``
1753 Let every is bytes of a request count as a new request for iops
1754 throttling purposes.
1756 -fsdev option is used along with -device driver "virtio-9p-...".
1758 ``-device virtio-9p-type,fsdev=id,mount_tag=mount_tag``
1759 Options for virtio-9p-... driver are:
1762 Specifies the variant to be used. Supported values are "pci",
1763 "ccw" or "device", depending on the machine type.
1766 Specifies the id value specified along with -fsdev option.
1768 ``mount_tag=mount_tag``
1769 Specifies the tag name to be used by the guest to mount this
1773 DEF("virtfs", HAS_ARG, QEMU_OPTION_virtfs,
1774 "-virtfs local,path=path,mount_tag=tag,security_model=mapped-xattr|mapped-file|passthrough|none\n"
1775 " [,id=id][,writeout=immediate][,readonly=on][,fmode=fmode][,dmode=dmode][,multidevs=remap|forbid|warn]\n"
1776 "-virtfs proxy,mount_tag=tag,socket=socket[,id=id][,writeout=immediate][,readonly=on]\n"
1777 "-virtfs proxy,mount_tag=tag,sock_fd=sock_fd[,id=id][,writeout=immediate][,readonly=on]\n"
1778 "-virtfs synth,mount_tag=tag[,id=id][,readonly=on]\n",
1782 ``-virtfs local,path=path,mount_tag=mount_tag ,security_model=security_model[,writeout=writeout][,readonly=on] [,fmode=fmode][,dmode=dmode][,multidevs=multidevs]``
1784 ``-virtfs proxy,socket=socket,mount_tag=mount_tag [,writeout=writeout][,readonly=on]``
1786 ``-virtfs proxy,sock_fd=sock_fd,mount_tag=mount_tag [,writeout=writeout][,readonly=on]``
1788 ``-virtfs synth,mount_tag=mount_tag``
1789 Define a new virtual filesystem device and expose it to the guest using
1790 a virtio-9p-device (a.k.a. 9pfs), which essentially means that a certain
1791 directory on host is made directly accessible by guest as a pass-through
1792 file system by using the 9P network protocol for communication between
1793 host and guests, if desired even accessible, shared by several guests
1796 Note that ``-virtfs`` is actually just a convenience shortcut for its
1797 generalized form ``-fsdev -device virtio-9p-pci``.
1799 The general form of pass-through file system options are:
1802 Accesses to the filesystem are done by QEMU.
1805 Accesses to the filesystem are done by virtfs-proxy-helper(1).
1808 Synthetic filesystem, only used by QTests.
1811 Specifies identifier for the filesystem device
1814 Specifies the export path for the file system device. Files
1815 under this path will be available to the 9p client on the guest.
1817 ``security_model=security_model``
1818 Specifies the security model to be used for this export path.
1819 Supported security models are "passthrough", "mapped-xattr",
1820 "mapped-file" and "none". In "passthrough" security model, files
1821 are stored using the same credentials as they are created on the
1822 guest. This requires QEMU to run as root. In "mapped-xattr"
1823 security model, some of the file attributes like uid, gid, mode
1824 bits and link target are stored as file attributes. For
1825 "mapped-file" these attributes are stored in the hidden
1826 .virtfs\_metadata directory. Directories exported by this
1827 security model cannot interact with other unix tools. "none"
1828 security model is same as passthrough except the sever won't
1829 report failures
if it fails to set file attributes like
1830 ownership
. Security model is mandatory only
for local fsdriver
.
1831 Other
fsdrivers (like proxy
) don
't take security model as a
1834 ``writeout=writeout``
1835 This is an optional argument. The only supported value is
1836 "immediate". This means that host page cache will be used to
1837 read and write data but write notification will be sent to the
1838 guest only when the data has been reported as written by the
1842 Enables exporting 9p share as a readonly mount for guests. By
1843 default read-write access is given.
1846 Enables proxy filesystem driver to use passed socket file for
1847 communicating with virtfs-proxy-helper(1). Usually a helper like
1848 libvirt will create socketpair and pass one of the fds as
1852 Enables proxy filesystem driver to use passed 'sock\_fd
' as the
1853 socket descriptor for interfacing with virtfs-proxy-helper(1).
1856 Specifies the default mode for newly created files on the host.
1857 Works only with security models "mapped-xattr" and
1861 Specifies the default mode for newly created directories on the
1862 host. Works only with security models "mapped-xattr" and
1865 ``mount_tag=mount_tag``
1866 Specifies the tag name to be used by the guest to mount this
1869 ``multidevs=multidevs``
1870 Specifies how to deal with multiple devices being shared with a
1871 9p export. Supported behaviours are either "remap", "forbid" or
1872 "warn". The latter is the default behaviour on which virtfs 9p
1873 expects only one device to be shared with the same export, and
1874 if more than one device is shared and accessed via the same 9p
1875 export then only a warning message is logged (once) by qemu on
1876 host side. In order to avoid file ID collisions on guest you
1877 should either create a separate virtfs export for each device to
1878 be shared with guests (recommended way) or you might use "remap"
1879 instead which allows you to share multiple devices with only one
1880 export instead, which is achieved by remapping the original
1881 inode numbers from host to guest in a way that would prevent
1882 such collisions. Remapping inodes in such use cases is required
1883 because the original device IDs from host are never passed and
1884 exposed on guest. Instead all files of an export shared with
1885 virtfs always share the same device id on guest. So two files
1886 with identical inode numbers but from actually different devices
1887 on host would otherwise cause a file ID collision and hence
1888 potential misbehaviours on guest. "forbid" on the other hand
1889 assumes like "warn" that only one device is shared by the same
1890 export, however it will not only log a warning message but also
1891 deny access to additional devices on guest. Note though that
1892 "forbid" does currently not block all possible file access
1893 operations (e.g. readdir() would still return entries from other
1897 DEF("iscsi", HAS_ARG, QEMU_OPTION_iscsi,
1898 "-iscsi [user=user][,password=password]\n"
1899 " [,header-digest=CRC32C|CR32C-NONE|NONE-CRC32C|NONE\n"
1900 " [,initiator-name=initiator-iqn][,id=target-iqn]\n"
1901 " [,timeout=timeout]\n"
1902 " iSCSI session parameters\n", QEMU_ARCH_ALL)
1906 Configure iSCSI session parameters.
1911 DEFHEADING(USB convenience options:)
1913 DEF("usb", 0, QEMU_OPTION_usb,
1914 "-usb enable on-board USB host controller (if not enabled by default)\n",
1918 Enable USB emulation on machine types with an on-board USB host
1919 controller (if not enabled by default). Note that on-board USB host
1920 controllers may not support USB 3.0. In this case
1921 ``-device qemu-xhci`` can be used instead on machines with PCI.
1924 DEF("usbdevice", HAS_ARG, QEMU_OPTION_usbdevice,
1925 "-usbdevice name add the host or guest USB device 'name
'\n",
1928 ``-usbdevice devname``
1929 Add the USB device devname, and enable an on-board USB controller
1930 if possible and necessary (just like it can be done via
1931 ``-machine usb=on``). Note that this option is mainly intended for
1932 the user's convenience only
. More fine
-grained control can be
1933 achieved by selecting a USB host
controller (if necessary
) and the
1934 desired USB device via the ``
-device`` option instead
. For example
,
1935 instead of
using ``
-usbdevice mouse`` it is possible to use
1936 ``
-device qemu
-xhci
-device usb
-mouse`` to connect the USB mouse
1937 to a USB
3.0 controller
instead (at least on machines that support
1938 PCI and
do not have an USB controller enabled by
default yet
).
1939 For more details
, see the chapter about
1940 :ref
:`Connecting USB devices`
in the System Emulation Users Guide
.
1941 Possible devices
for devname are
:
1944 Braille device
. This will use BrlAPI to display the braille
1945 output on a real or fake
device (i
.e
. it also creates a
1946 corresponding ``braille`` chardev automatically beside the
1947 ``usb
-braille`` USB device
).
1950 Standard USB keyboard
. Will
override the PS
/2 keyboard (if present
).
1953 Virtual Mouse
. This will
override the PS
/2 mouse emulation when
1957 Pointer device that uses absolute
coordinates (like a
1958 touchscreen
). This means QEMU is able to report the mouse
1959 position without having to grab the mouse
. Also overrides the
1960 PS
/2 mouse emulation when activated
.
1963 Wacom PenPartner USB tablet
.
1970 DEFHEADING(Display options
:)
1972 DEF("display", HAS_ARG
, QEMU_OPTION_display
,
1973 #
if defined(CONFIG_SPICE
)
1974 "-display spice-app[,gl=on|off]\n"
1976 #
if defined(CONFIG_SDL
)
1977 "-display sdl[,gl=on|core|es|off][,grab-mod=<mod>][,show-cursor=on|off]\n"
1978 " [,window-close=on|off]\n"
1980 #
if defined(CONFIG_GTK
)
1981 "-display gtk[,full-screen=on|off][,gl=on|off][,grab-on-hover=on|off]\n"
1982 " [,show-tabs=on|off][,show-cursor=on|off][,window-close=on|off]\n"
1983 " [,show-menubar=on|off]\n"
1985 #
if defined(CONFIG_VNC
)
1986 "-display vnc=<display>[,<optargs>]\n"
1988 #
if defined(CONFIG_CURSES
)
1989 "-display curses[,charset=<encoding>]\n"
1991 #
if defined(CONFIG_COCOA
)
1992 "-display cocoa[,full-grab=on|off][,swap-opt-cmd=on|off]\n"
1994 #
if defined(CONFIG_OPENGL
)
1995 "-display egl-headless[,rendernode=<file>]\n"
1997 #
if defined(CONFIG_DBUS_DISPLAY
)
1998 "-display dbus[,addr=<dbusaddr>]\n"
1999 " [,gl=on|core|es|off][,rendernode=<file>]\n"
2001 #
if defined(CONFIG_COCOA
)
2002 "-display cocoa[,show-cursor=on|off][,left-command-key=on|off]\n"
2005 " select display backend type\n"
2006 " The default display is equivalent to\n "
2007 #
if defined(CONFIG_GTK
)
2008 "\"-display gtk\"\n"
2009 #elif
defined(CONFIG_SDL
)
2010 "\"-display sdl\"\n"
2011 #elif
defined(CONFIG_COCOA
)
2012 "\"-display cocoa\"\n"
2013 #elif
defined(CONFIG_VNC
)
2014 "\"-vnc localhost:0,to=99,id=default\"\n"
2016 "\"-display none\"\n"
2021 Select type of display to use
. Use ``
-display help`` to list the available
2022 display types
. Valid values
for type are
2024 ``spice
-app
[,gl
=on|off
]``
2025 Start QEMU as a Spice server and launch the
default Spice client
2026 application
. The Spice server will redirect the serial consoles
2027 and QEMU monitors
. (Since
4.0)
2030 Export the display over D
-Bus interfaces
. (Since
7.0)
2032 The connection is registered with the
"org.qemu" name (and queued when
2035 ``addr
=<dbusaddr
>``
: D
-Bus bus address to connect to
.
2037 ``p2p
=yes|no``
: Use peer
-to
-peer connection
, accepted via QMP ``add_client``
.
2039 ``gl
=on|off|core|es``
: Use OpenGL
for rendering (the D
-Bus
interface
2040 will share framebuffers with DMABUF file descriptors
).
2043 Display video output via
SDL (usually
in a separate graphics
2044 window
; see the SDL documentation
for other possibilities
).
2045 Valid parameters are
:
2047 ``grab
-mod
=<mods
>``
: Used to select the modifier keys
for toggling
2048 the mouse grabbing
in conjunction with the
"g" key
. ``
<mods
>`` can be
2049 either ``lshift
-lctrl
-lalt`` or ``rctrl``
.
2051 ``gl
=on|off|core|es``
: Use OpenGL
for displaying
2053 ``show
-cursor
=on|off``
: Force showing the mouse cursor
2055 ``window
-close
=on|off``
: Allow to quit qemu with window close button
2058 Display video output
in a GTK window
. This
interface provides
2059 drop
-down menus and other UI elements to configure and control
2060 the VM during runtime
. Valid parameters are
:
2062 ``full
-screen
=on|off``
: Start
in fullscreen mode
2064 ``gl
=on|off``
: Use OpenGL
for displaying
2066 ``grab
-on
-hover
=on|off``
: Grab keyboard input on mouse hover
2068 ``show
-tabs
=on|off``
: Display the tab bar
for switching between the
2069 various graphical
interfaces (e
.g
. VGA and
2070 virtual console character devices
) by
default.
2072 ``show
-cursor
=on|off``
: Force showing the mouse cursor
2074 ``window
-close
=on|off``
: Allow to quit qemu with window close button
2076 ``show
-menubar
=on|off``
: Display the main window menubar
, defaults to
"on"
2078 ``curses
[,charset
=<encoding
>]``
2079 Display video output via curses
. For graphics device models
2080 which support a text mode
, QEMU can display
this output
using a
2081 curses
/ncurses
interface. Nothing is displayed when the graphics
2082 device is
in graphical mode or
if the graphics device does not
2083 support a text mode
. Generally only the VGA device models
2084 support text mode
. The font charset used by the guest can be
2085 specified with the ``charset`` option
, for example
2086 ``charset
=CP850``
for IBM CP850 encoding
. The
default is
2090 Display video output
in a Cocoa window
. Mac only
. This
interface
2091 provides drop
-down menus and other UI elements to configure and
2092 control the VM during runtime
. Valid parameters are
:
2094 ``show
-cursor
=on|off``
: Force showing the mouse cursor
2096 ``left
-command
-key
=on|off``
: Disable forwarding left command key to host
2098 ``egl
-headless
[,rendernode
=<file
>]``
2099 Offload all OpenGL operations to a local DRI device
. For any
2100 graphical display
, this display needs to be paired with either
2101 VNC or SPICE displays
.
2104 Start a VNC server on display
<display
>
2107 Do not display video output
. The guest will still see an
2108 emulated graphics card
, but its output will not be displayed to
2109 the QEMU user
. This option differs from the
-nographic option
in
2110 that it only affects what is done with video output
; -nographic
2111 also changes the destination of the serial and parallel port
2115 DEF("nographic", 0, QEMU_OPTION_nographic
,
2116 "-nographic disable graphical output and redirect serial I/Os to console\n",
2120 Normally
, if QEMU is compiled with graphical window support
, it
2121 displays output such as guest graphics
, guest console
, and the QEMU
2122 monitor
in a window
. With
this option
, you can totally disable
2123 graphical output so that QEMU is a simple command line application
.
2124 The emulated serial port is redirected on the console and muxed with
2125 the
monitor (unless redirected elsewhere explicitly
). Therefore
, you
2126 can still use QEMU to debug a Linux kernel with a serial console
.
2127 Use C
-a h
for help on switching between the console and monitor
.
2131 DEF("spice", HAS_ARG
, QEMU_OPTION_spice
,
2132 "-spice [port=port][,tls-port=secured-port][,x509-dir=<dir>]\n"
2133 " [,x509-key-file=<file>][,x509-key-password=<file>]\n"
2134 " [,x509-cert-file=<file>][,x509-cacert-file=<file>]\n"
2135 " [,x509-dh-key-file=<file>][,addr=addr]\n"
2136 " [,ipv4=on|off][,ipv6=on|off][,unix=on|off]\n"
2137 " [,tls-ciphers=<list>]\n"
2138 " [,tls-channel=[main|display|cursor|inputs|record|playback]]\n"
2139 " [,plaintext-channel=[main|display|cursor|inputs|record|playback]]\n"
2140 " [,sasl=on|off][,disable-ticketing=on|off]\n"
2141 " [,password=<string>][,password-secret=<secret-id>]\n"
2142 " [,image-compression=[auto_glz|auto_lz|quic|glz|lz|off]]\n"
2143 " [,jpeg-wan-compression=[auto|never|always]]\n"
2144 " [,zlib-glz-wan-compression=[auto|never|always]]\n"
2145 " [,streaming-video=[off|all|filter]][,disable-copy-paste=on|off]\n"
2146 " [,disable-agent-file-xfer=on|off][,agent-mouse=[on|off]]\n"
2147 " [,playback-compression=[on|off]][,seamless-migration=[on|off]]\n"
2148 " [,gl=[on|off]][,rendernode=<file>]\n"
2150 " at least one of {port, tls-port} is mandatory\n",
2154 ``
-spice option
[,option
[,...]]``
2155 Enable the spice remote desktop protocol
. Valid options are
2158 Set the TCP port spice is listening on
for plaintext channels
.
2161 Set the IP address spice is listening on
. Default is any
2164 ``ipv4
=on|off``
; \ ``ipv6
=on|off``
; \ ``unix
=on|off``
2165 Force
using the specified IP version
.
2167 ``password
=<string
>``
2168 Set the password you need to authenticate
.
2170 This option is deprecated and insecure because it leaves the
2171 password visible
in the process listing
. Use ``password
-secret``
2174 ``password
-secret
=<secret
-id
>``
2175 Set the ID of the ``secret`` object containing the password
2176 you need to authenticate
.
2179 Require that the client use SASL to authenticate with the spice
.
2180 The exact choice of authentication method used is controlled
2181 from the system
/ user
's SASL configuration file for the 'qemu
'
2182 service. This is typically found in /etc/sasl2/qemu.conf. If
2183 running QEMU as an unprivileged user, an environment variable
2184 SASL\_CONF\_PATH can be used to make it search alternate
2185 locations for the service config. While some SASL auth methods
2186 can also provide data encryption (eg GSSAPI), it is recommended
2187 that SASL always be combined with the 'tls
' and 'x509
' settings
2188 to enable use of SSL and server certificates. This ensures a
2189 data encryption preventing compromise of authentication
2192 ``disable-ticketing=on|off``
2193 Allow client connects without authentication.
2195 ``disable-copy-paste=on|off``
2196 Disable copy paste between the client and the guest.
2198 ``disable-agent-file-xfer=on|off``
2199 Disable spice-vdagent based file-xfer between the client and the
2203 Set the TCP port spice is listening on for encrypted channels.
2206 Set the x509 file directory. Expects same filenames as -vnc
2209 ``x509-key-file=<file>``; \ ``x509-key-password=<file>``; \ ``x509-cert-file=<file>``; \ ``x509-cacert-file=<file>``; \ ``x509-dh-key-file=<file>``
2210 The x509 file names can also be configured individually.
2212 ``tls-ciphers=<list>``
2213 Specify which ciphers to use.
2215 ``tls-channel=[main|display|cursor|inputs|record|playback]``; \ ``plaintext-channel=[main|display|cursor|inputs|record|playback]``
2216 Force specific channel to be used with or without TLS
2217 encryption. The options can be specified multiple times to
2218 configure multiple channels. The special name "default" can be
2219 used to set the default mode. For channels which are not
2220 explicitly forced into one mode the spice client is allowed to
2221 pick tls/plaintext as he pleases.
