[Libvir] Fix handling of HVM boot parameters

[Daniel Veillard]

On Wed, Aug 09, 2006 at 09:33:11PM -0400, Jeremy Katz wrote:
> On Thu, 2006-08-10 at 01:00 +0100, Daniel P. Berrange wrote:
> > I meant to include a complete example XML doc showing the changes in
> > place, so here is a XML dump from a HVM domain which has been booted
> > off a CDROM:
> [snip]
> >     <disk type='file'>
> >       <source file='/root/foo.img'/>
> >       <target dev='ioemu:hda'/>
> >     </disk>
> 
> Given what we know is coming, does it make sense to drop the ioemu: here
> and just have it be implied for HVM guests?  Accept it if it's there
> (and then drop it if we're on xend 3.0.3), but not really show it?

  Sound sensible, the problem is detecting the version of xend, 
of course you can ask xend, you will get the exact version of the
compiler used to compile it, but when it comes to xen version itself
  (xen_major 3) (xen_minor 0) (xen_extra -unstable)
which makes things a bit hard to distinguish 3.0.2 from 3.0.3 :-\
We could try to use the changest but it's not available in our build
either.
Still in spite of this I would rather not bury in the format an exotic
labelling which we know will be ignored (or breaking) later.

> Then again, not 100% sure how all of this is going to interact when we
> start having PV drivers for HVM guests :-/
> 
> >     <disk type='file'>
> >       <source file='/root/boot.iso'/>
> >       <target dev='cdrom'/>
> >     </disk>
> 
> Similarly, instead of target dev='cdrom', does it make more sense to
> have a devicetype (or something) that's an attribute of the disk rather
> than a magic device?

  There is the read-only attribute. For example UML has no specific way
to indicate an emulated CD-ROM, there is just a read-only command line 
flag.

     <disk type='file'>
       <source file='/root/boot.iso'/>
       <target dev='hdc'/>
       <readonly/>
     </disk>

  After all since we don't have hardware to tell us what kind of device
it is, it is really a matter of what kind of accesses are allowed. How
it is mapped underneath depends on the engine used, but should probably
not affect the XML format.

Daniel

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