Re: [PATCH v2 2/2] KVM: SVM: Add support for Virtual SPEC_CTRL

[Sean Christopherson]

On Wed, Dec 30, 2020, Borislav Petkov wrote:
> 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() ?

Nope, they can definitely use boot_cpu_has().