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Peter Anvin" , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Yongwei Ma , Xiong Zhang , Dapeng Mi , Jim Mattson , Sandipan Das , Zide Chen , Eranian Stephane , Shukla Manali , Nikunj Dadhania Content-Type: text/plain; charset="us-ascii" Again, be more precise. On Mon, Mar 24, 2025, Mingwei Zhang wrote: > From: Dapeng Mi > > Mediated vPMU needs to intercept EVENTSELx and FIXED_CNTR_CTRL MSRs to > filter out guest malicious perf events. Either writing these MSRs or > updating event filters would call reprogram_counter() eventually. Thus > check if the guest event should be filtered out in reprogram_counter(). > If so, clear corresponding EVENTSELx MSR or FIXED_CNTR_CTRL field to > ensure the guest event won't be really enabled at vm-entry. > > Besides, mediated vPMU intercepts the MSRs of these guest not owned > counters and it just needs simply to read/write from/to pmc->counter. > > Suggested-by: Sean Christopherson > Signed-off-by: Dapeng Mi > Co-developed-by: Mingwei Zhang > Signed-off-by: Mingwei Zhang > --- > arch/x86/kvm/pmu.c | 27 +++++++++++++++++++++++++++ > arch/x86/kvm/pmu.h | 3 +++ > 2 files changed, 30 insertions(+) > > diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c > index 63143eeb5c44..e9100dc49fdc 100644 > --- a/arch/x86/kvm/pmu.c > +++ b/arch/x86/kvm/pmu.c > @@ -305,6 +305,11 @@ static void pmc_update_sample_period(struct kvm_pmc *pmc) > > void pmc_write_counter(struct kvm_pmc *pmc, u64 val) > { > + if (kvm_mediated_pmu_enabled(pmc->vcpu)) { > + pmc->counter = val & pmc_bitmask(pmc); > + return; > + } > + > /* > * Drop any unconsumed accumulated counts, the WRMSR is a write, not a > * read-modify-write. Adjust the counter value so that its value is > @@ -455,6 +460,28 @@ static int reprogram_counter(struct kvm_pmc *pmc) > bool emulate_overflow; > u8 fixed_ctr_ctrl; > > + if (kvm_mediated_pmu_enabled(pmu_to_vcpu(pmu))) { > + bool allowed = check_pmu_event_filter(pmc); > + > + if (pmc_is_gp(pmc)) { > + if (allowed) > + pmc->eventsel_hw |= pmc->eventsel & > + ARCH_PERFMON_EVENTSEL_ENABLE; > + else > + pmc->eventsel_hw &= ~ARCH_PERFMON_EVENTSEL_ENABLE; > + } else { > + int idx = pmc->idx - KVM_FIXED_PMC_BASE_IDX; > + > + if (allowed) > + pmu->fixed_ctr_ctrl_hw = pmu->fixed_ctr_ctrl; > + else > + pmu->fixed_ctr_ctrl_hw &= > + ~intel_fixed_bits_by_idx(idx, 0xf); > + } > + > + return 0; I think it's worth adding a helper for this, as it makes things a bit more self-documenting in terms of when KVM needs to "reprogram" mediated PMU PMCs.