Re: [PATCH][v6] KVM: X86: support APERF/MPERF registers

[Paolo Bonzini]

On 05/06/20 19:16, Jim Mattson wrote:
>>>> @@ -4930,6 +4939,11 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>>>>           kvm->arch.exception_payload_enabled = cap->args[0];
>>>>           r = 0;
>>>>           break;
>>>> +    case KVM_CAP_APERFMPERF:
>>>> +        kvm->arch.aperfmperf_mode =
>>>> +            boot_cpu_has(X86_FEATURE_APERFMPERF) ? cap->args[0] : 0;
>>> Shouldn't check whether cap->args[0] is a valid value?
>> Yes, only valid values should be allowed.
>>
>> Also, it should fail with -EINVAL if the host does not have
>> X86_FEATURE_APERFMPERF.
> Should enabling/disabling this capability be disallowed once vCPUs
> have been created?
> 

That's a good idea, yes.

Paolo