From 42457a7fb6cacca83be4deaf202ac3e45830daf2 Mon Sep 17 00:00:00 2001 From: Kan Liang Date: Fri, 5 Dec 2025 16:16:43 -0800 Subject: [PATCH] perf: Add APIs to load/put guest mediated PMU context Add exported APIs to load/put a guest mediated PMU context. KVM will load the guest PMU shortly before VM-Enter, and put the guest PMU shortly after VM-Exit. On the perf side of things, schedule out all exclude_guest events when the guest context is loaded, and schedule them back in when the guest context is put. I.e. yield the hardware PMU resources to the guest, by way of KVM. Note, perf is only responsible for managing host context. KVM is responsible for loading/storing guest state to/from hardware. [sean: shuffle patches around, write changelog] Suggested-by: Sean Christopherson Signed-off-by: Kan Liang Signed-off-by: Mingwei Zhang Signed-off-by: Sean Christopherson Signed-off-by: Peter Zijlstra (Intel) Tested-by: Xudong Hao Link: https://patch.msgid.link/20251206001720.468579-8-seanjc@google.com --- include/linux/perf_event.h | 2 ++ kernel/events/core.c | 61 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 63 insertions(+) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d9988e3fd5571..322cfa9f3d481 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1925,6 +1925,8 @@ extern u64 perf_event_pause(struct perf_event *event, bool reset); #ifdef CONFIG_PERF_GUEST_MEDIATED_PMU int perf_create_mediated_pmu(void); void perf_release_mediated_pmu(void); +void perf_load_guest_context(void); +void perf_put_guest_context(void); #endif #else /* !CONFIG_PERF_EVENTS: */ diff --git a/kernel/events/core.c b/kernel/events/core.c index 6781d39f31587..bbb81a4a31965 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -470,10 +470,19 @@ static cpumask_var_t perf_online_pkg_mask; static cpumask_var_t perf_online_sys_mask; static struct kmem_cache *perf_event_cache; +#ifdef CONFIG_PERF_GUEST_MEDIATED_PMU +static DEFINE_PER_CPU(bool, guest_ctx_loaded); + +static __always_inline bool is_guest_mediated_pmu_loaded(void) +{ + return __this_cpu_read(guest_ctx_loaded); +} +#else static __always_inline bool is_guest_mediated_pmu_loaded(void) { return false; } +#endif /* * perf event paranoia level: @@ -6384,6 +6393,58 @@ void perf_release_mediated_pmu(void) atomic_dec(&nr_mediated_pmu_vms); } EXPORT_SYMBOL_GPL(perf_release_mediated_pmu); + +/* When loading a guest's mediated PMU, schedule out all exclude_guest events. */ +void perf_load_guest_context(void) +{ + struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context); + + lockdep_assert_irqs_disabled(); + + guard(perf_ctx_lock)(cpuctx, cpuctx->task_ctx); + + if (WARN_ON_ONCE(__this_cpu_read(guest_ctx_loaded))) + return; + + perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST); + ctx_sched_out(&cpuctx->ctx, NULL, EVENT_GUEST); + if (cpuctx->task_ctx) { + perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST); + task_ctx_sched_out(cpuctx->task_ctx, NULL, EVENT_GUEST); + } + + perf_ctx_enable(&cpuctx->ctx, EVENT_GUEST); + if (cpuctx->task_ctx) + perf_ctx_enable(cpuctx->task_ctx, EVENT_GUEST); + + __this_cpu_write(guest_ctx_loaded, true); +} +EXPORT_SYMBOL_GPL(perf_load_guest_context); + +void perf_put_guest_context(void) +{ + struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context); + + lockdep_assert_irqs_disabled(); + + guard(perf_ctx_lock)(cpuctx, cpuctx->task_ctx); + + if (WARN_ON_ONCE(!__this_cpu_read(guest_ctx_loaded))) + return; + + perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST); + if (cpuctx->task_ctx) + perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST); + + perf_event_sched_in(cpuctx, cpuctx->task_ctx, NULL, EVENT_GUEST); + + if (cpuctx->task_ctx) + perf_ctx_enable(cpuctx->task_ctx, EVENT_GUEST); + perf_ctx_enable(&cpuctx->ctx, EVENT_GUEST); + + __this_cpu_write(guest_ctx_loaded, false); +} +EXPORT_SYMBOL_GPL(perf_put_guest_context); #else static int mediated_pmu_account_event(struct perf_event *event) { return 0; } static void mediated_pmu_unaccount_event(struct perf_event *event) {} -- 2.47.3