Merge branch 'ibmveth-gso-fix'

David Wilder says:

====================
ibmveth gso fix

The ibmveth driver is a virtual Ethernet driver used on IBM pSeries systems.
Gso packets can be sent between LPARS (virtual hosts) without segmentation,
by flagging gso packets using one of two methods depending on the firmware
version. Some gso packet were not correctly identified by the receiver.
This patch-set corrects this issue.

V2:
- Added fix tags.
- Byteswap the constant at compilation time.
- Updated the commit message to clarify what frame validation is performed
  by the hypervisor.
====================

Link: https://lore.kernel.org/r/20201013232014.26044-1-dwilder@us.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

drivers/net/ethernet/ibm/ibmveth.c

@@ -1349,6 +1349,7 @@ static int ibmveth_poll(struct napi_struct *napi, int budget)
 			int offset = ibmveth_rxq_frame_offset(adapter);
 			int csum_good = ibmveth_rxq_csum_good(adapter);
 			int lrg_pkt = ibmveth_rxq_large_packet(adapter);
+			__sum16 iph_check = 0;
 
 			skb = ibmveth_rxq_get_buffer(adapter);
 
@@ -1385,16 +1386,26 @@ static int ibmveth_poll(struct napi_struct *napi, int budget)
 			skb_put(skb, length);
 			skb->protocol = eth_type_trans(skb, netdev);
 
-			if (csum_good) {
-				skb->ip_summed = CHECKSUM_UNNECESSARY;
-				ibmveth_rx_csum_helper(skb, adapter);
+			/* PHYP without PLSO support places a -1 in the ip
+			 * checksum for large send frames.
+			 */
+			if (skb->protocol == cpu_to_be16(ETH_P_IP)) {
+				struct iphdr *iph = (struct iphdr *)skb->data;
+
+				iph_check = iph->check;
 			}
 
-			if (length > netdev->mtu + ETH_HLEN) {
+			if ((length > netdev->mtu + ETH_HLEN) ||
+			    lrg_pkt || iph_check == 0xffff) {
 				ibmveth_rx_mss_helper(skb, mss, lrg_pkt);
 				adapter->rx_large_packets++;
 			}
 
+			if (csum_good) {
+				skb->ip_summed = CHECKSUM_UNNECESSARY;
+				ibmveth_rx_csum_helper(skb, adapter);
+			}
+
 			napi_gro_receive(napi, skb);	/* send it up */
 
 			netdev->stats.rx_packets++;