Messages in this thread | | | Subject | Re: [PATCH v5 06/16] KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter | From | "Xu, Like" <> | Date | Mon, 19 Apr 2021 16:17:54 +0800 |
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On 2021/4/19 16:11, Liuxiangdong wrote: > > > On 2021/4/15 11:20, Like Xu wrote: >> When a guest counter is configured as a PEBS counter through >> IA32_PEBS_ENABLE, a guest PEBS event will be reprogrammed by >> configuring a non-zero precision level in the perf_event_attr. >> >> The guest PEBS overflow PMI bit would be set in the guest >> GLOBAL_STATUS MSR when PEBS facility generates a PEBS >> overflow PMI based on guest IA32_DS_AREA MSR. >> >> Even with the same counter index and the same event code and >> mask, guest PEBS events will not be reused for non-PEBS events. >> >> Originally-by: Andi Kleen <ak@linux.intel.com> >> Co-developed-by: Kan Liang <kan.liang@linux.intel.com> >> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> >> Signed-off-by: Like Xu <like.xu@linux.intel.com> >> --- >> arch/x86/kvm/pmu.c | 34 ++++++++++++++++++++++++++++++++-- >> 1 file changed, 32 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c >> index 827886c12c16..0f86c1142f17 100644 >> --- a/arch/x86/kvm/pmu.c >> +++ b/arch/x86/kvm/pmu.c >> @@ -74,11 +74,21 @@ static void kvm_perf_overflow_intr(struct perf_event >> *perf_event, >> { >> struct kvm_pmc *pmc = perf_event->overflow_handler_context; >> struct kvm_pmu *pmu = pmc_to_pmu(pmc); >> + bool skip_pmi = false; >> if (!test_and_set_bit(pmc->idx, pmu->reprogram_pmi)) { >> - __set_bit(pmc->idx, (unsigned long *)&pmu->global_status); >> + if (perf_event->attr.precise_ip) { >> + /* Indicate PEBS overflow PMI to guest. */ >> + skip_pmi = __test_and_set_bit(GLOBAL_STATUS_BUFFER_OVF_BIT, >> + (unsigned long *)&pmu->global_status); >> + } else { >> + __set_bit(pmc->idx, (unsigned long *)&pmu->global_status); >> + } >> kvm_make_request(KVM_REQ_PMU, pmc->vcpu); >> + if (skip_pmi) >> + 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 >> @@ -99,6 +109,7 @@ static void pmc_reprogram_counter(struct kvm_pmc >> *pmc, u32 type, >> bool exclude_kernel, bool intr, >> bool in_tx, bool in_tx_cp) >> { >> + struct kvm_pmu *pmu = vcpu_to_pmu(pmc->vcpu); >> struct perf_event *event; >> struct perf_event_attr attr = { >> .type = type, >> @@ -110,6 +121,7 @@ static void pmc_reprogram_counter(struct kvm_pmc >> *pmc, u32 type, >> .exclude_kernel = exclude_kernel, >> .config = config, >> }; >> + bool pebs = test_bit(pmc->idx, (unsigned long *)&pmu->pebs_enable); > > pebs_enable is defined in patch 07, but used here(in patch 06). > Maybe we can change the patches order in next patch version if necessary.
Thanks! I'll fix it.
> >> attr.sample_period = get_sample_period(pmc, pmc->counter); >> @@ -124,9 +136,23 @@ static void pmc_reprogram_counter(struct kvm_pmc >> *pmc, u32 type, >> attr.sample_period = 0; >> attr.config |= HSW_IN_TX_CHECKPOINTED; >> } >> + if (pebs) { >> + /* >> + * The non-zero precision level of guest event makes the ordinary >> + * guest event becomes a guest PEBS event and triggers the host >> + * PEBS PMI handler to determine whether the PEBS overflow PMI >> + * comes from the host counters or the guest. >> + * >> + * For most PEBS hardware events, the difference in the software >> + * precision levels of guest and host PEBS events will not affect >> + * the accuracy of the PEBS profiling result, because the >> "event IP" >> + * in the PEBS record is calibrated on the guest side. >> + */ >> + attr.precise_ip = 1; >> + } >> event = perf_event_create_kernel_counter(&attr, -1, current, >> - intr ? kvm_perf_overflow_intr : >> + (intr || pebs) ? 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", >> @@ -161,6 +187,10 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc) >> get_sample_period(pmc, pmc->counter))) >> return false; >> + if (!test_bit(pmc->idx, (unsigned long >> *)&pmc_to_pmu(pmc)->pebs_enable) && >> + pmc->perf_event->attr.precise_ip) >> + return false; >> + >> /* reuse perf_event to serve as pmc_reprogram_counter() does*/ >> perf_event_enable(pmc->perf_event); >
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