releases/5.0.11/net-mlx5e-fix-the-max-mtu-check-in-case-of-xdp.patch

   1 From foo@baz Tue 30 Apr 2019 09:51:57 AM CEST
   2 From: Maxim Mikityanskiy <maximmi@mellanox.com>
   3 Date: Mon, 8 Apr 2019 15:12:45 +0300
   4 Subject: net/mlx5e: Fix the max MTU check in case of XDP
   5
   6 From: Maxim Mikityanskiy <maximmi@mellanox.com>
   7
   8 [ Upstream commit d460c2718906252a2a69bc6f89b537071f792e6e ]
   9
  10 MLX5E_XDP_MAX_MTU was calculated incorrectly. It didn't account for
  11 NET_IP_ALIGN and MLX5E_HW2SW_MTU, and it also misused MLX5_SKB_FRAG_SZ.
  12 This commit fixes the calculations and adds a brief explanation for the
  13 formula used.
  14
  15 Fixes: a26a5bdf3ee2d ("net/mlx5e: Restrict the combination of large MTU and XDP")
  16 Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
  17 Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
  18 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  19 ---
  20  drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c  |   20 ++++++++++++++++++++
  21  drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h  |    3 +--
  22  drivers/net/ethernet/mellanox/mlx5/core/en_main.c |    5 +++--
  23  3 files changed, 24 insertions(+), 4 deletions(-)
  24
  25 --- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
  26 +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
  27 @@ -33,6 +33,26 @@
  28  #include <linux/bpf_trace.h>
  29  #include "en/xdp.h"
  30
  31 +int mlx5e_xdp_max_mtu(struct mlx5e_params *params)
  32 +{
  33 +       int hr = NET_IP_ALIGN + XDP_PACKET_HEADROOM;
  34 +
  35 +       /* Let S := SKB_DATA_ALIGN(sizeof(struct skb_shared_info)).
  36 +        * The condition checked in mlx5e_rx_is_linear_skb is:
  37 +        *   SKB_DATA_ALIGN(sw_mtu + hard_mtu + hr) + S <= PAGE_SIZE         (1)
  38 +        *   (Note that hw_mtu == sw_mtu + hard_mtu.)
  39 +        * What is returned from this function is:
  40 +        *   max_mtu = PAGE_SIZE - S - hr - hard_mtu                         (2)
  41 +        * After assigning sw_mtu := max_mtu, the left side of (1) turns to
  42 +        * SKB_DATA_ALIGN(PAGE_SIZE - S) + S, which is equal to PAGE_SIZE,
  43 +        * because both PAGE_SIZE and S are already aligned. Any number greater
  44 +        * than max_mtu would make the left side of (1) greater than PAGE_SIZE,
  45 +        * so max_mtu is the maximum MTU allowed.
  46 +        */
  47 +
  48 +       return MLX5E_HW2SW_MTU(params, SKB_MAX_HEAD(hr));
  49 +}
  50 +
  51  static inline bool
  52  mlx5e_xmit_xdp_buff(struct mlx5e_xdpsq *sq, struct mlx5e_dma_info *di,
  53                     struct xdp_buff *xdp)
  54 --- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
  55 +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.h
  56 @@ -34,13 +34,12 @@
  57
  58  #include "en.h"
  59
  60 -#define MLX5E_XDP_MAX_MTU ((int)(PAGE_SIZE - \
  61 -                                MLX5_SKB_FRAG_SZ(XDP_PACKET_HEADROOM)))
  62  #define MLX5E_XDP_MIN_INLINE (ETH_HLEN + VLAN_HLEN)
  63  #define MLX5E_XDP_TX_EMPTY_DS_COUNT \
  64         (sizeof(struct mlx5e_tx_wqe) / MLX5_SEND_WQE_DS)
  65  #define MLX5E_XDP_TX_DS_COUNT (MLX5E_XDP_TX_EMPTY_DS_COUNT + 1 /* SG DS */)
  66
  67 +int mlx5e_xdp_max_mtu(struct mlx5e_params *params);
  68  bool mlx5e_xdp_handle(struct mlx5e_rq *rq, struct mlx5e_dma_info *di,
  69                       void *va, u16 *rx_headroom, u32 *len);
  70  bool mlx5e_poll_xdpsq_cq(struct mlx5e_cq *cq, struct mlx5e_rq *rq);
  71 --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
  72 +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
  73 @@ -3816,7 +3816,7 @@ int mlx5e_change_mtu(struct net_device *
  74         if (params->xdp_prog &&
  75             !mlx5e_rx_is_linear_skb(priv->mdev, &new_channels.params)) {
  76                 netdev_err(netdev, "MTU(%d) > %d is not allowed while XDP enabled\n",
  77 -                          new_mtu, MLX5E_XDP_MAX_MTU);
  78 +                          new_mtu, mlx5e_xdp_max_mtu(params));
  79                 err = -EINVAL;
  80                 goto out;
  81         }
  82 @@ -4280,7 +4280,8 @@ static int mlx5e_xdp_allowed(struct mlx5
  83
  84         if (!mlx5e_rx_is_linear_skb(priv->mdev, &new_channels.params)) {
  85                 netdev_warn(netdev, "XDP is not allowed with MTU(%d) > %d\n",
  86 -                           new_channels.params.sw_mtu, MLX5E_XDP_MAX_MTU);
  87 +                           new_channels.params.sw_mtu,
  88 +                           mlx5e_xdp_max_mtu(&new_channels.params));
  89                 return -EINVAL;
  90         }
  91