Add a new qmp command to start/stop replication

We can call this qmp command to start/stop replication outside of qemu.
Like Xen colo need this function.
Signed-off-by: NZhang Chen <zhangchen.fnst@cn.fujitsu.com>
Signed-off-by: NWen Congyang <wencongyang@gmail.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NStefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Signed-off-by: NStefano Stabellini <sstabellini@kernel.org>

migration/colo.c

@@ -19,6 +19,8 @@
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "migration/failover.h"
+#include "replication.h"
+#include "qmp-commands.h"
 
 static bool vmstate_loading;
 
@@ -147,6 +149,30 @@ void colo_do_failover(MigrationState *s)
     }
 }
 
+void qmp_xen_set_replication(bool enable, bool primary,
+                             bool has_failover, bool failover,
+                             Error **errp)
+{
+    ReplicationMode mode = primary ?
+                           REPLICATION_MODE_PRIMARY :
+                           REPLICATION_MODE_SECONDARY;
+
+    if (has_failover && enable) {
+        error_setg(errp, "Parameter 'failover' is only for"
+                   " stopping replication");
+        return;
+    }
+
+    if (enable) {
+        replication_start_all(mode, errp);
+    } else {
+        if (!has_failover) {
+            failover = NULL;
+        }
+        replication_stop_all(failover, failover ? NULL : errp);
+    }
+}
+
 static void colo_send_message(QEMUFile *f, COLOMessage msg,
                               Error **errp)
 {

qapi-schema.json

@@ -5989,6 +5989,31 @@
 ##
 { 'command': 'xen-load-devices-state', 'data': {'filename': 'str'} }
 
+##
+# @xen-set-replication:
+#
+# Enable or disable replication.
+#
+# @enable: true to enable, false to disable.
+#
+# @primary: true for primary or false for secondary.
+#
+# @failover: #optional true to do failover, false to stop. but cannot be
+#            specified if 'enable' is true. default value is false.
+#
+# Returns: nothing.
+#
+# Example:
+#
+# -> { "execute": "xen-set-replication",
+#      "arguments": {"enable": true, "primary": false} }
+# <- { "return": {} }
+#
+# Since: 2.9
+##
+{ 'command': 'xen-set-replication',
+  'data': { 'enable': 'bool', 'primary': 'bool', '*failover' : 'bool' } }
+
 ##
 # @GICCapability:
 #