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

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

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=xxxxxxxx00010000xxxxxxxxxxxxxxxx','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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