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
the pmc->intr can be stored into pmc from pmc_reprogram_counter()
which provides smaller instructions footprint against the
u-architecture branch predictor.
The __kvm_perf_overflow() can be called in non-nmi contexts
and a flag is needed to distinguish the caller context and thus
avoid a check on kvm_is_in_guest(), otherwise we might get
warnings from suspicious RCU or check_preemption_disabled().
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/pmu.c | 58 ++++++++++++++++-----------------
2 files changed, 29 insertions(+), 30 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index e41ad1ead721..6c2b2331ffeb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -495,6 +495,7 @@ struct kvm_pmc {
*/
u64 current_config;
bool is_paused;
+ bool intr;
};
struct kvm_pmu {
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index b7a1ae28ab87..a20207ee4014 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -55,43 +55,41 @@ 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 void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi)
{
- 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);
- }
+ /* Ignore counters that have been reprogrammed already. */
+ if (test_and_set_bit(pmc->idx, pmu->reprogram_pmi))
+ return;
+
+ __set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
+ kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
+
+ if (!pmc->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 (in_pmi && !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_intr(struct perf_event *perf_event,
- struct perf_sample_data *data,
- struct pt_regs *regs)
+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)) {
- __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);
- }
+ __kvm_perf_overflow(pmc, true);
}
static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
@@ -126,7 +124,6 @@ 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",
@@ -138,6 +135,7 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
pmc_to_pmu(pmc)->event_count++;
clear_bit(pmc->idx, pmc_to_pmu(pmc)->reprogram_pmi);
pmc->is_paused = false;
+ pmc->intr = intr;
}
static void pmc_pause_counter(struct kvm_pmc *pmc)
--
2.33.1
