From: Chun Feng Wu <danielwuwy@163.com>

For hot attaching/detaching
* Leverage qemuBlockThrottleFiltersData to prepare attaching/detaching
  throttle filter data for qemuMonitorBlockdevAdd and qemuMonitorBlockdevDel
* For hot attaching, within qemuDomainAttachDiskGeneric,prepare throttle
  filters json data, and create corresponding blockdev for QMP request
  ("blockdev-add" with "driver":"throttle")
* Each filter has a nodename, and those filters are chained up,
  create them in sequence, and delete them reversely
* Delete filters by "qemuBlockThrottleFiltersDetach"("blockdev-del")
  when detaching device

For throttle group commandline
* Add qemuBuildThrottleGroupCommandLine in qemuBuildCommandLine to add
  "object" of throttle-group
* Verify throttle group definition when lauching vm
* Check QEMU_CAPS_OBJECT_JSON before "qemuBuildObjectCommandlineFromJSON",
  which is to build "-object" option

For throttle filter commandline
* Add qemuBuildDiskThrottleFiltersCommandLine in qemuBuildDiskCommandLine
  to add "blockdev"

Signed-off-by: Chun Feng Wu <danielwuwy@163.com>
---
 src/qemu/qemu_command.c | 99 +++++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_hotplug.c | 25 +++++++++++
 2 files changed, 124 insertions(+)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 0c119c8827..19c8ab1b7f 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -2022,6 +2022,99 @@ qemuBuildBlockStorageSourceAttachDataCommandline(virCommand *cmd,
 }
 
 
+static bool
+qemuDiskConfigThrottleGroupEnabled(const virDomainThrottleGroupDef *group)
+{
+    return !!group->group_name &&
+           virDomainBlockIoTuneInfoHasAny(group);
+}
+
+
+/**
+ * qemuBuildThrottleGroupCommandLine:
+ * @cmd: the command to modify
+ * @def: domain definition
+ * @qemuCaps: qemu capabilities object
+ *
+ * build throttle group object in json format
+ */
+static int
+qemuBuildThrottleGroupCommandLine(virCommand *cmd,
+                                  const virDomainDef *def,
+                                  virQEMUCaps *qemuCaps)
+{
+    size_t i;
+
+    for (i = 0; i < def->nthrottlegroups; i++) {
+        g_autoptr(virJSONValue) props = NULL;
+        g_autoptr(virJSONValue) limits = virJSONValueNewObject();
+        virDomainThrottleGroupDef *group = def->throttlegroups[i];
+        /* prefix group name with "throttle-" in QOM */
+        g_autofree char *prefixed_group_name = g_strdup_printf("throttle-%s", group->group_name);
+
+        if (!qemuDiskConfigThrottleGroupEnabled(group)) {
+            continue;
+        }
+
+        if (qemuMonitorThrottleGroupLimits(limits, group) < 0)
+            return -1;
+
+        if (qemuMonitorCreateObjectProps(&props, "throttle-group", prefixed_group_name,
+                                         "a:limits", &limits,
+                                         NULL) < 0)
+            return -1;
+
+        /* this throttle group feature requires "QEMU_CAPS_OBJECT_JSON" */
+        if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_JSON)) {
+            virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                           _("This QEMU doesn't support throttle group creation"));
+            return -1;
+        }
+        if (qemuBuildObjectCommandlineFromJSON(cmd, props, qemuCaps) < 0)
+            return -1;
+    }
+
+    return 0;
+}
+
+
+static int
+qemuBuildBlockThrottleFilterCommandline(virCommand *cmd,
+                                        qemuBlockThrottleFilterAttachData *data)
+{
+    if (data->filterProps) {
+        g_autofree char *tmp = NULL;
+        if (!(tmp = virJSONValueToString(data->filterProps, false)))
+            return -1;
+
+        virCommandAddArgList(cmd, "-blockdev", tmp, NULL);
+    }
+
+    return 0;
+}
+
+
+static int
+qemuBuildDiskThrottleFiltersCommandLine(virCommand *cmd,
+                                        virDomainDiskDef *disk)
+{
+    g_autoptr(qemuBlockThrottleFiltersData) data = NULL;
+    size_t i;
+
+    data = qemuBuildThrottleFiltersAttachPrepareBlockdev(disk);
+    if (!data)
+        return -1;
+
+    for (i = 0; i < data->nfilterdata; i++) {
+        if (qemuBuildBlockThrottleFilterCommandline(cmd,
+                                                    data->filterdata[i]) < 0)
+            return -1;
+    }
+
+    return 0;
+}
+
+
 static int
 qemuBuildDiskSourceCommandLine(virCommand *cmd,
                                virDomainDiskDef *disk,
@@ -2079,6 +2172,9 @@ qemuBuildDiskCommandLine(virCommand *cmd,
     if (qemuBuildDiskSourceCommandLine(cmd, disk, qemuCaps) < 0)
         return -1;
 
