On 09/17/2012 08:05 PM, Jan Kiszka wrote:
> On 2012-09-17 19:46, Gilles Chanteperdrix wrote:
>> ipipe_end is a nop when called from primary domain, yes, but this is not
>> very different from edge irqs. Also, fasteoi become a bit like MSI: in
>> the same way as we can not mask MSI from primary domain, we should not
>> mask IO-APIC fasteoi irqs, because the cost is too prohibitive. If we
>> can live with MSI without masking them in primary mode, I guess we can
>> do the same with fasteoi irqs.
>
> MSIs are edge triggered, fasteois are still level-based. They require
> masking at the point you defer them - what we do and what Linux may even
> extend beyond that. If you mask them by raising the task priority, you
> have to keep it raised until Linux finally handled the IRQ.
Yes.
> Or you
> decide to mask it at IO-APIC level again.
We do not want that.
> If you keep the TPR raised,
> you will block more than what Linux wants to block.
The point is that if the TPR keeps raised, it means that primary domain
has preempted Linux, so, we want it to keep that way. Otherwise the TPR
gets lowered when Linux has handled the interrupt.
A week-end of testing made me sure of one thing: it works. I assure you.
>
> Jan
>
--
Gilles.
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