Re: [PATCH 1/6] virtio interace

Rusty Russell
2007-09-23T08:33:51Z

On Sat, 2007-09-22 at 12:01 +0200, Arnd Bergmann wrote:
> On Saturday 22 September 2007, Rusty Russell wrote:
> > But now each virtio device has two "struct device"s, not one. And
> > you've made up a fictional bus to do it.
> >
> > Yet for PCI systems, it really is a PCI device; exposing a second bus to
> > userspace just because we put a layer in our implementation is poor
> > form.
> >
> > Perhaps this is the easiest way of doing it. But it's still wrong.
>
> I think it's just a matter of perspective. In the model I'm advocating,
> the PCI device is not the same as the virtio device but rather a virtio
> host bridge, very much like USB or SATA works.
>
> We could easily have multiple virtio devices behind one PCI device, but
> since virtual PCI devices are cheap, a one-to-one mapping makes sense
> for simplicity.

This is still retro-justification. The simplest way for PCI systems to
represent a virtio device as a PCI device; this makes life easy for any
guest OS.

I just know we're going to regret this...
Rusty.