linux-kernel - Re: [PATCH v2 05/15] KVM: vmx/pmu: Emulate MSR_ARCH_LBR

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Message-ID: <a7c09bc6-8d80-3028-1cea-ee355b41109d@gmail.com>
Date:   Thu, 22 Dec 2022 19:15:33 +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 05/15] KVM: vmx/pmu: Emulate MSR_ARCH_LBR_DEPTH for
 guest Arch LBR

On 25/11/2022 12:05 pm, Yang Weijiang wrote:
> +static bool cpuid_enable_lbr(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
> +	struct kvm_cpuid_entry2 *entry;
> +	int depth_bit;
> +
> +	if (!kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR))
> +		return !static_cpu_has(X86_FEATURE_ARCH_LBR) &&
> +			cpuid_model_is_consistent(vcpu);

Please add selftests to cover this incompatibility.

And running the SPR vcpu model on a GNR host, the guest arch lbr
should be fully supported as long as both hosts have the same lbr_depth.