Re: [PATCH 3/3] vdpa net: follow VirtIO initialization properly at cvq isolation probing

[Jason Wang]

On Sat, Sep 16, 2023 at 1:03 AM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> This patch solves a few issues.  The most obvious is that the feature
> set was done previous to ACKNOWLEDGE | DRIVER status bit set.  Current
> vdpa devices are permissive with this, but it is better to follow the
> standard.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  net/vhost-vdpa.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 51d8144070..4b30325977 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -1270,8 +1270,7 @@ static int vhost_vdpa_probe_cvq_isolation(int 
> device_fd, uint64_t features,
>      uint64_t backend_features;
>      int64_t cvq_group;
>      uint8_t status = VIRTIO_CONFIG_S_ACKNOWLEDGE |
> -                     VIRTIO_CONFIG_S_DRIVER |
> -                     VIRTIO_CONFIG_S_FEATURES_OK;
> +                     VIRTIO_CONFIG_S_DRIVER;
>      int r;
>
>      ERRP_GUARD();
> @@ -1286,15 +1285,22 @@ static int vhost_vdpa_probe_cvq_isolation(int 
> device_fd, uint64_t features,
>          return 0;
>      }
>
> +    r = ioctl(device_fd, VHOST_VDPA_SET_STATUS, &status);
> +    if (unlikely(r)) {
> +        error_setg_errno(errp, -r, "Cannot set device status");
> +        goto out;
> +    }
> +
>      r = ioctl(device_fd, VHOST_SET_FEATURES, &features);
>      if (unlikely(r)) {
> -        error_setg_errno(errp, errno, "Cannot set features");
> +        error_setg_errno(errp, -r, "Cannot set features");
>          goto out;
>      }
>

Spec requires a re-read ?

"
Re-read device status to ensure the FEATURES_OK bit is still set:
otherwise, the device does not support our subset of features and the
device is unusable.
"

Thanks

> +    status |= VIRTIO_CONFIG_S_FEATURES_OK;
>      r = ioctl(device_fd, VHOST_VDPA_SET_STATUS, &status);
>      if (unlikely(r)) {
> -        error_setg_errno(errp, -r, "Cannot set status");
> +        error_setg_errno(errp, -r, "Cannot set device status");
>          goto out;
>      }
>
> --
> 2.39.3
>