"Michael S. Tsirkin" [off-list ref] writes:

On Thu, Oct 11, 2012 at 10:33:31AM +1030, Rusty Russell wrote:

quoted

OK.  Well, Anthony wants qemu to be robust in this regard, so I am
tempted to rework all the qemu drivers to handle arbitrary layouts.
They could use a good audit anyway.

I agree here. Still trying to understand whether we can agree to use
a feature bit for this, or not.

I'd *like* to imply it by the new PCI layout, but if it doesn't work
we'll add a new feature bit.

I'm resisting a feature bit, since it constrains future implementations
which could otherwise assume it.

quoted

This would become a glaring exception, but I'm tempted to fix it to 32
bytes at the same time as we get the new pci layout (ie. for the virtio
1.0 spec).

But this isn't a virtio-pci only issue, is it?
qemu has s390 bus with same limmitation.
How can we tie it to pci layout?

They can use a transport feature if they need to, of course.  But
perhaps the timing with ccw will coincide with the fix, in which they
don't need to, but it might be a bit late.

Cornelia?

Cheers,
Rusty.