[PATCH V5 00/12] perf/core: Add ability for an event to "pause" or "resume" AUX area tracing

[PATCH V5 00/12] perf/core: Add ability for an event to "pause" or "resume" AUX area tracing

[Adrian Hunter]

Hi

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.

These patches add such a facilty and show how it would work for Intel
Processor Trace.

Maintainers of other AUX area tracing implementations are requested to
consider if this is something they might employ and then whether or not
the ABI would work for them.  Note, thank you to James Clark (ARM) for
evaluating the API for Coresight.  Suzuki K Poulose (ARM) also responded
positively to the RFC.

Changes to perf tools are now (since V4) fleshed out.


Changes in V5:

    perf/core: Add aux_pause, aux_resume, aux_start_paused
	Added James' Ack

    perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
	New patch

    perf tools
	Added Ian's Ack

Changes in V4:

    perf/core: Add aux_pause, aux_resume, aux_start_paused
	Rename aux_output_cfg -> aux_action
	Reorder aux_action bits from:
		aux_pause, aux_resume, aux_start_paused
	to:
		aux_start_paused, aux_pause, aux_resume
	Fix aux_action bits __u64 -> __u32

    coresight: Have a stab at support for pause / resume
	Dropped

    perf tools
	All new patches

Changes in RFC V3:

    coresight: Have a stab at support for pause / resume
	'mode' -> 'flags' so it at least compiles

Changes in RFC V2:

	Use ->stop() / ->start() instead of ->pause_resume()
	Move aux_start_paused bit into aux_output_cfg
	Tighten up when Intel PT pause / resume is allowed
	Add an example of how it might work for CoreSight


Adrian Hunter (12):
      perf/core: Add aux_pause, aux_resume, aux_start_paused
      perf/x86/intel/pt: Add support for pause / resume
      perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
      perf tools: Enable evsel__is_aux_event() to work for ARM/ARM64
      perf tools: Enable evsel__is_aux_event() to work for S390_CPUMSF
      perf tools: Add aux_start_paused, aux_pause and aux_resume
      perf tools: Add aux-action config term
      perf tools: Parse aux-action
      perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume
      perf intel-pt: Improve man page format
      perf intel-pt: Add documentation for pause / resume
      perf intel-pt: Add a test for pause / resume

 arch/x86/events/intel/core.c               |  10 +-
 arch/x86/events/intel/pt.c                 |  63 ++-
 arch/x86/events/intel/pt.h                 |   4 +
 include/linux/perf_event.h                 |  15 +
 include/uapi/linux/perf_event.h            |  11 +-
 kernel/events/core.c                       |  72 +++-
 kernel/events/internal.h                   |   1 +
 tools/include/uapi/linux/perf_event.h      |  11 +-
 tools/perf/Documentation/perf-intel-pt.txt | 596 ++++++++++++++++++-----------
 tools/perf/Documentation/perf-record.txt   |   4 +
 tools/perf/arch/arm/util/pmu.c             |   3 +
 tools/perf/builtin-record.c                |   4 +-
 tools/perf/tests/shell/test_intel_pt.sh    |  28 ++
 tools/perf/util/auxtrace.c                 |  67 +++-
 tools/perf/util/auxtrace.h                 |   6 +-
 tools/perf/util/evsel.c                    |  13 +-
 tools/perf/util/evsel.h                    |   1 +
 tools/perf/util/evsel_config.h             |   1 +
 tools/perf/util/parse-events.c             |  10 +
 tools/perf/util/parse-events.h             |   1 +
 tools/perf/util/parse-events.l             |   1 +
 tools/perf/util/perf_event_attr_fprintf.c  |   3 +
 tools/perf/util/pmu.c                      |   6 +-
 23 files changed, 691 insertions(+), 240 deletions(-)


Regards
Adrian

[PATCH V5 01/12] perf/core: Add aux_pause, aux_resume, aux_start_paused

[Adrian Hunter]

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 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>
Acked-by: James Clark <james.clark@arm.com>
---


Changes in V5:
	Added James' Ack

Changes in V4:
	Rename aux_output_cfg -> aux_action
	Reorder aux_action bits from:
		aux_pause, aux_resume, aux_start_paused
	to:
		aux_start_paused, aux_pause, aux_resume
	Fix aux_action bits __u64 -> __u32


 include/linux/perf_event.h      | 15 +++++++
 include/uapi/linux/perf_event.h | 11 ++++-
 kernel/events/core.c            | 72 +++++++++++++++++++++++++++++++--
 kernel/events/internal.h        |  1 +
 4 files changed, 95 insertions(+), 4 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0c6f8a..6c1600b9bdb3 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -291,6 +291,7 @@ 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
 
 struct perf_output_handle;
 
@@ -363,6 +364,8 @@ 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
@@ -402,6 +405,15 @@ 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.
 	 */
 	void (*start)			(struct perf_event *event, int flags);
 	void (*stop)			(struct perf_event *event, int flags);
@@ -798,6 +810,9 @@ struct perf_event {
 	/* for aux_output events */
 	struct perf_event		*aux_event;
 
+	/* for AUX area events */
+	unsigned int			aux_paused;
+
 	void (*destroy)(struct perf_event *);
 	struct rcu_head			rcu_head;
 
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 3a64499b0f5d..0c557f0a17b3 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 f0f0f71213a1..00f6d0a327e8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2097,7 +2097,8 @@ 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 || event->attr.aux_sample_size ||
+	       event->attr.aux_pause || event->attr.aux_resume;
 }
 
 static int perf_get_aux_event(struct perf_event *event,
@@ -2122,6 +2123,10 @@ 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;
 
@@ -7854,6 +7859,47 @@ 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 (!READ_ONCE(event->aux_paused)) {
+			WRITE_ONCE(event->aux_paused, 1);
+			event->pmu->stop(event, PERF_EF_PAUSE);
+		}
+	} else {
+		if (READ_ONCE(event->aux_paused)) {
+			WRITE_ONCE(event->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;
+	unsigned long flags;
+
+	if (WARN_ON_ONCE(!event))
+		return;
+
+	rb = ring_buffer_get(event);
+	if (!rb)
+		return;
+
+	local_irq_save(flags);
+	/* Guard against NMI, NMI loses here */
+	if (READ_ONCE(rb->aux_in_pause_resume))
+		goto out_restore;
+	WRITE_ONCE(rb->aux_in_pause_resume, 1);
+	barrier();
+	__perf_event_aux_pause(event, pause);
+	barrier();
+	WRITE_ONCE(rb->aux_in_pause_resume, 0);
+out_restore:
+	local_irq_restore(flags);
+	ring_buffer_put(rb);
+}
+
 static __always_inline int
 __perf_event_output(struct perf_event *event,
 		    struct perf_sample_data *data,
@@ -7867,6 +7913,9 @@ __perf_event_output(struct perf_event *event,
 	struct perf_event_header header;
 	int err;
 
+	if (event->attr.aux_pause)
+		perf_event_aux_pause(event->aux_event, true);
+
 	/* protect the callchain buffers */
 	rcu_read_lock();
 
@@ -7883,6 +7932,10 @@ __perf_event_output(struct perf_event *event,
 
 exit:
 	rcu_read_unlock();
+
+	if (event->attr.aux_resume)
+		perf_event_aux_pause(event->aux_event, false);
+
 	return err;
 }
 
@@ -12036,10 +12089,23 @@ 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 &&
+	    !(pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE)) {
 		err = -EOPNOTSUPP;
 		goto err_pmu;
 	}
+	event->aux_paused = event->attr.aux_start_paused;
 
 	if (cgroup_fd != -1) {
 		err = perf_cgroup_connect(cgroup_fd, event, attr, group_leader);
@@ -12836,7 +12902,7 @@ 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 5150d5f84c03..3320f78117dc 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -51,6 +51,7 @@ 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;
 
-- 
2.34.1

[PATCH V5 02/12] perf/x86/intel/pt: Add support for pause / resume

[Adrian Hunter]

Prevent tracing to start if aux_paused.

Implement support for PERF_EF_PAUSE / PERF_EF_RESUME. When aux_paused, stop
tracing. When not aux_paused, only start tracing if it isn't currently
meant to be stopped.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 arch/x86/events/intel/pt.c | 63 ++++++++++++++++++++++++++++++++++++--
 arch/x86/events/intel/pt.h |  4 +++
 2 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 8e2a12235e62..b6e838f2c6d5 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -418,6 +418,9 @@ static void pt_config_start(struct perf_event *event)
 	struct pt *pt = this_cpu_ptr(&pt_ctx);
 	u64 ctl = event->hw.config;
 
+	if (READ_ONCE(event->aux_paused))
+		return;
+
 	ctl |= RTIT_CTL_TRACEEN;
 	if (READ_ONCE(pt->vmx_on))
 		perf_aux_output_flag(&pt->handle, PERF_AUX_FLAG_PARTIAL);
@@ -534,7 +537,20 @@ static void pt_config(struct perf_event *event)
 	reg |= (event->attr.config & PT_CONFIG_MASK);
 
 	event->hw.config = reg;
+
+	/*
+	 * Allow resume before starting so as not to overwrite a value set by a
+	 * PMI.
+	 */
+	WRITE_ONCE(pt->resume_allowed, 1);
+
 	pt_config_start(event);
+
+	/*
+	 * Allow pause after starting so its pt_config_stop() doesn't race with
+	 * pt_config_start().
+	 */
+	WRITE_ONCE(pt->pause_allowed, 1);
 }
 
 static void pt_config_stop(struct perf_event *event)
@@ -1511,6 +1527,7 @@ void intel_pt_interrupt(void)
 		buf = perf_aux_output_begin(&pt->handle, event);
 		if (!buf) {
 			event->hw.state = PERF_HES_STOPPED;
+			pt->resume_allowed = 0;
 			return;
 		}
 
