linux-kernel - Re: [PATCH v10 4/5] arm64: perf: Enable PMU counter userspace access for perf event

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Message-ID: <CAL_JsqJHfpcvKekEFm-d7rMJ=UNc7dXwfaMMkUWZYsnPg=QNPQ@mail.gmail.com>
Date:   Fri, 15 Oct 2021 10:53:15 -0500
From:   Rob Herring <robh@...nel.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Honnappa Nagarahalli <honnappa.nagarahalli@....com>,
        Zachary.Leaf@....com, Raphael Gault <raphael.gault@....com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        Vince Weaver <vincent.weaver@...ne.edu>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v10 4/5] arm64: perf: Enable PMU counter userspace access
 for perf event

On Thu, Oct 14, 2021 at 11:58 AM Mark Rutland <mark.rutland@....com> wrote:
>
> Hi Rob,
>
> This looks pretty good!
>
> I have one largish query below, and otherwise only trivialities that I'm
> happy to fix up.
>
> On Tue, Sep 14, 2021 at 03:47:59PM -0500, Rob Herring wrote:

[...]

> >  static inline bool armv8pmu_event_is_chained(struct perf_event *event)
> >  {
> >       int idx = event->hw.idx;
> >       struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
> >
> > -     return !WARN_ON(idx < 0) &&
> > +     return !(event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT) &&
> >              armv8pmu_event_is_64bit(event) &&
> >              !armv8pmu_has_long_event(cpu_pmu) &&
> >              (idx != ARMV8_IDX_CYCLE_COUNTER);
> > @@ -720,6 +726,27 @@ static inline u32 armv8pmu_getreset_flags(void)
> >       return value;
>
> Above this, could we please add:
>
> | static inline bool armv8pmu_event_has_user_read(struct perf_event *event)
> | {
> |       return event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT;
> | }
>
> ... and use that where we look at PERF_EVENT_FLAG_USER_READ_CNT?

Sure, but as this is a common flag now, I should probably make that a
common function in linux/perf_event.h and have x86 code use it too.

Rob