Re: [Xen-devel] [PATCH v2 2/5] arm: implement vcpu_mark_events_pending

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 24 Feb 2012, David Vrabel wrote:
> On 24/02/12 10:33, Ian Campbell wrote:
> > On Thu, 2012-02-23 at 18:21 +0000, Stefano Stabellini wrote:
> >> Implement vcpu_mark_events_pending using the vgic to inject INT 63, that
> >> we reserve for Xen usage.
> > 
> > Does this require a trap when the guest acks or EOIs this interrupt?
> > What about maintenance interrupts arising from injecting this?

Yes, we would get a maintenance interrupt in the hypervisor every time
the guest EOI's it.


> > Might we want to instead inject this interrupt as an SGI, so that it
> > appears as a per-VCPU interrupt?
> 
> I don't think it's possible to register a SGI handler in Linux
> currently.  The mapping of IRQ numbers to GIC interrupts skips over the
> SGIs.  This would be easy to fix I think.

A per-vcpu interrupt that doesn't require an EOI would be ideal, however
like David wrote, it is not possible to register an SGI handler in Linux
at the moment. I'll give it a look though.

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