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14319c81a0
The domain capabilities XML is capable of showing whether each guest CPU
mode is supported or not with a possibility to provide additional
details. This patch enhances host-model capability to advertise the
exact CPU model which will be used as a host-model:
<cpu>
...
<mode name='host-model' supported='yes'>
<model fallback='allow'>Broadwell</model>
<vendor>Intel</vendor>
<feature policy='disable' name='aes'/>
<feature policy='require' name='vmx'/>
</mode>
...
</cpu>
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
445 lines
14 KiB
XML
445 lines
14 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<body>
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<h1>Domain capabilities XML format</h1>
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<ul id="toc"></ul>
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<h2><a name="Overview">Overview</a></h2>
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<p>Sometimes, when a new domain is to be created it may come handy to know
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the capabilities of the hypervisor so the correct combination of devices and
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drivers is used. For example, when management application is considering the
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mode for a host device's passthrough there are several options depending not
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only on host, but on hypervisor in question too. If the hypervisor is qemu
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then it needs to be more recent to support VFIO, while legacy KVM is
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achievable just fine with older qemus.</p>
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<p>The main difference between
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<a href="/html/libvirt-libvirt-host.html#virConnectGetCapabilities">
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<code>virConnectGetCapabilities</code>
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</a>
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and the emulator capabilities API is, the former one aims more on
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the host capabilities (e.g. NUMA topology, security models in
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effect, etc.) while the latter one specializes on the hypervisor
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capabilities.</p>
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<p>While the <a href="formatcaps.html">Driver Capabilities</a> provides the
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host capabilities (e.g NUMA topology, security models in effect, etc.), the
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Domain Capabilities provides the hypervisor specific capabilities for
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Management Applications to query and make decisions regarding what to
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utilize.</p>
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<p>The Domain Capabilities can provide information such as the correct
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combination of devices and drivers that are supported. Knowing which host
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and hypervisor specific options are available or supported would allow the
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management application to choose an appropriate mode for a pass-through
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host device as well as which adapter to utilize.</p>
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<h2><a name="elements">Element and attribute overview</a></h2>
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<p> A new query interface was added to the virConnect API's to retrieve the
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XML listing of the set of domain capabilities (<span class="since">Since
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1.2.7</span>):</p>
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<pre>
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<a href="/html/libvirt-libvirt-domain.html#virConnectGetDomainCapabilities">virConnectGetDomainCapabilities</a>
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</pre>
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<p>The root element that emulator capability XML document starts with has
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name <code>domainCapabilities</code>. It contains at least four direct
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child elements:</p>
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<pre>
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<domainCapabilities>
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<path>/usr/bin/qemu-system-x86_64</path>
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<domain>kvm</domain>
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<machine>pc-i440fx-2.1</machine>
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<arch>x86_64</arch>
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...
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</domainCapabilities>
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</pre>
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<dl>
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<dt><code>path</code></dt>
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<dd>The full path to the emulator binary.</dd>
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<dt><code>domain</code></dt>
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<dd>Describes the <a href="formatdomain.html#elements">virtualization
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type</a> (or so called domain type).</dd>
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<dt><code>machine</code></dt>
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<dd>The domain's <a href="formatdomain.html#elementsOSBIOS">machine
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type</a>.</dd>
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<dt><code>arch</code></dt>
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<dd>The domain's <a href="formatdomain.html#elementsOSBIOS">
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architecture</a>.</dd>
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</dl>
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<h3><a name="elementsCPUAllocation">CPU Allocation</a></h3>
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<p>Before any devices capability occurs, there might be a info on domain
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wide capabilities, e.g. virtual CPUs:</p>
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<pre>
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<domainCapabilities>
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...
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<vcpu max='255'/>
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...
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</domainCapabilities>
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</pre>
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<dl>
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<dt><code>vcpu</code></dt>
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<dd>The maximum number of supported virtual CPUs</dd>
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</dl>
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<h3><a name="elementsOSBIOS">BIOS bootloader</a></h3>
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<p>Sometimes users might want to tweak some BIOS knobs or use
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UEFI. For cases like that, <a
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href="formatdomain.html#elementsOSBIOS"><code>os</code></a>
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element exposes what values can be passed to its children.</p>
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<pre>
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<domainCapabilities>
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...
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<os supported='yes'>
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<loader supported='yes'>
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<value>/usr/share/OVMF/OVMF_CODE.fd</value>
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<enum name='type'>
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<value>rom</value>
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<value>pflash</value>
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</enum>
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<enum name='readonly'>
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<value>yes</value>
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<value>no</value>
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</enum>
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</loader>
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</os>
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...
