[PATCH v1] perf arm: Workaround ARM PMUs cpu maps having offline cpus

[Ian Rogers]

When PMUs have a cpu map in the 'cpus' or 'cpumask' file, perf will
try to open events on those CPUs. ARM doesn't remove offline CPUs
meaning taking a CPU offline will cause perf commands to fail unless a
CPU map is passed on the command line.

More context in:
https://lore.kernel.org/lkml/20240603092812.46616-1-yangyicong@huawei.com/

Reported-by: Yicong Yang <yangyicong at huawei.com>
Closes: https://lore.kernel.org/lkml/20240603092812.46616-2-yangyicong@huawei.com/
Signed-off-by: Ian Rogers <irogers at google.com>
---
 tools/perf/arch/arm/util/pmu.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/perf/arch/arm/util/pmu.c b/tools/perf/arch/arm/util/pmu.c
index 8b7cb68ba1a8..6b544edbd3f6 100644
--- a/tools/perf/arch/arm/util/pmu.c
+++ b/tools/perf/arch/arm/util/pmu.c
@@ -11,12 +11,15 @@
 
 #include "arm-spe.h"
 #include "hisi-ptt.h"
+#include "../../../util/cpumap.h"
 #include "../../../util/pmu.h"
 #include "../../../util/cs-etm.h"
 #include "../../arm64/util/mem-events.h"
 
-void perf_pmu__arch_init(struct perf_pmu *pmu __maybe_unused)
+void perf_pmu__arch_init(struct perf_pmu *pmu)
 {
+	struct perf_cpu_map *intersect;
+
 #ifdef HAVE_AUXTRACE_SUPPORT
 	if (!strcmp(pmu->name, CORESIGHT_ETM_PMU_NAME)) {
 		/* add ETM default config here */
@@ -33,6 +36,9 @@ void perf_pmu__arch_init(struct perf_pmu *pmu __maybe_unused)
 		pmu->selectable = true;
 #endif
 	}
-
 #endif
+	/* Workaround some ARM PMU's failing to correctly set CPU maps for online processors. */
+	intersect = perf_cpu_map__intersect(cpu_map__online(), pmu->cpus);
+	perf_cpu_map__put(pmu->cpus);
+	pmu->cpus = intersect;
 }
-- 
2.45.2.505.gda0bf45e8d-goog