| Message ID | 20230622101525.3321642-1-arnd@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | mlx5: avoid integer overflow warning for large page size | expand |
On Thu, 22 Jun 2023 at 12:15:02 +0200, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@arndb.de> > > 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@arndb.de> > --- > 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@kernel.org/ 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 >
On Thu, Jun 22, 2023, at 13:23, Maxim Mikityanskiy wrote: > On Thu, 22 Jun 2023 at 12:15:02 +0200, Arnd Bergmann wrote: > > I recall you already sent a fix to silence this warning before: > > https://lore.kernel.org/netdev/20211015152056.2434853-1-arnd@kernel.org/ > > 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); Indeed, I don't know why I no longer had the old patch in my randconfig tree, I completely forgot about that. The old patch is also ok. Arnd
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) { 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;