conf: Introduce 'pmem' element into xml for NVDIMM memory

The 'pmem' option allows users to specify whether the backend
storage of memory-backend-file is a real persistent memory:

<devices>
  ...
  <memory model='nvdimm' access='shared'>
      <source>
          <path>/dev/dax0.0</path>
          <pmem/>
      </source>
      <target>
          <size unit='MiB'>4094</size>
          <node>0</node>
          <label>
              <size unit='MiB'>2</size>
          </label>
      </target>
  </memory>
  ...
</devices>

Signed-off-by: Luyao Zhong <luyao.zhong@intel.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>

docs/formatdomain.html.in

@@ -8332,6 +8332,19 @@ qemu-kvm -net nic,model=? /dev/null
       </label>
     </target>
   </memory>
+  <memory model='nvdimm'>
+    <source>
+      <path>/dev/dax0.0</path>
+      <pmem/>
+    </source>
+    <target>
+      <size unit='KiB'>524288</size>
+      <node>1</node>
+      <label>
+        <size unit='KiB'>128</size>
+      </label>
+    </target>
+  </memory>
 </devices>
 ...
 </pre>
@@ -8422,6 +8435,17 @@ qemu-kvm -net nic,model=? /dev/null
               <span class="since">Since 5.0.0</span>
             </p>
           </dd>
+
+          <dt><code>pmem</code></dt>
+          <dd>
+            <p>
+              If persistent memory is supported and enabled by the hypervisor
+              in order to guarantee the persistence of writes to the vNVDIMM
+              backend, then use the <code>pmem</code> element in order to
+              utilize the feature.
+              <span class="since">Since 5.0.0</span>
+            </p>
+          </dd>
         </dl>
       </dd>
 

docs/schemas/domaincommon.rng

@@ -5393,6 +5393,11 @@
                 <ref name="scaledInteger"/>
               </element>
             </optional>
+            <optional>
+              <element name="pmem">
+                <empty/>
+              </element>
+            </optional>
           </interleave>
         </group>
       </choice>

src/conf/domain_conf.c

@@ -15785,6 +15785,9 @@ virDomainMemorySourceDefParseXML(xmlNodePtr node,
                                  &def->alignsize, false, false) < 0)
             goto cleanup;
 
+        if (virXPathBoolean("boolean(./pmem)", ctxt))
+            def->nvdimmPmem = true;
+
         break;
 
     case VIR_DOMAIN_MEMORY_MODEL_NONE:
@@ -22756,6 +22759,13 @@ virDomainMemoryDefCheckABIStability(virDomainMemoryDefPtr src,
                            src->alignsize, dst->alignsize);
             return false;
         }
+
+        if (src->nvdimmPmem != dst->nvdimmPmem) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("Target NVDIMM pmem flag doesn't match "
+                             "source NVDIMM pmem flag"));
+            return false;
+        }
     }
 
     return virDomainDeviceInfoCheckABIStability(&src->info, &dst->info);
@@ -26296,6 +26306,9 @@ virDomainMemorySourceDefFormat(virBufferPtr buf,
         if (def->alignsize)
             virBufferAsprintf(buf, "<alignsize unit='KiB'>%llu</alignsize>\n",
                               def->alignsize);
+
+        if (def->nvdimmPmem)
+            virBufferAddLit(buf, "<pmem/>\n");
         break;
 
     case VIR_DOMAIN_MEMORY_MODEL_NONE:

src/conf/domain_conf.h

@@ -2148,6 +2148,7 @@ struct _virDomainMemoryDef {
     unsigned long long pagesize; /* kibibytes */
     char *nvdimmPath;
     unsigned long long alignsize; /* kibibytes; valid only for NVDIMM */
+    bool nvdimmPmem; /* valid only for NVDIMM */
 
     /* target */
     int model; /* virDomainMemoryModel */

tests/qemuxml2argvdata/memory-hotplug-nvdimm-pmem.xml

@@ -0,0 +1,58 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <maxMemory slots='16' unit='KiB'>1099511627776</maxMemory>
+  <memory unit='KiB'>1267710</memory>
+  <currentMemory unit='KiB'>1267710</currentMemory>
+  <vcpu placement='static' cpuset='0-1'>2</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <idmap>
+    <uid start='0' target='1000' count='10'/>
+    <gid start='0' target='1000' count='10'/>
+  </idmap>
+  <cpu>
+    <topology sockets='2' cores='1' threads='1'/>
+    <numa>
+      <cell id='0' cpus='0-1' memory='219136' unit='KiB'/>
+    </numa>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-i686</emulator>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='ide' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+    </controller>
+    <controller type='usb' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
+    </memballoon>
+    <memory model='nvdimm' access='private'>
+      <source>
+        <path>/tmp/nvdimm</path>
+        <pmem/>
+      </source>
+      <target>
+        <size unit='KiB'>523264</size>
+        <node>0</node>
+      </target>
+      <address type='dimm' slot='0'/>
+    </memory>
+  </devices>
+</domain>

tests/qemuxml2xmloutdata/memory-hotplug-nvdimm-pmem.xml

@@ -0,0 +1 @@
+../qemuxml2argvdata/memory-hotplug-nvdimm-pmem.xml

tests/qemuxml2xmltest.c

@@ -1117,6 +1117,7 @@ mymain(void)
     DO_TEST("memory-hotplug-nvdimm-access", NONE);
     DO_TEST("memory-hotplug-nvdimm-label", NONE);
     DO_TEST("memory-hotplug-nvdimm-align", NONE);
+    DO_TEST("memory-hotplug-nvdimm-pmem", NONE);
     DO_TEST("net-udp", NONE);
 
     DO_TEST("video-virtio-gpu-device", NONE);