[libvirt] What is the strategy to update the CPU Models in src/cpu/cpu_map.xml based on?

[Dou Liyang]

Hi Jiri,

At 05/30/2018 06:14 PM, Jiri Denemark wrote:
> [Dropping random people from Cc]
> 
> On Wed, May 30, 2018 at 18:00:56 +0800, Dou Liyang wrote:
>> Hi All,
>>
>> I am not sure about the update strategy of CPU models in libvirt.
>>
>> IMO, It's depend on the CPU model in qemu-kvm, if some CPU models
>> were updated in qemu-kvm. Then, we should modify the src/cpu/cpu_map.xml
>> of libvirt to synchronize?
> 
> No, we never change existing CPU models in cpu_map.xml to make sure the
> same CPU model is the same across libvirt versions. Not to mention that
> QEMU only changes existing CPU models for new machine type (for the same
> compatibility reason) so we can't just change our CPU models since we
> don't know what machine type their going to be used with. Libvirt will
> handle the differences in runtime by remembering any additionally
> enabled or disabled features once domain starts to make sure the exact
> same CPU is recreated after, e.g., migration.
> 

I see.

Btw, If we found there is a wrong feature in the existing CPU models,
what should we do?

If we add a new CPU model, what we refer to? CPU models spec or
hypervisors' code(eg, qemu-kvm)

Thanks,
	dou

> Jirka
> 
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