Re: [Xen-devel] [PATCH 1/4] xen/events: Clear cpu_evtchn_mask before resuming

[Boris Ostrovsky]

On 04/29/2015 01:59 PM, David Vrabel wrote:
> On 29/04/15 17:54, Boris Ostrovsky wrote:
> > On 04/29/2015 12:32 PM, David Vrabel wrote:
> > > On 28/04/15 19:29, Boris Ostrovsky wrote:
> > > > On 04/28/2015 12:28 PM, David Vrabel wrote:
> > > > >    From the commit log the evtchn_2l_resume() fucntion that's added
> > > > > sounds
> > > > > like it fixes the problem on its own?
> > > > It in fact makes this problem worse since now that cpu_evtchn_mask is
> > > > cleared during resume we cannot process the interrupt anymore in
> > > > evtchn_2l_handle_events(): irqs have to be bound to a cpu in order for
> > > > an interrupt to be processed.
> > > Perhaps evtchn_2l_resume() should set the local cpu mask for any bound
> > > event channels? And then you wouldn't need IRQ_MOVE_PCNTX.
> > But then (at least in 2-level case) more than one VCPUs may pick the
> > same interrupt, won't they? Because the local cpu mask is what tells a
> > VCPU that it is allowed to claim an interrupt.
>
> We know that all event channels at this point are on VCPU0 (right?) so
> we only set the bit in that VCPU's mask.

This is pretty much what I was suggesting since setting the mask is done 
via bind_evtchn_to_cpu(). Except that I also want to call 
EVTCHNOP_bind_vcpu before that, just in case.

-boris
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