Re: [PATCH v2 06/15] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_CTL for guest Arch LBR

[Yang, Weijiang]

On 12/22/2022 7:09 PM, Like Xu wrote:
> On 25/11/2022 12:05 pm, Yang Weijiang wrote:
> >   static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data 
> > *msr_info)
> >   {
> >       struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
> > @@ -377,6 +402,14 @@ static int intel_pmu_get_msr(struct kvm_vcpu 
> > *vcpu, struct msr_data *msr_info)
> >       case MSR_ARCH_LBR_DEPTH:
> >           msr_info->data = lbr_desc->records.nr;
> >           return 0;
> > +    case MSR_ARCH_LBR_CTL:
> > +        if (!kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR)) {
> > +            WARN_ON_ONCE(!msr_info->host_initiated);
>
> Why we need this warning even in the format of WARN_ON_ONCE() ?
> And why not for MSR_ARCH_LBR_DEPTH msr ?


IMO, this is just to give some informative message. Not necessary for every

arch-lbr MSRs as MSR_ARCH_LBR_CTL is the master control msr.



> > +            msr_info->data = 0;
> > +        } else {
> > +            msr_info->data = vmcs_read64(GUEST_IA32_LBR_CTL);
> > +        }
> > +        return 0;