Re: [PATCH v2 3/4] KVM: ioapic: extract body of kvm_ioapic_set_irq

[Radim KrÄmÃÅ]

2014-03-23 09:44+0100, Paolo Bonzini:
> Il 21/03/2014 19:58, Radim KrÄmÃÅ ha scritto:
> >>> +	/*
> >>> +	 * Return 0 for coalesced interrupts; for edge-triggered interrupts,
> >>> +	 * this only happens if a previous edge has not been delivered due
> >>> +	 * do masking.  For level interrupts, the remote_irr field tells
> >          (^ to)
> >>> +	 * us if the interrupt is waiting for an EOI.
> >
> >How do we know we haven't delivered an edge-triggered interrupt when
> >ioapic_service() always clears this IRR bit?
> 
> We know we have at least delivered it to the local APIC(s).  If it
> is masked in the ioredirtbl, ioapic_service doesn't clear the IRR.

I see, LAPIC can't "refuse" an interrupt, so kvm_irq_delivery_to_apic()
won't (mustn't) fail. (The code looks fragile if it returned -1.)

Thanks.
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