@@ -1519,6 +1536,7 @@ void intel_pt_interrupt(void)
 		ret = pt_buffer_reset_markers(buf, &pt->handle);
 		if (ret) {
 			perf_aux_output_end(&pt->handle, 0);
+			pt->resume_allowed = 0;
 			return;
 		}
 
@@ -1573,6 +1591,26 @@ static void pt_event_start(struct perf_event *event, int mode)
 	struct pt *pt = this_cpu_ptr(&pt_ctx);
 	struct pt_buffer *buf;
 
+	if (mode & PERF_EF_RESUME) {
+		if (READ_ONCE(pt->resume_allowed)) {
+			u64 status;
+
+			/*
+			 * Only if the trace is not active and the error and
+			 * stopped bits are clear, is it safe to start, but a
+			 * PMI might have just cleared these, so resume_allowed
+			 * must be checked again also.
+			 */
+			rdmsrl(MSR_IA32_RTIT_STATUS, status);
+			if (!(status & (RTIT_STATUS_TRIGGEREN |
+					RTIT_STATUS_ERROR |
+					RTIT_STATUS_STOPPED)) &&
+			   READ_ONCE(pt->resume_allowed))
+				pt_config_start(event);
+		}
+		return;
+	}
+
 	buf = perf_aux_output_begin(&pt->handle, event);
 	if (!buf)
 		goto fail_stop;
@@ -1601,6 +1639,16 @@ static void pt_event_stop(struct perf_event *event, int mode)
 {
 	struct pt *pt = this_cpu_ptr(&pt_ctx);
 
+	if (mode & PERF_EF_PAUSE) {
+		if (READ_ONCE(pt->pause_allowed))
+			pt_config_stop(event);
+		return;
+	}
+
+	/* Protect against racing */
+	WRITE_ONCE(pt->pause_allowed, 0);
+	WRITE_ONCE(pt->resume_allowed, 0);
+
 	/*
 	 * Protect against the PMI racing with disabling wrmsr,
 	 * see comment in intel_pt_interrupt().
@@ -1659,8 +1707,12 @@ static long pt_event_snapshot_aux(struct perf_event *event,
 	/*
 	 * Here, handle_nmi tells us if the tracing is on
 	 */
-	if (READ_ONCE(pt->handle_nmi))
+	if (READ_ONCE(pt->handle_nmi)) {
+		/* Protect against racing */
+		WRITE_ONCE(pt->pause_allowed, 0);
+		WRITE_ONCE(pt->resume_allowed, 0);
 		pt_config_stop(event);
+	}
 
 	pt_read_offset(buf);
 	pt_update_head(pt);
@@ -1677,8 +1729,11 @@ static long pt_event_snapshot_aux(struct perf_event *event,
 	 * Compiler barrier not needed as we couldn't have been
 	 * preempted by anything that touches pt->handle_nmi.
 	 */
-	if (pt->handle_nmi)
+	if (pt->handle_nmi) {
+		WRITE_ONCE(pt->resume_allowed, 1);
 		pt_config_start(event);
+		WRITE_ONCE(pt->pause_allowed, 1);
+	}
 
 	return ret;
 }
@@ -1794,7 +1849,9 @@ static __init int pt_init(void)
 	if (!intel_pt_validate_hw_cap(PT_CAP_topa_multiple_entries))
 		pt_pmu.pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG;
 
-	pt_pmu.pmu.capabilities	|= PERF_PMU_CAP_EXCLUSIVE | PERF_PMU_CAP_ITRACE;
+	pt_pmu.pmu.capabilities		|= PERF_PMU_CAP_EXCLUSIVE |
+					   PERF_PMU_CAP_ITRACE |
+					   PERF_PMU_CAP_AUX_PAUSE;
 	pt_pmu.pmu.attr_groups		 = pt_attr_groups;
 	pt_pmu.pmu.task_ctx_nr		 = perf_sw_context;
 	pt_pmu.pmu.event_init		 = pt_event_init;
diff --git a/arch/x86/events/intel/pt.h b/arch/x86/events/intel/pt.h
index 96906a62aacd..b9527205e028 100644
--- a/arch/x86/events/intel/pt.h
+++ b/arch/x86/events/intel/pt.h
@@ -117,6 +117,8 @@ struct pt_filters {
  * @filters:		last configured filters
  * @handle_nmi:		do handle PT PMI on this cpu, there's an active event
  * @vmx_on:		1 if VMX is ON on this cpu
+ * @pause_allowed:	PERF_EF_PAUSE is allowed to stop tracing
+ * @resume_allowed:	PERF_EF_RESUME is allowed to start tracing
  * @output_base:	cached RTIT_OUTPUT_BASE MSR value
  * @output_mask:	cached RTIT_OUTPUT_MASK MSR value
  */
@@ -125,6 +127,8 @@ struct pt {
 	struct pt_filters	filters;
 	int			handle_nmi;
 	int			vmx_on;
+	int			pause_allowed;
+	int			resume_allowed;
 	u64			output_base;
 	u64			output_mask;
 };
-- 
2.34.1

[PATCH V5 03/12] perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling

[Adrian Hunter]

Events with aux actions or aux sampling expect the PMI to coincide with the
event, which does not happen for large PEBS, so do not enable large PEBS in
that case.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
 arch/x86/events/intel/core.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 3804f21ab049..d50f4325d42a 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3885,6 +3885,12 @@ static inline bool intel_pmu_has_cap(struct perf_event *event, int idx)
 	return test_bit(idx, (unsigned long *)&intel_cap->capabilities);
 }
 
+static inline bool has_aux_action(struct perf_event *event)
+{
+	return event->attr.aux_pause || event->attr.aux_resume ||
+	       event->attr.aux_sample_size;
+}
+
 static int intel_pmu_hw_config(struct perf_event *event)
 {
 	int ret = x86_pmu_hw_config(event);
@@ -3902,8 +3908,8 @@ static int intel_pmu_hw_config(struct perf_event *event)
 
 		if (!(event->attr.freq || (event->attr.wakeup_events && !event->attr.watermark))) {
 			event->hw.flags |= PERF_X86_EVENT_AUTO_RELOAD;
-			if (!(event->attr.sample_type &
-			      ~intel_pmu_large_pebs_flags(event))) {
+			if (!(event->attr.sample_type & ~intel_pmu_large_pebs_flags(event)) &&
+			    !has_aux_action(event)) {
 				event->hw.flags |= PERF_X86_EVENT_LARGE_PEBS;
 				event->attach_state |= PERF_ATTACH_SCHED_CB;
 			}
-- 
2.34.1

[PATCH V5 04/12] perf tools: Enable evsel__is_aux_event() to work for ARM/ARM64

[Adrian Hunter]

Set pmu->auxtrace on ARM/ARM64 AUX area PMUs. evsel__is_aux_event() needs
the setting to identify AUX area tracing selected events.

Currently, the features that use evsel__is_aux_event() are used only by
Intel PT, but that may change in the future.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/perf/arch/arm/util/pmu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/arch/arm/util/pmu.c b/tools/perf/arch/arm/util/pmu.c
index 8b7cb68ba1a8..668a4310cb69 100644
--- a/tools/perf/arch/arm/util/pmu.c
+++ b/tools/perf/arch/arm/util/pmu.c
@@ -20,16 +20,19 @@ void perf_pmu__arch_init(struct perf_pmu *pmu __maybe_unused)
 #ifdef HAVE_AUXTRACE_SUPPORT
 	if (!strcmp(pmu->name, CORESIGHT_ETM_PMU_NAME)) {
 		/* add ETM default config here */
+		pmu->auxtrace = true;
 		pmu->selectable = true;
 		pmu->perf_event_attr_init_default = cs_etm_get_default_config;
 #if defined(__aarch64__)
 	} else if (strstarts(pmu->name, ARM_SPE_PMU_NAME)) {
+		pmu->auxtrace = true;
 		pmu->selectable = true;
 		pmu->is_uncore = false;
 		pmu->perf_event_attr_init_default = arm_spe_pmu_default_config;
 		if (!strcmp(pmu->name, "arm_spe_0"))
 			pmu->mem_events = perf_mem_events_arm;
 	} else if (strstarts(pmu->name, HISI_PTT_PMU_NAME)) {
+		pmu->auxtrace = true;
 		pmu->selectable = true;
 #endif
 	}
-- 
2.34.1

[PATCH V5 05/12] perf tools: Enable evsel__is_aux_event() to work for S390_CPUMSF

[Adrian Hunter]

evsel__is_aux_event() identifies AUX area tracing selected events.

S390_CPUMSF uses a raw event type (PERF_TYPE_RAW - refer
s390_cpumsf_evsel_is_auxtrace()) not a PMU type value that could be checked
in evsel__is_aux_event(). However it sets needs_auxtrace_mmap (refer
auxtrace_record__init()), so check that first.

