KVM: x86/pmu: Rewrite reprogram_counters() to improve performance

A valid pmc is always tested before using pmu->reprogram_pmi. Eliminate
this part of the redundancy by setting the counter's bitmask directly,
and in addition, trigger KVM_REQ_PMU only once to save more cpu cycles.

Signed-off-by: Like Xu <likexu@tencent.com>
Link: https://lore.kernel.org/r/20230214050757.9623-4-likexu@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index c45bd10f80a1eadb40d411bea5b27b398b45f0d3..eb291dfbe4aa393b56c35e7f91b0802a14870a0f 100644 (file)
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -76,13 +76,13 @@ static struct kvm_pmc *intel_pmc_idx_to_pmc(struct kvm_pmu *pmu, int pmc_idx)
 static void reprogram_counters(struct kvm_pmu *pmu, u64 diff)
 {
        int bit;
-       struct kvm_pmc *pmc;
 
-       for_each_set_bit(bit, (unsigned long *)&diff, X86_PMC_IDX_MAX) {
-               pmc = intel_pmc_idx_to_pmc(pmu, bit);
-               if (pmc)
-                       kvm_pmu_request_counter_reprogam(pmc);
-       }
+       if (!diff)
+               return;
+
+       for_each_set_bit(bit, (unsigned long *)&diff, X86_PMC_IDX_MAX)
+               set_bit(bit, pmu->reprogram_pmi);
+       kvm_make_request(KVM_REQ_PMU, pmu_to_vcpu(pmu));
 }
 
 static bool intel_hw_event_available(struct kvm_pmc *pmc)