Re: [PATCH] vhost-vdpa: check vhost_vdpa_set_vring_ready() return value

[Jason Wang]

On Wed, Feb 7, 2024 at 5:27 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> vhost_vdpa_set_vring_ready() could already fail, but if Linux's
> patch [1] will be merged, it may fail with more chance if
> userspace does not activate virtqueues before DRIVER_OK when
> VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK is not negotiated.

I wonder what happens if we just leave it as is.

VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK: We do know enabling could be
done after driver_ok.
Without VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK: We don't know whether
enabling could be done after driver_ok or not.

Thanks

>
> So better check its return value anyway.
>
> [1] 
> https://lore.kernel.org/virtualization/20240206145154.118044-1-sgarzare@redhat.com/T/#u
>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
> Note: This patch conflicts with [2], but the resolution is simple,
> so for now I sent a patch for the current master, but I'll rebase
> this patch if we merge the other one first.
>
> [2] 
> https://lore.kernel.org/qemu-devel/20240202132521.32714-1-kwolf@redhat.com/
> ---
>  hw/virtio/vdpa-dev.c |  8 +++++++-
>  net/vhost-vdpa.c     | 15 ++++++++++++---
>  2 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c
> index eb9ecea83b..d57cd76c18 100644
> --- a/hw/virtio/vdpa-dev.c
> +++ b/hw/virtio/vdpa-dev.c
> @@ -259,7 +259,11 @@ static int vhost_vdpa_device_start(VirtIODevice *vdev, 
> Error **errp)
>          goto err_guest_notifiers;
>      }
>      for (i = 0; i < s->dev.nvqs; ++i) {
> -        vhost_vdpa_set_vring_ready(&s->vdpa, i);
> +        ret = vhost_vdpa_set_vring_ready(&s->vdpa, i);
> +        if (ret < 0) {
> +            error_setg_errno(errp, -ret, "Error starting vring %d", i);
> +            goto err_dev_stop;
> +        }
>      }
>      s->started = true;
>
> @@ -274,6 +278,8 @@ static int vhost_vdpa_device_start(VirtIODevice *vdev, 
> Error **errp)
>
>      return ret;
>
> +err_dev_stop:
> +    vhost_dev_stop(&s->dev, vdev, false);
>  err_guest_notifiers:
>      k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
>  err_host_notifiers:
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 3726ee5d67..e3d8036479 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -381,7 +381,10 @@ static int vhost_vdpa_net_data_load(NetClientState *nc)
>      }
>
>      for (int i = 0; i < v->dev->nvqs; ++i) {
> -        vhost_vdpa_set_vring_ready(v, i + v->dev->vq_index);
> +        int ret = vhost_vdpa_set_vring_ready(v, i + v->dev->vq_index);
> +        if (ret < 0) {
> +            return ret;
> +        }
>      }
>      return 0;
>  }
> @@ -1213,7 +1216,10 @@ static int vhost_vdpa_net_cvq_load(NetClientState *nc)
>
>      assert(nc->info->type == NET_CLIENT_DRIVER_VHOST_VDPA);
>
> -    vhost_vdpa_set_vring_ready(v, v->dev->vq_index);
> +    r = vhost_vdpa_set_vring_ready(v, v->dev->vq_index);
> +    if (unlikely(r < 0)) {
> +        return r;
> +    }
>
>      if (v->shadow_vqs_enabled) {
>          n = VIRTIO_NET(v->dev->vdev);
> @@ -1252,7 +1258,10 @@ static int vhost_vdpa_net_cvq_load(NetClientState *nc)
>      }
>
>      for (int i = 0; i < v->dev->vq_index; ++i) {
> -        vhost_vdpa_set_vring_ready(v, i);
> +        r = vhost_vdpa_set_vring_ready(v, i);
> +        if (unlikely(r < 0)) {
> +            return r;
> +        }
>      }
>
>      return 0;
> --
> 2.43.0
>