[PATCH v2 net] ixgbe: allow to increase MTU to some extent with XDP enabled

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

I encountered one case where I cannot increase the MTU size directly
from 1500 to 2000 with XDP enabled if the server is equipped with
IXGBE card, which happened on thousands of servers in production
environment.

This patch follows the behavior of changing MTU as i40e/ice does.

Referrences:
commit 23b44513c3e6f ("ice: allow 3k MTU for XDP")
commit 0c8493d90b6bb ("i40e: add XDP support for pass and drop actions")

Link: https://lore.kernel.org/lkml/20230121085521.9566-1-kerneljasonxing@gmail.com/
Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
v2:
1) change the commit message.
2) modify the logic when changing MTU size suggested by Maciej and Alexander.
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 25 ++++++++++++-------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index ab8370c413f3..2c1b6eb60436 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -6777,6 +6777,18 @@ static void ixgbe_free_all_rx_resources(struct ixgbe_adapter *adapter)
 			ixgbe_free_rx_resources(adapter->rx_ring[i]);
 }
 
+/**
+ * ixgbe_max_xdp_frame_size - returns the maximum allowed frame size for XDP
+ * @adapter - device handle, pointer to adapter
+ */
+static int ixgbe_max_xdp_frame_size(struct ixgbe_adapter *adapter)
+{
+	if (PAGE_SIZE >= 8192 || adapter->flags2 & IXGBE_FLAG2_RX_LEGACY)
+		return IXGBE_RXBUFFER_2K;
+	else
+		return IXGBE_RXBUFFER_3K;
+}
+
 /**
  * ixgbe_change_mtu - Change the Maximum Transfer Unit
  * @netdev: network interface device structure
@@ -6788,18 +6800,13 @@ static int ixgbe_change_mtu(struct net_device *netdev, int new_mtu)
 {
 	struct ixgbe_adapter *adapter = netdev_priv(netdev);
 
-	if (adapter->xdp_prog) {
+	if (ixgbe_enabled_xdp_adapter(adapter)) {
 		int new_frame_size = new_mtu + ETH_HLEN + ETH_FCS_LEN +
 				     VLAN_HLEN;
-		int i;
-
-		for (i = 0; i < adapter->num_rx_queues; i++) {
-			struct ixgbe_ring *ring = adapter->rx_ring[i];
 
-			if (new_frame_size > ixgbe_rx_bufsz(ring)) {
-				e_warn(probe, "Requested MTU size is not supported with XDP\n");
-				return -EINVAL;
-			}
+		if (new_frame_size > ixgbe_max_xdp_frame_size(adapter)) {
+			e_warn(probe, "Requested MTU size is not supported with XDP\n");
+			return -EINVAL;
 		}
 	}
 
-- 
2.37.3