[PATCH 6.5 095/285] perf header: Fix missing PMU caps

[Greg Kroah-Hartman]

6.5-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ian Rogers <irogers at google.com>

[ Upstream commit 9897009eecae821efc684ecdd1d04584f5501509 ]

PMU caps are written as HEADER_PMU_CAPS or for the special case of the
PMU "cpu" as HEADER_CPU_PMU_CAPS. As the PMU "cpu" is special, and not
any "core" PMU, the logic had become broken and core PMUs not called
"cpu" were not having their caps written.

This affects ARM and s390 non-hybrid PMUs.

Simplify the PMU caps writing logic to scan one fewer time and to be
more explicit in its behavior.

Fixes: 178ddf3bad981380 ("perf header: Avoid hybrid PMU list in write_pmu_caps")
Reported-by: Wei Li <liwei391 at huawei.com>
Signed-off-by: Ian Rogers <irogers at google.com>
Cc: Adrian Hunter <adrian.hunter at intel.com>
Cc: Alexander Shishkin <alexander.shishkin at linux.intel.com>
Cc: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
Cc: Huacai Chen <chenhuacai at kernel.org>
Cc: Ian Rogers <irogers at google.com>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: James Clark <james.clark at arm.com>
Cc: Jiri Olsa <jolsa at kernel.org>
Cc: John Garry <john.g.garry at oracle.com>
Cc: K Prateek Nayak <kprateek.nayak at amd.com>
Cc: Kajol Jain <kjain at linux.ibm.com>
Cc: Kan Liang <kan.liang at linux.intel.com>
Cc: Leo Yan <leo.yan at linaro.org>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Mike Leach <mike.leach at linaro.org>
Cc: Ming Wang <wangming01 at loongson.cn>
Cc: Namhyung Kim <namhyung at kernel.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Ravi Bangoria <ravi.bangoria at amd.com>
Cc: Sean Christopherson <seanjc at google.com>
Cc: Suzuki Poulouse <suzuki.poulose at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: linux-arm-kernel at lists.infradead.org
Link: https://lore.kernel.org/r/20230825024002.801955-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme at redhat.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 tools/perf/util/header.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 52fbf526fe74a..13c71d28e0eb3 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1605,8 +1605,15 @@ static int write_pmu_caps(struct feat_fd *ff,
 	int ret;
 
 	while ((pmu = perf_pmus__scan(pmu))) {
-		if (!pmu->name || !strcmp(pmu->name, "cpu") ||
-		    perf_pmu__caps_parse(pmu) <= 0)
+		if (!strcmp(pmu->name, "cpu")) {
+			/*
+			 * The "cpu" PMU is special and covered by
+			 * HEADER_CPU_PMU_CAPS. Note, core PMUs are
+			 * counted/written here for ARM, s390 and Intel hybrid.
+			 */
+			continue;
+		}
+		if (perf_pmu__caps_parse(pmu) <= 0)
 			continue;
 		nr_pmu++;
 	}
@@ -1619,23 +1626,17 @@ static int write_pmu_caps(struct feat_fd *ff,
 		return 0;
 
 	/*
-	 * Write hybrid pmu caps first to maintain compatibility with
-	 * older perf tool.
+	 * Note older perf tools assume core PMUs come first, this is a property
+	 * of perf_pmus__scan.
 	 */
-	if (perf_pmus__num_core_pmus() > 1) {
-		pmu = NULL;
-		while ((pmu = perf_pmus__scan_core(pmu))) {
-			ret = __write_pmu_caps(ff, pmu, true);
-			if (ret < 0)
-				return ret;
-		}
-	}
-
 	pmu = NULL;
 	while ((pmu = perf_pmus__scan(pmu))) {
-		if (pmu->is_core || !pmu->nr_caps)
+		if (!strcmp(pmu->name, "cpu")) {
+			/* Skip as above. */
+			continue;
+		}
+		if (perf_pmu__caps_parse(pmu) <= 0)
 			continue;
-
 		ret = __write_pmu_caps(ff, pmu, true);
 		if (ret < 0)
 			return ret;
-- 
2.40.1