Hello,
On Mon, Mar 24, 2025 at 05:30:44PM +0000, Mingwei Zhang wrote:
> From: Kan Liang <kan.li...@linux.intel.com>
>
> Current perf doesn't explicitly schedule out all exclude_guest events
> while the guest is running. There is no problem with the current
> emulated vPMU. Because perf owns all the PMU counters. It can mask the
> counter which is assigned to an exclude_guest event when a guest is
> running (Intel way), or set the corresponding HOSTONLY bit in evsentsel
> (AMD way). The counter doesn't count when a guest is running.
>
> However, either way doesn't work with the introduced passthrough vPMU.
> A guest owns all the PMU counters when it's running. The host should not
> mask any counters. The counter may be used by the guest. The evsentsel
> may be overwritten.
>
> Perf should explicitly schedule out all exclude_guest events to release
> the PMU resources when entering a guest, and resume the counting when
> exiting the guest.
>
> It's possible that an exclude_guest event is created when a guest is
> running. The new event should not be scheduled in as well.
>
> The ctx time is shared among different PMUs. The time cannot be stopped
> when a guest is running. It is required to calculate the time for events
> from other PMUs, e.g., uncore events. Add timeguest to track the guest
> run time. For an exclude_guest event, the elapsed time equals
> the ctx time - guest time.
> Cgroup has dedicated times. Use the same method to deduct the guest time
> from the cgroup time as well.
>
> Co-developed-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
> Signed-off-by: Kan Liang <kan.li...@linux.intel.com>
> Signed-off-by: Mingwei Zhang <mizh...@google.com>
> ---
> include/linux/perf_event.h | 6 ++
> kernel/events/core.c | 209 +++++++++++++++++++++++++++++--------
> 2 files changed, 169 insertions(+), 46 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index a2fd1bdc955c..7bda1e20be12 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -999,6 +999,11 @@ struct perf_event_context {
> */
> struct perf_time_ctx time;
>
> + /*
> + * Context clock, runs when in the guest mode.
> + */
> + struct perf_time_ctx timeguest;
Why not make it an array as you use it later?
> +
> /*
> * These fields let us detect when two contexts have both
> * been cloned (inherited) from a common ancestor.
> @@ -1089,6 +1094,7 @@ struct bpf_perf_event_data_kern {
> */
> struct perf_cgroup_info {
> struct perf_time_ctx time;
> + struct perf_time_ctx timeguest;
> int active;
> };
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index e38c8b5e8086..7a2115b2c5c1 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -163,7 +163,8 @@ enum event_type_t {
> /* see ctx_resched() for details */
> EVENT_CPU = 0x10,
> EVENT_CGROUP = 0x20,
> - EVENT_FLAGS = EVENT_CGROUP,
> + EVENT_GUEST = 0x40,
It's not clear to me if this flag is for events to include guests or
exclude them. Can you please add a comment?
Thanks,
Namhyung
> + EVENT_FLAGS = EVENT_CGROUP | EVENT_GUEST,
> /* compound helpers */
> EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
> EVENT_TIME_FROZEN = EVENT_TIME | EVENT_FROZEN,
> @@ -435,6 +436,7 @@ static atomic_t nr_include_guest_events __read_mostly;
>
> static atomic_t nr_mediated_pmu_vms;
> static DEFINE_MUTEX(perf_mediated_pmu_mutex);
> +static DEFINE_PER_CPU(bool, perf_in_guest);
>
> /* !exclude_guest event of PMU with PERF_PMU_CAP_MEDIATED_VPMU */
> static inline bool is_include_guest_event(struct perf_event *event)
> @@ -738,6 +740,9 @@ static bool perf_skip_pmu_ctx(struct
> perf_event_pmu_context *pmu_ctx,
> {
