Re: [Qemu-devel] Can we improve virtio data structures with QOM?

[Anthony Liguori]

On 05/31/2012 12:28 AM, Markus Armbruster wrote:
> Stefan Hajnoczi<address@hidden>  writes:
>
> > On Wed, May 30, 2012 at 1:01 PM, Markus Armbruster<address@hidden>  wrote:
> > > Ordinary device models have a single state struct.  The first member is
> > > a DeviceState or a specialization of DeviceState, e.g. a PCIDevice.
> > > Simple enough.
> >
> > I think Evgeny's virtio mmio patches change all this.  In the recent
> > virtio-pci thread we were discussing how the virtio transport (mmio,
> > pci) and virtio devices (net, blk, etc) fit together.  The email
> > thread is "Virtio-pci issues" from Evgeny Voevodin
> > <address@hidden>.
>
> Thanks for the pointer.
>
> It's been a couple of weeks.  Evgeny, are you still pursuing this?
>
> > It probably makes sense to first merge Evgeny's virtio refactoring and
> > then ensure it's nicely mapped to QOM.
>
> Yes, no good attempting to do too much in one series.  Nevertheless,
> having a sufficiently developed idea of the final state in mind helps.

Basically, it should look like:

VirtioPCIDevice is-a PCIDevice

VirtioPCIDevice has-a link<VirtioDevice>

VirtioDevice is-a DeviceState

VirtioBlk is-a VirtioDevice
VirtioNet is-a VirtioDevice
...

VirtioPCIBlk is-a VirtioPCIDevice
VirtioPCIBlk has-a child<VirtioBlk>

This gives us backwards compat while also providing a cleaner model. 
VirtioPCIBlk et al would be deprecated eventually (but not any time soon).

Regards,

Anthony Liguori

>