Re: [PATCH 2/6] x86: KVM: Enable AMX-FP16 CPUID and expose it to guest

Paolo Bonzini
2022-11-02T18:17:44Z

On 11/2/22 19:14, Dave Hansen wrote:
>>
>> kvm_cpu_cap_mask(CPUID_7_1_EAX,
>> - F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD)
>> + F(AVX_VNNI) | F(AVX512_BF16) | F(CMPCCXADD) | F(AMX_FP16)
>> );
>>
>> kvm_cpu_cap_mask(CPUID_D_1_EAX,
>
> KVM folks, is the idea that every feature that is enumerated to a guest
> needs to be in one of these masks? Or is there something special about
> the features in these masks?

Yes, all features are vetted manually to see whether they require new
MSRs and the like. Therefore, anything that userspace can set in the
guest's CPUID must be in the list.

Paolo