virtio-net: fix wild pointer when remove virtio-net queues

[qemu.git] / qemu-doc.texi

\input texinfo @c -*- texinfo -*-
@c %**start of header
@setfilename qemu-doc.info

@documentlanguage en
@documentencoding UTF-8

@settitle QEMU Emulator User Documentation
@exampleindent 0
@paragraphindent 0
@c %**end of header

@ifinfo
@direntry
* QEMU: (qemu-doc).    The QEMU Emulator User Documentation.
@end direntry
@end ifinfo

@iftex
@titlepage
@sp 7
@center @titlefont{QEMU Emulator}
@sp 1
@center @titlefont{User Documentation}
@sp 3
@end titlepage
@end iftex

@ifnottex
@node Top
@top

@menu
* Introduction::
* QEMU PC System emulator::
* QEMU System emulator for non PC targets::
* QEMU User space emulator::
* Implementation notes::
* License::
* Index::
@end menu
@end ifnottex

@contents

@node Introduction
@chapter Introduction

@menu
* intro_features:: Features
@end menu

@node intro_features
@section Features

QEMU is a FAST! processor emulator using dynamic translation to
achieve good emulation speed.

@cindex operating modes
QEMU has two operating modes:

@itemize
@cindex system emulation
@item Full system emulation. In this mode, QEMU emulates a full system (for
example a PC), including one or several processors and various
peripherals. It can be used to launch different Operating Systems
without rebooting the PC or to debug system code.

@cindex user mode emulation
@item User mode emulation. In this mode, QEMU can launch
processes compiled for one CPU on another CPU. It can be used to
launch the Wine Windows API emulator (@url{http://www.winehq.org}) or
to ease cross-compilation and cross-debugging.

@end itemize

QEMU has the following features:

@itemize
@item QEMU can run without a host kernel driver and yet gives acceptable
performance.  It uses dynamic translation to native code for reasonable speed,
with support for self-modifying code and precise exceptions.

@item It is portable to several operating systems (GNU/Linux, *BSD, Mac OS X,
Windows) and architectures.

@item It performs accurate software emulation of the FPU.
@end itemize

QEMU user mode emulation has the following features:
@itemize
@item Generic Linux system call converter, including most ioctls.

@item clone() emulation using native CPU clone() to use Linux scheduler for threads.

@item Accurate signal handling by remapping host signals to target signals.
@end itemize

QEMU full system emulation has the following features:
@itemize
@item
QEMU uses a full software MMU for maximum portability.

@item
QEMU can optionally use an in-kernel accelerator, like kvm. The accelerators 
execute most of the guest code natively, while
continuing to emulate the rest of the machine.

@item
Various hardware devices can be emulated and in some cases, host
devices (e.g. serial and parallel ports, USB, drives) can be used
transparently by the guest Operating System. Host device passthrough
can be used for talking to external physical peripherals (e.g. a
webcam, modem or tape drive).

@item
Symmetric multiprocessing (SMP) support.  Currently, an in-kernel
accelerator is required to use more than one host CPU for emulation.

@end itemize


@node QEMU PC System emulator
@chapter QEMU PC System emulator
@cindex system emulation (PC)

@menu
* pcsys_introduction:: Introduction
* pcsys_quickstart::   Quick Start
* sec_invocation::     Invocation
* pcsys_keys::         Keys in the graphical frontends
* mux_keys::           Keys in the character backend multiplexer
* pcsys_monitor::      QEMU Monitor
* disk_images::        Disk Images
* pcsys_network::      Network emulation
* pcsys_other_devs::   Other Devices
* direct_linux_boot::  Direct Linux Boot
* pcsys_usb::          USB emulation
* vnc_security::       VNC security
* gdb_usage::          GDB usage
* pcsys_os_specific::  Target OS specific information
@end menu

@node pcsys_introduction
@section Introduction

@c man begin DESCRIPTION

The QEMU PC System emulator simulates the
following peripherals:

@itemize @minus
@item
i440FX host PCI bridge and PIIX3 PCI to ISA bridge
@item
Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs VESA
extensions (hardware level, including all non standard modes).
@item
PS/2 mouse and keyboard
@item
2 PCI IDE interfaces with hard disk and CD-ROM support
@item
Floppy disk
@item
PCI and ISA network adapters
@item
Serial ports
@item
IPMI BMC, either and internal or external one
@item
Creative SoundBlaster 16 sound card
@item
ENSONIQ AudioPCI ES1370 sound card
@item
Intel 82801AA AC97 Audio compatible sound card
@item
Intel HD Audio Controller and HDA codec
@item
Adlib (OPL2) - Yamaha YM3812 compatible chip
@item
Gravis Ultrasound GF1 sound card
@item
CS4231A compatible sound card
@item
PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual USB-1.1 hub.
@end itemize

SMP is supported with up to 255 CPUs.

QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL
VGA BIOS.

QEMU uses YM3812 emulation by Tatsuyuki Satoh.

QEMU uses GUS emulation (GUSEMU32 @url{http://www.deinmeister.de/gusemu/})
by Tibor "TS" Schütz.

Note that, by default, GUS shares IRQ(7) with parallel ports and so
QEMU must be told to not have parallel ports to have working GUS.

@example
qemu-system-i386 dos.img -soundhw gus -parallel none
@end example

Alternatively:
@example
qemu-system-i386 dos.img -device gus,irq=5
@end example

Or some other unclaimed IRQ.

CS4231A is the chip used in Windows Sound System and GUSMAX products

@c man end

@node pcsys_quickstart
@section Quick Start
@cindex quick start

Download and uncompress the linux image (@file{linux.img}) and type:

@example
qemu-system-i386 linux.img
@end example

Linux should boot and give you a prompt.

@node sec_invocation
@section Invocation

@example
@c man begin SYNOPSIS
@command{qemu-system-i386} [@var{options}] [@var{disk_image}]
@c man end
@end example

@c man begin OPTIONS
@var{disk_image} is a raw hard disk image for IDE hard disk 0. Some
targets do not need a disk image.

@include qemu-options.texi

@c man end

@node pcsys_keys
@section Keys in the graphical frontends

@c man begin OPTIONS

During the graphical emulation, you can use special key combinations to change
modes. The default key mappings are shown below, but if you use @code{-alt-grab}
then the modifier is Ctrl-Alt-Shift (instead of Ctrl-Alt) and if you use
@code{-ctrl-grab} then the modifier is the right Ctrl key (instead of Ctrl-Alt):

@table @key
@item Ctrl-Alt-f
@kindex Ctrl-Alt-f
Toggle full screen

@item Ctrl-Alt-+
@kindex Ctrl-Alt-+
Enlarge the screen

@item Ctrl-Alt--
@kindex Ctrl-Alt--
Shrink the screen

@item Ctrl-Alt-u
@kindex Ctrl-Alt-u
Restore the screen's un-scaled dimensions

@item Ctrl-Alt-n
@kindex Ctrl-Alt-n
Switch to virtual console 'n'. Standard console mappings are:
@table @emph
@item 1
Target system display
@item 2
Monitor
@item 3
Serial port
@end table

@item Ctrl-Alt
@kindex Ctrl-Alt
Toggle mouse and keyboard grab.
@end table

@kindex Ctrl-Up
@kindex Ctrl-Down
@kindex Ctrl-PageUp
@kindex Ctrl-PageDown
In the virtual consoles, you can use @key{Ctrl-Up}, @key{Ctrl-Down},
@key{Ctrl-PageUp} and @key{Ctrl-PageDown} to move in the back log.

@c man end

@node mux_keys
@section Keys in the character backend multiplexer

@c man begin OPTIONS

During emulation, if you are using a character backend multiplexer
(which is the default if you are using @option{-nographic}) then
several commands are available via an escape sequence. These
key sequences all start with an escape character, which is @key{Ctrl-a}
by default, but can be changed with @option{-echr}. The list below assumes
you're using the default.

@table @key
@item Ctrl-a h
@kindex Ctrl-a h
Print this help
@item Ctrl-a x
@kindex Ctrl-a x
Exit emulator
@item Ctrl-a s
@kindex Ctrl-a s
Save disk data back to file (if -snapshot)
@item Ctrl-a t
@kindex Ctrl-a t
Toggle console timestamps
@item Ctrl-a b
@kindex Ctrl-a b
Send break (magic sysrq in Linux)
@item Ctrl-a c
@kindex Ctrl-a c
Rotate between the frontends connected to the multiplexer (usually
this switches between the monitor and the console)
@item Ctrl-a Ctrl-a
@kindex Ctrl-a Ctrl-a
Send the escape character to the frontend
@end table
@c man end

@ignore

@c man begin SEEALSO
The HTML documentation of QEMU for more precise information and Linux
user mode emulator invocation.
@c man end

@c man begin AUTHOR
Fabrice Bellard
@c man end

@end ignore

@node pcsys_monitor
@section QEMU Monitor
@cindex QEMU monitor

The QEMU monitor is used to give complex commands to the QEMU
emulator. You can use it to:

@itemize @minus

@item
Remove or insert removable media images
(such as CD-ROM or floppies).

@item
Freeze/unfreeze the Virtual Machine (VM) and save or restore its state
from a disk file.

@item Inspect the VM state without an external debugger.

@end itemize

@subsection Commands

The following commands are available:

@include qemu-monitor.texi

@include qemu-monitor-info.texi

@subsection Integer expressions

The monitor understands integers expressions for every integer
argument. You can use register names to get the value of specifics
CPU registers by prefixing them with @emph{$}.

@node disk_images
@section Disk Images

Since version 0.6.1, QEMU supports many disk image formats, including
growable disk images (their size increase as non empty sectors are
written), compressed and encrypted disk images. Version 0.8.3 added
the new qcow2 disk image format which is essential to support VM
snapshots.

@menu
* disk_images_quickstart::    Quick start for disk image creation
* disk_images_snapshot_mode:: Snapshot mode
* vm_snapshots::              VM snapshots
* qemu_img_invocation::       qemu-img Invocation
* qemu_nbd_invocation::       qemu-nbd Invocation
* qemu_ga_invocation::        qemu-ga Invocation
* disk_images_formats::       Disk image file formats
* host_drives::               Using host drives
* disk_images_fat_images::    Virtual FAT disk images
* disk_images_nbd::           NBD access
* disk_images_sheepdog::      Sheepdog disk images
* disk_images_iscsi::         iSCSI LUNs
* disk_images_gluster::       GlusterFS disk images
* disk_images_ssh::           Secure Shell (ssh) disk images
@end menu

@node disk_images_quickstart
@subsection Quick start for disk image creation

You can create a disk image with the command:
@example
qemu-img create myimage.img mysize
@end example
where @var{myimage.img} is the disk image filename and @var{mysize} is its
size in kilobytes. You can add an @code{M} suffix to give the size in
megabytes and a @code{G} suffix for gigabytes.

See @ref{qemu_img_invocation} for more information.

@node disk_images_snapshot_mode
@subsection Snapshot mode

If you use the option @option{-snapshot}, all disk images are
considered as read only. When sectors in written, they are written in
a temporary file created in @file{/tmp}. You can however force the
write back to the raw disk images by using the @code{commit} monitor
command (or @key{C-a s} in the serial console).

@node vm_snapshots
@subsection VM snapshots

VM snapshots are snapshots of the complete virtual machine including
CPU state, RAM, device state and the content of all the writable
disks. In order to use VM snapshots, you must have at least one non
removable and writable block device using the @code{qcow2} disk image
format. Normally this device is the first virtual hard drive.

Use the monitor command @code{savevm} to create a new VM snapshot or
replace an existing one. A human readable name can be assigned to each
snapshot in addition to its numerical ID.

