Re: [Qemu-devel] Re: [PATCH 0/9] Virtio cleanups

[Anthony Liguori]

On 03/18/2010 11:36 AM, Gerd Hoffmann wrote:
>   Hi,
>
> > But I still think that this is independent that VirtIO being 1st (or
> > not) memer of VirtIOBlock.
>
> There is no strong reason for this other than memory allocation.  As 
> long as virtio_common_init() does the allocation there is no way 
> around VirtIODevice being the first member.  If this changes (and we 
> must change it if we want embed VirtIODevice and superclasses into 
> other structs) no reason is left.
>
> Just changing it for the snake of change isn't a good reason either. 
> But if it helps cleaning the code we can change it without running 
> into trouble.  You can't cast VirtIODevice to VirtIOBlock any more, 
> but you don't really want to anyway for type checking reasons.

It's almost certainly not worth the effort, but the proper way to model 
is it probably to have a VirtioIOPCIBus that is a PCIDevice.  The 
VirtIOPCIBus then creates a single VirtIODevice.  The VirtIODevice would 
then take a VirtioTransport which would be implemented as part of the 
VirtIOPCIBus.

Regards,

Anthony Liguori

> cheers,
>   Gerd