Re: [Libguestfs] [PATCH] v2v: add support for virtio-scsi
On Wed, Apr 13, 2016 at 07:45:42PM +0300, Roman Kagan wrote:
On Wed, Apr 13, 2016 at 10:11:54AM +0100, Richard W.M. Jones wrote:
> On Tue, Apr 12, 2016 at 06:46:31PM +0300, Roman Kagan wrote:
> > + (* Presence of virtio-scsi controller. *)
> > + let has_virtio_scsi =
> > + let obj = Xml.xpath_eval_expression xpathctx
> > +
"/domain/devices/controller[@model='virtio-scsi']" in
>
> I guess this short cut is OK. A true test would involve checking the
> <target bus="scsi"> on each disk and matching it back to the
> controller. In other words, a huge pain! Maybe you can add an "XXX"
> comment in the source about this.
On a second look, I'm not sure I got your comment right.
AFAICS there's no way in libvirt xml to define multiple scsi buses,
I think this is possible, although massively unlikely in practice. I
think the different controllers would have different
index="0"/index="1"/... attributes.
so all the matching I can do is just to notice the presence of
virtio-scsi controller, and attribute all SCSI drives to it. This
is exactly what happens in the patch.
Am I missing something?
So first off I think this part of the patch and your assumption is
fine, there's no need to change the code.
However there is a possibility that the source guest might have
multiple mixed virtio-blk + virtio-scsi disks. In that case the disks
would look like this:
<disk type='file' device='disk'>
<driver name='qemu' type='raw'/>
<source file=...>
<target dev='vda' bus='virtio'/>
</disk>
<disk type='file' device='disk'>
<driver name='qemu' type='raw'/>
<source file=...>
<target dev='sda' bus='scsi'/>
</disk>
<controller type="scsi" index="0"
model="virtio-scsi"/>
It's not something that we should worry about, and a simple comment
with "XXX" in it is fine, if you agree with my analysis.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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