[Qemu-devel] [PATCH] virtio: Tell the user what went wrong when event_notifier_init failed

[Thomas Huth <thuth@redhat.com>]

event_notifier_init() can fail in real life, for example when there
are not enough open file handles available (EMFILE) when using a lot
of devices. So instead of leaving the average user with a cryptic
error number only, print out a proper error message with strerror()
instead, so that the user has a better way to figure out what is
going on and that using "ulimit -n" might help here for example.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 hw/virtio/virtio-bus.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index 1313760..08e38fb 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -164,7 +164,8 @@ static int set_host_notifier_internal(DeviceState *proxy, VirtioBusState *bus,
     if (assign) {
         r = event_notifier_init(notifier, 1);
         if (r < 0) {
-            error_report("%s: unable to init event notifier: %d", __func__, r);
+            error_report("%s: unable to init event notifier: %s (%d)",
+                         __func__, strerror(-r), r);
             return r;
         }
         virtio_queue_set_host_notifier_fd_handler(vq, true, set_handler);
-- 
1.8.3.1