[PATCH] perf pmu: Skip test on Arm64 when #slots is zero

[Leo Yan]

Some Arm64 PMUs expose 'caps/slots' as 0 when the slot count is not
implemented, tool_pmu__read_event() currently treats that as a read
failure, so metrics that reference #slots are reported as syntax
error.

Since the commit 3a61fd866ef9 ("perf expr: Return -EINVAL for syntax
error in expr__find_ids()"), these syntax errors are populated as
failures and make the PMU metric test fail:

    9.3: Parsing of PMU event table metrics:
    --- start ---
    ...

    Found metric 'backend_bound'
    metric expr 100 * (stall_slot_backend / (#slots * cpu_cycles)) for backend_bound
    parsing metric: 100 * (stall_slot_backend / (#slots * cpu_cycles))
    Failure to read '#slots'
    literal: #slots = nan
    syntax error
    Fail to parse metric or group `backend_bound'

    ...
    ---- end(-1) ----
    9.3: Parsing of PMU event table metrics    : FAILED!

This commit introduces a new function is_expected_broken_metric() to
identify broken metrics, and treats metrics containing "#slots" as
broken when #slots == 0 on Arm64 platforms.

Fixes: 3a61fd866ef9 ("perf expr: Return -EINVAL for syntax error in expr__find_ids()")
Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
---
 tools/perf/tests/pmu-events.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/perf/tests/pmu-events.c b/tools/perf/tests/pmu-events.c
index a997168621688007c85495e2d9f6f459c2471516..6a68d46a4fcd96b7ce46272af36fcb5590939505 100644
--- a/tools/perf/tests/pmu-events.c
+++ b/tools/perf/tests/pmu-events.c
@@ -15,6 +15,7 @@
 #include "util/expr.h"
 #include "util/hashmap.h"
 #include "util/parse-events.h"
+#include "util/tool_pmu.h"
 #include "metricgroup.h"
 #include "stat.h"
 
@@ -817,6 +818,26 @@ struct metric {
 	struct metric_ref metric_ref;
 };
 
+static bool is_expected_broken_metric(const struct pmu_metric *pm)
+{
+	if (!strcmp(pm->metric_name, "M1") || !strcmp(pm->metric_name, "M2") ||
+	    !strcmp(pm->metric_name, "M3"))
+		return true;
+
+#if defined(__aarch64__)
+	/*
+	 * Arm64 platforms may return “#slots == 0”, which is treated as a
+	 * syntax error by the parser. Don't test these metrics when running
+	 * on such platforms.
+	 */
+	if (!strstr(pm->metric_name, "#slots") &&
+	    !tool_pmu__cpu_slots_per_cycle())
+		return true;
+#endif
+
+	return false;
+}
+
 static int test__parsing_callback(const struct pmu_metric *pm,
 				  const struct pmu_metrics_table *table,
 				  void *data)
@@ -852,8 +873,7 @@ static int test__parsing_callback(const struct pmu_metric *pm,
 
 	err = metricgroup__parse_groups_test(evlist, table, pm->metric_name);
 	if (err) {
-		if (!strcmp(pm->metric_name, "M1") || !strcmp(pm->metric_name, "M2") ||
-		    !strcmp(pm->metric_name, "M3")) {
+		if (is_expected_broken_metric(pm)) {
 			(*failures)--;
 			pr_debug("Expected broken metric %s skipping\n", pm->metric_name);
 			err = 0;

---
base-commit: 4cf1f549bbcdfea9c20df52994bb342677472dcd
change-id: 20260408-perf_fix_pmu_metrics_test-73c4dedc8585

Best regards,
-- 
Leo Yan <leo.yan@xxxxxxx>