Currently, the features that use evsel__is_aux_event() are used only by
Intel PT, but that may change in the future.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/pmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 437386dedd5c..40be43f1f648 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1099,8 +1099,12 @@ void perf_pmu__warn_invalid_formats(struct perf_pmu *pmu)
 
 bool evsel__is_aux_event(const struct evsel *evsel)
 {
-	struct perf_pmu *pmu = evsel__find_pmu(evsel);
+	struct perf_pmu *pmu;
+
+	if (evsel->needs_auxtrace_mmap)
+		return true;
 
+	pmu = evsel__find_pmu(evsel);
 	return pmu && pmu->auxtrace;
 }
 
-- 
2.34.1

[PATCH V5 06/12] perf tools: Add aux_start_paused, aux_pause and aux_resume

[Adrian Hunter]

Add struct perf_event_attr members to support pause and resume of AUX area
tracing.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/include/uapi/linux/perf_event.h     | 11 ++++++++++-
 tools/perf/util/perf_event_attr_fprintf.c |  3 +++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 3a64499b0f5d..0c557f0a17b3 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/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/tools/perf/util/perf_event_attr_fprintf.c b/tools/perf/util/perf_event_attr_fprintf.c
index 8f04d3b7f3ec..0e3cb35aab33 100644
--- a/tools/perf/util/perf_event_attr_fprintf.c
+++ b/tools/perf/util/perf_event_attr_fprintf.c
@@ -323,6 +323,9 @@ int perf_event_attr__fprintf(FILE *fp, struct perf_event_attr *attr,
 	PRINT_ATTRf(sample_max_stack, p_unsigned);
 	PRINT_ATTRf(aux_sample_size, p_unsigned);
 	PRINT_ATTRf(sig_data, p_unsigned);
+	PRINT_ATTRf(aux_start_paused, p_unsigned);
+	PRINT_ATTRf(aux_pause, p_unsigned);
+	PRINT_ATTRf(aux_resume, p_unsigned);
 
 	return ret;
 }
-- 
2.34.1

[PATCH V5 07/12] perf tools: Add aux-action config term

[Adrian Hunter]

Add a new common config term "aux-action" to use for configuring AUX area
trace pause / resume. The value is a string that will be parsed in a
subsequent patch.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/evsel.c        |  2 ++
 tools/perf/util/evsel_config.h |  1 +
 tools/perf/util/parse-events.c | 10 ++++++++++
 tools/perf/util/parse-events.h |  1 +
 tools/perf/util/parse-events.l |  1 +
 5 files changed, 15 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 3536404e9447..866c69f83595 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1001,6 +1001,8 @@ static void evsel__apply_config_terms(struct evsel *evsel,
 		case EVSEL__CONFIG_TERM_AUX_OUTPUT:
 			attr->aux_output = term->val.aux_output ? 1 : 0;
 			break;
+		case EVSEL__CONFIG_TERM_AUX_ACTION:
+			break;
 		case EVSEL__CONFIG_TERM_AUX_SAMPLE_SIZE:
 			/* Already applied by auxtrace */
 			break;
diff --git a/tools/perf/util/evsel_config.h b/tools/perf/util/evsel_config.h
index aee6f808b512..af52a1516d0b 100644
--- a/tools/perf/util/evsel_config.h
+++ b/tools/perf/util/evsel_config.h
@@ -25,6 +25,7 @@ enum evsel_term_type {
 	EVSEL__CONFIG_TERM_BRANCH,
 	EVSEL__CONFIG_TERM_PERCORE,
 	EVSEL__CONFIG_TERM_AUX_OUTPUT,
+	EVSEL__CONFIG_TERM_AUX_ACTION,
 	EVSEL__CONFIG_TERM_AUX_SAMPLE_SIZE,
 	EVSEL__CONFIG_TERM_CFG_CHG,
 };
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 6f8b0fa17689..75ebc515faba 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -768,6 +768,7 @@ static const char *config_term_name(enum parse_events__term_type term_type)
 		[PARSE_EVENTS__TERM_TYPE_DRV_CFG]		= "driver-config",
 		[PARSE_EVENTS__TERM_TYPE_PERCORE]		= "percore",
 		[PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT]		= "aux-output",
+		[PARSE_EVENTS__TERM_TYPE_AUX_ACTION]		= "aux-action",
 		[PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE]	= "aux-sample-size",
 		[PARSE_EVENTS__TERM_TYPE_METRIC_ID]		= "metric-id",
 		[PARSE_EVENTS__TERM_TYPE_RAW]                   = "raw",
@@ -817,6 +818,7 @@ config_term_avail(enum parse_events__term_type term_type, struct parse_events_er
 	case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
 	case PARSE_EVENTS__TERM_TYPE_DRV_CFG:
 	case PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT:
+	case PARSE_EVENTS__TERM_TYPE_AUX_ACTION:
 	case PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE:
 	case PARSE_EVENTS__TERM_TYPE_RAW:
 	case PARSE_EVENTS__TERM_TYPE_LEGACY_CACHE:
@@ -936,6 +938,9 @@ do {									   \
 	case PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT:
 		CHECK_TYPE_VAL(NUM);
 		break;
+	case PARSE_EVENTS__TERM_TYPE_AUX_ACTION:
+		CHECK_TYPE_VAL(STR);
+		break;
 	case PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE:
 		CHECK_TYPE_VAL(NUM);
 		if (term->val.num > UINT_MAX) {
@@ -1053,6 +1058,7 @@ static int config_term_tracepoint(struct perf_event_attr *attr,
 	case PARSE_EVENTS__TERM_TYPE_OVERWRITE:
 	case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE:
 	case PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT:
+	case PARSE_EVENTS__TERM_TYPE_AUX_ACTION:
 	case PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE:
 		return config_term_common(attr, term, err);
 	case PARSE_EVENTS__TERM_TYPE_USER:
@@ -1187,6 +1193,9 @@ do {								\
 			ADD_CONFIG_TERM_VAL(AUX_OUTPUT, aux_output,
 					    term->val.num ? 1 : 0, term->weak);
 			break;
+		case PARSE_EVENTS__TERM_TYPE_AUX_ACTION:
+			ADD_CONFIG_TERM_STR(AUX_ACTION, term->val.str, term->weak);
+			break;
 		case PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE:
 			ADD_CONFIG_TERM_VAL(AUX_SAMPLE_SIZE, aux_sample_size,
 					    term->val.num, term->weak);
@@ -1249,6 +1258,7 @@ static int get_config_chgs(struct perf_pmu *pmu, struct parse_events_terms *head
 		case PARSE_EVENTS__TERM_TYPE_DRV_CFG:
 		case PARSE_EVENTS__TERM_TYPE_PERCORE:
 		case PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT:
+		case PARSE_EVENTS__TERM_TYPE_AUX_ACTION:
 		case PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE:
 		case PARSE_EVENTS__TERM_TYPE_METRIC_ID:
 		case PARSE_EVENTS__TERM_TYPE_RAW:
diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index 809359e8544e..7e467ff71f19 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -74,6 +74,7 @@ enum parse_events__term_type {
 	PARSE_EVENTS__TERM_TYPE_DRV_CFG,
 	PARSE_EVENTS__TERM_TYPE_PERCORE,
 	PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT,
+	PARSE_EVENTS__TERM_TYPE_AUX_ACTION,
 	PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE,
 	PARSE_EVENTS__TERM_TYPE_METRIC_ID,
 	PARSE_EVENTS__TERM_TYPE_RAW,
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index e86c45675e1d..26a60ad5853c 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -244,6 +244,7 @@ overwrite		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_OVERWRITE); }
 no-overwrite		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_NOOVERWRITE); }
 percore			{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_PERCORE); }
 aux-output		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT); }
+aux-action		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_AUX_ACTION); }
 aux-sample-size		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE); }
 metric-id		{ return term(yyscanner, PARSE_EVENTS__TERM_TYPE_METRIC_ID); }
 cpu-cycles|cycles				{ return hw_term(yyscanner, PERF_COUNT_HW_CPU_CYCLES); }
-- 
2.34.1

[PATCH V5 08/12] perf tools: Parse aux-action

[Adrian Hunter]

Add parsing for aux-action to accept "pause", "resume" or "start-paused"
values.

"start-paused" is valid only for AUX area events.

"pause" and "resume" are valid only for events grouped with an AUX area
event as the group leader.  However, like with aux-output, the events
will be automatically grouped if they are not currently in a group, and
the AUX area event precedes the other events.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/perf/Documentation/perf-record.txt |  4 ++
 tools/perf/builtin-record.c              |  4 +-
 tools/perf/util/auxtrace.c               | 67 ++++++++++++++++++++++--
 tools/perf/util/auxtrace.h               |  6 ++-
 tools/perf/util/evsel.c                  |  1 +
 5 files changed, 74 insertions(+), 8 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 6015fdd08fb6..ccdba551e52d 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -68,6 +68,10 @@ OPTIONS
 		    like this: name=\'CPU_CLK_UNHALTED.THREAD:cmask=0x1\'.
 	  - 'aux-output': Generate AUX records instead of events. This requires
 			  that an AUX area event is also provided.
+	  - 'aux-action': "pause" or "resume" to pause or resume an AUX
+			  area event (the group leader) when this event occurs.
+			  "start-paused" on an AUX area event itself, will
+			  start in a paused state.
 	  - 'aux-sample-size': Set sample size for AUX area sampling. If the
 	  '--aux-sample' option has been used, set aux-sample-size=0 to disable
 	  AUX area sampling for the event.
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index c310eaad56ce..684a2768cf18 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -850,7 +850,9 @@ static int record__auxtrace_init(struct record *rec)
 	if (err)
 		return err;
 
