Rusty Russell wrote:
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.
I'm not sure what's best, maybe this can help:
With the virtio_find_driver you need to place all virtio drivers under
the same pci device or suggest new mapping.
Using Arnd's solution (actually I implemented it for KVM before the new
patch set) and 1-1 mapping for pci and virtio
devices makes life simpler.
Dor.
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