Re: [Xen-devel] [PATCH 1/4] xen/arm: gic: Ensure we have an ISB between ack and do_IRQ()

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

Hello Julien,


On 19.11.18 18:42, Julien Grall wrote:
> There are no issue about processing IRQs before the syncs. It is the 
> same as if an IRQ was raised from ila different pCPUs.
> So why do you need that?
From my understanding of gic-vgic code (old vgic), for the IRQs 
targeting the `current` vcpu, it leads to a faster processing under 
interrupts storm conditions. If it was all LRs set on previous switch to 
a guest, a the IRQ will have a chance to go directly to LR instead of 
setting on lr_pending queue. Also inflight_irqs queue have a chance to 
be shorter to insert.

Moreover, maybe you can explain me, what's the point of interrupts 
enabling before for `do_IRQ()` call? Those interrupts would be grabbed 
and processed anyway, during run through the loop in `gic_interrupt()`. 
So I see the only outcome of interrupts enabling - spending more time 
for context switches.

--
Sincerely,
Andrii Anisov.


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel