Re: [Xen-devel] Re: [PATCH] xen: events: do not unmask polled ipis on restore.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2010-10-29 at 18:52 +0100, Ian Campbell wrote:
> 
> 
> > I wonder if this shouldn't be done at the irq layer, based on the 
> > desc's irq state?
> 
> It looks like suspend_device_irqs/resume_device_irqs takes care of the
> mask/unmask element of restore for us (including unmasking irqs marked
> with IRQF_NO_SUSPEND when appropriate). So we know the evtchn will be
> masked on save and Xen brings us back up with all evtchns masked so
> all restore_cpu_ipis needs to do is the rebinding of ipi to evtchn? 

A naive attempt at this (i.e. remove the unmask_evtchn calls from
restore_cpu_{ipis,virqs}) doesn't work, since we (unsurprisingly) end up
with some evtchn's remaining masked...

I'll take another look. It's possible that this will also interact with
Stefano's changes to the irq_chip interactions since he is trying to
ensure that our callbacks have the semantics expected by the core.

BTW, do you think the polled-only IPI are unusual/special enough to have
their own interface with the event channel core (e.g.
bind_polled_ipi_to_irq) even if the internals of the implementation
doesn't turn into anything particularly unusual?

Ian.


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