diff options
| author | Sean Christopherson <seanjc@google.com> | 2023-03-11 01:46:04 +0100 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-04-06 23:58:43 +0200 |
| commit | 3a6de51a437fb4d2433f8a99fb59f43866cdbb98 (patch) | |
| tree | 1371bd9dfa246de0d6a82829b7c535e6a6eb61c4 /arch/x86 | |
| parent | KVM: x86: Disallow writes to immutable feature MSRs after KVM_RUN (diff) | |
| download | linux-3a6de51a437fb4d2433f8a99fb59f43866cdbb98.tar.xz linux-3a6de51a437fb4d2433f8a99fb59f43866cdbb98.zip | |
KVM: x86/pmu: WARN and bug the VM if PMU is refreshed after vCPU has run
Now that KVM disallows changing feature MSRs, i.e. PERF_CAPABILITIES,
after running a vCPU, WARN and bug the VM if the PMU is refreshed after
the vCPU has run.
Note, KVM has disallowed CPUID updates after running a vCPU since commit
feb627e8d6f6 ("KVM: x86: Forbid KVM_SET_CPUID{,2} after KVM_RUN"), i.e.
PERF_CAPABILITIES was the only remaining way to trigger a PMU refresh
after KVM_RUN.
Cc: Like Xu <like.xu.linux@gmail.com>
Link: https://lore.kernel.org/r/20230311004618.920745-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/pmu.c | 3 | ||||
| -rw-r--r-- | arch/x86/kvm/x86.c | 10 |
2 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index 29492c2a0c82..136184fe9e92 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -589,6 +589,9 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) */ void kvm_pmu_refresh(struct kvm_vcpu *vcpu) { + if (KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm)) + return; + bitmap_zero(vcpu_to_pmu(vcpu)->all_valid_pmc_idx, X86_PMC_IDX_MAX); static_call(kvm_x86_pmu_refresh)(vcpu); } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index cf33b7d910a6..a86ad45a53b8 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3632,9 +3632,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) if (data & ~kvm_caps.supported_perf_cap) return 1; + /* + * Note, this is not just a performance optimization! KVM + * disallows changing feature MSRs after the vCPU has run; PMU + * refresh will bug the VM if called after the vCPU has run. + */ + if (vcpu->arch.perf_capabilities == data) + break; + vcpu->arch.perf_capabilities = data; kvm_pmu_refresh(vcpu); - return 0; + break; case MSR_EFER: return set_efer(vcpu, msr_info); case MSR_K7_HWCR: |