Re: [PATCH 4/4][RFC] kvm: eoi_eventfd

[Avi Kivity <avi@redhat.com>]

On 06/24/2012 06:02 PM, Alex Williamson wrote:
> On Sun, 2012-06-24 at 15:56 +0300, Avi Kivity wrote:
>> On 06/23/2012 01:16 AM, Alex Williamson wrote:
>> > I think we're probably also going to need something like this.
>> > When running in non-accelerated qemu, we're going to have to
>> > create some kind of EOI notifier for drivers.  VFIO can make
>> > additional improvements when running on KVM so it will probably
>> > make use of the KVM_IRQFD_LEVEL_EOI interface, but we don't
>> > want to have a generic EOI notifier in qemu that just stops
>> > working when kvm-ioapic is enabled.
>> 
>> Why?
> 
> Hmm, I must be missing something or not describing it correctly, because
> it seems obvious.  

I have not exhausted this quarter's quota of stupid questions yet.

> If we create a dependency in qemu of needing to know
> when an eoi occurs and notifier a driver and have no way to fulfill that
> dependency when running on kvm... that'd be bad, right?  I don't want to
> assume that every consumer of such an interface would prefer to make use
> of an irqfd.  Not sure if that answers your question though.  Thanks,

I meant, what scenario do you have in mind where we want the EOI
notifier while running with kvm-irqchip enabled?  Perhaps I phrased my
question a bit too tersely.

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