net/mlx5e: Validate MTU when building non-linear legacy RQ fragments info

mlx5e_build_rq_frags_info() assumes that MTU is not bigger than
PAGE_SIZE * MLX5E_MAX_RX_FRAGS, which is 16K for 4K pages. Currently,
the firmware limits MTU to 10K, so the assumption doesn't lead to a bug.

This commits adds an additional driver check for reliability, since the
firmware boundary might be changed.

The calculation is taken to a separate function with a comment
explaining it. It's a preparation for the following patches that
introcuce XDP multi buffer support.

Signed-off-by: Maxim Mikityanskiy <maximmi@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/params.c b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
index 0bd8698..0f258e7 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -392,16 +392,23 @@ void mlx5e_build_create_cq_param(struct mlx5e_create_cq_param *ccp, struct mlx5e
        };
 }
 
+static int mlx5e_max_nonlinear_mtu(int frag_size)
+{
+       /* Optimization for small packets: the last fragment is bigger than the others. */
+       return (MLX5E_MAX_RX_FRAGS - 1) * frag_size + PAGE_SIZE;
+}
+
 #define DEFAULT_FRAG_SIZE (2048)
 
-static void mlx5e_build_rq_frags_info(struct mlx5_core_dev *mdev,
-                                     struct mlx5e_params *params,
-                                     struct mlx5e_xsk_param *xsk,
-                                     struct mlx5e_rq_frags_info *info)
+static int mlx5e_build_rq_frags_info(struct mlx5_core_dev *mdev,
+                                    struct mlx5e_params *params,
+                                    struct mlx5e_xsk_param *xsk,
+                                    struct mlx5e_rq_frags_info *info)
 {
        u32 byte_count = MLX5E_SW2HW_MTU(params, params->sw_mtu);
        int frag_size_max = DEFAULT_FRAG_SIZE;
        u32 buf_size = 0;
+       int max_mtu;
        int i;
 
        if (mlx5_fpga_is_ipsec_device(mdev))
@@ -420,10 +427,18 @@ static void mlx5e_build_rq_frags_info(struct mlx5_core_dev *mdev,
                goto out;
        }
 
-       if (byte_count > PAGE_SIZE +
-           (MLX5E_MAX_RX_FRAGS - 1) * frag_size_max)
+       max_mtu = mlx5e_max_nonlinear_mtu(frag_size_max);
+       if (byte_count > max_mtu) {
                frag_size_max = PAGE_SIZE;
 
+               max_mtu = mlx5e_max_nonlinear_mtu(frag_size_max);
+               if (byte_count > max_mtu) {
+                       mlx5_core_err(mdev, "MTU %u is too big for non-linear legacy RQ (max %d)\n",
+                                     params->sw_mtu, max_mtu);
+                       return -EINVAL;
+               }
+       }
+
        i = 0;
        while (buf_size < byte_count) {
                int frag_size = byte_count - buf_size;
@@ -444,6 +459,8 @@ static void mlx5e_build_rq_frags_info(struct mlx5_core_dev *mdev,
 out:
        info->wqe_bulk = max_t(u8, info->wqe_bulk, 8);
        info->log_num_frags = order_base_2(info->num_frags);
+
+       return 0;
 }
 
 static u8 mlx5e_get_rqwq_log_stride(u8 wq_type, int ndsegs)
@@ -540,6 +557,7 @@ int mlx5e_build_rq_param(struct mlx5_core_dev *mdev,
        void *rqc = param->rqc;
        void *wq = MLX5_ADDR_OF(rqc, rqc, wq);
        int ndsegs = 1;
+       int err;
 
        switch (params->rq_wq_type) {
        case MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ: {
@@ -579,7 +597,9 @@ int mlx5e_build_rq_param(struct mlx5_core_dev *mdev,
        }
        default: /* MLX5_WQ_TYPE_CYCLIC */
                MLX5_SET(wq, wq, log_wq_sz, params->log_rq_mtu_frames);
-               mlx5e_build_rq_frags_info(mdev, params, xsk, &param->frags_info);
+               err = mlx5e_build_rq_frags_info(mdev, params, xsk, &param->frags_info);
+               if (err)
+                       return err;
                ndsegs = param->frags_info.num_frags;
        }