> if ((event_type & EVENT_CGROUP) && !pmu_ctx->nr_cgroups)
> return true;
> + if ((event_type & EVENT_GUEST) &&
> + !(pmu_ctx->pmu->capabilities & PERF_PMU_CAP_MEDIATED_VPMU))
> + return true;
> return false;
> }
>
> @@ -788,6 +793,39 @@ static inline void update_perf_time_ctx(struct
> perf_time_ctx *time, u64 now, boo
> WRITE_ONCE(time->offset, time->time - time->stamp);
> }
>
> +static_assert(offsetof(struct perf_event_context, timeguest) -
> + offsetof(struct perf_event_context, time) ==
> + sizeof(struct perf_time_ctx));
> +
> +#define T_TOTAL 0
> +#define T_GUEST 1
> +
> +static inline u64 __perf_event_time_ctx(struct perf_event *event,
> + struct perf_time_ctx *times)
> +{
> + u64 time = times[T_TOTAL].time;
> +
> + if (event->attr.exclude_guest)
> + time -= times[T_GUEST].time;
> +
> + return time;
> +}
> +
> +static inline u64 __perf_event_time_ctx_now(struct perf_event *event,
> + struct perf_time_ctx *times,
> + u64 now)
> +{
> + if (event->attr.exclude_guest && __this_cpu_read(perf_in_guest)) {
> + /*
> + * (now + times[total].offset) - (now + times[guest].offset) :=
> + * times[total].offset - times[guest].offset
> + */
> + return READ_ONCE(times[T_TOTAL].offset) -
> READ_ONCE(times[T_GUEST].offset);
> + }
> +
> + return now + READ_ONCE(times[T_TOTAL].offset);
> +}
> +
> #ifdef CONFIG_CGROUP_PERF
>
> static inline bool
> @@ -824,12 +862,16 @@ static inline int is_cgroup_event(struct perf_event
> *event)
> return event->cgrp != NULL;
> }
>
> +static_assert(offsetof(struct perf_cgroup_info, timeguest) -
> + offsetof(struct perf_cgroup_info, time) ==
> + sizeof(struct perf_time_ctx));
> +
> static inline u64 perf_cgroup_event_time(struct perf_event *event)
> {
> struct perf_cgroup_info *t;
>
> t = per_cpu_ptr(event->cgrp->info, event->cpu);
> - return t->time.time;
> + return __perf_event_time_ctx(event, &t->time);
> }
>
> static inline u64 perf_cgroup_event_time_now(struct perf_event *event, u64
> now)
> @@ -838,9 +880,21 @@ static inline u64 perf_cgroup_event_time_now(struct
> perf_event *event, u64 now)
>
> t = per_cpu_ptr(event->cgrp->info, event->cpu);
> if (!__load_acquire(&t->active))
> - return t->time.time;
> - now += READ_ONCE(t->time.offset);
> - return now;
> + return __perf_event_time_ctx(event, &t->time);
> +
> + return __perf_event_time_ctx_now(event, &t->time, now);
> +}
> +
> +static inline void __update_cgrp_guest_time(struct perf_cgroup_info *info,
> u64 now, bool adv)
> +{
> + update_perf_time_ctx(&info->timeguest, now, adv);
> +}
> +
> +static inline void update_cgrp_time(struct perf_cgroup_info *info, u64 now)
> +{
> + update_perf_time_ctx(&info->time, now, true);
> + if (__this_cpu_read(perf_in_guest))
> + __update_cgrp_guest_time(info, now, true);
> }
>
> static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context
> *cpuctx, bool final)
> @@ -856,7 +910,7 @@ static inline void update_cgrp_time_from_cpuctx(struct
> perf_cpu_context *cpuctx,
> cgrp = container_of(css, struct perf_cgroup, css);
> info = this_cpu_ptr(cgrp->info);
>
> - update_perf_time_ctx(&info->time, now, true);
> + update_cgrp_time(info, now);
> if (final)
> __store_release(&info->active, 0);
> }
> @@ -879,11 +933,11 @@ static inline void update_cgrp_time_from_event(struct
> perf_event *event)
> * Do not update time when cgroup is not active
> */
> if (info->active)
> - update_perf_time_ctx(&info->time, perf_clock(), true);
> + update_cgrp_time(info, perf_clock());
> }
>
> static inline void
> -perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx)
> +perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx, bool guest)
