diff options
| author | Sean Christopherson <seanjc@google.com> | 2023-03-11 01:46:05 +0100 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-04-06 23:58:43 +0200 |
| commit | 957d0f70e97bb2257d8bf746ff2f524b793751b3 (patch) | |
| tree | 672905caeae738b1aaef9219131c013290c9d6a3 /arch/x86 | |
| parent | KVM: x86/pmu: WARN and bug the VM if PMU is refreshed after vCPU has run (diff) | |
| download | linux-957d0f70e97bb2257d8bf746ff2f524b793751b3.tar.xz linux-957d0f70e97bb2257d8bf746ff2f524b793751b3.zip | |
KVM: x86/pmu: Zero out LBR capabilities during PMU refresh
Zero out the LBR capabilities during PMU refresh to avoid exposing LBRs
to the guest against userspace's wishes. If userspace modifies the
guest's CPUID model or invokes KVM_CAP_PMU_CAPABILITY to disable vPMU
after an initial KVM_SET_CPUID2, but before the first KVM_RUN, KVM will
retain the previous LBR info due to bailing before refreshing the LBR
descriptor.
Note, this is a very theoretical bug, there is no known use case where a
VMM would deliberately enable the vPMU via KVM_SET_CPUID2, and then later
disable the vPMU.
Link: https://lore.kernel.org/r/20230311004618.920745-9-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kvm/vmx/pmu_intel.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index e8a3be0b9df9..d889bb2a1de5 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -531,6 +531,16 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu) pmu->pebs_enable_mask = ~0ull; pmu->pebs_data_cfg_mask = ~0ull; + memset(&lbr_desc->records, 0, sizeof(lbr_desc->records)); + + /* + * Setting passthrough of LBR MSRs is done only in the VM-Entry loop, + * and PMU refresh is disallowed after the vCPU has run, i.e. this code + * should never be reached while KVM is passing through MSRs. + */ + if (KVM_BUG_ON(lbr_desc->msr_passthrough, vcpu->kvm)) + return; + entry = kvm_find_cpuid_entry(vcpu, 0xa); if (!entry || !vcpu->kvm->arch.enable_pmu) return; |