-	auxtrace_regroup_aux_output(rec->evlist);
+	err = auxtrace_parse_aux_action(rec->evlist);
+	if (err)
+		return err;
 
 	return auxtrace_parse_filters(rec->evlist);
 }
diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
index 3684e6009b63..67bd33ea2eaf 100644
--- a/tools/perf/util/auxtrace.c
+++ b/tools/perf/util/auxtrace.c
@@ -805,19 +805,76 @@ int auxtrace_parse_sample_options(struct auxtrace_record *itr,
 	return auxtrace_validate_aux_sample_size(evlist, opts);
 }
 
-void auxtrace_regroup_aux_output(struct evlist *evlist)
+static struct aux_action_opt {
+	const char *str;
+	u32 aux_action;
+	bool aux_event_opt;
+} aux_action_opts[] = {
+	{"start-paused", BIT(0), true},
+	{"pause",        BIT(1), false},
+	{"resume",       BIT(2), false},
+	{NULL},
+};
+
+static const struct aux_action_opt *auxtrace_parse_aux_action_str(const char *str)
+{
+	const struct aux_action_opt *opt;
+
+	if (!str)
+		return NULL;
+
+	for (opt = aux_action_opts; opt->str; opt++)
+		if (!strcmp(str, opt->str))
+			return opt;
+
+	return NULL;
+}
+
+int auxtrace_parse_aux_action(struct evlist *evlist)
 {
-	struct evsel *evsel, *aux_evsel = NULL;
 	struct evsel_config_term *term;
+	struct evsel *aux_evsel = NULL;
+	struct evsel *evsel;
 
 	evlist__for_each_entry(evlist, evsel) {
-		if (evsel__is_aux_event(evsel))
+		bool is_aux_event = evsel__is_aux_event(evsel);
+		const struct aux_action_opt *opt;
+
+		if (is_aux_event)
 			aux_evsel = evsel;
-		term = evsel__get_config_term(evsel, AUX_OUTPUT);
+		term = evsel__get_config_term(evsel, AUX_ACTION);
+		if (!term) {
+			if (evsel__get_config_term(evsel, AUX_OUTPUT))
+				goto regroup;
+			continue;
+		}
+		opt = auxtrace_parse_aux_action_str(term->val.str);
+		if (!opt) {
+			pr_err("Bad aux-action '%s'\n", term->val.str);
+			return -EINVAL;
+		}
+		if (opt->aux_event_opt && !is_aux_event) {
+			pr_err("aux-action '%s' can only be used with AUX area event\n",
+			       term->val.str);
+			return -EINVAL;
+		}
+		if (!opt->aux_event_opt && is_aux_event) {
+			pr_err("aux-action '%s' cannot be used for AUX area event itself\n",
+			       term->val.str);
+			return -EINVAL;
+		}
+		evsel->core.attr.aux_action = opt->aux_action;
+regroup:
 		/* If possible, group with the AUX event */
-		if (term && aux_evsel)
+		if (aux_evsel)
 			evlist__regroup(evlist, aux_evsel, evsel);
+		if (!evsel__is_aux_event(evsel__leader(evsel))) {
+			pr_err("Events with aux-action must have AUX area event group leader\n");
+			return -EINVAL;
+		}
 	}
+
+	return 0;
 }
 
 struct auxtrace_record *__weak
diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
index 55702215a82d..35324ad12aad 100644
--- a/tools/perf/util/auxtrace.h
+++ b/tools/perf/util/auxtrace.h
@@ -579,7 +579,7 @@ int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
 int auxtrace_parse_sample_options(struct auxtrace_record *itr,
 				  struct evlist *evlist,
 				  struct record_opts *opts, const char *str);
-void auxtrace_regroup_aux_output(struct evlist *evlist);
+int auxtrace_parse_aux_action(struct evlist *evlist);
 int auxtrace_record__options(struct auxtrace_record *itr,
 			     struct evlist *evlist,
 			     struct record_opts *opts);
@@ -800,8 +800,10 @@ int auxtrace_parse_sample_options(struct auxtrace_record *itr __maybe_unused,
 }
 
 static inline
-void auxtrace_regroup_aux_output(struct evlist *evlist __maybe_unused)
+int auxtrace_parse_aux_action(struct evlist *evlist __maybe_unused)
 {
+	pr_err("AUX area tracing not supported\n");
+	return -EINVAL;
 }
 
 static inline
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 866c69f83595..8401685461bf 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1002,6 +1002,7 @@ static void evsel__apply_config_terms(struct evsel *evsel,
 			attr->aux_output = term->val.aux_output ? 1 : 0;
 			break;
 		case EVSEL__CONFIG_TERM_AUX_ACTION:
+			/* Already applied by auxtrace */
 			break;
 		case EVSEL__CONFIG_TERM_AUX_SAMPLE_SIZE:
 			/* Already applied by auxtrace */
-- 
2.34.1

[PATCH V5 09/12] perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume

[Adrian Hunter]

Display "feature is not supported" error message if aux_start_paused,
aux_pause or aux_resume result in a perf_event_open() error.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/evsel.c | 10 +++++++++-
 tools/perf/util/evsel.h |  1 +
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 8401685461bf..9d2fde919604 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1890,7 +1890,13 @@ bool evsel__detect_missing_features(struct evsel *evsel)
 	 * Must probe features in the order they were added to the
 	 * perf_event_attr interface.
 	 */
-	if (!perf_missing_features.branch_counters &&
+	if (!perf_missing_features.aux_pause_resume &&
+	    (evsel->core.attr.aux_pause || evsel->core.attr.aux_resume ||
+	     evsel->core.attr.aux_start_paused)) {
+		perf_missing_features.aux_pause_resume = true;
+		pr_debug2_peo("Kernel has no aux_pause/aux_resume support, bailing out\n");
+		return false;
+	} else if (!perf_missing_features.branch_counters &&
 	    (evsel->core.attr.branch_sample_type & PERF_SAMPLE_BRANCH_COUNTERS)) {
 		perf_missing_features.branch_counters = true;
 		pr_debug2("switching off branch counters support\n");
@@ -3089,6 +3095,8 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
 			return scnprintf(msg, size, "clockid feature not supported.");
 		if (perf_missing_features.clockid_wrong)
 			return scnprintf(msg, size, "wrong clockid (%d).", clockid);
+		if (perf_missing_features.aux_pause_resume)
+			return scnprintf(msg, size, "The 'aux_pause / aux_resume' feature is not supported, update the kernel.");
 		if (perf_missing_features.aux_output)
 			return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
 		if (!target__has_cpu(target))
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 517cff431de2..8ef5a6fdbd45 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -192,6 +192,7 @@ struct perf_missing_features {
 	bool weight_struct;
 	bool read_lost;
 	bool branch_counters;
+	bool aux_pause_resume;
 };
 
 extern struct perf_missing_features perf_missing_features;
-- 
2.34.1

[PATCH V5 10/12] perf intel-pt: Improve man page format

[Adrian Hunter]

Improve format of config terms and section references.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/perf/Documentation/perf-intel-pt.txt | 486 +++++++++++----------
 1 file changed, 267 insertions(+), 219 deletions(-)

diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
index 2109690b0d5f..b5fa7c7ad7f5 100644
--- a/tools/perf/Documentation/perf-intel-pt.txt
+++ b/tools/perf/Documentation/perf-intel-pt.txt
@@ -147,7 +147,7 @@ displayed as follows:
 There are two ways that instructions-per-cycle (IPC) can be calculated depending
 on the recording.
 
-If the 'cyc' config term (see config terms section below) was used, then IPC
+If the 'cyc' config term (see <<_config_terms,config terms>> section below) was used, then IPC
 and cycle events are calculated using the cycle count from CYC packets, otherwise
 MTC packets are used - refer to the 'mtc' config term.  When MTC is used, however,
 the values are less accurate because the timing is less accurate.
@@ -235,7 +235,7 @@ which is the same as
 
 	-e intel_pt/tsc=1,noretcomp=0/
 
-Note there are now new config terms - see section 'config terms' further below.
+Note there are other config terms - see section <<_config_terms,config terms>> further below.
 
