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

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
>> > I can't really see how we could make it work.
>> I am planning to stop using gmail, it makes you top post as it hides
>> everything.
> Yes, I use gmail for my personal email and I find it very inconvenient
> for anything but simple messages. Thank you.


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