Re: HEADS UP: HVM cdrom/disk configuration changed

["Daniel P. Berrange" <berrange@redhat.com>]

On Sun, Aug 06, 2006 at 01:26:57AM +0100, Christian Limpach wrote:
> Hi,
> 
> Changeset 10921:4c2fab8f8c34 changes how disk and cdrom drives are
> configured for hvm domains.  Disks no longer need the ioemu: prefix,
> it is ignored if it is present.  Cdrom drives are now configured like
> disks by adding a :cdrom suffix to the target device (i.e.
> 'file:/root/mytest.iso,hdc:cdrom,r').  There is no default cdrom drive
> any longer, to create an empty cdrom drive, use ',hdc:cdrom,r'.  Any
> of the 4 ide devices can be cdrom drives now.
> 
> There is no compatibility support for the cdrom= option in old config
> files.  I'll consider patches to add such compatibility support.  The
> compatibility code should be implemented in xm.

Any suggestions on how an application talking to XenD should detect whether
to use the old or new format config for creating domains ?

The only version number available is under /xend/node :

  (xen_major 3) (xen_minor 0) (xen_extra -unstable) 

But as you can see, this doesn't let us determine version with fine enough
granularity to decide which format config to use for HVM. If working off
a formal release I assume the 'xen_extra' fragment would refer to the last
digit in the xen release, but alot of people / tools are running against
-unstable builds so xen_extra fragment isn't really sufficient.

I realize that the current XenD SEXPR interface will shortly be deprecated
in favour of a new XML-RPC interface, but this isn't happening until 3.0.4
at earliest. In the meantime apps really need a way to determine what config
format to use for talking to XenD. Perhaps we could add a trivial API version
token to the SEXPR 

  (xend_sexpr_format 2)

To let people detect that they should use this new style HVM config ?

Regards,
Dan.
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