 The config terms are listed in /sys/devices/intel_pt/format.  They are bit
 fields within the config member of the struct perf_event_attr which is
@@ -307,217 +307,264 @@ perf_event_attr is displayed if the -vv option is used e.g.
 config terms
 ~~~~~~~~~~~~
 
-The June 2015 version of Intel 64 and IA-32 Architectures Software Developer
-Manuals, Chapter 36 Intel Processor Trace, defined new Intel PT features.
-Some of the features are reflect in new config terms.  All the config terms are
-described below.
-
-tsc		Always supported.  Produces TSC timestamp packets to provide
-		timing information.  In some cases it is possible to decode
-		without timing information, for example a per-thread context
-		that does not overlap executable memory maps.
-
-		The default config selects tsc (i.e. tsc=1).
-
-noretcomp	Always supported.  Disables "return compression" so a TIP packet
-		is produced when a function returns.  Causes more packets to be
-		produced but might make decoding more reliable.
-
-		The default config does not select noretcomp (i.e. noretcomp=0).
-
-psb_period	Allows the frequency of PSB packets to be specified.
-
-		The PSB packet is a synchronization packet that provides a
-		starting point for decoding or recovery from errors.
-
-		Support for psb_period is indicated by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/psb_cyc
-
-		which contains "1" if the feature is supported and "0"
-		otherwise.
-
-		Valid values are given by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/psb_periods
-
-		which contains a hexadecimal value, the bits of which represent
-		valid values e.g. bit 2 set means value 2 is valid.
-
-		The psb_period value is converted to the approximate number of
-		trace bytes between PSB packets as:
-
-			2 ^ (value + 11)
-
-		e.g. value 3 means 16KiB bytes between PSBs
-
-		If an invalid value is entered, the error message
-		will give a list of valid values e.g.
-
-			$ perf record -e intel_pt/psb_period=15/u uname
-			Invalid psb_period for intel_pt. Valid values are: 0-5
-
-		If MTC packets are selected, the default config selects a value
-		of 3 (i.e. psb_period=3) or the nearest lower value that is
-		supported (0 is always supported).  Otherwise the default is 0.
-
-		If decoding is expected to be reliable and the buffer is large
-		then a large PSB period can be used.
-
-		Because a TSC packet is produced with PSB, the PSB period can
-		also affect the granularity to timing information in the absence
-		of MTC or CYC.
-
-mtc		Produces MTC timing packets.
-
-		MTC packets provide finer grain timestamp information than TSC
-		packets.  MTC packets record time using the hardware crystal
-		clock (CTC) which is related to TSC packets using a TMA packet.
-
-		Support for this feature is indicated by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/mtc
-
-		which contains "1" if the feature is supported and
-		"0" otherwise.
-
-		The frequency of MTC packets can also be specified - see
-		mtc_period below.
-
-mtc_period	Specifies how frequently MTC packets are produced - see mtc
-		above for how to determine if MTC packets are supported.
-
-		Valid values are given by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/mtc_periods
-
-		which contains a hexadecimal value, the bits of which represent
-		valid values e.g. bit 2 set means value 2 is valid.
-
-		The mtc_period value is converted to the MTC frequency as:
-
-			CTC-frequency / (2 ^ value)
-
-		e.g. value 3 means one eighth of CTC-frequency
-
-		Where CTC is the hardware crystal clock, the frequency of which
-		can be related to TSC via values provided in cpuid leaf 0x15.
-
-		If an invalid value is entered, the error message
-		will give a list of valid values e.g.
-
-			$ perf record -e intel_pt/mtc_period=15/u uname
-			Invalid mtc_period for intel_pt. Valid values are: 0,3,6,9
-
-		The default value is 3 or the nearest lower value
-		that is supported (0 is always supported).
-
-cyc		Produces CYC timing packets.
-
-		CYC packets provide even finer grain timestamp information than
-		MTC and TSC packets.  A CYC packet contains the number of CPU
-		cycles since the last CYC packet. Unlike MTC and TSC packets,
-		CYC packets are only sent when another packet is also sent.
-
-		Support for this feature is indicated by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/psb_cyc
-
-		which contains "1" if the feature is supported and
-		"0" otherwise.
-
-		The number of CYC packets produced can be reduced by specifying
-		a threshold - see cyc_thresh below.
-
-cyc_thresh	Specifies how frequently CYC packets are produced - see cyc
-		above for how to determine if CYC packets are supported.
-
-		Valid cyc_thresh values are given by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/cycle_thresholds
-
-		which contains a hexadecimal value, the bits of which represent
-		valid values e.g. bit 2 set means value 2 is valid.
-
-		The cyc_thresh value represents the minimum number of CPU cycles
-		that must have passed before a CYC packet can be sent.  The
-		number of CPU cycles is:
-
-			2 ^ (value - 1)
-
-		e.g. value 4 means 8 CPU cycles must pass before a CYC packet
-		can be sent.  Note a CYC packet is still only sent when another
-		packet is sent, not at, e.g. every 8 CPU cycles.
-
-		If an invalid value is entered, the error message
-		will give a list of valid values e.g.
-
-			$ perf record -e intel_pt/cyc,cyc_thresh=15/u uname
-			Invalid cyc_thresh for intel_pt. Valid values are: 0-12
-
-		CYC packets are not requested by default.
-
-pt		Specifies pass-through which enables the 'branch' config term.
-
-		The default config selects 'pt' if it is available, so a user will
-		never need to specify this term.
-
-branch		Enable branch tracing.  Branch tracing is enabled by default so to
-		disable branch tracing use 'branch=0'.
-
-		The default config selects 'branch' if it is available.
-
-ptw		Enable PTWRITE packets which are produced when a ptwrite instruction
-		is executed.
-
-		Support for this feature is indicated by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/ptwrite
-
-		which contains "1" if the feature is supported and
-		"0" otherwise.
-
-		As an alternative, refer to "Emulated PTWRITE" further below.
-
-fup_on_ptw	Enable a FUP packet to follow the PTWRITE packet.  The FUP packet
-		provides the address of the ptwrite instruction.  In the absence of
-		fup_on_ptw, the decoder will use the address of the previous branch
-		if branch tracing is enabled, otherwise the address will be zero.
-		Note that fup_on_ptw will work even when branch tracing is disabled.
-
-pwr_evt		Enable power events.  The power events provide information about
-		changes to the CPU C-state.
-
-		Support for this feature is indicated by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/power_event_trace
-
-		which contains "1" if the feature is supported and
-		"0" otherwise.
-
-event		Enable Event Trace.  The events provide information about asynchronous
-		events.
-
-		Support for this feature is indicated by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/event_trace
-
-		which contains "1" if the feature is supported and
-		"0" otherwise.
-
-notnt		Disable TNT packets.  Without TNT packets, it is not possible to walk
-		executable code to reconstruct control flow, however FUP, TIP, TIP.PGE
-		and TIP.PGD packets still indicate asynchronous control flow, and (if
-		return compression is disabled - see noretcomp) return statements.
-		The advantage of eliminating TNT packets is reducing the size of the
-		trace and corresponding tracing overhead.
-
-		Support for this feature is indicated by:
-
-			/sys/bus/event_source/devices/intel_pt/caps/tnt_disable
-
-		which contains "1" if the feature is supported and
-		"0" otherwise.
+Config terms are parameters specified with the -e intel_pt// event option,
+for example:
+
+	-e intel_pt/cyc/
+
+which selects cycle accurate mode. Each config term can have a value which
+defaults to 1, so the above is the same as:
+
+	-e intel_pt/cyc=1/
+
+Some terms are set by default, so must be set to 0 to turn them off. For
+example, to turn off branch tracing:
+
+	-e intel_pt/branch=0/
+
+Multiple config terms are separated by commas, for example:
+
+	-e intel_pt/cyc,mtc_period=9/
+
+There are also common config terms, see linkperf:perf-record[1] documentation.
+
+Intel PT config terms are described below.
+
+*tsc*::
+Always supported.  Produces TSC timestamp packets to provide
+timing information.  In some cases it is possible to decode
+without timing information, for example a per-thread context
+that does not overlap executable memory maps.
++
+The default config selects tsc (i.e. tsc=1).
+
+*noretcomp*::
+Always supported.  Disables "return compression" so a TIP packet
+is produced when a function returns.  Causes more packets to be
+produced but might make decoding more reliable.
++
+The default config does not select noretcomp (i.e. noretcomp=0).
+
+*psb_period*::
+Allows the frequency of PSB packets to be specified.
++
+The PSB packet is a synchronization packet that provides a
+starting point for decoding or recovery from errors.
++
+Support for psb_period is indicated by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/psb_cyc
++
+which contains "1" if the feature is supported and "0"
+otherwise.
++
+Valid values are given by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/psb_periods
++
