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

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Date:   Mon, 21 Sep 2020 18:53:31 +0100
From:   Will Deacon <will@...nel.org>
To:     Alexandru Elisei <alexandru.elisei@....com>
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

On Mon, Sep 21, 2020 at 04:41:00PM +0100, Alexandru Elisei wrote:
> 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?

I'm on holiday for the rest of the week, but please post something when you
have it and I'll queue it if I manage to get to it.

Will