[libvirt] CPU compare and baseline

[Edouard Thuleau]

Thanks for your help.

Ok, I didn't understand how to use "cpu-baseline", it's not clear in
the help command.
So "cpu-baseline" give me the CPU XML file I need to use to be able to
migrate between two hosts but how I use this XML file ?

Another question, why Libvirt consider CPUs with non-matching vendors
cannot be compatible ?

Doude.

On Tue, Mar 22, 2011 at 3:01 PM, Jiri Denemark <jdenemar at redhat.com> wrote:
> On Mon, Mar 21, 2011 at 18:34:40 +0100, Edouard Thuleau wrote:
>> Hi,
>> I try to understand the compare and baseline CPU commands with libvirt.
>> This functions are useful for the migration ? Before migrate a domain to
>> other host, libvirt verifies the CPU compatibility, that's right ?
> Right.
>
>> > *$ virsh cpu-baseline cpu_gargamel.xml *
>
> It's not clear what the content of cpu_gargamel.xml is. Does it contain CPU
> definitions from both hosts? virsh cpu-baseline is supposed to give you an
> intersection of the CPUs given in the XML file; it doesn't use host CPU on
> which this command is called.
>
> If you take the two host CPUs above, remove <vendor> elements (since CPUs with
> non-matching vendors are considered incompatible), and pass that to
> cpu-baseline, you will get the following guest CPU which you can use to be
> able to migrate between the two hosts:
>
> <cpu match='exact'>
>  <model>Opteron_G2</model>
>  <feature policy='require' name='ht'/>
>  <feature policy='require' name='vme'/>
>  <feature policy='disable' name='svm'/>
>  <feature policy='disable' name='rdtscp'/>
> </cpu>
>
> Note, that there is no <vendor> element there since mentioning vendor in guest
> CPU config means that you always want to run the domain on CPUs from this
> specific vendor and migrating it to another vendor will fail.
>
> Jirka
>
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