> {
> struct perf_event_context *ctx = &cpuctx->ctx;
> struct perf_cgroup *cgrp = cpuctx->cgrp;
> @@ -903,8 +957,12 @@ perf_cgroup_set_timestamp(struct perf_cpu_context
> *cpuctx)
> for (css = &cgrp->css; css; css = css->parent) {
> cgrp = container_of(css, struct perf_cgroup, css);
> info = this_cpu_ptr(cgrp->info);
> - update_perf_time_ctx(&info->time, ctx->time.stamp, false);
> - __store_release(&info->active, 1);
> + if (guest) {
> + __update_cgrp_guest_time(info, ctx->time.stamp, false);
> + } else {
> + update_perf_time_ctx(&info->time, ctx->time.stamp,
> false);
> + __store_release(&info->active, 1);
> + }
> }
> }
>
> @@ -1104,7 +1162,7 @@ static inline int perf_cgroup_connect(pid_t pid, struct
> perf_event *event,
> }
>
> static inline void
> -perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx)
> +perf_cgroup_set_timestamp(struct perf_cpu_context *cpuctx, bool guest)
> {
> }
>
> @@ -1514,16 +1572,24 @@ static void perf_unpin_context(struct
> perf_event_context *ctx)
> */
> static void __update_context_time(struct perf_event_context *ctx, bool adv)
> {
> - u64 now = perf_clock();
> + lockdep_assert_held(&ctx->lock);
> +
> + update_perf_time_ctx(&ctx->time, perf_clock(), adv);
> +}
>
> +static void __update_context_guest_time(struct perf_event_context *ctx, bool
> adv)
> +{
> lockdep_assert_held(&ctx->lock);
>
> - update_perf_time_ctx(&ctx->time, now, adv);
> + /* must be called after __update_context_time(); */
> + update_perf_time_ctx(&ctx->timeguest, ctx->time.stamp, adv);
> }
>
> static void update_context_time(struct perf_event_context *ctx)
> {
> __update_context_time(ctx, true);
> + if (__this_cpu_read(perf_in_guest))
> + __update_context_guest_time(ctx, true);
> }
>
> static u64 perf_event_time(struct perf_event *event)
> @@ -1536,7 +1602,7 @@ static u64 perf_event_time(struct perf_event *event)
> if (is_cgroup_event(event))
> return perf_cgroup_event_time(event);
>
> - return ctx->time.time;
> + return __perf_event_time_ctx(event, &ctx->time);
> }
>
> static u64 perf_event_time_now(struct perf_event *event, u64 now)
> @@ -1550,10 +1616,9 @@ static u64 perf_event_time_now(struct perf_event
> *event, u64 now)
> return perf_cgroup_event_time_now(event, now);
>
> if (!(__load_acquire(&ctx->is_active) & EVENT_TIME))
> - return ctx->time.time;
> + return __perf_event_time_ctx(event, &ctx->time);
>
> - now += READ_ONCE(ctx->time.offset);
> - return now;
> + return __perf_event_time_ctx_now(event, &ctx->time, now);
> }
>
> static enum event_type_t get_event_type(struct perf_event *event)
> @@ -2384,20 +2449,23 @@ group_sched_out(struct perf_event *group_event,
> struct perf_event_context *ctx)
> }
>
> static inline void
> -__ctx_time_update(struct perf_cpu_context *cpuctx, struct perf_event_context
> *ctx, bool final)
> +__ctx_time_update(struct perf_cpu_context *cpuctx, struct perf_event_context
> *ctx,
> + bool final, enum event_type_t event_type)
> {
> if (ctx->is_active & EVENT_TIME) {
> if (ctx->is_active & EVENT_FROZEN)
> return;
> +
> update_context_time(ctx);
> - update_cgrp_time_from_cpuctx(cpuctx, final);
> + /* vPMU should not stop time */
> + update_cgrp_time_from_cpuctx(cpuctx, !(event_type &
> EVENT_GUEST) && final);
> }
> }
>
> static inline void
> ctx_time_update(struct perf_cpu_context *cpuctx, struct perf_event_context
> *ctx)
> {
> - __ctx_time_update(cpuctx, ctx, false);
> + __ctx_time_update(cpuctx, ctx, false, 0);
> }
>
> /*
> @@ -3405,7 +3473,7 @@ ctx_sched_out(struct perf_event_context *ctx, struct
> pmu *pmu, enum event_type_t
> *
> * would only update time for the pinned events.
