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Re: [Xen-devel] [RFC 05/19] xen/arm: Release IRQ routed to a domain when it's destroying

On 18/06/14 19:48, Stefano Stabellini wrote:
I can add an ASSERT(irq_get_domain(desc)->is_dying) here...

The ASSERT is a good idea.

Given that the domain has been descheduled, gic_update_one_lr won't work
but you can read the saved lr (pending_irq->lr) from v->arch.gic_lr.
You can obtain the target vcpu calling vgic_get_target_vcpu.
You only need to write to GICC_DIR if (gic_lr & 
> gic_remove_from_queues should still work.

Unless we assume a virq == pirq we can't retrieve the irq_pending structure via an irq_desc. Also this may has been free earlier, even tho for now SPIs are stored directly in arch_domain.

I prefer to keep the check IRQ_INPROGRESS, and call gic_update_lrs before unscheduled the VCPU. BTW, is it the case?

Also I wonder if you need to call gic_reset_guest_irq before
The specification states (4.3.5):

'Disabling an interrupt only disables the forwarding of the interrupt
from the Distributor to any CPU interface. It does not prevent the
interrupt from changing state, for example becoming pending, or active
and pending if it is already active.'

So from the text above I think that EOIing an interrupt that has been
disabled at the GICD level should work, but it is not 100% clear.

On oneshot IRQ, Linux is disabling the IRQ before EOIing it. This will avoid to receive spurious interrupt.

Here we need to do the same thing otherwise we may receive spurious interrupt.


Julien Grall

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