[bug report] net/mlx5e: Add mlx5e HV VHCA stats agent

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Eran Ben Elisha,

The patch cef35af34d6d: "net/mlx5e: Add mlx5e HV VHCA stats agent"
from Aug 22, 2019, leads to the following static checker warning:

	drivers/net/ethernet/mellanox/mlx5/core/en/hv_vhca_stats.c:41 mlx5e_hv_vhca_fill_stats()
	warn: potential pointer math issue ('buf' is a u64 pointer)

drivers/net/ethernet/mellanox/mlx5/core/en/hv_vhca_stats.c
    33  static void mlx5e_hv_vhca_fill_stats(struct mlx5e_priv *priv, u64 *data,
                                                                      ^^^^^^^^^
data is a u64 pointer.

    34                                       int buf_len)
    35  {
    36          int ch, i = 0;
    37  
    38          for (ch = 0; ch < priv->max_nch; ch++) {
    39                  u64 *buf = data + i;
                        ^^^^^^^^

    40  
    41                  if (WARN_ON_ONCE(buf +
    42                                   sizeof(struct mlx5e_hv_vhca_per_ring_stats) >
                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This pointer math doesn't work.  I'm surprised the warning doesn't
trigger.

    43                                   data + buf_len))
    44                          return;
    45  
    46                  mlx5e_hv_vhca_fill_ring_stats(priv, ch,
    47                                                (struct mlx5e_hv_vhca_per_ring_stats *)buf);
                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If we made both "data" and "buf" void pointers then this would be
much easier and the casting could be removed.


    48                  i += sizeof(struct mlx5e_hv_vhca_per_ring_stats) / sizeof(u64);
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This math works, but it's so complicated and you have to verify that
mlx5e_hv_vhca_per_ring_stats % sizeof(u64) is zero.

    49          }
    50  }

regards,
dan carpenter