Re: [Qemu-devel] [PATCH 2/2] virtio-balloon: Check if balloon registration failed

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 27, 2011 at 12:31:08PM +0530, Amit Shah wrote:
> 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>
> ---
>  hw/virtio-balloon.c |   10 +++++++++-
>  hw/virtio-pci.c     |    3 +++
>  2 files changed, 12 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/virtio-balloon.c b/hw/virtio-balloon.c
> index 2ba7e95..304a31a 100644
> --- a/hw/virtio-balloon.c
> +++ b/hw/virtio-balloon.c
> @@ -269,6 +269,7 @@ static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
>  VirtIODevice *virtio_balloon_init(DeviceState *dev)
>  {
>      VirtIOBalloon *s;
> +    int ret;
>  
>      s = (VirtIOBalloon *)virtio_common_init("virtio-balloon",
>                                              VIRTIO_ID_BALLOON,
> @@ -278,12 +279,19 @@ VirtIODevice *virtio_balloon_init(DeviceState *dev)
>      s->vdev.set_config = virtio_balloon_set_config;
>      s->vdev.get_features = virtio_balloon_get_features;
>  
> +    ret = qemu_add_balloon_handler(virtio_balloon_to_target,
> +                                   virtio_balloon_stat, s);
> +    if (ret < 0) {
> +        error_report("Another balloon device already registered");

We don't know why it failed at this point. I think
error report should be triggered by qemu_add_balloon_handler,
and this function would just cleanup and exit.


> +        virtio_cleanup(&s->vdev);
> +        return NULL;
> +    }
> +
>      s->ivq = virtio_add_queue(&s->vdev, 128, virtio_balloon_handle_output);
>      s->dvq = virtio_add_queue(&s->vdev, 128, virtio_balloon_handle_output);
>      s->svq = virtio_add_queue(&s->vdev, 128, virtio_balloon_receive_stats);
>  
>      reset_stats(s);
> -    qemu_add_balloon_handler(virtio_balloon_to_target, virtio_balloon_stat, s);
>  
>      register_savevm(dev, "virtio-balloon", -1, 1,
>                      virtio_balloon_save, virtio_balloon_load, s);
> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
> index d685243..ca5f125 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;
>  }
> -- 
> 1.7.6
>