Re: [PULL 07/15] vhost: check queue state in the vhost_dev_set_log routine

[Raphael Norwitz]

Hi MST - I think you picked an earlier version of the change with a
bug. See my comment bellow:

On Fri, Sep 18, 2020 at 11:11 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> From: Dima Stepanov <dimastep@yandex-team.ru>
>
> If the vhost-user-blk daemon provides only one virtqueue, but device was
> added with several queues, then QEMU will send more VHOST-USER command
> than expected by daemon side. The vhost_virtqueue_start() routine
> handles such case by checking the return value from the
> virtio_queue_get_desc_addr() function call. Add the same check to the
> vhost_dev_set_log() routine.
>
> Signed-off-by: Dima Stepanov <dimastep@yandex-team.ru>
> Message-Id: 
> <2da64fc45789094b6bd6f1c283cac9e47eeeb786.1598865610.git.dimastep@yandex-team.ru>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  hw/virtio/vhost.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 1b2d735b54..abe0fe3e67 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -835,12 +835,24 @@ out:
>  static int vhost_dev_set_log(struct vhost_dev *dev, bool enable_log)
>  {
>      int r, i, idx;
> +    hwaddr addr;
> +
>      r = vhost_dev_set_features(dev, enable_log);
>      if (r < 0) {
>          goto err_features;
>      }
>      for (i = 0; i < dev->nvqs; ++i) {
>          idx = dev->vhost_ops->vhost_get_vq_index(dev, dev->vq_index + i);
> +        addr = virtio_queue_get_desc_addr(dev->vdev, idx);
> +        if (!addr) {
> +            /*
> +             * The queue might not be ready for start. If this
> +             * is the case there is no reason to continue the process.
> +             * The similar logic is used by the vhost_virtqueue_start()
> +             * routine.
> +             */

This should be "continue" not "break" right?

ref: https://lore.kernel.org/qemu-devel/20200901083616.GA18268@dimastep-nix/

> +            break;
> +        }
>          r = vhost_virtqueue_set_addr(dev, dev->vqs + i, idx,
>                                       enable_log);
>          if (r < 0) {
> --
> MST
>
>