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Our documentation for features was rather sparse; this fleshes out more of the details for other existing capabilities (and cost me some time trawling git history). * docs/formatcaps.html.in: Document it feature bits. Signed-off-by: Eric Blake <eblake@redhat.com>
200 lines
7.7 KiB
XML
200 lines
7.7 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>Driver capabilities XML format</h1>
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<ul id="toc"></ul>
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<h2><a name="elements">Element and attribute overview</a></h2>
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<p>As new virtualization engine support gets added to libvirt, and to
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handle cases like QEMU supporting a variety of emulations, a query
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interface has been added in 0.2.1 allowing to list the set of supported
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virtualization capabilities on the host:</p>
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<pre> char * virConnectGetCapabilities (virConnectPtr conn);</pre>
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<p>The value returned is an XML document listing the virtualization
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capabilities of the host and virtualization engine to which
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<code>@conn</code> is connected. One can test it using <code>virsh</code>
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command line tool command '<code>capabilities</code>', it dumps the XML
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associated to the current connection. </p>
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<p>As can be seen seen in the <a href="#elementExamples">example</a>, the
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capabilities XML consists of the <code>capabilities</code> element which
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have exactly one <code>host</code> child element to report information on
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host capabilities, and zero or more <code>guest</code> element to express
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the set of architectures the host can run at the moment.</p>
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<h3><a name="elementHost">Host capabilities</a></h3>
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<p>The <code><host/></code> element consists of the following child
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elements:</p>
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<dl>
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<dt><code>uuid</code></dt>
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<dd>The host UUID.</dd>
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<dt><code>cpu</code></dt>
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<dd>The host CPU architecture and features.</dd>
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<dt><code>power_management</code></dt>
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<dd>whether host is capable of memory suspend, disk hibernation, or
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hybrid suspend.</dd>
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<dt><code>migration</code></dt>
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<dd>This element exposes information on the hypervisor's migration
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capabilities, like live migration, supported URI transports, and so
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on.</dd>
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<dt><code>topology</code></dt>
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<dd>This element embodies the host internal topology. Management
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applications may want to learn this information when orchestrating new
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guests - e.g. due to reduce inter-NUMA node transfers.</dd>
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<dt><code>secmodel</code></dt>
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<dd>To find out default security labels for different security models you
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need to parse this element. In contrast with the former elements, this is
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repeated for each security model the libvirt daemon currently supports.
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</dd>
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</dl>
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<h3><a name="elementGuest">Guest capabilities</a></h3>
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<p>While the <a href="#elementHost">previous section</a> aims at host
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capabilities, this one focuses on capabilities available to a guest
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using a given hypervisor. The <code><guest/></code> element will
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typically wrap up the following elements:</p>
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<dl>
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<dt><code>os_type</code></dt>
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<dd>This expresses what kind of operating system the hypervisor
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is able to run. Possible values are:
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<dl>
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<dt>xen</dt>
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<dd>for XEN</dd>
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<dt>linux</dt>
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<dd>legacy alias for <code>xen</code></dd>
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<dt>hvm</dt>
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<dd>Unmodified operating system</dd>
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<dt>exe</dt>
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<dd>Container based virtualization</dd>
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<dt>uml</dt>
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<dd>User Mode Linux</dd>
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</dl>
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</dd>
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<dt><code>arch</code></dt>
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<dd>This element brings some information on supported guest architecture.</dd>
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<dt><code>features</code></dt>
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<dd>This optional element encases possible features that can be used
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with a guest of described type. Possible subelements are:
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<dl>
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<dt>pae</dt><dd>If present, 32-bit guests can use PAE
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address space extensions, <span class="since">since
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0.4.1</span></dd>
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<dt>nonpae</dt><dd>If present, 32-bit guests can be run
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without requiring PAE, <span class="since">since
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0.4.1</span></dd>
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<dt>ia64_be</dt><dd>If present, IA64 guests can be run in
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big-endian mode, <span class="since">since 0.4.1</span></dd>
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<dt>acpi</dt><dd>If this element is present,
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the <code>default</code> attribute describes whether the
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hypervisor exposes ACPI to the guest by default, and
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the <code>toggle</code> attribute describes whether the
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user can override this
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default. <span class="since">Since 0.4.1</span></dd>
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<dt>apic</dt><dd>If this element is present,
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the <code>default</code> attribute describes whether the
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hypervisor exposes APIC to the guest by default, and
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the <code>toggle</code> attribute describes whether the
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user can override this
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default. <span class="since">Since 0.4.1</span></dd>
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<dt>cpuselection</dt><dd>If this element is present, the
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hypervisor supports the <code><cpu></code> element
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within a domain definition for fine-grained control over
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the CPU presented to the
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guest. <span class="since">Since 0.7.5</span></dd>
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<dt>deviceboot</dt><dd>If this element is present,
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the <code><boot order='...'/></code> element can
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be used inside devices, rather than the older boot
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specification by category. <span class="since">Since
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0.8.8</span></dd>
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<dt>disksnapshot</dt><dd>If this element is present,
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the <code>default</code> attribute describes whether
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external disk snapshots are supported. If absent,
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external snapshots may still be supported, but it
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requires attempting the API and checking for an error to
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find out for sure. <span class="since">Since
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1.2.3</span></dd>
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</dl>
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</dd>
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</dl>
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<h3><a name="elementExamples">Examples</a></h3>
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<p>For example, in the case of a 64-bit machine with hardware
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virtualization capabilities enabled in the chip and
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BIOS you will see:</p>
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<pre><capabilities>
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<span style="color: #E50000"><host>
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<cpu>
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<arch>x86_64</arch>
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<features>
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<vmx/>
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</features>
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<model>core2duo</model>
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<vendor>Intel</vendor>
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<topology sockets="1" cores="2" threads="1"/>
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<feature name="lahf_lm"/>
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<feature name='xtpr'/>
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...
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</cpu>
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<power_management>
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<suspend_mem/>
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<suspend_disk/>
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<suspend_hybrid/>
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<power_management/>
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</host></span>
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<!-- xen-3.0-x86_64 -->
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<span style="color: #0000E5"><guest>
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<os_type>xen</os_type>
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<arch name="x86_64">
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<wordsize>64</wordsize>
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<domain type="xen"></domain>
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<emulator>/usr/lib64/xen/bin/qemu-dm</emulator>
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</arch>
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<features>
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</features>
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</guest></span>
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<!-- hvm-3.0-x86_32 -->
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<span style="color: #00B200"><guest>
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<os_type>hvm</os_type>
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<arch name="i686">
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<wordsize>32</wordsize>
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<domain type="xen"></domain>
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<emulator>/usr/lib/xen/bin/qemu-dm</emulator>
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<machine>pc</machine>
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<machine>isapc</machine>
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<loader>/usr/lib/xen/boot/hvmloader</loader>
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</arch>
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<features>
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<cpuselection/>
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<deviceboot/>
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</features>
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</guest></span>
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...
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</capabilities></pre>
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</body>
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</html>
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