monitor: Improve and document client_migrate_info protocol error

Protocol must be spice, vnc isn't implemented.  Fix up documentation.

Attempts to use vnc or any other unknown protocol yield the misleading
error message "Invalid parameter 'protocol'".  Improve it to
"Parameter 'protocol' expects spice".

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by. Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>

hmp-commands.hx

@@ -1011,17 +1011,17 @@ ETEXI
         .name       = "client_migrate_info",
         .args_type  = "protocol:s,hostname:s,port:i?,tls-port:i?,cert-subject:s?",
         .params     = "protocol hostname port tls-port cert-subject",
-        .help       = "send migration info to spice/vnc client",
+        .help       = "set migration information for remote display",
         .user_print = monitor_user_noop,
         .mhandler.cmd_new = client_migrate_info,
     },
 
 STEXI
 @item client_migrate_info @var{protocol} @var{hostname} @var{port} @var{tls-port} @var{cert-subject}
 @findex client_migrate_info
-Set the spice/vnc connection info for the migration target.  The spice/vnc
-server will ask the spice/vnc client to automatically reconnect using the
-new parameters (if specified) once the vm migration finished successfully.
+Set migration information for remote display.  This makes the server
+ask the client to automatically reconnect using the new parameters
+once migration finished successfully.  Only implemented for SPICE.
 ETEXI
 
     {

monitor.c

@@ -1063,7 +1063,7 @@ static int client_migrate_info(Monitor *mon, const QDict *qdict,
         return 0;
     }
 
-    qerror_report(QERR_INVALID_PARAMETER, "protocol");
+    qerror_report(QERR_INVALID_PARAMETER_VALUE, "protocol", "spice");
     return -1;
 }
 

qmp-commands.hx

@@ -784,23 +784,23 @@ EQMP
         .name       = "client_migrate_info",
         .args_type  = "protocol:s,hostname:s,port:i?,tls-port:i?,cert-subject:s?",
         .params     = "protocol hostname port tls-port cert-subject",
-        .help       = "send migration info to spice/vnc client",
+        .help       = "set migration information for remote display",
         .mhandler.cmd_new = client_migrate_info,
     },
 
 SQMP
 client_migrate_info
-------------------
+-------------------
 
-Set the spice/vnc connection info for the migration target.  The spice/vnc
-server will ask the spice/vnc client to automatically reconnect using the
-new parameters (if specified) once the vm migration finished successfully.
+Set migration information for remote display.  This makes the server
+ask the client to automatically reconnect using the new parameters
+once migration finished successfully.  Only implemented for SPICE.
 
 Arguments:
 
-- "protocol":     protocol: "spice" or "vnc" (json-string)
+- "protocol":     must be "spice" (json-string)
 - "hostname":     migration target hostname (json-string)
-- "port":         spice/vnc tcp port for plaintext channels (json-int, optional)
+- "port":         spice tcp port for plaintext channels (json-int, optional)
 - "tls-port":     spice tcp port for tls-secured channels (json-int, optional)
 - "cert-subject": server certificate subject (json-string, optional)