From: Like Xu <likexu@xxxxxxxxxxx>
Depending on whether intr should be triggered or not, KVM registers
two different event overflow callbacks in the perf_event context.
The code skeleton of these two functions is very similar, so
need_overflow_intr() is introduced to increase the potential code reuse.
There is a trade-off between extra cycles in the irq context and a
smaller instructions footprint against the u-architecture branch predictor.
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
arch/x86/kvm/pmu.c | 64 +++++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 29 deletions(-)
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 3c45467b4275..ef4bba8be7f7 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -55,43 +55,50 @@ static void kvm_pmi_trigger_fn(struct irq_work *irq_work)
kvm_pmu_deliver_pmi(vcpu);
}
-static void kvm_perf_overflow(struct perf_event *perf_event,
- struct perf_sample_data *data,
- struct pt_regs *regs)
+static inline bool need_overflow_intr(struct kvm_pmc *pmc)
{
- struct kvm_pmc *pmc = perf_event->overflow_handler_context;
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
- if (!test_and_set_bit(pmc->idx, pmu->reprogram_pmi)) {
- __set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
- kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
- }
+ if (pmc_is_gp(pmc))
+ return (pmc->eventsel & ARCH_PERFMON_EVENTSEL_INT);
+ else
+ return fixed_ctrl_field(pmu->fixed_ctr_ctrl,
+ pmc->idx - INTEL_PMC_IDX_FIXED) & 0x8;
}
-static void kvm_perf_overflow_intr(struct perf_event *perf_event,
- struct perf_sample_data *data,
- struct pt_regs *regs)
+static inline void kvm_pmu_counter_overflow(struct kvm_pmc *pmc, bool intr)
{
- struct kvm_pmc *pmc = perf_event->overflow_handler_context;
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
- if (!test_and_set_bit(pmc->idx, pmu->reprogram_pmi)) {
- __set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
- kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
+ __set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
+ kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
- /*
- * Inject PMI. If vcpu was in a guest mode during NMI PMI
- * can be ejected on a guest mode re-entry. Otherwise we can't
- * be sure that vcpu wasn't executing hlt instruction at the
- * time of vmexit and is not going to re-enter guest mode until
- * woken up. So we should wake it, but this is impossible from
- * NMI context. Do it from irq work instead.
- */
- if (!kvm_is_in_guest())
- irq_work_queue(&pmc_to_pmu(pmc)->irq_work);
- else
- kvm_make_request(KVM_REQ_PMI, pmc->vcpu);
- }
+ if (!intr)
+ return;
+
+ /*
+ * Inject PMI. If vcpu was in a guest mode during NMI PMI
+ * can be ejected on a guest mode re-entry. Otherwise we can't
+ * be sure that vcpu wasn't executing hlt instruction at the
+ * time of vmexit and is not going to re-enter guest mode until
+ * woken up. So we should wake it, but this is impossible from
+ * NMI context. Do it from irq work instead.
+ */
+ if (!kvm_is_in_guest())
+ irq_work_queue(&pmc_to_pmu(pmc)->irq_work);
+ else
+ kvm_make_request(KVM_REQ_PMI, pmc->vcpu);
+}
+
+static void kvm_perf_overflow(struct perf_event *perf_event,
+ struct perf_sample_data *data,
+ struct pt_regs *regs)
+{
+ struct kvm_pmc *pmc = perf_event->overflow_handler_context;
+ struct kvm_pmu *pmu = pmc_to_pmu(pmc);
+
+ if (!test_and_set_bit(pmc->idx, pmu->reprogram_pmi))
+ kvm_pmu_counter_overflow(pmc, need_overflow_intr(pmc));
}
static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
@@ -126,7 +133,6 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
}
event = perf_event_create_kernel_counter(&attr, -1, current,
- intr ? kvm_perf_overflow_intr :
kvm_perf_overflow, pmc);
if (IS_ERR(event)) {
pr_debug_ratelimited("kvm_pmu: event creation failed %ld for pmc->idx = %d\n",
--
2.33.1
