Add option to skip cpu feature and model verification in libvirt and rely on qemu 'enforce' option

[manish.mishra]

On 24/11/22 5:40 pm, Jiri Denemark wrote:
> On Wed, Nov 23, 2022 at 18:34:38 +0530, manish.mishra wrote:
>> oh i see you meant something like this,
>>
>>     <cpu mode='custom' match='exact' check='none'>
>>       <numa>
>>         <cell id='0' cpus='0-239' memory='8388608' unit='KiB' memAccess='shared'/>
>>       </numa>
>>     </cpu>
>>
>>     <qemu:commandline>
>>       <qemu:arg value='-cpu'/>
>>       <qemu:arg value='enforce,Icelake-v4,x2apic=on,hv-time,kvm-pv-eoi=on'/>
>>     </qemu:commandline>
> This won't work as libvirt should add a default CPU model there and
> replace check='none' with check='full' once the domain starts.
>
> But we actually have a way to do what you need even without any change
> in libvirt:
>
>    <cpu mode='host-passthrough' check='none'>
>      <topology .../>
>      <numa>
>        ...
>      </numa>
>      ...
>    </cpu>
>
>    <qemu:commandline>
>      <qemu:arg value='-cpu'/>
>      <qemu:arg value='Icelake-Server-v4,enforce,x2apic=on,hv-time,kvm-pv-eoi=on'/>
>    </qemu:commandline>
>
> This will result in
>
>    -cpu host,migratable=on
>    ...
>    -cpu Icelake-Server-v4,enforce,x2apic=on,hv-time,kvm-pv-eoi=on
>
> and libvirt will not touch the check='none' attribute once the domain
> starts and it would not complain about any unknown CPU features or
> models as there's nothing to check in <cpu/>.
>
> That is, there's no need to come up with anything special to support
> passing arbitrary options to -cpu.
>
> Jirka


Thank you so much Jirka, let me give this a try with few different cases. I will let you know how this goes or if we need anything extra.

Thanks

Manish Mishra
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