linux-kernel - Re: [PATCH] genirq/affinity: show managed irq affinity correctly

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Date:   Sat, 15 Aug 2020 15:29:41 +0100
From:   Marc Zyngier <maz@...terjones.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Yunfeng Ye <yeyunfeng@...wei.com>
Cc:     Shiyuan Hu <hushiyuan@...wei.com>,
        Hewenliang <hewenliang4@...wei.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genirq/affinity: show managed irq affinity correctly

On 2020-08-13 09:08, Thomas Gleixner wrote:
> Yunfeng Ye <yeyunfeng@...wei.com> writes:

[...]

> You are looking at the wrong file. /proc/irq/$IRQ/smp_affinity* is the
> possible mask. If you want to know to which CPU an interrupt is affine
> then look at /proc/irq/$IRQ/effective_affinity*
> 
> If effective_affinity* is not showing the correct value, then the irq
> chip affinity setter is broken and needs to be fixed.

In order to reassure myself that nothing was untoward in GIC-land,
I went in and looked at an ITS-based VM running whatever is in
Linus' tree today. I see the effective affinity being correctly
setup, and being as expected a subset of the affinity. This is
without isolcpu though.

In any case, I'd be interested in understanding what this patch is
trying to solve, really.

         M.
-- 
Who you jivin' with that Cosmik Debris?