2223 ``image-compression=[auto_glz|auto_lz|quic|glz|lz|off]``
2224 Configure image compression (lossless). Default is auto\_glz.
2226 ``jpeg-wan-compression=[auto|never|always]``; \ ``zlib-glz-wan-compression=[auto|never|always]``
2227 Configure wan image compression (lossy for slow links). Default
2230 ``streaming-video=[off|all|filter]``
2231 Configure video stream detection. Default is off.
2233 ``agent-mouse=[on|off]``
2234 Enable/disable passing mouse events via vdagent. Default is on.
2236 ``playback-compression=[on|off]``
2237 Enable/disable audio stream compression (using celt 0.5.1).
2240 ``seamless-migration=[on|off]``
2241 Enable/disable spice seamless migration. Default is off.
2244 Enable/disable OpenGL context. Default is off.
2246 ``rendernode=<file>``
2247 DRM render node for OpenGL rendering. If not specified, it will
2248 pick the first available. (Since 2.9)
2251 DEF("portrait", 0, QEMU_OPTION_portrait,
2252 "-portrait rotate graphical output 90 deg left (only PXA LCD)\n",
2256 Rotate graphical output 90 deg left (only PXA LCD).
2259 DEF("rotate", HAS_ARG, QEMU_OPTION_rotate,
2260 "-rotate <deg> rotate graphical output some deg left (only PXA LCD)\n",
2264 Rotate graphical output some deg left (only PXA LCD).
2267 DEF("vga", HAS_ARG, QEMU_OPTION_vga,
2268 "-vga [std|cirrus|vmware|qxl|xenfb|tcx|cg3|virtio|none]\n"
2269 " select video card type\n", QEMU_ARCH_ALL)
2272 Select type of VGA card to emulate. Valid values for type are
2275 Cirrus Logic GD5446 Video card. All Windows versions starting
2276 from Windows 95 should recognize and use this graphic card. For
2277 optimal performances, use 16 bit color depth in the guest and
2278 the host OS. (This card was the default before QEMU 2.2)
2281 Standard VGA card with Bochs VBE extensions. If your guest OS
2282 supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if
2283 you want to use high resolution modes (>= 1280x1024x16) then you
2284 should use this option. (This card is the default since QEMU
2288 VMWare SVGA-II compatible adapter. Use it if you have
2289 sufficiently recent XFree86/XOrg server or Windows guest with a
2290 driver for this card.
2293 QXL paravirtual graphic card. It is VGA compatible (including
2294 VESA 2.0 VBE support). Works best with qxl guest drivers
2295 installed though. Recommended choice when using the spice
2299 (sun4m only) Sun TCX framebuffer. This is the default
2300 framebuffer for sun4m machines and offers both 8-bit and 24-bit
2301 colour depths at a fixed resolution of 1024x768.
2304 (sun4m only) Sun cgthree framebuffer. This is a simple 8-bit
2305 framebuffer for sun4m machines available in both 1024x768
2306 (OpenBIOS) and 1152x900 (OBP) resolutions aimed at people
2307 wishing to run older Solaris versions.
2316 DEF("full-screen", 0, QEMU_OPTION_full_screen,
2317 "-full-screen start in full screen\n", QEMU_ARCH_ALL)
2320 Start in full screen.
2323 DEF("g", HAS_ARG, QEMU_OPTION_g ,
2324 "-g WxH[xDEPTH] Set the initial graphical resolution and depth\n",
2325 QEMU_ARCH_PPC | QEMU_ARCH_SPARC | QEMU_ARCH_M68K)
2327 ``-g`` *width*\ ``x``\ *height*\ ``[x``\ *depth*\ ``]``
2328 Set the initial graphical resolution and depth (PPC, SPARC only).
2330 For PPC the default is 800x600x32.
2332 For SPARC with the TCX graphics device, the default is 1024x768x8
2333 with the option of 1024x768x24. For cgthree, the default is
2334 1024x768x8 with the option of 1152x900x8 for people who wish to use
2338 DEF("vnc", HAS_ARG, QEMU_OPTION_vnc ,
2339 "-vnc <display> shorthand for -display vnc=<display>\n", QEMU_ARCH_ALL)
2341 ``-vnc display[,option[,option[,...]]]``
2342 Normally, if QEMU is compiled with graphical window support, it
2343 displays output such as guest graphics, guest console, and the QEMU
2344 monitor in a window. With this option, you can have QEMU listen on
2345 VNC display display and redirect the VGA display over the VNC
2346 session. It is very useful to enable the usb tablet device when
2347 using this option (option ``-device usb-tablet``). When using the
2348 VNC display, you must use the ``-k`` parameter to set the keyboard
2349 layout if you are not using en-us. Valid syntax for the display is
2352 With this option, QEMU will try next available VNC displays,
2353 until the number L, if the origianlly defined "-vnc display" is
2354 not available, e.g. port 5900+display is already used by another
2355 application. By default, to=0.
2358 TCP connections will only be allowed from host on display d. By
2359 convention the TCP port is 5900+d. Optionally, host can be
2360 omitted in which case the server will accept connections from
2364 Connections will be allowed over UNIX domain sockets where path
2365 is the location of a unix socket to listen for connections on.
2368 VNC is initialized but not started. The monitor ``change``
2369 command can be used to later start the VNC server.
2371 Following the display value there may be one or more option flags
2372 separated by commas. Valid options are
2375 Connect to a listening VNC client via a "reverse" connection.
2376 The client is specified by the display. For reverse network
2377 connections (host:d,``reverse``), the d argument is a TCP port
2378 number, not a display number.
2380 ``websocket=on|off``
2381 Opens an additional TCP listening port dedicated to VNC
2382 Websocket connections. If a bare websocket option is given, the
2383 Websocket port is 5700+display. An alternative port can be
2384 specified with the syntax ``websocket``\ =port.
2386 If host is specified connections will only be allowed from this
2387 host. It is possible to control the websocket listen address
2388 independently, using the syntax ``websocket``\ =host:port.
2390 If no TLS credentials are provided, the websocket connection
2391 runs in unencrypted mode. If TLS credentials are provided, the
2392 websocket connection requires encrypted client connections.
2395 Require that password based authentication is used for client
2398 The password must be set separately using the ``set_password``
2399 command in the :ref:`QEMU monitor`. The
2400 syntax to change your password is:
2401 ``set_password <protocol> <password>`` where <protocol> could be
2402 either "vnc" or "spice".
2404 If you would like to change <protocol> password expiration, you
2405 should use ``expire_password <protocol> <expiration-time>``
2406 where expiration time could be one of the following options:
2407 now, never, +seconds or UNIX time of expiration, e.g. +60 to
2408 make password expire in 60 seconds, or 1335196800 to make
2409 password expire on "Mon Apr 23 12:00:00 EDT 2012" (UNIX time for
2410 this date and time).
2412 You can also use keywords "now" or "never" for the expiration
2413 time to allow <protocol> password to expire immediately or never
2416 ``password-secret=<secret-id>``
2417 Require that password based authentication is used for client
2418 connections, using the password provided by the ``secret``
2419 object identified by ``secret-id``.
2422 Provides the ID of a set of TLS credentials to use to secure the
2423 VNC server. They will apply to both the normal VNC server socket
2424 and the websocket socket (if enabled). Setting TLS credentials
2425 will cause the VNC server socket to enable the VeNCrypt auth
2426 mechanism. The credentials should have been previously created
2427 using the ``-object tls-creds`` argument.
2430 Provides the ID of the QAuthZ authorization object against which
2431 the client's x509 distinguished name will validated
. This object
2432 is only resolved at time of use
, so can be deleted and recreated
2433 on the fly
while the VNC server is active
. If missing
, it will
2434 default to denying access
.
2437 Require that the client use SASL to authenticate with the VNC
2438 server
. The exact choice of authentication method used is
2439 controlled from the system
/ user
's SASL configuration file for
2440 the 'qemu
' service. This is typically found in
2441 /etc/sasl2/qemu.conf. If running QEMU as an unprivileged user,
2442 an environment variable SASL\_CONF\_PATH can be used to make it
2443 search alternate locations for the service config. While some
2444 SASL auth methods can also provide data encryption (eg GSSAPI),
2445 it is recommended that SASL always be combined with the 'tls
'
2446 and 'x509
' settings to enable use of SSL and server
2447 certificates. This ensures a data encryption preventing
2448 compromise of authentication credentials. See the
2449 :ref:`VNC security` section in the System Emulation Users Guide
2450 for details on using SASL authentication.
2453 Provides the ID of the QAuthZ authorization object against which
2454 the client's SASL username will validated
. This object is only
2455 resolved at time of use
, so can be deleted and recreated on the
2456 fly
while the VNC server is active
. If missing
, it will
default
2460 Legacy method
for enabling authorization of clients against the
2461 x509 distinguished name and SASL username
. It results
in the
2462 creation of two ``authz
-list`` objects with IDs of
2463 ``vnc
.username`` and ``vnc
.x509dname``
. The rules
for these
2464 objects must be configured with the HMP ACL commands
.
2466 This option is deprecated and should no longer be used
. The
new
2467 ``sasl
-authz`` and ``tls
-authz`` options are a replacement
.
2470 Enable lossy compression
methods (gradient
, JPEG
, ...). If
this
2471 option is set
, VNC client may receive lossy framebuffer updates
2472 depending on its encoding settings
. Enabling
this option can
2473 save a lot of bandwidth at the expense of quality
.
2475 ``non
-adaptive
=on|off``
2476 Disable adaptive encodings
. Adaptive encodings are enabled by
2477 default. An adaptive encoding will
try to detect frequently
2478 updated screen regions
, and send updates
in these regions
using
2479 a lossy
encoding (like JPEG
). This can be really helpful to save
2480 bandwidth when playing videos
. Disabling adaptive encodings
2481 restores the original
static behavior of encodings like Tight
.
2483 ``share
=[allow
-exclusive|force
-shared|ignore
]``
2484 Set display sharing policy
. 'allow-exclusive' allows clients to
2485 ask
for exclusive access
. As suggested by the rfb spec
this is
2486 implemented by dropping other connections
. Connecting multiple
2487 clients
in parallel requires all clients asking
for a shared
2488 session (vncviewer
: -shared
switch). This is the
default.
2489 'force-shared' disables exclusive client access
. Useful
for
2490 shared desktop sessions
, where you don
't want someone forgetting
2491 specify -shared disconnect everybody else. 'ignore
' completely
2492 ignores the shared flag and allows everybody connect
2493 unconditionally. Doesn't conform to the rfb spec but is
2494 traditional QEMU behavior
.
2497 Set keyboard delay
, for key down and key up events
, in
2498 milliseconds
. Default is
10. Keyboards are low
-bandwidth
2499 devices
, so
this slowdown can help the device and guest to keep
2500 up and not lose events
in case events are arriving
in bulk
.
2501 Possible causes
for the latter are flaky network connections
, or
2502 scripts
for automated testing
.
2504 ``audiodev
=audiodev``
2505 Use the specified audiodev when the VNC client requests audio
2506 transmission
. When not
using an
-audiodev argument
, this option
2507 must be omitted
, otherwise is must be present and specify a
2510 ``power
-control
=on|off``
2511 Permit the remote client to issue shutdown
, reboot or reset power
2515 ARCHHEADING(, QEMU_ARCH_I386
)
2517 ARCHHEADING(i386 target only
:, QEMU_ARCH_I386
)
2519 DEF("win2k-hack", 0, QEMU_OPTION_win2k_hack
,
2520 "-win2k-hack use it when installing Windows 2000 to avoid a disk full bug\n",
2524 Use it when installing Windows
2000 to avoid a disk full bug
. After
2525 Windows
2000 is installed
, you no longer need
this option (this
2526 option slows down the IDE transfers
).
2529 DEF("no-fd-bootchk", 0, QEMU_OPTION_no_fd_bootchk
,
2530 "-no-fd-bootchk disable boot signature checking for floppy disks\n",
2534 Disable boot signature checking
for floppy disks
in BIOS
. May be
2535 needed to boot from old floppy disks
.
2538 DEF("no-acpi", 0, QEMU_OPTION_no_acpi
,
2539 "-no-acpi disable ACPI\n", QEMU_ARCH_I386 | QEMU_ARCH_ARM
)
2542 Disable
ACPI (Advanced Configuration and Power Interface
) support
.
2543 Use it
if your guest OS complains about ACPI
problems (PC target
2547 DEF("no-hpet", 0, QEMU_OPTION_no_hpet
,
2548 "-no-hpet disable HPET\n", QEMU_ARCH_I386
)
2551 Disable HPET support
.
2554 DEF("acpitable", HAS_ARG
, QEMU_OPTION_acpitable
,
2555 "-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n][,asl_compiler_id=str][,asl_compiler_rev=n][,{data|file}=file1[:file2]...]\n"
2556 " ACPI table description\n", QEMU_ARCH_I386
)
2558 ``
-acpitable
[sig
=str
][,rev
=n
][,oem_id
=str
][,oem_table_id
=str
][,oem_rev
=n
] [,asl_compiler_id
=str
][,asl_compiler_rev
=n
][,data
=file1
[:file2
]...]``
2559 Add ACPI table with specified header fields and context from
2560 specified files
. For file
=, take whole ACPI table from the specified
2561 files
, including all ACPI
headers (possible overridden by other
2562 options
). For data
=, only data portion of the table is used
, all
2563 header information is specified
in the command line
. If a SLIC table
2564 is supplied to QEMU
, then the SLIC
's oem\_id and oem\_table\_id
2565 fields will override the same in the RSDT and the FADT (a.k.a.
2566 FACP), in order to ensure the field matches required by the
2567 Microsoft SLIC spec and the ACPI spec.
2570 DEF("smbios", HAS_ARG, QEMU_OPTION_smbios,
2571 "-smbios file=binary\n"
2572 " load SMBIOS entry from binary file\n"
2573 "-smbios type=0[,vendor=str][,version=str][,date=str][,release=%d.%d]\n"
2575 " specify SMBIOS type 0 fields\n"
2576 "-smbios type=1[,manufacturer=str][,product=str][,version=str][,serial=str]\n"
2577 " [,uuid=uuid][,sku=str][,family=str]\n"
2578 " specify SMBIOS type 1 fields\n"
2579 "-smbios type=2[,manufacturer=str][,product=str][,version=str][,serial=str]\n"
2580 " [,asset=str][,location=str]\n"
2581 " specify SMBIOS type 2 fields\n"
2582 "-smbios type=3[,manufacturer=str][,version=str][,serial=str][,asset=str]\n"
2584 " specify SMBIOS type 3 fields\n"
2585 "-smbios type=4[,sock_pfx=str][,manufacturer=str][,version=str][,serial=str]\n"
2586 " [,asset=str][,part=str][,max-speed=%d][,current-speed=%d]\n"
2587 " [,processor-id=%d]\n"
2588 " specify SMBIOS type 4 fields\n"
2589 "-smbios type=8[,external_reference=str][,internal_reference=str][,connector_type=%d][,port_type=%d]\n"
2590 " specify SMBIOS type 8 fields\n"
2591 "-smbios type=11[,value=str][,path=filename]\n"
2592 " specify SMBIOS type 11 fields\n"
2593 "-smbios type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str]\n"
2594 " [,asset=str][,part=str][,speed=%d]\n"
2595 " specify SMBIOS type 17 fields\n"
2596 "-smbios type=41[,designation=str][,kind=str][,instance=%d][,pcidev=str]\n"
2597 " specify SMBIOS type 41 fields\n",
2598 QEMU_ARCH_I386 | QEMU_ARCH_ARM)
2600 ``-smbios file=binary``
2601 Load SMBIOS entry from binary file.
2603 ``-smbios type=0[,vendor=str][,version=str][,date=str][,release=%d.%d][,uefi=on|off]``
2604 Specify SMBIOS type 0 fields
2606 ``-smbios type=1[,manufacturer=str][,product=str][,version=str][,serial=str][,uuid=uuid][,sku=str][,family=str]``
2607 Specify SMBIOS type 1 fields
2609 ``-smbios type=2[,manufacturer=str][,product=str][,version=str][,serial=str][,asset=str][,location=str]``
2610 Specify SMBIOS type 2 fields
2612 ``-smbios type=3[,manufacturer=str][,version=str][,serial=str][,asset=str][,sku=str]``
2613 Specify SMBIOS type 3 fields
2615 ``-smbios type=4[,sock_pfx=str][,manufacturer=str][,version=str][,serial=str][,asset=str][,part=str][,processor-id=%d]``
2616 Specify SMBIOS type 4 fields
2618 ``-smbios type=11[,value=str][,path=filename]``
2619 Specify SMBIOS type 11 fields
2621 This argument can be repeated multiple times, and values are added in the order they are parsed.
2622 Applications intending to use OEM strings data are encouraged to use their application name as
2623 a prefix for the value string. This facilitates passing information for multiple applications
2626 The ``value=str`` syntax provides the string data inline, while the ``path=filename`` syntax
2627 loads data from a file on disk. Note that the file is not permitted to contain any NUL bytes.
2629 Both the ``value`` and ``path`` options can be repeated multiple times and will be added to
2630 the SMBIOS table in the order in which they appear.
2632 Note that on the x86 architecture, the total size of all SMBIOS tables is limited to 65535
2633 bytes. Thus the OEM strings data is not suitable for passing large amounts of data into the
2634 guest. Instead it should be used as a indicator to inform the guest where to locate the real
2635 data set, for example, by specifying the serial ID of a block device.
2637 An example passing three strings is
2641 -smbios type=11,value=cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/,\\
2642 value=anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os,\\
2643 path=/some/file/with/oemstringsdata.txt
2645 In the guest OS this is visible with the ``dmidecode`` command
2650 Handle 0x0E00, DMI type 11, 5 bytes
2652 String 1: cloud-init:ds=nocloud-net;s=http://10.10.0.1:8000/
2653 String 2: anaconda:method=http://dl.fedoraproject.org/pub/fedora/linux/releases/25/x86_64/os
2654 String 3: myapp:some extra data
2657 ``-smbios type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str][,asset=str][,part=str][,speed=%d]``
2658 Specify SMBIOS type 17 fields
2660 ``-smbios type=41[,designation=str][,kind=str][,instance=%d][,pcidev=str]``
2661 Specify SMBIOS type 41 fields
2663 This argument can be repeated multiple times. Its main use is to allow network interfaces be created
2664 as ``enoX`` on Linux, with X being the instance number, instead of the name depending on the interface
2665 position on the PCI bus.
