linux-kernel - Re: [PATCH 5/9] KVM: x86: Drop unnecessary check that cpuid_entry2

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Message-ID: <5adae6067e0d05a4421616f9153bc865cd200a15.camel@redhat.com>
Date:   Sun, 19 Nov 2023 19:33:11 +0200
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/9] KVM: x86: Drop unnecessary check that
 cpuid_entry2_find() returns right leaf

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@...gle.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@...hat.com>

Best regards,
	Maxim Levitsky