[Qemu-devel] [PATCH 2/3] balloon: report error if ballooning operation fails

[Amit Shah]

Ballooning operations can fail (e.g. driver in guest not available).
Let the user know of such an error condition instead of silently
ignoring errors.

Signed-off-by: Amit Shah <amit.s...@redhat.com>
---
 balloon.c           |    7 +++++--
 balloon.h           |    2 +-
 hw/virtio-balloon.c |    3 ++-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/balloon.c b/balloon.c
index 2b7131a..b05c9e2 100644
--- a/balloon.c
+++ b/balloon.c
@@ -63,12 +63,15 @@ void qemu_remove_balloon_handler(void *opaque)
 
 static int qemu_balloon(ram_addr_t target)
 {
+    int ret;
+
     if (!balloon_event_fn) {
         return -1;
     }
     trace_balloon_event(balloon_opaque, target);
-    balloon_event_fn(balloon_opaque, target);
-    return 0;
+    ret = balloon_event_fn(balloon_opaque, target);
+
+    return ret < 0 ? -1 : 0;
 }
 
 static int qemu_balloon_status(BalloonInfo *info)
diff --git a/balloon.h b/balloon.h
index b36abea..23b43bd 100644
--- a/balloon.h
+++ b/balloon.h
@@ -17,7 +17,7 @@
 #include "monitor.h"
 #include "qapi-types.h"
 
-typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
+typedef int (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
 typedef void (QEMUBalloonStatus)(void *opaque, BalloonInfo *info);
 
 int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
index e24a2bf..a8ecb51 100644
--- a/hw/virtio-balloon.c
+++ b/hw/virtio-balloon.c
@@ -180,7 +180,7 @@ static void virtio_balloon_stat(void *opaque, BalloonInfo 
*info)
                                VIRTIO_BALLOON_PFN_SHIFT);
 }
 
-static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
+static int virtio_balloon_to_target(void *opaque, ram_addr_t target)
 {
     VirtIOBalloon *dev = opaque;
 
@@ -191,6 +191,7 @@ static void virtio_balloon_to_target(void *opaque, 
ram_addr_t target)
         dev->num_pages = (ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT;
         virtio_notify_config(&dev->vdev);
     }
+    return 0;
 }
 
 static void virtio_balloon_save(QEMUFile *f, void *opaque)
-- 
1.7.7.3