2667 Here is an example of use:
2671 -netdev user,id=internet \\
2672 -device virtio-net-pci,mac=50:54:00:00:00:42,netdev=internet,id=internet-dev \\
2673 -smbios type=41,designation='Onboard LAN
',instance=1,kind=ethernet,pcidev=internet-dev
2675 In the guest OS, the device should then appear as ``eno1``:
2680 lo UNKNOWN 00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
2681 eno1 UP 50:54:00:00:00:42 <BROADCAST,MULTICAST,UP,LOWER_UP>
2683 Currently, the PCI device has to be attached to the root bus.
2689 DEFHEADING(Network options:)
2691 DEF("netdev", HAS_ARG, QEMU_OPTION_netdev,
2693 "-netdev user,id=str[,ipv4=on|off][,net=addr[/mask]][,host=addr]\n"
2694 " [,ipv6=on|off][,ipv6-net=addr[/int]][,ipv6-host=addr]\n"
2695 " [,restrict=on|off][,hostname=host][,dhcpstart=addr]\n"
2696 " [,dns=addr][,ipv6-dns=addr][,dnssearch=domain][,domainname=domain]\n"
2697 " [,tftp=dir][,tftp-server-name=name][,bootfile=f][,hostfwd=rule][,guestfwd=rule]"
2699 "[,smb=dir[,smbserver=addr]]\n"
2701 " configure a user mode network backend with ID 'str
',\n"
2702 " its DHCP server and optional services\n"
2705 "-netdev tap,id=str,ifname=name\n"
2706 " configure a host TAP network backend with ID 'str
'\n"
2708 "-netdev tap,id=str[,fd=h][,fds=x:y:...:z][,ifname=name][,script=file][,downscript=dfile]\n"
2709 " [,br=bridge][,helper=helper][,sndbuf=nbytes][,vnet_hdr=on|off][,vhost=on|off]\n"
2710 " [,vhostfd=h][,vhostfds=x:y:...:z][,vhostforce=on|off][,queues=n]\n"
2712 " configure a host TAP network backend with ID 'str
'\n"
2713 " connected to a bridge (default=" DEFAULT_BRIDGE_INTERFACE ")\n"
2714 " use network scripts 'file
' (default=" DEFAULT_NETWORK_SCRIPT ")\n"
2715 " to configure it and 'dfile
' (default=" DEFAULT_NETWORK_DOWN_SCRIPT ")\n"
2716 " to deconfigure it\n"
2717 " use '[down
]script
=no
' to disable script execution\n"
2718 " use network helper 'helper
' (default=" DEFAULT_BRIDGE_HELPER ") to\n"
2720 " use 'fd
=h
' to connect to an already opened TAP interface\n"
2721 " use 'fds
=x
:y
:...:z
' to connect to already opened multiqueue capable TAP interfaces\n"
2722 " use 'sndbuf
=nbytes
' to limit the size of the send buffer (the\n"
2723 " default is disabled 'sndbuf
=0' to enable flow control set 'sndbuf
=1048576')\n"
2724 " use vnet_hdr=off to avoid enabling the IFF_VNET_HDR tap flag\n"
2725 " use vnet_hdr=on to make the lack of IFF_VNET_HDR support an error condition\n"
2726 " use vhost=on to enable experimental in kernel accelerator\n"
2727 " (only has effect for virtio guests which use MSIX)\n"
2728 " use vhostforce=on to force vhost on for non-MSIX virtio guests\n"
2729 " use 'vhostfd
=h
' to connect to an already opened vhost net device\n"
2730 " use 'vhostfds
=x
:y
:...:z to connect to multiple already opened vhost net devices
\n"
2731 " use
'queues=n' to specify the number of queues to be created
for multiqueue TAP
\n"
2732 " use
'poll-us=n' to specify the maximum number of microseconds that could be
\n"
2733 " spent on busy polling
for vhost net
\n"
2734 "-netdev bridge
,id
=str
[,br
=bridge
][,helper
=helper
]\n"
2735 " configure a host TAP network backend with ID
'str' that is
\n"
2736 " connected to a
bridge (default=" DEFAULT_BRIDGE_INTERFACE ")\n"
2737 " using the program
'helper (default=" DEFAULT_BRIDGE_HELPER ")\n"
2740 "-netdev l2tpv3,id=str,src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport]\n"
2741 " [,rxsession=rxsession],txsession=txsession[,ipv6=on|off][,udp=on|off]\n"
2742 " [,cookie64=on|off][,counter][,pincounter][,txcookie=txcookie]\n"
2743 " [,rxcookie=rxcookie][,offset=offset]\n"
2744 " configure a network backend with ID 'str
' connected to\n"
2745 " an Ethernet over L2TPv3 pseudowire.\n"
2746 " Linux kernel 3.3+ as well as most routers can talk\n"
2747 " L2TPv3. This transport allows connecting a VM to a VM,\n"
2748 " VM to a router and even VM to Host. It is a nearly-universal\n"
2749 " standard (RFC3931). Note - this implementation uses static\n"
2750 " pre-configured tunnels (same as the Linux kernel).\n"
2751 " use 'src
=' to specify source address\n"
2752 " use 'dst
=' to specify destination address\n"
2753 " use 'udp
=on
' to specify udp encapsulation\n"
2754 " use 'srcport
=' to specify source udp port\n"
2755 " use 'dstport
=' to specify destination udp port\n"
2756 " use 'ipv6
=on
' to force v6\n"
2757 " L2TPv3 uses cookies to prevent misconfiguration as\n"
2758 " well as a weak security measure\n"
2759 " use 'rxcookie
=0x012345678' to specify a rxcookie\n"
2760 " use 'txcookie
=0x012345678' to specify a txcookie\n"
2761 " use 'cookie64
=on
' to set cookie size to 64 bit, otherwise 32\n"
2762 " use 'counter
=off
' to force a 'cut
-down
' L2TPv3 with no counter\n"
2763 " use 'pincounter
=on
' to work around broken counter handling in peer\n"
2764 " use 'offset
=X
' to add an extra offset between header and data\n"
2766 "-netdev socket,id=str[,fd=h][,listen=[host]:port][,connect=host:port]\n"
2767 " configure a network backend to connect to another network\n"
2768 " using a socket connection\n"
2769 "-netdev socket,id=str[,fd=h][,mcast=maddr:port[,localaddr=addr]]\n"
2770 " configure a network backend to connect to a multicast maddr and port\n"
2771 " use 'localaddr
=addr
' to specify the host address to send packets from\n"
2772 "-netdev socket,id=str[,fd=h][,udp=host:port][,localaddr=host:port]\n"
2773 " configure a network backend to connect to another network\n"
2774 " using an UDP tunnel\n"
2775 "-netdev stream,id=str[,server=on|off],addr.type=inet,addr.host=host,addr.port=port\n"
2776 "-netdev stream,id=str[,server=on|off],addr.type=unix,addr.path=path\n"
2777 "-netdev stream,id=str[,server=on|off],addr.type=fd,addr.str=file-descriptor\n"
2778 " configure a network backend to connect to another network\n"
2779 " using a socket connection in stream mode.\n"
2780 "-netdev dgram,id=str,remote.type=inet,remote.host=maddr,remote.port=port[,local.type=inet,local.host=addr]\n"
2781 "-netdev dgram,id=str,remote.type=inet,remote.host=maddr,remote.port=port[,local.type=fd,local.str=file-descriptor]\n"
2782 " configure a network backend to connect to a multicast maddr and port\n"
2783 " use ``local.host=addr`` to specify the host address to send packets from\n"
2784 "-netdev dgram,id=str,local.type=inet,local.host=addr,local.port=port[,remote.type=inet,remote.host=addr,remote.port=port]\n"
2785 "-netdev dgram,id=str,local.type=fd,local.str=file-descriptor\n"
2786 " configure a network backend to connect to another network\n"
2787 " using an UDP tunnel\n"
2789 "-netdev vde,id=str[,sock=socketpath][,port=n][,group=groupname][,mode=octalmode]\n"
2790 " configure a network backend to connect to port 'n
' of a vde switch\n"
2791 " running on host and listening for incoming connections on 'socketpath
'.\n"
2792 " Use group 'groupname
' and mode 'octalmode
' to change default\n"
2793 " ownership and permissions for communication port.\n"
2795 #ifdef CONFIG_NETMAP
2796 "-netdev netmap,id=str,ifname=name[,devname=nmname]\n"
2797 " attach to the existing netmap-enabled network interface 'name
', or to a\n"
2798 " VALE port (created on the fly) called 'name
' ('nmname
' is name of the \n"
2799 " netmap device, defaults to '/dev
/netmap
')\n"
2802 "-netdev vhost-user,id=str,chardev=dev[,vhostforce=on|off]\n"
2803 " configure a vhost-user network, backed by a chardev 'dev
'\n"
2806 "-netdev vhost-vdpa,id=str[,vhostdev=/path/to/dev][,vhostfd=h]\n"
2807 " configure a vhost-vdpa network,Establish a vhost-vdpa netdev\n"
2808 " use 'vhostdev
=/path
/to
/dev
' to open a vhost vdpa device\n"
2809 " use 'vhostfd
=h
' to connect to an already opened vhost vdpa device\n"
2812 "-netdev vmnet-host,id=str[,isolated=on|off][,net-uuid=uuid]\n"
2813 " [,start-address=addr,end-address=addr,subnet-mask=mask]\n"
2814 " configure a vmnet network backend in host mode with ID 'str
',\n"
2815 " isolate this interface from others with 'isolated
',\n"
2816 " configure the address range and choose a subnet mask,\n"
2817 " specify network UUID 'uuid
' to disable DHCP and interact with\n"
2818 " vmnet-host interfaces within this isolated network\n"
2819 "-netdev vmnet-shared,id=str[,isolated=on|off][,nat66-prefix=addr]\n"
2820 " [,start-address=addr,end-address=addr,subnet-mask=mask]\n"
2821 " configure a vmnet network backend in shared mode with ID 'str
',\n"
2822 " configure the address range and choose a subnet mask,\n"
2823 " set IPv6 ULA prefix (of length 64) to use for internal network,\n"
2824 " isolate this interface from others with 'isolated
'\n"
2825 "-netdev vmnet-bridged,id=str,ifname=name[,isolated=on|off]\n"
2826 " configure a vmnet network backend in bridged mode with ID 'str
',\n"
2827 " use 'ifname
=name
' to select a physical network interface to be bridged,\n"
2828 " isolate this interface from others with 'isolated
'\n"
2830 "-netdev hubport,id=str,hubid=n[,netdev=nd]\n"
2831 " configure a hub port on the hub with ID 'n
'\n", QEMU_ARCH_ALL)
2832 DEF("nic", HAS_ARG, QEMU_OPTION_nic,
2843 #ifdef CONFIG_NETMAP
2850 "vmnet-host|vmnet-shared|vmnet-bridged|"
2852 "socket][,option][,...][mac=macaddr]\n"
2853 " initialize an on-board / default host NIC (using MAC address\n"
2854 " macaddr) and connect it to the given host network backend\n"
2855 "-nic none use it alone to have zero network devices (the default is to\n"
2856 " provided a 'user
' network connection)\n",
2858 DEF("net", HAS_ARG, QEMU_OPTION_net,
2859 "-net nic[,macaddr=mac][,model=type][,name=str][,addr=str][,vectors=v]\n"
2860 " configure or create an on-board (or machine default) NIC and\n"
2861 " connect it to hub 0 (please use -nic unless you need a hub)\n"
2871 #ifdef CONFIG_NETMAP
2875 "vmnet-host|vmnet-shared|vmnet-bridged|"
2877 "socket][,option][,option][,...]\n"
2878 " old way to initialize a host network interface\n"
2879 " (use the -netdev option if possible instead)\n", QEMU_ARCH_ALL)
2881 ``-nic [tap|bridge|user|l2tpv3|vde|netmap|vhost-user|socket][,...][,mac=macaddr][,model=mn]``
2882 This option is a shortcut for configuring both the on-board
2883 (default) guest NIC hardware and the host network backend in one go.
2884 The host backend options are the same as with the corresponding
2885 ``-netdev`` options below. The guest NIC model can be set with
2886 ``model=modelname``. Use ``model=help`` to list the available device
2887 types. The hardware MAC address can be set with ``mac=macaddr``.
2889 The following two example do exactly the same, to show how ``-nic``
2890 can be used to shorten the command line length:
2894 |qemu_system| -netdev user,id=n1,ipv6=off -device e1000,netdev=n1,mac=52:54:98:76:54:32
2895 |qemu_system| -nic user,ipv6=off,model=e1000,mac=52:54:98:76:54:32
2898 Indicate that no network devices should be configured. It is used to
2899 override the default configuration (default NIC with "user" host
2900 network backend) which is activated if no other networking options
2903 ``-netdev user,id=id[,option][,option][,...]``
2904 Configure user mode host network backend which requires no
2905 administrator privilege to run. Valid options are:
2908 Assign symbolic name for use in monitor commands.
2910 ``ipv4=on|off and ipv6=on|off``
2911 Specify that either IPv4 or IPv6 must be enabled. If neither is
2912 specified both protocols are enabled.
2915 Set IP network address the guest will see. Optionally specify
2916 the netmask, either in the form a.b.c.d or as number of valid
2917 top-most bits. Default is 10.0.2.0/24.
2920 Specify the guest-visible address of the host. Default is the
2921 2nd IP in the guest network, i.e. x.x.x.2.
2923 ``ipv6-net=addr[/int]``
2924 Set IPv6 network address the guest will see (default is
2925 fec0::/64). The network prefix is given in the usual hexadecimal
2926 IPv6 address notation. The prefix size is optional, and is given
2927 as the number of valid top-most bits (default is 64).
2930 Specify the guest-visible IPv6 address of the host. Default is
2931 the 2nd IPv6 in the guest network, i.e. xxxx::2.
2934 If this option is enabled, the guest will be isolated, i.e. it
2935 will not be able to contact the host and no guest IP packets
2936 will be routed over the host to the outside. This option does
2937 not affect any explicitly set forwarding rules.
2940 Specifies the client hostname reported by the built-in DHCP
2944 Specify the first of the 16 IPs the built-in DHCP server can
2945 assign. Default is the 15th to 31st IP in the guest network,
2946 i.e. x.x.x.15 to x.x.x.31.
2949 Specify the guest-visible address of the virtual nameserver. The
2950 address must be different from the host address. Default is the
2951 3rd IP in the guest network, i.e. x.x.x.3.
2954 Specify the guest-visible address of the IPv6 virtual
2955 nameserver. The address must be different from the host address.
2956 Default is the 3rd IP in the guest network, i.e. xxxx::3.
2958 ``dnssearch=domain``
2959 Provides an entry for the domain-search list sent by the
2960 built-in DHCP server. More than one domain suffix can be
2961 transmitted by specifying this option multiple times. If
2962 supported, this will cause the guest to automatically try to
2963 append the given domain suffix(es) in case a domain name can not
2970 |qemu_system| -nic user,dnssearch=mgmt.example.org,dnssearch=example.org
2972 ``domainname=domain``
2973 Specifies the client domain name reported by the built-in DHCP
2977 When using the user mode network stack, activate a built-in TFTP
2978 server. The files in dir will be exposed as the root of a TFTP
2979 server. The TFTP client on the guest must be configured in
2980 binary mode (use the command ``bin`` of the Unix TFTP client).
2982 ``tftp-server-name=name``
2983 In BOOTP reply, broadcast name as the "TFTP server name"
2984 (RFC2132 option 66). This can be used to advise the guest to
2985 load boot files or configurations from a different server than
2989 When using the user mode network stack, broadcast file as the
2990 BOOTP filename. In conjunction with ``tftp``, this can be used
2991 to network boot a guest from a local directory.
2993 Example (using pxelinux):
2997 |qemu_system| -hda linux.img -boot n -device e1000,netdev=n1 \\
2998 -netdev user,id=n1,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
3000 ``smb=dir[,smbserver=addr]``
3001 When using the user mode network stack, activate a built-in SMB
3002 server so that Windows OSes can access to the host files in
3003 ``dir`` transparently. The IP address of the SMB server can be
3004 set to addr. By default the 4th IP in the guest network is used,
3007 In the guest Windows OS, the line:
3013 must be added in the file ``C:\WINDOWS\LMHOSTS`` (for windows
3014 9x/Me) or ``C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS`` (Windows
3017 Then ``dir`` can be accessed in ``\\smbserver\qemu``.
3019 Note that a SAMBA server must be installed on the host OS.
3021 ``hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport``
3022 Redirect incoming TCP or UDP connections to the host port
3023 hostport to the guest IP address guestaddr on guest port
3024 guestport. If guestaddr is not specified, its value is x.x.x.15
3025 (default first address given by the built-in DHCP server). By
3026 specifying hostaddr, the rule can be bound to a specific host
3027 interface. If no connection type is set, TCP is used. This
3028 option can be given multiple times.
3030 For example, to redirect host X11 connection from screen 1 to
3031 guest screen 0, use the following:
3036 |qemu_system| -nic user,hostfwd=tcp:127.0.0.1:6001-:6000
3037 # this host xterm should open in the guest X11 server
3040 To redirect telnet connections from host port 5555 to telnet
3041 port on the guest, use the following:
3046 |qemu_system| -nic user,hostfwd=tcp::5555-:23
3047 telnet localhost 5555
3049 Then when you use on the host ``telnet localhost 5555``, you
3050 connect to the guest telnet server.
3052 ``guestfwd=[tcp]:server:port-dev``; \ ``guestfwd=[tcp]:server:port-cmd:command``
3053 Forward guest TCP connections to the IP address server on port
3054 port to the character device dev or to a program executed by
3055 cmd:command which gets spawned for each connection. This option
3056 can be given multiple times.
3058 You can either use a chardev directly and have that one used
3059 throughout QEMU's lifetime
, like
in the following example
:
3063 # open
10.10.1.1:4321 on bootup
, connect
10.0.2.100:1234 to it whenever
3064 # the guest accesses it
3065 |qemu_system|
-nic user
,guestfwd
=tcp
:10.0.2.100:1234-tcp
:10.10.1.1:4321
3067 Or you can execute a command on every TCP connection established
3068 by the guest
, so that QEMU behaves similar to an inetd process
3069 for that virtual server
:
3073 # call
"netcat 10.10.1.1 4321" on every TCP connection to
10.0.2.100:1234
3074 # and connect the TCP stream to its stdin
/stdout
3075 |qemu_system|
-nic
'user,id=n1,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'
3077 ``
-netdev tap
,id
=id
[,fd
=h
][,ifname
=name
][,script
=file
][,downscript
=dfile
][,br
=bridge
][,helper
=helper
]``
3078 Configure a host TAP network backend with ID id
.
3080 Use the network script file to configure it and the network script
3081 dfile to deconfigure it
. If name is not provided
, the OS
3082 automatically provides one
. The
default network configure script is
3083 ``
/etc
/qemu
-ifup`` and the
default network deconfigure script is
3084 ``
/etc
/qemu
-ifdown``
. Use ``script
=no`` or ``downscript
=no`` to
3085 disable script execution
.
3087 If running QEMU as an unprivileged user
, use the network helper
3088 to configure the TAP
interface and attach it to the bridge
.
3089 The
default network helper executable is
3090 ``
/path
/to
/qemu
-bridge
-helper`` and the
default bridge device is
3093 ``fd``\
=h can be used to specify the handle of an already opened
3100 #launch a QEMU instance with the
default network script
3101 |qemu_system| linux
.img
-nic tap
3105 #launch a QEMU instance with two NICs
, each one connected
3107 |qemu_system| linux
.img
\\
3108 -netdev tap
,id
=nd0
,ifname
=tap0
-device e1000
,netdev
=nd0
\\
3109 -netdev tap
,id
=nd1
,ifname
=tap1
-device rtl8139
,netdev
=nd1
3113 #launch a QEMU instance with the
default network helper to
3114 #connect a TAP device to bridge br0
3115 |qemu_system| linux
.img
-device virtio
-net
-pci
,netdev
=n1
\\
3116 -netdev tap
,id
=n1
,"helper=/path/to/qemu-bridge-helper"
3118 ``
-netdev bridge
,id
=id
[,br
=bridge
][,helper
=helper
]``
3119 Connect a host TAP network
interface to a host bridge device
.
