6.12-stable review patch. If anyone has any objections, please let me know.
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From: Adrian Hunter adrian.hunter@intel.com
[ Upstream commit 18d92bb57c39504d9da11c6ef604f58eb1d5a117 ]
Hardware traces, such as instruction traces, can produce a vast amount of trace data, so being able to reduce tracing to more specific circumstances can be useful.
The ability to pause or resume tracing when another event happens, can do that.
Add ability for an event to "pause" or "resume" AUX area tracing.
Add aux_pause bit to perf_event_attr to indicate that, if the event happens, the associated AUX area tracing should be paused. Ditto aux_resume. Do not allow aux_pause and aux_resume to be set together.
Add aux_start_paused bit to perf_event_attr to indicate to an AUX area event that it should start in a "paused" state.
Add aux_paused to struct hw_perf_event for AUX area events to keep track of the "paused" state. aux_paused is initialized to aux_start_paused.
Add PERF_EF_PAUSE and PERF_EF_RESUME modes for ->stop() and ->start() callbacks. Call as needed, during __perf_event_output(). Add aux_in_pause_resume to struct perf_buffer to prevent races with the NMI handler. Pause/resume in NMI context will miss out if it coincides with another pause/resume.
To use aux_pause or aux_resume, an event must be in a group with the AUX area event as the group leader.
Example (requires Intel PT and tools patches also):
$ perf record --kcore -e intel_pt/aux-action=start-paused/k,syscalls:sys_enter_newuname/aux-action=resume/,syscalls:sys_exit_newuname/aux-action=pause/ uname Linux [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.043 MB perf.data ] $ perf script --call-trace uname 30805 [000] 24001.058782799: name: 0x7ffc9c1865b0 uname 30805 [000] 24001.058784424: psb offs: 0 uname 30805 [000] 24001.058784424: cbr: 39 freq: 3904 MHz (139%) uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __x64_sys_newuname uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) down_read uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __cond_resched uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) in_lock_functions uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_sub uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) up_read uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) in_lock_functions uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) preempt_count_sub uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) _copy_to_user uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_to_user_mode uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_work uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) perf_syscall_exit uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_alloc uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_get_recursion_context uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_tp_event uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_update uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) tracing_gen_ctx_irq_test uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_event uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __perf_event_account_interrupt uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __this_cpu_preempt_check uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_output_forward uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_aux_pause uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) ring_buffer_get uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_lock uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_unlock uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) pt_event_stop uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) native_write_msr uname 30805 [000] 24001.058785463: ([kernel.kallsyms]) native_write_msr uname 30805 [000] 24001.058785639: 0x0
Signed-off-by: Adrian Hunter adrian.hunter@intel.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: James Clark james.clark@arm.com Link: https://lkml.kernel.org/r/20241022155920.17511-3-adrian.hunter@intel.com Stable-dep-of: 56799bc03565 ("perf: Fix hang while freeing sigtrap event") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/perf_event.h | 28 ++++++++++++ include/uapi/linux/perf_event.h | 11 ++++- kernel/events/core.c | 75 +++++++++++++++++++++++++++++++-- kernel/events/internal.h | 1 + 4 files changed, 110 insertions(+), 5 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 347901525a46a..19551d664bce2 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -170,6 +170,12 @@ struct hw_perf_event { }; struct { /* aux / Intel-PT */ u64 aux_config; + /* + * For AUX area events, aux_paused cannot be a state + * flag because it can be updated asynchronously to + * state. + */ + unsigned int aux_paused; }; struct { /* software */ struct hrtimer hrtimer; @@ -294,6 +300,7 @@ struct perf_event_pmu_context; #define PERF_PMU_CAP_NO_EXCLUDE 0x0040 #define PERF_PMU_CAP_AUX_OUTPUT 0x0080 #define PERF_PMU_CAP_EXTENDED_HW_TYPE 0x0100 +#define PERF_PMU_CAP_AUX_PAUSE 0x0200
/** * pmu::scope @@ -384,6 +391,8 @@ struct pmu { #define PERF_EF_START 0x01 /* start the counter when adding */ #define PERF_EF_RELOAD 0x02 /* reload the counter when starting */ #define PERF_EF_UPDATE 0x04 /* update the counter when stopping */ +#define PERF_EF_PAUSE 0x08 /* AUX area event, pause tracing */ +#define PERF_EF_RESUME 0x10 /* AUX area event, resume tracing */
