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Date:   Wed, 30 Dec 2020 08:15:01 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Babu Moger <babu.moger@....com>
Cc:     pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        fenghua.yu@...el.com, tony.luck@...el.com, wanpengli@...cent.com,
        kvm@...r.kernel.org, thomas.lendacky@....com, peterz@...radead.org,
        seanjc@...gle.com, joro@...tes.org, x86@...nel.org,
        kyung.min.park@...el.com, linux-kernel@...r.kernel.org,
        krish.sadhukhan@...cle.com, hpa@...or.com, mgross@...ux.intel.com,
        vkuznets@...hat.com, kim.phillips@....com, wei.huang2@....com,
        jmattson@...gle.com
Subject: Re: [PATCH v2 2/2] KVM: SVM: Add support for Virtual SPEC_CTRL

On Tue, Dec 22, 2020 at 04:31:55PM -0600, Babu Moger wrote:
> @@ -2549,7 +2559,10 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  		    !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
>  			return 1;
>  
> -		msr_info->data = svm->spec_ctrl;
> +		if (static_cpu_has(X86_FEATURE_V_SPEC_CTRL))
> +			msr_info->data = svm->vmcb->save.spec_ctrl;
> +		else
> +			msr_info->data = svm->spec_ctrl;
>  		break;
>  	case MSR_AMD64_VIRT_SPEC_CTRL:
>  		if (!msr_info->host_initiated &&
> @@ -2640,6 +2653,8 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
>  			return 1;
>  
>  		svm->spec_ctrl = data;
> +		if (static_cpu_has(X86_FEATURE_V_SPEC_CTRL))
> +			svm->vmcb->save.spec_ctrl = data;
>  		if (!data)
>  			break;
>  

Are the get/set_msr() accessors such a fast path that they need
static_cpu_has() ?

svm_get_msr() already uses boot_cpu_has() for MSR_TSC_AUX...

-- 
Regards/Gruss,
    Boris.

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