[PATCH v4 03/12] KVM: x86/pmu: Rewrite reprogram_counters() to improve performance

Like Xu
2023-02-14T05:08:36Z

From: Like Xu <likexu@tencent.com>

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>
---
arch/x86/kvm/vmx/pmu_intel.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 6a2f8b4ed061..069e1aae418c 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -73,16 +73,16 @@ 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)
+static inline 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)
--
2.39.1