linux-kernel - Re: [PATCH v4 16/26] genirq: Allow per-cpu interrupt sharing for non-overlapping affinities

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Message-ID: <20251112182521.000027ad@huawei.com>
Date: Wed, 12 Nov 2025 18:25:21 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Marc Zyngier <maz@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-acpi@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, "Mark
 Rutland" <mark.rutland@....com>, Will Deacon <will@...nel.org>, "Rafael J.
 Wysocki" <rafael@...nel.org>, Rob Herring <robh@...nel.org>, "Saravana
 Kannan" <saravanak@...gle.com>, Greg Kroah-Hartman
	<gregkh@...uxfoundation.org>, Sven Peter <sven@...nel.org>, Janne Grunau
	<j@...nau.net>, Suzuki K Poulose <suzuki.poulose@....com>, James Clark
	<james.clark@...aro.org>, Jinjie Ruan <ruanjinjie@...wei.com>, "Alexandru
 Elisei" <alexandru.elisei@....com>
Subject: Re: [PATCH v4 16/26] genirq: Allow per-cpu interrupt sharing for
 non-overlapping affinities

On Mon, 20 Oct 2025 13:29:33 +0100
Marc Zyngier <maz@...nel.org> wrote:

> Interrupt sharing for percpu-devid interrupts is forbidden, and
> for good reasons. These are interrupts generated *from* a CPU and
> handled by itself (timer, for example). Nobody in their right mind
> would put two devices on the same pin (and if they have, they get to
> keep the pieces...).
> 
> But this also prevents more benign cases, where devices are connected
> to groups of CPUs, and for which the affinities are not overlapping.
> Effectively, the only thing they share is the interrupt number, and
> nothing else.
> 
> Let's tweak the definition of IRQF_SHARED applied to percpu_devid
> interrupts to allow this particular case. This results in extra
> validation at the point of the interrupt being setup and freed,
> as well as a tiny bit of extra complexity for interrupts at handling
> time (to pick the correct irqaction).
> 
> Tested-by: Will Deacon <will@...nel.org>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>