Use @code{loadvm} to restore a VM snapshot and @code{delvm} to remove
a VM snapshot. @code{info snapshots} lists the available snapshots
with their associated information:

@example
(qemu) info snapshots
Snapshot devices: hda
Snapshot list (from hda):
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         start                   41M 2006-08-06 12:38:02   00:00:14.954
2                                 40M 2006-08-06 12:43:29   00:00:18.633
3         msys                    40M 2006-08-06 12:44:04   00:00:23.514
@end example

A VM snapshot is made of a VM state info (its size is shown in
@code{info snapshots}) and a snapshot of every writable disk image.
The VM state info is stored in the first @code{qcow2} non removable
and writable block device. The disk image snapshots are stored in
every disk image. The size of a snapshot in a disk image is difficult
to evaluate and is not shown by @code{info snapshots} because the
associated disk sectors are shared among all the snapshots to save
disk space (otherwise each snapshot would need a full copy of all the
disk images).

When using the (unrelated) @code{-snapshot} option
(@ref{disk_images_snapshot_mode}), you can always make VM snapshots,
but they are deleted as soon as you exit QEMU.

VM snapshots currently have the following known limitations:
@itemize
@item
They cannot cope with removable devices if they are removed or
inserted after a snapshot is done.
@item
A few device drivers still have incomplete snapshot support so their
state is not saved or restored properly (in particular USB).
@end itemize

@node qemu_img_invocation
@subsection @code{qemu-img} Invocation

@include qemu-img.texi

@node qemu_nbd_invocation
@subsection @code{qemu-nbd} Invocation

@include qemu-nbd.texi

@node qemu_ga_invocation
@subsection @code{qemu-ga} Invocation

@include qemu-ga.texi

@node disk_images_formats
@subsection Disk image file formats

QEMU supports many image file formats that can be used with VMs as well as with
any of the tools (like @code{qemu-img}). This includes the preferred formats
raw and qcow2 as well as formats that are supported for compatibility with
older QEMU versions or other hypervisors.

Depending on the image format, different options can be passed to
@code{qemu-img create} and @code{qemu-img convert} using the @code{-o} option.
This section describes each format and the options that are supported for it.

@table @option
@item raw

Raw disk image format. This format has the advantage of
being simple and easily exportable to all other emulators. If your
file system supports @emph{holes} (for example in ext2 or ext3 on
Linux or NTFS on Windows), then only the written sectors will reserve
space. Use @code{qemu-img info} to know the real size used by the
image or @code{ls -ls} on Unix/Linux.

Supported options:
@table @code
@item preallocation
Preallocation mode (allowed values: @code{off}, @code{falloc}, @code{full}).
@code{falloc} mode preallocates space for image by calling posix_fallocate().
@code{full} mode preallocates space for image by writing zeros to underlying
storage.
@end table

@item qcow2
QEMU image format, the most versatile format. Use it to have smaller
images (useful if your filesystem does not supports holes, for example
on Windows), zlib based compression and support of multiple VM
snapshots.

Supported options:
@table @code
@item compat
Determines the qcow2 version to use. @code{compat=0.10} uses the
traditional image format that can be read by any QEMU since 0.10.
@code{compat=1.1} enables image format extensions that only QEMU 1.1 and
newer understand (this is the default). Amongst others, this includes
zero clusters, which allow efficient copy-on-read for sparse images.

@item backing_file
File name of a base image (see @option{create} subcommand)
@item backing_fmt
Image format of the base image
@item encryption
If this option is set to @code{on}, the image is encrypted with 128-bit AES-CBC.

The use of encryption in qcow and qcow2 images is considered to be flawed by
modern cryptography standards, suffering from a number of design problems:

@itemize @minus
@item The AES-CBC cipher is used with predictable initialization vectors based
on the sector number. This makes it vulnerable to chosen plaintext attacks
which can reveal the existence of encrypted data.
@item The user passphrase is directly used as the encryption key. A poorly
chosen or short passphrase will compromise the security of the encryption.
@item In the event of the passphrase being compromised there is no way to
change the passphrase to protect data in any qcow images. The files must
be cloned, using a different encryption passphrase in the new file. The
original file must then be securely erased using a program like shred,
though even this is ineffective with many modern storage technologies.
@end itemize

Use of qcow / qcow2 encryption with QEMU is deprecated, and support for
it will go away in a future release.  Users are recommended to use an
alternative encryption technology such as the Linux dm-crypt / LUKS
system.

@item cluster_size
Changes the qcow2 cluster size (must be between 512 and 2M). Smaller cluster
sizes can improve the image file size whereas larger cluster sizes generally
provide better performance.

@item preallocation
Preallocation mode (allowed values: @code{off}, @code{metadata}, @code{falloc},
@code{full}). An image with preallocated metadata is initially larger but can
improve performance when the image needs to grow. @code{falloc} and @code{full}
preallocations are like the same options of @code{raw} format, but sets up
metadata also.

@item lazy_refcounts
If this option is set to @code{on}, reference count updates are postponed with
the goal of avoiding metadata I/O and improving performance. This is
particularly interesting with @option{cache=writethrough} which doesn't batch
metadata updates. The tradeoff is that after a host crash, the reference count
tables must be rebuilt, i.e. on the next open an (automatic) @code{qemu-img
check -r all} is required, which may take some time.

This option can only be enabled if @code{compat=1.1} is specified.

@item nocow
If this option is set to @code{on}, it will turn off COW of the file. It's only
valid on btrfs, no effect on other file systems.

Btrfs has low performance when hosting a VM image file, even more when the guest
on the VM also using btrfs as file system. Turning off COW is a way to mitigate
this bad performance. Generally there are two ways to turn off COW on btrfs:
a) Disable it by mounting with nodatacow, then all newly created files will be
NOCOW. b) For an empty file, add the NOCOW file attribute. That's what this option
does.

Note: this option is only valid to new or empty files. If there is an existing
file which is COW and has data blocks already, it couldn't be changed to NOCOW
by setting @code{nocow=on}. One can issue @code{lsattr filename} to check if
the NOCOW flag is set or not (Capital 'C' is NOCOW flag).

@end table

@item qed
Old QEMU image format with support for backing files and compact image files
(when your filesystem or transport medium does not support holes).

When converting QED images to qcow2, you might want to consider using the
@code{lazy_refcounts=on} option to get a more QED-like behaviour.

Supported options:
@table @code
@item backing_file
File name of a base image (see @option{create} subcommand).
@item backing_fmt
Image file format of backing file (optional).  Useful if the format cannot be
autodetected because it has no header, like some vhd/vpc files.
@item cluster_size
Changes the cluster size (must be power-of-2 between 4K and 64K). Smaller
cluster sizes can improve the image file size whereas larger cluster sizes
generally provide better performance.
@item table_size
Changes the number of clusters per L1/L2 table (must be power-of-2 between 1
and 16).  There is normally no need to change this value but this option can be
used for performance benchmarking.
@end table

@item qcow
Old QEMU image format with support for backing files, compact image files,
encryption and compression.

Supported options:
@table @code
@item backing_file
File name of a base image (see @option{create} subcommand)
@item encryption
If this option is set to @code{on}, the image is encrypted.
@end table

@item vdi
VirtualBox 1.1 compatible image format.
Supported options:
@table @code
@item static
If this option is set to @code{on}, the image is created with metadata
preallocation.
@end table

@item vmdk
VMware 3 and 4 compatible image format.

Supported options:
@table @code
@item backing_file
File name of a base image (see @option{create} subcommand).
@item compat6
Create a VMDK version 6 image (instead of version 4)
@item hwversion
Specify vmdk virtual hardware version. Compat6 flag cannot be enabled
if hwversion is specified.
@item subformat
Specifies which VMDK subformat to use. Valid options are
@code{monolithicSparse} (default),
@code{monolithicFlat},
@code{twoGbMaxExtentSparse},
@code{twoGbMaxExtentFlat} and
@code{streamOptimized}.
@end table

@item vpc
VirtualPC compatible image format (VHD).
Supported options:
@table @code
@item subformat
Specifies which VHD subformat to use. Valid options are
@code{dynamic} (default) and @code{fixed}.
@end table

@item VHDX
Hyper-V compatible image format (VHDX).
Supported options:
@table @code
@item subformat
Specifies which VHDX subformat to use. Valid options are
@code{dynamic} (default) and @code{fixed}.
@item block_state_zero
Force use of payload blocks of type 'ZERO'.  Can be set to @code{on} (default)
or @code{off}.  When set to @code{off}, new blocks will be created as
@code{PAYLOAD_BLOCK_NOT_PRESENT}, which means parsers are free to return
arbitrary data for those blocks.  Do not set to @code{off} when using
@code{qemu-img convert} with @code{subformat=dynamic}.
@item block_size
Block size; min 1 MB, max 256 MB.  0 means auto-calculate based on image size.
@item log_size
Log size; min 1 MB.
@end table
@end table

@subsubsection Read-only formats
More disk image file formats are supported in a read-only mode.
@table @option
@item bochs
Bochs images of @code{growing} type.
@item cloop
Linux Compressed Loop image, useful only to reuse directly compressed
CD-ROM images present for example in the Knoppix CD-ROMs.
@item dmg
Apple disk image.
@item parallels
Parallels disk image format.
@end table


@node host_drives
@subsection Using host drives

In addition to disk image files, QEMU can directly access host
devices. We describe here the usage for QEMU version >= 0.8.3.

@subsubsection Linux

On Linux, you can directly use the host device filename instead of a
disk image filename provided you have enough privileges to access
it. For example, use @file{/dev/cdrom} to access to the CDROM.

@table @code
@item CD
You can specify a CDROM device even if no CDROM is loaded. QEMU has
specific code to detect CDROM insertion or removal. CDROM ejection by
the guest OS is supported. Currently only data CDs are supported.
@item Floppy
You can specify a floppy device even if no floppy is loaded. Floppy
removal is currently not detected accurately (if you change floppy
without doing floppy access while the floppy is not loaded, the guest
OS will think that the same floppy is loaded).
Use of the host's floppy device is deprecated, and support for it will
be removed in a future release.
@item Hard disks
Hard disks can be used. Normally you must specify the whole disk
(@file{/dev/hdb} instead of @file{/dev/hdb1}) so that the guest OS can
see it as a partitioned disk. WARNING: unless you know what you do, it
is better to only make READ-ONLY accesses to the hard disk otherwise
you may corrupt your host data (use the @option{-snapshot} command
line option or modify the device permissions accordingly).
@end table

@subsubsection Windows

@table @code
@item CD
The preferred syntax is the drive letter (e.g. @file{d:}). The
alternate syntax @file{\\.\d:} is supported. @file{/dev/cdrom} is
supported as an alias to the first CDROM drive.

Currently there is no specific code to handle removable media, so it
is better to use the @code{change} or @code{eject} monitor commands to
change or eject media.
@item Hard disks
Hard disks can be used with the syntax: @file{\\.\PhysicalDrive@var{N}}
where @var{N} is the drive number (0 is the first hard disk).

WARNING: unless you know what you do, it is better to only make
READ-ONLY accesses to the hard disk otherwise you may corrupt your
host data (use the @option{-snapshot} command line so that the
modifications are written in a temporary file).
@end table


@subsubsection Mac OS X

@file{/dev/cdrom} is an alias to the first CDROM.

Currently there is no specific code to handle removable media, so it
is better to use the @code{change} or @code{eject} monitor commands to
change or eject media.

@node disk_images_fat_images
@subsection Virtual FAT disk images

QEMU can automatically create a virtual FAT disk image from a
directory tree. In order to use it, just type:

@example
qemu-system-i386 linux.img -hdb fat:/my_directory
@end example

Then you access access to all the files in the @file{/my_directory}
directory without having to copy them in a disk image or to export
them via SAMBA or NFS. The default access is @emph{read-only}.

