[RFC PATCH 2/9] virtio_net: set up xdp for multi buffer packets

[Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>]

When the xdp program sets xdp.frags, which means it can process
multi-buffer packets, so we continue to open xdp support when
features such as GRO_HW are negotiated.

Signed-off-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
Reviewed-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/net/virtio_net.c | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c5046d21b281..8f7d207d58d6 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3080,14 +3080,21 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 	u16 xdp_qp = 0, curr_qp;
 	int i, err;
 
-	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)
-	    && (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
-	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
-	        virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
-		virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO) ||
-		virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM))) {
-		NL_SET_ERR_MSG_MOD(extack, "Can't set XDP while host is implementing GRO_HW/CSUM, disable GRO_HW/CSUM first");
-		return -EOPNOTSUPP;
+	if (!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
+		if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_CSUM)) {
+			NL_SET_ERR_MSG_MOD(extack, "Can't set XDP without frags while guest is implementing GUEST_CSUM");
+			return -EOPNOTSUPP;
+		}
+
+		if (prog && !prog->aux->xdp_has_frags) {
+			if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
+			    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6) ||
+			    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ECN) ||
+			    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_UFO)) {
+				NL_SET_ERR_MSG_MOD(extack, "Can't set XDP without frags while guest is implementing GUEST_GRO_HW");
+				return -EOPNOTSUPP;
+			}
+		}
 	}
 
 	if (vi->mergeable_rx_bufs && !vi->any_header_sg) {
@@ -3095,8 +3102,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
 		return -EINVAL;
 	}
 
-	if (dev->mtu > max_sz) {
-		NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP");
+	if (prog && !prog->aux->xdp_has_frags && dev->mtu > max_sz) {
+		NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP without frags");
 		netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz);
 		return -EINVAL;
 	}
@@ -3218,9 +3225,6 @@ static int virtnet_set_features(struct net_device *dev,
 	int err;
 
 	if ((dev->features ^ features) & NETIF_F_GRO_HW) {
-		if (vi->xdp_enabled)
-			return -EBUSY;
-
 		if (features & NETIF_F_GRO_HW)
 			offloads = vi->guest_offloads_capable;
 		else
-- 
2.19.1.6.gb485710b