hmp: Add "calc_dirty_rate" and "info dirty_rate" cmds

These two commands are missing when adding the QMP sister commands.
Add them, so developers can play with them easier.

Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Hyman Huang(黄勇) <huangy81@chinatelecom.cn>
Message-Id: <4cc0039fc3ad6145136770cf3b0f056c09a2910b.1623027729.git.huangy81@chinatelecom.cn>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 2d21fe5..84dcc3a 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1727,3 +1727,17 @@
         .flags      = "p",
     },
 
+SRST
+``calc_dirty_rate`` *second*
+  Start a round of dirty rate measurement with the period specified in *second*.
+  The result of the dirty rate measurement may be observed with ``info
+  dirty_rate`` command.
+ERST
+
+    {
+        .name       = "calc_dirty_rate",
+        .args_type  = "second:l,sample_pages_per_GB:l?",
+        .params     = "second [sample_pages_per_GB]",
+        .help       = "start a round of guest dirty rate measurement",
+        .cmd        = hmp_calc_dirty_rate,
+    },