Add nova file_backed_memory and memory_backing_dir support for qemu.conf

The libvirt driver now allows utilizing file backed memory for qemu/KVM
virtual machines, via a new configuration attribute
``[libvirt]/file_backed_memory``, defaulting to 0 (disabled).

``[libvirt]/file_backed_memory`` specifies the available capacity in MiB
for file backed memory, at the directory configured for
``memory_backing_dir`` in libvirt's ``qemu.conf``. When enabled, the
libvirt driver will report the configured value for the total memory
capacity of the node, and will report used memory as the sum of all
configured guest memory.

Running Nova with file_backed_memory requires libvirt version 4.0.0 and
qemu version 2.6.0

This introduces parameters QemuMemoryBackingDir and NovaLibvirtFileBackedMemory

Resolves-Bug: 1793687
Depends-On: I0d9eb21fcab01266e501b7fc63c5b2bbb244956a

Change-Id: I47e2f92fb2ed3e66d4bf31814eac9090382ef4e1

docker/services/nova-libvirt.yaml

@@ -125,6 +125,14 @@ parameters:
     type: string
     tags:
       - role_specific
+  QemuMemoryBackingDir:
+    type: string
+    description: >
+      Directory used for memoryBacking source if configured as file.
+      NOTE: big files will be stored here
+    default: ''
+    tags:
+      - role_specific
 
 conditions:
 
@@ -165,6 +173,11 @@ conditions:
       - {get_param: LibvirtVncCACert}
       - ''
 
+  memory_backing_dir_set:
+    not:
+      equals:
+      - {get_param: QemuMemoryBackingDir}
+      - ''
 
 resources:
   RoleParametersValue:
@@ -175,9 +188,11 @@ resources:
         map_replace:
           - map_replace:
             - vhostuser_socket_group: VhostuserSocketGroup
+              memory_backing_dir: QemuMemoryBackingDir
             - values: {get_param: [RoleParameters]}
           - values:
               VhostuserSocketGroup: {get_param: VhostuserSocketGroup}
+              QemuMemoryBackingDir: {get_param: QemuMemoryBackingDir}
 
 
   ContainersCommon:
@@ -361,6 +376,15 @@ outputs:
                                 - get_param: LibvirtVncCACert
                       - /etc/pki/libvirt-vnc:/var/lib/kolla/config_files/src-libvirt-vnc-pki:ro
                     - null
+                -
+                  if:
+                    - memory_backing_dir_set
+                    -
+                      - str_replace:
+                          template: "MEMORY_BACKING_DIR:MEMORY_BACKING_DIR"
+                          params:
+                            MEMORY_BACKING_DIR: {get_attr: [RoleParametersValue, value, memory_backing_dir]}
+                    - null
             environment:
               - KOLLA_CONFIG_STRATEGY=COPY_ALWAYS
         step_4:

puppet/services/nova-compute.yaml

@@ -189,6 +189,13 @@ parameters:
       - allowed_values: [ 256, 512, 1024 ]
     tags:
       - role_specific
+  NovaLibvirtFileBackedMemory:
+    description: >
+      Available capacity in MiB for file-backed memory.
+    default: 0
+    type: number
+    tags:
+      - role_specific
 
 conditions:
   enable_live_migration_tunnelled:
@@ -196,6 +203,12 @@ conditions:
       - equals: [{get_param: NovaNfsEnabled}, true]
       - equals: [{get_param: NovaEnableRbdBackend}, true]
 