Floppies can be emulated with the @code{:floppy:} option:

@example
qemu-system-i386 linux.img -fda fat:floppy:/my_directory
@end example

A read/write support is available for testing (beta stage) with the
@code{:rw:} option:

@example
qemu-system-i386 linux.img -fda fat:floppy:rw:/my_directory
@end example

What you should @emph{never} do:
@itemize
@item use non-ASCII filenames ;
@item use "-snapshot" together with ":rw:" ;
@item expect it to work when loadvm'ing ;
@item write to the FAT directory on the host system while accessing it with the guest system.
@end itemize

@node disk_images_nbd
@subsection NBD access

QEMU can access directly to block device exported using the Network Block Device
protocol.

@example
qemu-system-i386 linux.img -hdb nbd://my_nbd_server.mydomain.org:1024/
@end example

If the NBD server is located on the same host, you can use an unix socket instead
of an inet socket:

@example
qemu-system-i386 linux.img -hdb nbd+unix://?socket=/tmp/my_socket
@end example

In this case, the block device must be exported using qemu-nbd:

@example
qemu-nbd --socket=/tmp/my_socket my_disk.qcow2
@end example

The use of qemu-nbd allows sharing of a disk between several guests:
@example
qemu-nbd --socket=/tmp/my_socket --share=2 my_disk.qcow2
@end example

@noindent
and then you can use it with two guests:
@example
qemu-system-i386 linux1.img -hdb nbd+unix://?socket=/tmp/my_socket
qemu-system-i386 linux2.img -hdb nbd+unix://?socket=/tmp/my_socket
@end example

If the nbd-server uses named exports (supported since NBD 2.9.18, or with QEMU's
own embedded NBD server), you must specify an export name in the URI:
@example
qemu-system-i386 -cdrom nbd://localhost/debian-500-ppc-netinst
qemu-system-i386 -cdrom nbd://localhost/openSUSE-11.1-ppc-netinst
@end example

The URI syntax for NBD is supported since QEMU 1.3.  An alternative syntax is
also available.  Here are some example of the older syntax:
@example
qemu-system-i386 linux.img -hdb nbd:my_nbd_server.mydomain.org:1024
qemu-system-i386 linux2.img -hdb nbd:unix:/tmp/my_socket
qemu-system-i386 -cdrom nbd:localhost:10809:exportname=debian-500-ppc-netinst
@end example

@node disk_images_sheepdog
@subsection Sheepdog disk images

Sheepdog is a distributed storage system for QEMU.  It provides highly
available block level storage volumes that can be attached to
QEMU-based virtual machines.

You can create a Sheepdog disk image with the command:
@example
qemu-img create sheepdog:///@var{image} @var{size}
@end example
where @var{image} is the Sheepdog image name and @var{size} is its
size.

To import the existing @var{filename} to Sheepdog, you can use a
convert command.
@example
qemu-img convert @var{filename} sheepdog:///@var{image}
@end example

You can boot from the Sheepdog disk image with the command:
@example
qemu-system-i386 sheepdog:///@var{image}
@end example

You can also create a snapshot of the Sheepdog image like qcow2.
@example
qemu-img snapshot -c @var{tag} sheepdog:///@var{image}
@end example
where @var{tag} is a tag name of the newly created snapshot.

To boot from the Sheepdog snapshot, specify the tag name of the
snapshot.
@example
qemu-system-i386 sheepdog:///@var{image}#@var{tag}
@end example

You can create a cloned image from the existing snapshot.
@example
qemu-img create -b sheepdog:///@var{base}#@var{tag} sheepdog:///@var{image}
@end example
where @var{base} is a image name of the source snapshot and @var{tag}
is its tag name.

You can use an unix socket instead of an inet socket:

@example
qemu-system-i386 sheepdog+unix:///@var{image}?socket=@var{path}
@end example

If the Sheepdog daemon doesn't run on the local host, you need to
specify one of the Sheepdog servers to connect to.
@example
qemu-img create sheepdog://@var{hostname}:@var{port}/@var{image} @var{size}
qemu-system-i386 sheepdog://@var{hostname}:@var{port}/@var{image}
@end example

@node disk_images_iscsi
@subsection iSCSI LUNs

iSCSI is a popular protocol used to access SCSI devices across a computer
network.

There are two different ways iSCSI devices can be used by QEMU.

The first method is to mount the iSCSI LUN on the host, and make it appear as
any other ordinary SCSI device on the host and then to access this device as a
/dev/sd device from QEMU. How to do this differs between host OSes.

The second method involves using the iSCSI initiator that is built into
QEMU. This provides a mechanism that works the same way regardless of which
host OS you are running QEMU on. This section will describe this second method
of using iSCSI together with QEMU.

In QEMU, iSCSI devices are described using special iSCSI URLs

@example
URL syntax:
iscsi://[<username>[%<password>]@@]<host>[:<port>]/<target-iqn-name>/<lun>
@end example

Username and password are optional and only used if your target is set up
using CHAP authentication for access control.
Alternatively the username and password can also be set via environment
variables to have these not show up in the process list

@example
export LIBISCSI_CHAP_USERNAME=<username>
export LIBISCSI_CHAP_PASSWORD=<password>
iscsi://<host>/<target-iqn-name>/<lun>
@end example

Various session related parameters can be set via special options, either
in a configuration file provided via '-readconfig' or directly on the
command line.

If the initiator-name is not specified qemu will use a default name
of 'iqn.2008-11.org.linux-kvm[:<name>'] where <name> is the name of the
virtual machine.


@example
Setting a specific initiator name to use when logging in to the target
-iscsi initiator-name=iqn.qemu.test:my-initiator
@end example

@example
Controlling which type of header digest to negotiate with the target
-iscsi header-digest=CRC32C|CRC32C-NONE|NONE-CRC32C|NONE
@end example

These can also be set via a configuration file
@example
[iscsi]
  user = "CHAP username"
  password = "CHAP password"
  initiator-name = "iqn.qemu.test:my-initiator"
  # header digest is one of CRC32C|CRC32C-NONE|NONE-CRC32C|NONE
  header-digest = "CRC32C"
@end example


Setting the target name allows different options for different targets
@example
[iscsi "iqn.target.name"]
  user = "CHAP username"
  password = "CHAP password"
  initiator-name = "iqn.qemu.test:my-initiator"
  # header digest is one of CRC32C|CRC32C-NONE|NONE-CRC32C|NONE
  header-digest = "CRC32C"
@end example


Howto use a configuration file to set iSCSI configuration options:
@example
cat >iscsi.conf <<EOF
[iscsi]
  user = "me"
  password = "my password"
  initiator-name = "iqn.qemu.test:my-initiator"
  header-digest = "CRC32C"
EOF

qemu-system-i386 -drive file=iscsi://127.0.0.1/iqn.qemu.test/1 \
    -readconfig iscsi.conf
@end example


Howto set up a simple iSCSI target on loopback and accessing it via QEMU:
@example
This example shows how to set up an iSCSI target with one CDROM and one DISK
using the Linux STGT software target. This target is available on Red Hat based
systems as the package 'scsi-target-utils'.

tgtd --iscsi portal=127.0.0.1:3260
tgtadm --lld iscsi --op new --mode target --tid 1 -T iqn.qemu.test
tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 1 \
    -b /IMAGES/disk.img --device-type=disk
tgtadm --lld iscsi --mode logicalunit --op new --tid 1 --lun 2 \
    -b /IMAGES/cd.iso --device-type=cd
tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL

qemu-system-i386 -iscsi initiator-name=iqn.qemu.test:my-initiator \
    -boot d -drive file=iscsi://127.0.0.1/iqn.qemu.test/1 \
    -cdrom iscsi://127.0.0.1/iqn.qemu.test/2
@end example

@node disk_images_gluster
@subsection GlusterFS disk images

GlusterFS is a user space distributed file system.

You can boot from the GlusterFS disk image with the command:
@example
URI:
qemu-system-x86_64 -drive file=gluster[+@var{type}]://[@var{host}[:@var{port}]]/@var{volume}/@var{path}
                               [?socket=...][,file.debug=9][,file.logfile=...]

JSON:
qemu-system-x86_64 'json:@{"driver":"qcow2",
                           "file":@{"driver":"gluster",
                                    "volume":"testvol","path":"a.img","debug":9,"logfile":"...",
                                    "server":[@{"type":"tcp","host":"...","port":"..."@},
                                              @{"type":"unix","socket":"..."@}]@}@}'
@end example

@var{gluster} is the protocol.

@var{type} specifies the transport type used to connect to gluster
management daemon (glusterd). Valid transport types are
tcp and unix. In the URI form, if a transport type isn't specified,
then tcp type is assumed.

@var{host} specifies the server where the volume file specification for
the given volume resides. This can be either a hostname or an ipv4 address.
If transport type is unix, then @var{host} field should not be specified.
Instead @var{socket} field needs to be populated with the path to unix domain
socket.

@var{port} is the port number on which glusterd is listening. This is optional
and if not specified, it defaults to port 24007. If the transport type is unix,
then @var{port} should not be specified.

@var{volume} is the name of the gluster volume which contains the disk image.

@var{path} is the path to the actual disk image that resides on gluster volume.

@var{debug} is the logging level of the gluster protocol driver. Debug levels
are 0-9, with 9 being the most verbose, and 0 representing no debugging output.
The default level is 4. The current logging levels defined in the gluster source
are 0 - None, 1 - Emergency, 2 - Alert, 3 - Critical, 4 - Error, 5 - Warning,
6 - Notice, 7 - Info, 8 - Debug, 9 - Trace

@var{logfile} is a commandline option to mention log file path which helps in
logging to the specified file and also help in persisting the gfapi logs. The
default is stderr.




You can create a GlusterFS disk image with the command:
@example
qemu-img create gluster://@var{host}/@var{volume}/@var{path} @var{size}
@end example

Examples
@example
qemu-system-x86_64 -drive file=gluster://1.2.3.4/testvol/a.img
qemu-system-x86_64 -drive file=gluster+tcp://1.2.3.4/testvol/a.img
qemu-system-x86_64 -drive file=gluster+tcp://1.2.3.4:24007/testvol/dir/a.img
qemu-system-x86_64 -drive file=gluster+tcp://[1:2:3:4:5:6:7:8]/testvol/dir/a.img
qemu-system-x86_64 -drive file=gluster+tcp://[1:2:3:4:5:6:7:8]:24007/testvol/dir/a.img
qemu-system-x86_64 -drive file=gluster+tcp://server.domain.com:24007/testvol/dir/a.img
qemu-system-x86_64 -drive file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glusterd.socket
qemu-system-x86_64 -drive file=gluster+rdma://1.2.3.4:24007/testvol/a.img
qemu-system-x86_64 -drive file=gluster://1.2.3.4/testvol/a.img,file.debug=9,file.logfile=/var/log/qemu-gluster.log
qemu-system-x86_64 'json:@{"driver":"qcow2",
                           "file":@{"driver":"gluster",
                                    "volume":"testvol","path":"a.img",
                                    "debug":9,"logfile":"/var/log/qemu-gluster.log",
                                    "server":[@{"type":"tcp","host":"1.2.3.4","port":24007@},
                                              @{"type":"unix","socket":"/var/run/glusterd.socket"@}]@}@}'
qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
                                       file.debug=9,file.logfile=/var/log/qemu-gluster.log,
                                       file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
                                       file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket
@end example

@node disk_images_ssh
@subsection Secure Shell (ssh) disk images

You can access disk images located on a remote ssh server
by using the ssh protocol:

@example
qemu-system-x86_64 -drive file=ssh://[@var{user}@@]@var{server}[:@var{port}]/@var{path}[?host_key_check=@var{host_key_check}]
@end example

Alternative syntax using properties:

@example
qemu-system-x86_64 -drive file.driver=ssh[,file.user=@var{user}],file.host=@var{server}[,file.port=@var{port}],file.path=@var{path}[,file.host_key_check=@var{host_key_check}]
@end example

@var{ssh} is the protocol.

