linux-kernel - Re: [PATCH v11 07/11] KVM: x86: Expose MSR_IA32_PERF

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Message-ID: <20200519105335.GF279861@hirez.programming.kicks-ass.net>
Date:   Tue, 19 May 2020 12:53:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Like Xu <like.xu@...ux.intel.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>, ak@...ux.intel.com,
        wei.w.wang@...el.com
Subject: Re: [PATCH v11 07/11] KVM: x86: Expose MSR_IA32_PERF_CAPABILITIES
 for LBR record format

On Thu, May 14, 2020 at 04:30:50PM +0800, Like Xu wrote:
> @@ -203,6 +206,12 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  	case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
>  		msr_info->data = pmu->global_ovf_ctrl;
>  		return 0;
> +	case MSR_IA32_PERF_CAPABILITIES:
> +		if (!msr_info->host_initiated &&
> +			!guest_cpuid_has(vcpu, X86_FEATURE_PDCM))
> +			return 1;

I know this is KVM code, so maybe they feel differently, but I find the
above indentation massively confusing. Consider using: "set cino=:0(0"
if you're a vim user.

> +		msr_info->data = vcpu->arch.perf_capabilities;
> +		return 0;
>  	default:
>  		if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0))) {
>  			u64 val = pmc_read_counter(pmc);
> @@ -261,6 +270,16 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  			return 0;
>  		}
>  		break;
> +	case MSR_IA32_PERF_CAPABILITIES:
> +		if (!msr_info->host_initiated ||
> +			!guest_cpuid_has(vcpu, X86_FEATURE_PDCM))
> +			return 1;

Idem.

> +		if (!(data & ~vmx_get_perf_capabilities()))
> +			return 1;
> +		if ((data ^ vmx_get_perf_capabilities()) & PERF_CAP_LBR_FMT)
> +			return 1;
> +		vcpu->arch.perf_capabilities = data;
> +		return 0;
>  	default:
>  		if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0))) {
>  			if (!msr_info->host_initiated)