linux-kernel - Re: [PATCH v2 0/6] coresight: Add config flag to enable branch broadcast

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Date:   Thu, 27 Jan 2022 13:26:26 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     James Clark <james.clark@....com>
Cc:     Suzuki.Poulose@....com, coresight@...ts.linaro.org,
        leo.yan@...aro.com, mike.leach@...aro.org,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.garry@...wei.com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2 0/6] coresight: Add config flag to enable branch broadcast

Hi James,

I am seriously back-logged in my patch reviews and as such will not be
able to get to your work in the usual 14 days.  At this time and if
everything goes well, I should be able to start reviewing this
patchset during the week of February 7th.

Thanks,
Mathieu

On Thu, 13 Jan 2022 at 02:11, James Clark <james.clark@....com> wrote:
>
> This allows enabling branch broadcast for Perf hosted sessions (the option
> is currently only available for the sysfs interface). Hopefully this could
> be useful for testing the decode in perf, for example does a determinisitic
> run with branch broadcast enabled look the same as with it disabled? It
> could also be used for scenarios like OpenJ9's support for JIT code:
>
>   java -Xjit:perfTool hello.java
>
> Currently this is not working and you get the usual errors of a missing
> DSO, but branch broadcast would have to be enabled anyway before working
> through this next issue:
>
>   CS ETM Trace: Debug data not found for address 0xffff7b94b058 in /tmp/perf-29360.map
>
> Address range support in Perf for branch broadcast has also not been added
> here, but could be added later.
>
> The documentation has been refactored slightly to allow updates to be made
> that link the Perf format arguments with the existing documentation.
>
> For Suzuki's comment, I will do it as a separate change that converts all
> the other hard coded values to a more consistent sysreg.h style:
>
>   nit: While at this, please could you change the hard coded value
>   to ETM4_CFG_BIT_RETSTK ?
>
> Changes since v1:
>
>   * Added Leo's reviewed by on patch 3
>   * Fix bracket styling
>   * Add documentation
>
> Applies on top of coresight/next efa56eddf5d5c. But this docs fix is also
> required to get the links to work:
>   https://marc.info/?l=linux-doc&m=164139331923986&w=2
>
> Also available at: https://gitlab.arm.com/linux-arm/linux-jc/-/tree/james-branch-broadcast-v2
>
> James Clark (6):
>   coresight: Add config flag to enable branch broadcast
>   coresight: Fail to open with return stacks if they are unavailable
>   perf cs-etm: Update deduction of TRCCONFIGR register for branch
>     broadcast
>   Documentation: coresight: Turn numbered subsections into real
>     subsections
>   Documentation: coresight: Link config options to existing
>     documentation
>   Documentation: coresight: Expand branch broadcast documentation
>
>  .../coresight/coresight-etm4x-reference.rst   | 14 ++++-
>  Documentation/trace/coresight/coresight.rst   | 56 +++++++++++++++++--
>  .../hwtracing/coresight/coresight-etm-perf.c  |  2 +
>  .../coresight/coresight-etm4x-core.c          | 23 ++++++--
>  include/linux/coresight-pmu.h                 |  2 +
>  tools/include/linux/coresight-pmu.h           |  2 +
>  tools/perf/arch/arm/util/cs-etm.c             |  3 +
>  7 files changed, 92 insertions(+), 10 deletions(-)
>
> --
> 2.28.0
>