> */
> - __ctx_time_update(cpuctx, ctx, ctx == &cpuctx->ctx);
> + __ctx_time_update(cpuctx, ctx, ctx == &cpuctx->ctx, event_type);
>
> /*
> * CPU-release for the below ->is_active store,
> @@ -3431,7 +3499,18 @@ ctx_sched_out(struct perf_event_context *ctx, struct
> pmu *pmu, enum event_type_t
> cpuctx->task_ctx = NULL;
> }
>
> - is_active ^= ctx->is_active; /* changed bits */
> + if (event_type & EVENT_GUEST) {
> + /*
> + * Schedule out all exclude_guest events of PMU
> + * with PERF_PMU_CAP_MEDIATED_VPMU.
> + */
> + is_active = EVENT_ALL;
> + __update_context_guest_time(ctx, false);
> + perf_cgroup_set_timestamp(cpuctx, true);
> + barrier();
> + } else {
> + is_active ^= ctx->is_active; /* changed bits */
> + }
>
> for_each_epc(pmu_ctx, ctx, pmu, event_type)
> __pmu_ctx_sched_out(pmu_ctx, is_active);
> @@ -3926,10 +4005,15 @@ static inline void group_update_userpage(struct
> perf_event *group_event)
> event_update_userpage(event);
> }
>
> +struct merge_sched_data {
> + int can_add_hw;
> + enum event_type_t event_type;
> +};
> +
> static int merge_sched_in(struct perf_event *event, void *data)
> {
> struct perf_event_context *ctx = event->ctx;
> - int *can_add_hw = data;
> + struct merge_sched_data *msd = data;
>
> if (event->state <= PERF_EVENT_STATE_OFF)
> return 0;
> @@ -3937,13 +4021,22 @@ static int merge_sched_in(struct perf_event *event,
> void *data)
> if (!event_filter_match(event))
> return 0;
>
> - if (group_can_go_on(event, *can_add_hw)) {
> + /*
> + * Don't schedule in any host events from PMU with
> + * PERF_PMU_CAP_MEDIATED_VPMU, while a guest is running.
> + */
> + if (__this_cpu_read(perf_in_guest) &&
> + event->pmu_ctx->pmu->capabilities & PERF_PMU_CAP_MEDIATED_VPMU &&
> + !(msd->event_type & EVENT_GUEST))
> + return 0;
> +
> + if (group_can_go_on(event, msd->can_add_hw)) {
> if (!group_sched_in(event, ctx))
> list_add_tail(&event->active_list,
> get_event_list(event));
> }
>
> if (event->state == PERF_EVENT_STATE_INACTIVE) {
> - *can_add_hw = 0;
> + msd->can_add_hw = 0;
> if (event->attr.pinned) {
> perf_cgroup_event_disable(event, ctx);
> perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
> @@ -3962,11 +4055,15 @@ static int merge_sched_in(struct perf_event *event,
> void *data)
>
> static void pmu_groups_sched_in(struct perf_event_context *ctx,
> struct perf_event_groups *groups,
> - struct pmu *pmu)
> + struct pmu *pmu,
> + enum event_type_t event_type)
> {
> - int can_add_hw = 1;
> + struct merge_sched_data msd = {
> + .can_add_hw = 1,
> + .event_type = event_type,
> + };
> visit_groups_merge(ctx, groups, smp_processor_id(), pmu,
> - merge_sched_in, &can_add_hw);
> + merge_sched_in, &msd);
> }
>
> static void __pmu_ctx_sched_in(struct perf_event_pmu_context *pmu_ctx,
> @@ -3975,9 +4072,9 @@ static void __pmu_ctx_sched_in(struct
> perf_event_pmu_context *pmu_ctx,
> struct perf_event_context *ctx = pmu_ctx->ctx;
>
> if (event_type & EVENT_PINNED)
> - pmu_groups_sched_in(ctx, &ctx->pinned_groups, pmu_ctx->pmu);
> + pmu_groups_sched_in(ctx, &ctx->pinned_groups, pmu_ctx->pmu,
> event_type);
> if (event_type & EVENT_FLEXIBLE)
