I noticed I can only use 6 vcpu's in the gui. I also noticed that when I selected 6 my windows kvm wasn't using 6 cores. I did some googling and found out I can check by running

virsh capabilities | grep topology

which gets me:

      <topology sockets='1' cores='6' threads='1'/>
    <topology>
    </topology>

 

I have two of those processors so I should have 12 cores. Also, to get windows to see the 6 vcpus I had to edit the xml  and put this in:

<vcpu>6</vcpu>
<cpu>
     <topology sockets='1' cores='6' threads='1'/>
</cpu>

 

After this Windows at least sees all the cores on one of my processors. Has anyone experience an issue with only one cpu being recognized?

Can you post your entire XML?

 

If you want your VM to use 12 CPU's, the pertinent part of your XML should be something like:

 

  <!-- TOTAL NUMBER OF CPUS FOR VM -->
  <vcpu placement='static'>12</vcpu>
  <cpu mode='host-passthrough'>
    <!-- SOCKETS X CORES X 1 THREAD EQUALS VCPU COUNT -->
    <topology sockets='3' cores='4' threads='1'/>
  </cpu>

 

You can play around with the <topology ...> line, for example:

 

    <!-- SOCKETS X CORES X 1 THREAD EQUALS VCPU COUNT -->
    <topology sockets='6' cores='2' threads='1'/>

 

If you're doing CPU pinning, there should be 12 lines for that also.

 

Gary