Re: [PATCH 1/6] x86: KVM: Enable CMPccXADD CPUID and expose it to guest

Jiaxi Chen
2022-10-27T02:28:09Z

On 10/27/2022 1:15 AM, Borislav Petkov wrote:
> On Wed, Oct 26, 2022 at 11:40:31AM +0800, Jiaxi Chen wrote:
>>> What do you think about moving CPUID_7_1_EAX to be a KVM-only leaf too? AFAICT,
>>> KVM passthrough is the only reason the existing features are defined.
>
> Yap, looking at the patches which added those 2 feature flags upstream,
> they don't look like some particular use was the goal but rather to
> expose it to guests. Besides, AVX512 apps do their own CPUID detection.
>
>> Since CPUID_7_1_EAX has only 5 features now, it is a big waste,
>> should we move it to KVM-only leaf as Sean suggested. What's your
>> opinion about this?
>
> Yes, pls do.
>
> And when you do, make sure to undo what
>
> b302e4b176d0 ("x86/cpufeatures: Enumerate the new AVX512 BFLOAT16 instructions")
>
> added.
>
> Thx.
>

Yes, will do this in v2. Thanks for reminding~
--
Regards,
Jiaxi