drivers/net/virtio_net: Fixed padded vheader to use v1 with hash.

The header v1 provides additional info about RSS.
Added changes to computing proper header length.
In the next patches, the header may contain RSS hash info
for the hash population.

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
Link: https://lore.kernel.org/r/20220328175336.10802-2-andrew@daynix.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: AndrewAtDaynix

drivers/net/virtio_net.c

@@ -242,13 +242,13 @@ struct virtnet_info {
 };
 
 struct padded_vnet_hdr {
-	struct virtio_net_hdr_mrg_rxbuf hdr;
+	struct virtio_net_hdr_v1_hash hdr;
 	/*
 	 * hdr is in a separate sg buffer, and data sg buffer shares same page
 	 * with this header sg. This padding makes next sg 16 byte aligned
 	 * after the header.
 	 */
-	char padding[4];
+	char padding[12];
 };
 
 static bool is_xdp_frame(void *ptr)
@@ -396,7 +396,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 
 	hdr_len = vi->hdr_len;
 	if (vi->mergeable_rx_bufs)
-		hdr_padded_len = sizeof(*hdr);
+		hdr_padded_len = hdr_len;
 	else
 		hdr_padded_len = sizeof(struct padded_vnet_hdr);
 
@@ -1266,7 +1266,8 @@ static unsigned int get_mergeable_buf_len(struct receive_queue *rq,
 					  struct ewma_pkt_len *avg_pkt_len,
 					  unsigned int room)
 {
-	const size_t hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+	struct virtnet_info *vi = rq->vq->vdev->priv;
+	const size_t hdr_len = vi->hdr_len;
 	unsigned int len;
 
 	if (room)
@@ -2851,7 +2852,7 @@ static void virtnet_del_vqs(struct virtnet_info *vi)
  */
 static unsigned int mergeable_min_buf_len(struct virtnet_info *vi, struct virtqueue *vq)
 {
-	const unsigned int hdr_len = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+	const unsigned int hdr_len = vi->hdr_len;
 	unsigned int rq_size = virtqueue_get_vring_size(vq);
 	unsigned int packet_len = vi->big_packets ? IP_MAX_MTU : vi->dev->max_mtu;
 	unsigned int buf_len = hdr_len + ETH_HLEN + VLAN_HLEN + packet_len;