Again, be more precise.
On Mon, Mar 24, 2025, Mingwei Zhang wrote:
From: Dapeng Mi dapeng1.mi@linux.intel.com
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 seanjc@google.com Signed-off-by: Dapeng Mi dapeng1.mi@linux.intel.com Co-developed-by: Mingwei Zhang mizhang@google.com Signed-off-by: Mingwei Zhang mizhang@google.com
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;elsepmc->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;elsepmu->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.