Re: [PATCH v2 37/49] KVM: x86: Replace guts of "governed" features with comprehensive cpu_caps

[Yang, Weijiang]

On 5/18/2024 1:39 AM, Sean Christopherson wrote:

[...]

> index e021681f34ac..ad0168d3aec5 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -259,10 +259,10 @@ static __always_inline bool kvm_is_governed_feature(unsigned int x86_feature)
>   static __always_inline void guest_cpu_cap_set(struct kvm_vcpu *vcpu,
>   					      unsigned int x86_feature)
>   {
> -	BUILD_BUG_ON(!kvm_is_governed_feature(x86_feature));
> +	unsigned int x86_leaf = __feature_leaf(x86_feature);
>   
> -	__set_bit(kvm_governed_feature_index(x86_feature),
> -		  vcpu->arch.governed_features.enabled);
> +	reverse_cpuid_check(x86_leaf);

This reverse_cpuid_check() seems unnecessary since in patch(17), we already have moved it in
 __feature_leaf(). But I don't have full source code to double check it now.

> +	vcpu->arch.cpu_caps[x86_leaf] |= __feature_bit(x86_feature);
>   }
>   
>   static __always_inline void guest_cpu_cap_check_and_set(struct kvm_vcpu *vcpu,
> @@ -275,10 +275,10 @@ static __always_inline void guest_cpu_cap_check_and_set(struct kvm_vcpu *vcpu,
>   static __always_inline bool guest_cpu_cap_has(struct kvm_vcpu *vcpu,
>   					      unsigned int x86_feature)
>   {
> -	BUILD_BUG_ON(!kvm_is_governed_feature(x86_feature));
> +	unsigned int x86_leaf = __feature_leaf(x86_feature);
>   
> -	return test_bit(kvm_governed_feature_index(x86_feature),
> -			vcpu->arch.governed_features.enabled);
> +	reverse_cpuid_check(x86_leaf);

Ditto.

> +	return vcpu->arch.cpu_caps[x86_leaf] & __feature_bit(x86_feature);
>   }
>   
[...]