KVM: x86: Replace governed features with guest cpu_caps

[PATCH 5/9] KVM: x86: Drop unnecessary check that cpuid_entry2_find() returns right leaf

Posted by Sean Christopherson 2 years, 1 month ago

Drop an unnecessary check that cpuid_entry2_find() returns the correct
leaf when getting CPUID.0x7.0x0 to update X86_FEATURE_OSPKE, as
cpuid_entry2_find() never returns an entry for the wrong function.  And
not that it matters, but cpuid_entry2_find() will always return a precise
match for CPUID.0x7.0x0 since the index is significant.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/cpuid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 6777780be6ae..36bd04030989 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -284,7 +284,7 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
 	}
 
 	best = cpuid_entry2_find(entries, nent, 7, 0);
-	if (best && boot_cpu_has(X86_FEATURE_PKU) && best->function == 0x7)
+	if (best && boot_cpu_has(X86_FEATURE_PKU))
 		cpuid_entry_change(best, X86_FEATURE_OSPKE,
 				   kvm_is_cr4_bit_set(vcpu, X86_CR4_PKE));
 
-- 
2.42.0.869.gea05f2083d-goog

Re: [PATCH 5/9] KVM: x86: Drop unnecessary check that cpuid_entry2_find() returns right leaf

Posted by Maxim Levitsky 2 years, 1 month ago

On Fri, 2023-11-10 at 15:55 -0800, Sean Christopherson wrote:
> Drop an unnecessary check that cpuid_entry2_find() returns the correct
> leaf when getting CPUID.0x7.0x0 to update X86_FEATURE_OSPKE, as
> cpuid_entry2_find() never returns an entry for the wrong function.  And
> not that it matters, but cpuid_entry2_find() will always return a precise
> match for CPUID.0x7.0x0 since the index is significant.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  arch/x86/kvm/cpuid.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 6777780be6ae..36bd04030989 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -284,7 +284,7 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
>  	}
>  
>  	best = cpuid_entry2_find(entries, nent, 7, 0);
> -	if (best && boot_cpu_has(X86_FEATURE_PKU) && best->function == 0x7)
> +	if (best && boot_cpu_has(X86_FEATURE_PKU))
>  		cpuid_entry_change(best, X86_FEATURE_OSPKE,
>  				   kvm_is_cr4_bit_set(vcpu, X86_CR4_PKE));
>  

Makes sense.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
	Maxim Levitsky