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

[Leo Yan]

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.hun...@intel.com>
> Acked-by: Ian Rogers <irog...@google.com>
> Reviewed-by: Andi Kleen <a...@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
> 
>