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<domainCapabilities>
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</pre>
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<p>For the <code>loader</code> element, the following can occur:</p>
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<dl>
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<dt><code>value</code></dt>
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<dd>List of known loader paths. Currently this is only used
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to advertise known locations of OVMF binaries for qemu. Binaries
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will only be listed if they actually exist on disk.</dd>
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<dt><code>type</code></dt>
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<dd>Whether loader is a typical BIOS (<code>rom</code>) or
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an UEFI binary (<code>pflash</code>). This refers to
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<code>type</code> attribute of the <loader/>
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element.</dd>
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<dt><code>readonly</code></dt>
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<dd>Options for the <code>readonly</code> attribute of the
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<loader/> element.</dd>
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</dl>
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<h3><a name="elementsCPU">CPU configuration</a></h3>
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<p>
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The <code>cpu</code> element exposes options usable for configuring
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<a href="formatdomain.html#elementsCPU">guest CPUs</a>.
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</p>
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<pre>
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<domainCapabilities>
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...
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<cpu>
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<mode name='host-passthrough' supported='yes'/>
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<mode name='host-model' supported='yes'>
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<model fallback='allow'>Broadwell</model>
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<vendor>Intel</vendor>
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<feature policy='disable' name='aes'/>
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<feature policy='require' name='vmx'/>
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</mode>
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<mode name='custom' supported='yes'>
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<model usable='no'>Broadwell</model>
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<model usable='yes'>Broadwell-noTSX</model>
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<model usable='no'>Haswell</model>
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...
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</mode>
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</cpu>
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...
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<domainCapabilities>
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</pre>
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<p>
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Each CPU mode understood by libvirt is described with a
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<code>mode</code> element which tells whether the particular mode
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is supported and provides (when applicable) more details about it:
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</p>
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<dl>
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<dt><code>host-passthrough</code></dt>
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<dd>No mode specific details are provided.</dd>
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<dt><code>host-model</code></dt>
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<dd>
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If <code>host-model</code> is supported by the hypervisor, the
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<code>mode</code> describes the guest CPU which will be used when
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starting a domain with <code>host-model</code> CPU. The hypervisor
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specifics (such as unsupported CPU models or features, machine type,
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etc.) may be accounted for in this guest CPU specification and thus
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the CPU can be different from the one shown in host capabilities XML.
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This is indicated by the <code>fallback</code> attribute of the
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<code>model</code> sub element: <code>allow</code> means not all
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specifics were accounted for and thus the CPU a guest will see may
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be different; <code>forbid</code> indicates that the CPU a guest will
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see should match this CPU definition.
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</dd>
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<dt><code>custom</code></dt>
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<dd>
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The <code>mode</code> element contains a list of supported CPU
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models, each described by a dedicated <code>model</code> element.
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The <code>usable</code> attribute specifies whether the model can
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be used on the host. A special value <code>unknown</code> indicates
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libvirt does not have enough information to provide the usability
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data.
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</dd>
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</dl>
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<h3><a name="elementsDevices">Devices</a></h3>
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<p>
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Another set of XML elements describe the supported devices and their
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capabilities. All devices occur as children of the main
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<code>devices</code> element.
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</p>
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<pre>
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<domainCapabilities>
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...
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<devices>
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<disk supported='yes'>
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<enum name='diskDevice'>
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<value>disk</value>
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<value>cdrom</value>
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<value>floppy</value>
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<value>lun</value>
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</enum>
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...
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</disk>
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<hostdev supported='no'/>
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</devices>
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</domainCapabilities>
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</pre>
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<p>Reported capabilities are expressed as an enumerated list of available
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options for each of the element or attribute. For example, the
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<disk/> element has an attribute <code>device</code> which can
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support the values <code>disk</code>, <code>cdrom</code>,
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<code>floppy</code>, or <code>lun</code>.</p>
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<h4><a name="elementsDisks">Hard drives, floppy disks, CDROMs</a></h4>
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<p>Disk capabilities are exposed under the <code>disk</code> element. For
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instance:</p>
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<pre>
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<domainCapabilities>
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...
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<devices>
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<disk supported='yes'>
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<enum name='diskDevice'>
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<value>disk</value>
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<value>cdrom</value>
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<value>floppy</value>
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<value>lun</value>
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</enum>
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<enum name='bus'>
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<value>ide</value>
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<value>fdc</value>
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<value>scsi</value>
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<value>virtio</value>
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<value>xen</value>
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<value>usb</value>
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<value>uml</value>
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<value>sata</value>
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<value>sd</value>
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</enum>
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</disk>
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...
