linux-kernel - Re: [PATCH v3 3/3] perf test: Add user space counter reading tests

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Date:   Wed, 20 Jul 2022 08:09:50 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Vince Weaver <vincent.weaver@...ne.edu>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Rob Herring <robh@...nel.org>,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v3 3/3] perf test: Add user space counter reading tests

On Wed, Jul 20, 2022 at 7:57 AM Vince Weaver <vincent.weaver@...ne.edu> wrote:
>
> On Tue, 19 Jul 2022, Ian Rogers wrote:
>
> > These tests are based on test_stat_user_read in
> > tools/lib/perf/tests/test-evsel.c. The tests are modified to skip if
> > perf_event_open fails or rdpmc isn't supported.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
>
> > +             .type   = PERF_TYPE_HARDWARE,
> > +             .config = event,
> > +#ifdef __aarch64__
> > +             .config1 = 0x2,         /* Request user access */
> > +#endif
>
> should this value have a name rather than being a "magic constant"?

Thanks! Firstly, this is just moving code around and so not a
regression introduced by this code:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/lib/perf/tests/test-evsel.c?h=perf/core#n134
I don't believe there is an existing constant for this purpose. The
kernel isn't using one either:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/kernel/perf_event.c#n309

So I agree with you and hopefully this is something ARM will clean up.

Thanks,
Ian

> Vince