MNAIO: Ensure that nested virt is enabled on host

Nested virtualization is important to improve VM performance
and enabling it is crucial to ensuring that VM images built
on one host work on boot on other hosts because the environment
is consistent.

In this patch add a task to enable it if it is available.

Change-Id: I812d8399cf45fab94f0f46976c9415591d45e463

multi-node-aio/playbooks/setup-host.yml

@@ -99,6 +99,42 @@
               ((_libguestfs_version.stdout is version('1.39.0', '>=')) and
                (_libguestfs_version.stdout is version('1.39.1', '<'))) }}"
 
+    # If the host had already installed kvm_intel.ko without nested=1, then
+    # re-load it now, honoring whatever is in qemu-system-x86.modprobe
+    # Exit codes:
+    # 0 - Nested virt already enabled
+    # 1 - Error
+    # 2 - Nested virt enabled by task (should show task as changed)
+    # 3 - Nested virt not available
+    - name: Ensure that nested virtualization is enabled (if it is available)
+      shell: |
+        INTEL_NESTED=/sys/module/kvm_intel/parameters/nested
+        if grep -q kvm_intel /proc/modules; then
+          echo "Intel CPU found. Checking for nested virtualization capabilities."
+          if [ -f ${INTEL_NESTED} ]; then
+            echo "Nested virtualization capability found. Checking if it is enabled."
+            v=$(cat ${INTEL_NESTED})
+            if [ "x${v}" != "xY" ]; then
+              echo "Nested virtualization not enabled. Enabling it now."
+              rmmod kvm_intel && modprobe kvm_intel
+              exit 2
+            else
+              echo "Nested virtualization already enabled."
+            fi
+          else
+            echo "Nested virtualization capability not found."
+            exit 3
+          fi
+        else
+          echo "Intel CPU not found."
+          exit 3
+        fi
+      args:
+        executable: /bin/bash
+      register: _enable_nested_virt
+      changed_when: _enable_nested_virt.rc == 2
+      failed_when: _enable_nested_virt.rc not in [0, 2, 3]
+
     - name: Ensure root has a .ssh directory
       file:
         path: /root/.ssh