3121 Use the network helper helper to configure the TAP
interface and
3122 attach it to the bridge
. The
default network helper executable is
3123 ``
/path
/to
/qemu
-bridge
-helper`` and the
default bridge device is
3130 #launch a QEMU instance with the
default network helper to
3131 #connect a TAP device to bridge br0
3132 |qemu_system| linux
.img
-netdev bridge
,id
=n1
-device virtio
-net
,netdev
=n1
3136 #launch a QEMU instance with the
default network helper to
3137 #connect a TAP device to bridge qemubr0
3138 |qemu_system| linux
.img
-netdev bridge
,br
=qemubr0
,id
=n1
-device virtio
-net
,netdev
=n1
3140 ``
-netdev socket
,id
=id
[,fd
=h
][,listen
=[host
]:port
][,connect
=host
:port
]``
3141 This host network backend can be used to connect the guest
's network
3142 to another QEMU virtual machine using a TCP socket connection. If
3143 ``listen`` is specified, QEMU waits for incoming connections on port
3144 (host is optional). ``connect`` is used to connect to another QEMU
3145 instance using the ``listen`` option. ``fd``\ =h specifies an
3146 already opened TCP socket.
3152 # launch a first QEMU instance
3153 |qemu_system| linux.img \\
3154 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \\
3155 -netdev socket,id=n1,listen=:1234
3156 # connect the network of this instance to the network of the first instance
3157 |qemu_system| linux.img \\
3158 -device e1000,netdev=n2,mac=52:54:00:12:34:57 \\
3159 -netdev socket,id=n2,connect=127.0.0.1:1234
3161 ``-netdev socket,id=id[,fd=h][,mcast=maddr:port[,localaddr=addr]]``
3162 Configure a socket host network backend to share the guest's network
3163 traffic with another QEMU virtual machines
using a UDP multicast
3164 socket
, effectively making a bus
for every QEMU with same multicast
3165 address maddr and port
. NOTES
:
3167 1. Several QEMU can be running on different hosts and share same bus
3168 (assuming correct multicast setup
for these hosts
).
3170 2. mcast support is compatible with User Mode
Linux (argument
3171 ``ethN
=mcast``
), see http
://user-mode-linux.sf.net.
3173 3. Use ``fd
=h`` to specify an already opened UDP multicast socket
.
3179 # launch one QEMU instance
3180 |qemu_system| linux
.img
\\
3181 -device e1000
,netdev
=n1
,mac
=52:54:00:12:34:56 \\
3182 -netdev socket
,id
=n1
,mcast
=230.0.0.1:1234
3183 # launch another QEMU instance on same
"bus"
3184 |qemu_system| linux
.img
\\
3185 -device e1000
,netdev
=n2
,mac
=52:54:00:12:34:57 \\
3186 -netdev socket
,id
=n2
,mcast
=230.0.0.1:1234
3187 # launch yet another QEMU instance on same
"bus"
3188 |qemu_system| linux
.img
\\
3189 -device e1000
,netdev
=n3
,mac
=52:54:00:12:34:58 \\
3190 -netdev socket
,id
=n3
,mcast
=230.0.0.1:1234
3192 Example (User Mode Linux compat
.):
3196 # launch QEMU
instance (note mcast address selected is UML
's default)
3197 |qemu_system| linux.img \\
3198 -device e1000,netdev=n1,mac=52:54:00:12:34:56 \\
3199 -netdev socket,id=n1,mcast=239.192.168.1:1102
3201 /path/to/linux ubd0=/path/to/root_fs eth0=mcast
3203 Example (send packets from host's
1.2.3.4):
3207 |qemu_system| linux
.img
\\
3208 -device e1000
,netdev
=n1
,mac
=52:54:00:12:34:56 \\
3209 -netdev socket
,id
=n1
,mcast
=239.192.168.1:1102,localaddr
=1.2.3.4
3211 ``
-netdev l2tpv3
,id
=id
,src
=srcaddr
,dst
=dstaddr
[,srcport
=srcport
][,dstport
=dstport
],txsession
=txsession
[,rxsession
=rxsession
][,ipv6
=on|off
][,udp
=on|off
][,cookie64
][,counter
][,pincounter
][,txcookie
=txcookie
][,rxcookie
=rxcookie
][,offset
=offset
]``
3212 Configure a L2TPv3 pseudowire host network backend
. L2TPv3 (RFC3931
)
3213 is a popular protocol to transport
Ethernet (and other Layer
2) data
3214 frames between two systems
. It is present
in routers
, firewalls and
3215 the Linux
kernel (from version
3.3 onwards
).
3217 This transport allows a VM to communicate to another VM
, router or
3221 source
address (mandatory
)
3224 destination
address (mandatory
)
3227 select udp
encapsulation (default is ip
).
3233 destination udp port
.
3236 force v6
, otherwise defaults to v4
.
3238 ``rxcookie
=rxcookie``
; \ ``txcookie
=txcookie``
3239 Cookies are a weak form of security
in the l2tpv3 specification
.
3240 Their
function is mostly to prevent misconfiguration
. By
default
3244 Set cookie size to
64 bit instead of the
default 32
3247 Force a
'cut-down' L2TPv3 with no counter as
in
3248 draft
-mkonstan
-l2tpext
-keyed
-ipv6
-tunnel
-00
3251 Work around broken counter handling
in peer
. This may also help
3252 on networks which have packet reorder
.
3255 Add an extra offset between header and data
3257 For example
, to attach a VM running on host
4.3.2.1 via L2TPv3 to
3258 the bridge br
-lan on the remote Linux host
1.2.3.4:
3262 # Setup tunnel on linux host
using raw ip as encapsulation
3264 ip l2tp add tunnel remote
4.3.2.1 local
1.2.3.4 tunnel_id
1 peer_tunnel_id
1 \\
3265 encap udp udp_sport
16384 udp_dport
16384
3266 ip l2tp add session tunnel_id
1 name vmtunnel0 session_id
\\
3267 0xFFFFFFFF peer_session_id
0xFFFFFFFF
3268 ifconfig vmtunnel0 mtu
1500
3269 ifconfig vmtunnel0 up
3270 brctl addif br
-lan vmtunnel0
3274 # launch QEMU instance
- if your network has reorder or is very lossy add
,pincounter
3276 |qemu_system| linux
.img
-device e1000
,netdev
=n1
\\
3277 -netdev l2tpv3
,id
=n1
,src
=4.2.3.1,dst
=1.2.3.4,udp
,srcport
=16384,dstport
=16384,rxsession
=0xffffffff,txsession
=0xffffffff,counter
3279 ``
-netdev vde
,id
=id
[,sock
=socketpath
][,port
=n
][,group
=groupname
][,mode
=octalmode
]``
3280 Configure VDE backend to connect to PORT n of a vde
switch running
3281 on host and listening
for incoming connections on socketpath
. Use
3282 GROUP groupname and MODE octalmode to change
default ownership and
3283 permissions
for communication port
. This option is only available
if
3284 QEMU has been compiled with vde support enabled
.
3291 vde_switch
-F
-sock
/tmp
/myswitch
3292 # launch QEMU instance
3293 |qemu_system| linux
.img
-nic vde
,sock
=/tmp
/myswitch
3295 ``
-netdev vhost
-user
,chardev
=id
[,vhostforce
=on|off
][,queues
=n
]``
3296 Establish a vhost
-user netdev
, backed by a chardev id
. The chardev
3297 should be a unix domain socket backed one
. The vhost
-user uses a
3298 specifically defined protocol to pass vhost ioctl replacement
3299 messages to an application on the other end of the socket
. On
3300 non
-MSIX guests
, the feature can be forced with vhostforce
. Use
3301 'queues=n' to specify the number of queues to be created
for
3302 multiqueue vhost
-user
.
3308 qemu
-m
512 -object memory
-backend
-file
,id
=mem
,size
=512M
,mem
-path
=/hugetlbfs
,share
=on \
3309 -numa node
,memdev
=mem \
3310 -chardev socket
,id
=chr0
,path
=/path
/to
/socket \
3311 -netdev type
=vhost
-user
,id
=net0
,chardev
=chr0 \
3312 -device virtio
-net
-pci
,netdev
=net0
3314 ``
-netdev vhost
-vdpa
[,vhostdev
=/path
/to
/dev
][,vhostfd
=h
]``
3315 Establish a vhost
-vdpa netdev
.
3317 vDPA device is a device that uses a datapath which complies with
3318 the virtio specifications with a vendor specific control path
.
3319 vDPA devices can be both physically located on the hardware or
3320 emulated by software
.
3322 ``
-netdev hubport
,id
=id
,hubid
=hubid
[,netdev
=nd
]``
3323 Create a hub port on the emulated hub with ID hubid
.
3325 The hubport netdev lets you connect a NIC to a QEMU emulated hub
3326 instead of a single netdev
. Alternatively
, you can also connect the
3327 hubport to another netdev with ID nd by
using the ``netdev
=nd``
3330 ``
-net nic
[,netdev
=nd
][,macaddr
=mac
][,model
=type
] [,name
=name
][,addr
=addr
][,vectors
=v
]``
3331 Legacy option to configure or create an on
-board (or machine
3332 default) Network Interface
Card(NIC
) and connect it either to the
3333 emulated hub with ID
0 (i
.e
. the
default hub
), or to the netdev nd
.
3334 If model is omitted
, then the
default NIC model associated with the
3335 machine type is used
. Note that the
default NIC model may change
in
3336 future QEMU releases
, so it is highly recommended to always specify
3337 a model
. Optionally
, the MAC address can be changed to mac
, the
3338 device address set to
addr (PCI cards only
), and a name can be
3339 assigned
for use
in monitor commands
. Optionally
, for PCI cards
, you
3340 can specify the number v of MSI
-X vectors that the card should have
;
3341 this option currently only affects virtio cards
; set v
= 0 to
3342 disable MSI
-X
. If no ``
-net`` option is specified
, a single NIC is
3343 created
. QEMU can emulate several different models of network card
.
3344 Use ``
-net nic
,model
=help``
for a list of available devices
for your
3347 ``
-net user|tap|bridge|socket|l2tpv3|vde
[,...][,name
=name
]``
3348 Configure a host network
backend (with the options corresponding to
3349 the same ``
-netdev`` option
) and connect it to the emulated hub
0
3350 (the
default hub
). Use name to specify the name of the hub port
.
3355 DEFHEADING(Character device options
:)
3357 DEF("chardev", HAS_ARG
, QEMU_OPTION_chardev
,
3359 "-chardev null,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3360 "-chardev socket,id=id[,host=host],port=port[,to=to][,ipv4=on|off][,ipv6=on|off][,nodelay=on|off]\n"
3361 " [,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect=seconds][,mux=on|off]\n"
3362 " [,logfile=PATH][,logappend=on|off][,tls-creds=ID][,tls-authz=ID] (tcp)\n"
3363 "-chardev socket,id=id,path=path[,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect=seconds]\n"
3364 " [,mux=on|off][,logfile=PATH][,logappend=on|off][,abstract=on|off][,tight=on|off] (unix)\n"
3365 "-chardev udp,id=id[,host=host],port=port[,localaddr=localaddr]\n"
3366 " [,localport=localport][,ipv4=on|off][,ipv6=on|off][,mux=on|off]\n"
3367 " [,logfile=PATH][,logappend=on|off]\n"
3368 "-chardev msmouse,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3369 "-chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]\n"
3370 " [,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3371 "-chardev ringbuf,id=id[,size=size][,logfile=PATH][,logappend=on|off]\n"
3372 "-chardev file,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3373 "-chardev pipe,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3375 "-chardev console,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3376 "-chardev serial,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3378 "-chardev pty,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3379 "-chardev stdio,id=id[,mux=on|off][,signal=on|off][,logfile=PATH][,logappend=on|off]\n"
3381 #ifdef CONFIG_BRLAPI
3382 "-chardev braille,id=id[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3384 #
if defined(__linux__
) ||
defined(__sun__
) ||
defined(__FreeBSD__
) \
3385 ||
defined(__NetBSD__
) ||
defined(__OpenBSD__
) ||
defined(__DragonFly__
)
3386 "-chardev serial,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3387 "-chardev tty,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3389 #
if defined(__linux__
) ||
defined(__FreeBSD__
) ||
defined(__DragonFly__
)
3390 "-chardev parallel,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3391 "-chardev parport,id=id,path=path[,mux=on|off][,logfile=PATH][,logappend=on|off]\n"
3393 #
if defined(CONFIG_SPICE
)
3394 "-chardev spicevmc,id=id,name=name[,debug=debug][,logfile=PATH][,logappend=on|off]\n"
3395 "-chardev spiceport,id=id,name=name[,debug=debug][,logfile=PATH][,logappend=on|off]\n"
3401 The general form of a character device option is
:
3403 ``
-chardev backend
,id
=id
[,mux
=on|off
][,options
]``
3404 Backend is one of
: ``
null``
, ``socket``
, ``udp``
, ``msmouse``
,
3405 ``vc``
, ``ringbuf``
, ``file``
, ``pipe``
, ``console``
, ``serial``
,
3406 ``pty``
, ``stdio``
, ``braille``
, ``tty``
, ``parallel``
, ``parport``
,
3407 ``spicevmc``
, ``spiceport``
. The specific backend will determine the
3410 Use ``
-chardev help`` to print all available chardev backend types
.
3412 All devices must have an id
, which can be any string up to
127
3413 characters long
. It is used to uniquely identify
this device
in
3414 other command line directives
.
3416 A character device may be used
in multiplexing mode by multiple
3417 front
-ends
. Specify ``mux
=on`` to enable
this mode
. A multiplexer is
3418 a
"1:N" device
, and
here the
"1" end is your specified chardev
3419 backend
, and the
"N" end is the various parts of QEMU that can talk
3420 to a chardev
. If you create a chardev with ``id
=myid`` and
3421 ``mux
=on``
, QEMU will create a multiplexer with your specified ID
,
3422 and you can then configure multiple front ends to use that chardev
3423 ID
for their input
/output
. Up to four different front ends can be
3424 connected to a single multiplexed chardev
. (Without multiplexing
3425 enabled
, a chardev can only be used by a single front end
.) For
3426 instance you could use
this to allow a single stdio chardev to be
3427 used by two serial ports and the QEMU monitor
:
3431 -chardev stdio
,mux
=on
,id
=char0 \
3432 -mon chardev
=char0
,mode
=readline \
3433 -serial chardev
:char0 \
3434 -serial chardev
:char0
3436 You can have more than one multiplexer
in a system configuration
;
3437 for instance you could have a TCP port multiplexed between UART
0
3438 and UART
1, and stdio multiplexed between the QEMU monitor and a
3443 -chardev stdio
,mux
=on
,id
=char0 \
3444 -mon chardev
=char0
,mode
=readline \
3445 -parallel chardev
:char0 \
3446 -chardev tcp
,...,mux
=on
,id
=char1 \
3447 -serial chardev
:char1 \
3448 -serial chardev
:char1
3450 When you
're using a multiplexed character device, some escape
3451 sequences are interpreted in the input. See the chapter about
3452 :ref:`keys in the character backend multiplexer` in the
3453 System Emulation Users Guide for more details.
3455 Note that some other command line options may implicitly create
3456 multiplexed character backends; for instance ``-serial mon:stdio``
3457 creates a multiplexed stdio backend connected to the serial port and
3458 the QEMU monitor, and ``-nographic`` also multiplexes the console
3459 and the monitor to stdio.
3461 There is currently no support for multiplexing in the other
3462 direction (where a single QEMU front end takes input and output from
3465 Every backend supports the ``logfile`` option, which supplies the
3466 path to a file to record all data transmitted via the backend. The
3467 ``logappend`` option controls whether the log file will be truncated
3468 or appended to when opened.
3470 The available backends are:
3472 ``-chardev null,id=id``
3473 A void device. This device will not emit any data, and will drop any
3474 data it receives. The null backend does not take any options.
3476 ``-chardev socket,id=id[,TCP options or unix options][,server=on|off][,wait=on|off][,telnet=on|off][,websocket=on|off][,reconnect=seconds][,tls-creds=id][,tls-authz=id]``
3477 Create a two-way stream socket, which can be either a TCP or a unix
3478 socket. A unix socket will be created if ``path`` is specified.
3479 Behaviour is undefined if TCP options are specified for a unix
3482 ``server=on|off`` specifies that the socket shall be a listening socket.
3484 ``wait=on|off`` specifies that QEMU should not block waiting for a client
3485 to connect to a listening socket.
3487 ``telnet=on|off`` specifies that traffic on the socket should interpret
3488 telnet escape sequences.
3490 ``websocket=on|off`` specifies that the socket uses WebSocket protocol for
3493 ``reconnect`` sets the timeout for reconnecting on non-server
3494 sockets when the remote end goes away. qemu will delay this many
3495 seconds and then attempt to reconnect. Zero disables reconnecting,
3498 ``tls-creds`` requests enablement of the TLS protocol for
3499 encryption, and specifies the id of the TLS credentials to use for
3500 the handshake. The credentials must be previously created with the
3501 ``-object tls-creds`` argument.
3503 ``tls-auth`` provides the ID of the QAuthZ authorization object
3504 against which the client's x509 distinguished name will be
3505 validated
. This object is only resolved at time of use
, so can be
3506 deleted and recreated on the fly
while the chardev server is active
.
3507 If missing
, it will
default to denying access
.
3509 TCP and unix socket options are given below
:
3511 ``TCP options
: port
=port
[,host
=host
][,to
=to
][,ipv4
=on|off
][,ipv6
=on|off
][,nodelay
=on|off
]``
3512 ``host``
for a listening socket specifies the local address to
3513 be bound
. For a connecting socket species the remote host to
3514 connect to
. ``host`` is optional
for listening sockets
. If not
3515 specified it defaults to ``
0.0.0.0``
.
3517 ``port``
for a listening socket specifies the local port to be
3518 bound
. For a connecting socket specifies the port on the remote
3519 host to connect to
. ``port`` can be given as either a port
3520 number or a service name
. ``port`` is required
.
3522 ``to`` is only relevant to listening sockets
. If it is
3523 specified
, and ``port`` cannot be bound
, QEMU will attempt to
3524 bind to subsequent ports up to and including ``to`` until it
3525 succeeds
. ``to`` must be specified as a port number
.
3527 ``ipv4
=on|off`` and ``ipv6
=on|off`` specify that either IPv4
3528 or IPv6 must be used
. If neither is specified the socket may
3529 use either protocol
.
3531 ``nodelay
=on|off`` disables the Nagle algorithm
.
3533 ``unix options
: path
=path
[,abstract
=on|off
][,tight
=on|off
]``
3534 ``path`` specifies the local path of the unix socket
. ``path``
3536 ``abstract
=on|off`` specifies the use of the abstract socket namespace
,
3537 rather than the filesystem
. Optional
, defaults to
false.
3538 ``tight
=on|off`` sets the socket length of abstract sockets to their minimum
,
3539 rather than the full sun_path length
. Optional
, defaults to
true.
3541 ``
-chardev udp
,id
=id
[,host
=host
],port
=port
[,localaddr
=localaddr
][,localport
=localport
][,ipv4
=on|off
][,ipv6
=on|off
]``
3542 Sends all traffic from the guest to a remote host over UDP
.
3544 ``host`` specifies the remote host to connect to
. If not specified
3545 it defaults to ``localhost``
.
3547 ``port`` specifies the port on the remote host to connect to
.
3548 ``port`` is required
.
3550 ``localaddr`` specifies the local address to bind to
. If not
3551 specified it defaults to ``
0.0.0.0``
.
3553 ``localport`` specifies the local port to bind to
. If not specified
3554 any available local port will be used
.
