Re: [PATCH V12 11/14] perf tools: Add missing_features for aux_start_paused, aux_pause, aux_resume

[Leo Yan <leo.yan@linux.dev>]

On Thu, Oct 10, 2024 at 05:31:48PM +0300, Adrian Hunter wrote:
> Display "feature is not supported" error message if aux_start_paused,
> aux_pause or aux_resume result in a perf_event_open() error.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> Acked-by: Ian Rogers <irogers@google.com>
> Reviewed-by: Andi Kleen <ak@linux.intel.com>

This patch looks good to me.

A case is the Linux kernel has supported aux_pause_resume feature, but
the PMU event does not support it. So we might consider to add a extra
patch in perf:

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 927aa61e7b14..9a3191df2ec5 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -3373,6 +3373,10 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
                        return scnprintf(msg, size,
        "%s: PMU Hardware doesn't support 'aux_output' feature",
                                         evsel__name(evsel));
+               if (evsel->core.attr.aux_action)
+                       return scnprintf(msg, size,
+       "%s: PMU Hardware doesn't support 'aux_action' feature",
+                                        evsel__name(evsel));
                if (evsel->core.attr.sample_period != 0)
                        return scnprintf(msg, size,
        "%s: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat'",

Thanks,
Leo

> ---
>  tools/perf/util/evsel.c | 10 +++++++++-
>  tools/perf/util/evsel.h |  1 +
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index d34ceab9e454..927aa61e7b14 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2147,7 +2147,13 @@ bool evsel__detect_missing_features(struct evsel *evsel)
>  	 * Must probe features in the order they were added to the
>  	 * perf_event_attr interface.
>  	 */
> -	if (!perf_missing_features.branch_counters &&
> +	if (!perf_missing_features.aux_pause_resume &&
> +	    (evsel->core.attr.aux_pause || evsel->core.attr.aux_resume ||
> +	     evsel->core.attr.aux_start_paused)) {
> +		perf_missing_features.aux_pause_resume = true;
> +		pr_debug2_peo("Kernel has no aux_pause/aux_resume support, bailing out\n");
> +		return false;
> +	} else if (!perf_missing_features.branch_counters &&
>  	    (evsel->core.attr.branch_sample_type & PERF_SAMPLE_BRANCH_COUNTERS)) {
>  		perf_missing_features.branch_counters = true;
>  		pr_debug2("switching off branch counters support\n");
> @@ -3397,6 +3403,8 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
>  			return scnprintf(msg, size, "clockid feature not supported.");
>  		if (perf_missing_features.clockid_wrong)
>  			return scnprintf(msg, size, "wrong clockid (%d).", clockid);
> +		if (perf_missing_features.aux_pause_resume)
> +			return scnprintf(msg, size, "The 'aux_pause / aux_resume' feature is not supported, update the kernel.");
>  		if (perf_missing_features.aux_output)
>  			return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
>  		if (!target__has_cpu(target))
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 15e745a9a798..778fcdb8261f 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -221,6 +221,7 @@ struct perf_missing_features {
>  	bool weight_struct;
>  	bool read_lost;
>  	bool branch_counters;
> +	bool aux_pause_resume;
>  };
>  
>  extern struct perf_missing_features perf_missing_features;
> -- 
> 2.43.0
> 
>