@var{user} is the remote user.  If not specified, then the local
username is tried.

@var{server} specifies the remote ssh server.  Any ssh server can be
used, but it must implement the sftp-server protocol.  Most Unix/Linux
systems should work without requiring any extra configuration.

@var{port} is the port number on which sshd is listening.  By default
the standard ssh port (22) is used.

@var{path} is the path to the disk image.

The optional @var{host_key_check} parameter controls how the remote
host's key is checked.  The default is @code{yes} which means to use
the local @file{.ssh/known_hosts} file.  Setting this to @code{no}
turns off known-hosts checking.  Or you can check that the host key
matches a specific fingerprint:
@code{host_key_check=md5:78:45:8e:14:57:4f:d5:45:83:0a:0e:f3:49:82:c9:c8}
(@code{sha1:} can also be used as a prefix, but note that OpenSSH
tools only use MD5 to print fingerprints).

Currently authentication must be done using ssh-agent.  Other
authentication methods may be supported in future.

Note: Many ssh servers do not support an @code{fsync}-style operation.
The ssh driver cannot guarantee that disk flush requests are
obeyed, and this causes a risk of disk corruption if the remote
server or network goes down during writes.  The driver will
print a warning when @code{fsync} is not supported:

warning: ssh server @code{ssh.example.com:22} does not support fsync

With sufficiently new versions of libssh2 and OpenSSH, @code{fsync} is
supported.

@node pcsys_network
@section Network emulation

QEMU can simulate several network cards (PCI or ISA cards on the PC
target) and can connect them to an arbitrary number of Virtual Local
Area Networks (VLANs). Host TAP devices can be connected to any QEMU
VLAN. VLAN can be connected between separate instances of QEMU to
simulate large networks. For simpler usage, a non privileged user mode
network stack can replace the TAP device to have a basic network
connection.

@subsection VLANs

QEMU simulates several VLANs. A VLAN can be symbolised as a virtual
connection between several network devices. These devices can be for
example QEMU virtual Ethernet cards or virtual Host ethernet devices
(TAP devices).

@subsection Using TAP network interfaces

This is the standard way to connect QEMU to a real network. QEMU adds
a virtual network device on your host (called @code{tapN}), and you
can then configure it as if it was a real ethernet card.

@subsubsection Linux host

As an example, you can download the @file{linux-test-xxx.tar.gz}
archive and copy the script @file{qemu-ifup} in @file{/etc} and
configure properly @code{sudo} so that the command @code{ifconfig}
contained in @file{qemu-ifup} can be executed as root. You must verify
that your host kernel supports the TAP network interfaces: the
device @file{/dev/net/tun} must be present.

See @ref{sec_invocation} to have examples of command lines using the
TAP network interfaces.

@subsubsection Windows host

There is a virtual ethernet driver for Windows 2000/XP systems, called
TAP-Win32. But it is not included in standard QEMU for Windows,
so you will need to get it separately. It is part of OpenVPN package,
so download OpenVPN from : @url{http://openvpn.net/}.

@subsection Using the user mode network stack

By using the option @option{-net user} (default configuration if no
@option{-net} option is specified), QEMU uses a completely user mode
network stack (you don't need root privilege to use the virtual
network). The virtual network configuration is the following:

@example

         QEMU VLAN      <------>  Firewall/DHCP server <-----> Internet
                           |          (10.0.2.2)
                           |
                           ---->  DNS server (10.0.2.3)
                           |
                           ---->  SMB server (10.0.2.4)
@end example

The QEMU VM behaves as if it was behind a firewall which blocks all
incoming connections. You can use a DHCP client to automatically
configure the network in the QEMU VM. The DHCP server assign addresses
to the hosts starting from 10.0.2.15.

In order to check that the user mode network is working, you can ping
the address 10.0.2.2 and verify that you got an address in the range
10.0.2.x from the QEMU virtual DHCP server.

Note that ICMP traffic in general does not work with user mode networking.
@code{ping}, aka. ICMP echo, to the local router (10.0.2.2) shall work,
however. If you're using QEMU on Linux >= 3.0, it can use unprivileged ICMP
ping sockets to allow @code{ping} to the Internet. The host admin has to set
the ping_group_range in order to grant access to those sockets. To allow ping
for GID 100 (usually users group):

@example
echo 100 100 > /proc/sys/net/ipv4/ping_group_range
@end example

When using the built-in TFTP server, the router is also the TFTP
server.

When using the @option{'-netdev user,hostfwd=...'} option, TCP or UDP
connections can be redirected from the host to the guest. It allows for
example to redirect X11, telnet or SSH connections.

@subsection Connecting VLANs between QEMU instances

Using the @option{-net socket} option, it is possible to make VLANs
that span several QEMU instances. See @ref{sec_invocation} to have a
basic example.

@node pcsys_other_devs
@section Other Devices

@subsection Inter-VM Shared Memory device

On Linux hosts, a shared memory device is available.  The basic syntax
is:

@example
qemu-system-x86_64 -device ivshmem-plain,memdev=@var{hostmem}
@end example

where @var{hostmem} names a host memory backend.  For a POSIX shared
memory backend, use something like

@example
-object memory-backend-file,size=1M,share,mem-path=/dev/shm/ivshmem,id=@var{hostmem}
@end example

If desired, interrupts can be sent between guest VMs accessing the same shared
memory region.  Interrupt support requires using a shared memory server and
using a chardev socket to connect to it.  The code for the shared memory server
is qemu.git/contrib/ivshmem-server.  An example syntax when using the shared
memory server is:

@example
# First start the ivshmem server once and for all
ivshmem-server -p @var{pidfile} -S @var{path} -m @var{shm-name} -l @var{shm-size} -n @var{vectors}

# Then start your qemu instances with matching arguments
qemu-system-x86_64 -device ivshmem-doorbell,vectors=@var{vectors},chardev=@var{id}
                 -chardev socket,path=@var{path},id=@var{id}
@end example

When using the server, the guest will be assigned a VM ID (>=0) that allows guests
using the same server to communicate via interrupts.  Guests can read their
VM ID from a device register (see ivshmem-spec.txt).

@subsubsection Migration with ivshmem

With device property @option{master=on}, the guest will copy the shared
memory on migration to the destination host.  With @option{master=off},
the guest will not be able to migrate with the device attached.  In the
latter case, the device should be detached and then reattached after
migration using the PCI hotplug support.

At most one of the devices sharing the same memory can be master.  The
master must complete migration before you plug back the other devices.

@subsubsection ivshmem and hugepages

Instead of specifying the <shm size> using POSIX shm, you may specify
a memory backend that has hugepage support:

@example
qemu-system-x86_64 -object memory-backend-file,size=1G,mem-path=/dev/hugepages/my-shmem-file,share,id=mb1
                 -device ivshmem-plain,memdev=mb1
@end example

ivshmem-server also supports hugepages mount points with the
@option{-m} memory path argument.

@node direct_linux_boot
@section Direct Linux Boot

This section explains how to launch a Linux kernel inside QEMU without
having to make a full bootable image. It is very useful for fast Linux
kernel testing.

The syntax is:
@example
qemu-system-i386 -kernel arch/i386/boot/bzImage -hda root-2.4.20.img -append "root=/dev/hda"
@end example

Use @option{-kernel} to provide the Linux kernel image and
@option{-append} to give the kernel command line arguments. The
@option{-initrd} option can be used to provide an INITRD image.

When using the direct Linux boot, a disk image for the first hard disk
@file{hda} is required because its boot sector is used to launch the
Linux kernel.

If you do not need graphical output, you can disable it and redirect
the virtual serial port and the QEMU monitor to the console with the
@option{-nographic} option. The typical command line is:
@example
qemu-system-i386 -kernel arch/i386/boot/bzImage -hda root-2.4.20.img \
                 -append "root=/dev/hda console=ttyS0" -nographic
@end example

Use @key{Ctrl-a c} to switch between the serial console and the
monitor (@pxref{pcsys_keys}).

@node pcsys_usb
@section USB emulation

QEMU can emulate a PCI UHCI, OHCI, EHCI or XHCI USB controller. You can
plug virtual USB devices or real host USB devices (only works with certain
host operating systems). QEMU will automatically create and connect virtual
USB hubs as necessary to connect multiple USB devices.

@menu
* usb_devices::
* host_usb_devices::
@end menu
@node usb_devices
@subsection Connecting USB devices

USB devices can be connected with the @option{-device usb-...} command line
option or the @code{device_add} monitor command. Available devices are:

@table @code
@item usb-mouse
Virtual Mouse.  This will override the PS/2 mouse emulation when activated.
@item usb-tablet
Pointer device that uses absolute coordinates (like a touchscreen).
This means QEMU is able to report the mouse position without having
to grab the mouse.  Also overrides the PS/2 mouse emulation when activated.
@item usb-storage,drive=@var{drive_id}
Mass storage device backed by @var{drive_id} (@pxref{disk_images})
@item usb-uas
USB attached SCSI device, see
@url{http://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/usb-storage.txt,usb-storage.txt}
for details
@item usb-bot
Bulk-only transport storage device, see
@url{http://git.qemu.org/?p=qemu.git;a=blob_plain;f=docs/usb-storage.txt,usb-storage.txt}
for details here, too
@item usb-mtp,x-root=@var{dir}
Media transfer protocol device, using @var{dir} as root of the file tree
that is presented to the guest.
@item usb-host,hostbus=@var{bus},hostaddr=@var{addr}
Pass through the host device identified by @var{bus} and @var{addr}
@item usb-host,vendorid=@var{vendor},productid=@var{product}
Pass through the host device identified by @var{vendor} and @var{product} ID
@item usb-wacom-tablet
Virtual Wacom PenPartner tablet.  This device is similar to the @code{tablet}
above but it can be used with the tslib library because in addition to touch
coordinates it reports touch pressure.
@item usb-kbd
Standard USB keyboard.  Will override the PS/2 keyboard (if present).
@item usb-serial,chardev=@var{id}
Serial converter. This emulates an FTDI FT232BM chip connected to host character
device @var{id}.
@item usb-braille,chardev=@var{id}
Braille device.  This will use BrlAPI to display the braille output on a real
or fake device referenced by @var{id}.
@item usb-net[,netdev=@var{id}]
Network adapter that supports CDC ethernet and RNDIS protocols.  @var{id}
specifies a netdev defined with @code{-netdev @dots{},id=@var{id}}.
For instance, user-mode networking can be used with
@example
qemu-system-i386 [...] -netdev user,id=net0 -device usb-net,netdev=net0
@end example
@item usb-ccid
Smartcard reader device
@item usb-audio
USB audio device
@item usb-bt-dongle
Bluetooth dongle for the transport layer of HCI. It is connected to HCI
scatternet 0 by default (corresponds to @code{-bt hci,vlan=0}).
Note that the syntax for the @code{-device usb-bt-dongle} option is not as
useful yet as it was with the legacy @code{-usbdevice} option. So to
configure an USB bluetooth device, you might need to use
"@code{-usbdevice bt}[:@var{hci-type}]" instead. This configures a
bluetooth dongle whose type is specified in the same format as with
the @option{-bt hci} option, @pxref{bt-hcis,,allowed HCI types}.  If
no type is given, the HCI logic corresponds to @code{-bt hci,vlan=0}.
This USB device implements the USB Transport Layer of HCI.  Example
usage:
@example
@command{qemu-system-i386} [...@var{OPTIONS}...] @option{-usbdevice} bt:hci,vlan=3 @option{-bt} device:keyboard,vlan=3
@end example
@end table

@node host_usb_devices
@subsection Using host USB devices on a Linux host

WARNING: this is an experimental feature. QEMU will slow down when
using it. USB devices requiring real time streaming (i.e. USB Video
Cameras) are not supported yet.

