On Tue, 13 Nov 2012 15:27:57 +0100
KONRAD Frédéric <fred.kon...@greensocs.com> wrote:
> To fix this, an idea is to use a new qbus named VirtioBus to link virtio-pci
> or virtio-mmio with all the virtio backend ( VirtioDevice ). So
> "virtio-pci" and
> "virtio-mmio" will have a VirtioBus.
Just to spell this out:
We'd go from
system bus
-> virtio transport bridge dev (virtio-xxx-bridge)
-> virtio transport bus (virtio-xxx-bus)
-> virtio transport dev (virtio-<type>-xxx)
to
system bus
-> virtio transport bridge dev (virtio-bridge-xxx)
-> virtio bus (virtio-bus-xxx)
-> virtio dev (virtio-<type>-xxx)
?
Would this also mean we could have several virtio-busses with different
transports?
>
> To do that we will do the following things in the right order :
> * Introduce a new VirtioBus ( same way as scsi-bus.c ), with
> VirtIODevice
> interface :
> -> callback to completely abstract the VirtioDevice from
> VirtioPCI.
> -> for the queue, load/save the queue/config, features, ...,
> other ?
> * Add a VirtioBus to the VirtioPCIProxy. ( virtio-pci.c ) :
> -> moving all to the newer callback.
> * For each of the virtio-device : ( virtio-x.c )
> -> making a separate class for virtio-x which is a VirtioDevice.
> -> making a virtio-x-pci which has a virtio-x.
> * Create virtio-mmio ( virtio-mmio.c ).
>
> Is it the right approach ? Do I miss something ?
What of the alias handling? Can this be killed once everything has been
converted?
>
> When it will work, we must be sure of :
>
> -> migration compatibility.
> -> not breaking the s390 transport.
> -> compatibility with s390 ccw.
There shouldn't be major problems rebasing the virtio-ccw code on top
of this rework (though I'd probably try to keep the basic channel I/O
support separate from this patchset).
