Re: [patch] perf tools: perf list broken on ARM

[Namhyung Kim]

Hi Vince,

On Mon, 9 Dec 2013 16:58:35 -0500 (EST), Vince Weaver wrote:
> Hello,
>
> "perf list" listing of hardware events doesn't work on older ARM devices.
> The change enabling event detection:
>
> commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b
> Author: Namhyung Kim <namhyung.kim@xxxxxxx>
> Date:   Tue Aug 27 11:41:53 2013 +0900
>
>     perf list: Skip unsupported events
>
>
> uses the following code in tools/perf/util/parse-events.c:
>
>        struct perf_event_attr attr = {
>                .type = type,
>                .config = config,
>                .disabled = 1,
>                .exclude_kernel = 1,
>        };
>
> On ARM machines pre-dating the Cortex-A15 this doesn't work, as
> these machines don't support .exclude_kernel.  So starting with 3.12
> "perf list" does not report any hardware events at all on older
> machines (seen on Rasp-Pi, Pandaboard, Beagleboard, etc).
>
> If we drop the "exclude_kernel" attribute events are properly reported.

Okay, the reason I set the bit was consideration of a very strict
perf_event_paranoid setting (-2).

So maybe we can try it again with the bit cleared after a failure, or
checking the paranoid setting first.

Thanks,
Namhyung
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