linux-kernel - Re: [PATCH v2 06/15] KVM: vmx/pmu: Emulate MSR_ARCH_LBR

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Date:   Thu, 22 Dec 2022 19:19:33 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Yang Weijiang <weijiang.yang@...el.com>
Cc:     kan.liang@...ux.intel.com, wei.w.wang@...el.com, seanjc@...gle.com,
        pbonzini@...hat.com, jmattson@...gle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/15] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_CTL for guest
 Arch LBR

On 25/11/2022 12:05 pm, Yang Weijiang wrote:
> @@ -727,12 +772,16 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
>    */
>   static void intel_pmu_legacy_freezing_lbrs_on_pmi(struct kvm_vcpu *vcpu)
>   {
> -	u64 data = vmcs_read64(GUEST_IA32_DEBUGCTL);
> +	u32 lbr_ctl_field = GUEST_IA32_DEBUGCTL;
>   
> -	if (data & DEBUGCTLMSR_FREEZE_LBRS_ON_PMI) {
> -		data &= ~DEBUGCTLMSR_LBR;
> -		vmcs_write64(GUEST_IA32_DEBUGCTL, data);
> -	}
> +	if (!(vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_FREEZE_LBRS_ON_PMI))
> +		return;
> +
> +	if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR) &&
> +	    guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
> +		lbr_ctl_field = GUEST_IA32_LBR_CTL;
> +
> +	vmcs_write64(lbr_ctl_field, vmcs_read64(lbr_ctl_field) & ~0x1ULL);
>   }
>   
>   static void intel_pmu_deliver_pmi(struct kvm_vcpu *vcpu)

The legacy lbr test case in KUT does not cover this scenario, but
arch lbr contributor should take the opportunity to fill this gap. Thanks.