Add image platform argument

roles/os_images/README.md

@@ -57,6 +57,10 @@ mutually exclusive where each contain:
   This is a dict of the form of `KEY: VALUE`.
 * `packages`: (optional) list of packages to install in the image.
 * `size`: (optional) size to make the image filesystem.
+* `architecture`: (optional) image CPU architecture to pass to diskimage-builder `-a`.
+  If unset, default to the diskimage-builder default architecture: `x86_64`, and upload
+  Glance images with the `cpu_arch: "x86_64"` image property.
+  When setting, consider also setting `properties.cpu_arch` to a corresponding value.
 * `properties`: (optional) dict of properties to set on the glance image.
   Common image properties are available
   [here](https://docs.openstack.org/glance/latest/user/common-image-properties.html).
@@ -76,6 +80,9 @@ or 'community'. Default is 'public'
 `os_images_common`: A set of elements to include in every image listed.
 Defaults to `cloud-init enable-serial-console stable-interface-names`.
 
+`os_images_common_properties`: A dict of Glance image properties to set on all images.
+Defaults to an empty dict, and is overridden by `os_images_list.*.properties`.
+
 `os_images_dib_pkg_name`: Optionally customise the name parameter passed 
 to the ansible.builtin.pip module when installing diskimage-builder. This can
 be used to install diskimage-builder from version control.
@@ -118,6 +125,34 @@ will be replaced with the newly built image if `os_images_upload` is set to `Tru
 
 `os_images_hide`: Whether or not to hide the images in Glance list. Hiding images is available as an option in image retirement/promotion process. Defaults to `False`.
 
+Changing platform architecture in os_images
+-------------------------------------------
+
+The target CPU architecture for each image defined in `os_images_list` may be set to any architecture supported by diskimage-builder with the `architecture` parameter.
+
+If it is unset, an image with the default diskimage-builder architecture (`x86_64`) will be built and optionally uploaded to Glance, with the Glance image property `cpu_arch` set to `x86_64`.
+
+If `architecture` is set for an image, consider also setting `properties.cpu_arch` to an architecture [supported by Glance](https://docs.openstack.org/glance/latest/admin/useful-image-properties.html#image-property-keys-and-values). An example is given below.
+
+```yaml
+   os_images_list:
+   - name: ubuntu
+     elements:
+       - ubuntu
+     packages:
+       - biosdevname
+     type: qcow2
+   - name: ubuntu-aarch64
+     architecture: arm64
+     elements:
+       - ubuntu
+     properties:
+       cpu_arch: aarch64
+     packages:
+       - biosdevname
+     type: qcow2
+```
+
 Dependencies
 ------------
 

roles/os_images/defaults/main.yml

@@ -45,8 +45,7 @@ os_images_common: cloud-init enable-serial-console stable-interface-names
 #     type: qcow2
 os_images_list: []
 # Common properties to apply to all glance images.
-os_images_common_properties:
-  cpu_arch: x86_64
+os_images_common_properties: {}
 
 # OpenStack authentication type: passed to the os_image Ansible module
 os_images_auth_type: password

roles/os_images/tasks/images.yml

@@ -83,8 +83,9 @@
 - name: Generate diskimage-builder images
   vars:
     dib_args: >-
-      {% if item.size is defined %}--image-size {{ item.size }}{% endif %} {% if item.type is defined %}-t {{ item.type }}{% endif %} {% if item.packages | default
-      %}-p {{ item.packages | join(',') }}{% endif %} {{ os_images_common }} {{ item.elements | join(' ') }} -o {{ item.name }}
+      {% if item.size is defined %}--image-size {{ item.size }}{% endif %} {% if item.type is defined %}-t {{ item.type }}{% endif %}
+      {% if item.packages | default %}-p {{ item.packages | join(',') }}{% endif %} {{ os_images_common }} {{ item.elements | join(' ') }}
+      -o {{ item.name }} {% if item.architecture is defined %}-a {{ item.architecture }}{% endif %}
   ansible.builtin.shell: . {{ os_images_dib_venv }}/bin/activate && disk-image-create {{ dib_args }} > {{ item.name }}.stdout 2> {{ item.name }}.stderr
   args:
     chdir: "{{ os_images_cache }}/{{ item.name }}"

roles/os_images/tasks/upload.yml

@@ -110,10 +110,19 @@
     container_format: bare
     disk_format: "{{ item.0.type | default('qcow2') }}"
     filename: "{{ os_images_cache }}/{{ item.0.name }}/{{ item.0.name }}.{{ item.0.type | default('qcow2') }}"
-    properties: "{{ os_images_common_properties | combine(item.0.properties | default({})) or omit }}"
+    properties: "{{ os_images_common_properties | combine(cpu_arch_properties) | combine(item.0.properties | default({})) or omit }}"
     kernel: "{{ item.1.id if is_baremetal else omit }}"
     ramdisk: "{{ item.2.id if is_baremetal else omit }}"
   vars:
+    # NOTE(m-anson): When architecture isn't defined for an
+    # image, assume that we should set cpu_arch: x86_64 as
+    # this is the diskimage-builder default.
+    cpu_arch_properties: >-
+      {{
+          {}
+          if item.0.architecture is defined
+          else {"cpu_arch": "x86_64"}
+      }}
     is_baremetal: "{{ item.0.elements is defined and 'baremetal' in item.0.elements }}"
     visibility: "{{ item.0.visibility | default(item.0.is_public | ternary('public', 'private') if item.0.is_public is defined else os_images_visibility) }}"
   with_together: