On Thu, 22 Jun 2023 at 12:15:02 +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> Build testing with 'make LLVM=1 W=1' shows a warning about a
> condition that is always true on configurations with 64KB
> pages:
>
> drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c:32:22: error: result of comparison of constant 65536 with expression of type 'u16' (aka 'unsigned short') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>
> Change the condition in a way that lets clang know this
> is intentional.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
> index 36826b5824847..b9f62e531bd4c 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c
> @@ -29,7 +29,8 @@ bool mlx5e_validate_xsk_param(struct mlx5e_params *params,
> struct mlx5_core_dev *mdev)
> {
> /* AF_XDP doesn't support frames larger than PAGE_SIZE. */
> - if (xsk->chunk_size > PAGE_SIZE || xsk->chunk_size < MLX5E_MIN_XSK_CHUNK_SIZE) {
> + if ((PAGE_SIZE < U16_MAX && xsk->chunk_size > PAGE_SIZE)
> + || xsk->chunk_size < MLX5E_MIN_XSK_CHUNK_SIZE) {
I recall you already sent a fix to silence this warning before:
https://lore.kernel.org/netdev/20211015152056.2434853-1-arnd@xxxxxxxxxx/
I prefer that old one, as it's more future-proof to cast to size_t here
in place (chunk_size won't be bigger than size_t for sure). With your
new patch, if chunk_size is ever changed from u16 to u32, it's likely
that this place will be unnoticed, and a bug will be introduced.
> mlx5_core_err(mdev, "XSK chunk size %u out of bounds [%u, %lu]\n", xsk->chunk_size,
> MLX5E_MIN_XSK_CHUNK_SIZE, PAGE_SIZE);
> return false;
> --
> 2.39.2
>
