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Subject: Re: [PATCH v6 0/7] arm_pmu: Use NMI for perf interrupt
To:     Will Deacon <will@kernel.org>
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        mark.rutland@arm.com, maz@kernel.org, catalin.marinas@arm.com,
        swboyd@chromium.org, sumit.garg@linaro.org
References: <20200819133419.526889-1-alexandru.elisei@arm.com>
 <20200921135951.GN2139@willie-the-truck>
From:   Alexandru Elisei <alexandru.elisei@arm.com>
Message-ID: <296304b8-aadd-817d-bb12-dc7524b6f0f5@arm.com>
Date:   Mon, 21 Sep 2020 16:41:00 +0100
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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