Re: [Xen-devel] [query] gic_set_lr always uses maintenance Interrupt

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 7 Nov 2013, Mj Embd wrote:
> On Thu, Nov 7, 2013 at 10:18 PM, Stefano Stabellini
> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Thu, 7 Nov 2013, Mj Embd wrote:
> >> On Thu, Nov 7, 2013 at 5:07 PM, Stefano Stabellini
> >> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >> > Please don't top post as it makes it harder to follow the conversation.
> >> >
> >> > On Thu, 7 Nov 2013, Mj Embd wrote:
> >> >> A few thoughts are circling around my mind, don't know how much
> >> >> interrupt latency would it have.
> >> >>
> >> >> Rather than the hypervisor entry when guest does EOI, a late / lazy
> >> >> checkin on LR's can be done
> >> >>  on next hypervisor entry by
> >> >> a) guest doing something and trapping to hypervisor
> >> >> b) schedular timer in hypervisor
> >> >>
> >> >> What do you think on this...
> >> >
> >> > It might work.
> >> > One key issue is how to identify that the guest EOIed a particular irq
> >> > and henceforth the corresponding LR can be reused.
> >> [mj] I believe that GICH_ELSR0/1 can be read anytime to get the status.
> >>
> >> > I hope that the status bits in the LR register reflect this condition.
> >> > Maybe the status becomes 00 invalid after the guest does EOI? Otherwise
> >> [mj] The state in LR is marked invalid by Virtual CPU interface.
> >
> > Right. In that case the lazy LR clearance should work.
> >
> [mj] I have started analysing it, can i send a patch in near future

Do you have an update on this?
Did you manage to write such a patch?

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel