Re: [Qemu-devel] [RFC PATCH v6 0/6] Virtio refactoring.

[KONRAD Frédéric]

On 17/12/2012 16:45, Michael S. Tsirkin wrote:
> On Fri, Dec 07, 2012 at 02:32:29PM +0100, address@hidden wrote:
> > From: KONRAD Frederic <address@hidden>
> >
> > You can clone that from here :
> > git.greensocs.com/home/greensocs/git/qemu_virtio.git virtio_refactoring_v6
> >
> > The problem with the last RFC v5 was that virtio-blk refactoring broke
> > virtio-blk-pci device ( SEGFAULT ). So I modify this last step to fix that
> > issue.
> >
> > In order to not break anything, I think we have to refactor virtio-pci-blk in a
> > next step then add a supplementary step which clean virtio-blk
> > ( eg : fix the cast ).
> >
> > Does it make sense ?
> I am yet to go over the patches but I did try to read
> previous discussion and I am still puzzled about the motivation. One of
> the previous messages mentioned this is to allow virtio-mmio.
Yes, the main goal is to have the choice of the transport device.

eg :

-device virtio-pci,id=transport1 -device virtio-scsi,bus=transport1

or

-device virtio-mmio,id=transport1 -device virtio-scsi,bus=transport1

That's why anthony suggest to create a virtio-bus to connect transport 
to device.

so all virtio-x devices must be created. And virtio-pci must have a 
virtio-bus.

Then to keep compability with the older version virtio-x-pci must create 
virtio-pci and virtio-x.

> Is the point to allow virtio-mmio?  Why can't virtio-mmio be just
> another bus, like a pci bus, and another binding, like the virtio-pci
> binding?
Do you mean something like creating all virtio device like virtio-mmio-x ?

> Is the issue that bindings are not devices?
> I'm sending a patchset to use DeviceState as binding pointer -
> will this address the issue?
The issue is that all is linked, and here the virtio-blk refactoring breaks
virtio-blk-pci and virtio-blk-s390 devices as they didn't use QOM.
But the newer version ( V7 ) didn't break anything.

> If this was covered but I missed this I'll be thankful for
> pointers if any.
> Thanks,