libvirt: Enable driver configuring PMEM namespaces

Add one configuration option CONF.libvirt.pmem_namespaces:
"$LABEL:$NSNAME[|$NSNAME][,$LABEL:$NSNAME[|$NSNAME]]"

e.g. "128G:ns0|ns1|ns2|ns3,262144MB:ns4|ns5,MEDIUM:ns6|ns7"

Change-Id: I98e5ddbd7a9f2211a16221b5049bc36452a49a75
Partially-Implements: blueprint virtual-persistent-memory
Co-Authored-By: He Jie Xu <hejie.xu@intel.com>

nova/conf/libvirt.py

@@ -1335,6 +1335,32 @@ maximum number of retry attempts that can be made to discover the NVMe device.
 """),
 ]
 
+
+libvirt_pmem_opts = [
+    cfg.ListOpt('pmem_namespaces',
+                item_type=cfg.types.String(),
+                default=[],
+                help="""
+Configure persistent memory(pmem) namespaces.
+
+These namespaces must have been already created on the host. This config
+option is in the following format::
+
+    "$LABEL:$NSNAME[|$NSNAME][,$LABEL:$NSNAME[|$NSNAME]]"
+
+* ``$NSNAME`` is the name of the pmem namespace.
+* ``$LABEL`` represents one resource class, this is used to generate
+      the resource class name as ``CUSTOM_PMEM_NAMESPACE_$LABEL``.
+
+For example::
+
+    [libvirt]
+    pmem_namespaces=128G:ns0|ns1|ns2|ns3,262144MB:ns4|ns5,MEDIUM:ns6|ns7
+
+"""),
+]
+
+
 ALL_OPTS = list(itertools.chain(
     libvirt_general_opts,
     libvirt_imagebackend_opts,
@@ -1354,6 +1380,7 @@ ALL_OPTS = list(itertools.chain(
     libvirt_volume_vzstorage_opts,
     libvirt_virtio_queue_sizes,
     libvirt_volume_nvmeof_opts,
+    libvirt_pmem_opts,
 ))
 
 

nova/virt/libvirt/driver.py

@@ -435,7 +435,8 @@ class LibvirtDriver(driver.ComputeDriver):
         self.cpu_models_mapping = {}
         self.cpu_model_flag_mapping = {}
 
-        self._vpmems_by_name, self._vpmems_by_rc = self._discover_vpmems()
+        self._vpmems_by_name, self._vpmems_by_rc = self._discover_vpmems(
+                vpmem_conf=CONF.libvirt.pmem_namespaces)
 
     def _discover_vpmems(self, vpmem_conf=None):
         """Discover vpmems on host and configuration.

releasenotes/notes/add-support-for-vpmem-libvirt-8b66add5b2d8f5f5.yaml

@@ -0,0 +1,24 @@
+---
+features:
+  - |
+    The libvirt driver now supports booting instances with virtual persistent
+    memory (vPMEM), also called persistent memory (PMEM) namespaces.
+    To enable vPMEM support, the user should specify the PMEM namespaces
+    in the ``nova.conf`` by using the configuration option
+    ``[libvirt]/pmem_namespaces``. For example::
+
+      [libvirt]
+      # pmem_namespaces=$LABEL:$NSNAME[|$NSNAME][,$LABEL:$NSNAME[|$NSNAME]]
+      pmem_namespaces = 128G:ns0|ns1|ns2|ns3,262144MB:ns4|ns5,MEDIUM:ns6|ns7
+
+    Only PMEM namespaces listed in the configuration file can be used by
+    instances. To identify the available PMEM namespaces on the host or create
+    new namespaces, the ``ndctl`` utility can be used::
+
+      ndctl create-namespace -m devdax -s $SIZE -M mem -n $NSNAME
+
+    Nova will invoke this utility to identify available PMEM namespaces.
+    Then users can specify vPMEM resources in a flavor by adding flavor's
+    extra specs::
+
+      openstack flavor set --property hw:pmem=6GB,64GB <flavor-id>