virtio-balloon: Check if balloon registration failed

Multiple balloon registrations are not allowed; check if the
registration with the qemu balloon api succeeded.  If not, fail the
device init.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index d685243728..ca5f125dae 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -788,6 +788,9 @@ static int virtio_balloon_init_pci(PCIDevice *pci_dev)
     VirtIODevice *vdev;
 
     vdev = virtio_balloon_init(&pci_dev->qdev);
+    if (!vdev) {
+        return -1;
+    }
     virtio_init_pci(proxy, vdev);
     return 0;
 }