Re: [Qemu-devel] [PATCH for-2.5] virtio-9p-device: add minimal unrealize handler

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

On Tue, Dec 08, 2015 at 04:54:57PM +0100, Greg Kurz wrote:
> Since commit 4652f1640e029e1f2433fa77ba6af285 "virtio-9p: add savevm handlers",
> if the user hot-unplugs a quiescent 9p device and live migrates, the source
> QEMU crashes before migration completetion... This happens because virtio-9p
> devices have a realize handler which calls virtio_init() and register_savevm().
> Both calls store pointers to the device internals, that get dereferenced during
> migration even if the device got unplugged.
> 
> This patch simply adds an unrealize handler to perform minimal cleanup and
> avoid the crash. Hot unplug of non-quiescent 9p devices is still not supported
> in QEMU, and not supported by linux guests either.
> 
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  hw/9pfs/virtio-9p-device.c |   12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
> index 944b5f5e9fcc..b42d3b30a027 100644
> --- a/hw/9pfs/virtio-9p-device.c
> +++ b/hw/9pfs/virtio-9p-device.c
> @@ -145,6 +145,17 @@ out:
>      v9fs_path_free(&path);
>  }
>  
> +static void virtio_9p_device_unrealize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    V9fsState *s = VIRTIO_9P(dev);
> +
> +    virtio_cleanup(vdev);
> +    unregister_savevm(dev, "virtio-9p", s);
> +    g_free(s->ctx.fs_root);
> +    g_free(s->tag);
> +}
> +
>  /* virtio-9p device */
>  
>  static Property virtio_9p_properties[] = {
> @@ -161,6 +172,7 @@ static void virtio_9p_class_init(ObjectClass *klass, void *data)
>      dc->props = virtio_9p_properties;
>      set_bit(DEVICE_CATEGORY_STORAGE, dc->categories);
>      vdc->realize = virtio_9p_device_realize;
> +    vdc->unrealize = virtio_9p_device_unrealize;
>      vdc->get_features = virtio_9p_get_features;
>      vdc->get_config = virtio_9p_get_config;
>  }