linux-kernel - Re: [PATCH v7 08/12] perf: Add perf_event

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Message-ID: <CAP-5=fXBot2K0MR9t7o6J7-FihNXzKcotdF6p3bfL7DwqR9jfg@mail.gmail.com>
Date: Mon, 18 Aug 2025 08:51:50 -0700
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, Jonathan Corbet <corbet@....net>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Joey Gouly <joey.gouly@....com>, 
	Suzuki K Poulose <suzuki.poulose@....com>, Zenghui Yu <yuzenghui@...wei.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Leo Yan <leo.yan@....com>, 
	Anshuman Khandual <anshuman.khandual@....com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	linux-doc@...r.kernel.org, kvmarm@...ts.linux.dev
Subject: Re: [PATCH v7 08/12] perf: Add perf_event_attr::config4

On Thu, Aug 14, 2025 at 2:26 AM James Clark <james.clark@...aro.org> wrote:
>
> Arm FEAT_SPE_FDS adds the ability to filter on the data source of a
> packet using another 64-bits of event filtering control. As the existing
> perf_event_attr::configN fields are all used up for SPE PMU, an
> additional field is needed. Add a new 'config4' field.

Somewhat off-topic, imo it would be nice if we could land:
https://lore.kernel.org/lkml/20250603181634.1362626-1-ctshao@google.com/
and show all the config values via fdinfo to better allow tools to
diagnose when PMUs are busy, etc. The patch there tries to be minimal
and just reveal config (even with being minimal the patch is stalled).

Thanks,
Ian

> Reviewed-by: Leo Yan <leo.yan@....com>
> Tested-by: Leo Yan <leo.yan@....com>
> Reviewed-by: Ian Rogers <irogers@...gle.com>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
>  include/uapi/linux/perf_event.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 78a362b80027..0d0ed85ad8cb 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -382,6 +382,7 @@ enum perf_event_read_format {
>  #define PERF_ATTR_SIZE_VER6                    120     /* Add: aux_sample_size */
>  #define PERF_ATTR_SIZE_VER7                    128     /* Add: sig_data */
>  #define PERF_ATTR_SIZE_VER8                    136     /* Add: config3 */
> +#define PERF_ATTR_SIZE_VER9                    144     /* add: config4 */
>
>  /*
>   * 'struct perf_event_attr' contains various attributes that define
> @@ -543,6 +544,7 @@ struct perf_event_attr {
>         __u64   sig_data;
>
>         __u64   config3; /* extension of config2 */
> +       __u64   config4; /* extension of config3 */
>  };
>
>  /*
>
> --
> 2.34.1
>