linux-kernel - [PATCH 6.6 370/638] perf pmu: Treat the msr pmu as software

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Date: Sun, 24 Mar 2024 18:56:47 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Ian Rogers <irogers@...gle.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	James Clark <james.clark@....com>,
	Caleb Biggers <caleb.biggers@...el.com>,
	Edward Baker <edward.baker@...el.com>,
	Perry Taylor <perry.taylor@...el.com>,
	Samantha Alt <samantha.alt@...el.com>,
	Weilin Wang <weilin.wang@...el.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.6 370/638] perf pmu: Treat the msr pmu as software

From: Ian Rogers <irogers@...gle.com>

[ Upstream commit 24852ef2e2d5c555c2da05baff112ea414b6e0f5 ]

The msr PMU is a software one, meaning msr events may be grouped
with events in a hardware context. As the msr PMU isn't marked as a
software PMU by perf_pmu__is_software, groups with the msr PMU in
are broken and the msr events placed in a different group. This
may lead to multiplexing errors where a hardware event isn't
counted while the msr event, such as tsc, is. Fix all of this by
marking the msr PMU as software, which agrees with the driver.

Before:
```
$ perf stat -e '{slots,tsc}' -a true
WARNING: events were regrouped to match PMUs

 Performance counter stats for 'system wide':

         1,750,335      slots
         4,243,557      tsc

       0.001456717 seconds time elapsed
```

After:
```
$ perf stat -e '{slots,tsc}' -a true
 Performance counter stats for 'system wide':

        12,526,380      slots
         3,415,163      tsc

       0.001488360 seconds time elapsed
```

Fixes: 251aa040244a ("perf parse-events: Wildcard most "numeric" events")
Signed-off-by: Ian Rogers <irogers@...gle.com>
Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
Cc: James Clark <james.clark@....com>
Cc: Caleb Biggers <caleb.biggers@...el.com>
Cc: Edward Baker <edward.baker@...el.com>
Cc: Perry Taylor <perry.taylor@...el.com>
Cc: Samantha Alt <samantha.alt@...el.com>
Cc: Weilin Wang <weilin.wang@...el.com>
Link: https://lore.kernel.org/r/20240124234200.1510417-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/perf/util/pmu.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index d515ba8a0e160..a3c7814116c7c 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1735,6 +1735,12 @@ bool pmu__name_match(const struct perf_pmu *pmu, const char *pmu_name)
 
 bool perf_pmu__is_software(const struct perf_pmu *pmu)
 {
+	const char *known_sw_pmus[] = {
+		"kprobe",
+		"msr",
+		"uprobe",
+	};
+
 	if (pmu->is_core || pmu->is_uncore || pmu->auxtrace)
 		return false;
 	switch (pmu->type) {
@@ -1746,7 +1752,11 @@ bool perf_pmu__is_software(const struct perf_pmu *pmu)
 	case PERF_TYPE_BREAKPOINT:	return true;
 	default: break;
 	}
-	return !strcmp(pmu->name, "kprobe") || !strcmp(pmu->name, "uprobe");
+	for (size_t i = 0; i < ARRAY_SIZE(known_sw_pmus); i++) {
+		if (!strcmp(pmu->name, known_sw_pmus[i]))
+			return true;
+	}
+	return false;
 }
 
 FILE *perf_pmu__open_file(struct perf_pmu *pmu, const char *name)
-- 
2.43.0