+  libvirt_file_backed_memory_enabled:
+    not:
+      or:
+      -  equals: [{get_param: NovaLibvirtFileBackedMemory}, '']
+      -  equals: [{get_param: NovaLibvirtFileBackedMemory}, 0]
+
 resources:
   NovaBase:
     type: ./nova-base.yaml
@@ -224,6 +237,7 @@ resources:
               nova::compute::resume_guests_state_on_host_boot: NovaResumeGuestsStateOnHostBoot
               nova::compute::libvirt::rx_queue_size: NovaLibvirtRxQueueSize
               nova::compute::libvirt::tx_queue_size: NovaLibvirtTxQueueSize
+              nova::compute::libvirt::file_backed_memory: NovaLibvirtFileBackedMemory
             - values: {get_param: [RoleParameters]}
           - values:
               NovaVcpuPinSet: {get_param: NovaVcpuPinSet}
@@ -234,6 +248,7 @@ resources:
               NovaResumeGuestsStateOnHostBoot: {get_param: NovaResumeGuestsStateOnHostBoot}
               NovaLibvirtRxQueueSize: {get_param: NovaLibvirtRxQueueSize}
               NovaLibvirtTxQueueSize: {get_param: NovaLibvirtTxQueueSize}
+              NovaLibvirtFileBackedMemory: {get_param: NovaLibvirtFileBackedMemory}
 
 outputs:
   role_data:
@@ -313,6 +328,12 @@ outputs:
             nova::vncproxy::common::vncproxy_host: {get_param: [EndpointMap, NovaVNCProxyPublic, host_nobrackets]}
             nova::vncproxy::common::vncproxy_port: {get_param: [EndpointMap, NovaVNCProxyPublic, port]}
             nova::compute::verify_glance_signatures: {get_param: [VerifyGlanceSignatures]}
+            # if libvirt_file_backed_memory_enabled we have to set ram_allocation_ratio to 1.0
+            nova::ram_allocation_ratio:
+              if:
+              - libvirt_file_backed_memory_enabled
+              - '1.0'
+              - null
       step_config: |
         # TODO(emilien): figure how to deal with libvirt profile.
         # We'll probably treat it like we do with Neutron plugins.

puppet/services/nova-libvirt.yaml

@@ -130,6 +130,14 @@ parameters:
     description: The password for the libvirt service when TLS is enabled
     type: string
     hidden: true
+  QemuMemoryBackingDir:
+    type: string
+    description: >
+      Directory used for memoryBacking source if configured as file.
+      NOTE: big files will be stored here
+    default: ''
+    tags:
+      - role_specific
 
 conditions:
 
@@ -173,6 +181,20 @@ resources:
       RoleName: {get_param: RoleName}
       RoleParameters: {get_param: RoleParameters}
 
+  # Merging role-specific parameters (RoleParameters) with the default parameters.
+  # RoleParameters will have the precedence over the default parameters.
+  RoleParametersValue:
+    type: OS::Heat::Value
+    properties:
+      type: json
+      value:
+        map_replace:
+          - map_replace:
+            - nova::compute::libvirt::qemu::memory_backing_dir: QemuMemoryBackingDir
+            - values: {get_param: [RoleParameters]}
+          - values:
+              QemuMemoryBackingDir: {get_param: QemuMemoryBackingDir}
+
 outputs:
   role_data:
     description: Role data for the Libvirt service.
@@ -182,6 +204,7 @@ outputs:
       config_settings:
         map_merge:
           - get_attr: [NovaBase, role_data, config_settings]
+          - get_attr: [RoleParametersValue, value]
           # we include ::nova::compute::libvirt::services in nova/libvirt profile
           - nova::compute::libvirt::manage_libvirt_services: false
           # we manage migration in nova common puppet profile

releasenotes/notes/nova_file_backed_memory_and_memory_backing_dir_support_for_qemu-accfda4919b3d9dd.yaml

@@ -0,0 +1,18 @@
+---
+features:
+  - |
+    Add nova file_backed_memory and memory_backing_dir support for qemu.conf
+
+    The libvirt driver now allows utilizing file backed memory for qemu/KVM
+    virtual machines, via a new configuration attribute
+    ``[libvirt]/file_backed_memory``, defaulting to 0 (disabled).
+
+    ``[libvirt]/file_backed_memory`` specifies the available capacity in MiB
+    for file backed memory, at the directory configured for
+    ``memory_backing_dir`` in libvirt's ``qemu.conf``. When enabled, the
+    libvirt driver will report the configured value for the total memory
+    capacity of the node, and will report used memory as the sum of all
+    configured guest memory.
+
+    Running Nova with file_backed_memory requires libvirt version 4.0.0 and
+    qemu version 2.6.0