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Subject: Re: [PATCH 0/3] arm64: perf: Add support for Perf NMI interrupts
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Lecopzer Chen <lecopzer@gmail.com>
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From:   Alexandru Elisei <alexandru.elisei@arm.com>
Message-ID: <1d615c32-89f0-d9ba-43db-3d90c7d53e15@arm.com>
Date:   Thu, 21 May 2020 13:36:06 +0100
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Hi,

On 5/21/20 4:00 AM, Song Bao Hua (Barry Song) wrote:

>
>> -----Original Message-----
>> From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@lists.infradead.org]
>> 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 .

That's good news that it works for you, thanks for letting me know.

Alex