Re: [Qemu-devel] device assignment for embedded Power

[Anthony Liguori]

On 07/01/2011 12:03 PM, Paul Brook wrote:
> > > irq[0].guest_irq = "10"
> > >
> > > This should be independent of anything to do with device tree.  This
> > > would be useful for x86 too to assign platform devices (like the HPET).
> >
> > That's fine, as long as there's something layered on top of it for the case
> > where we do want to reference something in the device tree.
> >
> > However, we'll need to address the question of what it means to say "irq
> > 10" -- outside of PC-land there often isn't a global IRQ numberspace that
> > isn't a fiction created by some software layer.  Addressing this is one of
> > the device tree's strengths.
>
> That's an entirely separate problem, thoug probably a prerequisite.
>
> Basically you should start by implementing full emulation of a device with
> similar characteristics to the one you want to passthrough.

If you want to model interrupt remapping, you have to model device 
relationships.  If you cannot express the bus hierarchy/relationship 
then you cannot sanely model interrupt remapping.

You can only really ever think about passing through an entire subtree 
of the device hierarchy.  You can't have a partial subtree with some 
crazy hack logic to explain how the physical layer may remap interrupts. 
 That's just asking for pain.

Regards,

Anthony Liguori