linux-kernel - Re: [PATCH v2 1/2] genirq: Retain depth for managed IRQs across CPU hotplug

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Message-ID: <aEsfJj35W7HQlTOH@google.com>
Date: Thu, 12 Jun 2025 11:40:38 -0700
From: Brian Norris <briannorris@...omium.org>
To: Aleksandrs Vinarskis <alex.vinarskis@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Tsai Sung-Fu <danielsftsai@...gle.com>,
	Douglas Anderson <dianders@...omium.org>,
	linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH v2 1/2] genirq: Retain depth for managed IRQs across CPU
 hotplug

On Wed, Jun 11, 2025 at 12:08:16PM -0700, Brian Norris wrote:
> On Wed, Jun 11, 2025 at 08:56:40AM +0200, Aleksandrs Vinarskis wrote:
> > Yes. Dell XPS 9345 is arch/arm64/boot/dts/qcom/x1e80100.dtsi based,
> > and Asus Zenbook A14 is arch/arm64/boot/dts/qcom/x1p42100.dtsi based,
> > which is a derivative but has a slightly different PCIe setup. So far
> > both laptops would behave in the same ways.
> 
> Thanks. So that's what I suspected, a DWC/pcie-qcom PCIe driver, and
> seemingly standard NVMe on top. pcie-qcom doesn't seem to do anything
> weird regarding MSIs or affinity, [...]

For the record, I was reminded that DWC/pcie-qcom does not, in fact,
support irq_chip::irq_set_affinity(), which could perhaps be a unique
factor in his systems' behavior.

> > > Thanks for the testing. I've found a few problems with my proposed
> > > patch, and I've come up with the appended alternative that solves them.
> > > Could you give it a try?
> > 
> > Just tested, and it appears to solve it, though I see some errors on
> > wakeup that I don't remember seeing before. I will test-drive this
> > setup for a day to provide better feedback and confirm if it is
> > related to the fixup or not.
> 
> That's promising, I think. Do feel free to forward info if you think
> there's still a problem though. I'll await your feedback before spinning
> patches.

Alex sent some private feedback, and from what I could tell, there was
nothing concerning. The "new" errors are simply about a wakeup attempt
interrupting the CPU offlining process, which I believe is normal
behavior depending on the wakeup actvity on his laptop (e.g., input
devices).

I've submitted my fixes here:

Subject: [PATCH 6.16 0/2] genirq: Fixes for CPU hotplug / disable-depth regressions
https://lore.kernel.org/lkml/20250612183303.3433234-1-briannorris@chromium.org/

Brian