3556 ``ipv4
=on|off`` and ``ipv6
=on|off`` specify that either IPv4 or IPv6 must be used
.
3557 If neither is specified the device may use either protocol
.
3559 ``
-chardev msmouse
,id
=id``
3560 Forward QEMU
's emulated msmouse events to the guest. ``msmouse``
3561 does not take any options.
3563 ``-chardev vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]``
3564 Connect to a QEMU text console. ``vc`` may optionally be given a
3567 ``width`` and ``height`` specify the width and height respectively
3568 of the console, in pixels.
3570 ``cols`` and ``rows`` specify that the console be sized to fit a
3571 text console with the given dimensions.
3573 ``-chardev ringbuf,id=id[,size=size]``
3574 Create a ring buffer with fixed size ``size``. size must be a power
3575 of two and defaults to ``64K``.
3577 ``-chardev file,id=id,path=path``
3578 Log all traffic received from the guest to a file.
3580 ``path`` specifies the path of the file to be opened. This file will
3581 be created if it does not already exist, and overwritten if it does.
3582 ``path`` is required.
3584 ``-chardev pipe,id=id,path=path``
3585 Create a two-way connection to the guest. The behaviour differs
3586 slightly between Windows hosts and other hosts:
3588 On Windows, a single duplex pipe will be created at
3591 On other hosts, 2 pipes will be created called ``path.in`` and
3592 ``path.out``. Data written to ``path.in`` will be received by the
3593 guest. Data written by the guest can be read from ``path.out``. QEMU
3594 will not create these fifos, and requires them to be present.
3596 ``path`` forms part of the pipe path as described above. ``path`` is
3599 ``-chardev console,id=id``
3600 Send traffic from the guest to QEMU's standard output
. ``console``
3601 does not take any options
.
3603 ``console`` is only available on Windows hosts
.
3605 ``
-chardev serial
,id
=id
,path
=path``
3606 Send traffic from the guest to a serial device on the host
.
3608 On Unix hosts serial will actually accept any tty device
, not only
3611 ``path`` specifies the name of the serial device to open
.
3613 ``
-chardev pty
,id
=id``
3614 Create a
new pseudo
-terminal on the host and connect to it
. ``pty``
3615 does not take any options
.
3617 ``pty`` is not available on Windows hosts
.
3619 ``
-chardev stdio
,id
=id
[,signal
=on|off
]``
3620 Connect to standard input and standard output of the QEMU process
.
3622 ``signal`` controls
if signals are enabled on the terminal
, that
3623 includes exiting QEMU with the key sequence Control
-c
. This option
3624 is enabled by
default, use ``signal
=off`` to disable it
.
3626 ``
-chardev braille
,id
=id``
3627 Connect to a local BrlAPI server
. ``braille`` does not take any
3630 ``
-chardev tty
,id
=id
,path
=path``
3631 ``tty`` is only available on Linux
, Sun
, FreeBSD
, NetBSD
, OpenBSD
3632 and DragonFlyBSD hosts
. It is an alias
for ``serial``
.
3634 ``path`` specifies the path to the tty
. ``path`` is required
.
3636 ``
-chardev parallel
,id
=id
,path
=path``
3638 ``
-chardev parport
,id
=id
,path
=path``
3639 ``parallel`` is only available on Linux
, FreeBSD and DragonFlyBSD
3642 Connect to a local parallel port
.
3644 ``path`` specifies the path to the parallel port device
. ``path`` is
3647 ``
-chardev spicevmc
,id
=id
,debug
=debug
,name
=name``
3648 ``spicevmc`` is only available when spice support is built
in.
3650 ``debug`` debug level
for spicevmc
3652 ``name`` name of spice channel to connect to
3654 Connect to a spice virtual machine channel
, such as vdiport
.
3656 ``
-chardev spiceport
,id
=id
,debug
=debug
,name
=name``
3657 ``spiceport`` is only available when spice support is built
in.
3659 ``debug`` debug level
for spicevmc
3661 ``name`` name of spice port to connect to
3663 Connect to a spice port
, allowing a Spice client to handle the
3664 traffic identified by a
name (preferably a fqdn
).
3670 DEFHEADING(TPM device options
:)
3672 DEF("tpmdev", HAS_ARG
, QEMU_OPTION_tpmdev
, \
3673 "-tpmdev passthrough,id=id[,path=path][,cancel-path=path]\n"
3674 " use path to provide path to a character device; default is /dev/tpm0\n"
3675 " use cancel-path to provide path to TPM's cancel sysfs entry; if\n"
3676 " not provided it will be searched for in /sys/class/misc/tpm?/device\n"
3677 "-tpmdev emulator,id=id,chardev=dev\n"
3678 " configure the TPM device using chardev backend\n",
3681 The general form of a TPM device option is
:
3683 ``
-tpmdev backend
,id
=id
[,options
]``
3684 The specific backend type will determine the applicable options
. The
3685 ``
-tpmdev`` option creates the TPM backend and requires a
3686 ``
-device`` option that specifies the TPM frontend
interface model
.
3688 Use ``
-tpmdev help`` to print all available TPM backend types
.
3690 The available backends are
:
3692 ``
-tpmdev passthrough
,id
=id
,path
=path
,cancel
-path
=cancel
-path``
3693 (Linux
-host only
) Enable access to the host
's TPM using the
3696 ``path`` specifies the path to the host's TPM device
, i
.e
., on a
3697 Linux host
this would be ``
/dev
/tpm0``
. ``path`` is optional and by
3698 default ``
/dev
/tpm0`` is used
.
3700 ``cancel
-path`` specifies the path to the host TPM device
's sysfs
3701 entry allowing for cancellation of an ongoing TPM command.
3702 ``cancel-path`` is optional and by default QEMU will search for the
3705 Some notes about using the host's TPM with the passthrough driver
:
3707 The TPM device accessed by the passthrough driver must not be used
3708 by any other application on the host
.
3710 Since the host
's firmware (BIOS/UEFI) has already initialized the
3711 TPM, the VM's
firmware (BIOS
/UEFI
) will not be able to initialize
3712 the TPM again and may therefore not show a TPM
-specific menu that
3713 would otherwise allow the user to configure the TPM
, e
.g
., allow the
3714 user to enable
/disable or activate
/deactivate the TPM
. Further
, if
3715 TPM ownership is released from within a VM then the host
's TPM will
3716 get disabled and deactivated. To enable and activate the TPM again
3717 afterwards, the host has to be rebooted and the user is required to
3718 enter the firmware's menu to enable and activate the TPM
. If the TPM
3719 is left disabled and
/or deactivated most TPM commands will fail
.
3721 To create a passthrough TPM use the following two options
:
3725 -tpmdev passthrough
,id
=tpm0
-device tpm
-tis
,tpmdev
=tpm0
3727 Note that the ``
-tpmdev`` id is ``tpm0`` and is referenced by
3728 ``tpmdev
=tpm0``
in the device option
.
3730 ``
-tpmdev emulator
,id
=id
,chardev
=dev``
3731 (Linux
-host only
) Enable access to a TPM emulator
using Unix domain
3732 socket based chardev backend
.
3734 ``chardev`` specifies the unique ID of a character device backend
3735 that provides connection to the software TPM server
.
3737 To create a TPM emulator backend device with chardev socket backend
:
3741 -chardev socket
,id
=chrtpm
,path
=/tmp
/swtpm
-sock
-tpmdev emulator
,id
=tpm0
,chardev
=chrtpm
-device tpm
-tis
,tpmdev
=tpm0
3748 DEFHEADING(Boot Image or Kernel specific
:)
3750 There are broadly
4 ways you can boot a system with QEMU
.
3752 - specify a firmware and let it control finding a kernel
3753 - specify a firmware and pass a hint to the kernel to boot
3754 - direct kernel image boot
3755 - manually load files into the guest
's address space
3757 The third method is useful for quickly testing kernels but as there is
3758 no firmware to pass configuration information to the kernel the
3759 hardware must either be probeable, the kernel built for the exact
3760 configuration or passed some configuration data (e.g. a DTB blob)
3761 which tells the kernel what drivers it needs. This exact details are
3762 often hardware specific.
3764 The final method is the most generic way of loading images into the
3765 guest address space and used mostly for ``bare metal`` type
3766 development where the reset vectors of the processor are taken into
3773 For x86 machines and some other architectures ``-bios`` will generally
3774 do the right thing with whatever it is given. For other machines the
3775 more strict ``-pflash`` option needs an image that is sized for the
3776 flash device for the given machine type.
3778 Please see the :ref:`system-targets-ref` section of the manual for
3779 more detailed documentation.
3783 DEF("bios", HAS_ARG, QEMU_OPTION_bios, \
3784 "-bios file set the filename for the BIOS\n", QEMU_ARCH_ALL)
3787 Set the filename for the BIOS.
3790 DEF("pflash", HAS_ARG, QEMU_OPTION_pflash,
3791 "-pflash file use 'file
' as a parallel flash image\n", QEMU_ARCH_ALL)
3794 Use file as a parallel flash image.
3799 The kernel options were designed to work with Linux kernels although
3800 other things (like hypervisors) can be packaged up as a kernel
3801 executable image. The exact format of a executable image is usually
3802 architecture specific.
3804 The way in which the kernel is started (what address it is loaded at,
3805 what if any information is passed to it via CPU registers, the state
3806 of the hardware when it is started, and so on) is also architecture
3807 specific. Typically it follows the specification laid down by the
3808 Linux kernel for how kernels for that architecture must be started.
3812 DEF("kernel", HAS_ARG, QEMU_OPTION_kernel, \
3813 "-kernel bzImage use 'bzImage
' as kernel image\n", QEMU_ARCH_ALL)
3816 Use bzImage as kernel image. The kernel can be either a Linux kernel
3817 or in multiboot format.
3820 DEF("append", HAS_ARG, QEMU_OPTION_append, \
3821 "-append cmdline use 'cmdline
' as kernel command line\n", QEMU_ARCH_ALL)
3824 Use cmdline as kernel command line
3827 DEF("initrd", HAS_ARG, QEMU_OPTION_initrd, \
3828 "-initrd file use 'file
' as initial ram disk\n", QEMU_ARCH_ALL)
3831 Use file as initial ram disk.
3833 ``-initrd "file1 arg=foo,file2"``
3834 This syntax is only available with multiboot.
3836 Use file1 and file2 as modules and pass arg=foo as parameter to the
3840 DEF("dtb", HAS_ARG, QEMU_OPTION_dtb, \
3841 "-dtb file use 'file
' as device tree image\n", QEMU_ARCH_ALL)
3844 Use file as a device tree binary (dtb) image and pass it to the
3850 Finally you can also manually load images directly into the address
3851 space of the guest. This is most useful for developers who already
3852 know the layout of their guest and take care to ensure something sane
3853 will happen when the reset vector executes.
3855 The generic loader can be invoked by using the loader device:
3857 ``-device loader,addr=<addr>,data=<data>,data-len=<data-len>[,data-be=<data-be>][,cpu-num=<cpu-num>]``
3859 there is also the guest loader which operates in a similar way but
3860 tweaks the DTB so a hypervisor loaded via ``-kernel`` can find where
3863 ``-device guest-loader,addr=<addr>[,kernel=<path>,[bootargs=<arguments>]][,initrd=<path>]``
3869 DEFHEADING(Debug/Expert options:)
3871 DEF("compat", HAS_ARG, QEMU_OPTION_compat,
3872 "-compat [deprecated-input=accept|reject|crash][,deprecated-output=accept|hide]\n"
3873 " Policy for handling deprecated management interfaces\n"
3874 "-compat [unstable-input=accept|reject|crash][,unstable-output=accept|hide]\n"
3875 " Policy for handling unstable management interfaces\n",
3878 ``-compat [deprecated-input=@var{input-policy}][,deprecated-output=@var{output-policy}]``
3879 Set policy for handling deprecated management interfaces (experimental):
3881 ``deprecated-input=accept`` (default)
3882 Accept deprecated commands and arguments
3883 ``deprecated-input=reject``
3884 Reject deprecated commands and arguments
3885 ``deprecated-input=crash``
3886 Crash on deprecated commands and arguments
3887 ``deprecated-output=accept`` (default)
3888 Emit deprecated command results and events
3889 ``deprecated-output=hide``
3890 Suppress deprecated command results and events
3892 Limitation: covers only syntactic aspects of QMP.
3894 ``-compat [unstable-input=@var{input-policy}][,unstable-output=@var{output-policy}]``
3895 Set policy for handling unstable management interfaces (experimental):
3897 ``unstable-input=accept`` (default)
3898 Accept unstable commands and arguments
3899 ``unstable-input=reject``
3900 Reject unstable commands and arguments
3901 ``unstable-input=crash``
3902 Crash on unstable commands and arguments
3903 ``unstable-output=accept`` (default)
3904 Emit unstable command results and events
3905 ``unstable-output=hide``
3906 Suppress unstable command results and events
3908 Limitation: covers only syntactic aspects of QMP.
3911 DEF("fw_cfg", HAS_ARG, QEMU_OPTION_fwcfg,
3912 "-fw_cfg [name=]<name>,file=<file>\n"
3913 " add named fw_cfg entry with contents from file\n"
3914 "-fw_cfg [name=]<name>,string=<str>\n"
3915 " add named fw_cfg entry with contents from string\n",
3918 ``-fw_cfg [name=]name,file=file``
3919 Add named fw\_cfg entry with contents from file file.
3921 ``-fw_cfg [name=]name,string=str``
3922 Add named fw\_cfg entry with contents from string str.
3924 The terminating NUL character of the contents of str will not be
3925 included as part of the fw\_cfg item data. To insert contents with
3926 embedded NUL characters, you have to use the file parameter.
3928 The fw\_cfg entries are passed by QEMU through to the guest.
3934 -fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin
3936 creates an fw\_cfg entry named opt/com.mycompany/blob with contents
3937 from ./my\_blob.bin.
3940 DEF("serial", HAS_ARG, QEMU_OPTION_serial, \
3941 "-serial dev redirect the serial port to char device 'dev
'\n",
3945 Redirect the virtual serial port to host character device dev. The
3946 default device is ``vc`` in graphical mode and ``stdio`` in non
3949 This option can be used several times to simulate up to 4 serial
3952 Use ``-serial none`` to disable all serial ports.
3954 Available character devices are:
3957 Virtual console. Optionally, a width and height can be given in
3964 It is also possible to specify width or height in characters:
3971 [Linux only] Pseudo TTY (a new PTY is automatically allocated)
3974 No device is allocated.
3980 Use a named character device defined with the ``-chardev``
3984 [Linux only] Use host tty, e.g. ``/dev/ttyS0``. The host serial
3985 port parameters are set according to the emulated ones.
3988 [Linux only, parallel port only] Use host parallel port N.
3989 Currently SPP and EPP parallel port features can be used.
3992 Write output to filename. No character can be read.
3995 [Unix only] standard input/output
4001 [Windows only] Use host serial port n
4003 ``udp:[remote_host]:remote_port[@[src_ip]:src_port]``
4004 This implements UDP Net Console. When remote\_host or src\_ip
4005 are not specified they default to ``0.0.0.0``. When not using a
4006 specified src\_port a random port is automatically chosen.
4008 If you just want a simple readonly console you can use
4009 ``netcat`` or ``nc``, by starting QEMU with:
4010 ``-serial udp::4555`` and nc as: ``nc -u -l -p 4555``. Any time
4011 QEMU writes something to that port it will appear in the
4014 If you plan to send characters back via netconsole or you want
4015 to stop and start QEMU a lot of times, you should have QEMU use
4016 the same source port each time by using something like ``-serial
4017 udp::4555@:4556`` to QEMU. Another approach is to use a patched
4018 version of netcat which can listen to a TCP port and send and
4019 receive characters via udp. If you have a patched version of
4020 netcat which activates telnet remote echo and single char
4021 transfer, then you can use the following options to set up a
4022 netcat redirector to allow telnet on port 5555 to access the
4026 -serial udp::4555@:4556
4029 -u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T
4034 ``tcp:[host]:port[,server=on|off][,wait=on|off][,nodelay=on|off][,reconnect=seconds]``
4035 The TCP Net Console has two modes of operation. It can send the
4036 serial I/O to a location or wait for a connection from a
4037 location. By default the TCP Net Console is sent to host at the
4038 port. If you use the ``server=on`` option QEMU will wait for a client
4039 socket application to connect to the port before continuing,
4040 unless the ``wait=on|off`` option was specified. The ``nodelay=on|off``
4041 option disables the Nagle buffering algorithm. The ``reconnect=on``
4042 option only applies if ``server=no`` is set, if the connection goes
4043 down it will attempt to reconnect at the given interval. If host
4044 is omitted, 0.0.0.0 is assumed. Only one TCP connection at a
4045 time is accepted. You can use ``telnet=on`` to connect to the
4046 corresponding character device.
4048 ``Example to send tcp console to 192.168.0.2 port 4444``
4049 -serial tcp:192.168.0.2:4444
4051 ``Example to listen and wait on port 4444 for connection``
4052 -serial tcp::4444,server=on
4054 ``Example to not wait and listen on ip 192.168.0.100 port 4444``
4055 -serial tcp:192.168.0.100:4444,server=on,wait=off
4057 ``telnet:host:port[,server=on|off][,wait=on|off][,nodelay=on|off]``
4058 The telnet protocol is used instead of raw tcp sockets. The
4059 options work the same as if you had specified ``-serial tcp``.
4060 The difference is that the port acts like a telnet server or
4061 client using telnet option negotiation. This will also allow you
4062 to send the MAGIC\_SYSRQ sequence if you use a telnet that
4063 supports sending the break sequence. Typically in unix telnet
4064 you do it with Control-] and then type "send break" followed by
4065 pressing the enter key.
4067 ``websocket:host:port,server=on[,wait=on|off][,nodelay=on|off]``
4068 The WebSocket protocol is used instead of raw tcp socket. The
4069 port acts as a WebSocket server. Client mode is not supported.
4071 ``unix:path[,server=on|off][,wait=on|off][,reconnect=seconds]``
4072 A unix domain socket is used instead of a tcp socket. The option
4073 works the same as if you had specified ``-serial tcp`` except
4074 the unix domain socket path is used for connections.
4077 This is a special option to allow the monitor to be multiplexed
4078 onto another serial port. The monitor is accessed with key
4079 sequence of Control-a and then pressing c. dev\_string should be
4080 any one of the serial devices specified above. An example to
4081 multiplex the monitor onto a telnet server listening on port
4084 ``-serial mon:telnet::4444,server=on,wait=off``
4086 When the monitor is multiplexed to stdio in this way, Ctrl+C
4087 will not terminate QEMU any more but will be passed to the guest
4091 Braille device. This will use BrlAPI to display the braille
4092 output on a real or fake device.
4095 Three button serial mouse. Configure the guest to use Microsoft
4099 DEF("parallel", HAS_ARG, QEMU_OPTION_parallel, \
4100 "-parallel dev redirect the parallel port to char device 'dev
'\n",
4104 Redirect the virtual parallel port to host device dev (same devices
4105 as the serial port). On Linux hosts, ``/dev/parportN`` can be used
4106 to use hardware devices connected on the corresponding host parallel
4109 This option can be used several times to simulate up to 3 parallel
4112 Use ``-parallel none`` to disable all parallel ports.
4115 DEF("monitor", HAS_ARG, QEMU_OPTION_monitor, \
4116 "-monitor dev redirect the monitor to char device 'dev
'\n",
4120 Redirect the monitor to host device dev (same devices as the serial
4121 port). The default device is ``vc`` in graphical mode and ``stdio``
4122 in non graphical mode. Use ``-monitor none`` to disable the default
4125 DEF("qmp", HAS_ARG, QEMU_OPTION_qmp, \
4126 "-qmp dev like -monitor but opens in 'control
' mode\n",
4130 Like -monitor but opens in 'control
' mode.
