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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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.


> 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.

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