+which contains a hexadecimal value, the bits of which represent
+valid values e.g. bit 2 set means value 2 is valid.
++
+The psb_period value is converted to the approximate number of
+trace bytes between PSB packets as:
++
+	2 ^ (value + 11)
++
+e.g. value 3 means 16KiB bytes between PSBs
++
+If an invalid value is entered, the error message
+will give a list of valid values e.g.
++
+	$ perf record -e intel_pt/psb_period=15/u uname
+	Invalid psb_period for intel_pt. Valid values are: 0-5
++
+If MTC packets are selected, the default config selects a value
+of 3 (i.e. psb_period=3) or the nearest lower value that is
+supported (0 is always supported).  Otherwise the default is 0.
++
+If decoding is expected to be reliable and the buffer is large
+then a large PSB period can be used.
++
+Because a TSC packet is produced with PSB, the PSB period can
+also affect the granularity to timing information in the absence
+of MTC or CYC.
+
+*mtc*::
+Produces MTC timing packets.
++
+MTC packets provide finer grain timestamp information than TSC
+packets.  MTC packets record time using the hardware crystal
+clock (CTC) which is related to TSC packets using a TMA packet.
++
+Support for this feature is indicated by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/mtc
++
+which contains "1" if the feature is supported and
+"0" otherwise.
++
+The frequency of MTC packets can also be specified - see
+mtc_period below.
+
+*mtc_period*::
+Specifies how frequently MTC packets are produced - see mtc
+above for how to determine if MTC packets are supported.
++
+Valid values are given by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/mtc_periods
++
+which contains a hexadecimal value, the bits of which represent
+valid values e.g. bit 2 set means value 2 is valid.
++
+The mtc_period value is converted to the MTC frequency as:
+
+	CTC-frequency / (2 ^ value)
++
+e.g. value 3 means one eighth of CTC-frequency
++
+Where CTC is the hardware crystal clock, the frequency of which
+can be related to TSC via values provided in cpuid leaf 0x15.
++
+If an invalid value is entered, the error message
+will give a list of valid values e.g.
++
+	$ perf record -e intel_pt/mtc_period=15/u uname
+	Invalid mtc_period for intel_pt. Valid values are: 0,3,6,9
++
+The default value is 3 or the nearest lower value
+that is supported (0 is always supported).
+
+*cyc*::
+Produces CYC timing packets.
++
+CYC packets provide even finer grain timestamp information than
+MTC and TSC packets.  A CYC packet contains the number of CPU
+cycles since the last CYC packet. Unlike MTC and TSC packets,
+CYC packets are only sent when another packet is also sent.
++
+Support for this feature is indicated by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/psb_cyc
++
+which contains "1" if the feature is supported and
+"0" otherwise.
++
+The number of CYC packets produced can be reduced by specifying
+a threshold - see cyc_thresh below.
+
+*cyc_thresh*::
+Specifies how frequently CYC packets are produced - see cyc
+above for how to determine if CYC packets are supported.
++
+Valid cyc_thresh values are given by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/cycle_thresholds
++
+which contains a hexadecimal value, the bits of which represent
+valid values e.g. bit 2 set means value 2 is valid.
++
+The cyc_thresh value represents the minimum number of CPU cycles
+that must have passed before a CYC packet can be sent.  The
+number of CPU cycles is:
++
+	2 ^ (value - 1)
++
+e.g. value 4 means 8 CPU cycles must pass before a CYC packet
+can be sent.  Note a CYC packet is still only sent when another
+packet is sent, not at, e.g. every 8 CPU cycles.
++
+If an invalid value is entered, the error message
+will give a list of valid values e.g.
++
+	$ perf record -e intel_pt/cyc,cyc_thresh=15/u uname
+	Invalid cyc_thresh for intel_pt. Valid values are: 0-12
++
+CYC packets are not requested by default.
+
+*pt*::
+Specifies pass-through which enables the 'branch' config term.
++
+The default config selects 'pt' if it is available, so a user will
+never need to specify this term.
+
+*branch*::
+Enable branch tracing.  Branch tracing is enabled by default so to
+disable branch tracing use 'branch=0'.
++
+The default config selects 'branch' if it is available.
+
+*ptw*::
+Enable PTWRITE packets which are produced when a ptwrite instruction
+is executed.
++
+Support for this feature is indicated by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/ptwrite
++
+which contains "1" if the feature is supported and
+"0" otherwise.
++
+As an alternative, refer to "Emulated PTWRITE" further below.
+
+*fup_on_ptw*::
+Enable a FUP packet to follow the PTWRITE packet.  The FUP packet
+provides the address of the ptwrite instruction.  In the absence of
+fup_on_ptw, the decoder will use the address of the previous branch
+if branch tracing is enabled, otherwise the address will be zero.
+Note that fup_on_ptw will work even when branch tracing is disabled.
+
+*pwr_evt*::
+Enable power events.  The power events provide information about
+changes to the CPU C-state.
++
+Support for this feature is indicated by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/power_event_trace
++
+which contains "1" if the feature is supported and
+"0" otherwise.
+
+*event*::
+Enable Event Trace.  The events provide information about asynchronous
+events.
++
+Support for this feature is indicated by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/event_trace
++
+which contains "1" if the feature is supported and
+"0" otherwise.
+
+*notnt*::
+Disable TNT packets.  Without TNT packets, it is not possible to walk
+executable code to reconstruct control flow, however FUP, TIP, TIP.PGE
+and TIP.PGD packets still indicate asynchronous control flow, and (if
+return compression is disabled - see noretcomp) return statements.
+The advantage of eliminating TNT packets is reducing the size of the
+trace and corresponding tracing overhead.
++
+Support for this feature is indicated by:
++
+	/sys/bus/event_source/devices/intel_pt/caps/tnt_disable
++
+which contains "1" if the feature is supported and
+"0" otherwise.
+
+
+config terms on other events
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Some Intel PT features work with other events, features such as AUX area sampling
+and PEBS-via-PT.  In those cases, the other events can have config terms below:
+
+*aux-sample-size*::
+		Used to set the AUX area sample size, refer to the section
+		<<_aux_area_sampling_option,AUX area sampling option>>
+
+*aux-output*::
+		Used to select PEBS-via-PT, refer to the
+		section <<_pebs_via_intel_pt,PEBS via Intel PT>>
 
 
 AUX area sampling option
@@ -592,7 +639,8 @@ The default snapshot size is the auxtrace mmap size.  If neither auxtrace mmap s
 nor snapshot size is specified, then the default is 4MiB for privileged users
 (or if /proc/sys/kernel/perf_event_paranoid < 0), 128KiB for unprivileged users.
 If an unprivileged user does not specify mmap pages, the mmap pages will be
-reduced as described in the 'new auxtrace mmap size option' section below.
+reduced as described in the <<_new_auxtrace_mmap_size_option,new auxtrace mmap size option>>
+section below.
 
 The snapshot size is displayed if the option -vv is used e.g.
 
@@ -948,11 +996,11 @@ transaction start, commit or abort.
 
 Note that "instructions", "cycles", "branches" and "transactions" events
 depend on code flow packets which can be disabled by using the config term
-"branch=0".  Refer to the config terms section above.
+"branch=0".  Refer to the <<_config_terms,config terms>> section above.
 
 "ptwrite" events record the payload of the ptwrite instruction and whether
 "fup_on_ptw" was used.  "ptwrite" events depend on PTWRITE packets which are
-recorded only if the "ptw" config term was used.  Refer to the config terms
+recorded only if the "ptw" config term was used.  Refer to the <<_config_terms,config terms>>
 section above.  perf script "synth" field displays "ptwrite" information like
 this: "ip: 0 payload: 0x123456789abcdef0"  where "ip" is 1 if "fup_on_ptw" was
 used.
@@ -960,7 +1008,7 @@ used.
 "Power" events correspond to power event packets and CBR (core-to-bus ratio)
 packets.  While CBR packets are always recorded when tracing is enabled, power
 event packets are recorded only if the "pwr_evt" config term was used.  Refer to
-the config terms section above.  The power events record information about
+the <<_config_terms,config terms>> section above.  The power events record information about
 C-state changes, whereas CBR is indicative of CPU frequency.  perf script
 "event,synth" fields display information like this:
 
@@ -1116,7 +1164,7 @@ What *will* be decoded with the (single) q option:
 	- asynchronous branches such as interrupts
 	- indirect branches
 	- function return target address *if* the noretcomp config term (refer
-	config terms section) was used
+	<<_config_terms,config terms>> section) was used
 	- start of (control-flow) tracing
 	- end of (control-flow) tracing, if it is not out of context
 	- power events, ptwrite, transaction start and abort
@@ -1129,7 +1177,7 @@ Repeating the q option (double-q i.e. qq) results in even faster decoding and ev
 less detail.  The decoder decodes only extended PSB (PSB+) packets, getting the
 instruction pointer if there is a FUP packet within PSB+ (i.e. between PSB and
 PSBEND).  Note PSB packets occur regularly in the trace based on the psb_period