+    if (qemuBuildDiskThrottleFiltersCommandLine(cmd, disk) < 0)
+        return -1;
+
     /* SD cards are currently instantiated via -drive if=sd, so the -device
      * part must be skipped */
     if (qemuDiskBusIsSD(disk->bus))
@@ -10435,6 +10531,9 @@ qemuBuildCommandLine(virDomainObj *vm,
     if (qemuBuildIOThreadCommandLine(cmd, def, qemuCaps) < 0)
         return NULL;
 
+    if (qemuBuildThrottleGroupCommandLine(cmd, def, qemuCaps) < 0)
+        return NULL;
+
     if (virDomainNumaGetNodeCount(def->numa) &&
         qemuBuildNumaCommandLine(cfg, def, cmd, priv) < 0)
         return NULL;
diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
index bddd553c88..bf001aa902 100644
--- a/src/qemu/qemu_hotplug.c
+++ b/src/qemu/qemu_hotplug.c
@@ -708,6 +708,7 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
                             virDomainAsyncJob asyncJob)
 {
     g_autoptr(qemuBlockStorageSourceChainData) data = NULL;
+    g_autoptr(qemuBlockThrottleFiltersData) filterData = NULL;
     qemuDomainObjPrivate *priv = vm->privateData;
     g_autoptr(virJSONValue) devprops = NULL;
     bool extensionDeviceAttached = false;
@@ -746,6 +747,19 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
         if (rc < 0)
             goto rollback;
 
+        /* Setup throttling filters
+         * add additional "blockdev-add"(throttle filter) between "blockdev-add" (qemuBlockStorageSourceChainAttach) and "device_add" (qemuDomainAttachExtensionDevice)
+         */
+        if ((filterData = qemuBuildThrottleFiltersAttachPrepareBlockdev(disk))) {
+            if (qemuDomainObjEnterMonitorAsync(vm, asyncJob) < 0)
+                return -1;
+            /* QMP requests("blockdev-add" with "driver":"throttle") to QEMU */
+            rc = qemuBlockThrottleFiltersAttach(priv->mon, filterData);
+            qemuDomainObjExitMonitor(vm);
+            if (rc < 0)
+                goto rollback;
+        }
+
         if (disk->transient) {
             g_autoptr(qemuBlockStorageSourceAttachData) backend = NULL;
             g_autoptr(GHashTable) blockNamedNodeData = NULL;
@@ -817,6 +831,8 @@ qemuDomainAttachDiskGeneric(virDomainObj *vm,
     if (extensionDeviceAttached)
         ignore_value(qemuDomainDetachExtensionDevice(priv->mon, &disk->info));
 
+    qemuBlockThrottleFiltersDetach(priv->mon, filterData);
+
     qemuBlockStorageSourceChainDetach(priv->mon, data);
 
     qemuDomainObjExitMonitor(vm);
@@ -4642,6 +4658,7 @@ qemuDomainRemoveDiskDevice(virQEMUDriver *driver,
 {
     qemuDomainDiskPrivate *diskPriv = QEMU_DOMAIN_DISK_PRIVATE(disk);
     g_autoptr(qemuBlockStorageSourceChainData) diskBackend = NULL;
+    g_autoptr(qemuBlockThrottleFiltersData) filterData = NULL;
     size_t i;
     qemuDomainObjPrivate *priv = vm->privateData;
     int ret = -1;
@@ -4680,6 +4697,14 @@ qemuDomainRemoveDiskDevice(virQEMUDriver *driver,
         }
     }
 
+    qemuDomainObjEnterMonitor(vm);
+    /* QMP request("blockdev-del") to QEMU to delete throttle filter*/
+    if ((filterData = qemuBuildThrottleFiltersDetachPrepareBlockdev(disk))) {
+        /* "qemuBlockThrottleFiltersDetach" is used in rollback within "qemuDomainAttachDiskGeneric" as well */
+        qemuBlockThrottleFiltersDetach(priv->mon, filterData);
+    }
+    qemuDomainObjExitMonitor(vm);
+
     qemuDomainObjEnterMonitor(vm);
 
     if (diskBackend)
-- 
2.39.5 (Apple Git-154)