Re: [Xen-users] Running Xen on top of Xen

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > I was wondering if anyone has run Xen on top of Xen in the following
> > scenarios and did it work:
> >
> > 1) Xen-Paravirtualized on top of Xen Intel-VT (I hope this would work
> > out of the box)
> > 2) Xen Intel-VT on top of Xen-Paravirtualized (I don't think this would
> > work out of the box)
>
> You can't load the xen hypervisor inside a PV guest, which would be
> necessary to get 2) to work.

As Jim says, you can't run Xen inside of a PV domain.  Xen can't emulate the 
presense of VT if it's not already there, so your option 2 won't work, sorry.

> Even if you could run the hypervisor inside an 
> hvm guest to get 1) to work, I would suspect the performance would be
> abysmal. I tried loading WIndows Virtual PC 2007 inside my Xen WIndows XP
> guest. The configuration steps worked fine, but as soon as I tried to run
> the Virtual PC guest, my Xen Windows guest became unresponsive. (Maybe
> Xen/qemu-dm was trying to emulate every instruction of the Virtual PC
> guest? :-) Some people on this list report being able to run Xen under
> Vmware.

Actually, I find that running Xen PV in an HVM domain on top of a host Xen 
performs OK.  Not great but actually pretty good.  The fact that it's doing 
paravirtualisation rather than two nested layers of full virtualisation 
probably makes a lot of difference here!

I actually use Xen-on-Xen to do development, with my unstable development Xens 
running in HVM domains on top of a nice reliable host Xen :-)

Cheers,
Mark

-- 
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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