Hyper-V Enlightenments with Libvirt

With Windows 10, it’s helpful to enable Hyper-V Enlightenments, to save CPU and increase VM responsiveness.

To use these enlightenments, edit your libvirt xml:

<features>
  <acpi/>
  <apic/>
  <pae/>
  <hyperv>
    <relaxed state='on'/>
    <vapic state='on'/>
    <spinlocks state='on' retries='8191'/>
    <vpindex state='on'/>
    <synic state='on'/>
    <stimer state='on'/>
    <reset state='on'/>
  </hyperv>
</features>

More information available on https://fossies.org/linux/qemu/docs/hyperv.txt

Another interesting note: if you want to run Windows 10 or similar in a VM, you might want to use these clock timer settings, to avoid high load even when your VM is idle:

<clock offset='localtime'>
  <timer name='rtc' tickpolicy='catchup'/>
  <timer name='pit' tickpolicy='delay'/>
  <timer name='hpet' present='no'/>
  <timer name='hypervclock' present='yes'/>
</clock>