Compute: Enable vGPU in Nova if exist on the host

Since Queens release Nova support vGPUs. In order to use it,
nova must have the right configuration. This commit will
enable vGPU in the nova configuration if some mdev[1] devices
exist on the compute node.

[1] - https://docs.openstack.org/nova/latest/admin/virtual-gpu.html#how-to-discover-a-gpu-type

Change-Id: Ia30b1a4fe38eb966f029f16142b8302707107bfc
Signed-off-by: Valentin Boucher <valentin.boucher@kontron.com>

tasks/main.yml

@@ -73,6 +73,11 @@
     - always
     - nova-config
 
+- include_tasks: nova_vgpu_detect.yml
+  tags:
+    - always
+    - nova-config
+
 - include_tasks: nova_pre_install.yml
   tags:
     - nova-install

tasks/nova_vgpu_detect.yml

@@ -0,0 +1,30 @@
+---
+# Copyright 2018, Kontron.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+- name: Check if the mdev folder exist
+  stat: path=/sys/class/mdev_bus
+  register: mdev_folder
+
+- name: Get mdev info content and store as var
+  command: "/bin/sh -c 'ls -1 /sys/class/mdev_bus/*/mdev_supported_types'"
+  register: mdev
+  when: mdev_folder.stat.exists
+
+- name: Register a fact for nova enabled_vgpu_types
+  set_fact:
+    enabled_vgpu_types: "{{ mdev.stdout_lines | unique }}"
+  when:
+    - mdev.stdout_lines is defined
+    - mdev.stdout_lines | length > 0

templates/nova.conf.j2

@@ -345,3 +345,8 @@ server_groups = {{ nova_quota_server_groups }}
 
 [upgrade_levels]
 compute=auto
+
+{% if enabled_vgpu_types is defined %}
+[devices]
+enabled_vgpu_types = {{ enabled_vgpu_types | join(',') }}
+{% endif %}