Re: Xen3/PAE problems with domainU

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Aug 04, 2006 at 09:00:31PM -0400, Todd Vierling wrote:
> This is Bcc:'d to port-i386 as it also concerns PAE, which may be required
> to get things working correctly.  The main thread should remain on port-xen.
> 
> So I am in contact with the proprietor of a hosting company that is offering
> Xen-based hosting, and is moving to Xen 3.  We had a pretty well working
> NetBSD domU setup for Xen2.  But for PAE and other things, this host has to
> move to Xen3.
> 
> I got the 20060803 build of the Xen3 kernels, and the host ran into this
> when creating the domain.  The host has Linux kernel 2.6.16 compiled
> directly from xensource + distro sources, and has xentools 3.0.2-2
> installed.
> 
> ==========
> 
> [...]
> 
> ==========
> 
> I found the following very vague post about a problem just like this when
> the dom0 has PAE enabled but the domU doesn't:
> 
>     http://lists.xensource.com/archives/html/xen-users/2006-06/msg00077.html
> 
> Is there any PAE support in work for i386 (not just amd64)?  Looks like the
> Xen folks aren't going to emulate non-PAE domU environments on a PAE dom0
> anytime soon, so this has become a requirement.

I'm not sure NetBSD/i386 itself will get PAE support, AFAIK nobody is
working on it. I don't know how much work is involved, or what it
would mean for userland compatibility (especially kmem grovelers).

I don't know if a Xen/x86_PAE could boot a guest kernel for x86_64
(you could probably try with a linux x86_64 domU kernel). It it does the way
to go would be to port NetBSD/amd64 to Xen. There's patches for OpenBSD so
maybe it's not that much work to get a domU kernel working.
But I don't have the time to work on this right now (I want to get dom0/i386
working right first), and some manpower is definitively welcome :)

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--