Make arm64/aarch64 and x86_64 first-class citizens for images

Detect their glance cpu_arch property directly from their
architecture.

Author: m-bull

roles/os_images/README.md

@@ -59,8 +59,10 @@ mutually exclusive where each contain:
 * `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.
+  Glance images with the `cpu_arch: "x86_64"` image property. If architecture is set
+  to `arm64` or `aarch64`, Glance images with the `cpu_arch: "aarch64"` image property
+  When setting to other values, 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).
@@ -130,28 +132,9 @@ 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
-```
+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 it is set to `arm64` or `aarch64`, images will be uploaded to Glance with the Glance image property `cpu_arch` set to `aarch64`.
+
+If setting to a different `architecture`, 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).
 
 Dependencies
 ------------

roles/os_images/tasks/upload.yml

@@ -116,12 +116,21 @@
   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.
+    # this is the diskimage-builder default. If an architecture
+    # of arm64 or aarch64 is defined, set cpu_arch: aarch64. In
+    # all other cases, leave it up to the operator to set
+    # properties.cpu_arch.
     cpu_arch_properties: >-
       {{
-          {}
-          if item.0.architecture is defined
-          else {"cpu_arch": "x86_64"}
+          {} | combine(
+            {"cpu_arch": "x86_64"}
+            if item.0.architecture is not defined
+            else {}
+            ) | combine(
+            {"cpu_arch": "aarch64"}
+            if item.0.architecture is defined and item.0.architecture in ["arm64", "aarch64"]
+            else {}
+            )
       }}
     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) }}"