Re: [Qemu-devel] Re: [PATCH v2 3/9] provide in-kernel ioapic

[Glauber Costa]

On Thu, Oct 08, 2009 at 06:22:48PM +0200, Gleb Natapov wrote:
> On Thu, Oct 08, 2009 at 06:17:57PM +0200, Avi Kivity wrote:
> > On 10/08/2009 06:07 PM, Jamie Lokier wrote:
> > >Haven't we already confirmed that it *isn't* just an ioapic accelerator
> > >because you can't migrate between in-kernel iopic and qemu's ioapic?
> > 
> > We haven't confirmed it.  Both implement the same spec, and if you
> > can't migrate between them, one of them has a bug (for example, qemu
> > ioapic doesn't implement polarity - but it's still just a bug).
> > 
> Are you saying that HW spec (that only describes software visible behavior)
> completely defines implementation? No other internal state is needed
> that may be done differently by different implementations?
Most specifications leaves a lot as implementation specific.

It's not hard to imagine a case in which both devices will follow the spec 
correctly,
(no bugs involved), and yet differ in the implementation.