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From:   Sumit Garg <sumit.garg@linaro.org>
Date:   Mon, 18 May 2020 11:16:20 +0530
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Subject: Re: [PATCH 0/3] arm64: perf: Add support for Perf NMI interrupts
To:     Lecopzer Chen <lecopzer@gmail.com>, julien.thierry.kdev@gmail.com
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        lecopzer.chen@mediatek.com, alexander.shishkin@linux.intel.com,
        Catalin Marinas <catalin.marinas@arm.com>, jolsa@redhat.com,
        acme@kernel.org, Peter Zijlstra <peterz@infradead.org>,
        mingo@redhat.com, linux-mediatek@lists.infradead.org,
        matthias.bgg@gmail.com, namhyung@kernel.org,
        Will Deacon <will@kernel.org>, yj.chiang@mediatek.com,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
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+ Julien

Hi Lecopzer,

On Sat, 16 May 2020 at 18:20, Lecopzer Chen <lecopzer@gmail.com> wrote:
>
> These series implement Perf NMI funxtionality and depends on
> Pseudo NMI [1] which has been upstreamed.
>
> In arm64 with GICv3, Pseudo NMI was implemented for NMI-like interruts.
> That can be extended to Perf NMI which is the prerequisite for hard-lockup
> detector which had already a standard interface inside Linux.
>
> Thus the first step we need to implement perf NMI interface and make sure
> it works fine.
>

This is something that is already implemented via Julien's patch-set
[1]. Its v4 has been floating since July, 2019 and I couldn't find any
major blocking comments but not sure why things haven't progressed
further.

Maybe Julien or Arm maintainers can provide updates on existing
patch-set [1] and how we should proceed further with this interesting
feature.

And regarding hard-lockup detection, I have been able to enable it
based on perf NMI events using Julien's perf patch-set [1]. Have a
look at the patch here [2].

[1] https://patchwork.kernel.org/cover/11047407/
[2] http://lists.infradead.org/pipermail/linux-arm-kernel/2020-May/732227.html

-Sumit

> Perf NMI has been test by dd if=/dev/urandom of=/dev/null like the link [2]
> did.
>
> [1] https://lkml.org/lkml/2019/1/31/535
> [2] https://www.linaro.org/blog/debugging-arm-kernels-using-nmifiq
>
>
> Lecopzer Chen (3):
>   arm_pmu: Add support for perf NMI interrupts registration
>   arm64: perf: Support NMI context for perf event ISR
>   arm64: Kconfig: Add support for the Perf NMI
>
>  arch/arm64/Kconfig             | 10 +++++++
>  arch/arm64/kernel/perf_event.c | 36 ++++++++++++++++++------
>  drivers/perf/arm_pmu.c         | 51 ++++++++++++++++++++++++++++++----
>  include/linux/perf/arm_pmu.h   |  6 ++++
>  4 files changed, 88 insertions(+), 15 deletions(-)
>
> --
> 2.25.1
>
>
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