On Tue, Jun 19, 2018 at 12:54:53PM +0200, Cornelia Huck wrote:

Sorry about dragging mainframes into this, but this will only work for
homogenous device coupling, not for heterogenous. Consider my vfio-pci
+ virtio-net-ccw example again: The guest cannot find out that the two
belong together by checking some group ID, it has to either use the MAC
or some needs-to-be-architectured property.

Alternatively, we could propose that mechanism as pci-only, which means
we can rely on mechanisms that won't necessarily work on non-pci
transports. (FWIW, I don't see a use case for using vfio-ccw to pass
through a network card anytime in the near future, due to the nature of
network cards currently in use on s390.)

That's what it boils down to, yes.  If there's need to have this for
non-pci devices, then we should put it in config space.
Cornelia, what do you think?

-- 
MST