Re: [patch 27/30] xen/events: Only force affinity mask for percpu interrupts

From: Jürgen Groß
Date: Fri Dec 11 2020 - 01:21:51 EST


On 11.12.20 00:20, boris.ostrovsky@xxxxxxxxxx wrote:

On 12/10/20 2:26 PM, Thomas Gleixner wrote:
All event channel setups bind the interrupt on CPU0 or the target CPU for
percpu interrupts and overwrite the affinity mask with the corresponding
cpumask. That does not make sense.

The XEN implementation of irqchip::irq_set_affinity() already picks a
single target CPU out of the affinity mask and the actual target is stored
in the effective CPU mask, so destroying the user chosen affinity mask
which might contain more than one CPU is wrong.

Change the implementation so that the channel is bound to CPU0 at the XEN
level and leave the affinity mask alone. At startup of the interrupt
affinity will be assigned out of the affinity mask and the XEN binding will
be updated.


If that's the case then I wonder whether we need this call at all and instead bind at startup time.

This binding to cpu0 was introduced with commit 97253eeeb792d61ed2
and I have no reason to believe the underlying problem has been
eliminated.


Juergen

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