[Xen-devel] Re: [RFC PATCH] libxl: basic virtio disk / nic configuration support.

[Wei Liu <liuw@xxxxxxxxx>]

On Thu, Jul 28, 2011 at 02:05:08PM +0100, Stefano Stabellini wrote:
> On Thu, 28 Jul 2011, Wei Liu wrote:
> > This is a prototype patch for libxl to write virtio disk and nic
> > configurations in xenstore.
> > 
> > I have following questions on this patch:
> > 
> > 1. VBD encoding for virtio disk.
> > In fact, virtio disk driver doesn't care about this encoding, so
> > arbitrary number is OK. I also discover a strange bug in xenstore -- if
> > I use (2<<28) | (disk<<4) | partition (reserved encoding), it will
> > trigger a xenstore parsing bug which affects existing protocol (VIF, VFB
> > etc.), causing them fail to initialize frontend and backend.
> 
> Apart from the strange bug, I think that the encoding is reasonable.
>

A second thought comes to me. Since virtio frontend does not care
about this encoding, can we just use 0,1,...,n for it? Just like VIF
case.
 
> 
> > 2. Configuration syntax and implementation for virtio disk and nic.
> > Currently some hacks are needed to distinguish virtio devices. I hope we
> > can get a cleaner implementation.
> 
> I think you need to add a new field in libxl_device_disk to specify the
> protocol, something like libxl_disk_protocol, that can be:
> 
> LIBXL_DISK_PROTOCOL_XENVBD
> LIBXL_DISK_PROTOCOL_VIRTIO
> 
> then parse_disk_config can be modified to distinguish xen disks from
> virtio disks and set the field accordingly.

Good idea. Working on this.

Wei.

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