linux-kernel - Re: [PATCH] arm_pmu: Validate single/group leader events

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Date:   Tue, 12 Apr 2022 11:14:19 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Rob Herring <robh@...nel.org>, Will Deacon <will@...nel.org>
Cc:     Al Grant <al.grant@....com>, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm_pmu: Validate single/group leader events

On Mon, Apr 11, 2022 at 09:14:03AM -0500, Rob Herring wrote:
> On Mon, Apr 11, 2022 at 11:04:26AM +0100, Mark Rutland wrote:
> > Hi Rob,
> > 
> > On Fri, Apr 08, 2022 at 03:33:30PM -0500, Rob Herring wrote:
> > > In the case where there is only a cycle counter available (i.e.
> > > PMCR_EL0.N is 0) and an event other than CPU cycles is opened, the open
> > > should fail as the event can never possibly be scheduled. However, the
> > > event validation when an event is opened is skipped when the group
> > > leader is opened. Fix this by always validating the group leader events.
> > > 
> > > Reported-by: Al Grant <al.grant@....com>
> > > Cc: Will Deacon <will@...nel.org>
> > > Cc: Mark Rutland <mark.rutland@....com>
> > > Signed-off-by: Rob Herring <robh@...nel.org>
> > 
> > This looks obviously correct to me, so FWIW:
> > 
> > Acked-by: Mark Rutland <mark.rutland@....com>
> 
> Thanks.
> 
> > Just to check, have you tested this (e.g. by running on a platform with
> > PMCR_EL0.N == 0, or hacking the PMU probing to report just the cycle counter)
> 
> Yes, tested on FVP with 0 counters running the libperf evsel userspace 
> access tests as that tries both the cycle counter and instruction 
> counts.

Perfect, thanks!

Will, I assume that you'll pick this up.

Mark.