Add migrate_incoming

Add migrate_incoming/migrate-incoming to start an incoming
migration.

Once a qemu has been started with
    -incoming defer

the migration can be started by issuing:
    migrate_incoming uri
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

hmp-commands.hx

@@ -919,6 +919,22 @@ STEXI
 @findex migrate_cancel
 Cancel the current VM migration.
 
+ETEXI
+
+    {
+        .name       = "migrate_incoming",
+        .args_type  = "uri:s",
+        .params     = "uri",
+        .help       = "Continue an incoming migration from an -incoming defer",
+        .mhandler.cmd = hmp_migrate_incoming,
+    },
+
+STEXI
+@item migrate_incoming @var{uri}
+@findex migrate_incoming
+Continue an incoming migration using the @var{uri} (that has the same syntax
+as the -incoming option).
+
 ETEXI
 
     {

hmp.c

@@ -1116,6 +1116,20 @@ void hmp_migrate_cancel(Monitor *mon, const QDict *qdict)
     qmp_migrate_cancel(NULL);
 }
 
+void hmp_migrate_incoming(Monitor *mon, const QDict *qdict)
+{
+    Error *err = NULL;
+    const char *uri = qdict_get_str(qdict, "uri");
+
+    qmp_migrate_incoming(uri, &err);
+
+    if (err) {
+        monitor_printf(mon, "%s\n", error_get_pretty(err));
+        error_free(err);
+        return;
+    }
+}
+
 void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict)
 {
     double value = qdict_get_double(qdict, "value");

hmp.h

@@ -60,6 +60,7 @@ void hmp_snapshot_delete_blkdev_internal(Monitor *mon, const QDict *qdict);
 void hmp_drive_mirror(Monitor *mon, const QDict *qdict);
 void hmp_drive_backup(Monitor *mon, const QDict *qdict);
 void hmp_migrate_cancel(Monitor *mon, const QDict *qdict);
+void hmp_migrate_incoming(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_speed(Monitor *mon, const QDict *qdict);
 void hmp_migrate_set_capability(Monitor *mon, const QDict *qdict);

migration/migration.c

@@ -432,6 +432,25 @@ void migrate_del_blocker(Error *reason)
     migration_blockers = g_slist_remove(migration_blockers, reason);
 }
 
+void qmp_migrate_incoming(const char *uri, Error **errp)
+{
+    Error *local_err = NULL;
+
+    if (!deferred_incoming) {
+        error_setg(errp, "'-incoming defer' is required for migrate_incoming");
+        return;
+    }
+
+    qemu_start_incoming_migration(uri, &local_err);
+
+    if (local_err) {
+        error_propagate(errp, local_err);
+        return;
+    }
+
+    deferred_incoming = false;
+}
+
 void qmp_migrate(const char *uri, bool has_blk, bool blk,
                  bool has_inc, bool inc, bool has_detach, bool detach,
                  Error **errp)

qapi-schema.json

@@ -1738,6 +1738,21 @@
 { 'command': 'migrate',
   'data': {'uri': 'str', '*blk': 'bool', '*inc': 'bool', '*detach': 'bool' } }
 
+##
+# @migrate-incoming
+#
+# Start an incoming migration, the qemu must have been started
+# with -incoming defer
+#
+# @uri: The Uniform Resource Identifier identifying the source or
+#       address to listen on
+#
+# Returns: nothing on success
+#
+# Since: 2.3
+##
+{ 'command': 'migrate-incoming', 'data': {'uri': 'str' } }
+
 # @xen-save-devices-state:
 #
 # Save the state of all devices to file. The RAM and the block devices

qmp-commands.hx

@@ -661,7 +661,36 @@ Example:
 <- { "return": {} }
 
 EQMP
-{
+
+    {
+        .name       = "migrate-incoming",
+        .args_type  = "uri:s",
+        .mhandler.cmd_new = qmp_marshal_input_migrate_incoming,
+    },
+
+SQMP
+migrate-incoming
+----------------
+
+Continue an incoming migration
+
+Arguments:
+
+- "uri": Source/listening URI (json-string)
+
+Example:
+
+-> { "execute": "migrate-incoming", "arguments": { "uri": "tcp::4446" } }
+<- { "return": {} }
+
+Notes:
+
+(1) QEMU must be started with -incoming defer to allow migrate-incoming to
+    be used
+(2) The uri format is the same as to -incoming
+
+EQMP
+    {
         .name       = "migrate-set-cache-size",
         .args_type  = "value:o",
         .mhandler.cmd_new = qmp_marshal_input_migrate_set_cache_size,