qemu: Parse current balloon value returned by query_balloon

Qemu once supported following memory stats which will returned by
"query_balloon":

    stat_put(dict, "actual", actual);
    stat_put(dict, "mem_swapped_in", dev->stats[VIRTIO_BALLOON_S_SWAP_IN]);
    stat_put(dict, "mem_swapped_out", dev->stats[VIRTIO_BALLOON_S_SWAP_OUT]);
    stat_put(dict, "major_page_faults", dev->stats[VIRTIO_BALLOON_S_MAJFLT]);
    stat_put(dict, "minor_page_faults", dev->stats[VIRTIO_BALLOON_S_MINFLT]);
    stat_put(dict, "free_mem", dev->stats[VIRTIO_BALLOON_S_MEMFREE]);
    stat_put(dict, "total_mem", dev->stats[VIRTIO_BALLOON_S_MEMTOT]);

But it later disabled all the stats except "actual" by commit
07b0403dfc2b2ac179ae5b48105096cc2d03375a.

libvirt doesn't parse "actual", so user will always see a empty result
with "virsh dommemstat $domain". Even qemu haven't disabled the stats,
we should support parsing "actual".

include/libvirt/libvirt.h.in

@@ -467,11 +467,13 @@ typedef enum {
      */
     VIR_DOMAIN_MEMORY_STAT_AVAILABLE       = 5,
 
+    /* Current balloon value (in KB). */
+    VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON  = 6,
     /*
      * The number of statistics supported by this version of the interface.
      * To add new statistics, add them to the enum and increase this value.
      */
-    VIR_DOMAIN_MEMORY_STAT_NR              = 6,
+    VIR_DOMAIN_MEMORY_STAT_NR              = 7,
 } virDomainMemoryStatTags;
 
 typedef struct _virDomainMemoryStat virDomainMemoryStatStruct;

src/libvirt.c

@@ -5750,6 +5750,8 @@ error:
  *     The amount of memory which is not being used for any purpose (in kb).
  * VIR_DOMAIN_MEMORY_STAT_AVAILABLE:
  *     The total amount of memory available to the domain's OS (in kb).
+ * VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON:
+ *     Current balloon value (in kb).
  *
  * Returns: The number of stats provided or -1 in case of failure.
  */

src/qemu/qemu_monitor_json.c

@@ -1119,6 +1119,18 @@ int qemuMonitorJSONGetMemoryStats(qemuMonitorPtr mon,
                 goto cleanup;
             }
 
+            if (virJSONValueObjectHasKey(data, "actual") && (got < nr_stats)) {
+                if (virJSONValueObjectGetNumberUlong(data, "actual", &mem) < 0) {
+                    qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                                    _("info balloon reply was missing balloon actual"));
+                    ret = -1;
+                    goto cleanup;
+                }
+                stats[got].tag = VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON;
+                stats[got].val = (mem/1024);
+                got++;
+            }
+
             if (virJSONValueObjectHasKey(data, "mem_swapped_in") && (got < nr_stats)) {
                 if (virJSONValueObjectGetNumberUlong(data, "mem_swapped_in", &mem) < 0) {
                     qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",

src/qemu/qemu_monitor_text.c

@@ -549,7 +549,9 @@ static int qemuMonitorParseExtraBalloonInfo(char *text,
             parseMemoryStat(&p, VIR_DOMAIN_MEMORY_STAT_UNUSED,
                             ",free_mem=", &stats[nr_stats_found]) ||
             parseMemoryStat(&p, VIR_DOMAIN_MEMORY_STAT_AVAILABLE,
-                            ",total_mem=", &stats[nr_stats_found]))
+                            ",total_mem=", &stats[nr_stats_found]) ||
+            parseMemoryStat(&p, VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON,
+                            ",actual=", &stats[nr_stats_found]))
             nr_stats_found++;
 
         /* Skip to the next label.  When *p is ',' the last match attempt

tools/virsh.c

@@ -1147,6 +1147,8 @@ cmdDomMemStat(vshControl *ctl, const vshCmd *cmd)
             vshPrint (ctl, "unused %llu\n", stats[i].val);
         if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_AVAILABLE)
             vshPrint (ctl, "available %llu\n", stats[i].val);
+        if (stats[i].tag == VIR_DOMAIN_MEMORY_STAT_ACTUAL_BALLOON)
+            vshPrint (ctl, "actual %llu\n", stats[i].val);
     }
 
     virDomainFree(dom);