@enumerate
@item If you use an early Linux 2.4 kernel, verify that no Linux driver
is actually using the USB device. A simple way to do that is simply to
disable the corresponding kernel module by renaming it from @file{mydriver.o}
to @file{mydriver.o.disabled}.

@item Verify that @file{/proc/bus/usb} is working (most Linux distributions should enable it by default). You should see something like that:
@example
ls /proc/bus/usb
001  devices  drivers
@end example

@item Since only root can access to the USB devices directly, you can either launch QEMU as root or change the permissions of the USB devices you want to use. For testing, the following suffices:
@example
chown -R myuid /proc/bus/usb
@end example

@item Launch QEMU and do in the monitor:
@example
info usbhost
  Device 1.2, speed 480 Mb/s
    Class 00: USB device 1234:5678, USB DISK
@end example
You should see the list of the devices you can use (Never try to use
hubs, it won't work).

@item Add the device in QEMU by using:
@example
device_add usb-host,vendorid=0x1234,productid=0x5678
@end example

Normally the guest OS should report that a new USB device is plugged.
You can use the option @option{-device usb-host,...} to do the same.

@item Now you can try to use the host USB device in QEMU.

@end enumerate

When relaunching QEMU, you may have to unplug and plug again the USB
device to make it work again (this is a bug).

@node vnc_security
@section VNC security

The VNC server capability provides access to the graphical console
of the guest VM across the network. This has a number of security
considerations depending on the deployment scenarios.

@menu
* vnc_sec_none::
* vnc_sec_password::
* vnc_sec_certificate::
* vnc_sec_certificate_verify::
* vnc_sec_certificate_pw::
* vnc_sec_sasl::
* vnc_sec_certificate_sasl::
* vnc_generate_cert::
* vnc_setup_sasl::
@end menu
@node vnc_sec_none
@subsection Without passwords

The simplest VNC server setup does not include any form of authentication.
For this setup it is recommended to restrict it to listen on a UNIX domain
socket only. For example

@example
qemu-system-i386 [...OPTIONS...] -vnc unix:/home/joebloggs/.qemu-myvm-vnc
@end example

This ensures that only users on local box with read/write access to that
path can access the VNC server. To securely access the VNC server from a
remote machine, a combination of netcat+ssh can be used to provide a secure
tunnel.

@node vnc_sec_password
@subsection With passwords

The VNC protocol has limited support for password based authentication. Since
the protocol limits passwords to 8 characters it should not be considered
to provide high security. The password can be fairly easily brute-forced by
a client making repeat connections. For this reason, a VNC server using password
authentication should be restricted to only listen on the loopback interface
or UNIX domain sockets. Password authentication is not supported when operating
in FIPS 140-2 compliance mode as it requires the use of the DES cipher. Password
authentication is requested with the @code{password} option, and then once QEMU
is running the password is set with the monitor. Until the monitor is used to
set the password all clients will be rejected.

@example
qemu-system-i386 [...OPTIONS...] -vnc :1,password -monitor stdio
(qemu) change vnc password
Password: ********
(qemu)
@end example

@node vnc_sec_certificate
@subsection With x509 certificates

The QEMU VNC server also implements the VeNCrypt extension allowing use of
TLS for encryption of the session, and x509 certificates for authentication.
The use of x509 certificates is strongly recommended, because TLS on its
own is susceptible to man-in-the-middle attacks. Basic x509 certificate
support provides a secure session, but no authentication. This allows any
client to connect, and provides an encrypted session.

@example
qemu-system-i386 [...OPTIONS...] -vnc :1,tls,x509=/etc/pki/qemu -monitor stdio
@end example

In the above example @code{/etc/pki/qemu} should contain at least three files,
@code{ca-cert.pem}, @code{server-cert.pem} and @code{server-key.pem}. Unprivileged
users will want to use a private directory, for example @code{$HOME/.pki/qemu}.
NB the @code{server-key.pem} file should be protected with file mode 0600 to
only be readable by the user owning it.

@node vnc_sec_certificate_verify
@subsection With x509 certificates and client verification

Certificates can also provide a means to authenticate the client connecting.
The server will request that the client provide a certificate, which it will
then validate against the CA certificate. This is a good choice if deploying
in an environment with a private internal certificate authority.

@example
qemu-system-i386 [...OPTIONS...] -vnc :1,tls,x509verify=/etc/pki/qemu -monitor stdio
@end example


@node vnc_sec_certificate_pw
@subsection With x509 certificates, client verification and passwords

Finally, the previous method can be combined with VNC password authentication
to provide two layers of authentication for clients.

@example
qemu-system-i386 [...OPTIONS...] -vnc :1,password,tls,x509verify=/etc/pki/qemu -monitor stdio
(qemu) change vnc password
Password: ********
(qemu)
@end example


@node vnc_sec_sasl
@subsection With SASL authentication

The SASL authentication method is a VNC extension, that provides an
easily extendable, pluggable authentication method. This allows for
integration with a wide range of authentication mechanisms, such as
PAM, GSSAPI/Kerberos, LDAP, SQL databases, one-time keys and more.
The strength of the authentication depends on the exact mechanism
configured. If the chosen mechanism also provides a SSF layer, then
it will encrypt the datastream as well.

Refer to the later docs on how to choose the exact SASL mechanism
used for authentication, but assuming use of one supporting SSF,
then QEMU can be launched with:

@example
qemu-system-i386 [...OPTIONS...] -vnc :1,sasl -monitor stdio
@end example

@node vnc_sec_certificate_sasl
@subsection With x509 certificates and SASL authentication

If the desired SASL authentication mechanism does not supported
SSF layers, then it is strongly advised to run it in combination
with TLS and x509 certificates. This provides securely encrypted
data stream, avoiding risk of compromising of the security
credentials. This can be enabled, by combining the 'sasl' option
with the aforementioned TLS + x509 options:

@example
qemu-system-i386 [...OPTIONS...] -vnc :1,tls,x509,sasl -monitor stdio
@end example


@node vnc_generate_cert
@subsection Generating certificates for VNC

The GNU TLS packages provides a command called @code{certtool} which can
be used to generate certificates and keys in PEM format. At a minimum it
is necessary to setup a certificate authority, and issue certificates to
each server. If using certificates for authentication, then each client
will also need to be issued a certificate. The recommendation is for the
server to keep its certificates in either @code{/etc/pki/qemu} or for
unprivileged users in @code{$HOME/.pki/qemu}.

@menu
* vnc_generate_ca::
* vnc_generate_server::
* vnc_generate_client::
@end menu
@node vnc_generate_ca
@subsubsection Setup the Certificate Authority

This step only needs to be performed once per organization / organizational
unit. First the CA needs a private key. This key must be kept VERY secret
and secure. If this key is compromised the entire trust chain of the certificates
issued with it is lost.

@example
# certtool --generate-privkey > ca-key.pem
@end example

A CA needs to have a public certificate. For simplicity it can be a self-signed
certificate, or one issue by a commercial certificate issuing authority. To
generate a self-signed certificate requires one core piece of information, the
name of the organization.

@example
# cat > ca.info <<EOF
cn = Name of your organization
ca
cert_signing_key
EOF
# certtool --generate-self-signed \
           --load-privkey ca-key.pem
           --template ca.info \
           --outfile ca-cert.pem
@end example

The @code{ca-cert.pem} file should be copied to all servers and clients wishing to utilize
TLS support in the VNC server. The @code{ca-key.pem} must not be disclosed/copied at all.

@node vnc_generate_server
@subsubsection Issuing server certificates

Each server (or host) needs to be issued with a key and certificate. When connecting
the certificate is sent to the client which validates it against the CA certificate.
The core piece of information for a server certificate is the hostname. This should
be the fully qualified hostname that the client will connect with, since the client
will typically also verify the hostname in the certificate. On the host holding the
secure CA private key:

@example
# cat > server.info <<EOF
organization = Name  of your organization
cn = server.foo.example.com
tls_www_server
encryption_key
signing_key
EOF
# certtool --generate-privkey > server-key.pem
# certtool --generate-certificate \
           --load-ca-certificate ca-cert.pem \
           --load-ca-privkey ca-key.pem \
           --load-privkey server-key.pem \
           --template server.info \
           --outfile server-cert.pem
@end example

The @code{server-key.pem} and @code{server-cert.pem} files should now be securely copied
to the server for which they were generated. The @code{server-key.pem} is security
sensitive and should be kept protected with file mode 0600 to prevent disclosure.

@node vnc_generate_client
@subsubsection Issuing client certificates

If the QEMU VNC server is to use the @code{x509verify} option to validate client
certificates as its authentication mechanism, each client also needs to be issued
a certificate. The client certificate contains enough metadata to uniquely identify
the client, typically organization, state, city, building, etc. On the host holding
the secure CA private key:

@example
# cat > client.info <<EOF
country = GB
state = London
locality = London
organization = Name of your organization
cn = client.foo.example.com
tls_www_client
encryption_key
signing_key
EOF
# certtool --generate-privkey > client-key.pem
# certtool --generate-certificate \
           --load-ca-certificate ca-cert.pem \
           --load-ca-privkey ca-key.pem \
           --load-privkey client-key.pem \
           --template client.info \
           --outfile client-cert.pem
@end example

The @code{client-key.pem} and @code{client-cert.pem} files should now be securely
copied to the client for which they were generated.


@node vnc_setup_sasl

@subsection Configuring SASL mechanisms

The following documentation assumes use of the Cyrus SASL implementation on a
Linux host, but the principals should apply to any other SASL impl. When SASL
is enabled, the mechanism configuration will be loaded from system default
SASL service config /etc/sasl2/qemu.conf. If running QEMU as an
unprivileged user, an environment variable SASL_CONF_PATH can be used
to make it search alternate locations for the service config.

If the TLS option is enabled for VNC, then it will provide session encryption,
otherwise the SASL mechanism will have to provide encryption. In the latter
case the list of possible plugins that can be used is drastically reduced. In
fact only the GSSAPI SASL mechanism provides an acceptable level of security
by modern standards. Previous versions of QEMU referred to the DIGEST-MD5
mechanism, however, it has multiple serious flaws described in detail in
RFC 6331 and thus should never be used any more. The SCRAM-SHA-1 mechanism
provides a simple username/password auth facility similar to DIGEST-MD5, but
does not support session encryption, so can only be used in combination with
TLS.

When not using TLS the recommended configuration is

@example
mech_list: gssapi
keytab: /etc/qemu/krb5.tab
@end example

This says to use the 'GSSAPI' mechanism with the Kerberos v5 protocol, with
the server principal stored in /etc/qemu/krb5.tab. For this to work the
administrator of your KDC must generate a Kerberos principal for the server,
with a name of 'qemu/somehost.example.com@@EXAMPLE.COM' replacing
'somehost.example.com' with the fully qualified host name of the machine
running QEMU, and 'EXAMPLE.COM' with the Kerberos Realm.

When using TLS, if username+password authentication is desired, then a
reasonable configuration is

@example
mech_list: scram-sha-1
sasldb_path: /etc/qemu/passwd.db
@end example

The saslpasswd2 program can be used to populate the passwd.db file with
accounts.

Other SASL configurations will be left as an exercise for the reader. Note that
all mechanisms except GSSAPI, should be combined with use of TLS to ensure a
secure data channel.

@node gdb_usage
@section GDB usage

QEMU has a primitive support to work with gdb, so that you can do
'Ctrl-C' while the virtual machine is running and inspect its state.

