Xen users - Apr 2006 - about migration betweendifferents architecture

Hello
I aim to use xen to migrate virtual machine between different host but i
have a lot of problem in suchcase:
My first VMM use XEN 3.01 32bit on an x86 machine (athlon XP)
My second VMM use Xen 3.01 for amd64 SMP on a sun v20z

The VM use an standard ubuntu distribution (32bits, i386 architecture).
I am able to create the vm on each machine but i can''t migrate (the
destination VMM crash)

Is there a solution to permit migration between different host, or do I
commit a mistake ?

Thanks
Fabien


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Hi,

 > My first VMM use XEN 3.01 32bit on an x86 machine (athlon XP)
 > My second VMM use Xen 3.01 for amd64 SMP on a sun v20z
migrating between different platforms can work, but it depends how 
different the systems are and on the actual status the processor has at 
the moment of migration. If the source-system uses features that are not 
available on the destination, migration will fail!

 > The VM use an standard ubuntu distribution (32bits, i386
 > I am able to create the vm on each machine but i can''t migrate
 > (the destination VMM crash)
I always thought that on a x86-64-system only 64 bit-domU''s will work 
and on i386 only 32 bit. Is this not true anymore?
-- 

Chau y hasta luego,

Thorolf

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>  > My first VMM use XEN 3.01 32bit on an x86 machine (athlon XP)
>  > My second VMM use Xen 3.01 for amd64 SMP on a sun v20z
>
> migrating between different platforms can work, but it depends how
> different the systems are and on the actual status the processor has at
> the moment of migration. If the source-system uses features that are not
> available on the destination, migration will fail!
Yep.
>  > The VM use an standard ubuntu distribution (32bits, i386
>  > I am able to create the vm on each machine but i can''t
migrate
>  > (the destination VMM crash)
>
> I always thought that on a x86-64-system only 64 bit-domU''s will
work
> and on i386 only 32 bit. Is this not true anymore?
Right now it''s still true.

So, folks, no migrating between 64 and 32 bit architectures.  It''s
naughty,
yall hear?  ;-)

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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Quoting Mark Williamson <mark.williamson@cl.cam.ac.uk>: 
 
> > I always thought that on a x86-64-system only 64 bit-domU''s
will work
> > and on i386 only 32 bit. Is this not true anymore? 
>  
> Right now it''s still true. 
 
i think the mantra is something like "the memory model of a paravirtualized
kernel must match that of the hypervisor" 
 
> So, folks, no migrating between 64 and 32 bit architectures.  It''s
naughty,
>  
> yall hear?  ;-) 
 
in this particular case, it might be a solution to just use the x86-64 in 
totally 32 bit mode, with 32bit xen hypervisor.  would that work? 
 
------ 
Javier 

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> > > I always thought that on a x86-64-system only 64
bit-domU''s will work
> > > and on i386 only 32 bit. Is this not true anymore?
> >
> > Right now it''s still true.
>
> i think the mantra is something like "the memory model of a
paravirtualized
> kernel must match that of the hypervisor"
Yes, for now.

There are plans to relax this a bit at some stage, but it''ll require 
additional support in the system for translating between different memory 
layouts / hypercall tables.
> > So, folks, no migrating between 64 and 32 bit architectures. 
It''s
> > naughty,
> >
> > yall hear?  ;-)
>
> in this particular case, it might be a solution to just use the x86-64 in
> totally 32 bit mode, with 32bit xen hypervisor.  would that work?
It''ll work if the processors are reasonably compatible...

E.g. between a 32-bit Athlon and an Opteron in 32-bit mode...

If one of the CPUs has instructions the other doesn''t it''ll be
a problem.
E.g. if 3dnow instructions are being used by the domain and you migrate it to 
an Intel system, you''ll get breakages.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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> -----Original Message-----
> From: xen-users-bounces@lists.xensource.com 
> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of 
> Javier Guerra
> Sent: 26 April 2006 17:56
> To: xen-users@lists.xensource.com
> Subject: Re: [Xen-users] about migration betweendifferents 
> architecture
> 
> Quoting Mark Williamson <mark.williamson@cl.cam.ac.uk>: 
>  
> > > I always thought that on a x86-64-system only 64
bit-domU''s will
> > > work and on i386 only 32 bit. Is this not true anymore?
> >  
> > Right now it''s still true. 
>  
> i think the mantra is something like "the memory model of a 
> paravirtualized kernel must match that of the hypervisor" 
>  
> > So, folks, no migrating between 64 and 32 bit architectures. 
It''s
> > naughty,
> >  
> > yall hear?  ;-)
>  
> in this particular case, it might be a solution to just use 
> the x86-64 in totally 32 bit mode, with 32bit xen hypervisor. 
>  would that work? 
Yes, that would be the way to work it. Since the 64-bit processor is
100% 32-bit compatible, it shouldn''t make any difference (except
you''re
not wearing down the upper 32-bits of the registers ;-) ). 

--
Mats
>  
> ------
> Javier 
> 
> _______________________________________________
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> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
> 
> 

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