linux-kernel - [PATCH net] mlx5: avoid 64-bit division in dr_icm_pool_mr

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Message-Id: <20191002121241.D74DAE04C7@unicorn.suse.cz>
Date:   Wed,  2 Oct 2019 14:12:41 +0200 (CEST)
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Saeed Mahameed <saeedm@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>
Cc:     Alex Vesker <valex@...lanox.com>, Borislav Petkov <bp@...en8.de>,
        Stephen Hemminger <stephen@...workplumber.org>,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net] mlx5: avoid 64-bit division in dr_icm_pool_mr_create()

Recently added code introduces 64-bit division in dr_icm_pool_mr_create()
so that build on 32-bit architectures fails with

  ERROR: "__umoddi3" [drivers/net/ethernet/mellanox/mlx5/core/mlx5_core.ko] undefined!

As the divisor is always a power of 2, we can use bitwise operation
instead.

Fixes: 29cf8febd185 ("net/mlx5: DR, ICM pool memory allocator")
Reported-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Michal Kubecek <mkubecek@...e.cz>
---
 drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c b/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
index 913f1e5aaaf2..d7c7467e2d53 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/steering/dr_icm_pool.c
@@ -137,7 +137,8 @@ dr_icm_pool_mr_create(struct mlx5dr_icm_pool *pool,
 
 	icm_mr->icm_start_addr = icm_mr->dm.addr;
 
-	align_diff = icm_mr->icm_start_addr % align_base;
+	/* align_base is always a power of 2 */
+	align_diff = icm_mr->icm_start_addr & (align_base - 1);
 	if (align_diff)
 		icm_mr->used_length = align_base - align_diff;
 
-- 
2.23.0