From: Sean Christopherson Date: Sat, 6 Dec 2025 00:16:44 +0000 (-0800) Subject: perf/x86/core: Register a new vector for handling mediated guest PMIs X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a05385d84b2af64600fc84b027bea481e8f6261d;p=thirdparty%2Fkernel%2Flinux.git perf/x86/core: Register a new vector for handling mediated guest PMIs Wire up system vector 0xf5 for handling PMIs (i.e. interrupts delivered through the LVTPC) while running KVM guests with a mediated PMU. Perf currently delivers all PMIs as NMIs, e.g. so that events that trigger while IRQs are disabled aren't delayed and generate useless records, but due to the multiplexing of NMIs throughout the system, correctly identifying NMIs for a mediated PMU is practically infeasible. To (greatly) simplify identifying guest mediated PMU PMIs, perf will switch the CPU's LVTPC between PERF_GUEST_MEDIATED_PMI_VECTOR and NMI when guest PMU context is loaded/put. I.e. PMIs that are generated by the CPU while the guest is active will be identified purely based on the IRQ vector. Route the vector through perf, e.g. as opposed to letting KVM attach a handler directly a la posted interrupt notification vectors, as perf owns the LVTPC and thus is the rightful owner of PERF_GUEST_MEDIATED_PMI_VECTOR. Functionally, having KVM directly own the vector would be fine (both KVM and perf will be completely aware of when a mediated PMU is active), but would lead to an undesirable split in ownership: perf would be responsible for installing the vector, but not handling the resulting IRQs. Add a new perf_guest_info_callbacks hook (and static call) to allow KVM to register its handler with perf when running guests with mediated PMUs. Note, because KVM always runs guests with host IRQs enabled, there is no danger of a PMI being delayed from the guest's perspective due to using a regular IRQ instead of an NMI. Signed-off-by: Sean Christopherson Signed-off-by: Peter Zijlstra (Intel) Tested-by: Xudong Hao Link: https://patch.msgid.link/20251206001720.468579-9-seanjc@google.com --- diff --git a/arch/x86/entry/entry_fred.c b/arch/x86/entry/entry_fred.c index 94e626cc6a074..a9b72997103d2 100644 --- a/arch/x86/entry/entry_fred.c +++ b/arch/x86/entry/entry_fred.c @@ -114,6 +114,7 @@ static idtentry_t sysvec_table[NR_SYSTEM_VECTORS] __ro_after_init = { SYSVEC(IRQ_WORK_VECTOR, irq_work), + SYSVEC(PERF_GUEST_MEDIATED_PMI_VECTOR, perf_guest_mediated_pmi_handler), SYSVEC(POSTED_INTR_VECTOR, kvm_posted_intr_ipi), SYSVEC(POSTED_INTR_WAKEUP_VECTOR, kvm_posted_intr_wakeup_ipi), SYSVEC(POSTED_INTR_NESTED_VECTOR, kvm_posted_intr_nested_ipi), diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h index 6b6d472baa0bb..9314642ae93cf 100644 --- a/arch/x86/include/asm/hardirq.h +++ b/arch/x86/include/asm/hardirq.h @@ -18,6 +18,9 @@ typedef struct { unsigned int kvm_posted_intr_ipis; unsigned int kvm_posted_intr_wakeup_ipis; unsigned int kvm_posted_intr_nested_ipis; +#endif +#ifdef CONFIG_GUEST_PERF_EVENTS + unsigned int perf_guest_mediated_pmis; #endif unsigned int x86_platform_ipis; /* arch dependent */ unsigned int apic_perf_irqs; diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index 3218770670d38..42bf6a58ec368 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -746,6 +746,12 @@ DECLARE_IDTENTRY_SYSVEC(POSTED_INTR_NESTED_VECTOR, sysvec_kvm_posted_intr_nested # define fred_sysvec_kvm_posted_intr_nested_ipi NULL #endif +# ifdef CONFIG_GUEST_PERF_EVENTS +DECLARE_IDTENTRY_SYSVEC(PERF_GUEST_MEDIATED_PMI_VECTOR, sysvec_perf_guest_mediated_pmi_handler); +#else +# define fred_sysvec_perf_guest_mediated_pmi_handler NULL +#endif + # ifdef CONFIG_X86_POSTED_MSI DECLARE_IDTENTRY_SYSVEC(POSTED_MSI_NOTIFICATION_VECTOR, sysvec_posted_msi_notification); #else diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h index 47051871b4361..85253fc8e3845 100644 --- a/arch/x86/include/asm/irq_vectors.h +++ b/arch/x86/include/asm/irq_vectors.h @@ -77,7 +77,9 @@ */ #define IRQ_WORK_VECTOR 0xf6 -/* 0xf5 - unused, was UV_BAU_MESSAGE */ +/* IRQ vector for PMIs when running a guest with a mediated PMU. */ +#define PERF_GUEST_MEDIATED_PMI_VECTOR 0xf5 + #define DEFERRED_ERROR_VECTOR 0xf4 /* Vector on which hypervisor callbacks will be delivered */ diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c index f445bec516a0b..2604565887564 100644 --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -158,6 +158,9 @@ static const __initconst struct idt_data apic_idts[] = { INTG(POSTED_INTR_WAKEUP_VECTOR, asm_sysvec_kvm_posted_intr_wakeup_ipi), INTG(POSTED_INTR_NESTED_VECTOR, asm_sysvec_kvm_posted_intr_nested_ipi), # endif +#ifdef CONFIG_GUEST_PERF_EVENTS + INTG(PERF_GUEST_MEDIATED_PMI_VECTOR, asm_sysvec_perf_guest_mediated_pmi_handler), +#endif # ifdef CONFIG_IRQ_WORK INTG(IRQ_WORK_VECTOR, asm_sysvec_irq_work), # endif diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 86f4e574de026..d56185b49a0e9 