Patch "perf pmu: Unbreak perf record for arm/arm64 with events with explicit PMU" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

perf pmu: Unbreak perf record for arm/arm64 with events with explicit PMU

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-pmu-unbreak-perf-record-for-arm-arm64-with-events-with-explicit-pmu.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mark Rutland <[email protected]>
Date: Fri, 6 Oct 2017 19:38:22 +0100
Subject: perf pmu: Unbreak perf record for arm/arm64 with events with explicit PMU

From: Mark Rutland <[email protected]>

commit 66ec11919a0f96e936bb731fdbc2851316077d26 upstream.

Currently, perf record is broken on arm/arm64 systems when the PMU is specified explicitly as part of the event, e.g.

$ ./perf record -e armv8_cortex_a53/cpu_cycles/u true

In such cases, perf record fails to open events unless perf_event_paranoid is set to -1, even if the PMU in question supports mode exclusion. Further, even when perf_event_paranoid is toggled, no samples are recorded.

This is an unintended side effect of commit:

e3ba76deef23064f ("perf tools: Force uncore events to system wide monitoring)

... which assumes that if a PMU has an associated cpu_map, it is an uncore PMU, and forces events for such PMUs to be system-wide.

This is not true for arm/arm64 systems, which can have heterogeneous CPUs. To account for this, multiple CPU PMUs are exposed, each with a "cpus" field under sysfs, which the perf tool parses into a cpu_map. ARM PMUs do not have a "cpumask" file, and only have a "cpus" file. For the gory details as to why, see commit:

7e3fcffe95544010 ("perf pmu: Support alternative sysfs cpumask")

Given all of this, we can instead identify uncore PMUs by explicitly checking for a "cpumask" file, and restore arm/arm64 PMU support back to a working state. This patch does so, adding a new perf_pmu::is_uncore field, and splitting the existing cpumask parsing so that it can be reused.

Tested-by Will Deacon <[email protected]>

---
 tools/perf/util/parse-events.c |    9 +++---
 tools/perf/util/pmu.c          |   56 ++++++++++++++++++++++++++++++-----------
 tools/perf/util/pmu.h          |    1 
 3 files changed, 47 insertions(+), 19 deletions(-)

@@ -309,10 +309,11 @@ static char *get_config_name(struct list
 static struct perf_evsel *
 __add_event(struct list_head *list, int *idx,
 	    struct perf_event_attr *attr,
-	    char *name, struct cpu_map *cpus,
+	    char *name, struct perf_pmu *pmu,
 	    struct list_head *config_terms)
 {
 	struct perf_evsel *evsel;
+	struct cpu_map *cpus = pmu ? pmu->cpus : NULL;
 
 	event_attr_init(attr);
 

@@ -323,7 +324,7 @@ __add_event(struct list_head *list, int
 	(*idx)++;
 	evsel->cpus        = cpu_map__get(cpus);
 	evsel->own_cpus    = cpu_map__get(cpus);
-	evsel->system_wide = !!cpus;
+	evsel->system_wide = pmu ? pmu->is_uncore : false;
 
 	if (name)
 		evsel->name = strdup(name);

@@ -1232,7 +1233,7 @@ int parse_events_add_pmu(struct parse_ev
 
 	if (!head_config) {
 		attr.type = pmu->type;
-		evsel = __add_event(list, &data->idx, &attr, NULL, pmu->cpus, NULL);
+		evsel = __add_event(list, &data->idx, &attr, NULL, pmu, NULL);
 		return evsel ? 0 : -ENOMEM;
 	}
 

@@ -1253,7 +1254,7 @@ int parse_events_add_pmu(struct parse_ev
 		return -EINVAL;
 
 	evsel = __add_event(list, &data->idx, &attr,
-			    get_config_name(head_config), pmu->cpus,
+			    get_config_name(head_config), pmu,
 			    &config_terms);
 	if (evsel) {
 		evsel->unit = info.unit;

@@ -22,6 +22,7 @@ struct perf_pmu {
 	char *name;
 	__u32 type;
 	bool selectable;
+	bool is_uncore;
 	struct perf_event_attr *default_config;
 	struct cpu_map *cpus;
 	struct list_head format;  /* HEAD struct perf_pmu_format -> list */

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/perf-pmu-unbreak-perf-record-for-arm-arm64-with-events-with-explicit-pmu.patch