From d2b321ea9380564510d281d45ccd2b424da14e7f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 9 Nov 2023 18:28:53 -0800 Subject: [PATCH] KVM: x86/pmu: Process only enabled PMCs when emulating events in software Mask off disabled counters based on PERF_GLOBAL_CTRL *before* iterating over PMCs to emulate (branch) instruction required events in software. In the common case where the guest isn't utilizing the PMU, pre-checking for enabled counters turns a relatively expensive search into a few AND uops and a Jcc. Sadly, PMUs without PERF_GLOBAL_CTRL, e.g. most existing AMD CPUs, are out of luck as there is no way to check that a PMC isn't being used without checking the PMC's event selector. Cc: Konstantin Khorenko Link: https://lore.kernel.org/r/20231110022857.1273836-7-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/pmu.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index 7b5563ff259ce..c04c3f37a1b8c 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -847,11 +847,20 @@ static inline bool cpl_is_matched(struct kvm_pmc *pmc) void kvm_pmu_trigger_event(struct kvm_vcpu *vcpu, u64 perf_hw_id) { + DECLARE_BITMAP(bitmap, X86_PMC_IDX_MAX); struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); struct kvm_pmc *pmc; int i; - kvm_for_each_pmc(pmu, pmc, i, pmu->all_valid_pmc_idx) { + BUILD_BUG_ON(sizeof(pmu->global_ctrl) * BITS_PER_BYTE != X86_PMC_IDX_MAX); + + if (!kvm_pmu_has_perf_global_ctrl(pmu)) + bitmap_copy(bitmap, pmu->all_valid_pmc_idx, X86_PMC_IDX_MAX); + else if (!bitmap_and(bitmap, pmu->all_valid_pmc_idx, + (unsigned long *)&pmu->global_ctrl, X86_PMC_IDX_MAX)) + return; + + kvm_for_each_pmc(pmu, pmc, i, bitmap) { if (!pmc_event_is_allowed(pmc)) continue; -- 2.30.2