linux-kernel - Re: [PATCH v3 3/3] PCI: dwc: Enable MSI affinity support

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Message-ID: <255713ca-bf91-4f7e-8df2-33b7b614a1bb@nvidia.com>
Date: Mon, 26 Jan 2026 22:07:02 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Thomas Gleixner <tglx@...nel.org>, Radu Rendec <rrendec@...hat.com>,
 Manivannan Sadhasivam <mani@...nel.org>
Cc: Daniel Tsai <danielsftsai@...gle.com>, Marek Behún
 <kabel@...nel.org>, Krishna Chaitanya Chundru <quic_krichai@...cinc.com>,
 Bjorn Helgaas <bhelgaas@...gle.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Wilczyński <kwilczynski@...nel.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>, Jingoo Han
 <jingoohan1@...il.com>, Brian Masney <bmasney@...hat.com>,
 Eric Chanudet <echanude@...hat.com>,
 Alessandro Carminati <acarmina@...hat.com>, Jared Kangas
 <jkangas@...hat.com>, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3 3/3] PCI: dwc: Enable MSI affinity support

Hi Thomas,

On 26/01/2026 07:59, Thomas Gleixner wrote:
> On Thu, Jan 22 2026 at 18:31, Radu Rendec wrote:
>> The CPUs are taken offline one by one, starting with CPU 7. The code in
>> question runs on the dying CPU, and with hardware interrupts disabled
>> on all CPUs. The (simplified) call stack looks like this:
>>
>> irq_migrate_all_off_this_cpu
>>    for_each_active_irq
>>      migrate_one_irq
>>        irq_do_set_affinity
>>          irq_chip_redirect_set_affinity (via chip->irq_set_affinity)
>>
>> The debug patch I gave you adds:
>>   * a printk to irq_chip_redirect_set_affinity (which is very small)
>>   * a printk at the beginning of migrate_one_irq
>>
>> Also, the call to irq_do_set_affinity is almost the last thing that
>> happens in migrate_one_irq, and that for_each_active_irq loop is quite
>> small too. So, there isn't much happening between the printk in
>> irq_chip_redirect_set_affinity for the msi irq (which we do see in the
>> log) and the printk in migrate_one_irq for the next irq (which we don't
>> see).
> 
> This doesn't make any sense at all. irq_chip_redirect_set_affinity() is
> only accessing interrupt descriptor associated memory and the new
> redirection CPU is the same as the previous one as the mask changes from
> 0xff to 0x7f and therefore cpumask_first() yields 0 in both cases.
> 
> According to the provided dmesg, this happens on linux-next.
> 
> Jon, can you please validate that this happens as well on
> 
>       git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq/msi


I tried this branch and I see suspend failing with that branch too. If I 
revert this change on top of your branch or -next, I don't see any 
problems.

Thanks
Jon

-- 
nvpublic