> A VirtIOBlock device cannot be a VirtIODevice while being a > VirtIOPCIProxy (proxy is a poor name, btw). > > It really ought to be: > > DeviceState -> VirtIODevice -> VirtIOBlock > > and: > > PCIDevice -> VirtIOPCI : implements VirtIOBus > > The interface between the VirtIODevice and VirtIOBus is the virtio > transport. > > The main reason a separate bus is needed is the same reason it's needed > in Linux. VirtIOBlock has to be tied to some bus. It cannot be tied to > the PCI bus without having it be part of the implementation detail. > Introducing another bus type fixes this (and it's what we do in the > kernel).
Why does virtio need a device state and bus at all? Can't it just be an internal implementation interface, which happens to be used by all devices that happen to exposed a block device over a virtio transport? If you have a virtio bus then IMO the PCI bridge device should be independent of the virtio device that is connected to it. Paul
