docs/formatcaps.html.in

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   5     <h1>Driver capabilities XML format</h1>
   6
   7     <ul id="toc"></ul>
   8
   9     <h2><a id="elements">Element and attribute overview</a></h2>
  10
  11     <p>As new virtualization engine support gets added to libvirt, and to
  12     handle cases like QEMU supporting a variety of emulations, a query
  13     interface has been added in 0.2.1 allowing to list the set of supported
  14     virtualization capabilities on the host:</p>
  15
  16     <pre>char * virConnectGetCapabilities (virConnectPtr conn);</pre>
  17
  18     <p>The value returned is an XML document listing the virtualization
  19     capabilities of the host and virtualization engine to which
  20     <code>@conn</code> is connected. One can test it using <code>virsh</code>
  21     command line tool command '<code>capabilities</code>', it dumps the XML
  22     associated to the current connection. </p>
  23
  24     <p>As can be seen in the <a href="#elementExamples">example</a>, the
  25     capabilities XML consists of the <code>capabilities</code> element which
  26     have exactly one <code>host</code> child element to report information on
  27     host capabilities, and zero or more <code>guest</code> element to express
  28     the set of architectures the host can run at the moment.</p>
  29
  30
  31     <h3><a id="elementHost">Host capabilities</a></h3>
  32
  33     <p>The <code>&lt;host/&gt;</code> element consists of the following child
  34     elements:</p>
  35     <dl>
  36       <dt><code>uuid</code></dt>
  37       <dd>The host UUID.</dd>
  38
  39       <dt><code>cpu</code></dt>
  40       <dd>The host CPU architecture and features.</dd>
  41
  42       <dt><code>power_management</code></dt>
  43       <dd>whether host is capable of memory suspend, disk hibernation, or
  44       hybrid suspend.</dd>
  45
  46       <dt><code>migration</code></dt>
  47       <dd>This element exposes information on the hypervisor's migration
  48       capabilities, like live migration, supported URI transports, and so
  49       on.</dd>
  50
  51       <dt><code>topology</code></dt>
  52       <dd>This element embodies the host internal topology. Management
  53       applications may want to learn this information when orchestrating new
  54       guests - e.g. due to reduce inter-NUMA node transfers.</dd>
  55
  56       <dt><code>secmodel</code></dt>
  57       <dd>To find out default security labels for different security models you
  58       need to parse this element. In contrast with the former elements, this is
  59       repeated for each security model the libvirt daemon currently supports.
  60       </dd>
  61     </dl>
  62
  63
  64     <h3><a id="elementGuest">Guest capabilities</a></h3>
  65
  66     <p>While the <a href="#elementHost">previous section</a> aims at host
  67     capabilities, this one focuses on capabilities available to a guest
  68     using a given hypervisor. The <code>&lt;guest/&gt;</code> element will
  69     typically wrap up the following elements:</p>
  70
  71     <dl>
  72         <dt><code>os_type</code></dt>
  73         <dd>This expresses what kind of operating system the hypervisor
  74         is able to run. Possible values are:
  75         <dl>
  76           <dt><code>xen</code></dt>
  77           <dd>for XEN PV</dd>
  78
  79           <dt><code>linux</code></dt>
  80           <dd>legacy alias for <code>xen</code></dd>
  81
  82           <dt><code>xenpvh</code></dt>
  83           <dd>for XEN PVH</dd>
  84
  85           <dt><code>hvm</code></dt>
  86           <dd>Unmodified operating system</dd>
  87
  88           <dt><code>exe</code></dt>
  89           <dd>Container based virtualization</dd>
  90         </dl>
  91         </dd>
  92
  93         <dt><code>arch</code></dt>
  94         <dd>This element brings some information on supported guest
  95           architecture. Possible subelements are:
  96           <dl>
  97             <dt><code>wordsize</code></dt><dd>Size of CPU word in bits, for example 64.</dd>
  98             <dt><code>emulator</code></dt><dd>Emulator (device model) path, for
  99               use in <a href="formatdomain.html#elementEmulator">emulator</a>
 100               element of domain XML.</dd>
 101             <dt><code>loader</code></dt><dd>Loader path, for use in
 102               <a href="formatdomain.html#elementLoader">loader</a> element of domain
 103               XML.</dd>
 104             <dt><code>machine</code></dt><dd>Machine type, for use in
 105               <a href="formatdomain.html#attributeOSTypeMachine">machine</a>
 106               attribute of os/type element in domain XML. For example Xen
 107               supports <code>xenfv</code> for HVM, <code>xenpv</code> for
 108               PV, or <code>xenpvh</code> for PVH.</dd>
 109             <dt><code>domain</code></dt><dd>The <code>type</code> attribute of
 110               this element specifies the type of hypervisor required to run the
