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From: Arnd Bergmann <arnd@kernel.org>
To: Saeed Mahameed <saeedm@nvidia.com>,
	Leon Romanovsky <leon@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Tariq Toukan <tariqt@nvidia.com>,
	Maxim Mikityanskiy <maximmi@nvidia.com>,
	Aya Levin <ayal@nvidia.com>, Eran Ben Elisha <eranbe@nvidia.com>,
	Vladyslav Tarasiuk <vladyslavt@nvidia.com>,
	Jonathan Lemon <jonathan.lemon@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: [PATCH] mlx5: allow larger xsk chunk_size
Date: Wed, 13 Oct 2021 17:02:13 +0200	[thread overview]
Message-ID: <20211013150232.2942146-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

When building with 64KB pages, clang points out that xsk->chunk_size
can never be PAGE_SIZE:

drivers/net/ethernet/mellanox/mlx5/core/en/xsk/setup.c:19:22: 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]
        if (xsk->chunk_size > PAGE_SIZE ||
            ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~

I'm not familiar with the details of this code, but from a quick look
I found that it gets assigned from a 32-bit variable that can be
PAGE_SIZE, and that the layout of 'xsk' is not part of an ABI or
a hardware structure, so extending the members to 32 bits as well
should address both the behavior on 64KB page kernels, and the
warning I saw.

In older versions of this code, using PAGE_SIZE was the only
possibility, so this would have never worked on 64KB page kernels,
but the patch apparently did not address this case completely.

Fixes: 282c0c798f8e ("net/mlx5e: Allow XSK frames smaller than a page")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/params.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.h b/drivers/net/ethernet/mellanox/mlx5/core/en/params.h
index 879ad46d754e..b4167350b6df 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.h
@@ -7,8 +7,8 @@
 #include "en.h"
 
 struct mlx5e_xsk_param {
-	u16 headroom;
-	u16 chunk_size;
+	u32 headroom;
+	u32 chunk_size;
 };
 
 struct mlx5e_lro_param {
-- 
2.29.2


             reply	other threads:[~2021-10-13 15:02 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-13 15:02 Arnd Bergmann [this message]
2021-10-14  7:32 ` [PATCH] mlx5: allow larger xsk chunk_size Tariq Toukan
2021-10-15 13:27   ` Maxim Mikityanskiy
2021-10-15 15:16     ` Arnd Bergmann

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