On Thu, Apr 20, 2023 at 09:07:06AM -0400, Stefan Hajnoczi wrote:
> Setting the VIRTIO Device Status Field to 0 resets the device. The
> device's state is lost, including the vring configuration.
>
> vhost-user.c currently sends SET_STATUS 0 before GET_VRING_BASE. This
> risks confusion about the lifetime of the vhost-user state (e.g. vring
> last_avail_idx) across VIRTIO device reset.
>
> Eugenio Pérez <epere...@redhat.com> adjusted the order for vhost-vdpa.c
> in commit c3716f260bff ("vdpa: move vhost reset after get vring base")
> and in that commit description suggested doing the same for vhost-user
> in the future.
>
> Go ahead and adjust vhost-user.c now. I ran various online code searches
> to identify vhost-user backends implementing SET_STATUS. It seems only
> DPDK implements SET_STATUS and Yajun Wu <yaj...@nvidia.com> has
> confirmed that it is safe to make this change.
Fixes tag?
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Cc: Cindy Lu <l...@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> ---
> hw/virtio/vhost-user.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> index e5285df4ba..2d40b1b3e7 100644
> --- a/hw/virtio/vhost-user.c
> +++ b/hw/virtio/vhost-user.c
> @@ -2677,10 +2677,20 @@ static int vhost_user_dev_start(struct vhost_dev
> *dev, bool started)
> VIRTIO_CONFIG_S_DRIVER |
> VIRTIO_CONFIG_S_DRIVER_OK);
> } else {
> - return vhost_user_set_status(dev, 0);
> + return 0;
> }
> }
>
> +static void vhost_user_reset_status(struct vhost_dev *dev)
> +{
> + /* Set device status only for last queue pair */
> + if (dev->vq_index + dev->nvqs != dev->vq_index_end) {
> + return;
> + }
> +
> + vhost_user_set_status(dev, 0);
> +}
> +
> const VhostOps user_ops = {
> .backend_type = VHOST_BACKEND_TYPE_USER,
> .vhost_backend_init = vhost_user_backend_init,
> @@ -2716,4 +2726,5 @@ const VhostOps user_ops = {
> .vhost_get_inflight_fd = vhost_user_get_inflight_fd,
> .vhost_set_inflight_fd = vhost_user_set_inflight_fd,
> .vhost_dev_start = vhost_user_dev_start,
> + .vhost_reset_status = vhost_user_reset_status,
> };
> --
> 2.39.2
