net/mlx5e: Fix hw mtu initializing at XDP SQ allocation

Adham Faris · Saeed Mahameed · commit 1e267ab88dc4 · 2022-12-28T11:38:51.000-08:00
Current xdp xmit functions logic (mlx5e_xmit_xdp_frame_mpwqe or mlx5e_xmit_xdp_frame), validates xdp packet length by comparing it to hw mtu (configured at xdp sq allocation) before xmiting it. This check does not account for ethernet fcs length (calculated and filled by the nic). Hence, when we try sending packets with length > (hw-mtu - ethernet-fcs-size), the device port drops it and tx_errors_phy is incremented. Desired behavior is to catch these packets and drop them by the driver. Fix this behavior in XDP SQ allocation function (mlx5e_alloc_xdpsq) by subtracting ethernet FCS header size (4 Bytes) from current hw mtu value, since ethernet FCS is calculated and written to ethernet frames by the nic. Fixes: d8bec2b ("net/mlx5e: Support bpf_xdp_adjust_head()") Signed-off-by: Adham Faris <afaris@nvidia.com> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -1305,7 +1305,7 @@ static int mlx5e_alloc_xdpsq(struct mlx5e_channel *c,
 	sq->channel   = c;
 	sq->uar_map   = mdev->mlx5e_res.hw_objs.bfreg.map;
 	sq->min_inline_mode = params->tx_min_inline_mode;
-	sq->hw_mtu    = MLX5E_SW2HW_MTU(params, params->sw_mtu);
+	sq->hw_mtu    = MLX5E_SW2HW_MTU(params, params->sw_mtu) - ETH_FCS_LEN;
 	sq->xsk_pool  = xsk_pool;
 
 	sq->stats = sq->xsk_pool ?
