RE: [PATCH 0/3] arm64: perf: Add support for Perf NMI interrupts

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx]
> On Behalf Of Alexandru Elisei
> Sent: Wednesday, May 20, 2020 10:31 PM> 
> Hi,
> 
> On 5/18/20 12:17 PM, Alexandru Elisei 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.
> 
> Pushed a WIP branch on linux-arm.org [1]:
> 
> git clone -b WIP-pmu-nmi git://linux-arm.org/linux-ae
> 
> Practically untested, I only did perf record on a defconfig kernel running on the
> model.
> 
> [1]
> http://www.linux-arm.org/git?p=linux-ae.git;a=shortlog;h=refs/heads/WIP-pm
> u-nmi

Fortunately, it does work. I used this tree to perf annotate arm_smmu_cmdq_issue_cmdlist() which
is completely disabling IRQ. Luckily, it reports correct data. Before that, it reported all time was spent by
the code which enabled IRQ .


Barry

> 
> Thanks,
> Alex
> >
> > 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@xxxxxxxxxx> æ 2020å5æ18æ éä äå
> 1:46åéï
> >>>> + Julien
> >>>>
> >>>> Hi Lecopzer,
> >>>>
> >>>> On Sat, 16 May 2020 at 18:20, Lecopzer Chen <lecopzer@xxxxxxxxx>
> 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/7322
> >>>> 27.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