Re: [PATCH 1/3] vhost-user: do not send RESET_OWNER on device reset

[Raphael Norwitz]

> On Sep 27, 2023, at 3:27 PM, Stefan Hajnoczi <stefanha@redhat.com> wrote:
> 
> The VHOST_USER_RESET_OWNER message is deprecated in the spec:
> 
>   This is no longer used. Used to be sent to request disabling all
>   rings, but some back-ends interpreted it to also discard connection
>   state (this interpretation would lead to bugs).  It is recommended
>   that back-ends either ignore this message, or use it to disable all
>   rings.
> 
> The only caller of vhost_user_reset_device() is vhost_user_scsi_reset().
> It checks that F_RESET_DEVICE was negotiated before calling it:
> 
>  static void vhost_user_scsi_reset(VirtIODevice *vdev)
>  {
>      VHostSCSICommon *vsc = VHOST_SCSI_COMMON(vdev);
>      struct vhost_dev *dev = &vsc->dev;
> 
>      /*
>       * Historically, reset was not implemented so only reset devices
>       * that are expecting it.
>       */
>      if (!virtio_has_feature(dev->protocol_features,
>                              VHOST_USER_PROTOCOL_F_RESET_DEVICE)) {
>          return;
>      }
> 
>      if (dev->vhost_ops->vhost_reset_device) {
>          dev->vhost_ops->vhost_reset_device(dev);
>      }
>  }
> 
> Therefore VHOST_USER_RESET_OWNER is actually never sent by
> vhost_user_reset_device(). Remove the dead code. This effectively moves
> the vhost-user protocol specific code from vhost-user-scsi.c into
> vhost-user.c where it belongs.

Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com>

> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> hw/scsi/vhost-user-scsi.c |  9 ---------
> hw/virtio/vhost-user.c    | 13 +++++++++----
> 2 files changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
> index ee99b19e7a..8582b2e8ab 100644
> --- a/hw/scsi/vhost-user-scsi.c
> +++ b/hw/scsi/vhost-user-scsi.c
> @@ -71,15 +71,6 @@ static void vhost_user_scsi_reset(VirtIODevice *vdev)
>     VHostSCSICommon *vsc = VHOST_SCSI_COMMON(vdev);
>     struct vhost_dev *dev = &vsc->dev;
> 
> -    /*
> -     * Historically, reset was not implemented so only reset devices
> -     * that are expecting it.
> -     */
> -    if (!virtio_has_feature(dev->protocol_features,
> -                            VHOST_USER_PROTOCOL_F_RESET_DEVICE)) {
> -        return;
> -    }
> -
>     if (dev->vhost_ops->vhost_reset_device) {
>         dev->vhost_ops->vhost_reset_device(dev);
>     }
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index 8dcf049d42..7bed9ad7d5 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -1492,12 +1492,17 @@ static int vhost_user_reset_device(struct vhost_dev 
> *dev)
> {
>     VhostUserMsg msg = {
>         .hdr.flags = VHOST_USER_VERSION,
> +        .hdr.request = VHOST_USER_RESET_DEVICE,
>     };
> 
> -    msg.hdr.request = virtio_has_feature(dev->protocol_features,
> -                                         VHOST_USER_PROTOCOL_F_RESET_DEVICE)
> -        ? VHOST_USER_RESET_DEVICE
> -        : VHOST_USER_RESET_OWNER;
> +    /*
> +     * Historically, reset was not implemented so only reset devices
> +     * that are expecting it.
> +     */
> +    if (!virtio_has_feature(dev->protocol_features,
> +                            VHOST_USER_PROTOCOL_F_RESET_DEVICE)) {
> +        return -ENOSYS;
> +    }
> 
>     return vhost_user_write(dev, &msg, NULL, 0);
> }
> -- 
> 2.41.0
>