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

[Paul Brook <paul@codesourcery.com>]

> On Fri, 2011-07-01 at 21:59 +0100, Paul Brook wrote:
> > > On Fri, 1 Jul 2011 18:03:01 +0100
> > > 
> > > Paul Brook <paul@codesourcery.com> wrote:
> > > > Basically you should start by implementing full emulation of a device
> > > > with similar characteristics to the one you want to passthrough.
> > > 
> > > That's not going to happen.
> > 
> > Why is your device so unique? How does it interact with the guest system
> > and what features does it require that doen't exist in any device that
> > can be emulated?
> 
> Do you guys only support PCI pass-through by doing full emulation of the
> all possible supported PCI devices first ? :-)

Absolutely not.  My point is that dynamic (user-driven) device creation is 
effectively a prerequisite for a passthrough device.

If you just want to make a very specific use-case then this doesn't need any 
code in qemu at all.  We just make the user provide the device tree 
themselves. If it doesn't match then they loose.  If you do choose an ugly 
qemu then the changes are it'll be changed/removed once we do dyamic device 
creation properly.  There have already been discussions about dynamic device 
creation, so this this isn't completely hypothetical.

If you integrate it properly, then you need to realise then there's a fair 
chunk of infrastructure and user interface required.  Most of which has 
nothing to do with device passthrough.  Trying to implement both at the same 
time is just going to cause confusion and complicate things.  It's already a 
hard problem, combining it with something else is just going to cause you and 
everyone else even more pain.

Paul