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.