Messages in this thread | | | Subject | Re: [PATCH v5 06/16] KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter | From | Liuxiangdong <> | Date | Mon, 19 Apr 2021 16:11:18 +0800 |
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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.
> 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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