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Re: [Xen-users] Re: 64 Bit Dom0 and 32Bit DomU

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Subject: Re: [Xen-users] Re: 64 Bit Dom0 and 32Bit DomU
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Tue, 20 May 2008 22:44:05 +0100
Cc: Jens Kleikamp <jens@xxxxxxxxxxxxxxxxxx>
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On Tuesday 20 May 2008, Jens Kleikamp wrote:
> > If you've upgraded Xen make sure you have properly uninstalled the old
> > tools and installed the new ones to match your Xen.
> >
> > nb. to actually use 32-on-64 you also need a sufficiently new dom0 kernel
> > that supports this feature.
> >
> > Cheers,
> > Mark
> Hello,
> I am hanging also on this issue, I want to a boot 32bit debian domu on
> my 64bit host with XEN 3.2.1.
> The 32bit debian 4.0 boots fine with my default 64bit domU kernel. This
> makes me really wonder.
> But with a 64bit kernel the 32bit domU is not that usable as I thought.
> For example, openpkg and probably other software looks what kernel is
> running and then thinks its on a 64bit system.

OK.  32-bit distros can often boot on a 64-bit kernel due to the binary 
compatibility provided.  Your package manager's confusion can probably be 
fixed but there are other things which may still break.

> Now I am trying to figure out a new kernel-config to make this work.
> Maybe you can give some tips what changes to the kernel configs are needed.

On 3.2.1 you should be able to boot a 32-bit Xenified kernel instead of the 
64-bit one and have it Just Work(TM).  Have you tried this?  Were there 
problems?  The 32-bit kernel needs to support PAE (CONFIG_HIGHMEM_64G) in 
order to run on 64-bit Xen.

I'm not sure if suspend/resume/migration will work for that setup but just 
running the domain paravirtualised ought to be OK.


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