Re: [PATCH v2] perf pmu: Skip test on Arm64 when #slots is zero

[James Clark <james.clark@linaro.org>]

On 10/04/2026 12:13, Leo Yan wrote:
> Some Arm64 PMUs expose 'caps/slots' as 0 when the slot count is not
> implemented, tool_pmu__read_event() currently returns false for this,
> 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
> expected 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@arm.com>

Reviewed-by: James Clark <james.clark@linaro.org>

> ---
> Changes in v2:
> - Checked pm->metric_expr instead of pm->metric_name and removed the
>    negation before strstr() suggested by sashiko.
> - Link to v1: https://lore.kernel.org/r/20260410-perf_fix_pmu_metrics_test-v1-1-18a5d80f71b6@arm.com
> ---
>   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..b1609a7e1d8c9427e6bf9500380e8aac6167c7fa 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_expr, "#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,