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[v2,1/5] balloon: Don't allow multiple balloon handler registrations

Message ID 1f7b38242c65413430023e5019c97b11daede8bc.1311833521.git.amit.shah@redhat.com
State New
Headers show

Commit Message

Amit Shah July 28, 2011, 6:17 a.m. UTC 
Multiple balloon devices don't make sense; disallow more than one
registration attempt to register handlers.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 balloon.c |   12 ++++++++++--
 balloon.h |    4 ++--
 2 files changed, 12 insertions(+), 4 deletions(-)
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Patch

diff --git a/balloon.c b/balloon.c
index a938475..5200565 100644
--- a/balloon.c
+++ b/balloon.c
@@ -36,12 +36,20 @@  static QEMUBalloonEvent *balloon_event_fn;
 static QEMUBalloonStatus *balloon_stat_fn;
 static void *balloon_opaque;
 
-void qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
-                              QEMUBalloonStatus *stat_func, void *opaque)
+int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
+                             QEMUBalloonStatus *stat_func, void *opaque)
 {
+    if (balloon_event_fn || balloon_stat_fn || balloon_opaque) {
+        /* We're already registered one balloon handler.  How many can
+         * a guest really have?
+         */
+        error_report("Another balloon device already registered");
+        return -1;
+    }
     balloon_event_fn = event_func;
     balloon_stat_fn = stat_func;
     balloon_opaque = opaque;
+    return 0;
 }
 
 static int qemu_balloon(ram_addr_t target)
diff --git a/balloon.h b/balloon.h
index a6c31d5..3df14e6 100644
--- a/balloon.h
+++ b/balloon.h
@@ -20,8 +20,8 @@  typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
 typedef void (QEMUBalloonStatus)(void *opaque, MonitorCompletion cb,
                                  void *cb_data);
 
-void qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
-                              QEMUBalloonStatus *stat_func, void *opaque);
+int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
+			     QEMUBalloonStatus *stat_func, void *opaque);
 
 void monitor_print_balloon(Monitor *mon, const QObject *data);
 int do_info_balloon(Monitor *mon, MonitorCompletion cb, void *opaque);