[Qemu-devel] Re: [RFC PATCH 4/5] APIC/IOAPIC EOI callback

[Avi Kivity]

On 07/11/2010 09:30 PM, Avi Kivity wrote:
> > Registering an eventfd for the eoi seems like a reasonable alternative.
>
> I'm worried about that racing (with what?)

I don't think there's a problem.

First, the EOI message is itself asynchronous.  While the write to the 
local APIC is synchronous, effects on the rest of the system are 
effected using an APIC message, which travels asynchronously.

Second, a component that needs timely information doesn't have to wait; 
it can read the eventfd and be sure it has seen all EOIs up to now.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.