Enable live migration between heterogeneous kvm hypervisors.

Modified NovaComputeLibvirtContext in nova_compute_context.py to
transclude 'cpu-mode' and 'cpu-model' into nova.conf.

Added conditional tags for 'cpu_mode' and 'cpu_model' to the havana,
icehouse, juno, and kilo nova.conf templates.

Added 'cpu-mode' and 'cpu-model' string params and descriptions to
config.yaml.

Fixes Bug #1499611

config.yaml

@@ -211,6 +211,22 @@ options:
       order for this charm to function correctly, the privacy extension must be
       disabled and a non-temporary address must be configured/available on
       your network interface.
+  cpu-mode:
+    type: string
+    default:
+    description: |
+      Set to 'host-model' to clone the host CPU feature flags; to 
+      'host-passthrough' to use the host CPU model exactly; to 'custom' to 
+      use a named CPU model; to 'none' to not set any CPU model. If 
+      virt_type='kvm|qemu', it will default to 'host-model', otherwise it will 
+      default to 'none'.
+  cpu-model:
+    type: string
+    default:
+    description: |
+      Set to a named libvirt CPU model (see names listed in 
+      /usr/share/libvirt/cpu_map.xml). Only has effect if cpu_mode='custom' and 
+      virt_type='kvm|qemu'.
   # Storage configuration options
   libvirt-image-backend:
     type: string

hooks/nova_compute_context.py

@@ -124,6 +124,12 @@ class NovaComputeLibvirtContext(context.OSContextGenerator):
         if config('disk-cachemodes'):
             ctxt['disk_cachemodes'] = config('disk-cachemodes')
 
+        if config('cpu-mode'):
+            ctxt['cpu_mode'] = config('cpu-mode')
+
+        if config('cpu-model'):
+            ctxt['cpu_model'] = config('cpu-model') 
+
         if config('hugepages'):
             ctxt['hugepages'] = True
 

templates/havana/nova.conf

@@ -128,6 +128,12 @@ server_proxyclient_address = {{ console_listen_addr }}
 {% endif -%}
 
 [libvirt]
+{% if cpu_mode -%}
+cpu_mode = {{ cpu_mode }}
+{% endif -%}
+{% if cpu_model -%}
+cpu_model = {{ cpu_model }}
+{% endif -%}
 {% if libvirt_images_type -%}
 images_type = {{ libvirt_images_type }}
 images_rbd_pool = {{ rbd_pool }}

templates/icehouse/nova.conf

@@ -146,6 +146,12 @@ server_proxyclient_address = {{ console_listen_addr }}
 {% endif -%}
 
 [libvirt]
+{% if cpu_mode -%}
+cpu_mode = {{ cpu_mode }}
+{% endif -%}
+{% if cpu_model -%}
+cpu_model = {{ cpu_model }}
+{% endif -%}
 {% if libvirt_images_type -%}
 images_type = {{ libvirt_images_type }}
 images_rbd_pool = {{ rbd_pool }}

templates/juno/nova.conf

@@ -142,6 +142,12 @@ server_proxyclient_address = {{ console_listen_addr }}
 {% endif -%}
 
 [libvirt]
+{% if cpu_mode -%}
+cpu_mode = {{ cpu_mode }}
+{% endif -%}
+{% if cpu_model -%}
+cpu_model = {{ cpu_model }}
+{% endif -%}
 {% if libvirt_images_type -%}
 images_type = {{ libvirt_images_type }}
 images_rbd_pool = {{ rbd_pool }}

templates/kilo/nova.conf

@@ -147,6 +147,12 @@ server_proxyclient_address = {{ console_listen_addr }}
 {% endif -%}
 
 [libvirt]
+{% if cpu_mode -%}
+cpu_mode = {{ cpu_mode }}
+{% endif -%}
+{% if cpu_model -%}
+cpu_model = {{ cpu_model }}
+{% endif -%}
 {% if libvirt_images_type -%}
 images_type = {{ libvirt_images_type }}
 images_rbd_pool = {{ rbd_pool }}