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

[Jiaxi Chen]

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