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This patch exports KVM Host Power Management capabilities as XML so that higher-level systems management software can make use of these features available in the host. The script "pm-is-supported" (from pm-utils package) is run to discover if Suspend-to-RAM (S3) or Suspend-to-Disk (S4) is supported by the host. If either of them are supported, then a new tag "<power_management>" is introduced in the XML under the <host> tag. However in case the query to check for power management features succeeded, but the host does not support any such feature, then the XML will contain an empty <power_management/> tag. In the event that the PM query itself failed, the XML will not contain any "power_management" tag. To use this, new APIs could be implemented in libvirt to exploit power management features such as S3/S4.
89 lines
3.9 KiB
HTML
89 lines
3.9 KiB
HTML
<html>
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<body>
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<h1>Driver capabilities XML format</h1>
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<p>As new virtualization engine support gets added to libvirt, and to handle
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cases like QEmu supporting a variety of emulations, a query interface has
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been added in 0.2.1 allowing to list the set of supported virtualization
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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. For example in the case of a 64 bits
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machine with hardware 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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<S3/>
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<S4/>
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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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<p>The first block (in red) indicates the host hardware capabilities, currently
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it is limited to the CPU properties and the power management features of
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the host platform, but other information may be available, it shows the CPU architecture,
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topology, model name, and additional features which are not included in the model but the
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CPU provides them. Features of the chip are shown within the feature block (the block is
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similar to what you will find in a Xen fully virtualized domain description). Further,
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the power management features supported by the host are shown, such as Suspend-to-RAM (S3)
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and Suspend-to-Disk (S4). In case the query for power management features succeeded but the
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host does not support any such feature, then an empty <power_management/>
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tag will be shown. Otherwise, if the query itself failed, no such tag will
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be displayed (i.e., there will not be any power_management block or empty tag in the XML).</p>
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<p>The second block (in blue) indicates the paravirtualization support of the
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Xen support, you will see the os_type of xen to indicate a paravirtual
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kernel, then architecture information and potential features.</p>
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<p>The third block (in green) gives similar information but when running a
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32 bit OS fully virtualized with Xen using the hvm support.</p>
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<p>This section is likely to be updated and augmented in the future, see <a href="https://www.redhat.com/archives/libvir-list/2007-March/msg00215.html">the
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discussion</a> which led to the capabilities format in the mailing-list
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archives.</p>
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</body>
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</html>
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