From: Xiong Zhang Date: Sat, 6 Dec 2025 00:16:55 +0000 (-0800) Subject: KVM: x86/pmu: Register PMI handler for mediated vPMU X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1c4ba7286afba9842f295fc7a3dbe74acc6a92af;p=thirdparty%2Flinux.git KVM: x86/pmu: Register PMI handler for mediated vPMU Register a dedicated PMI handler with perf's callback when mediated PMU support is enabled. Perf routes PMIs that arrive while guest context is loaded to the provided callback, by modifying the CPU's LVTPC to point at a dedicated mediated PMI IRQ vector. WARN upon receipt of a mediated PMI if there is no active vCPU, or if the vCPU doesn't have a mediated PMU. Even if a PMI manages to skid past VM-Exit, it should never be delayed all the way beyond unloading the vCPU. And while running vCPUs without a mediated PMU, the LVTPC should never be wired up to the mediated PMI IRQ vector, i.e. should always be routed through perf's NMI handler. Signed-off-by: Xiong Zhang Signed-off-by: Mingwei Zhang Tested-by: Xudong Hao Co-developed-by: Sean Christopherson Tested-by: Manali Shukla Link: https://patch.msgid.link/20251206001720.468579-20-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c index 131e24246b09e..0b67920fa0697 100644 --- a/arch/x86/kvm/pmu.c +++ b/arch/x86/kvm/pmu.c @@ -157,6 +157,16 @@ void kvm_init_pmu_capability(const struct kvm_pmu_ops *pmu_ops) perf_get_hw_event_config(PERF_COUNT_HW_BRANCH_INSTRUCTIONS); } +void kvm_handle_guest_mediated_pmi(void) +{ + struct kvm_vcpu *vcpu = kvm_get_running_vcpu(); + + if (WARN_ON_ONCE(!vcpu || !kvm_vcpu_has_mediated_pmu(vcpu))) + return; + + kvm_make_request(KVM_REQ_PMI, vcpu); +} + static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi) { struct kvm_pmu *pmu = pmc_to_pmu(pmc); diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h index a5c7c026b919a..9849c2bb720df 100644 --- a/arch/x86/kvm/pmu.h +++ b/arch/x86/kvm/pmu.h @@ -46,6 +46,8 @@ struct kvm_pmu_ops { void kvm_pmu_ops_update(const struct kvm_pmu_ops *pmu_ops); +void kvm_handle_guest_mediated_pmi(void); + static inline bool kvm_pmu_has_perf_global_ctrl(struct kvm_pmu *pmu) { /* diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index fb3a5e8615538..1623afddff3b6 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10111,7 +10111,8 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) set_hv_tscchange_cb(kvm_hyperv_tsc_notifier); #endif - __kvm_register_perf_callbacks(ops->handle_intel_pt_intr, NULL); + __kvm_register_perf_callbacks(ops->handle_intel_pt_intr, + enable_mediated_pmu ? kvm_handle_guest_mediated_pmi : NULL); if (IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) && tdp_mmu_enabled) kvm_caps.supported_vm_types |= BIT(KVM_X86_SW_PROTECTED_VM);