In order to use gdb, launch QEMU with the '-s' option. It will wait for a
gdb connection:
@example
qemu-system-i386 -s -kernel arch/i386/boot/bzImage -hda root-2.4.20.img \
                    -append "root=/dev/hda"
Connected to host network interface: tun0
Waiting gdb connection on port 1234
@end example

Then launch gdb on the 'vmlinux' executable:
@example
> gdb vmlinux
@end example

In gdb, connect to QEMU:
@example
(gdb) target remote localhost:1234
@end example

Then you can use gdb normally. For example, type 'c' to launch the kernel:
@example
(gdb) c
@end example

Here are some useful tips in order to use gdb on system code:

@enumerate
@item
Use @code{info reg} to display all the CPU registers.
@item
Use @code{x/10i $eip} to display the code at the PC position.
@item
Use @code{set architecture i8086} to dump 16 bit code. Then use
@code{x/10i $cs*16+$eip} to dump the code at the PC position.
@end enumerate

Advanced debugging options:

The default single stepping behavior is step with the IRQs and timer service routines off.  It is set this way because when gdb executes a single step it expects to advance beyond the current instruction.  With the IRQs and timer service routines on, a single step might jump into the one of the interrupt or exception vectors instead of executing the current instruction. This means you may hit the same breakpoint a number of times before executing the instruction gdb wants to have executed.  Because there are rare circumstances where you want to single step into an interrupt vector the behavior can be controlled from GDB.  There are three commands you can query and set the single step behavior:
@table @code
@item maintenance packet qqemu.sstepbits

This will display the MASK bits used to control the single stepping IE:
@example
(gdb) maintenance packet qqemu.sstepbits
sending: "qqemu.sstepbits"
received: "ENABLE=1,NOIRQ=2,NOTIMER=4"
@end example
@item maintenance packet qqemu.sstep

This will display the current value of the mask used when single stepping IE:
@example
(gdb) maintenance packet qqemu.sstep
sending: "qqemu.sstep"
received: "0x7"
@end example
@item maintenance packet Qqemu.sstep=HEX_VALUE

This will change the single step mask, so if wanted to enable IRQs on the single step, but not timers, you would use:
@example
(gdb) maintenance packet Qqemu.sstep=0x5
sending: "qemu.sstep=0x5"
received: "OK"
@end example
@end table

@node pcsys_os_specific
@section Target OS specific information

@subsection Linux

To have access to SVGA graphic modes under X11, use the @code{vesa} or
the @code{cirrus} X11 driver. For optimal performances, use 16 bit
color depth in the guest and the host OS.

When using a 2.6 guest Linux kernel, you should add the option
@code{clock=pit} on the kernel command line because the 2.6 Linux
kernels make very strict real time clock checks by default that QEMU
cannot simulate exactly.

When using a 2.6 guest Linux kernel, verify that the 4G/4G patch is
not activated because QEMU is slower with this patch. The QEMU
Accelerator Module is also much slower in this case. Earlier Fedora
Core 3 Linux kernel (< 2.6.9-1.724_FC3) were known to incorporate this
patch by default. Newer kernels don't have it.

@subsection Windows

If you have a slow host, using Windows 95 is better as it gives the
best speed. Windows 2000 is also a good choice.

@subsubsection SVGA graphic modes support

QEMU emulates a Cirrus Logic GD5446 Video
card. All Windows versions starting from Windows 95 should recognize
and use this graphic card. For optimal performances, use 16 bit color
depth in the guest and the host OS.

If you are using Windows XP as guest OS and if you want to use high
resolution modes which the Cirrus Logic BIOS does not support (i.e. >=
1280x1024x16), then you should use the VESA VBE virtual graphic card
(option @option{-std-vga}).

@subsubsection CPU usage reduction

Windows 9x does not correctly use the CPU HLT
instruction. The result is that it takes host CPU cycles even when
idle. You can install the utility from
@url{http://web.archive.org/web/20060212132151/http://www.user.cityline.ru/~maxamn/amnhltm.zip}
to solve this problem. Note that no such tool is needed for NT, 2000 or XP.

@subsubsection Windows 2000 disk full problem

Windows 2000 has a bug which gives a disk full problem during its
installation. When installing it, use the @option{-win2k-hack} QEMU
option to enable a specific workaround. After Windows 2000 is
installed, you no longer need this option (this option slows down the
IDE transfers).

@subsubsection Windows 2000 shutdown

Windows 2000 cannot automatically shutdown in QEMU although Windows 98
can. It comes from the fact that Windows 2000 does not automatically
use the APM driver provided by the BIOS.

In order to correct that, do the following (thanks to Struan
Bartlett): go to the Control Panel => Add/Remove Hardware & Next =>
Add/Troubleshoot a device => Add a new device & Next => No, select the
hardware from a list & Next => NT Apm/Legacy Support & Next => Next
(again) a few times. Now the driver is installed and Windows 2000 now
correctly instructs QEMU to shutdown at the appropriate moment.

@subsubsection Share a directory between Unix and Windows

See @ref{sec_invocation} about the help of the option
@option{'-netdev user,smb=...'}.

@subsubsection Windows XP security problem

Some releases of Windows XP install correctly but give a security
error when booting:
@example
A problem is preventing Windows from accurately checking the
license for this computer. Error code: 0x800703e6.
@end example

The workaround is to install a service pack for XP after a boot in safe
mode. Then reboot, and the problem should go away. Since there is no
network while in safe mode, its recommended to download the full
installation of SP1 or SP2 and transfer that via an ISO or using the
vvfat block device ("-hdb fat:directory_which_holds_the_SP").

@subsection MS-DOS and FreeDOS

@subsubsection CPU usage reduction

DOS does not correctly use the CPU HLT instruction. The result is that
it takes host CPU cycles even when idle. You can install the utility from
@url{http://web.archive.org/web/20051222085335/http://www.vmware.com/software/dosidle210.zip}
to solve this problem.

@node QEMU System emulator for non PC targets
@chapter QEMU System emulator for non PC targets

QEMU is a generic emulator and it emulates many non PC
machines. Most of the options are similar to the PC emulator. The
differences are mentioned in the following sections.

@menu
* PowerPC System emulator::
* Sparc32 System emulator::
* Sparc64 System emulator::
* MIPS System emulator::
* ARM System emulator::
* ColdFire System emulator::
* Cris System emulator::
* Microblaze System emulator::
* SH4 System emulator::
* Xtensa System emulator::
@end menu

@node PowerPC System emulator
@section PowerPC System emulator
@cindex system emulation (PowerPC)

Use the executable @file{qemu-system-ppc} to simulate a complete PREP
or PowerMac PowerPC system.

QEMU emulates the following PowerMac peripherals:

@itemize @minus
@item
UniNorth or Grackle PCI Bridge
@item
PCI VGA compatible card with VESA Bochs Extensions
@item
2 PMAC IDE interfaces with hard disk and CD-ROM support
@item
NE2000 PCI adapters
@item
Non Volatile RAM
@item
VIA-CUDA with ADB keyboard and mouse.
@end itemize

QEMU emulates the following PREP peripherals:

@itemize @minus
@item
PCI Bridge
@item
PCI VGA compatible card with VESA Bochs Extensions
@item
2 IDE interfaces with hard disk and CD-ROM support
@item
Floppy disk
@item
NE2000 network adapters
@item
Serial port
@item
PREP Non Volatile RAM
@item
PC compatible keyboard and mouse.
@end itemize

QEMU uses the Open Hack'Ware Open Firmware Compatible BIOS available at
@url{http://perso.magic.fr/l_indien/OpenHackWare/index.htm}.

Since version 0.9.1, QEMU uses OpenBIOS @url{http://www.openbios.org/}
for the g3beige and mac99 PowerMac machines. OpenBIOS is a free (GPL
v2) portable firmware implementation. The goal is to implement a 100%
IEEE 1275-1994 (referred to as Open Firmware) compliant firmware.

@c man begin OPTIONS

The following options are specific to the PowerPC emulation:

@table @option

@item -g @var{W}x@var{H}[x@var{DEPTH}]

Set the initial VGA graphic mode. The default is 800x600x32.

@item -prom-env @var{string}

Set OpenBIOS variables in NVRAM, for example:

@example
qemu-system-ppc -prom-env 'auto-boot?=false' \
 -prom-env 'boot-device=hd:2,\yaboot' \
 -prom-env 'boot-args=conf=hd:2,\yaboot.conf'
@end example

These variables are not used by Open Hack'Ware.

@end table

@c man end


More information is available at
@url{http://perso.magic.fr/l_indien/qemu-ppc/}.

@node Sparc32 System emulator
@section Sparc32 System emulator
@cindex system emulation (Sparc32)

Use the executable @file{qemu-system-sparc} to simulate the following
Sun4m architecture machines:
@itemize @minus
@item
SPARCstation 4
@item
SPARCstation 5
@item
SPARCstation 10
@item
SPARCstation 20
@item
SPARCserver 600MP
@item
SPARCstation LX
@item
SPARCstation Voyager
@item
SPARCclassic
@item
SPARCbook
@end itemize

The emulation is somewhat complete. SMP up to 16 CPUs is supported,
but Linux limits the number of usable CPUs to 4.

QEMU emulates the following sun4m peripherals:

@itemize @minus
@item
IOMMU
@item
TCX or cgthree Frame buffer
@item
Lance (Am7990) Ethernet
@item
Non Volatile RAM M48T02/M48T08
@item
Slave I/O: timers, interrupt controllers, Zilog serial ports, keyboard
and power/reset logic
@item
ESP SCSI controller with hard disk and CD-ROM support
@item
Floppy drive (not on SS-600MP)
@item
CS4231 sound device (only on SS-5, not working yet)
@end itemize

The number of peripherals is fixed in the architecture.  Maximum
memory size depends on the machine type, for SS-5 it is 256MB and for
others 2047MB.

Since version 0.8.2, QEMU uses OpenBIOS
@url{http://www.openbios.org/}. OpenBIOS is a free (GPL v2) portable
firmware implementation. The goal is to implement a 100% IEEE
1275-1994 (referred to as Open Firmware) compliant firmware.

A sample Linux 2.6 series kernel and ram disk image are available on
the QEMU web site. There are still issues with NetBSD and OpenBSD, but
most kernel versions work. Please note that currently older Solaris kernels
don't work probably due to interface issues between OpenBIOS and
Solaris.

@c man begin OPTIONS

The following options are specific to the Sparc32 emulation:

@table @option

@item -g @var{W}x@var{H}x[x@var{DEPTH}]

Set the initial graphics mode. For TCX, the default is 1024x768x8 with the
option of 1024x768x24. For cgthree, the default is 1024x768x8 with the option
of 1152x900x8 for people who wish to use OBP.

@item -prom-env @var{string}

Set OpenBIOS variables in NVRAM, for example:

@example
qemu-system-sparc -prom-env 'auto-boot?=false' \
 -prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
@end example

@item -M [SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic] [|SPARCbook]

Set the emulated machine type. Default is SS-5.

@end table

@c man end

@node Sparc64 System emulator
@section Sparc64 System emulator
@cindex system emulation (Sparc64)

Use the executable @file{qemu-system-sparc64} to simulate a Sun4u
(UltraSPARC PC-like machine), Sun4v (T1 PC-like machine), or generic
Niagara (T1) machine. The Sun4u emulator is mostly complete, being
able to run Linux, NetBSD and OpenBSD in headless (-nographic) mode. The
Sun4v emulator is still a work in progress.

