Add support to kvm nested virt

This patch aims to provide the ability for the user
to enable nested kvm virtualization in a kvm compute node
through nova_nested_virt_enabled variable, which its defaults is False.

Change-Id: I64417221fb3d74453d979b7198a0e916e7f4dd23

defaults/main.yml

@@ -269,6 +269,7 @@ nova_metadata_port: 8775
 ## Nova compute
 nova_enable_instance_password: True
 nova_force_config_drive: False
+nova_nested_virt_enabled: False
 
 ## Nova placement
 nova_placement_service_enabled: True

files/kvm.conf

@@ -0,0 +1,2 @@
+options kvm_intel nested=1 enable_apicv=0
+options kvm_amd nested=1

releasenotes/notes/add-nested-virt-1db2270e73d1b34.yaml

@@ -0,0 +1,7 @@
+---
+features:
+    - This role now optionally enables your compute nodes' KVM kernel
+      module nested virtualization capabilities, by setting nova_nested_virt_enabled
+      to true. Depending on your distribution and libvirt version, you might need to
+      set additional variables to fully enabled nested virtualization.
+      For details, please see https://docs.openstack.org/nova/latest/admin/configuration/hypervisor-kvm.html#nested-guest-support.

tasks/drivers/kvm/nova_compute_kvm.yml

@@ -17,6 +17,19 @@
   tags:
     - nova-install
 
+- name: Set nested kvm virt
+  copy:
+    src: kvm.conf
+    dest: /etc/modprobe.d/kvm.conf
+    owner: root
+    group: root
+    mode: 0644
+  when:
+    - nova_nested_virt_enabled | bool
+  tags:
+    - nova-config
+    - nova-kvm
+
 - name: Add nova user to libvirtd group
   user:
     name: "{{ nova_system_user_name }}"