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Subject[PATCH] perf tools: unbreak perf record for arm/arm64
Date
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.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Fixes: e3ba76deef23064f ("perf tools: Force uncore events to system wide monitoring)
Cc: stable@vger.kernel.org
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Will Deacon <will.deacon@arm.com>
---
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(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index f6257fb..39b1596 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -309,10 +309,11 @@ static char *get_config_name(struct list_head *head_terms)
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, bool auto_merge_stats)
{
struct perf_evsel *evsel;
+ struct cpu_map *cpus = pmu ? pmu->cpus : NULL;

event_attr_init(attr);

@@ -323,7 +324,7 @@ static char *get_config_name(struct list_head *head_terms)
(*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;
evsel->auto_merge_stats = auto_merge_stats;

if (name)
@@ -1233,7 +1234,7 @@ static int __parse_events_add_pmu(struct parse_events_state *parse_state,

if (!head_config) {
attr.type = pmu->type;
- evsel = __add_event(list, &parse_state->idx, &attr, NULL, pmu->cpus, NULL, auto_merge_stats);
+ evsel = __add_event(list, &parse_state->idx, &attr, NULL, pmu, NULL, auto_merge_stats);
return evsel ? 0 : -ENOMEM;
}

@@ -1254,7 +1255,7 @@ static int __parse_events_add_pmu(struct parse_events_state *parse_state,
return -EINVAL;

evsel = __add_event(list, &parse_state->idx, &attr,
- get_config_name(head_config), pmu->cpus,
+ get_config_name(head_config), pmu,
&config_terms, auto_merge_stats);
if (evsel) {
evsel->unit = info.unit;
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index ac16a9d..1c4d7b4 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -470,17 +470,36 @@ static void pmu_read_sysfs(void)
closedir(dir);
}

+static struct cpu_map *__pmu_cpumask(const char *path)
+{
+ FILE *file;
+ struct cpu_map *cpus;
+
+ file = fopen(path, "r");
+ if (!file)
+ return NULL;
+
+ cpus = cpu_map__read(file);
+ fclose(file);
+ return cpus;
+}
+
+/*
+ * Uncore PMUs have a "cpumask" file under sysfs. CPU PMUs (e.g. on arm/arm64)
+ * may have a "cpus" file.
+ */
+#define CPUS_TEMPLATE_UNCORE "%s/bus/event_source/devices/%s/cpumask"
+#define CPUS_TEMPLATE_CPU "%s/bus/event_source/devices/%s/cpus"
+
static struct cpu_map *pmu_cpumask(const char *name)
{
- struct stat st;
char path[PATH_MAX];
- FILE *file;
struct cpu_map *cpus;
const char *sysfs = sysfs__mountpoint();
const char *templates[] = {
- "%s/bus/event_source/devices/%s/cpumask",
- "%s/bus/event_source/devices/%s/cpus",
- NULL
+ CPUS_TEMPLATE_UNCORE,
+ CPUS_TEMPLATE_CPU,
+ NULL
};
const char **template;

@@ -489,20 +508,25 @@ static struct cpu_map *pmu_cpumask(const char *name)

for (template = templates; *template; template++) {
snprintf(path, PATH_MAX, *template, sysfs, name);
- if (stat(path, &st) == 0)
- break;
+ cpus = __pmu_cpumask(path);
+ if (cpus)
+ return cpus;
}

- if (!*template)
- return NULL;
+ return NULL;
+}

- file = fopen(path, "r");
- if (!file)
- return NULL;
+static bool pmu_is_uncore(const char *name)
+{
+ char path[PATH_MAX];
+ struct cpu_map *cpus;
+ const char *sysfs = sysfs__mountpoint();

- cpus = cpu_map__read(file);
- fclose(file);
- return cpus;
+ snprintf(path, PATH_MAX, CPUS_TEMPLATE_UNCORE, sysfs, name);
+ cpus = __pmu_cpumask(path);
+ cpu_map__put(cpus);
+
+ return !!cpus;
}

/*
@@ -617,6 +641,8 @@ static struct perf_pmu *pmu_lookup(const char *name)

pmu->cpus = pmu_cpumask(name);

+ pmu->is_uncore = pmu_is_uncore(name);
+
INIT_LIST_HEAD(&pmu->format);
INIT_LIST_HEAD(&pmu->aliases);
list_splice(&format, &pmu->format);
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 389e972..fe0de05 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -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 */
--
1.9.1
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