The Niagara T1 emulator makes use of firmware and OS binaries supplied in the S10image/ directory
of the OpenSPARC T1 project @url{http://download.oracle.com/technetwork/systems/opensparc/OpenSPARCT1_Arch.1.5.tar.bz2}
and is able to boot the disk.s10hw2 Solaris image.
@example
qemu-system-sparc64 -M niagara -L /path-to/S10image/ \
                    -nographic -m 256 \
                    -drive if=pflash,readonly=on,file=/S10image/disk.s10hw2
@end example


QEMU emulates the following peripherals:

@itemize @minus
@item
UltraSparc IIi APB PCI Bridge
@item
PCI VGA compatible card with VESA Bochs Extensions
@item
PS/2 mouse and keyboard
@item
Non Volatile RAM M48T59
@item
PC-compatible serial ports
@item
2 PCI IDE interfaces with hard disk and CD-ROM support
@item
Floppy disk
@end itemize

@c man begin OPTIONS

The following options are specific to the Sparc64 emulation:

@table @option

@item -prom-env @var{string}

Set OpenBIOS variables in NVRAM, for example:

@example
qemu-system-sparc64 -prom-env 'auto-boot?=false'
@end example

@item -M [sun4u|sun4v|niagara]

Set the emulated machine type. The default is sun4u.

@end table

@c man end

@node MIPS System emulator
@section MIPS System emulator
@cindex system emulation (MIPS)

Four executables cover simulation of 32 and 64-bit MIPS systems in
both endian options, @file{qemu-system-mips}, @file{qemu-system-mipsel}
@file{qemu-system-mips64} and @file{qemu-system-mips64el}.
Five different machine types are emulated:

@itemize @minus
@item
A generic ISA PC-like machine "mips"
@item
The MIPS Malta prototype board "malta"
@item
An ACER Pica "pica61". This machine needs the 64-bit emulator.
@item
MIPS emulator pseudo board "mipssim"
@item
A MIPS Magnum R4000 machine "magnum". This machine needs the 64-bit emulator.
@end itemize

The generic emulation is supported by Debian 'Etch' and is able to
install Debian into a virtual disk image. The following devices are
emulated:

@itemize @minus
@item
A range of MIPS CPUs, default is the 24Kf
@item
PC style serial port
@item
PC style IDE disk
@item
NE2000 network card
@end itemize

The Malta emulation supports the following devices:

@itemize @minus
@item
Core board with MIPS 24Kf CPU and Galileo system controller
@item
PIIX4 PCI/USB/SMbus controller
@item
The Multi-I/O chip's serial device
@item
PCI network cards (PCnet32 and others)
@item
Malta FPGA serial device
@item
Cirrus (default) or any other PCI VGA graphics card
@end itemize

The ACER Pica emulation supports:

@itemize @minus
@item
MIPS R4000 CPU
@item
PC-style IRQ and DMA controllers
@item
PC Keyboard
@item
IDE controller
@end itemize

The mipssim pseudo board emulation provides an environment similar
to what the proprietary MIPS emulator uses for running Linux.
It supports:

@itemize @minus
@item
A range of MIPS CPUs, default is the 24Kf
@item
PC style serial port
@item
MIPSnet network emulation
@end itemize

The MIPS Magnum R4000 emulation supports:

@itemize @minus
@item
MIPS R4000 CPU
@item
PC-style IRQ controller
@item
PC Keyboard
@item
SCSI controller
@item
G364 framebuffer
@end itemize


@node ARM System emulator
@section ARM System emulator
@cindex system emulation (ARM)

Use the executable @file{qemu-system-arm} to simulate a ARM
machine. The ARM Integrator/CP board is emulated with the following
devices:

@itemize @minus
@item
ARM926E, ARM1026E, ARM946E, ARM1136 or Cortex-A8 CPU
@item
Two PL011 UARTs
@item
SMC 91c111 Ethernet adapter
@item
PL110 LCD controller
@item
PL050 KMI with PS/2 keyboard and mouse.
@item
PL181 MultiMedia Card Interface with SD card.
@end itemize

The ARM Versatile baseboard is emulated with the following devices:

@itemize @minus
@item
ARM926E, ARM1136 or Cortex-A8 CPU
@item
PL190 Vectored Interrupt Controller
@item
Four PL011 UARTs
@item
SMC 91c111 Ethernet adapter
@item
PL110 LCD controller
@item
PL050 KMI with PS/2 keyboard and mouse.
@item
PCI host bridge.  Note the emulated PCI bridge only provides access to
PCI memory space.  It does not provide access to PCI IO space.
This means some devices (eg. ne2k_pci NIC) are not usable, and others
(eg. rtl8139 NIC) are only usable when the guest drivers use the memory
mapped control registers.
@item
PCI OHCI USB controller.
@item
LSI53C895A PCI SCSI Host Bus Adapter with hard disk and CD-ROM devices.
@item
PL181 MultiMedia Card Interface with SD card.
@end itemize

Several variants of the ARM RealView baseboard are emulated,
including the EB, PB-A8 and PBX-A9.  Due to interactions with the
bootloader, only certain Linux kernel configurations work out
of the box on these boards.

Kernels for the PB-A8 board should have CONFIG_REALVIEW_HIGH_PHYS_OFFSET
enabled in the kernel, and expect 512M RAM.  Kernels for The PBX-A9 board
should have CONFIG_SPARSEMEM enabled, CONFIG_REALVIEW_HIGH_PHYS_OFFSET
disabled and expect 1024M RAM.

The following devices are emulated:

@itemize @minus
@item
ARM926E, ARM1136, ARM11MPCore, Cortex-A8 or Cortex-A9 MPCore CPU
@item
ARM AMBA Generic/Distributed Interrupt Controller
@item
Four PL011 UARTs
@item
SMC 91c111 or SMSC LAN9118 Ethernet adapter
@item
PL110 LCD controller
@item
PL050 KMI with PS/2 keyboard and mouse
@item
PCI host bridge
@item
PCI OHCI USB controller
@item
LSI53C895A PCI SCSI Host Bus Adapter with hard disk and CD-ROM devices
@item
PL181 MultiMedia Card Interface with SD card.
@end itemize

The XScale-based clamshell PDA models ("Spitz", "Akita", "Borzoi"
and "Terrier") emulation includes the following peripherals:

@itemize @minus
@item
Intel PXA270 System-on-chip (ARM V5TE core)
@item
NAND Flash memory
@item
IBM/Hitachi DSCM microdrive in a PXA PCMCIA slot - not in "Akita"
@item
On-chip OHCI USB controller
@item
On-chip LCD controller
@item
On-chip Real Time Clock
@item
TI ADS7846 touchscreen controller on SSP bus
@item
Maxim MAX1111 analog-digital converter on I@math{^2}C bus
@item
GPIO-connected keyboard controller and LEDs
@item
Secure Digital card connected to PXA MMC/SD host
@item
Three on-chip UARTs
@item
WM8750 audio CODEC on I@math{^2}C and I@math{^2}S busses
@end itemize

The Palm Tungsten|E PDA (codename "Cheetah") emulation includes the
following elements:

@itemize @minus
@item
Texas Instruments OMAP310 System-on-chip (ARM 925T core)
@item
ROM and RAM memories (ROM firmware image can be loaded with -option-rom)
@item
On-chip LCD controller
@item
On-chip Real Time Clock
@item
TI TSC2102i touchscreen controller / analog-digital converter / Audio
CODEC, connected through MicroWire and I@math{^2}S busses
@item
GPIO-connected matrix keypad
@item
Secure Digital card connected to OMAP MMC/SD host
@item
Three on-chip UARTs
@end itemize

Nokia N800 and N810 internet tablets (known also as RX-34 and RX-44 / 48)
emulation supports the following elements:

@itemize @minus
@item
Texas Instruments OMAP2420 System-on-chip (ARM 1136 core)
@item
RAM and non-volatile OneNAND Flash memories
@item
Display connected to EPSON remote framebuffer chip and OMAP on-chip
display controller and a LS041y3 MIPI DBI-C controller
@item
TI TSC2301 (in N800) and TI TSC2005 (in N810) touchscreen controllers
driven through SPI bus
@item
National Semiconductor LM8323-controlled qwerty keyboard driven
through I@math{^2}C bus
@item
Secure Digital card connected to OMAP MMC/SD host
@item
Three OMAP on-chip UARTs and on-chip STI debugging console
@item
A Bluetooth(R) transceiver and HCI connected to an UART
@item
Mentor Graphics "Inventra" dual-role USB controller embedded in a TI
TUSB6010 chip - only USB host mode is supported
@item
TI TMP105 temperature sensor driven through I@math{^2}C bus
@item
TI TWL92230C power management companion with an RTC on I@math{^2}C bus
@item
Nokia RETU and TAHVO multi-purpose chips with an RTC, connected
through CBUS
@end itemize

The Luminary Micro Stellaris LM3S811EVB emulation includes the following
devices:

@itemize @minus
@item
Cortex-M3 CPU core.
@item
64k Flash and 8k SRAM.
@item
Timers, UARTs, ADC and I@math{^2}C interface.
@item
OSRAM Pictiva 96x16 OLED with SSD0303 controller on I@math{^2}C bus.
@end itemize

The Luminary Micro Stellaris LM3S6965EVB emulation includes the following
devices:

@itemize @minus
@item
Cortex-M3 CPU core.
@item
256k Flash and 64k SRAM.
@item
Timers, UARTs, ADC, I@math{^2}C and SSI interfaces.
@item
OSRAM Pictiva 128x64 OLED with SSD0323 controller connected via SSI.
@end itemize

The Freecom MusicPal internet radio emulation includes the following
elements:

@itemize @minus
@item
Marvell MV88W8618 ARM core.
@item
32 MB RAM, 256 KB SRAM, 8 MB flash.
@item
Up to 2 16550 UARTs
@item
MV88W8xx8 Ethernet controller
@item
MV88W8618 audio controller, WM8750 CODEC and mixer
@item
128×64 display with brightness control
@item
2 buttons, 2 navigation wheels with button function
@end itemize

The Siemens SX1 models v1 and v2 (default) basic emulation.
The emulation includes the following elements:

@itemize @minus
@item
Texas Instruments OMAP310 System-on-chip (ARM 925T core)
@item
ROM and RAM memories (ROM firmware image can be loaded with -pflash)
V1
1 Flash of 16MB and 1 Flash of 8MB
V2
1 Flash of 32MB
@item
On-chip LCD controller
@item
On-chip Real Time Clock
@item
Secure Digital card connected to OMAP MMC/SD host
@item
Three on-chip UARTs
@end itemize

A Linux 2.6 test image is available on the QEMU web site. More
information is available in the QEMU mailing-list archive.

@c man begin OPTIONS

The following options are specific to the ARM emulation:

@table @option

@item -semihosting
Enable semihosting syscall emulation.

On ARM this implements the "Angel" interface.

Note that this allows guest direct access to the host filesystem,
so should only be used with trusted guest OS.

@end table

@node ColdFire System emulator
@section ColdFire System emulator
@cindex system emulation (ColdFire)
@cindex system emulation (M68K)

Use the executable @file{qemu-system-m68k} to simulate a ColdFire machine.
The emulator is able to boot a uClinux kernel.

The M5208EVB emulation includes the following devices:

@itemize @minus
@item
MCF5208 ColdFire V2 Microprocessor (ISA A+ with EMAC).
@item
Three Two on-chip UARTs.
@item
Fast Ethernet Controller (FEC)
@end itemize

The AN5206 emulation includes the following devices:

@itemize @minus
@item
MCF5206 ColdFire V2 Microprocessor.
@item
Two on-chip UARTs.
@end itemize

@c man begin OPTIONS

The following options are specific to the ColdFire emulation:

@table @option

@item -semihosting
Enable semihosting syscall emulation.

On M68K this implements the "ColdFire GDB" interface used by libgloss.

Note that this allows guest direct access to the host filesystem,
so should only be used with trusted guest OS.

