On 2024-12-13 4:37 a.m., Sandipan Das wrote:
> On 8/1/2024 10:28 AM, Mingwei Zhang wrote:
>> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>>
>> 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) <peterz@xxxxxxxxxxxxx>
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
>> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
>> ---
>> include/linux/perf_event.h | 6 ++
>> kernel/events/core.c | 178 +++++++++++++++++++++++++++++++------
>> 2 files changed, 155 insertions(+), 29 deletions(-)
>>
>> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
>> index e22cdb6486e6..81a5f8399cb8 100644
>> --- a/include/linux/perf_event.h
>> +++ b/include/linux/perf_event.h
>> @@ -952,6 +952,11 @@ struct perf_event_context {
>> */
>> struct perf_time_ctx time;
>>
>> + /*
>> + * Context clock, runs when in the guest mode.
>> + */
>> + struct perf_time_ctx timeguest;
>> +
>> /*
>> * These fields let us detect when two contexts have both
>> * been cloned (inherited) from a common ancestor.
>> @@ -1044,6 +1049,7 @@ 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 c25e2bf27001..57648736e43e 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -376,7 +376,8 @@ enum event_type_t {
>> /* see ctx_resched() for details */
>> EVENT_CPU = 0x8,
>> EVENT_CGROUP = 0x10,
>> - EVENT_FLAGS = EVENT_CGROUP,
>> + EVENT_GUEST = 0x20,
>> + EVENT_FLAGS = EVENT_CGROUP | EVENT_GUEST,
>> EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
>> };
>>
>> @@ -407,6 +408,7 @@ 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_PASSTHROUGH_VPMU */
>> static inline bool is_include_guest_event(struct perf_event *event)
>> @@ -706,6 +708,10 @@ 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_PASSTHROUGH_VPMU))
>> + return true;
>> +
>> return false;
>> }
>>
>> @@ -770,12 +776,21 @@ static inline int is_cgroup_event(struct perf_event *event)
>> return event->cgrp != NULL;
>> }
>>
>> +static inline u64 __perf_event_time_ctx(struct perf_event *event,
>> + struct perf_time_ctx *time,
>> + struct perf_time_ctx *timeguest);
>> +
>> +static inline u64 __perf_event_time_ctx_now(struct perf_event *event,
>> + struct perf_time_ctx *time,
>> + struct perf_time_ctx *timeguest,
>> + u64 now);
>> +
>> 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, &t->timeguest);
>> }
>>
>> static inline u64 perf_cgroup_event_time_now(struct perf_event *event, u64 now)
>> @@ -784,9 +799,9 @@ 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, &t->timeguest);
>> +
>> + return __perf_event_time_ctx_now(event, &t->time, &t->timeguest, now);
>> }
>>
>> static inline void update_perf_time_ctx(struct perf_time_ctx *time, u64 now, bool adv);
>> @@ -796,6 +811,18 @@ static inline void __update_cgrp_time(struct perf_cgroup_info *info, u64 now, bo
>> update_perf_time_ctx(&info->time, now, adv);
>> }
>>
>> +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_cgrp_time(info, 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)
>> {
>> struct perf_cgroup *cgrp = cpuctx->cgrp;
>> @@ -809,7 +836,7 @@ 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_cgrp_time(info, now, true);
>> + update_cgrp_time(info, now);
>> if (final)
>> __store_release(&info->active, 0);
>> }
>> @@ -832,11 +859,11 @@ 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_cgrp_time(info, 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;
>> @@ -856,8 +883,12 @@ 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_cgrp_time(info, ctx->time.stamp, false);
>> - __store_release(&info->active, 1);
>> + if (guest) {
>> + __update_cgrp_guest_time(info, ctx->time.stamp, false);
>> + } else {
>> + __update_cgrp_time(info, ctx->time.stamp, false);
>> + __store_release(&info->active, 1);
>> + }
>> }
>> }
>>
>> @@ -1061,7 +1092,7 @@ 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)
>> {
>> }
>>
>> @@ -1488,16 +1519,34 @@ static inline void update_perf_time_ctx(struct perf_time_ctx *time, u64 now, boo
>> */
>> 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 inline u64 __perf_event_time_ctx(struct perf_event *event,
>> + struct perf_time_ctx *time,
>> + struct perf_time_ctx *timeguest)
>> +{
>> + if (event->attr.exclude_guest)
>> + return time->time - timeguest->time;
>> + else
>> + return time->time;
>> }
>>
>> static u64 perf_event_time(struct perf_event *event)
>> @@ -1510,7 +1559,26 @@ 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, &ctx->timeguest);
>> +}
>> +
>> +static inline u64 __perf_event_time_ctx_now(struct perf_event *event,
>> + struct perf_time_ctx *time,
>> + struct perf_time_ctx *timeguest,
>> + u64 now)
>> +{
>> + /*
>> + * The exclude_guest event time should be calculated from
>> + * the ctx time - the guest time.
