RDMA/mlx5: Fix page size bitmap calculation for KSM mode

When using KSM (Key Scatter-gather Memory) access mode, the HW requires
the IOVA to be aligned to the selected page size.
Without this alignment, the HW may not function correctly.

Currently, mlx5_umem_mkc_find_best_pgsz() does not filter out page sizes
that would result in misaligned IOVAs for KSM mode. This can lead to
selecting page sizes that are incompatible with the given IOVA.

Fix this by filtering the page size bitmap when in KSM mode, keeping
only page sizes to which the IOVA is aligned to.

Fixes: fcfb03597b7d ("RDMA/mlx5: Align mkc page size capability check to PRM")
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20250824144839.154717-1-edwards@nvidia.com
Reviewed-by: Michael Guralnik <michaelgur@nvidia.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>

diff --git a/drivers/infiniband/hw/mlx5/mlx5_ib.h b/drivers/infiniband/hw/mlx5/mlx5_ib.h
index b43cf9c7e140320becd4eed62fa9ad26128763f5..09d82d5f95e35414c84fe6258a36b15b25bb6574 100644 (file)
--- a/drivers/infiniband/hw/mlx5/mlx5_ib.h
+++ b/drivers/infiniband/hw/mlx5/mlx5_ib.h
@@ -1805,6 +1805,10 @@ mlx5_umem_mkc_find_best_pgsz(struct mlx5_ib_dev *dev, struct ib_umem *umem,
 
        bitmap = GENMASK_ULL(max_log_entity_size_cap, min_log_entity_size_cap);
 
+       /* In KSM mode HW requires IOVA and mkey's page size to be aligned */
+       if (access_mode == MLX5_MKC_ACCESS_MODE_KSM && iova)
+               bitmap &= GENMASK_ULL(__ffs64(iova), 0);
+
        return ib_umem_find_best_pgsz(umem, bitmap, iova);
 }