linux-kernel - Re: [PATCH] perf: arm_pmuv3: Fix chained event check for cycle counter

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Message-ID: <CAL_Jsq+YoHYyUF25aD6ACbiUj3+M2c4uH5tWGB+u12AiCp6fGg@mail.gmail.com>
Date: Thu, 1 Aug 2024 11:19:26 -0600
From: Rob Herring <robh@...nel.org>
To: Will Deacon <will@...nel.org>, catalin.marinas@....com
Cc: Mark Rutland <mark.rutland@....com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: arm_pmuv3: Fix chained event check for cycle counter

On Thu, Aug 1, 2024 at 5:29 AM Will Deacon <will@...nel.org> wrote:
>
> On Wed, Jul 10, 2024 at 12:23:56PM -0600, Rob Herring (Arm) wrote:
> > Since commit b7e89b0f5bd7 ("perf: arm_pmu: Remove event index to
> > counter remapping"), armv8pmu_event_is_chained() is incorrectly
> > returning that the cycle counter is chained, but the cycle counter has
> > always been 64-bit. The result is trying to configure counter #30 which
> > typically doesn't exist.
> >
> > As ARMV8_PMU_MAX_GENERAL_COUNTERS is the number of counters (31), the
> > comparison to the counter index needs to be '<' rather than '<='.
> >
> > Fixes: b7e89b0f5bd7 ("perf: arm_pmu: Remove event index to counter remapping")
> > Signed-off-by: Rob Herring (Arm) <robh@...nel.org>
> > ---
> >  drivers/perf/arm_pmuv3.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
> > index 3b3a3334cc3f..0e22c68fb804 100644
> > --- a/drivers/perf/arm_pmuv3.c
> > +++ b/drivers/perf/arm_pmuv3.c
> > @@ -482,7 +482,7 @@ static bool armv8pmu_event_is_chained(struct perf_event *event)
> >       return !armv8pmu_event_has_user_read(event) &&
> >              armv8pmu_event_is_64bit(event) &&
> >              !armv8pmu_has_long_event(cpu_pmu) &&
> > -            (idx <= ARMV8_PMU_MAX_GENERAL_COUNTERS);
> > +            (idx < ARMV8_PMU_MAX_GENERAL_COUNTERS);
> >  }
>
> Acked-by: Will Deacon <will@...nel.org>
>
> Catalin -- please can you pick this up as a fix?

No, this is the fix for what Will dropped and said to resend on the
v9.4 fixed instruction counter series. Here's the series with the fix
in it[1].

Rob

[1] https://lore.kernel.org/all/20240731-arm-pmu-3-9-icntr-v3-0-280a8d7ff465@kernel.org/