Xen users - Nov 2009 - ''lowest common denominator'' cpuid feature set

I want to be able to test live migration... I have an intel box and an
amd box, so live migration between them won''t ''just
work''. From what
I''ve read though, I should be able to use cpuid to turn off all the cpu
features which might be different between them. Is this do-able? I''m
willing to accept any resulting loss of performance etc.

James

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On Tue, Nov 17, 2009 at 5:56 PM, James Harper
<james.harper@bendigoit.com.au> wrote:
> I want to be able to test live migration... I have an intel box and an
> amd box, so live migration between them won''t ''just
work''. From what
> I''ve read though, I should be able to use cpuid to turn off all
the cpu
> features which might be different between them. Is this do-able?
I''m
> willing to accept any resulting loss of performance etc.
>
James,

You can use localhost as the migration target to eliminate CPU and
shared storage requirements.

It''s possible to mask cpu features resulting in a generic vcpu that
should run on intel or amd. The following excerpt is taken from the
xen sample config file xmexample.hvm:
>From the xmexample.hvm
#  Downgrade the cpuid to make a better compatibility for migration :
# Look like a generic 686 :
# cpuid = [ ''0:eax=0x3,ebx=0x0,ecx=0x0,edx=0x0'',
#           ''1:eax=0x06b1,
#              ecx=xxxxxxxxxxx0000xx00xxx0000000xx0,
#              edx=xxx00000xxxxxxx0xxxxxxxxx0xxxxxx'',
#           ''4:eax=0x3,ebx=0x0,ecx=0x0,edx=0x0'',
#  ''0x80000000:eax=0x3,ebx=0x0,ecx=0x0,edx=0x0'']
#  with the highest leaf
#  - CPUID.0[EAX] : Set the highest leaf
#  - CPUID.1[EAX] : 686
#  - CPUID.1[ECX] : Mask some features
#  - CPUID.1[EDX] : Mask some features
#  - CPUID.4 : Reply like the highest leaf, in our case CPUID.3
#  - CPUID.0x80000000 : No extension we are on a Pentium III, reply like the
#  highest leaf (CPUID.3).



Keith Coleman

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> On Tue, Nov 17, 2009 at 5:56 PM, James Harper
> <james.harper@bendigoit.com.au> wrote:
> > I want to be able to test live migration... I have an intel box and
an
> > amd box, so live migration between them won''t ''just
work''. From what
> > I''ve read though, I should be able to use cpuid to turn off
all the
cpu
> > features which might be different between them. Is this do-able?
I''m
> > willing to accept any resulting loss of performance etc.
> >
> 
> James,
> 
> You can use localhost as the migration target to eliminate CPU and
> shared storage requirements.
I''ve seen problems with device usage (fail to bind to vbd because it is
already in use because the ''source'' instance is still using
it). That
was a while ago though.
> 
> It''s possible to mask cpu features resulting in a generic vcpu
that
> should run on intel or amd. The following excerpt is taken from the
> xen sample config file xmexample.hvm:
> 
> From the xmexample.hvm
> #  Downgrade the cpuid to make a better compatibility for migration :
That worked perfectly - migrated from the AMD machine to the Intel
machine and back again.

Thanks

James

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Hello list,

we are trying to get a windows 2003 enterprise running with our 2 socket xeon
quad core with hyperthreading.

Since xen turns every thread into a cpu, we could not use enterprise, it only
supports 8 CPU, but we want the hyperthreading as well (16 logical cpu).

We tried
cpuid =
[''1:edx=xxx1xxxxxxxxxxxxxxxxxxxxxxxxxxxx,ebx=xxxxxxxx00001000xxxxxxxxxxxxxxxx'',''4,0:eax=001111xxxxxxxxxxxxxxxxxxxxxxxxxx'']
vcpus=16

but windows does not start with it.
When we set vcpus=8 then it starts - with 8 cpus of course.

Does anybody have an idea for the correct configuration?

Thanks,
        Hinrich


Hinrich Aue
Sr. SW Engineer
Kofax Development GmbH

Freiburger Strasse 6
79199 Kirchzarten
Germany

Tel: +49 (7661) 9797 17
Fax: +49 (7661) 9797 29
Hinrich.Aue@kofax.com



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or have received this communication in error, please notify the sender via phone
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On Fri, Nov 27, 2009 at 9:54 AM, Hinrich Aue <Hinrich.Aue@kofax.com>
wrote:
> Hello list,
>
> we are trying to get a windows 2003 enterprise running with our 2 socket
xeon quad core with hyperthreading.
>
> Since xen turns every thread into a cpu, we could not use enterprise, it
only supports 8 CPU, but we want the hyperthreading as well (16 logical cpu).
>
> We tried
> cpuid =
[''1:edx=xxx1xxxxxxxxxxxxxxxxxxxxxxxxxxxx,ebx=xxxxxxxx00001000xxxxxxxxxxxxxxxx'',''4,0:eax=001111xxxxxxxxxxxxxxxxxxxxxxxxxx'']
> vcpus=16
>
> but windows does not start with it.
> When we set vcpus=8 then it starts - with 8 cpus of course.
>
> Does anybody have an idea for the correct configuration?
I think you almost got it right but you have a 0 and a 1 swapped, try this:

cpuid=''1:edx=xxx1xxxxxxxxxxxxxxxxxxxxxxxxxxxx,ebx=xxxxxxxx00010000xxxxxxxxxxxxxxxx'',''4,0:eax=001111xxxxxxxxxxxxxxxxxxxxxxxxxx'']


note ebx 00010000 rather than 00001000

Andy
>
> Thanks,
>        Hinrich
>
>
> Hinrich Aue
> Sr. SW Engineer
> Kofax Development GmbH
>
> Freiburger Strasse 6
> 79199 Kirchzarten
> Germany
>
> Tel: +49 (7661) 9797 17
> Fax: +49 (7661) 9797 29
> Hinrich.Aue@kofax.com
>
>
>
> This communication is only for the use of the intended recipient. It may
contain confidential or proprietary information. If you are not the intended
recipient or have received this communication in error, please notify the sender
via phone and destroy this communication immediately.
>
> Kofax Development GmbH
> Sitz der Gesellschaft: Kirchzarten
> Registergericht: Amtsgericht Freiburg i.Br.
> Registernummer: HRB 7007
> Gesch?ftsf?hrer: Stefan Gaiser und Bradford Weller
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>
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