* [PATCH] mlx5: avoid integer overflow warning for large page size
@ 2023-06-22 10:15 Arnd Bergmann
2023-06-22 11:23 ` Maxim Mikityanskiy
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2023-06-22 10:15 UTC (permalink / raw)
To: Saeed Mahameed, Leon Romanovsky, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni
Cc: Arnd Bergmann, Nathan Chancellor, Nick Desaulniers, Tom Rix,
Tariq Toukan, Maxim Mikityanskiy, Adham Faris, netdev,
linux-rdma, linux-kernel, llvm
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) {
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mlx5: avoid integer overflow warning for large page size
2023-06-22 10:15 [PATCH] mlx5: avoid integer overflow warning for large page size Arnd Bergmann
@ 2023-06-22 11:23 ` Maxim Mikityanskiy
2023-06-22 11:28 ` Arnd Bergmann
0 siblings, 1 reply; 3+ messages in thread
From: Maxim Mikityanskiy @ 2023-06-22 11:23 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Saeed Mahameed, Leon Romanovsky, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Arnd Bergmann, Nathan Chancellor,
Nick Desaulniers, Tom Rix, Tariq Toukan, Adham Faris, netdev,
linux-rdma, linux-kernel, llvm
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
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mlx5: avoid integer overflow warning for large page size
2023-06-22 11:23 ` Maxim Mikityanskiy
@ 2023-06-22 11:28 ` Arnd Bergmann
0 siblings, 0 replies; 3+ messages in thread
From: Arnd Bergmann @ 2023-06-22 11:28 UTC (permalink / raw)
To: Maxim Mikityanskiy, Arnd Bergmann
Cc: Saeed Mahameed, Leon Romanovsky, David S . Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Nathan Chancellor, Nick Desaulniers,
Tom Rix, Tariq Toukan, Adham Faris, Netdev, linux-rdma,
linux-kernel, llvm
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-06-22 10:15 [PATCH] mlx5: avoid integer overflow warning for large page size Arnd Bergmann
2023-06-22 11:23 ` Maxim Mikityanskiy
2023-06-22 11:28 ` Arnd Bergmann
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