/* * Adds/Removes a counter to/from the PMU, can be done inside a @@ -423,6 +432,18 @@ struct pmu { * * ->start() with PERF_EF_RELOAD will reprogram the counter * value, must be preceded by a ->stop() with PERF_EF_UPDATE. + * + * ->stop() with PERF_EF_PAUSE will stop as simply as possible. Will not + * overlap another ->stop() with PERF_EF_PAUSE nor ->start() with + * PERF_EF_RESUME. + * + * ->start() with PERF_EF_RESUME will start as simply as possible but + * only if the counter is not otherwise stopped. Will not overlap + * another ->start() with PERF_EF_RESUME nor ->stop() with + * PERF_EF_PAUSE. + * + * Notably, PERF_EF_PAUSE/PERF_EF_RESUME *can* be concurrent with other + * ->stop()/->start() invocations, just not itself. */ void (*start) (struct perf_event *event, int flags); void (*stop) (struct perf_event *event, int flags); @@ -1685,6 +1706,13 @@ static inline bool has_aux(struct perf_event *event) return event->pmu->setup_aux; }
+static inline bool has_aux_action(struct perf_event *event) +{ + return event->attr.aux_sample_size || + event->attr.aux_pause || + event->attr.aux_resume; +} + static inline bool is_write_backward(struct perf_event *event) { return !!event->attr.write_backward; diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 4842c36fdf801..0524d541d4e3d 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -511,7 +511,16 @@ struct perf_event_attr { __u16 sample_max_stack; __u16 __reserved_2; __u32 aux_sample_size; - __u32 __reserved_3; + + union { + __u32 aux_action; + struct { + __u32 aux_start_paused : 1, /* start AUX area tracing paused */ + aux_pause : 1, /* on overflow, pause AUX area tracing */ + aux_resume : 1, /* on overflow, resume AUX area tracing */ + __reserved_3 : 29; + }; + };
/* * User provided data if sigtrap=1, passed back to user via diff --git a/kernel/events/core.c b/kernel/events/core.c index b5ccf52bb71ba..bee6f88d0556b 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2146,7 +2146,7 @@ static void perf_put_aux_event(struct perf_event *event)
static bool perf_need_aux_event(struct perf_event *event) { - return !!event->attr.aux_output || !!event->attr.aux_sample_size; + return event->attr.aux_output || has_aux_action(event); }
static int perf_get_aux_event(struct perf_event *event, @@ -2171,6 +2171,10 @@ static int perf_get_aux_event(struct perf_event *event, !perf_aux_output_match(event, group_leader)) return 0;
+ if ((event->attr.aux_pause || event->attr.aux_resume) && + !(group_leader->pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE)) + return 0; + if (event->attr.aux_sample_size && !group_leader->pmu->snapshot_aux) return 0;
@@ -8029,6 +8033,49 @@ void perf_prepare_header(struct perf_event_header *header, WARN_ON_ONCE(header->size & 7); }
+static void __perf_event_aux_pause(struct perf_event *event, bool pause) +{ + if (pause) { + if (!event->hw.aux_paused) { + event->hw.aux_paused = 1; + event->pmu->stop(event, PERF_EF_PAUSE); + } + } else { + if (event->hw.aux_paused) { + event->hw.aux_paused = 0; + event->pmu->start(event, PERF_EF_RESUME); + } + } +} + +static void perf_event_aux_pause(struct perf_event *event, bool pause) +{ + struct perf_buffer *rb; + + if (WARN_ON_ONCE(!event)) + return; + + rb = ring_buffer_get(event); + if (!rb) + return; + + scoped_guard (irqsave) { + /* + * Guard against self-recursion here. Another event could trip + * this same from NMI context. + */ + if (READ_ONCE(rb->aux_in_pause_resume)) + break; + + WRITE_ONCE(rb->aux_in_pause_resume, 1); + barrier(); + __perf_event_aux_pause(event, pause); + barrier(); + WRITE_ONCE(rb->aux_in_pause_resume, 0); + } + ring_buffer_put(rb); +} + static __always_inline int __perf_event_output(struct perf_event *event, struct perf_sample_data *data, @@ -9832,9 +9879,12 @@ static int __perf_event_overflow(struct perf_event *event,
ret = __perf_event_account_interrupt(event, throttle);
+ if (event->attr.aux_pause) + perf_event_aux_pause(event->aux_event, true); + if (event->prog && event->prog->type == BPF_PROG_TYPE_PERF_EVENT && !bpf_overflow_handler(event, data, regs)) - return ret; + goto out;
/* * XXX event_limit might not quite work as expected on inherited @@ -9896,6 +9946,9 @@ static int __perf_event_overflow(struct perf_event *event, event->pending_wakeup = 1; irq_work_queue(&event->pending_irq); } +out: + if (event->attr.aux_resume) + perf_event_aux_pause(event->aux_event, false);
return ret; } @@ -12312,11 +12365,25 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, }
if (event->attr.aux_output && - !(pmu->capabilities & PERF_PMU_CAP_AUX_OUTPUT)) { + (!(pmu->capabilities & PERF_PMU_CAP_AUX_OUTPUT) || + event->attr.aux_pause || event->attr.aux_resume)) { err = -EOPNOTSUPP; goto err_pmu; }
+ if (event->attr.aux_pause && event->attr.aux_resume) { + err = -EINVAL; + goto err_pmu; + } + + if (event->attr.aux_start_paused) { + if (!(pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE)) { + err = -EOPNOTSUPP; + goto err_pmu; + } + event->hw.aux_paused = 1; + } + if (cgroup_fd != -1) { err = perf_cgroup_connect(cgroup_fd, event, attr, group_leader); if (err) @@ -13112,7 +13179,7 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, * Grouping is not supported for kernel events, neither is 'AUX', * make sure the caller's intentions are adjusted. */ - if (attr->aux_output) + if (attr->aux_output || attr->aux_action) return ERR_PTR(-EINVAL);
event = perf_event_alloc(attr, cpu, task, NULL, NULL, diff --git a/kernel/events/internal.h b/kernel/events/internal.h index e072d995d670f..249288d82b8dc 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -52,6 +52,7 @@ struct perf_buffer { void (*free_aux)(void *); refcount_t aux_refcount; int aux_in_sampling; + int aux_in_pause_resume; void **aux_pages; void *aux_priv;