Date:   Mon, 18 May 2020 19:39:23 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Alexandru Elisei <alexandru.elisei@....com>,
        Mark Rutland <mark.rutland@....com>
Cc:     Lecopzer Chen <lecopzer@...il.com>, julien.thierry.kdev@...il.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jian-Lin Chen <lecopzer.chen@...iatek.com>,
        alexander.shishkin@...ux.intel.com,
        Catalin Marinas <catalin.marinas@....com>, jolsa@...hat.com,
        acme@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        mingo@...hat.com, linux-mediatek@...ts.infradead.org,
        matthias.bgg@...il.com, namhyung@...nel.org,
        Will Deacon <will@...nel.org>, yj.chiang@...iatek.com,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 0/3] arm64: perf: Add support for Perf NMI interrupts

On Mon, 18 May 2020 at 16:47, Alexandru Elisei <alexandru.elisei@....com> wrote:
>
> Hi,
>
> On 5/18/20 11:45 AM, Mark Rutland wrote:
> > Hi all,
> >
> > On Mon, May 18, 2020 at 02:26:00PM +0800, Lecopzer Chen wrote:
> >> HI Sumit,
> >>
> >> Thanks for your information.
> >>
> >> I've already implemented IPI (same as you did [1], little difference
> >> in detail), hardlockup detector and perf in last year(2019) for
> >> debuggability.
> >> And now we tend to upstream to reduce kernel maintaining effort.
> >> I'm glad if someone in ARM can do this work :)
> >>
> >> Hi Julien,
> >>
> >> Does any Arm maintainers can proceed this action?
> > Alexandru (Cc'd) has been rebasing and reworking Julien's patches, which
> > is my preferred approach.
> >
> > I understand that's not quite ready for posting since he's investigating
> > some of the nastier subtleties (e.g. mutual exclusion with the NMI), but
> > maybe we can put the work-in-progress patches somewhere in the mean
> > time.
> >
> > Alexandru, do you have an idea of what needs to be done, and/or when you
> > expect you could post that?
>
> I'm currently working on rebasing the patches on top of 5.7-rc5, when I have
> something usable I'll post a link (should be a couple of days). After that I will
> address the review comments, and I plan to do a thorough testing because I'm not
> 100% confident that some of the assumptions around the locks that were removed are
> correct. My guess is this will take a few weeks.
>

Thanks Mark, Alex for the status updates on perf NMI feature.

Alex,

As the hard-lockup detection patch [1] has a dependency on perf NMI
patch-set, I will rebase and test hard-lockup detector when you have
got a working tree. But due to the dependency, I think patch [1]
should be accepted along with perf NMI patch-set. So would you be open
to include this patch as part of your series?

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2020-May/732227.html

-Sumit

> Thanks,
> Alex
> >
> > Thanks,
> > Mark.
> >
> >> This is really useful in debugging.
> >> Thank you!!
> >>
> >>
> >>
> >> [1] https://lkml.org/lkml/2020/4/24/328
> >>
> >>
> >> Lecopzer
> >>
> >> Sumit Garg <sumit.garg@...aro.org> 於 2020年5月18日 週一 下午1:46寫道：
> >>> + Julien
> >>>
> >>> Hi Lecopzer,
> >>>
> >>> On Sat, 16 May 2020 at 18:20, Lecopzer Chen <lecopzer@...il.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
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> linux-arm-kernel mailing list
> >>>> linux-arm-kernel@...ts.infradead.org
> >>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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