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Commit ae6b0710 authored by Maxim Mikityanskiy's avatar Maxim Mikityanskiy Committed by Greg Kroah-Hartman
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net/mlx5e: Fix the max MTU check in case of XDP 



[ Upstream commit d460c2718906252a2a69bc6f89b537071f792e6e ]

MLX5E_XDP_MAX_MTU was calculated incorrectly. It didn't account for
NET_IP_ALIGN and MLX5E_HW2SW_MTU, and it also misused MLX5_SKB_FRAG_SZ.
This commit fixes the calculations and adds a brief explanation for the
formula used.

Fixes: a26a5bdf ("net/mlx5e: Restrict the combination of large MTU and XDP")
Signed-off-by: default avatarMaxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: default avatarSaeed Mahameed <saeedm@mellanox.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b08774d3

drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c

+20 −0
Original line number Diff line number Diff line
@@ -33,6 +33,26 @@ 
#include <linux/bpf_trace.h>

#include "en/xdp.h"



int mlx5e_xdp_max_mtu(struct mlx5e_params *params)

{

	int hr = NET_IP_ALIGN + XDP_PACKET_HEADROOM;



	/* Let S := SKB_DATA_ALIGN(sizeof(struct skb_shared_info)).

	 * The condition checked in mlx5e_rx_is_linear_skb is:

	 *   SKB_DATA_ALIGN(sw_mtu + hard_mtu + hr) + S <= PAGE_SIZE         (1)

	 *   (Note that hw_mtu == sw_mtu + hard_mtu.)

	 * What is returned from this function is:

	 *   max_mtu = PAGE_SIZE - S - hr - hard_mtu                         (2)

	 * After assigning sw_mtu := max_mtu, the left side of (1) turns to

	 * SKB_DATA_ALIGN(PAGE_SIZE - S) + S, which is equal to PAGE_SIZE,

	 * because both PAGE_SIZE and S are already aligned. Any number greater

	 * than max_mtu would make the left side of (1) greater than PAGE_SIZE,

	 * so max_mtu is the maximum MTU allowed.

	 */



	return MLX5E_HW2SW_MTU(params, SKB_MAX_HEAD(hr));

}



static inline bool

mlx5e_xmit_xdp_buff(struct mlx5e_xdpsq *sq, struct mlx5e_dma_info *di,

		    struct xdp_buff *xdp)

drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h

+1 −2
Original line number Diff line number Diff line
@@ -34,12 +34,11 @@ 


#include "en.h"



#define MLX5E_XDP_MAX_MTU ((int)(PAGE_SIZE - \

				 MLX5_SKB_FRAG_SZ(XDP_PACKET_HEADROOM)))

#define MLX5E_XDP_MIN_INLINE (ETH_HLEN + VLAN_HLEN)

#define MLX5E_XDP_TX_DS_COUNT \

	((sizeof(struct mlx5e_tx_wqe) / MLX5_SEND_WQE_DS) + 1 /* SG DS */)



int mlx5e_xdp_max_mtu(struct mlx5e_params *params);

bool mlx5e_xdp_handle(struct mlx5e_rq *rq, struct mlx5e_dma_info *di,

		      void *va, u16 *rx_headroom, u32 *len);

bool mlx5e_poll_xdpsq_cq(struct mlx5e_cq *cq);

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

+3 −2
Original line number Diff line number Diff line
@@ -3761,7 +3761,7 @@ int mlx5e_change_mtu(struct net_device *netdev, int new_mtu, 
	if (params->xdp_prog &&

	    !mlx5e_rx_is_linear_skb(priv->mdev, &new_channels.params)) {

		netdev_err(netdev, "MTU(%d) > %d is not allowed while XDP enabled\n",

			   new_mtu, MLX5E_XDP_MAX_MTU);

			   new_mtu, mlx5e_xdp_max_mtu(params));

		err = -EINVAL;

		goto out;

	}
@@ -4227,7 +4227,8 @@ static int mlx5e_xdp_allowed(struct mlx5e_priv *priv, struct bpf_prog *prog) 


	if (!mlx5e_rx_is_linear_skb(priv->mdev, &new_channels.params)) {

		netdev_warn(netdev, "XDP is not allowed with MTU(%d) > %d\n",

			    new_channels.params.sw_mtu, MLX5E_XDP_MAX_MTU);

			    new_channels.params.sw_mtu,

			    mlx5e_xdp_max_mtu(&new_channels.params));

		return -EINVAL;

	}