On Thu, Dec 10 2020 at 18:20, boris ostrovsky wrote:

On 12/10/20 2:26 PM, Thomas Gleixner wrote:

quoted

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.

I was wondering about that, but my knowledge about the Xen internal
requirements is pretty limited. The current set at least survived basic
testing by Jürgen.

Thanks,

        tglx