From 73554b29bd70546c1a9efc9c160641ef1b849358 Mon Sep 17 00:00:00 2001 From: Jim Mattson Date: Mon, 25 Sep 2023 17:34:46 +0000 Subject: KVM: x86/pmu: Synthesize at most one PMI per VM-exit When the irq_work callback, kvm_pmi_trigger_fn(), is invoked during a VM-exit that also invokes __kvm_perf_overflow() as a result of instruction emulation, kvm_pmu_deliver_pmi() will be called twice before the next VM-entry. Calling kvm_pmu_deliver_pmi() twice is unlikely to be problematic now that KVM sets the LVTPC mask bit when delivering a PMI. But using IRQ work to trigger the PMI is still broken, albeit very theoretically. E.g. if the self-IPI to trigger IRQ work is be delayed long enough for the vCPU to be migrated to a different pCPU, then it's possible for kvm_pmi_trigger_fn() to race with the kvm_pmu_deliver_pmi() from KVM_REQ_PMI and still generate two PMIs. KVM could set the mask bit using an atomic operation, but that'd just be piling on unnecessary code to workaround what is effectively a hack. The *only* reason KVM uses IRQ work is to ensure the PMI is treated as a wake event, e.g. if the vCPU just executed HLT. Remove the irq_work callback for synthesizing a PMI, and all of the logic for invoking it. Instead, to prevent a vcpu from leaving C0 with a PMI pending, add a check for KVM_REQ_PMI to kvm_vcpu_has_events(). Fixes: 9cd803d496e7 ("KVM: x86: Update vPMCs when retiring instructions") Signed-off-by: Jim Mattson Tested-by: Mingwei Zhang Tested-by: Dapeng Mi Signed-off-by: Mingwei Zhang Link: https://lore.kernel.org/r/20230925173448.3518223-2-mizhang@google.com [sean: massage changelog] Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_host.h | 1 - arch/x86/kvm/pmu.c | 27 +-------------------------- arch/x86/kvm/x86.c | 3 +++ 3 files changed, 4 insertions(+), 27 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 17715cb8731d..70d139406bc8 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -528,7 +528,6 @@ struct kvm_pmu { u64 raw_event_mask; struct kvm_pmc gp_counters[KVM_INTEL_PMC_MAX_GENERIC]; struct kvm_pmc fixed_counters[KVM_PMC_MAX_FIXED]; - struct irq_work irq_work; /* * Overlay the bitmap with a 64-bit atomic so that all bits can be diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index edb89b51b383..9ae07db6f0f6 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -93,14 +93,6 @@ void kvm_pmu_ops_update(const struct kvm_pmu_ops *pmu_ops) #undef __KVM_X86_PMU_OP } -static void kvm_pmi_trigger_fn(struct irq_work *irq_work) -{ - struct kvm_pmu *pmu = container_of(irq_work, struct kvm_pmu, irq_work); - struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu); - - kvm_pmu_deliver_pmi(vcpu); -} - static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi) { struct kvm_pmu *pmu = pmc_to_pmu(pmc); @@ -124,20 +116,7 @@ static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi) __set_bit(pmc->idx, (unsigned long *)&pmu->global_status); } - if (!pmc->intr || 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 - * 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_handling_nmi_from_guest(pmc->vcpu)) - irq_work_queue(&pmc_to_pmu(pmc)->irq_work); - else + if (pmc->intr && !skip_pmi) kvm_make_request(KVM_REQ_PMI, pmc->vcpu); } @@ -675,9 +654,6 @@ void kvm_pmu_refresh(struct kvm_vcpu *vcpu) void kvm_pmu_reset(struct kvm_vcpu *vcpu) { - struct kvm_pmu *pmu = vcpu_to_pmu(vcpu); - - irq_work_sync(&pmu->irq_work); static_call(kvm_x86_pmu_reset)(vcpu); } @@ -687,7 +663,6 @@ void kvm_pmu_init(struct kvm_vcpu *vcpu) memset(pmu, 0, sizeof(*pmu)); static_call(kvm_x86_pmu_init)(vcpu); - init_irq_work(&pmu->irq_work, kvm_pmi_trigger_fn); pmu->event_count = 0; pmu->need_cleanup = false; kvm_pmu_refresh(vcpu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9f18b06bbda6..42a4e8f5e89a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12843,6 +12843,9 @@ static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu) return true; #endif + if (kvm_test_request(KVM_REQ_PMI, vcpu)) + return true; + if (kvm_arch_interrupt_allowed(vcpu) && (kvm_cpu_has_interrupt(vcpu) || kvm_guest_apic_has_interrupt(vcpu))) -- cgit