From cf52de619c67bd1f6b1cf2751c3827815f74a5a5 Mon Sep 17 00:00:00 2001 From: Like Xu Date: Wed, 31 Aug 2022 16:53:24 +0800 Subject: [PATCH] KVM: x86/pmu: Avoid using PEBS perf_events for normal counters The check logic in the pmc_resume_counter() to determine whether a perf_event is reusable is partial and flawed, especially when it comes to a pseudocode sequence (contrived, but valid) like: - enabling a counter and its PEBS bit - enable global_ctrl - run workload - disable only the PEBS bit, leaving the global_ctrl bit enabled In this corner case, a perf_event created for PEBS can be reused by a normal counter before it has been released and recreated, and when this normal counter overflows, it triggers a PEBS interrupt (precise_ip != 0). To address this issue, reprogram all affected counters when PEBS_ENABLE change and reuse a counter if and only if PEBS exactly matches precise. Fixes: 79f3e3b58386 ("KVM: x86/pmu: Reprogram PEBS event to emulate guest PEBS counter") Signed-off-by: Like Xu Link: https://lore.kernel.org/r/20220831085328.45489-4-likexu@tencent.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/pmu.c | 4 ++-- arch/x86/kvm/vmx/pmu_intel.c | 2 ++ 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index 390d697efde14..d9b9a0f0db17c 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -237,8 +237,8 @@ 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) + 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*/ diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index 5592b1259e1bb..25b70a85bef54 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -431,7 +431,9 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) if (pmu->pebs_enable == data) return 0; if (!(data & pmu->pebs_enable_mask)) { + diff = pmu->pebs_enable ^ data; pmu->pebs_enable = data; + reprogram_counters(pmu, diff); return 0; } break;