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

[Marc Zyngier]

On 2020-08-13 09:08, Thomas Gleixner wrote:
> Yunfeng Ye <yeyunfeng@xxxxxxxxxx> 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?