Re: cpu frequency

[Paolo Bonzini <pbonzini@redhat.com>]

> A commercial application running on Windows (kvm guest) detects CPU as:
> CPU_0: CPU0, Intel64 Family 6 Model 42 Stepping 1, 64, 64, 2200,
> 078BFBFD000206A1, 10753, CPU 0
> After some time, without reboot, it detects as:
> CPU_0: CPU0, Intel64 Family 6 Model 42 Stepping 1, 64, 64, 2298,
> 078BFBFD000206A1, 10753, CPU 0
> 
> Windows Server 2012 Control Panel -> System shows CPU as 2.3 GHZ, but after 
> reboot it might show 2.2 or 1.97 GHz.
> 
> The problem is, that commercial application stops working after it detects 
> CPU frequency change (2200 -> 2298 in above case). Is it possible to patch 
> qemu-kvm that it shows some constant frquency to the guest?

Do you know how the application computes the frequency?

In the case of Windows it's probably some timing loop that is executed
at startup, and the result depends on frequency scaling in the host.
Try adding this to the XML in the meanwhile, and see if the control
panel shows the same value:

Inside <features>:

  <hyperv>
    <relaxed state='on'/>
  </hyperv>

Inside <clock offset='localtime'>:

  <timer name='hypervclock' present='yes'/>

Paolo