[PATCH v5 35/44] KVM: x86/pmu: Reprogram mediated PMU event selectors on event filter updates
From: Sean Christopherson <seanjc@google.com>
Date: 2025-08-06 19:58:32
Also in:
kvm, kvm-riscv, kvmarm, linux-perf-users, linux-riscv, lkml, loongarch
Subsystem:
kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Dapeng Mi <redacted> Refresh the event selectors that are programmed into hardware when a PMC is "reprogrammed" for a mediated PMU, i.e. if userspace changes the PMU event filters Note, KVM doesn't utilize the reprogramming infrastructure to handle counter overflow for mediated PMUs, as there's no need to reprogram a non-existent perf event. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Dapeng Mi <redacted> Co-developed-by: Mingwei Zhang <redacted> Signed-off-by: Mingwei Zhang <redacted> [sean: add a helper to document behavior, split patch and rewrite changelog] Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/pmu.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index e39ae37f0280..b4c6a7704a01 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c@@ -518,6 +518,25 @@ static bool pmc_is_event_allowed(struct kvm_pmc *pmc) return is_fixed_event_allowed(filter, pmc->idx); } +static void kvm_mediated_pmu_refresh_event_filter(struct kvm_pmc *pmc) +{ + bool allowed = pmc_is_event_allowed(pmc); + struct kvm_pmu *pmu = pmc_to_pmu(pmc); + + if (pmc_is_gp(pmc)) { + pmc->eventsel_hw &= ~ARCH_PERFMON_EVENTSEL_ENABLE; + if (allowed) + pmc->eventsel_hw |= pmc->eventsel & + ARCH_PERFMON_EVENTSEL_ENABLE; + } else { + u64 mask = intel_fixed_bits_by_idx(pmc->idx - KVM_FIXED_PMC_BASE_IDX, 0xf); + + pmu->fixed_ctr_ctrl_hw &= ~mask; + if (allowed) + pmu->fixed_ctr_ctrl_hw |= pmu->fixed_ctr_ctrl & mask; + } +} + static int reprogram_counter(struct kvm_pmc *pmc) { struct kvm_pmu *pmu = pmc_to_pmu(pmc);
@@ -526,6 +545,11 @@ static int reprogram_counter(struct kvm_pmc *pmc) bool emulate_overflow; u8 fixed_ctr_ctrl; + if (kvm_vcpu_has_mediated_pmu(pmu_to_vcpu(pmu))) { + kvm_mediated_pmu_refresh_event_filter(pmc); + return 0; + } + emulate_overflow = pmc_pause_counter(pmc); if (!pmc_is_globally_enabled(pmc) || !pmc_is_locally_enabled(pmc) ||
--
2.50.1.565.gc32cd1483b-goog