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

[Gleb Natapov]

On Thu, Oct 08, 2009 at 06:29:53PM +0200, Avi Kivity wrote:
> On 10/08/2009 06:22 PM, 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?
> 
> It may be done differently (for example, selecting the cpu to
> deliver the interrupt to), but as the guest cannot rely on the
> differences, there's no need to save the state that can cause these
> differences.
> 
So suppose I have simple watchdog device that required to be poked every
second, otherwise it resets a computer. On migration we have to migrate
time elapsed since last poke, but if device doesn't expose it to
software in any way you are saying we can recreate is some other way?

--
                        Gleb.