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

[Rob Herring <robh@kernel.org>]

On Thu, Oct 14, 2021 at 11:58 AM Mark Rutland <mark.rutland@arm.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