Re: [Qemu-devel] [PATCH v5 06/16] apic: Introduce backend/frontend infrastructure for KVM reuse

[Anthony Liguori]

On 12/20/2011 03:56 AM, Avi Kivity wrote:
> On 12/20/2011 02:38 AM, Anthony Liguori wrote:
> > > That was v1 of my patches. Avi didn't like it, I tried it like this, and
> > > in the end I had to agree. So, no, I don't think we want such a model.
> >
> >
> > Yes, we do :-)
> >
> > The in-kernel APIC is a different implementation of the APIC device.
> > It's not an "accelerator" for the userspace APIC.
>
> A different implementation but not a different device.  Device == spec.

If it was hardware, it'd be a fully compatible clone.  The way we would model 
this is via inheritance.

Regards,

Anthony Liguori

> > All that you're doing here is reinventing qdev.  You're defining your
> > own type system (APICBackend), creating a new regression system for
> > it, and then defining your own factory function for creating it
> > (through a qdev property).
> >
> > I'm struggling to understand the reason to avoid using the
> > infrastructure we already have to do all of this.
>
> Not every table of function pointers has to be done through qdev (not
> that I feel strongly about this - only that there is just one APIC device).