Re: [Xen-devel] [PATCH] xen-evtchn: Bind dyn evtchn:qemu-dm interrupt to next online VCPU

[Anoob Soman]

On 05/06/17 16:32, Boris Ostrovsky wrote:
> I believe we do need to take affinity into consideration even if the
> chance that it is non-default is small.

Agreed.

> I am not opposed to having bind_last_selected_cpu percpu, I just wanted
> to understand the reason better. Additional locking would be a downside
> with a global so if you feel that percpu is worth it then I won't object.

If affinity == cpu_online_mask, then percpu will give a better spread. 
atomic set/get can be used, if we want to use a global variable, but I 
think it will be more random than percpu.

> > Yes, you are correct. .irq_set_affinity pretty much does the same thing.
> >
> > The code will now looks like this.
> > raw_spin_lock_irqsave(lock, flags);
> > percpu read
> > select_cpu
> > percpu write
> > xen_rebind_evtchn_to_cpu(evtchn, selected_cpu)
> > raw_spin_unlock_irqsave(lock, flags);
> (BTW, I just noticed --- you don't need to initialize desc)

Sorry, I didn't get it. Which desc doesn't need init ?

-Anoob