-config term (refer config terms section).  There will be a FUP packet if the
+config term (refer <<_config_terms,config terms>> section).  There will be a FUP packet if the
 PSB+ occurs while control flow is being traced.
 
 What will *not* be decoded with the qq option:
-- 
2.34.1

[PATCH V5 11/12] perf intel-pt: Add documentation for pause / resume

[Adrian Hunter]

Document the use of aux-action config term and provide a simple example.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---


Changes in V5:
	Added more examples


 tools/perf/Documentation/perf-intel-pt.txt | 108 +++++++++++++++++++++
 1 file changed, 108 insertions(+)

diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
index b5fa7c7ad7f5..c86deae170e4 100644
--- a/tools/perf/Documentation/perf-intel-pt.txt
+++ b/tools/perf/Documentation/perf-intel-pt.txt
@@ -551,6 +551,9 @@ Support for this feature is indicated by:
 which contains "1" if the feature is supported and
 "0" otherwise.
 
+*aux-action=start-paused*::
+Start tracing paused, refer to the section <<_pause_or_resume_tracing,Pause or Resume Tracing>>
+
 
 config terms on other events
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -566,6 +569,9 @@ and PEBS-via-PT.  In those cases, the other events can have config terms below:
 		Used to select PEBS-via-PT, refer to the
 		section <<_pebs_via_intel_pt,PEBS via Intel PT>>
 
+*aux-action*::
+		Used to pause or resume tracing, refer to the section
+		<<_pause_or_resume_tracing,Pause or Resume Tracing>>
 
 AUX area sampling option
 ~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1911,6 +1917,108 @@ For pipe mode, the order of events and timestamps can presumably
 be messed up.
 
 
+Pause or Resume Tracing
+-----------------------
+
+With newer Kernels, it is possible to use other selected events to pause
+or resume Intel PT tracing.  This is configured by using the "aux-action"
+config term:
+
+"aux-action=pause" is used with events that are to pause Intel PT tracing.
+
+"aux-action=resume" is used with events that are to resume Intel PT tracing.
+
+"aux-action=start-paused" is used with the Intel PT event to start in a
+paused state.
+
+For example, to trace only the uname system call (sys_newuname) when running the
+command line utility uname:
+
+ $ 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
+
+The example above uses tracepoints, but any kind of sampled event can be used.
+
+For example:
+
+ Tracing between arch_cpu_idle_enter() and arch_cpu_idle_exit() using breakpoint events:
+
+ $ sudo cat /proc/kallsyms | sort | grep ' arch_cpu_idle_enter\| arch_cpu_idle_exit'
+ ffffffffb605bf60 T arch_cpu_idle_enter
+ ffffffffb614d8a0 W arch_cpu_idle_exit
+ $ sudo perf record --kcore -a -e intel_pt/aux-action=start-paused/k -e mem:0xffffffffb605bf60:x/aux-action=resume/ -e mem:0xffffffffb614d8a0:x/aux-action=pause/ -- sleep 1
+ [ perf record: Woken up 1 times to write data ]
+ [ perf record: Captured and wrote 1.387 MB perf.data ]
+
+ Tracing __alloc_pages() using kprobes:
+
+ $ sudo perf probe --add '__alloc_pages order'
+ Added new event:  probe:__alloc_pages  (on __alloc_pages with order)
+ $ sudo perf probe --add __alloc_pages%return
+ Added new event:  probe:__alloc_pages__return (on __alloc_pages%return)
+ $ sudo perf record --kcore -aR -e intel_pt/aux-action=start-paused/k -e probe:__alloc_pages/aux-action=resume/ -e probe:__alloc_pages__return/aux-action=pause/ -- sleep 1
+ [ perf record: Woken up 1 times to write data ]
+ [ perf record: Captured and wrote 1.490 MB perf.data ]
+
+ Tracing starting at main() using a uprobe event:
+
+ $ sudo perf probe -x /usr/bin/uname main
+ Added new event:  probe_uname:main     (on main in /usr/bin/uname)
+ $ sudo perf record -e intel_pt/-aux-action=start-paused/u -e probe_uname:main/aux-action=resume/ -- uname
+ Linux
+ [ perf record: Woken up 1 times to write data ]
+ [ perf record: Captured and wrote 0.031 MB perf.data ]
+
+ Tracing occassionally using cycles events with different periods:
+
+ $ perf record --kcore -a -m,64M -e intel_pt/aux-action=start-paused/k -e cycles/aux-action=pause,period=1000000/Pk -e cycles/aux-action=resume,period=10500000/Pk -- firefox
+ [ perf record: Woken up 19 times to write data ]
+ [ perf record: Captured and wrote 16.561 MB perf.data ]
+
+
 EXAMPLE
 -------
 
-- 
2.34.1

[PATCH V5 12/12] perf intel-pt: Add a test for pause / resume

[Adrian Hunter]

Add a simple sub-test to the "Miscellaneous Intel PT testing" test to
check pause / resume.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---
 tools/perf/tests/shell/test_intel_pt.sh | 28 +++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tools/perf/tests/shell/test_intel_pt.sh b/tools/perf/tests/shell/test_intel_pt.sh
index 723ec501f99a..e359db0d0ff2 100755
--- a/tools/perf/tests/shell/test_intel_pt.sh
+++ b/tools/perf/tests/shell/test_intel_pt.sh
@@ -644,6 +644,33 @@ test_pipe()
 	return 0
 }
 
+test_pause_resume()
+{
+	echo "--- Test with pause / resume ---"
+	if ! perf_record_no_decode -o "${perfdatafile}" -e intel_pt/aux-action=start-paused/u uname ; then
+		echo "SKIP: pause / resume is not supported"
+		return 2
+	fi
+	if ! perf_record_no_bpf -o "${perfdatafile}" \
+			-e intel_pt/aux-action=start-paused/u \
+			-e instructions/period=50000,aux-action=resume,name=Resume/u \
+			-e instructions/period=100000,aux-action=pause,name=Pause/u uname  ; then
+		echo "perf record with pause / resume failed"
+		return 1
+	fi
+	if ! perf script -i "${perfdatafile}" --itrace=b -Fperiod,event | \
+			awk 'BEGIN {paused=1;branches=0}
+			     /Resume/ {paused=0}
+			     /branches/ {if (paused) exit 1;branches=1}
+			     /Pause/ {paused=1}
+			     END {if (!branches) exit 1}' ; then
+		echo "perf record with pause / resume failed"
+		return 1
+	fi
+	echo OK
+	return 0
+}
+
 count_result()
 {
 	if [ "$1" -eq 2 ] ; then
@@ -672,6 +699,7 @@ test_power_event			|| ret=$? ; count_result $ret ; ret=0
 test_no_tnt				|| ret=$? ; count_result $ret ; ret=0
 test_event_trace			|| ret=$? ; count_result $ret ; ret=0
 test_pipe				|| ret=$? ; count_result $ret ; ret=0
+test_pause_resume			|| ret=$? ; count_result $ret ; ret=0
 
 cleanup
 
-- 
2.34.1

Re: [PATCH V5 01/12] perf/core: Add aux_pause, aux_resume, aux_start_paused

[Andi Kleen]

> +static void __perf_event_aux_pause(struct perf_event *event, bool pause)
> +{
> +	if (pause) {
> +		if (!READ_ONCE(event->aux_paused)) {
> +			WRITE_ONCE(event->aux_paused, 1);
> +			event->pmu->stop(event, PERF_EF_PAUSE);
> +		}
> +	} else {
> +		if (READ_ONCE(event->aux_paused)) {
> +			WRITE_ONCE(event->aux_paused, 0);
> +			event->pmu->start(event, PERF_EF_RESUME);
> +		}

This doesn't look atomic. Either the READ/WRITE once are not needed,
or you need an actually atomic construct.

> +
> +	rb = ring_buffer_get(event);
> +	if (!rb)
> +		return;
> +
> +	local_irq_save(flags);
> +	/* Guard against NMI, NMI loses here */
> +	if (READ_ONCE(rb->aux_in_pause_resume))
> +		goto out_restore;
> +	WRITE_ONCE(rb->aux_in_pause_resume, 1);


> +	barrier();
> +	__perf_event_aux_pause(event, pause);
> +	barrier();
> +	WRITE_ONCE(rb->aux_in_pause_resume, 0);

Dito.

-Andi

Re: [PATCH V5 12/12] perf intel-pt: Add a test for pause / resume

[Andi Kleen]

For Patch 2-12:

Reviewed-by: Andi Kleen <ak@linux.intel.com>

Re: [PATCH V5 01/12] perf/core: Add aux_pause, aux_resume, aux_start_paused

[Adrian Hunter]

On 9/02/24 02:13, Andi Kleen wrote:
>> +static void __perf_event_aux_pause(struct perf_event *event, bool pause)
>> +{
>> +	if (pause) {
>> +		if (!READ_ONCE(event->aux_paused)) {
>> +			WRITE_ONCE(event->aux_paused, 1);
>> +			event->pmu->stop(event, PERF_EF_PAUSE);
>> +		}
>> +	} else {
>> +		if (READ_ONCE(event->aux_paused)) {
>> +			WRITE_ONCE(event->aux_paused, 0);
>> +			event->pmu->start(event, PERF_EF_RESUME);
>> +		}
> 
> This doesn't look atomic. Either the READ/WRITE once are not needed,
> or you need an actually atomic construct.

Yes READ_ONCE / WRITE_ONCE is not really needed here.

> 
>> +
>> +	rb = ring_buffer_get(event);
>> +	if (!rb)
>> +		return;
>> +
>> +	local_irq_save(flags);
>> +	/* Guard against NMI, NMI loses here */
>> +	if (READ_ONCE(rb->aux_in_pause_resume))
>> +		goto out_restore;
>> +	WRITE_ONCE(rb->aux_in_pause_resume, 1);
> 
> 
>> +	barrier();
>> +	__perf_event_aux_pause(event, pause);
>> +	barrier();
>> +	WRITE_ONCE(rb->aux_in_pause_resume, 0);
> 
> Dito.
> 

The writes to rb->aux_in_pause_resume must be done
only once.  It might be possible to get away without
WRITE_ONCE(), but really the compiler should be informed
not to make assumptions.

Re: [PATCH V5 01/12] perf/core: Add aux_pause, aux_resume, aux_start_paused

[Andi Kleen]

On Fri, Feb 09, 2024 at 10:14:44AM +0200, Adrian Hunter wrote:
> On 9/02/24 02:13, Andi Kleen wrote:
> >> +static void __perf_event_aux_pause(struct perf_event *event, bool pause)
> >> +{
> >> +	if (pause) {
> >> +		if (!READ_ONCE(event->aux_paused)) {
> >> +			WRITE_ONCE(event->aux_paused, 1);
> >> +			event->pmu->stop(event, PERF_EF_PAUSE);
> >> +		}
> >> +	} else {
> >> +		if (READ_ONCE(event->aux_paused)) {
> >> +			WRITE_ONCE(event->aux_paused, 0);
> >> +			event->pmu->start(event, PERF_EF_RESUME);
> >> +		}
> > 
> > This doesn't look atomic. Either the READ/WRITE once are not needed,
> > or you need an actually atomic construct.
> 
> Yes READ_ONCE / WRITE_ONCE is not really needed here.

Normally you are supposed to add a comment on what the interaction