4132 DEF("qmp-pretty", HAS_ARG, QEMU_OPTION_qmp_pretty, \
4133 "-qmp-pretty dev like -qmp but uses pretty JSON formatting\n",
4137 Like -qmp but uses pretty JSON formatting.
4140 DEF("mon", HAS_ARG, QEMU_OPTION_mon, \
4141 "-mon [chardev=]name[,mode=readline|control][,pretty[=on|off]]\n", QEMU_ARCH_ALL)
4143 ``-mon [chardev=]name[,mode=readline|control][,pretty[=on|off]]``
4144 Setup monitor on chardev name. ``mode=control`` configures
4145 a QMP monitor (a JSON RPC-style protocol) and it is not the
4146 same as HMP, the human monitor that has a "(qemu)" prompt.
4147 ``pretty`` is only valid when ``mode=control``,
4148 turning on JSON pretty printing to ease
4149 human reading and debugging.
4152 DEF("debugcon", HAS_ARG, QEMU_OPTION_debugcon, \
4153 "-debugcon dev redirect the debug console to char device 'dev
'\n",
4157 Redirect the debug console to host device dev (same devices as the
4158 serial port). The debug console is an I/O port which is typically
4159 port 0xe9; writing to that I/O port sends output to this device. The
4160 default device is ``vc`` in graphical mode and ``stdio`` in non
4164 DEF("pidfile", HAS_ARG, QEMU_OPTION_pidfile, \
4165 "-pidfile file write PID to 'file
'\n", QEMU_ARCH_ALL)
4168 Store the QEMU process PID in file. It is useful if you launch QEMU
4172 DEF("singlestep", 0, QEMU_OPTION_singlestep, \
4173 "-singlestep always run in singlestep mode\n", QEMU_ARCH_ALL)
4176 Run the emulation in single step mode.
4179 DEF("preconfig", 0, QEMU_OPTION_preconfig, \
4180 "--preconfig pause QEMU before machine is initialized (experimental)\n",
4184 Pause QEMU for interactive configuration before the machine is
4185 created, which allows querying and configuring properties that will
4186 affect machine initialization. Use QMP command 'x
-exit
-preconfig
' to
4187 exit the preconfig state and move to the next state (i.e. run guest
4188 if -S isn't used or pause the second time
if -S is used
). This
4189 option is experimental
.
4192 DEF("S", 0, QEMU_OPTION_S
, \
4193 "-S freeze CPU at startup (use 'c' to start execution)\n",
4197 Do not start CPU at
startup (you must type
'c' in the monitor
).
4200 DEF("overcommit", HAS_ARG
, QEMU_OPTION_overcommit
,
4201 "-overcommit [mem-lock=on|off][cpu-pm=on|off]\n"
4202 " run qemu with overcommit hints\n"
4203 " mem-lock=on|off controls memory lock support (default: off)\n"
4204 " cpu-pm=on|off controls cpu power management (default: off)\n",
4207 ``
-overcommit mem
-lock
=on|off``
4209 ``
-overcommit cpu
-pm
=on|off``
4210 Run qemu with hints about host resource overcommit
. The
default is
4211 to assume that host overcommits all resources
.
4213 Locking qemu and guest memory can be enabled via ``mem
-lock
=on``
4214 (disabled by
default). This works when host memory is not
4215 overcommitted and reduces the worst
-case latency
for guest
.
4217 Guest ability to manage power state of host
cpus (increasing latency
4218 for other processes on the same host cpu
, but decreasing latency
for
4219 guest
) can be enabled via ``cpu
-pm
=on``
(disabled by
default). This
4220 works best when host CPU is not overcommitted
. When used
, host
4221 estimates of CPU cycle and power utilization will be incorrect
, not
4222 taking into account guest idle time
.
4225 DEF("gdb", HAS_ARG
, QEMU_OPTION_gdb
, \
4226 "-gdb dev accept gdb connection on 'dev'. (QEMU defaults to starting\n"
4227 " the guest without waiting for gdb to connect; use -S too\n"
4228 " if you want it to not start execution.)\n",
4232 Accept a gdb connection on device
dev (see the
:ref
:`GDB usage` chapter
4233 in the System Emulation Users Guide
). Note that
this option does not pause QEMU
4234 execution
-- if you want QEMU to not start the guest until you
4235 connect with gdb and issue a ``
continue`` command
, you will need to
4236 also pass the ``
-S`` option to QEMU
.
4238 The most usual configuration is to listen on a local TCP socket
::
4242 but you can specify other backends
; UDP
, pseudo TTY
, or even stdio
4243 are all reasonable use cases
. For example
, a stdio connection
4244 allows you to start QEMU from within gdb and establish the
4245 connection via a pipe
:
4249 (gdb
) target remote | exec |qemu_system|
-gdb stdio
...
4252 DEF("s", 0, QEMU_OPTION_s
, \
4253 "-s shorthand for -gdb tcp::" DEFAULT_GDBSTUB_PORT
"\n",
4257 Shorthand
for -gdb tcp
::1234, i
.e
. open a gdbserver on TCP port
1234
4258 (see the
:ref
:`GDB usage` chapter
in the System Emulation Users Guide
).
4261 DEF("d", HAS_ARG
, QEMU_OPTION_d
, \
4262 "-d item1,... enable logging of specified items (use '-d help' for a list of log items)\n",
4266 Enable logging of specified items
. Use
'-d help' for a list of log
4270 DEF("D", HAS_ARG
, QEMU_OPTION_D
, \
4271 "-D logfile output log to logfile (default stderr)\n",
4275 Output log
in logfile instead of to stderr
4278 DEF("dfilter", HAS_ARG
, QEMU_OPTION_DFILTER
, \
4279 "-dfilter range,.. filter debug output to range of addresses (useful for -d cpu,exec,etc..)\n",
4282 ``
-dfilter range1
[,...]``
4283 Filter debug output to that relevant to a range of target addresses
.
4284 The filter spec can be either start
+size
, start
-size or start
..end
4285 where start end and size are the addresses and sizes required
. For
4290 -dfilter
0x8000..0x8fff
,0xffffffc000080000+0x200,0xffffffc000060000-0x1000
4292 Will dump output
for any code
in the
0x1000 sized block starting at
4293 0x8000 and the
0x200 sized block starting at
0xffffffc000080000 and
4294 another
0x1000 sized block starting at
0xffffffc00005f000.
4297 DEF("seed", HAS_ARG
, QEMU_OPTION_seed
, \
4298 "-seed number seed the pseudo-random number generator\n",
4302 Force the guest to use a deterministic pseudo
-random number
4303 generator
, seeded with number
. This does not affect crypto routines
4307 DEF("L", HAS_ARG
, QEMU_OPTION_L
, \
4308 "-L path set the directory for the BIOS, VGA BIOS and keymaps\n",
4312 Set the directory
for the BIOS
, VGA BIOS and keymaps
.
4314 To list all the data directories
, use ``
-L help``
.
4317 DEF("enable-kvm", 0, QEMU_OPTION_enable_kvm
, \
4318 "-enable-kvm enable KVM full virtualization support\n",
4319 QEMU_ARCH_ARM | QEMU_ARCH_I386 | QEMU_ARCH_MIPS | QEMU_ARCH_PPC |
4320 QEMU_ARCH_RISCV | QEMU_ARCH_S390X
)
4323 Enable KVM full virtualization support
. This option is only
4324 available
if KVM support is enabled when compiling
.
4327 DEF("xen-domid", HAS_ARG
, QEMU_OPTION_xen_domid
,
4328 "-xen-domid id specify xen guest domain id\n",
4329 QEMU_ARCH_ARM | QEMU_ARCH_I386
)
4330 DEF("xen-attach", 0, QEMU_OPTION_xen_attach
,
4331 "-xen-attach attach to existing xen domain\n"
4332 " libxl will use this when starting QEMU\n",
4333 QEMU_ARCH_ARM | QEMU_ARCH_I386
)
4334 DEF("xen-domid-restrict", 0, QEMU_OPTION_xen_domid_restrict
,
4335 "-xen-domid-restrict restrict set of available xen operations\n"
4336 " to specified domain id. (Does not affect\n"
4337 " xenpv machine type).\n",
4338 QEMU_ARCH_ARM | QEMU_ARCH_I386
)
4341 Specify xen guest domain
id (XEN only
).
4344 Attach to existing xen domain
. libxl will use
this when starting
4345 QEMU (XEN only
). Restrict set of available xen operations to
4346 specified domain
id (XEN only
).
4349 DEF("no-reboot", 0, QEMU_OPTION_no_reboot
, \
4350 "-no-reboot exit instead of rebooting\n", QEMU_ARCH_ALL
)
4353 Exit instead of rebooting
.
4356 DEF("no-shutdown", 0, QEMU_OPTION_no_shutdown
, \
4357 "-no-shutdown stop before shutdown\n", QEMU_ARCH_ALL
)
4360 Don
't exit QEMU on guest shutdown, but instead only stop the
4361 emulation. This allows for instance switching to monitor to commit
4362 changes to the disk image.
4365 DEF("action", HAS_ARG, QEMU_OPTION_action,
4366 "-action reboot=reset|shutdown\n"
4367 " action when guest reboots [default=reset]\n"
4368 "-action shutdown=poweroff|pause\n"
4369 " action when guest shuts down [default=poweroff]\n"
4370 "-action panic=pause|shutdown|exit-failure|none\n"
4371 " action when guest panics [default=shutdown]\n"
4372 "-action watchdog=reset|shutdown|poweroff|inject-nmi|pause|debug|none\n"
4373 " action when watchdog fires [default=reset]\n",
4376 ``-action event=action``
4377 The action parameter serves to modify QEMU's
default behavior when
4378 certain guest events occur
. It provides a generic method
for specifying the
4379 same behaviors that are modified by the ``
-no
-reboot`` and ``
-no
-shutdown``
4384 ``
-action panic
=none``
4385 ``
-action reboot
=shutdown
,shutdown
=pause``
4386 ``
-device i6300esb
-action watchdog
=pause``
4390 DEF("loadvm", HAS_ARG
, QEMU_OPTION_loadvm
, \
4391 "-loadvm [tag|id]\n" \
4392 " start right away with a saved state (loadvm in monitor)\n",
4396 Start right away with a saved
state (``loadvm``
in monitor
)
4400 DEF("daemonize", 0, QEMU_OPTION_daemonize
, \
4401 "-daemonize daemonize QEMU after initializing\n", QEMU_ARCH_ALL
)
4405 Daemonize the QEMU process after initialization
. QEMU will not
4406 detach from standard IO until it is ready to receive connections on
4407 any of its devices
. This option is a useful way
for external
4408 programs to launch QEMU without having to cope with initialization
4412 DEF("option-rom", HAS_ARG
, QEMU_OPTION_option_rom
, \
4413 "-option-rom rom load a file, rom, into the option ROM space\n",
4416 ``
-option
-rom file``
4417 Load the contents of file as an option ROM
. This option is useful to
4418 load things like EtherBoot
.
4421 DEF("rtc", HAS_ARG
, QEMU_OPTION_rtc
, \
4422 "-rtc [base=utc|localtime|<datetime>][,clock=host|rt|vm][,driftfix=none|slew]\n" \
4423 " set the RTC base and clock, enable drift fix for clock ticks (x86 only)\n",
4427 ``
-rtc
[base
=utc|localtime|datetime
][,clock
=host|rt|vm
][,driftfix
=none|slew
]``
4428 Specify ``base`` as ``utc`` or ``localtime`` to let the RTC start at
4429 the current UTC or local time
, respectively
. ``localtime`` is
4430 required
for correct date
in MS
-DOS or Windows
. To start at a
4431 specific point
in time
, provide datetime
in the format
4432 ``
2006-06-17T16
:01:21`` or ``
2006-06-17``
. The
default base is UTC
.
4434 By
default the RTC is driven by the host system time
. This allows
4435 using of the RTC as accurate reference clock inside the guest
,
4436 specifically
if the host time is smoothly following an accurate
4437 external reference clock
, e
.g
. via NTP
. If you want to isolate the
4438 guest time from the host
, you can set ``clock`` to ``rt`` instead
,
4439 which provides a host monotonic clock
if host support it
. To even
4440 prevent the RTC from progressing during suspension
, you can set
4441 ``clock`` to ``vm``
(virtual clock
). '\ ``clock=vm``\ ' is
4442 recommended especially
in icount mode
in order to preserve
4443 determinism
; however
, note that
in icount mode the speed of the
4444 virtual clock is variable and can
in general differ from the host
4447 Enable ``driftfix``
(i386 targets only
) if you experience time drift
4448 problems
, specifically with Windows
' ACPI HAL. This option will try
4449 to figure out how many timer interrupts were not processed by the
4450 Windows guest and will re-inject them.
4453 DEF("icount", HAS_ARG, QEMU_OPTION_icount, \
4454 "-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=<filename>[,rrsnapshot=<snapshot>]]\n" \
4455 " enable virtual instruction counter with 2^N clock ticks per\n" \
4456 " instruction, enable aligning the host and virtual clocks\n" \
4457 " or disable real time cpu sleeping, and optionally enable\n" \
4458 " record-and-replay mode\n", QEMU_ARCH_ALL)
4460 ``-icount [shift=N|auto][,align=on|off][,sleep=on|off][,rr=record|replay,rrfile=filename[,rrsnapshot=snapshot]]``
4461 Enable virtual instruction counter. The virtual cpu will execute one
4462 instruction every 2^N ns of virtual time. If ``auto`` is specified
4463 then the virtual cpu speed will be automatically adjusted to keep
4464 virtual time within a few seconds of real time.
4466 Note that while this option can give deterministic behavior, it does
4467 not provide cycle accurate emulation. Modern CPUs contain
4468 superscalar out of order cores with complex cache hierarchies. The
4469 number of instructions executed often has little or no correlation
4470 with actual performance.
4472 When the virtual cpu is sleeping, the virtual time will advance at
4473 default speed unless ``sleep=on`` is specified. With
4474 ``sleep=on``, the virtual time will jump to the next timer
4475 deadline instantly whenever the virtual cpu goes to sleep mode and
4476 will not advance if no timer is enabled. This behavior gives
4477 deterministic execution times from the guest point of view.
4478 The default if icount is enabled is ``sleep=off``.
4479 ``sleep=on`` cannot be used together with either ``shift=auto``
4482 ``align=on`` will activate the delay algorithm which will try to
4483 synchronise the host clock and the virtual clock. The goal is to
4484 have a guest running at the real frequency imposed by the shift
4485 option. Whenever the guest clock is behind the host clock and if
4486 ``align=on`` is specified then we print a message to the user to
4487 inform about the delay. Currently this option does not work when
4488 ``shift`` is ``auto``. Note: The sync algorithm will work for those
4489 shift values for which the guest clock runs ahead of the host clock.
4490 Typically this happens when the shift value is high (how high
4491 depends on the host machine). The default if icount is enabled
4494 When the ``rr`` option is specified deterministic record/replay is
4495 enabled. The ``rrfile=`` option must also be provided to
4496 specify the path to the replay log. In record mode data is written
4497 to this file, and in replay mode it is read back.
4498 If the ``rrsnapshot`` option is given then it specifies a VM snapshot
4499 name. In record mode, a new VM snapshot with the given name is created
4500 at the start of execution recording. In replay mode this option
4501 specifies the snapshot name used to load the initial VM state.
4504 DEF("watchdog-action", HAS_ARG, QEMU_OPTION_watchdog_action, \
4505 "-watchdog-action reset|shutdown|poweroff|inject-nmi|pause|debug|none\n" \
4506 " action when watchdog fires [default=reset]\n",
4509 ``-watchdog-action action``
4510 The action controls what QEMU will do when the watchdog timer
4511 expires. The default is ``reset`` (forcefully reset the guest).
4512 Other possible actions are: ``shutdown`` (attempt to gracefully
4513 shutdown the guest), ``poweroff`` (forcefully poweroff the guest),
4514 ``inject-nmi`` (inject a NMI into the guest), ``pause`` (pause the
4515 guest), ``debug`` (print a debug message and continue), or ``none``
4518 Note that the ``shutdown`` action requires that the guest responds
4519 to ACPI signals, which it may not be able to do in the sort of
4520 situations where the watchdog would have expired, and thus
4521 ``-watchdog-action shutdown`` is not recommended for production use.
4525 ``-device i6300esb -watchdog-action pause``
4529 DEF("echr", HAS_ARG, QEMU_OPTION_echr, \
4530 "-echr chr set terminal escape character instead of ctrl-a\n",
4533 ``-echr numeric_ascii_value``
4534 Change the escape character used for switching to the monitor when
4535 using monitor and serial sharing. The default is ``0x01`` when using
4536 the ``-nographic`` option. ``0x01`` is equal to pressing
4537 ``Control-a``. You can select a different character from the ascii
4538 control keys where 1 through 26 map to Control-a through Control-z.
4539 For instance you could use the either of the following to change the
4540 escape character to Control-t.
4542 ``-echr 0x14``; \ ``-echr 20``
4546 DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \
4547 "-incoming tcp:[host]:port[,to=maxport][,ipv4=on|off][,ipv6=on|off]\n" \
4548 "-incoming rdma:host:port[,ipv4=on|off][,ipv6=on|off]\n" \
4549 "-incoming unix:socketpath\n" \
4550 " prepare for incoming migration, listen on\n" \
4551 " specified protocol and socket address\n" \
4552 "-incoming fd:fd\n" \
4553 "-incoming exec:cmdline\n" \
4554 " accept incoming migration on given file descriptor\n" \
4555 " or from given external command\n" \
4556 "-incoming defer\n" \
4557 " wait for the URI to be specified via migrate_incoming\n",
4560 ``-incoming tcp:[host]:port[,to=maxport][,ipv4=on|off][,ipv6=on|off]``
4562 ``-incoming rdma:host:port[,ipv4=on|off][,ipv6=on|off]``
4563 Prepare for incoming migration, listen on a given tcp port.
4565 ``-incoming unix:socketpath``
4566 Prepare for incoming migration, listen on a given unix socket.
4569 Accept incoming migration from a given filedescriptor.
4571 ``-incoming exec:cmdline``
4572 Accept incoming migration as an output from specified external
4576 Wait for the URI to be specified via migrate\_incoming. The monitor
4577 can be used to change settings (such as migration parameters) prior
4578 to issuing the migrate\_incoming to allow the migration to begin.
4581 DEF("only-migratable", 0, QEMU_OPTION_only_migratable, \
4582 "-only-migratable allow only migratable devices\n", QEMU_ARCH_ALL)
4584 ``-only-migratable``
4585 Only allow migratable devices. Devices will not be allowed to enter
4586 an unmigratable state.
