QEMU version 2.12.1 introduced a performance feature under commit
be7773268d98 ("target-i386: add KVM_HINTS_DEDICATED performance hint")

This patch adds a new KVM feature 'hint-dedicated' to set this performance
hint for KVM guests. The feature is off by default.

To enable this hint and have libvirt add "-cpu host,kvm-hint-dedicated=on"
to the QEMU command line, the following XML code needs to be added to the
guest's domain description in conjunction with CPU mode='host-passthrough'.

  <features>
    <kvm>
      <hint-dedicated state='on'/>
    </kvm>
  </features>
  ...
  <cpu mode='host-passthrough ... />
Signed-off-by: NWim ten Have <wim.ten.have@oracle.com>
Signed-off-by: NMenno Lageman <menno.lageman@oracle.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>