@end table

@node Cris System emulator
@section Cris System emulator
@cindex system emulation (Cris)

TODO

@node Microblaze System emulator
@section Microblaze System emulator
@cindex system emulation (Microblaze)

TODO

@node SH4 System emulator
@section SH4 System emulator
@cindex system emulation (SH4)

TODO

@node Xtensa System emulator
@section Xtensa System emulator
@cindex system emulation (Xtensa)

Two executables cover simulation of both Xtensa endian options,
@file{qemu-system-xtensa} and @file{qemu-system-xtensaeb}.
Two different machine types are emulated:

@itemize @minus
@item
Xtensa emulator pseudo board "sim"
@item
Avnet LX60/LX110/LX200 board
@end itemize

The sim pseudo board emulation provides an environment similar
to one provided by the proprietary Tensilica ISS.
It supports:

@itemize @minus
@item
A range of Xtensa CPUs, default is the DC232B
@item
Console and filesystem access via semihosting calls
@end itemize

The Avnet LX60/LX110/LX200 emulation supports:

@itemize @minus
@item
A range of Xtensa CPUs, default is the DC232B
@item
16550 UART
@item
OpenCores 10/100 Mbps Ethernet MAC
@end itemize

@c man begin OPTIONS

The following options are specific to the Xtensa emulation:

@table @option

@item -semihosting
Enable semihosting syscall emulation.

Xtensa semihosting provides basic file IO calls, such as open/read/write/seek/select.
Tensilica baremetal libc for ISS and linux platform "sim" use this interface.

Note that this allows guest direct access to the host filesystem,
so should only be used with trusted guest OS.

@end table
@node QEMU User space emulator
@chapter QEMU User space emulator

@menu
* Supported Operating Systems ::
* Features::
* Linux User space emulator::
* BSD User space emulator ::
@end menu

@node Supported Operating Systems
@section Supported Operating Systems

The following OS are supported in user space emulation:

@itemize @minus
@item
Linux (referred as qemu-linux-user)
@item
BSD (referred as qemu-bsd-user)
@end itemize

@node Features
@section Features

QEMU user space emulation has the following notable features:

@table @strong
@item System call translation:
QEMU includes a generic system call translator.  This means that
the parameters of the system calls can be converted to fix
endianness and 32/64-bit mismatches between hosts and targets.
IOCTLs can be converted too.

@item POSIX signal handling:
QEMU can redirect to the running program all signals coming from
the host (such as @code{SIGALRM}), as well as synthesize signals from
virtual CPU exceptions (for example @code{SIGFPE} when the program
executes a division by zero).

QEMU relies on the host kernel to emulate most signal system
calls, for example to emulate the signal mask.  On Linux, QEMU
supports both normal and real-time signals.

@item Threading:
On Linux, QEMU can emulate the @code{clone} syscall and create a real
host thread (with a separate virtual CPU) for each emulated thread.
Note that not all targets currently emulate atomic operations correctly.
x86 and ARM use a global lock in order to preserve their semantics.
@end table

QEMU was conceived so that ultimately it can emulate itself. Although
it is not very useful, it is an important test to show the power of the
emulator.

@node Linux User space emulator
@section Linux User space emulator

@menu
* Quick Start::
* Wine launch::
* Command line options::
* Other binaries::
@end menu

@node Quick Start
@subsection Quick Start

In order to launch a Linux process, QEMU needs the process executable
itself and all the target (x86) dynamic libraries used by it.

@itemize

@item On x86, you can just try to launch any process by using the native
libraries:

@example
qemu-i386 -L / /bin/ls
@end example

@code{-L /} tells that the x86 dynamic linker must be searched with a
@file{/} prefix.

@item Since QEMU is also a linux process, you can launch QEMU with
QEMU (NOTE: you can only do that if you compiled QEMU from the sources):

@example
qemu-i386 -L / qemu-i386 -L / /bin/ls
@end example

@item On non x86 CPUs, you need first to download at least an x86 glibc
(@file{qemu-runtime-i386-XXX-.tar.gz} on the QEMU web page). Ensure that
@code{LD_LIBRARY_PATH} is not set:

@example
unset LD_LIBRARY_PATH
@end example

Then you can launch the precompiled @file{ls} x86 executable:

@example
qemu-i386 tests/i386/ls
@end example
You can look at @file{scripts/qemu-binfmt-conf.sh} so that
QEMU is automatically launched by the Linux kernel when you try to
launch x86 executables. It requires the @code{binfmt_misc} module in the
Linux kernel.

@item The x86 version of QEMU is also included. You can try weird things such as:
@example
qemu-i386 /usr/local/qemu-i386/bin/qemu-i386 \
          /usr/local/qemu-i386/bin/ls-i386
@end example

@end itemize

@node Wine launch
@subsection Wine launch

@itemize

@item Ensure that you have a working QEMU with the x86 glibc
distribution (see previous section). In order to verify it, you must be
able to do:

@example
qemu-i386 /usr/local/qemu-i386/bin/ls-i386
@end example

@item Download the binary x86 Wine install
(@file{qemu-XXX-i386-wine.tar.gz} on the QEMU web page).

@item Configure Wine on your account. Look at the provided script
@file{/usr/local/qemu-i386/@/bin/wine-conf.sh}. Your previous
@code{$@{HOME@}/.wine} directory is saved to @code{$@{HOME@}/.wine.org}.

@item Then you can try the example @file{putty.exe}:

@example
qemu-i386 /usr/local/qemu-i386/wine/bin/wine \
          /usr/local/qemu-i386/wine/c/Program\ Files/putty.exe
@end example

@end itemize

@node Command line options
@subsection Command line options

@example
@command{qemu-i386} [@option{-h]} [@option{-d]} [@option{-L} @var{path}] [@option{-s} @var{size}] [@option{-cpu} @var{model}] [@option{-g} @var{port}] [@option{-B} @var{offset}] [@option{-R} @var{size}] @var{program} [@var{arguments}...]
@end example

@table @option
@item -h
Print the help
@item -L path
Set the x86 elf interpreter prefix (default=/usr/local/qemu-i386)
@item -s size
Set the x86 stack size in bytes (default=524288)
@item -cpu model
Select CPU model (-cpu help for list and additional feature selection)
@item -E @var{var}=@var{value}
Set environment @var{var} to @var{value}.
@item -U @var{var}
Remove @var{var} from the environment.
@item -B offset
Offset guest address by the specified number of bytes.  This is useful when
the address region required by guest applications is reserved on the host.
This option is currently only supported on some hosts.
@item -R size
Pre-allocate a guest virtual address space of the given size (in bytes).
"G", "M", and "k" suffixes may be used when specifying the size.
@end table

Debug options:

@table @option
@item -d item1,...
Activate logging of the specified items (use '-d help' for a list of log items)
@item -p pagesize
Act as if the host page size was 'pagesize' bytes
@item -g port
Wait gdb connection to port
@item -singlestep
Run the emulation in single step mode.
@end table

Environment variables:

@table @env
@item QEMU_STRACE
Print system calls and arguments similar to the 'strace' program
(NOTE: the actual 'strace' program will not work because the user
space emulator hasn't implemented ptrace).  At the moment this is
incomplete.  All system calls that don't have a specific argument
format are printed with information for six arguments.  Many
flag-style arguments don't have decoders and will show up as numbers.
@end table

@node Other binaries
@subsection Other binaries

@cindex user mode (Alpha)
@command{qemu-alpha} TODO.

@cindex user mode (ARM)
@command{qemu-armeb} TODO.

@cindex user mode (ARM)
@command{qemu-arm} is also capable of running ARM "Angel" semihosted ELF
binaries (as implemented by the arm-elf and arm-eabi Newlib/GDB
configurations), and arm-uclinux bFLT format binaries.

@cindex user mode (ColdFire)
@cindex user mode (M68K)
@command{qemu-m68k} is capable of running semihosted binaries using the BDM
(m5xxx-ram-hosted.ld) or m68k-sim (sim.ld) syscall interfaces, and
coldfire uClinux bFLT format binaries.

The binary format is detected automatically.

@cindex user mode (Cris)
@command{qemu-cris} TODO.

@cindex user mode (i386)
@command{qemu-i386} TODO.
@command{qemu-x86_64} TODO.

@cindex user mode (Microblaze)
@command{qemu-microblaze} TODO.

@cindex user mode (MIPS)
@command{qemu-mips} TODO.
@command{qemu-mipsel} TODO.

@cindex user mode (NiosII)
@command{qemu-nios2} TODO.

@cindex user mode (PowerPC)
@command{qemu-ppc64abi32} TODO.
@command{qemu-ppc64} TODO.
@command{qemu-ppc} TODO.

@cindex user mode (SH4)
@command{qemu-sh4eb} TODO.
@command{qemu-sh4} TODO.

@cindex user mode (SPARC)
@command{qemu-sparc} can execute Sparc32 binaries (Sparc32 CPU, 32 bit ABI).

@command{qemu-sparc32plus} can execute Sparc32 and SPARC32PLUS binaries
(Sparc64 CPU, 32 bit ABI).

@command{qemu-sparc64} can execute some Sparc64 (Sparc64 CPU, 64 bit ABI) and
SPARC32PLUS binaries (Sparc64 CPU, 32 bit ABI).

@node BSD User space emulator
@section BSD User space emulator

@menu
* BSD Status::
* BSD Quick Start::
* BSD Command line options::
@end menu

@node BSD Status
@subsection BSD Status

@itemize @minus
@item
target Sparc64 on Sparc64: Some trivial programs work.
@end itemize

@node BSD Quick Start
@subsection Quick Start

In order to launch a BSD process, QEMU needs the process executable
itself and all the target dynamic libraries used by it.

@itemize

@item On Sparc64, you can just try to launch any process by using the native
libraries:

@example
qemu-sparc64 /bin/ls
@end example

@end itemize

@node BSD Command line options
@subsection Command line options

@example
@command{qemu-sparc64} [@option{-h]} [@option{-d]} [@option{-L} @var{path}] [@option{-s} @var{size}] [@option{-bsd} @var{type}] @var{program} [@var{arguments}...]
@end example

@table @option
@item -h
Print the help
@item -L path
Set the library root path (default=/)
@item -s size
Set the stack size in bytes (default=524288)
@item -ignore-environment
Start with an empty environment. Without this option,
the initial environment is a copy of the caller's environment.
@item -E @var{var}=@var{value}
Set environment @var{var} to @var{value}.
@item -U @var{var}
Remove @var{var} from the environment.
@item -bsd type
Set the type of the emulated BSD Operating system. Valid values are
FreeBSD, NetBSD and OpenBSD (default).
@end table

Debug options:

@table @option
@item -d item1,...
Activate logging of the specified items (use '-d help' for a list of log items)
@item -p pagesize
Act as if the host page size was 'pagesize' bytes
@item -singlestep
Run the emulation in single step mode.
@end table


@include qemu-tech.texi

@node License
@appendix License

QEMU is a trademark of Fabrice Bellard.

QEMU is released under the GNU General Public License (TODO: add link).
Parts of QEMU have specific licenses, see file LICENSE.

TODO (refer to file LICENSE, include it, include the GPL?)

@node Index
@appendix Index
@menu
* Concept Index::
* Function Index::
* Keystroke Index::
* Program Index::
* Data Type Index::
* Variable Index::
@end menu

@node Concept Index
@section Concept Index
This is the main index. Should we combine all keywords in one index? TODO
@printindex cp

@node Function Index
@section Function Index
This index could be used for command line options and monitor functions.
@printindex fn

@node Keystroke Index
@section Keystroke Index

This is a list of all keystrokes which have a special function
in system emulation.

@printindex ky

@node Program Index
@section Program Index
@printindex pg

@node Data Type Index
@section Data Type Index

This index could be used for qdev device names and options.

@printindex tp

@node Variable Index
@section Variable Index
@printindex vr

@bye