Revert "compute: don't use 'host-model' CPU mode"

This reverts commit d0c55cd2f0.

Change-Id: If15fd288178563c7bfc91a8d5a56fabf4ef21b8b
Closes-bug: #1640559
Related-bug: #1618473

deployment/puppet/openstack/manifests/compute.pp

@@ -265,15 +265,11 @@ class openstack::compute (
       nova_shell             => '/bin/bash',
   }
 
-  # CPU configuration created using host-model may not work as expected.
-  # The guest CPU may differ from the configuration and it may also confuse
-  # guest OS by using a combination of CPU features and other parameters (such
-  # as CPUID level) that don't work. Until these issues are fixed, it's a good
-  # idea to avoid using host-model
-  # http://libvirt.org/formatdomain.html#elementsCPU
-  # https://bugs.launchpad.net/mos/+bug/1618473
+  if str2bool($::is_virtual) {
     $libvirt_cpu_mode = 'none'
-
+  } else {
+    $libvirt_cpu_mode = 'host-model'
+  }
   # Install / configure nova-compute
 
   # From legacy ceilometer notifications for nova