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

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.

> 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


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