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -192,6 +192,13 @@ int arch_show_interrupts(struct seq_file *p, int prec) irq_stats(j)->kvm_posted_intr_wakeup_ipis); seq_puts(p, " Posted-interrupt wakeup event\n"); #endif +#ifdef CONFIG_GUEST_PERF_EVENTS + seq_printf(p, "%*s: ", prec, "VPMI"); + for_each_online_cpu(j) + seq_printf(p, "%10u ", + irq_stats(j)->perf_guest_mediated_pmis); + seq_puts(p, " Perf Guest Mediated PMI\n"); +#endif #ifdef CONFIG_X86_POSTED_MSI seq_printf(p, "%*s: ", prec, "PMN"); for_each_online_cpu(j) @@ -349,6 +356,18 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_x86_platform_ipi) } #endif +#ifdef CONFIG_GUEST_PERF_EVENTS +/* + * Handler for PERF_GUEST_MEDIATED_PMI_VECTOR. + */ +DEFINE_IDTENTRY_SYSVEC(sysvec_perf_guest_mediated_pmi_handler) +{ + apic_eoi(); + inc_irq_stat(perf_guest_mediated_pmis); + perf_guest_handle_mediated_pmi(); +} +#endif + #if IS_ENABLED(CONFIG_KVM) static void dummy_handler(void) {} static void (*kvm_posted_intr_wakeup_handler)(void) = dummy_handler; diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 322cfa9f3d481..82e617fad1655 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1677,6 +1677,8 @@ struct perf_guest_info_callbacks { unsigned int (*state)(void); unsigned long (*get_ip)(void); unsigned int (*handle_intel_pt_intr)(void); + + void (*handle_mediated_pmi)(void); }; #ifdef CONFIG_GUEST_PERF_EVENTS @@ -1686,6 +1688,7 @@ extern struct perf_guest_info_callbacks __rcu *perf_guest_cbs; DECLARE_STATIC_CALL(__perf_guest_state, *perf_guest_cbs->state); DECLARE_STATIC_CALL(__perf_guest_get_ip, *perf_guest_cbs->get_ip); DECLARE_STATIC_CALL(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr); +DECLARE_STATIC_CALL(__perf_guest_handle_mediated_pmi, *perf_guest_cbs->handle_mediated_pmi); static inline unsigned int perf_guest_state(void) { @@ -1702,6 +1705,11 @@ static inline unsigned int perf_guest_handle_intel_pt_intr(void) return static_call(__perf_guest_handle_intel_pt_intr)(); } +static inline void perf_guest_handle_mediated_pmi(void) +{ + static_call(__perf_guest_handle_mediated_pmi)(); +} + extern void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs); extern void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs); diff --git a/kernel/events/core.c b/kernel/events/core.c index bbb81a4a31965..dd842a4ca7895 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7644,6 +7644,7 @@ struct perf_guest_info_callbacks __rcu *perf_guest_cbs; DEFINE_STATIC_CALL_RET0(__perf_guest_state, *perf_guest_cbs->state); DEFINE_STATIC_CALL_RET0(__perf_guest_get_ip, *perf_guest_cbs->get_ip); DEFINE_STATIC_CALL_RET0(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr); +DEFINE_STATIC_CALL_RET0(__perf_guest_handle_mediated_pmi, *perf_guest_cbs->handle_mediated_pmi); void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs) { @@ -7658,6 +7659,10 @@ void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs) if (cbs->handle_intel_pt_intr) static_call_update(__perf_guest_handle_intel_pt_intr, cbs->handle_intel_pt_intr); + + if (cbs->handle_mediated_pmi) + static_call_update(__perf_guest_handle_mediated_pmi, + cbs->handle_mediated_pmi); } EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks); @@ -7669,8 +7674,8 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs) rcu_assign_pointer(perf_guest_cbs, NULL); static_call_update(__perf_guest_state, (void *)&__static_call_return0); static_call_update(__perf_guest_get_ip, (void *)&__static_call_return0); - static_call_update(__perf_guest_handle_intel_pt_intr, - (void *)&__static_call_return0); + static_call_update(__perf_guest_handle_intel_pt_intr, (void *)&__static_call_return0); + static_call_update(__perf_guest_handle_mediated_pmi, (void *)&__static_call_return0); synchronize_rcu(); } EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks); diff --git a/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h b/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h index 47051871b4361..6e1d5b955aae4 100644 --- a/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h +++ b/tools/perf/trace/beauty/arch/x86/include/asm/irq_vectors.h @@ -77,7 +77,8 @@ */ #define IRQ_WORK_VECTOR 0xf6 -/* 0xf5 - unused, was UV_BAU_MESSAGE */ +#define PERF_GUEST_MEDIATED_PMI_VECTOR 0xf5 + #define DEFERRED_ERROR_VECTOR 0xf4 /* Vector on which hypervisor callbacks will be delivered */ diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 5fcd401a58973..21a0d226d63f8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -6467,11 +6467,14 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = { .state = kvm_guest_state, .get_ip = kvm_guest_get_ip, .handle_intel_pt_intr = NULL, + .handle_mediated_pmi = NULL, }; void kvm_register_perf_callbacks(unsigned int (*pt_intr_handler)(void)) { kvm_guest_cbs.handle_intel_pt_intr = pt_intr_handler; + kvm_guest_cbs.handle_mediated_pmi = NULL; + perf_register_guest_info_callbacks(&kvm_guest_cbs); } void kvm_unregister_perf_callbacks(void)