conf: create memory bandwidth monitor.

Following domain configuration changes create two memory bandwidth
monitors: one is monitoring the bandwidth consumed by vCPU 0,
another is for vCPU 5.

```
               <cputune>
                 <memorytune vcpus='0-4'>
                   <node id='0' bandwidth='20'/>
                   <node id='1' bandwidth='30'/>
       +           <monitor vcpus='0'/>
                 </memorytune>
       +         <memorytune vcpus='5'>
       +           <monitor vcpus='5'/>
       +         </memorytune>

               </cputune>
    ```

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Huaqiang <huaqiang.wang@intel.com>

docs/schemas/domaincommon.rng

@@ -1023,14 +1023,21 @@
               <ref name='cpuset'/>
             </attribute>
             <oneOrMore>
-              <element name="node">
+              <choice>
-                <attribute name="id">
+                <element name="node">
-                  <ref name='unsignedInt'/>
+                  <attribute name="id">
-                </attribute>
+                    <ref name='unsignedInt'/>
-                <attribute name="bandwidth">
+                  </attribute>
-                  <ref name='unsignedInt'/>
+                  <attribute name="bandwidth">
-                </attribute>
+                    <ref name='unsignedInt'/>
-              </element>
+                  </attribute>
+                </element>
+                <element name="monitor">
+                  <attribute name="vcpus">
+                    <ref name='cpuset'/>
+                  </attribute>
+                </element>
+              </choice>
             </oneOrMore>
           </element>
         </zeroOrMore>

src/conf/domain_conf.c

@@ -19711,10 +19711,14 @@ virDomainMemorytuneDefParse(virDomainDefPtr def,
 {
     VIR_XPATH_NODE_AUTORESTORE(ctxt);
     virDomainResctrlDefPtr resctrl = NULL;
+    virDomainResctrlDefPtr newresctrl = NULL;
     g_autoptr(virBitmap) vcpus = NULL;
     g_autofree xmlNodePtr *nodes = NULL;
     g_autoptr(virResctrlAlloc) alloc = NULL;
     ssize_t i = 0;
+    size_t nmons = 0;
+    size_t ret = -1;
+
     int n;
 
     ctxt->node = node;
@@ -19741,29 +19745,44 @@ virDomainMemorytuneDefParse(virDomainDefPtr def,
             return -1;
     }
 
+    /* First, parse <memorytune/node> element if any <node> element exists */
     for (i = 0; i < n; i++) {
         if (virDomainMemorytuneDefParseMemory(ctxt, nodes[i], alloc) < 0)
             return -1;
     }
 
-    if (n == 0)
-        return 0;
-
     /*
      * If this is a new allocation, format ID and append to resctrl, otherwise
      * just update the existing alloc information, which is done in above
      * virDomainMemorytuneDefParseMemory */
     if (!resctrl) {
-        if (!(resctrl = virDomainResctrlNew(node, alloc, vcpus, flags)))
+        if (!(newresctrl = virDomainResctrlNew(node, alloc, vcpus, flags)))
             return -1;
 
-        if (VIR_APPEND_ELEMENT(def->resctrls, def->nresctrls, resctrl) < 0) {
+        resctrl = newresctrl;
-            virDomainResctrlDefFree(resctrl);
-            return -1;
-        }
     }
 
-    return 0;
+    /* Next, parse <memorytune/monitor> element */
+    nmons = resctrl->nmonitors;
+    if (virDomainResctrlMonDefParse(def, ctxt, node,
+                                    VIR_RESCTRL_MONITOR_TYPE_MEMBW,
+                                    resctrl) < 0)
+        goto cleanup;
+
+    nmons = resctrl->nmonitors - nmons;
+    /* Now @nmons contains the new <monitor> element number found in current
+     * <memorytune> element, and @n holds the number of new <node> element,
+     * only append the new @newresctrl object to domain if any of them is
+     * not zero. */
+    if (newresctrl && (nmons || n)) {
+        if (VIR_APPEND_ELEMENT(def->resctrls, def->nresctrls, newresctrl) < 0)
+            goto cleanup;
+    }
+
+    ret = 0;
+ cleanup:
+    virDomainResctrlDefFree(newresctrl);
+    return ret;
 }
 
 
@@ -27630,12 +27649,19 @@ virDomainMemorytuneDefFormat(virBufferPtr buf,
 {
     g_auto(virBuffer) childrenBuf = VIR_BUFFER_INIT_CHILD(buf);
     g_autofree char *vcpus = NULL;
+    size_t i = 0;
 
     if (virResctrlAllocForeachMemory(resctrl->alloc,
                                      virDomainMemorytuneDefFormatHelper,
                                      &childrenBuf) < 0)
         return -1;
 
+    for (i = 0; i< resctrl->nmonitors; i++) {
+        if (virDomainResctrlMonDefFormatHelper(resctrl->monitors[i],
+                                               VIR_RESCTRL_MONITOR_TYPE_MEMBW,
+                                               &childrenBuf) < 0)
+            return -1;
+    }
 
     if (!virBufferUse(&childrenBuf))
         return 0;

tests/genericxml2xmlindata/memorytune.xml

@@ -10,12 +10,17 @@
       <cache id='1' level='3' type='both' size='768' unit='KiB'/>
     </cachetune>
     <memorytune vcpus='0-1'>
+      <monitor vcpus='0-1'/>
       <node id='0' bandwidth='20'/>
+      <monitor vcpus='0'/>
       <node id='1' bandwidth='30'/>
     </memorytune>
     <memorytune vcpus='3'>
       <node id='0' bandwidth='50'/>
     </memorytune>
+    <memorytune vcpus='2'>
+      <monitor vcpus='2'/>
+    </memorytune>
   </cputune>
   <os>
     <type arch='i686' machine='pc'>hvm</type>

tests/genericxml2xmloutdata/memorytune.xml

@@ -0,0 +1,42 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>4</vcpu>
+  <cputune>
+    <cachetune vcpus='0-1'>
+      <cache id='0' level='3' type='both' size='768' unit='KiB'/>
+      <cache id='1' level='3' type='both' size='768' unit='KiB'/>
+    </cachetune>
+    <memorytune vcpus='0-1'>
+      <node id='0' bandwidth='20'/>
+      <node id='1' bandwidth='30'/>
+      <monitor vcpus='0-1'/>
+      <monitor vcpus='0'/>
+    </memorytune>
+    <memorytune vcpus='3'>
+      <node id='0' bandwidth='50'/>
+    </memorytune>
+    <memorytune vcpus='2'>
+      <monitor vcpus='2'/>
+    </memorytune>
+  </cputune>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <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>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/genericxml2xmltest.c

@@ -173,7 +173,7 @@ mymain(void)
                  TEST_COMPARE_DOM_XML2XML_RESULT_FAIL_PARSE);
     DO_TEST_FULL("cachetune-colliding-monitor", false, true,
                  TEST_COMPARE_DOM_XML2XML_RESULT_FAIL_PARSE);
-    DO_TEST("memorytune");
+    DO_TEST_DIFFERENT("memorytune");
     DO_TEST_FULL("memorytune-colliding-allocs", false, true,
                  TEST_COMPARE_DOM_XML2XML_RESULT_FAIL_PARSE);
     DO_TEST_FULL("memorytune-colliding-cachetune", false, true,