> - pmu_groups_sched_in(ctx, &ctx->flexible_groups, pmu_ctx->pmu);
> + pmu_groups_sched_in(ctx, &ctx->flexible_groups, pmu_ctx->pmu,
> event_type);
> }
>
> static void
> @@ -3994,9 +4091,11 @@ ctx_sched_in(struct perf_event_context *ctx, struct
> pmu *pmu, enum event_type_t
> return;
>
> if (!(is_active & EVENT_TIME)) {
> + /* EVENT_TIME should be active while the guest runs */
> + WARN_ON_ONCE(event_type & EVENT_GUEST);
> /* start ctx time */
> __update_context_time(ctx, false);
> - perf_cgroup_set_timestamp(cpuctx);
> + perf_cgroup_set_timestamp(cpuctx, false);
> /*
> * CPU-release for the below ->is_active store,
> * see __load_acquire() in perf_event_time_now()
> @@ -4012,7 +4111,23 @@ ctx_sched_in(struct perf_event_context *ctx, struct
> pmu *pmu, enum event_type_t
> WARN_ON_ONCE(cpuctx->task_ctx != ctx);
> }
>
> - is_active ^= ctx->is_active; /* changed bits */
> + if (event_type & EVENT_GUEST) {
> + /*
> + * Schedule in the required exclude_guest events of PMU
> + * with PERF_PMU_CAP_MEDIATED_VPMU.
> + */
> + is_active = event_type & EVENT_ALL;
> +
> + /*
> + * Update ctx time to set the new start time for
> + * the exclude_guest events.
> + */
> + update_context_time(ctx);
> + update_cgrp_time_from_cpuctx(cpuctx, false);
> + barrier();
> + } else {
> + is_active ^= ctx->is_active; /* changed bits */
> + }
>
> /*
> * First go through the list and put on any pinned groups
> @@ -4020,13 +4135,13 @@ ctx_sched_in(struct perf_event_context *ctx, struct
> pmu *pmu, enum event_type_t
> */
> if (is_active & EVENT_PINNED) {
> for_each_epc(pmu_ctx, ctx, pmu, event_type)
> - __pmu_ctx_sched_in(pmu_ctx, EVENT_PINNED);
> + __pmu_ctx_sched_in(pmu_ctx, EVENT_PINNED | (event_type
> & EVENT_GUEST));
> }
>
> /* Then walk through the lower prio flexible groups */
> if (is_active & EVENT_FLEXIBLE) {
> for_each_epc(pmu_ctx, ctx, pmu, event_type)
> - __pmu_ctx_sched_in(pmu_ctx, EVENT_FLEXIBLE);
> + __pmu_ctx_sched_in(pmu_ctx, EVENT_FLEXIBLE |
> (event_type & EVENT_GUEST));
> }
> }
>
> @@ -6285,23 +6400,25 @@ void perf_event_update_userpage(struct perf_event
> *event)
> if (!rb)
> goto unlock;
>
> - /*
> - * compute total_time_enabled, total_time_running
> - * based on snapshot values taken when the event
> - * was last scheduled in.
> - *
> - * we cannot simply called update_context_time()
> - * because of locking issue as we can be called in
> - * NMI context
> - */
> - calc_timer_values(event, &now, &enabled, &running);
> -
> - userpg = rb->user_page;
> /*
> * Disable preemption to guarantee consistent time stamps are stored to
> * the user page.
> */
> preempt_disable();
> +
> + /*
> + * compute total_time_enabled, total_time_running
> + * based on snapshot values taken when the event
> + * was last scheduled in.
> + *
> + * we cannot simply called update_context_time()
> + * because of locking issue as we can be called in
> + * NMI context
> + */
> + calc_timer_values(event, &now, &enabled, &running);
> +
> + userpg = rb->user_page;
> +
> ++userpg->lock;
> barrier();
> userpg->index = perf_event_index(event);
> --
> 2.49.0.395.g12beb8f557-goog
>
