On 2025-05-21 3:55 p.m., Namhyung Kim wrote:
On Mon, Mar 24, 2025 at 05:30:45PM +0000, Mingwei Zhang wrote:
From: Kan Liang kan.liang@linux.intel.com
Only KVM knows the exact time when a guest is entering/exiting. Expose two interfaces to KVM to switch the ownership of the PMU resources.
All the pinned events must be scheduled in first. Extend the perf_event_sched_in() helper to support extra flag, e.g., EVENT_GUEST.
Signed-off-by: Kan Liang kan.liang@linux.intel.com Signed-off-by: Mingwei Zhang mizhang@google.com
include/linux/perf_event.h | 4 ++ kernel/events/core.c | 80 ++++++++++++++++++++++++++++++++++---- 2 files changed, 77 insertions(+), 7 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 7bda1e20be12..37187ee8e226 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1822,6 +1822,8 @@ extern int perf_event_period(struct perf_event *event, u64 value); extern u64 perf_event_pause(struct perf_event *event, bool reset); int perf_get_mediated_pmu(void); void perf_put_mediated_pmu(void); +void perf_guest_enter(void); +void perf_guest_exit(void); #else /* !CONFIG_PERF_EVENTS: */ static inline void * perf_aux_output_begin(struct perf_output_handle *handle, @@ -1919,6 +1921,8 @@ static inline int perf_get_mediated_pmu(void) } static inline void perf_put_mediated_pmu(void) { } +static inline void perf_guest_enter(void) { } +static inline void perf_guest_exit(void) { } #endif #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL) diff --git a/kernel/events/core.c b/kernel/events/core.c index 7a2115b2c5c1..d05487d465c9 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2827,14 +2827,15 @@ static void task_ctx_sched_out(struct perf_event_context *ctx, static void perf_event_sched_in(struct perf_cpu_context *cpuctx, struct perf_event_context *ctx,
struct pmu *pmu)
struct pmu *pmu,enum event_type_t event_type){
- ctx_sched_in(&cpuctx->ctx, pmu, EVENT_PINNED);
- ctx_sched_in(&cpuctx->ctx, pmu, EVENT_PINNED | event_type); if (ctx)
ctx_sched_in(ctx, pmu, EVENT_PINNED);- ctx_sched_in(&cpuctx->ctx, pmu, EVENT_FLEXIBLE);
ctx_sched_in(ctx, pmu, EVENT_PINNED | event_type);- ctx_sched_in(&cpuctx->ctx, pmu, EVENT_FLEXIBLE | event_type); if (ctx)
ctx_sched_in(ctx, pmu, EVENT_FLEXIBLE);
ctx_sched_in(ctx, pmu, EVENT_FLEXIBLE | event_type);} /* @@ -2890,7 +2891,7 @@ static void ctx_resched(struct perf_cpu_context *cpuctx, else if (event_type & EVENT_PINNED) ctx_sched_out(&cpuctx->ctx, pmu, EVENT_FLEXIBLE);
- perf_event_sched_in(cpuctx, task_ctx, pmu);
- perf_event_sched_in(cpuctx, task_ctx, pmu, 0);
for_each_epc(epc, &cpuctx->ctx, pmu, 0) perf_pmu_enable(epc->pmu); @@ -4188,7 +4189,7 @@ static void perf_event_context_sched_in(struct task_struct *task) ctx_sched_out(&cpuctx->ctx, NULL, EVENT_FLEXIBLE); }
- perf_event_sched_in(cpuctx, ctx, NULL);
- perf_event_sched_in(cpuctx, ctx, NULL, 0);
perf_ctx_sched_task_cb(cpuctx->task_ctx, true); @@ -6040,6 +6041,71 @@ void perf_put_mediated_pmu(void) } EXPORT_SYMBOL_GPL(perf_put_mediated_pmu); +static inline void perf_host_exit(struct perf_cpu_context *cpuctx) +{
- perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST);
- ctx_sched_out(&cpuctx->ctx, NULL, EVENT_GUEST);
- perf_ctx_enable(&cpuctx->ctx, 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->task_ctx, EVENT_GUEST);- }
+}
Cpu context and task context may have events in the same PMU. How about this?
perf_ctx_disable(&cpuctx->ctx, EVENT_GUEST); if (cpuctx->task_ctx) perf_ctx_disable(cpuctx->task_ctx, EVENT_GUEST);
ctx_sched_out(&cpuctx->ctx, NULL, EVENT_GUEST); if (cpuctx->task_ctx) task_ctx_sched_out(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);
Yes, this is what has to be fixed in V4.
No matter for load context or put context, I think the below steps have to be followed. - Disable both cpuctx->ctx and cpuctx->task_ctx - schedule in/out host counters and load/put guest countext - Enable both cpuctx->ctx and cpuctx->task_ctx
A similar proposed can be found at https://lore.kernel.org/lkml/4aaf67ab-aa5c-41e6-bced-3cb000172c52@linux.inte...
Thanks, Kan