Re: [PATCH] vhost_net: add NOTIFICATION_DATA and IN_ORDER feature bits to vdpa_feature_bits

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jan 02, 2024 at 04:44:32PM +0530, Srujana Challa wrote:
> Enables VIRTIO_F_NOTIFICATION_DATA and VIRTIO_F_IN_ORDER feature bits
> for vhost vdpa backend. Also adds code to consider all feature bits
> supported by vhost net client type for feature negotiation, so that
> vhost backend device supported features can be negotiated with guest.
> 
> Signed-off-by: Srujana Challa <schalla@marvell.com>
> ---
>  hw/net/vhost_net.c | 10 ++++++++++
>  net/vhost-vdpa.c   |  2 ++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index e8e1661646..65ae8bcece 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -117,6 +117,16 @@ static const int *vhost_net_get_feature_bits(struct vhost_net *net)
>  
>  uint64_t vhost_net_get_features(struct vhost_net *net, uint64_t features)
>  {
> +    const int *bit = vhost_net_get_feature_bits(net);
> +
> +    /*
> +     * Consider all feature bits for feature negotiation with vhost backend,
> +     * so that all backend device supported features can be negotiated.
> +     */
> +    while (*bit != VHOST_INVALID_FEATURE_BIT) {
> +        features |= (1ULL << *bit);
> +        bit++;
> +    }
>      return vhost_get_features(&net->dev, vhost_net_get_feature_bits(net),
>              features);
>  }

I don't think we should do this part. With vdpa QEMU is in control of
which features are exposed and that is intentional since features are
often tied to other behaviour.

> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 3726ee5d67..51334fcfe2 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -57,7 +57,9 @@ typedef struct VhostVDPAState {
>   */
>  const int vdpa_feature_bits[] = {
>      VIRTIO_F_ANY_LAYOUT,
> +    VIRTIO_F_IN_ORDER,
>      VIRTIO_F_IOMMU_PLATFORM,
> +    VIRTIO_F_NOTIFICATION_DATA,
>      VIRTIO_F_NOTIFY_ON_EMPTY,
>      VIRTIO_F_RING_PACKED,
>      VIRTIO_F_RING_RESET,
> -- 
> 2.25.1