2024-01-26 12:17:37

by Zhang, Xiong Y

Subject: [RFC PATCH 36/41] KVM: x86/pmu: Intercept FIXED_CTR_CTRL MSR

From: Xiong Zhang <[email protected]>

Fixed counters control MSR are still intercepted for the purpose of
security, i.e., preventing guest from using unallowed Fixed Counter
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 92c5baed8d36..713c2a7c7f07 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -825,7 +825,6 @@ void intel_passthrough_pmu_msrs(struct kvm_vcpu *vcpu)
vmx_set_intercept_for_msr(vcpu, MSR_IA32_PMC0 + i, MSR_TYPE_RW, false);
}

- vmx_set_intercept_for_msr(vcpu, MSR_CORE_PERF_FIXED_CTR_CTRL, MSR_TYPE_RW, false);
for (i = 0; i < vcpu_to_pmu(vcpu)->nr_arch_fixed_counters; i++)
vmx_set_intercept_for_msr(vcpu, MSR_CORE_PERF_FIXED_CTR0 + i, MSR_TYPE_RW, false);

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1a518800d154..7c4e1feb589b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -700,7 +700,6 @@ static bool is_valid_passthrough_msr(u32 msr)
/* LBR MSRs. These are handled in vmx_update_intercept_for_lbr_msrs() */
case MSR_IA32_PMC0 ... MSR_IA32_PMC0 + 7:
case MSR_IA32_PERFCTR0 ... MSR_IA32_PERFCTR0 + 7:
- case MSR_CORE_PERF_FIXED_CTR_CTRL:
case MSR_CORE_PERF_FIXED_CTR0 ... MSR_CORE_PERF_FIXED_CTR0 + 2:
case MSR_CORE_PERF_GLOBAL_STATUS:
case MSR_CORE_PERF_GLOBAL_CTRL:
--
2.34.1

2024-04-11 21:57:11

by Sean Christopherson

Subject: Re: [RFC PATCH 36/41] KVM: x86/pmu: Intercept FIXED_CTR_CTRL MSR

On Fri, Jan 26, 2024, Xiong Zhang wrote:
> From: Xiong Zhang <[email protected]>
>
> Fixed counters control MSR are still intercepted for the purpose of
> security, i.e., preventing guest from using unallowed Fixed Counter
> to steal information or take advantages of any CPU errata.

Same comments as earlier patches. Don't introduce bugs and then immediately fix
said bugs.