4589 DEF("nodefaults", 0, QEMU_OPTION_nodefaults, \
4590 "-nodefaults don't create
default devices
\n", QEMU_ARCH_ALL)
4593 Don't create default devices. Normally, QEMU sets the default
4594 devices like serial port, parallel port, virtual console, monitor
4595 device, VGA adapter, floppy and CD-ROM drive and others. The
4596 ``-nodefaults`` option will disable all those default devices.
4600 DEF("chroot
", HAS_ARG, QEMU_OPTION_chroot, \
4601 "-chroot dir chroot to dir just before starting the VM
\n",
4606 Immediately before starting guest execution, chroot to the specified
4607 directory. Especially useful in combination with -runas.
4611 DEF("runas
", HAS_ARG, QEMU_OPTION_runas, \
4612 "-runas user change to user id user just before starting the VM
\n" \
4613 " user can be numeric uid
:gid instead
\n",
4618 Immediately before starting guest execution, drop root privileges,
4619 switching to the specified user.
4622 DEF("prom
-env
", HAS_ARG, QEMU_OPTION_prom_env,
4623 "-prom
-env variable
=value
\n"
4624 " set OpenBIOS nvram variables
\n",
4625 QEMU_ARCH_PPC | QEMU_ARCH_SPARC)
4627 ``-prom-env variable=value``
4628 Set OpenBIOS nvram variable to given value (PPC, SPARC only).
4632 qemu-system-sparc -prom-env 'auto-boot?=false' \
4633 -prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
4637 qemu-system-ppc -prom-env 'auto-boot?=false' \
4638 -prom-env 'boot-device=hd:2,\yaboot' \
4639 -prom-env 'boot-args=conf=hd:2,\yaboot.conf'
4641 DEF("semihosting
", 0, QEMU_OPTION_semihosting,
4642 "-semihosting semihosting mode
\n",
4643 QEMU_ARCH_ARM | QEMU_ARCH_M68K | QEMU_ARCH_XTENSA |
4644 QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2 | QEMU_ARCH_RISCV)
4647 Enable semihosting mode (ARM, M68K, Xtensa, MIPS, Nios II, RISC-V only).
4649 Note that this allows guest direct access to the host filesystem, so
4650 should only be used with a trusted guest OS.
4652 See the -semihosting-config option documentation for further
4653 information about the facilities this enables.
4655 DEF("semihosting
-config
", HAS_ARG, QEMU_OPTION_semihosting_config,
4656 "-semihosting
-config
[enable
=on|off
][,target
=native|gdb|auto
][,chardev
=id
][,userspace
=on|off
][,arg
=str
[,...]]\n" \
4657 " semihosting configuration
\n",
4658 QEMU_ARCH_ARM | QEMU_ARCH_M68K | QEMU_ARCH_XTENSA |
4659 QEMU_ARCH_MIPS | QEMU_ARCH_NIOS2 | QEMU_ARCH_RISCV)
4661 ``-semihosting-config [enable=on|off][,target=native|gdb|auto][,chardev=id][,userspace=on|off][,arg=str[,...]]``
4662 Enable and configure semihosting (ARM, M68K, Xtensa, MIPS, Nios II, RISC-V
4665 Note that this allows guest direct access to the host filesystem, so
4666 should only be used with a trusted guest OS.
4668 On Arm this implements the standard semihosting API, version 2.0.
4670 On M68K this implements the "ColdFire GDB
" interface used by
4673 Xtensa semihosting provides basic file IO calls, such as
4674 open/read/write/seek/select. Tensilica baremetal libc for ISS and
4675 linux platform "sim
" use this interface.
4677 On RISC-V this implements the standard semihosting API, version 0.2.
4679 ``target=native|gdb|auto``
4680 Defines where the semihosting calls will be addressed, to QEMU
4681 (``native``) or to GDB (``gdb``). The default is ``auto``, which
4682 means ``gdb`` during debug sessions and ``native`` otherwise.
4685 Send the output to a chardev backend output for native or auto
4686 output when not in gdb
4688 ``userspace=on|off``
4689 Allows code running in guest userspace to access the semihosting
4690 interface. The default is that only privileged guest code can
4691 make semihosting calls. Note that setting ``userspace=on`` should
4692 only be used if all guest code is trusted (for example, in
4693 bare-metal test case code).
4695 ``arg=str1,arg=str2,...``
4696 Allows the user to pass input arguments, and can be used
4697 multiple times to build up a list. The old-style
4698 ``-kernel``/``-append`` method of passing a command line is
4699 still supported for backward compatibility. If both the
4700 ``--semihosting-config arg`` and the ``-kernel``/``-append`` are
4701 specified, the former is passed to semihosting as it always
4704 DEF("old
-param
", 0, QEMU_OPTION_old_param,
4705 "-old
-param old param mode
\n", QEMU_ARCH_ARM)
4708 Old param mode (ARM only).
4711 DEF("sandbox
", HAS_ARG, QEMU_OPTION_sandbox, \
4712 "-sandbox on
[,obsolete
=allow|deny
][,elevateprivileges
=allow|deny|children
]\n" \
4713 " [,spawn
=allow|deny
][,resourcecontrol
=allow|deny
]\n" \
4714 " Enable seccomp mode
2 system call
filter (default 'off').\n" \
4715 " use
'obsolete' to allow obsolete system calls that are provided
\n" \
4716 " by the kernel
, but typically no longer used by modern
\n" \
4717 " C library implementations
.\n" \
4718 " use
'elevateprivileges' to allow or deny the QEMU process ability
\n" \
4719 " to elevate privileges
using set
*uid|gid system calls
.\n" \
4720 " The value
'children' will deny set
*uid|gid system calls
for\n" \
4721 " main QEMU process but will allow forks and execves to run unprivileged
\n" \
4722 " use
'spawn' to avoid QEMU to spawn
new threads or processes by
\n" \
4723 " blocking
*fork and execve
\n" \
4724 " use
'resourcecontrol' to disable process affinity and schedular priority
\n",
4727 ``-sandbox arg[,obsolete=string][,elevateprivileges=string][,spawn=string][,resourcecontrol=string]``
4728 Enable Seccomp mode 2 system call filter. 'on' will enable syscall
4729 filtering and 'off' will disable it. The default is 'off'.
4732 Enable Obsolete system calls
4734 ``elevateprivileges=string``
4735 Disable set\*uid\|gid system calls
4738 Disable \*fork and execve
4740 ``resourcecontrol=string``
4741 Disable process affinity and schedular priority
4744 DEF("readconfig
", HAS_ARG, QEMU_OPTION_readconfig,
4745 "-readconfig
<file
>\n"
4746 " read config file
\n", QEMU_ARCH_ALL)
4748 ``-readconfig file``
4749 Read device configuration from file. This approach is useful when
4750 you want to spawn QEMU process with many command line options but
4751 you don't want to exceed the command line character limit.
4754 DEF("no
-user
-config
", 0, QEMU_OPTION_nouserconfig,
4756 " do not load
default user
-provided config files at startup
\n",
4760 The ``-no-user-config`` option makes QEMU not load any of the
4761 user-provided config files on sysconfdir.
4764 DEF("trace", HAS_ARG, QEMU_OPTION_trace,
4765 "-trace [[enable
=]<pattern
>][,events
=<file
>][,file
=<file
>]\n"
4766 " specify tracing options
\n",
4769 ``-trace [[enable=]pattern][,events=file][,file=file]``
4770 .. include:: ../qemu-option-trace.rst.inc
4773 DEF("plugin
", HAS_ARG, QEMU_OPTION_plugin,
4774 "-plugin
[file
=]<file
>[,<argname
>=<argvalue
>]\n"
4778 ``-plugin file=file[,argname=argvalue]``
4782 Load the given plugin from a shared library file.
4784 ``argname=argvalue``
4785 Argument passed to the plugin. (Can be given multiple times.)
4789 DEF("qtest
", HAS_ARG, QEMU_OPTION_qtest, "", QEMU_ARCH_ALL)
4790 DEF("qtest
-log
", HAS_ARG, QEMU_OPTION_qtest_log, "", QEMU_ARCH_ALL)
4792 DEF("msg
", HAS_ARG, QEMU_OPTION_msg,
4793 "-msg
[timestamp
[=on|off
]][,guest
-name
=[on|off
]]\n"
4794 " control error message format
\n"
4795 " timestamp
=on enables
timestamps (default: off
)\n"
4796 " guest
-name
=on enables guest name prefix but only
if\n"
4797 " -name guest option is
set (default: off
)\n",
4800 ``-msg [timestamp[=on|off]][,guest-name[=on|off]]``
4801 Control error message format.
4803 ``timestamp=on|off``
4804 Prefix messages with a timestamp. Default is off.
4806 ``guest-name=on|off``
4807 Prefix messages with guest name but only if -name guest option is set
4808 otherwise the option is ignored. Default is off.
4811 DEF("dump
-vmstate
", HAS_ARG, QEMU_OPTION_dump_vmstate,
4812 "-dump
-vmstate
<file
>\n"
4813 " Output vmstate information
in JSON format to file
.\n"
4814 " Use the scripts
/vmstate
-static-checker
.py file to
\n"
4815 " check
for possible regressions
in migration code
\n"
4816 " by comparing two such vmstate dumps
.\n",
4819 ``-dump-vmstate file``
4820 Dump json-encoded vmstate information for current machine type to
4824 DEF("enable
-sync
-profile
", 0, QEMU_OPTION_enable_sync_profile,
4825 "-enable
-sync
-profile
\n"
4826 " enable synchronization profiling
\n",
4829 ``-enable-sync-profile``
4830 Enable synchronization profiling.
4835 DEFHEADING(Generic object creation:)
4837 DEF("object
", HAS_ARG, QEMU_OPTION_object,
4838 "-object TYPENAME
[,PROP1
=VALUE1
,...]\n"
4839 " create a
new object of type TYPENAME setting properties
\n"
4840 " in the order they are specified
. Note that the
'id'\n"
4841 " property must be set
. These objects are placed
in the
\n"
4842 " '/objects' path
.\n",
4845 ``-object typename[,prop1=value1,...]``
4846 Create a new object of type typename setting properties in the order
4847 they are specified. Note that the 'id' property must be set. These
4848 objects are placed in the '/objects' path.
4850 ``-object memory-backend-file,id=id,size=size,mem-path=dir,share=on|off,discard-data=on|off,merge=on|off,dump=on|off,prealloc=on|off,host-nodes=host-nodes,policy=default|preferred|bind|interleave,align=align,readonly=on|off``
4851 Creates a memory file backend object, which can be used to back
4852 the guest RAM with huge pages.
4854 The ``id`` parameter is a unique ID that will be used to
4855 reference this memory region in other parameters, e.g. ``-numa``,
4856 ``-device nvdimm``, etc.
4858 The ``size`` option provides the size of the memory region, and
4859 accepts common suffixes, e.g. ``500M``.
4861 The ``mem-path`` provides the path to either a shared memory or
4862 huge page filesystem mount.
4864 The ``share`` boolean option determines whether the memory
4865 region is marked as private to QEMU, or shared. The latter
4866 allows a co-operating external process to access the QEMU memory
4869 The ``share`` is also required for pvrdma devices due to
4870 limitations in the RDMA API provided by Linux.
4872 Setting share=on might affect the ability to configure NUMA
4873 bindings for the memory backend under some circumstances, see
4874 Documentation/vm/numa\_memory\_policy.txt on the Linux kernel
4875 source tree for additional details.
4877 Setting the ``discard-data`` boolean option to on indicates that
4878 file contents can be destroyed when QEMU exits, to avoid
4879 unnecessarily flushing data to the backing file. Note that
4880 ``discard-data`` is only an optimization, and QEMU might not
4881 discard file contents if it aborts unexpectedly or is terminated
4884 The ``merge`` boolean option enables memory merge, also known as
4885 MADV\_MERGEABLE, so that Kernel Samepage Merging will consider
4886 the pages for memory deduplication.
4888 Setting the ``dump`` boolean option to off excludes the memory
4889 from core dumps. This feature is also known as MADV\_DONTDUMP.
4891 The ``prealloc`` boolean option enables memory preallocation.
4893 The ``host-nodes`` option binds the memory range to a list of
4896 The ``policy`` option sets the NUMA policy to one of the
4903 prefer the given host node list for allocation
4906 restrict memory allocation to the given host node list
4909 interleave memory allocations across the given host node
4912 The ``align`` option specifies the base address alignment when
4913 QEMU mmap(2) ``mem-path``, and accepts common suffixes, eg
4914 ``2M``. Some backend store specified by ``mem-path`` requires an
4915 alignment different than the default one used by QEMU, eg the
4916 device DAX /dev/dax0.0 requires 2M alignment rather than 4K. In
4917 such cases, users can specify the required alignment via this
4920 The ``pmem`` option specifies whether the backing file specified
4921 by ``mem-path`` is in host persistent memory that can be
4922 accessed using the SNIA NVM programming model (e.g. Intel
4923 NVDIMM). If ``pmem`` is set to 'on', QEMU will take necessary
4924 operations to guarantee the persistence of its own writes to
4925 ``mem-path`` (e.g. in vNVDIMM label emulation and live
4926 migration). Also, we will map the backend-file with MAP\_SYNC
4927 flag, which ensures the file metadata is in sync for
4928 ``mem-path`` in case of host crash or a power failure. MAP\_SYNC
4929 requires support from both the host kernel (since Linux kernel
4930 4.15) and the filesystem of ``mem-path`` mounted with DAX
4933 The ``readonly`` option specifies whether the backing file is opened
4934 read-only or read-write (default).
4936 ``-object memory-backend-ram,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave``
4937 Creates a memory backend object, which can be used to back the
4938 guest RAM. Memory backend objects offer more control than the
4939 ``-m`` option that is traditionally used to define guest RAM.
4940 Please refer to ``memory-backend-file`` for a description of the
4943 ``-object memory-backend-memfd,id=id,merge=on|off,dump=on|off,share=on|off,prealloc=on|off,size=size,host-nodes=host-nodes,policy=default|preferred|bind|interleave,seal=on|off,hugetlb=on|off,hugetlbsize=size``
4944 Creates an anonymous memory file backend object, which allows
4945 QEMU to share the memory with an external process (e.g. when
4946 using vhost-user). The memory is allocated with memfd and
4947 optional sealing. (Linux only)
4949 The ``seal`` option creates a sealed-file, that will block
4950 further resizing the memory ('on' by default).
4952 The ``hugetlb`` option specify the file to be created resides in
4953 the hugetlbfs filesystem (since Linux 4.14). Used in conjunction
4954 with the ``hugetlb`` option, the ``hugetlbsize`` option specify
4955 the hugetlb page size on systems that support multiple hugetlb
4956 page sizes (it must be a power of 2 value supported by the
4959 In some versions of Linux, the ``hugetlb`` option is
4960 incompatible with the ``seal`` option (requires at least Linux
4963 Please refer to ``memory-backend-file`` for a description of the
4966 The ``share`` boolean option is on by default with memfd.
4968 ``-object rng-builtin,id=id``
4969 Creates a random number generator backend which obtains entropy
4970 from QEMU builtin functions. The ``id`` parameter is a unique ID
4971 that will be used to reference this entropy backend from the
4972 ``virtio-rng`` device. By default, the ``virtio-rng`` device
4973 uses this RNG backend.
4975 ``-object rng-random,id=id,filename=/dev/random``
4976 Creates a random number generator backend which obtains entropy
4977 from a device on the host. The ``id`` parameter is a unique ID
4978 that will be used to reference this entropy backend from the
4979 ``virtio-rng`` device. The ``filename`` parameter specifies
4980 which file to obtain entropy from and if omitted defaults to
4983 ``-object rng-egd,id=id,chardev=chardevid``
4984 Creates a random number generator backend which obtains entropy
4985 from an external daemon running on the host. The ``id``
4986 parameter is a unique ID that will be used to reference this
4987 entropy backend from the ``virtio-rng`` device. The ``chardev``
4988 parameter is the unique ID of a character device backend that
4989 provides the connection to the RNG daemon.
4991 ``-object tls-creds-anon,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off``
4992 Creates a TLS anonymous credentials object, which can be used to
4993 provide TLS support on network backends. The ``id`` parameter is
4994 a unique ID which network backends will use to access the
4995 credentials. The ``endpoint`` is either ``server`` or ``client``
4996 depending on whether the QEMU network backend that uses the
4997 credentials will be acting as a client or as a server. If
4998 ``verify-peer`` is enabled (the default) then once the handshake
4999 is completed, the peer credentials will be verified, though this
5000 is a no-op for anonymous credentials.
5002 The dir parameter tells QEMU where to find the credential files.
5003 For server endpoints, this directory may contain a file
5004 dh-params.pem providing diffie-hellman parameters to use for the
5005 TLS server. If the file is missing, QEMU will generate a set of
5006 DH parameters at startup. This is a computationally expensive
5007 operation that consumes random pool entropy, so it is
5008 recommended that a persistent set of parameters be generated
5011 ``-object tls-creds-psk,id=id,endpoint=endpoint,dir=/path/to/keys/dir[,username=username]``
5012 Creates a TLS Pre-Shared Keys (PSK) credentials object, which
5013 can be used to provide TLS support on network backends. The
5014 ``id`` parameter is a unique ID which network backends will use
5015 to access the credentials. The ``endpoint`` is either ``server``
5016 or ``client`` depending on whether the QEMU network backend that
5017 uses the credentials will be acting as a client or as a server.
5018 For clients only, ``username`` is the username which will be
5019 sent to the server. If omitted it defaults to "qemu
".
5021 The dir parameter tells QEMU where to find the keys file. It is
5022 called "dir
/keys
.psk
" and contains "username
:key
" pairs. This
5023 file can most easily be created using the GnuTLS ``psktool``
5026 For server endpoints, dir may also contain a file dh-params.pem
5027 providing diffie-hellman parameters to use for the TLS server.
5028 If the file is missing, QEMU will generate a set of DH
5029 parameters at startup. This is a computationally expensive
5030 operation that consumes random pool entropy, so it is
5031 recommended that a persistent set of parameters be generated up
5034 ``-object tls-creds-x509,id=id,endpoint=endpoint,dir=/path/to/cred/dir,priority=priority,verify-peer=on|off,passwordid=id``
5035 Creates a TLS anonymous credentials object, which can be used to
5036 provide TLS support on network backends. The ``id`` parameter is
5037 a unique ID which network backends will use to access the
5038 credentials. The ``endpoint`` is either ``server`` or ``client``
5039 depending on whether the QEMU network backend that uses the
5040 credentials will be acting as a client or as a server. If
5041 ``verify-peer`` is enabled (the default) then once the handshake
5042 is completed, the peer credentials will be verified. With x509
5043 certificates, this implies that the clients must be provided
5044 with valid client certificates too.
5046 The dir parameter tells QEMU where to find the credential files.
5047 For server endpoints, this directory may contain a file
5048 dh-params.pem providing diffie-hellman parameters to use for the
5049 TLS server. If the file is missing, QEMU will generate a set of
5050 DH parameters at startup. This is a computationally expensive
5051 operation that consumes random pool entropy, so it is
5052 recommended that a persistent set of parameters be generated
5055 For x509 certificate credentials the directory will contain
5056 further files providing the x509 certificates. The certificates
5057 must be stored in PEM format, in filenames ca-cert.pem,
5058 ca-crl.pem (optional), server-cert.pem (only servers),
5059 server-key.pem (only servers), client-cert.pem (only clients),
5060 and client-key.pem (only clients).