>> + * The ctx time is now + READ_ONCE(time->offset).
>> + * The guest time is now + READ_ONCE(timeguest->offset).
>> + * So the exclude_guest time is
>> + * READ_ONCE(time->offset) - READ_ONCE(timeguest->offset).
>> + */
>> + if (event->attr.exclude_guest && __this_cpu_read(perf_in_guest))
>> + return READ_ONCE(time->offset) - READ_ONCE(timeguest->offset);
>> + else
>> + return now + READ_ONCE(time->offset);
>> }
>>
>> static u64 perf_event_time_now(struct perf_event *event, u64 now)
>> @@ -1524,10 +1592,9 @@ 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, &ctx->timeguest);
>>
>> - now += READ_ONCE(ctx->time.offset);
>> - return now;
>> + return __perf_event_time_ctx_now(event, &ctx->time, &ctx->timeguest, now);
>> }
>>
>> static enum event_type_t get_event_type(struct perf_event *event)
>> @@ -3334,9 +3401,15 @@ ctx_sched_out(struct perf_event_context *ctx, enum event_type_t event_type)
>> * would only update time for the pinned events.
>> */
>> if (is_active & EVENT_TIME) {
>> + bool stop;
>> +
>> + /* vPMU should not stop time */
>> + stop = !(event_type & EVENT_GUEST) &&
>> + ctx == &cpuctx->ctx;
>> +
>> /* update (and stop) ctx time */
>> update_context_time(ctx);
>> - update_cgrp_time_from_cpuctx(cpuctx, ctx == &cpuctx->ctx);
>> + update_cgrp_time_from_cpuctx(cpuctx, stop);
>> /*
>> * CPU-release for the below ->is_active store,
>> * see __load_acquire() in perf_event_time_now()
>> @@ -3354,7 +3427,18 @@ ctx_sched_out(struct perf_event_context *ctx, enum event_type_t event_type)
>> 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_PASSTHROUGH_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 */
>> + }
>>
>> list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry) {
>> if (perf_skip_pmu_ctx(pmu_ctx, event_type))
>> @@ -3853,10 +3937,15 @@ 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;
>> @@ -3864,13 +3953,22 @@ 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 exclude_guest events of PMU with
>> + * PERF_PMU_CAP_PASSTHROUGH_VPMU, while a guest is running.
>> + */
>> + if (__this_cpu_read(perf_in_guest) && event->attr.exclude_guest &&
>> + event->pmu->capabilities & PERF_PMU_CAP_PASSTHROUGH_VPMU &&
>> + !(msd->event_type & EVENT_GUEST))
>> + return 0;
>> +
>
> It is possible for event groups to have a mix of software and core PMU events.
> If the group leader is a software event, event->pmu will point to the software
> PMU but event->pmu_ctx->pmu will point to the core PMU. When perf_in_guest is
> true for a CPU and the group leader is passed to merge_sched_in(), the condition
> above fails as the software PMU does not have PERF_PMU_CAP_PASSTHROUGH_VPMU
> capability. This can lead to group_sched_in() getting called later where all
> the sibling events, which includes core PMU events that are not supposed to
> be scheduled in, to be brought in. So event->pmu_ctx->pmu->capabilities needs
> to be looked at instead.
Right, Thanks.
I will fix it in the next version.
Thanks,
Kan
>
>> + 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);
>> @@ -3889,11 +3987,15 @@ 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 ctx_groups_sched_in(struct perf_event_context *ctx,
>> @@ -3905,14 +4007,14 @@ static void ctx_groups_sched_in(struct perf_event_context *ctx,
>> list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry) {
>> if (perf_skip_pmu_ctx(pmu_ctx, event_type))
>> continue;
>> - pmu_groups_sched_in(ctx, groups, pmu_ctx->pmu);
>> + pmu_groups_sched_in(ctx, groups, pmu_ctx->pmu, event_type);
>> }
>> }
>>
>> static void __pmu_ctx_sched_in(struct perf_event_context *ctx,
>> struct pmu *pmu)
>> {
>> - pmu_groups_sched_in(ctx, &ctx->flexible_groups, pmu);
>> + pmu_groups_sched_in(ctx, &ctx->flexible_groups, pmu, 0);
>> }
>>
>> static void
>> @@ -3927,9 +4029,11 @@ ctx_sched_in(struct perf_event_context *ctx, enum event_type_t event_type)
>> 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()
>> @@ -3945,7 +4049,23 @@ ctx_sched_in(struct perf_event_context *ctx, enum event_type_t event_type)
>> WARN_ON_ONCE(cpuctx->task_ctx != ctx);
>> }
>>
>> - is_active ^= ctx->is_active; /* changed bits */
>> + if (event_type & EVENT_GUEST) {
>> + /*
>> + * Schedule in all !exclude_guest events of PMU
>> + * with PERF_PMU_CAP_PASSTHROUGH_VPMU.
>> + */
>> + is_active = 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
>
>
