[Libvir] [PATCH] pae/nonpae capabilities for paravirt xen guests

Daniel P. Berrange berrange at redhat.com
Mon Mar 26 15:30:39 UTC 2007

On Sun, Mar 25, 2007 at 03:48:41PM +0100, Richard W.M. Jones wrote:
> David Lutterkort wrote:
> >I noticed that the guest capabilities on a xen dom0 always contain both
> >the pae and nonpae feature - AFAIK, you can't mix pae/nonpae guests and
> >hosts, and only one of the features should be there.
> >
> >The attached patch contains the obvious fix.
> Actually, <pae/><nonpae/> was intentional, to indicate that both modes 
> of operation could be used.  (Perhaps the error, then, is that if PAE is 
> not supported, <features><nonpae/></features> should be used?).  Anyway, 
> I don't really understand the specifics of selecting PAE and non-PAE for 
> Xen guests, so I'll punt on this to Dan.

Yes, as Rich says its perfectly valid to have both flags listed under the
same architecture. We're actually dealing with a tri-state here rather than
a boolean. Xen can support

  - PAE only      (Xen i686 paravirt)
  - non-PAE only  (Xen i686 paravirt)
  - PAE & non-PAE (Xen i686/x86_64 fullyvirt)

That said, I'm not sure we've got the translation of Xen capabilities
into XML quite right - I'm going to do some verification of a couple
of other dev boxes with varying levels of Xen support / archicture mixes.

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