[PATCH net-next] ibmvnic: Enable TSO support

[Thomas Falcon <tlfalcon@linux.vnet.ibm.com>]

Enable TSO in the ibmvnic driver. Scatter-gather is also enabled,
though there currently is no support for scatter-gather in
vNIC-compatible hardware, resulting in forced linearization
of all fragmented SKB's. Though not ideal, given the throughput
improvement gained by enabling TSO, it has been decided
that this is an acceptable tradeoff.

The feature is also enabled by a module parameter.
This parameter is necessary because TSO can not easily be
enabled or disabled in firmware without reinitializing the driver.

CC: Nathan Fontenot <nfont@linux.vnet.ibm.com>
CC: John Allen <jallen@linux.vnet.ibm.com>
Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 39 +++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index abe2b6e..64e8d50 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -81,6 +81,11 @@
 static const char ibmvnic_driver_name[] = "ibmvnic";
 static const char ibmvnic_driver_string[] = "IBM System i/p Virtual NIC Driver";
 
+static int large_send_offload;
+module_param(large_send_offload, bool, 0644);
+MODULE_PARM_DESC(large_send_offload,
+		 "Determines whether large send offload is enabled");
+
 MODULE_AUTHOR("Santiago Leon <santi_leon@yahoo.com>");
 MODULE_DESCRIPTION("IBM System i/p Virtual NIC Driver");
 MODULE_LICENSE("GPL");
@@ -1025,6 +1030,17 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 		goto out;
 	}
 
+	/* All scatter-gather SKB's will be linearized for the time being, but
+	 * scatter-gather is only enabled if the user wishes to use TSO.
+	 */
+	if (skb_shinfo(skb)->nr_frags && __skb_linearize(skb)) {
+		dev_kfree_skb_any(skb);
+		tx_send_failed++;
+		tx_dropped++;
+		ret = NETDEV_TX_OK;
+		goto out;
+	}
+
 	tx_pool = &adapter->tx_pool[queue_num];
 	tx_scrq = adapter->tx_scrq[queue_num];
 	txq = netdev_get_tx_queue(netdev, skb_get_queue_mapping(skb));
@@ -1082,6 +1098,11 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 		tx_crq.v1.flags1 |= IBMVNIC_TX_CHKSUM_OFFLOAD;
 		hdrs += 2;
 	}
+	if (skb_is_gso(skb)) {
+		tx_crq.v1.flags1 |= IBMVNIC_TX_LSO;
+		tx_crq.v1.mss = cpu_to_be16(skb_shinfo(skb)->gso_size);
+		hdrs += 2;
+	}
 	/* determine if l2/3/4 headers are sent to firmware */
 	if ((*hdrs >> 7) & 1 &&
 	    (skb->protocol == htons(ETH_P_IP) ||
@@ -2629,10 +2650,10 @@ static void handle_query_ip_offload_rsp(struct ibmvnic_adapter *adapter)
 	adapter->ip_offload_ctrl.udp_ipv4_chksum = buf->udp_ipv4_chksum;
 	adapter->ip_offload_ctrl.tcp_ipv6_chksum = buf->tcp_ipv6_chksum;
 	adapter->ip_offload_ctrl.udp_ipv6_chksum = buf->udp_ipv6_chksum;
+	adapter->ip_offload_ctrl.large_tx_ipv4 = buf->large_tx_ipv4;
+	adapter->ip_offload_ctrl.large_tx_ipv6 = buf->large_tx_ipv6;
 
-	/* large_tx/rx disabled for now, additional features needed */
-	adapter->ip_offload_ctrl.large_tx_ipv4 = 0;
-	adapter->ip_offload_ctrl.large_tx_ipv6 = 0;
+	/* large_rx disabled for now, additional features needed */
 	adapter->ip_offload_ctrl.large_rx_ipv4 = 0;
 	adapter->ip_offload_ctrl.large_rx_ipv6 = 0;
 
@@ -2648,6 +2669,18 @@ static void handle_query_ip_offload_rsp(struct ibmvnic_adapter *adapter)
 	    (NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM)))
 		adapter->netdev->features |= NETIF_F_RXCSUM;
 
+	if (large_send_offload) {
+		/* Scatter-gather is not currently supported by firmware.
+		 * It will only be enabled to support TSO operations.
+		 */
+		adapter->netdev->features = NETIF_F_SG;
+
+		if (buf->large_tx_ipv4)
+			adapter->netdev->features |= NETIF_F_TSO;
+		if (buf->large_tx_ipv6)
+			adapter->netdev->features |= NETIF_F_TSO6;
+	}
+
 	memset(&crq, 0, sizeof(crq));
 	crq.control_ip_offload.first = IBMVNIC_CRQ_CMD;
 	crq.control_ip_offload.cmd = CONTROL_IP_OFFLOAD;
-- 
1.8.3.1