linux-kernel - Re: [RFC PATCH 34/41] KVM: x86/pmu: Intercept EVENT

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Date: Thu, 11 Apr 2024 14:55:59 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Xiong Zhang <xiong.y.zhang@...ux.intel.com>
Cc: pbonzini@...hat.com, peterz@...radead.org, mizhang@...gle.com, 
	kan.liang@...el.com, zhenyuw@...ux.intel.com, dapeng1.mi@...ux.intel.com, 
	jmattson@...gle.com, kvm@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, zhiyuan.lv@...el.com, eranian@...gle.com, 
	irogers@...gle.com, samantha.alt@...el.com, like.xu.linux@...il.com, 
	chao.gao@...el.com, Xiong Zhang <xiong.y.zhang@...el.com>
Subject: Re: [RFC PATCH 34/41] KVM: x86/pmu: Intercept EVENT_SELECT MSR

On Fri, Jan 26, 2024, Xiong Zhang wrote:
> From: Xiong Zhang <xiong.y.zhang@...el.com>
> 
> Event selectors for GP counters are still intercepted for the purpose of
> security, i.e., preventing guest from using unallowed events to steal
> information or take advantages of any CPU errata.

Heh, so then they shouldn't have been passed through in the first place.

> Signed-off-by: Xiong Zhang <xiong.y.zhang@...el.com>
> Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
> ---
>  arch/x86/kvm/vmx/pmu_intel.c | 1 -
>  arch/x86/kvm/vmx/vmx.c       | 1 -
>  2 files changed, 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> index 9bbd5084a766..621922005184 100644
> --- a/arch/x86/kvm/vmx/pmu_intel.c
> +++ b/arch/x86/kvm/vmx/pmu_intel.c
> @@ -809,7 +809,6 @@ void intel_passthrough_pmu_msrs(struct kvm_vcpu *vcpu)
>  	int i;
>  
>  	for (i = 0; i < vcpu_to_pmu(vcpu)->nr_arch_gp_counters; i++) {
> -		vmx_set_intercept_for_msr(vcpu, MSR_ARCH_PERFMON_EVENTSEL0 + i, MSR_TYPE_RW, false);
>  		vmx_set_intercept_for_msr(vcpu, MSR_IA32_PERFCTR0 + i, MSR_TYPE_RW, false);
>  		if (fw_writes_is_enabled(vcpu))
>  			vmx_set_intercept_for_msr(vcpu, MSR_IA32_PMC0 + i, MSR_TYPE_RW, false);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d28afa87be70..1a518800d154 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -698,7 +698,6 @@ static bool is_valid_passthrough_msr(u32 msr)
>  	case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 8:
>  	case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 8:
>  		/* LBR MSRs. These are handled in vmx_update_intercept_for_lbr_msrs() */
> -	case MSR_ARCH_PERFMON_EVENTSEL0 ... MSR_ARCH_PERFMON_EVENTSEL0 + 7:
>  	case MSR_IA32_PMC0 ... MSR_IA32_PMC0 + 7:
>  	case MSR_IA32_PERFCTR0 ... MSR_IA32_PERFCTR0 + 7:
>  	case MSR_CORE_PERF_FIXED_CTR_CTRL:
> -- 
> 2.34.1
>