On Thu, 17 Jan 2008, Troy Dawson wrote:

> John Summerfield wrote:
>> Jan Iven wrote:
>>> On 17/01/08 02:45, John Summerfield wrote:
>>>> Jan Iven wrote:
>>> ..
>>>>> SL4 can then run as a domU, with some caveats (cannot mix 32/64 bit
>>>>>  doms).
>>>> I'm not sure about that. I run 64-bit Fedora 8 on Intel, and run
>>>> several 32-bit guests.
>>> Sorry - I was unclear and perhaps wrong.  As stated on
>>> http://www.linuxtopia.org/online_books/centos5/centos_5_xen_virtualization/centos5_ch-virt-hw-support.html
>>>
>>>
>>>> With Red Hat Virtualization, 32-bit hosts runs only 32-bit
>>>> paravirtual guests. 64-bit hosts runs only 64-bit paravirtual guests.
>>>> And a 64-bit full virtualization host runs 32-bit, 32-bit PAE, or
>>>> 64-bit guests. A 32-bit full virtualization host runs both PAE and
>>>> non-PAE full virtualization guests.
>>> This could have changed with 5.1 -  Red Hat claims on
>>> http://www.europe.redhat.com/rhel/virtualization/ that 5.1 now has
>>>
>>>> # The ability to run 32-bit para-virtualized guests on x86-64 systems
>>>> running in 64-bit mode.
>>> (I guess they are talking about the dom0 here)
>>
>> Well, I did mention my experience is on F8:-) I've only one system with
>> hardware virtualisation, and its first level OS is Fedora 8.
>>
>> I use it to answer questions such as "Can I take this windows system run
>>   it on different hardware without it barfing because it's become
>> unactivated?" and to similarly play with Windows domains.
>>
>> I seem to have an inordinate array of problems:-( Fortunately, Fedora
>> has two virtualisation technologies, there's also KVM, and sometimes one
>> works when the other does not.
>>
>
> Just so you know, because this was discussed on Fermi's mailling list.
>
> The xen in SL 5.1 is 3.0.3, the same as RedHat's.
>
> RedHat's original release announcement said that you can run 32 bit
> paravirtualized guests on 64 bit xen hosts.
> RedHat's engineers then quickly said "No it doesn't, don't do it.  We need to
> change the announcement."

The Release Notes for 5.1 state that this is a "Technology Preview" and 
thus is not supported.  The announcement that is mentioned above is on 
RedHat's web area .

-Connie Sieh

  >
> Last time I checked, RedHat hadn't changed the announcement, so we ran some
> testshere at Fermi.
>
> On SL5 is technically possible to get a 32 bit guest paravirtulized guest
> running on a 64 bit host.  But don't do it.  It will crash.  The longest we
> ever got one to stay  up was 5 minutes.  Most won't even fully boot before
> crashing.
>
> We had some users that needed 32 bit guests on 64 bit hosts, so they updated to
> the latest stable xen (3.1.x I believe) and they were able to do it, and it
> seemed to be stable.
>
> Fedora 8 (and possibly 7) has the latest xen in it, so it most likely that they
> have the version that will do 32 bit guests on 64 bit hosts.
>
> Troy
>