linux-kernel - Re: [PATCH v6 0/7] arm_pmu: Use NMI for perf interrupt

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Message-ID: <296304b8-aadd-817d-bb12-dc7524b6f0f5@arm.com>
Date:   Mon, 21 Sep 2020 16:41:00 +0100
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     Will Deacon <will@...nel.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, maz@...nel.org, catalin.marinas@....com,
        swboyd@...omium.org, sumit.garg@...aro.org
Subject: Re: [PATCH v6 0/7] arm_pmu: Use NMI for perf interrupt

Hi Will,

Thank you so much for reviewing the series!

On 9/21/20 2:59 PM, Will Deacon wrote:
> On Wed, Aug 19, 2020 at 02:34:12PM +0100, Alexandru Elisei wrote:
>> The series makes the arm_pmu driver use NMIs for the perf interrupt when
>> NMIs are available on the platform (currently, only arm64 + GICv3). To make
>> it easier to play with the patches, I've pushed a branch at [1]:
> This mostly looks good to me, but see some of the comments I left on the
> code. One other thing I'm not sure about is whether or not we should tell
> userspace that we're using an NMI for the sampling. Do any other
> architectures have a conditional NMI?

I'm not sure about other architectures being able to configure the perf interrupt
as NMI or a regular interrupt, I'll try to find out. Regardless of what the other
architecture do, I am of the opinion that we should spell out explicitly when the
PMU is using pseudo-NMIs, because it makes a huge difference in the accuracy of
the instrumentation and the overall usefulness of perf.

If I spin a v7 quickly, is it still time to merge the series for 5.10?

Thanks,
Alex