2024-01-26 14:55:20

by Zhang, Xiong Y

Subject: [RFC PATCH 34/41] KVM: x86/pmu: Intercept EVENT_SELECT MSR

From: Xiong Zhang <[email protected]>

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.

Signed-off-by: Xiong Zhang <[email protected]>
Signed-off-by: Mingwei Zhang <[email protected]>
---
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

2024-04-11 21:56:34

by Sean Christopherson

Subject: Re: [RFC PATCH 34/41] KVM: x86/pmu: Intercept EVENT_SELECT MSR

On Fri, Jan 26, 2024, Xiong Zhang wrote:
> From: Xiong Zhang <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Mingwei Zhang <[email protected]>
> ---
> 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
>