linux-kernel - Re: [PATCH 4/5] perf arm-spe: Implement find

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Message-ID: <6b092f13-832f-5d1d-a504-aea96c81bf17@arm.com>
Date:   Wed, 6 Oct 2021 10:35:20 +0100
From:   German Gomez <german.gomez@....com>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, coresight@...ts.linaro.org
Subject: Re: [PATCH 4/5] perf arm-spe: Implement find_snapshot callback

Hi Leo,

Many thanks for your comments.

On 04/10/2021 13:27, Leo Yan wrote:

> Hi German,
>
> On Thu, Sep 30, 2021 at 01:26:15PM +0100, German Gomez wrote:
>
> [...]
>
> So simply say, I think the head pointer monotonically increasing is
> the right thing to do in Arm SPE driver.

I will talk to James about how we can proceed on this.

>> (note that the patch will skip the wrap-around detection if this is the
>> case,
>> in order to handle both cases in the userspace perf tool).
> Almost agree, I read multiple times but have no idea what's the
> "both cases" in the last sentence.

Apologies for the later part was not clear. What I meant to say was that
in the original patch for cs-etm, it seemed to handle both cases where
AUX head might be monotonically and non-monotonically increasing, so we
applied the same for the Arm SPE patch.

>
> Please let me know if anything is not clear.
>
> Thanks,
> Leo
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/util/auxtrace.c#n1804