migration/hmp: add migrate_pause command

Wrapper for QMP command "migrate-pause".

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-25-peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 2fa387d..0734fea 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -974,6 +974,20 @@
 ETEXI
 
     {
+        .name       = "migrate_pause",
+        .args_type  = "",
+        .params     = "",
+        .help       = "Pause an ongoing migration (postcopy-only)",
+        .cmd        = hmp_migrate_pause,
+    },
+
+STEXI
+@item migrate_pause
+@findex migrate_pause
+Pause an ongoing migration.  Currently it only supports postcopy.
+ETEXI
+
+    {
         .name       = "migrate_set_cache_size",
         .args_type  = "value:o",
         .params     = "value",