linux-kernel - Re: [PATCH v2 42/49] KVM: x86: Drop unnecessary check that cpuid_entry2

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Message-ID: <f8e58280c31e7f37c36277928b48a3e4bde5d795.camel@redhat.com>
Date: Thu, 04 Jul 2024 22:22:25 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>,  Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, Hou Wenlong
 <houwenlong.hwl@...group.com>, Kechen Lu <kechenl@...dia.com>, Oliver Upton
 <oliver.upton@...ux.dev>, Binbin Wu <binbin.wu@...ux.intel.com>, Yang
 Weijiang <weijiang.yang@...el.com>, Robert Hoo <robert.hoo.linux@...il.com>
Subject: Re: [PATCH v2 42/49] KVM: x86: Drop unnecessary check that
 cpuid_entry2_find() returns right leaf

On Fri, 2024-05-17 at 10:39 -0700, Sean Christopherson wrote:
> Drop an unnecessary check that kvm_find_cpuid_entry_index(), i.e.
> cpuid_entry2_find(), returns the correct leaf when getting CPUID.0x7.0x0
> to update X86_FEATURE_OSPKE.  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.
> 
> Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
> 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 258c5fce87fc..8256fc657c6b 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -351,7 +351,7 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
>  	}
>  
>  	best = kvm_find_cpuid_entry_index(vcpu, 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));
>  

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

Best regards,
	Maxim Levitsky