linux-kernel - Re: [PATCH v3 8/8] perf: arm_spe: Add support for SPEv1.2 inverted event filtering

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Message-ID: <CAL_JsqKS+xos95R0KUhm-xJ5ZhTaa7XYc-Ly45BCEWTXOh4j7w@mail.gmail.com>
Date:   Tue, 8 Nov 2022 07:12:53 -0600
From:   Rob Herring <robh@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Ingo Molnar <mingo@...hat.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kvmarm@...ts.linux.dev, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, James Clark <james.clark@....com>,
        Mark Brown <broonie@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH v3 8/8] perf: arm_spe: Add support for SPEv1.2 inverted
 event filtering

On Mon, Nov 7, 2022 at 1:48 PM Namhyung Kim <namhyung@...nel.org> wrote:
>
> Hello,
>
> On Fri, Nov 4, 2022 at 8:55 AM Rob Herring <robh@...nel.org> wrote:
> >
> > Arm SPEv1.2 (Arm v8.7/v9.2) adds a new feature called Inverted Event
> > Filter which excludes samples matching the event filter. The feature
> > mirrors the existing event filter in PMSEVFR_EL1 adding a new register,
> > PMSNEVFR_EL1, which has the same event bit assignments.
>
> Just out of curiosity, is it possible to have the event filter and
> inverted filter at the same time?

Yes, that's why config3 is needed. Samples with all the events set in
PMSEVFR_EL1 and none of the events set in PMSNEVFR_EL1 are recorded.
For example if an event bit is 0 in PMSEVFR_EL1, then recorded samples
may or may not have that event. If the same event bit is then set in
PMSNEVFR_EL1, then record samples will not have that event.

> What if they have the same?

You'd get no samples.

Rob