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.
After some discussion with Thomas on IRC and xen-devel archaeology the result is: this will be needed especially for systems running on a single vcpu (e.g. small guests), as the .irq_set_affinity() callback won't be called in this case when starting the irq. Juergen
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