[libvirt] Is it possible to use more then 2 CPUs in the guest?

[Mirko Raasch]

Tom Hughes schrieb:
> On 06/08/09 12:36, Daniel P. Berrange wrote:
>> On Wed, Aug 05, 2009 at 10:11:07AM +0200, Mirko Raasch wrote:
>>
>>> in my server i use an Intel Quad Core CPU and i want to use in one
>>> WindowsXP guest all 4 cores.
>>> The device manager shows four CPU (Qemu Virtual CPU version 0.10.5).
>>> When i start prime95 or superpi, only 2 of them are in use. CPU-Z shows
>>> also 2 Cores, instead of 4 like the device manager.
>>
>> I don't know what those apps are, but they sound broken to me. If the
>> guest has been launched with 4 virtual CPus, the guest OS should be
>> able to use them, regardless of what your host core/socket/thread cpu
>> topology is. KVM/QEMU allow upto 16  virtual CPUs IIRC, and this is
>> totally independant of how many physical CPUs you have.
>
> As other people have already said, it's a Windows licensing thing 
> where some versions of Windows are designed to only work on a limited 
> number of physical CPU packages. So they will run 4-way on a quad core 
> but not on four single core CPUs.
>
> So it is seeing all the cores and reporting them in task manager but 
> only allowing two to be used by programs.
>
> Tom
>
I tried Windows 7 Ultimate and its the same like in WinXP, only two 
Cores are in use. The other two cores are bored.
It does not matter whether I emulate four, six or eight cpu in the 
guest, in the host only two of four cores are in use.