 111               domain. Use in <a href="formatdomain.html#attributeDomainType">type</a>
 112               attribute of the domain root element.</dd>
 113           </dl>
 114         </dd>
 115
 116         <dt><code>features</code></dt>
 117         <dd>This optional element encases possible features that can be used
 118           with a guest of described type.  Possible subelements are:
 119           <dl>
 120             <dt><code>pae</code></dt><dd>If present, 32-bit guests can use PAE
 121               address space extensions, <span class="since">since
 122               0.4.1</span></dd>
 123             <dt><code>nonpae</code></dt><dd>If present, 32-bit guests can be run
 124               without requiring PAE, <span class="since">since
 125               0.4.1</span></dd>
 126             <dt><code>ia64_be</code></dt><dd>If present, IA64 guests can be run in
 127               big-endian mode, <span class="since">since 0.4.1</span></dd>
 128             <dt><code>acpi</code></dt><dd>If this element is present,
 129               the <code>default</code> attribute describes whether the
 130               hypervisor exposes ACPI to the guest by default, and
 131               the <code>toggle</code> attribute describes whether the
 132               user can override this
 133               default. <span class="since">Since 0.4.1</span></dd>
 134             <dt><code>apic</code></dt><dd>If this element is present,
 135               the <code>default</code> attribute describes whether the
 136               hypervisor exposes APIC to the guest by default, and
 137               the <code>toggle</code> attribute describes whether the
 138               user can override this
 139               default. <span class="since">Since 0.4.1</span></dd>
 140             <dt><code>cpuselection</code></dt><dd>If this element is present, the
 141               hypervisor supports the <code>&lt;cpu&gt;</code> element
 142               within a domain definition for fine-grained control over
 143               the CPU presented to the
 144               guest. <span class="since">Since 0.7.5</span></dd>
 145             <dt><code>deviceboot</code></dt><dd>If this element is present,
 146               the <code>&lt;boot order='...'/&gt;</code> element can
 147               be used inside devices, rather than the older boot
 148               specification by category. <span class="since">Since
 149               0.8.8</span></dd>
 150             <dt><code>disksnapshot</code></dt><dd>If this element is present,
 151               the <code>default</code> attribute describes whether
 152               external disk snapshots are supported.  If absent,
 153               external snapshots may still be supported, but it
 154               requires attempting the API and checking for an error to
 155               find out for sure. <span class="since">Since
 156               1.2.3</span></dd>
 157           </dl>
 158         </dd>
 159     </dl>
 160
 161     <h3><a id="elementExamples">Examples</a></h3>
 162
 163     <p>For example, in the case of a 64-bit machine with hardware
 164     virtualization capabilities enabled in the chip and
 165     BIOS you will see:</p>
 166
 167     <pre>&lt;capabilities&gt;
 168   <span style="color: #E50000">&lt;host&gt;
 169     &lt;cpu&gt;
 170       &lt;arch&gt;x86_64&lt;/arch&gt;
 171       &lt;features&gt;
 172         &lt;vmx/&gt;
 173       &lt;/features&gt;
 174       &lt;model&gt;core2duo&lt;/model&gt;
 175       &lt;vendor&gt;Intel&lt;/vendor&gt;
 176       &lt;topology sockets="1" cores="2" threads="1"/&gt;
 177       &lt;feature name="lahf_lm"/&gt;
 178       &lt;feature name='xtpr'/&gt;
 179       ...
 180     &lt;/cpu&gt;
 181     &lt;power_management&gt;
 182       &lt;suspend_mem/&gt;
 183       &lt;suspend_disk/&gt;
 184       &lt;suspend_hybrid/&gt;
 185     &lt;/power_management&gt;
 186   &lt;/host&gt;</span>
 187
 188   &lt;!-- xen-3.0-x86_64 --&gt;
 189   <span style="color: #0000E5">&lt;guest&gt;
 190     &lt;os_type&gt;xen&lt;/os_type&gt;
 191     &lt;arch name="x86_64"&gt;
 192       &lt;wordsize&gt;64&lt;/wordsize&gt;
 193       &lt;domain type="xen"&gt;&lt;/domain&gt;
 194       &lt;emulator&gt;/usr/lib64/xen/bin/qemu-dm&lt;/emulator&gt;
 195     &lt;/arch&gt;
 196     &lt;features&gt;
 197     &lt;/features&gt;
 198   &lt;/guest&gt;</span>
 199
 200   &lt;!-- hvm-3.0-x86_32 --&gt;
 201   <span style="color: #00B200">&lt;guest&gt;
 202     &lt;os_type&gt;hvm&lt;/os_type&gt;
 203     &lt;arch name="i686"&gt;
 204       &lt;wordsize&gt;32&lt;/wordsize&gt;
 205       &lt;domain type="xen"&gt;&lt;/domain&gt;
 206       &lt;emulator&gt;/usr/lib/xen/bin/qemu-dm&lt;/emulator&gt;
 207       &lt;machine&gt;pc&lt;/machine&gt;
 208       &lt;machine&gt;isapc&lt;/machine&gt;
 209       &lt;loader&gt;/usr/lib/xen/boot/hvmloader&lt;/loader&gt;
 210     &lt;/arch&gt;
 211     &lt;features&gt;
 212       &lt;cpuselection/&gt;
 213       &lt;deviceboot/&gt;
 214     &lt;/features&gt;
 215   &lt;/guest&gt;</span>
 216   ...
 217 &lt;/capabilities&gt;</pre>
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