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</devices>
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</domainCapabilities>
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</pre>
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<dl>
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<dt><code>diskDevice</code></dt>
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<dd>Options for the <code>device</code> attribute of the <disk/>
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element.</dd>
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<dt><code>bus</code></dt>
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<dd>Options for the <code>bus</code> attribute of the <target/>
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element for a <disk/>.</dd>
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</dl>
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<h4><a name="elementsGraphics">Graphical framebuffers</a></h4>
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<p>Graphics device capabilities are exposed under the
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<code>graphics</code> element. For instance:</p>
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<pre>
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<domainCapabilities>
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...
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<devices>
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<graphics supported='yes'>
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<enum name='type'>
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<value>sdl</value>
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<value>vnc</value>
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<value>spice</value>
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</enum>
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</graphics>
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...
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</devices>
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</domainCapabilities>
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</pre>
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<dl>
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<dt><code>type</code></dt>
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<dd>Options for the <code>type</code> attribute of the <graphics/>
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element.</dd>
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</dl>
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<h4><a name="elementsVideo">Video device</a></h4>
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<p>Video device capabilities are exposed under the
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<code>video</code> element. For instance:</p>
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<pre>
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<domainCapabilities>
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...
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<devices>
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<video supported='yes'>
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<enum name='modelType'>
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<value>vga</value>
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<value>cirrus</value>
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<value>vmvga</value>
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<value>qxl</value>
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<value>virtio</value>
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</enum>
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</video>
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...
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</devices>
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</domainCapabilities>
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</pre>
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<dl>
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<dt><code>modelType</code></dt>
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<dd>Options for the <code>type</code> attribute of the
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<video><model> element.</dd>
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</dl>
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<h4><a name="elementsHostDev">Host device assignment</a></h4>
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<p>Some host devices can be passed through to a guest (e.g. USB, PCI and
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SCSI). Well, only if the following is enabled:</p>
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<pre>
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<domainCapabilities>
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...
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<devices>
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<hostdev supported='yes'>
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<enum name='mode'>
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<value>subsystem</value>
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<value>capabilities</value>
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</enum>
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<enum name='startupPolicy'>
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<value>default</value>
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<value>mandatory</value>
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<value>requisite</value>
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<value>optional</value>
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</enum>
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<enum name='subsysType'>
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<value>usb</value>
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<value>pci</value>
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<value>scsi</value>
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</enum>
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<enum name='capsType'>
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<value>storage</value>
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<value>misc</value>
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<value>net</value>
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</enum>
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<enum name='pciBackend'>
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<value>default</value>
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<value>kvm</value>
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<value>vfio</value>
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<value>xen</value>
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</enum>
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</hostdev>
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</devices>
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</domainCapabilities>
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</pre>
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<dl>
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<dt><code>mode</code></dt>
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<dd>Options for the <code>mode</code> attribute of the <hostdev/>
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element.</dd>
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<dt><code>startupPolicy</code></dt>
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<dd>Options for the <code>startupPolicy</code> attribute of the
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<hostdev/> element.</dd>
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<dt><code>subsysType</code></dt>
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<dd>Options for the <code>type</code> attribute of the <hostdev/>
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element in case of <code>mode="subsystem"</code>.</dd>
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<dt><code>capsType</code></dt>
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<dd>Options for the <code>type</code> attribute of the <hostdev/>
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element in case of <code>mode="capabilities"</code>.</dd>
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<dt><code>pciBackend</code></dt>
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<dd>Options for the <code>name</code> attribute of the <driver/>
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element.</dd>
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</dl>
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<h3><a name="elementsFeatures">Features</a></h3>
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<p>One more set of XML elements describe the supported features and
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their capabilities. All features occur as children of the main
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<code>features</code> element.</p>
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<pre>
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<domainCapabilities>
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...
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<features>
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<gic supported='yes'>
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<enum name='version'>
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<value>2</value>
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<value>3</value>
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</enum>
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</gic>
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</features>
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</domainCapabilities>
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</pre>
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<p>Reported capabilities are expressed as an enumerated list of
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possible values for each of the elements or attributes. For example, the
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<code>gic</code> element has an attribute <code>version</code> which can
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support the values <code>2</code> or <code>3</code>.</p>
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<p>For information about the purpose of each feature, see the
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<a href="formatdomain.html#elementsFeatures">relevant section</a> in
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the domain XML documentation.
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</p>
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<h4><a name="elementsGIC">GIC capabilities</a></h4>
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<p>GIC capabilities are exposed under the <code>gic</code> element.</p>
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<dl>
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<dt><code>version</code></dt>
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<dd>Options for the <code>version</code> attribute of the
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<code>gic</code> element.</dd>
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</dl>
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</body>
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</html>
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