replay: implement replay-seek command

This patch adds hmp/qmp commands replay_seek/replay-seek that proceed
the execution to the specified instruction count.
The command automatically loads nearest snapshot and replays the execution
to find the desired instruction count.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Acked-by: Markus Armbruster <armbru@redhat.com>

--

v4 changes:
 - fixed HMP command description indent
 - removed useless error_free call
Message-Id: <160174521180.12451.14033112911009278753.stgit@pasha-ThinkPad-X280>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 7680d0b..e43ce60 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1837,6 +1837,24 @@
 ERST
 
     {
+        .name       = "replay_seek",
+        .args_type  = "icount:i",
+        .params     = "icount",
+        .help       = "replay execution to the specified instruction count",
+        .cmd        = hmp_replay_seek,
+    },
+
+SRST
+``replay_seek`` *icount*
+  Automatically proceed to the instruction count *icount*, when
+  replaying the execution. The command automatically loads nearest
+  snapshot and replays the execution to find the desired instruction.
+  When there is no preceding snapshot or the execution is not replayed,
+  then the command fails.
+  *icount* for the reference may be observed with ``info replay`` command.
+ERST
+
+    {
         .name       = "info",
         .args_type  = "item:s?",
         .params     = "[subcommand]",