Re: [Xen-users] Dom0 versus DomU and sata DVD drives

["Stephen Carville" <stephen.carville@xxxxxxxxx>]

On 5/7/07, Mark Williamson <mark.williamson@xxxxxxxxxxxx> wrote:
> Hi Stephen,
>
> I cc-ed this back onto xen-users, hope you don't mind.
Not at all.  I would have done that myself if I'd been paying attention...

> > > There's not currently a way to allow domUs to get full CD-ROM
> > > functionality without passing an entire SATA controller to them using PCI
> > > passthrough.  I suspect for your desktop-based testing application it's
> > > not worth it.  In particular, domUs can currently only read data from a
> > > CD, they can't write to it.  Also, AFAIK they can't treat the CD as an
> > > audio disk either.
> >
> > That's good enough for me and I can see the CD as read only in the
> > paravirtualized linux domains.  I'll test with RHEL4 and RHEL 3
> > tomorrow.
>
> Cool.  Paravirtualised domains don't strictly see it as a CD at all -
> CD-related ioctls won't work for instance.  But for many purposes this does
> not matter.
It's good enough for now.  I only need to see a boot CD or, sometimes,
a CD/DVD with data files that need to be copied.  Eventually I may
need to create virtual desktop boxes but they won't need a CD drive
anyway.

> > Is there a trick to getting the CDROM to show up in XP?
>
> I just dd if=/dev/cdrom of=/mycd.iso then export the iso file to XP.
Tried that but dd only copied abut 11M of the CD (MS Office).  HOwever
k3b seesm to have copied the so I can try again when IO get to work.

> I was under the impression that you should be able to give HVM guests access
> to the real CD-ROM drive too, but I never got that working when I tried it.
> I think in principle you just export /dev/cdrom with something like:
>
> disk [ ... other disks ..., 'file:/dev/cdrom,hdc:cdrom,r', ... ]
I've tried:

'phy:/dev/scd0,hdd:cdrom,r',

but not 'file: etc.'

I'll give that a try.

> If you're lucky it might even let the guest eject the host cd rom drive - ISTR
> seeing a patch for that at one point, don't know if it's applied yet.
I can appreciate teh difficulty of getting a device like the CD/DVD
drive to be shared by several VM's. I imagine the hypervisor will need
to enforce some kind of ownership of each such device.

> Cheers,
> Mark
Thank for all your help.

> --
> Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
> Mark: To answer a question with a question: What use is a skateboard?
> Dave: Skateboards have wheels.
> Mark: My wheel has a wheel!
--
Stephen Carville

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