linux-kernel - [PATCH v1] perf pmu: Treat the msr pmu as software

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240124234200.1510417-1-irogers@google.com>
Date: Wed, 24 Jan 2024 15:42:00 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@....com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Perry Taylor <perry.taylor@...el.com>, Samantha Alt <samantha.alt@...el.com>, 
	Caleb Biggers <caleb.biggers@...el.com>, Weilin Wang <weilin.wang@...el.com>, 
	Edward Baker <edward.baker@...el.com>
Subject: [PATCH v1] perf pmu: Treat the msr pmu as software

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>
---
The fixes tag is close enough rather than being fully accurate. The
regression was introduced earlier by the automatic event regrouping.
---
 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 3c9609944a2f..88b9aa7d3a27 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1760,6 +1760,12 @@ 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) {
@@ -1771,7 +1777,11 @@ 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(const struct perf_pmu *pmu, const char *name)
-- 
2.43.0.429.g432eaa2c6b-goog