linux-kernel - Re: [PATCH 2/2] KVM: SVM: Simplify MSR interception logic for IA32

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Message-ID: <1822390b-468b-400d-b6e5-d936372653e1@linux.intel.com>
Date: Wed, 25 Jun 2025 15:20:03 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Chao Gao <chao.gao@...el.com>, linux-kernel@...r.kernel.org,
 kvm@...r.kernel.org
Cc: seanjc@...gle.com, pbonzini@...hat.com, dapeng1.mi@...ux.intel.com
Subject: Re: [PATCH 2/2] KVM: SVM: Simplify MSR interception logic for
 IA32_XSS MSR



On 6/12/2025 4:19 PM, Chao Gao wrote:
> Use svm_set_intercept_for_msr() directly to configure IA32_XSS MSR
> interception, ensuring consistency with other cases where MSRs are
> intercepted depending on guest caps and CPUIDs.
>
> No functional change intended.
>
> Signed-off-by: Chao Gao <chao.gao@...el.com>

Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>

> ---
> With this patch applied, svm_enable_intercept_for_msr() has no user.
> Should it be removed?
> ---
>   arch/x86/kvm/svm/sev.c | 8 +++-----
>   1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 6282c2930cda..504e8a87644a 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -4371,11 +4371,9 @@ void sev_es_recalc_msr_intercepts(struct kvm_vcpu *vcpu)
>   	 * XSAVES being exposed to the guest so that KVM can at least honor
>   	 * guest CPUID for RDMSR and WRMSR.
>   	 */
> -	if (guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) &&
> -	    guest_cpuid_has(vcpu, X86_FEATURE_XSAVES))
> -		svm_disable_intercept_for_msr(vcpu, MSR_IA32_XSS, MSR_TYPE_RW);
> -	else
> -		svm_enable_intercept_for_msr(vcpu, MSR_IA32_XSS, MSR_TYPE_RW);
> +	svm_set_intercept_for_msr(vcpu, MSR_IA32_XSS, MSR_TYPE_RW,
> +				  !guest_cpu_cap_has(vcpu, X86_FEATURE_XSAVES) ||
> +				  !guest_cpuid_has(vcpu, X86_FEATURE_XSAVES));
>   }
>   
>   void sev_vcpu_after_set_cpuid(struct vcpu_svm *svm)