Re: [Xen-users] Re: Windows and Multiple CPUS?

["Andrew Lyon" <andrew.lyon@xxxxxxxxx>]

You need Xen 3.3, examples are shown in /etc/xen/ xmexample.hvm-stubdom:

#   Expose to the guest multi-core cpu instead of multiple processors
# Example for intel, expose a 8-core processor :
#cpuid=['1:edx=xxx1xxxxxxxxxxxxxxxxxxxxxxxxxxxx,
#          ebx=xxxxxxxx00010000xxxxxxxxxxxxxxxx',
#     '4,0:eax=001111xxxxxxxxxxxxxxxxxxxxxxxxxx']
#  - CPUID.1[EDX][HT] : Enable HT
#  - CPUID.1[EBX] : Number of vcpus * 2
#  - CPUID.4,0[EAX] : Number of vcpus * 2 - 1
#vcpus=8



I used a single line to set the cpuid:

cpuid=['1:edx=xxx1xxxxxxxxxxxxxxxxxxxxxxxxxxxx,ebx=xxxxxxxx00010000xxxxxxxxxxxxxxxx','4,0:eax=001111xxxxxxxxxxxxxxxxxxxxxxxxxx']
vcpus=8

Andy

On Mon, Sep 29, 2008 at 12:49 PM, Dustin Henning
<Dustin.Henning@xxxxxxxxxxx> wrote:
>        Awesome, mind telling us how you figured this out?  Is it documented
> somewhere?  I have seen several people want to do this, and someone always
> tells them it is not possible.
>        Dustin
>
> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Andrew Lyon
> Sent: Sunday, September 28, 2008 09:44
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] Re: Windows and Multiple CPUS?
>
> On Fri, Sep 19, 2008 at 2:46 PM, Andrew Lyon <andrew.lyon@xxxxxxxxx> wrote:
>> On Fri, Sep 19, 2008 at 2:39 PM, Andrew Lyon <andrew.lyon@xxxxxxxxx>
> wrote:
>>> Hi,
>>>
>>> Am I correct in thinking that when Xen is running on a multi-core /
>>> smp system and several cpus are assigned to a VM they are "presented"
>>> as multiple single core cpus rather than 1 or more multi-core cpus?
>>>
>>> Microsoft CPU limits are for physical sockets, not cores.
>>>
>>> Windows XP and Vista are limited to two physical cpus, running under
>>> Xen the maximum cpus I have seen in task manager and system properties
>>> is 2, although device manager shows all of the assigned cpus (up to
>>> 8).
>>>
>>> Windows 2003 and 2008 standard edition are limited to 4 cpus, which is
>>> the limit I find under Xen, again device manager shows all assigned
>>> cpus (up to 8).
>>>
>>> Is there any way to make windows see the cpus as multi-core so that
>>> all 8 cores can be used ?
>>>
>>> Andy
>>>
>>
>> I've also noticed that if I run "xm list" repeatedly as the VM is
>> starting up I can actually see the cpus being initialized, the value
>> matches the limit i find in windows:
>>
>> A Windows 2003 R2 Standard Edition 32 Bit VM:
>>
>> #grep vcpu Win2003x86.cfg
>> vcpus=8
>>
>> xm list (several times during boot process)
>>
>> Win2003x86                                  24  2048     1
>> Win2003x86                                  24  2048     2
>> Win2003x86                                  24  2048     3
>> Win2003x86                                  24  2048     4
>>
>> But if i booted this version of windows on the raw hardware all 8 cpus
>> would be utilized.
>>
>> Andy
>>
>
> I found the solution to this problem, in my hvm windows config file I added:
>
> cpuid='1:edx=xxx1xxxxxxxxxxxxxxxxxxxxxxxxxxxx,ebx=xxxxxxxx00010000xxxxxxxxxx
> xxxxxx','4,0:eax=001111xxxxxxxxxxxxxxxxxxxxxxxxxx']
> vcpus=8
>
> Which makes the 8 CPUs appear to the guest os as a single 8 core
> rather than 8 separate cpus, as windows is limited to 2 sockets it now
> sees all 8 cores in task manager.
>
> Andy
>
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>
>

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