Fix libvirt_type kvm for overcloud deploy

Apparently after merging https://review.openstack.org/#/c/584380
we got a consistent failure in the 3node and scn008 jobs:

invalid argument: could not find capabilities for domaintype=kvm

Try to enable kvm nested virtualization and switch back to default
qemu full emulation if kvm-{intel|amd} module cannot be loaded.

In addition, remove the current logic behind ansible_distribution
== 'RedHat' to enable kvm as this condition must run on overcloud
and also depends on cpu capabilities.

Change-Id: Iaa936facc5148ee6ff136db1524584785588c01e
Closes-Bug: #1784017

playbooks/multinode-undercloud.yml

@@ -79,3 +79,9 @@
   roles:
     - validate-undercloud
 
+- name: Set Libvirt type
+  hosts: overcloud
+  roles:
+    - set-libvirt-type
+  tags:
+    - overcloud-deploy

roles/overcloud-deploy/README.md

@@ -41,8 +41,10 @@ A description of the settable variables for this role should go here, including
   environment in THT.
 * `deploy_steps_ansible_workflow`: false/true - whether to deploy the overcloud with
   config-download Ansible steps from a Mistral workflow.
-* `libvirt_args`:  qemu|kvm default is kvm
+* `libvirt_args`: libvirt arguments used to deploy overcloud as the
-
+  --libvirt_type `virt_type`.
+* `virt_type`: qemu|kvm default is qemu. kvm is only enabled when kvm-{intel|amd}
+   kernel module can be loaded.
 
 
 Dependencies

roles/overcloud-deploy/defaults/main.yml

@@ -37,7 +37,7 @@ composable_args: ""
 extra_args: ""
 topology: ""
 ssl_overcloud: false
-libvirt_args: "--libvirt-type kvm"
+libvirt_args: "--libvirt-type {{ virt_type|default('qemu') }}"
 deploy_ha_ovn: false
 
 use_git_tht_repo: false

roles/overcloud-deploy/tasks/pre-deploy.yml

@@ -180,13 +180,6 @@
     - release not in ['mitaka', 'liberty']
     - set_overcloud_workers|bool
 
-- name: Use KVM for Red Hat distro
-  set_fact:
-    libvirt_args: "--libvirt-type kvm"
-  when:
-    - ansible_distribution is defined
-    - ansible_distribution == 'RedHat'
-
 - name: set container_args fact
   set_fact:
     container_args: >-

roles/set-libvirt-type/README.md

@@ -0,0 +1,45 @@
+set-libvirt-type
+================
+
+Set Libvirt type for overcloud deploy.
+This Ansible role allows provisioning overcloud with nested kvm or qemu full
+virtualization mode based on cpu and OS capabilities.
+
+Requirements
+------------
+
+No requirements.
+
+Role Variables
+--------------
+
+No variables.
+
+Dependencies
+------------
+
+No dependencies.
+
+Example Playbook
+----------------
+
+Including an example of how to use this role
+
+    ---
+    - name:  Set Libvirt type
+      hosts: overcloud
+      roles:
+        - set-libvirt-type
+      tags:
+        - overcloud-deploy
+
+
+License
+-------
+
+Apache 2.0
+
+Author Information
+------------------
+
+OpenStack

roles/set-libvirt-type/tasks/main.yml

@@ -0,0 +1,30 @@
+- name: Enable kvm nested virtualization
+  block:
+    - name: Check cpu vendor
+      set_fact:
+        cpu_vendor: "{{ item }}"
+      when: ansible_processor[1]|lower is search(item)
+      with_items:
+        - intel
+        - amd
+    - name: Fail if cpu vendor is undefined
+      fail:
+        msg: 'WARNING: Unknown/unsupported CPU vendor'
+      when: cpu_vendor is not defined
+    - name: Make sure the kvm module is present
+      modprobe:
+        name: kvm-{{ cpu_vendor }}
+        state: present
+        params: 'nested=1'
+      become: true
+    - name: Set kvm as virt type
+      set_fact:
+        virt_type: kvm
+    - debug:
+        msg: 'KVM nested virtualization Enabled.'
+  rescue:
+    - name: Set qemu as virt type
+      set_fact:
+        virt_type: qemu
+    - debug:
+        msg: 'WARNING: Running QEMU full emulation.'