5062 For the server-key.pem and client-key.pem files which contain
5063 sensitive private keys, it is possible to use an encrypted
5064 version by providing the passwordid parameter. This provides the
5065 ID of a previously created ``secret`` object containing the
5066 password for decryption.
5068 The priority parameter allows to override the global default
5069 priority used by gnutls. This can be useful if the system
5070 administrator needs to use a weaker set of crypto priorities for
5071 QEMU without potentially forcing the weakness onto all
5072 applications. Or conversely if one wants wants a stronger
5073 default for QEMU than for all other applications, they can do
5074 this through this parameter. Its format is a gnutls priority
5075 string as described at
5076 https://gnutls.org/manual/html_node/Priority-Strings.html.
5078 ``-object tls-cipher-suites,id=id,priority=priority``
5079 Creates a TLS cipher suites object, which can be used to control
5080 the TLS cipher/protocol algorithms that applications are permitted
5083 The ``id`` parameter is a unique ID which frontends will use to
5084 access the ordered list of permitted TLS cipher suites from the
5087 The ``priority`` parameter allows to override the global default
5088 priority used by gnutls. This can be useful if the system
5089 administrator needs to use a weaker set of crypto priorities for
5090 QEMU without potentially forcing the weakness onto all
5091 applications. Or conversely if one wants wants a stronger
5092 default for QEMU than for all other applications, they can do
5093 this through this parameter. Its format is a gnutls priority
5094 string as described at
5095 https://gnutls.org/manual/html_node/Priority-Strings.html.
5097 An example of use of this object is to control UEFI HTTPS Boot.
5098 The tls-cipher-suites object exposes the ordered list of permitted
5099 TLS cipher suites from the host side to the guest firmware, via
5100 fw_cfg. The list is represented as an array of IANA_TLS_CIPHER
5101 objects. The firmware uses the IANA_TLS_CIPHER array for configuring
5104 In the following example, the priority at which the host-side policy
5105 is retrieved is given by the ``priority`` property.
5106 Given that QEMU uses GNUTLS, ``priority=@SYSTEM`` may be used to
5107 refer to /etc/crypto-policies/back-ends/gnutls.config.
5112 -object tls-cipher-suites,id=mysuite0,priority=@SYSTEM \\
5113 -fw_cfg name=etc/edk2/https/ciphers,gen_id=mysuite0
5115 ``-object filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off][,position=head|tail|id=<id>][,insert=behind|before]``
5116 Interval t can't be 0, this filter batches the packet delivery:
5117 all packets arriving in a given interval on netdev netdevid are
5118 delayed until the end of the interval. Interval is in
5119 microseconds. ``status`` is optional that indicate whether the
5120 netfilter is on (enabled) or off (disabled), the default status
5121 for netfilter will be 'on'.
5123 queue all\|rx\|tx is an option that can be applied to any
5126 ``all``: the filter is attached both to the receive and the
5127 transmit queue of the netdev (default).
5129 ``rx``: the filter is attached to the receive queue of the
5130 netdev, where it will receive packets sent to the netdev.
5132 ``tx``: the filter is attached to the transmit queue of the
5133 netdev, where it will receive packets sent by the netdev.
5135 position head\|tail\|id=<id> is an option to specify where the
5136 filter should be inserted in the filter list. It can be applied
5139 ``head``: the filter is inserted at the head of the filter list,
5140 before any existing filters.
5142 ``tail``: the filter is inserted at the tail of the filter list,
5143 behind any existing filters (default).
5145 ``id=<id>``: the filter is inserted before or behind the filter
5146 specified by <id>, see the insert option below.
5148 insert behind\|before is an option to specify where to insert
5149 the new filter relative to the one specified with
5150 position=id=<id>. It can be applied to any netfilter.
5152 ``before``: insert before the specified filter.
5154 ``behind``: insert behind the specified filter (default).
5156 ``-object filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]``
5157 filter-mirror on netdev netdevid,mirror net packet to
5158 chardevchardevid, if it has the vnet\_hdr\_support flag,
5159 filter-mirror will mirror packet with vnet\_hdr\_len.
5161 ``-object filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]``
5162 filter-redirector on netdev netdevid,redirect filter's net
5163 packet to chardev chardevid,and redirect indev's packet to
5164 filter.if it has the vnet\_hdr\_support flag, filter-redirector
5165 will redirect packet with vnet\_hdr\_len. Create a
5166 filter-redirector we need to differ outdev id from indev id, id
5167 can not be the same. we can just use indev or outdev, but at
5168 least one of indev or outdev need to be specified.
5170 ``-object filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind|before]``
5171 Filter-rewriter is a part of COLO project.It will rewrite tcp
5172 packet to secondary from primary to keep secondary tcp
5173 connection,and rewrite tcp packet to primary from secondary make
5174 tcp packet can be handled by client.if it has the
5175 vnet\_hdr\_support flag, we can parse packet with vnet header.
5177 usage: colo secondary: -object
5178 filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object
5179 filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 -object
5180 filter-rewriter,id=rew0,netdev=hn0,queue=all
5182 ``-object filter-dump,id=id,netdev=dev[,file=filename][,maxlen=len][,position=head|tail|id=<id>][,insert=behind|before]``
5183 Dump the network traffic on netdev dev to the file specified by
5184 filename. At most len bytes (64k by default) per packet are
5185 stored. The file format is libpcap, so it can be analyzed with
5186 tools such as tcpdump or Wireshark.
5188 ``-object colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid,iothread=id[,vnet_hdr_support][,notify_dev=id][,compare_timeout=@var{ms}][,expired_scan_cycle=@var{ms}][,max_queue_size=@var{size}]``
5189 Colo-compare gets packet from primary\_in chardevid and
5190 secondary\_in, then compare whether the payload of primary packet
5191 and secondary packet are the same. If same, it will output
5192 primary packet to out\_dev, else it will notify COLO-framework to do
5193 checkpoint and send primary packet to out\_dev. In order to
5194 improve efficiency, we need to put the task of comparison in
5195 another iothread. If it has the vnet\_hdr\_support flag,
5196 colo compare will send/recv packet with vnet\_hdr\_len.
5197 The compare\_timeout=@var{ms} determines the maximum time of the
5198 colo-compare hold the packet. The expired\_scan\_cycle=@var{ms}
5199 is to set the period of scanning expired primary node network packets.
5200 The max\_queue\_size=@var{size} is to set the max compare queue
5201 size depend on user environment.
5202 If user want to use Xen COLO, need to add the notify\_dev to
5203 notify Xen colo-frame to do checkpoint.
5205 COLO-compare must be used with the help of filter-mirror,
5206 filter-redirector and filter-rewriter.
5213 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
5214 -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
5215 -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
5216 -chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
5217 -chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
5218 -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
5219 -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
5220 -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
5221 -object iothread,id=iothread1
5222 -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
5223 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
5224 -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
5225 -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1
5228 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
5229 -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
5230 -chardev socket,id=red0,host=3.3.3.3,port=9003
5231 -chardev socket,id=red1,host=3.3.3.3,port=9004
5232 -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
5233 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
5239 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
5240 -device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
5241 -chardev socket,id=mirror0,host=3.3.3.3,port=9003,server=on,wait=off
5242 -chardev socket,id=compare1,host=3.3.3.3,port=9004,server=on,wait=off
5243 -chardev socket,id=compare0,host=3.3.3.3,port=9001,server=on,wait=off
5244 -chardev socket,id=compare0-0,host=3.3.3.3,port=9001
5245 -chardev socket,id=compare_out,host=3.3.3.3,port=9005,server=on,wait=off
5246 -chardev socket,id=compare_out0,host=3.3.3.3,port=9005
5247 -chardev socket,id=notify_way,host=3.3.3.3,port=9009,server=on,wait=off
5248 -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
5249 -object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
5250 -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
5251 -object iothread,id=iothread1
5252 -object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,notify_dev=nofity_way,iothread=iothread1
5255 -netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
5256 -device e1000,netdev=hn0,mac=52:a4:00:12:78:66
5257 -chardev socket,id=red0,host=3.3.3.3,port=9003
5258 -chardev socket,id=red1,host=3.3.3.3,port=9004
5259 -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
5260 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
5262 If you want to know the detail of above command line, you can
5263 read the colo-compare git log.
5265 ``-object cryptodev-backend-builtin,id=id[,queues=queues]``
5266 Creates a cryptodev backend which executes crypto opreation from
5267 the QEMU cipher APIS. The id parameter is a unique ID that will
5268 be used to reference this cryptodev backend from the
5269 ``virtio-crypto`` device. The queues parameter is optional,
5270 which specify the queue number of cryptodev backend, the default
5277 -object cryptodev-backend-builtin,id=cryptodev0 \\
5278 -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \\
5281 ``-object cryptodev-vhost-user,id=id,chardev=chardevid[,queues=queues]``
5282 Creates a vhost-user cryptodev backend, backed by a chardev
5283 chardevid. The id parameter is a unique ID that will be used to
5284 reference this cryptodev backend from the ``virtio-crypto``
5285 device. The chardev should be a unix domain socket backed one.
5286 The vhost-user uses a specifically defined protocol to pass
5287 vhost ioctl replacement messages to an application on the other
5288 end of the socket. The queues parameter is optional, which
5289 specify the queue number of cryptodev backend for multiqueue
5290 vhost-user, the default of queues is 1.
5296 -chardev socket,id=chardev0,path=/path/to/socket \\
5297 -object cryptodev-vhost-user,id=cryptodev0,chardev=chardev0 \\
5298 -device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \\
5301 ``-object secret,id=id,data=string,format=raw|base64[,keyid=secretid,iv=string]``
5303 ``-object secret,id=id,file=filename,format=raw|base64[,keyid=secretid,iv=string]``
5304 Defines a secret to store a password, encryption key, or some
5305 other sensitive data. The sensitive data can either be passed
5306 directly via the data parameter, or indirectly via the file
5307 parameter. Using the data parameter is insecure unless the
5308 sensitive data is encrypted.
5310 The sensitive data can be provided in raw format (the default),
5311 or base64. When encoded as JSON, the raw format only supports
5312 valid UTF-8 characters, so base64 is recommended for sending
5313 binary data. QEMU will convert from which ever format is
5314 provided to the format it needs internally. eg, an RBD password
5315 can be provided in raw format, even though it will be base64
5316 encoded when passed onto the RBD sever.
5318 For added protection, it is possible to encrypt the data
5319 associated with a secret using the AES-256-CBC cipher. Use of
5320 encryption is indicated by providing the keyid and iv
5321 parameters. The keyid parameter provides the ID of a previously
5322 defined secret that contains the AES-256 decryption key. This
5323 key should be 32-bytes long and be base64 encoded. The iv
5324 parameter provides the random initialization vector used for
5325 encryption of this particular secret and should be a base64
5326 encrypted string of the 16-byte IV.
5328 The simplest (insecure) usage is to provide the secret inline
5332 # |qemu_system| -object secret,id=sec0,data=letmein,format=raw
5334 The simplest secure usage is to provide the secret via a file
5336 # printf "letmein
" > mypasswd.txt # QEMU\_SYSTEM\_MACRO -object
5337 secret,id=sec0,file=mypasswd.txt,format=raw
5339 For greater security, AES-256-CBC should be used. To illustrate
5340 usage, consider the openssl command line tool which can encrypt
5341 the data. Note that when encrypting, the plaintext must be
5342 padded to the cipher block size (32 bytes) using the standard
5343 PKCS#5/6 compatible padding algorithm.
5345 First a master key needs to be created in base64 encoding:
5349 # openssl rand -base64 32 > key.b64
5350 # KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X
"')
5352 Each secret to be encrypted needs to have a random
5353 initialization vector generated. These do not need to be kept
5358 # openssl rand -base64 16 > iv.b64
5359 # IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X
"')
5361 The secret to be defined can now be encrypted, in this case
5362 we're telling openssl to base64 encode the result, but it could
5363 be left as raw bytes if desired.
5367 # SECRET=$(printf "letmein
" |
5368 openssl enc -aes-256-cbc -a -K $KEY -iv $IV)
5370 When launching QEMU, create a master secret pointing to
5371 ``key.b64`` and specify that to be used to decrypt the user
5372 password. Pass the contents of ``iv.b64`` to the second secret
5377 -object secret,id=secmaster0,format=base64,file=key.b64 \\
5378 -object secret,id=sec0,keyid=secmaster0,format=base64,\\
5379 data=$SECRET,iv=$(<iv.b64)
5381 ``-object sev-guest,id=id,cbitpos=cbitpos,reduced-phys-bits=val,[sev-device=string,policy=policy,handle=handle,dh-cert-file=file,session-file=file,kernel-hashes=on|off]``
5382 Create a Secure Encrypted Virtualization (SEV) guest object,
5383 which can be used to provide the guest memory encryption support
5386 When memory encryption is enabled, one of the physical address
5387 bit (aka the C-bit) is utilized to mark if a memory page is
5388 protected. The ``cbitpos`` is used to provide the C-bit
5389 position. The C-bit position is Host family dependent hence user
5390 must provide this value. On EPYC, the value should be 47.
5392 When memory encryption is enabled, we loose certain bits in
5393 physical address space. The ``reduced-phys-bits`` is used to
5394 provide the number of bits we loose in physical address space.
5395 Similar to C-bit, the value is Host family dependent. On EPYC,
5396 the value should be 5.
5398 The ``sev-device`` provides the device file to use for
5399 communicating with the SEV firmware running inside AMD Secure
5400 Processor. The default device is '/dev/sev'. If hardware
5401 supports memory encryption then /dev/sev devices are created by
5404 The ``policy`` provides the guest policy to be enforced by the
5405 SEV firmware and restrict what configuration and operational
5406 commands can be performed on this guest by the hypervisor. The
5407 policy should be provided by the guest owner and is bound to the
5408 guest and cannot be changed throughout the lifetime of the
5409 guest. The default is 0.
5411 If guest ``policy`` allows sharing the key with another SEV
5412 guest then ``handle`` can be use to provide handle of the guest
5413 from which to share the key.
5415 The ``dh-cert-file`` and ``session-file`` provides the guest
5416 owner's Public Diffie-Hillman key defined in SEV spec. The PDH
5417 and session parameters are used for establishing a cryptographic
5418 session with the guest owner to negotiate keys used for
5419 attestation. The file must be encoded in base64.
5421 The ``kernel-hashes`` adds the hashes of given kernel/initrd/
5422 cmdline to a designated guest firmware page for measured Linux
5423 boot with -kernel. The default is off. (Since 6.2)
5425 e.g to launch a SEV guest
5429 # |qemu_system_x86| \\
5431 -object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=5 \\
5432 -machine ...,memory-encryption=sev0 \\
5435 ``-object authz-simple,id=id,identity=string``
5436 Create an authorization object that will control access to
5439 The ``identity`` parameter is identifies the user and its format
5440 depends on the network service that authorization object is
5441 associated with. For authorizing based on TLS x509 certificates,
5442 the identity must be the x509 distinguished name. Note that care
5443 must be taken to escape any commas in the distinguished name.
5445 An example authorization object to validate a x509 distinguished
5446 name would look like:
5452 -object 'authz-simple,id=auth0,identity=CN=laptop.example.com,,O=Example Org,,L=London,,ST=London,,C=GB' \\
5455 Note the use of quotes due to the x509 distinguished name
5456 containing whitespace, and escaping of ','.
5458 ``-object authz-listfile,id=id,filename=path,refresh=on|off``
5459 Create an authorization object that will control access to
5462 The ``filename`` parameter is the fully qualified path to a file
5463 containing the access control list rules in JSON format.
5465 An example set of rules that match against SASL usernames might
5472 { "match
": "fred
", "policy
": "allow
", "format
": "exact
" },
5473 { "match
": "bob
", "policy
": "allow
", "format
": "exact
" },
5474 { "match
": "danb
", "policy
": "deny
", "format
": "glob
" },
5475 { "match
": "dan
*", "policy
": "allow
", "format
": "exact
" },
5480 When checking access the object will iterate over all the rules
5481 and the first rule to match will have its ``policy`` value
5482 returned as the result. If no rules match, then the default
5483 ``policy`` value is returned.
5485 The rules can either be an exact string match, or they can use
5486 the simple UNIX glob pattern matching to allow wildcards to be
5489 If ``refresh`` is set to true the file will be monitored and
5490 automatically reloaded whenever its content changes.
5492 As with the ``authz-simple`` object, the format of the identity
5493 strings being matched depends on the network service, but is
5494 usually a TLS x509 distinguished name, or a SASL username.
5496 An example authorization object to validate a SASL username
5503 -object authz-simple,id=auth0,filename=/etc/qemu/vnc-sasl.acl,refresh=on \\
5506 ``-object authz-pam,id=id,service=string``
5507 Create an authorization object that will control access to
5510 The ``service`` parameter provides the name of a PAM service to
5511 use for authorization. It requires that a file
5512 ``/etc/pam.d/service`` exist to provide the configuration for
5513 the ``account`` subsystem.
5515 An example authorization object to validate a TLS x509
5516 distinguished name would look like:
5522 -object authz-pam,id=auth0,service=qemu-vnc \\
5525 There would then be a corresponding config file for PAM at
5526 ``/etc/pam.d/qemu-vnc`` that contains:
5530 account requisite pam_listfile.so item=user sense=allow \
5531 file=/etc/qemu/vnc.allow
5533 Finally the ``/etc/qemu/vnc.allow`` file would contain the list
5534 of x509 distingished names that are permitted access
5538 CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB
5540 ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch``
5541 Creates a dedicated event loop thread that devices can be
5542 assigned to. This is known as an IOThread. By default device
5543 emulation happens in vCPU threads or the main event loop thread.
5544 This can become a scalability bottleneck. IOThreads allow device
5545 emulation and I/O to run on other host CPUs.
5547 The ``id`` parameter is a unique ID that will be used to
5548 reference this IOThread from ``-device ...,iothread=id``.
5549 Multiple devices can be assigned to an IOThread. Note that not
5550 all devices support an ``iothread`` parameter.
5552 The ``query-iothreads`` QMP command lists IOThreads and reports
5553 their thread IDs so that the user can configure host CPU
5556 IOThreads use an adaptive polling algorithm to reduce event loop
5557 latency. Instead of entering a blocking system call to monitor
5558 file descriptors and then pay the cost of being woken up when an
5559 event occurs, the polling algorithm spins waiting for events for
5560 a short time. The algorithm's default parameters are suitable
5561 for many cases but can be adjusted based on knowledge of the
5562 workload and/or host device latency.
5564 The ``poll-max-ns`` parameter is the maximum number of
5565 nanoseconds to busy wait for events. Polling can be disabled by
5566 setting this value to 0.
5568 The ``poll-grow`` parameter is the multiplier used to increase
5569 the polling time when the algorithm detects it is missing events
5570 due to not polling long enough.
5572 The ``poll-shrink`` parameter is the divisor used to decrease
5573 the polling time when the algorithm detects it is spending too
5574 long polling without encountering events.
5576 The ``aio-max-batch`` parameter is the maximum number of requests
5577 in a batch for the AIO engine, 0 means that the engine will use
5580 The IOThread parameters can be modified at run-time using the
5581 ``qom-set`` command (where ``iothread1`` is the IOThread's
5586 (qemu) qom-set /objects/iothread1 poll-max-ns 100000
5590 HXCOMM This is the last statement. Insert new options before this line!