is (similar to what is done for spinlock declarations)

-Andi

Re: [PATCH V5 01/12] perf/core: Add aux_pause, aux_resume, aux_start_paused

[Andi Kleen]

> The writes to rb->aux_in_pause_resume must be done
> only once.  It might be possible to get away without
> WRITE_ONCE(), but really the compiler should be informed
> not to make assumptions.

What stops the NMI from firing here?

> >> +  if (READ_ONCE(rb->aux_in_pause_resume))
> >> +	/* Guard against NMI, NMI loses here */
> >> +          goto out_restore;
<----------------------- NMI
> >> +  WRITE_ONCE(rb->aux_in_pause_resume, 1);


Even if it isn't racy it needs a clear comment.

-Andi

Re: [PATCH V5 01/12] perf/core: Add aux_pause, aux_resume, aux_start_paused

[Adrian Hunter]

On 9/02/24 23:10, Andi Kleen wrote:
>> The writes to rb->aux_in_pause_resume must be done
>> only once.  It might be possible to get away without
>> WRITE_ONCE(), but really the compiler should be informed
>> not to make assumptions.
> 
> What stops the NMI from firing here?

That would be fine.

> 
>>>> +  if (READ_ONCE(rb->aux_in_pause_resume))
>>>> +	/* Guard against NMI, NMI loses here */
>>>> +          goto out_restore;
> <----------------------- NMI

That would be fine.

>>>> +  WRITE_ONCE(rb->aux_in_pause_resume, 1);

From here on, the NMI will see rb->aux_in_pause_resume == 1
and do nothing, up to the point when rb->aux_in_pause_resume == 0
again.

This code is about guarding against NMI.  Interrupts are
disabled, and the rb and event only operate on 1 cpu at a time.

> 
> 
> Even if it isn't racy it needs a clear comment.

It has a comment, but it could be more explanatory.  The code
paradigm is also used in perf_pmu_snapshot_aux().

[PATCH V6] perf/core: Add aux_pause, aux_resume, aux_start_paused

[Adrian Hunter]

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 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>
Acked-by: James Clark <james.clark@arm.com>
---


Changes in V6:
	Removed READ/WRITE_ONCEfrom __perf_event_aux_pause()
	Expanded comment about guarding against NMI

Changes in V5:
	Added James' Ack

Changes in V4:
	Rename aux_output_cfg -> aux_action
	Reorder aux_action bits from:
		aux_pause, aux_resume, aux_start_paused
	to:
		aux_start_paused, aux_pause, aux_resume
	Fix aux_action bits __u64 -> __u32


 include/linux/perf_event.h      | 15 +++++++
 include/uapi/linux/perf_event.h | 11 ++++-
 kernel/events/core.c            | 76 +++++++++++++++++++++++++++++++--
 kernel/events/internal.h        |  1 +
 4 files changed, 99 insertions(+), 4 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0c6f8a..6c1600b9bdb3 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -291,6 +291,7 @@ 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
 
 struct perf_output_handle;
 
@@ -363,6 +364,8 @@ 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
@@ -402,6 +405,15 @@ 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.
 	 */
 	void (*start)			(struct perf_event *event, int flags);
 	void (*stop)			(struct perf_event *event, int flags);
@@ -798,6 +810,9 @@ struct perf_event {
 	/* for aux_output events */
 	struct perf_event		*aux_event;
 
+	/* for AUX area events */
+	unsigned int			aux_paused;
+
 	void (*destroy)(struct perf_event *);
 	struct rcu_head			rcu_head;
 
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 3a64499b0f5d..0c557f0a17b3 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 f0f0f71213a1..c7ed4e64f1d8 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2097,7 +2097,8 @@ 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 || event->attr.aux_sample_size ||
+	       event->attr.aux_pause || event->attr.aux_resume;
 }
 
 static int perf_get_aux_event(struct perf_event *event,
@@ -2122,6 +2123,10 @@ 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;
 
@@ -7854,6 +7859,51 @@ 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->aux_paused) {
+			event->aux_paused = 1;
+			event->pmu->stop(event, PERF_EF_PAUSE);
+		}
+	} else {
+		if (event->aux_paused) {
+			event->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;
+	unsigned long flags;
+
+	if (WARN_ON_ONCE(!event))
+		return;
+
+	rb = ring_buffer_get(event);
+	if (!rb)
+		return;
+
+	local_irq_save(flags);
+	/*
+	 * Guard against NMI, NMI loses here. The critical setion is demarked by
+	 * rb->aux_in_pause_resume == 1. An NMI in the critical section will not
+	 * process a pause/resume.
+	 */
+	if (READ_ONCE(rb->aux_in_pause_resume))
+		goto out_restore;
+	WRITE_ONCE(rb->aux_in_pause_resume, 1);
+	barrier();
+	__perf_event_aux_pause(event, pause);
+	barrier();
+	WRITE_ONCE(rb->aux_in_pause_resume, 0);
+out_restore:
+	local_irq_restore(flags);
+	ring_buffer_put(rb);
+}
+
 static __always_inline int
 __perf_event_output(struct perf_event *event,
 		    struct perf_sample_data *data,
@@ -7867,6 +7917,9 @@ __perf_event_output(struct perf_event *event,
 	struct perf_event_header header;
 	int err;
 
+	if (event->attr.aux_pause)
+		perf_event_aux_pause(event->aux_event, true);
+
 	/* protect the callchain buffers */
 	rcu_read_lock();
 
@@ -7883,6 +7936,10 @@ __perf_event_output(struct perf_event *event,
 
 exit:
 	rcu_read_unlock();
+
+	if (event->attr.aux_resume)
+		perf_event_aux_pause(event->aux_event, false);
+
 	return err;
 }
 
@@ -12036,10 +12093,23 @@ 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 &&
+	    !(pmu->capabilities & PERF_PMU_CAP_AUX_PAUSE)) {
 		err = -EOPNOTSUPP;
 		goto err_pmu;
 	}
+	event->aux_paused = event->attr.aux_start_paused;
 
 	if (cgroup_fd != -1) {
 		err = perf_cgroup_connect(cgroup_fd, event, attr, group_leader);
@@ -12836,7 +12906,7 @@ 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 5150d5f84c03..3320f78117dc 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -51,6 +51,7 @@ 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;
 
-- 
2.34.1

Re: [PATCH V5 00/12] perf/core: Add ability for an event to "pause" or "resume" AUX area tracing

[Adrian Hunter]

On 8/02/24 13:31, Adrian Hunter wrote:
> Hi
> 
> 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.
> 
> These patches add such a facilty and show how it would work for Intel
> Processor Trace.
> 
> Maintainers of other AUX area tracing implementations are requested to
> consider if this is something they might employ and then whether or not
> the ABI would work for them.  Note, thank you to James Clark (ARM) for
> evaluating the API for Coresight.  Suzuki K Poulose (ARM) also responded
> positively to the RFC.
> 
> Changes to perf tools are now (since V4) fleshed out.
> 
> 
> Changes in V5:
> 
>     perf/core: Add aux_pause, aux_resume, aux_start_paused
> 	Added James' Ack
> 
>     perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
> 	New patch
> 
>     perf tools
> 	Added Ian's Ack
> 
> Changes in V4:
> 
>     perf/core: Add aux_pause, aux_resume, aux_start_paused
> 	Rename aux_output_cfg -> aux_action
> 	Reorder aux_action bits from:
> 		aux_pause, aux_resume, aux_start_paused
> 	to:
> 		aux_start_paused, aux_pause, aux_resume
> 	Fix aux_action bits __u64 -> __u32
> 
>     coresight: Have a stab at support for pause / resume
> 	Dropped
> 
>     perf tools
> 	All new patches
> 
> Changes in RFC V3:
> 
>     coresight: Have a stab at support for pause / resume
> 	'mode' -> 'flags' so it at least compiles
> 
> Changes in RFC V2:
> 
> 	Use ->stop() / ->start() instead of ->pause_resume()
> 	Move aux_start_paused bit into aux_output_cfg
> 	Tighten up when Intel PT pause / resume is allowed
> 	Add an example of how it might work for CoreSight

Any more comments?

Re: [PATCH V5 00/12] perf/core: Add ability for an event to "pause" or "resume" AUX area tracing

[Adrian Hunter]

On 11/04/24 15:02, Adrian Hunter wrote:
> On 8/02/24 13:31, Adrian Hunter wrote:
>> Hi
>>
>> 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.
>>
>> These patches add such a facilty and show how it would work for Intel
>> Processor Trace.
>>
>> Maintainers of other AUX area tracing implementations are requested to
>> consider if this is something they might employ and then whether or not
>> the ABI would work for them.  Note, thank you to James Clark (ARM) for
>> evaluating the API for Coresight.  Suzuki K Poulose (ARM) also responded
>> positively to the RFC.
>>
>> Changes to perf tools are now (since V4) fleshed out.
>>
>>
>> Changes in V5:
>>
>>     perf/core: Add aux_pause, aux_resume, aux_start_paused
>> 	Added James' Ack
>>
>>     perf/x86/intel: Do not enable large PEBS for events with aux actions or aux sampling
>> 	New patch
>>
>>     perf tools
>> 	Added Ian's Ack
>>
>> Changes in V4:
>>
>>     perf/core: Add aux_pause, aux_resume, aux_start_paused
>> 	Rename aux_output_cfg -> aux_action
>> 	Reorder aux_action bits from:
>> 		aux_pause, aux_resume, aux_start_paused
>> 	to:
>> 		aux_start_paused, aux_pause, aux_resume
>> 	Fix aux_action bits __u64 -> __u32
>>
>>     coresight: Have a stab at support for pause / resume
>> 	Dropped
>>
>>     perf tools
>> 	All new patches
>>
>> Changes in RFC V3:
>>
>>     coresight: Have a stab at support for pause / resume
>> 	'mode' -> 'flags' so it at least compiles
>>
>> Changes in RFC V2:
>>
>> 	Use ->stop() / ->start() instead of ->pause_resume()
>> 	Move aux_start_paused bit into aux_output_cfg
>> 	Tighten up when Intel PT pause / resume is allowed
>> 	Add an example of how it might work for CoreSight
> 
> Any more comments?
> 

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