6.12-stable review patch. If anyone has any objections, please let me know.
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From: Or Har-Toov ohartoov@nvidia.com
[ Upstream commit 1a7c18c485bf17ef408d5ebb7f83e1f8ef329585 ]
The mlx5 driver currently derives max_qp_wr directly from the log_max_qp_sz HCA capability:
props->max_qp_wr = 1 << MLX5_CAP_GEN(mdev, log_max_qp_sz);
However, this value represents the number of WQEs in units of Basic Blocks (see MLX5_SEND_WQE_BB), not actual number of WQEs. Since the size of a WQE can vary depending on transport type and features (e.g., atomic operations, UMR, LSO), the actual number of WQEs can be significantly smaller than the WQEBB count suggests.
This patch introduces a conservative estimation of the worst-case WQE size — considering largest segments possible with 1 SGE and no inline data or special features. It uses this to derive a more accurate max_qp_wr value.
Fixes: 938fe83c8dcb ("net/mlx5_core: New device capabilities handling") Link: https://patch.msgid.link/r/7d992c9831c997ed5c33d30973406dc2dcaf5e89.17550887... Reported-by: Chuck Lever cel@kernel.org Closes: https://lore.kernel.org/all/20250506142202.GJ2260621@ziepe.ca/ Signed-off-by: Or Har-Toov ohartoov@nvidia.com Signed-off-by: Leon Romanovsky leonro@nvidia.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/infiniband/hw/mlx5/main.c | 48 ++++++++++++++++++++++++++++++- 1 file changed, 47 insertions(+), 1 deletion(-)
diff --git a/drivers/infiniband/hw/mlx5/main.c b/drivers/infiniband/hw/mlx5/main.c index 435c456a4fd5b..29d0bc583169b 100644 --- a/drivers/infiniband/hw/mlx5/main.c +++ b/drivers/infiniband/hw/mlx5/main.c @@ -13,6 +13,7 @@ #include <linux/dma-mapping.h> #include <linux/slab.h> #include <linux/bitmap.h> +#include <linux/log2.h> #include <linux/sched.h> #include <linux/sched/mm.h> #include <linux/sched/task.h> @@ -865,6 +866,51 @@ static void fill_esw_mgr_reg_c0(struct mlx5_core_dev *mdev, resp->reg_c0.mask = mlx5_eswitch_get_vport_metadata_mask(); }
+/* + * Calculate maximum SQ overhead across all QP types. + * Other QP types (REG_UMR, UC, RC, UD/SMI/GSI, XRC_TGT) + * have smaller overhead than the types calculated below, + * so they are implicitly included. + */ +static u32 mlx5_ib_calc_max_sq_overhead(void) +{ + u32 max_overhead_xrc, overhead_ud_lso, a, b; + + /* XRC_INI */ + max_overhead_xrc = sizeof(struct mlx5_wqe_xrc_seg); + max_overhead_xrc += sizeof(struct mlx5_wqe_ctrl_seg); + a = sizeof(struct mlx5_wqe_atomic_seg) + + sizeof(struct mlx5_wqe_raddr_seg); + b = sizeof(struct mlx5_wqe_umr_ctrl_seg) + + sizeof(struct mlx5_mkey_seg) + + MLX5_IB_SQ_UMR_INLINE_THRESHOLD / MLX5_IB_UMR_OCTOWORD; + max_overhead_xrc += max(a, b); + + /* UD with LSO */ + overhead_ud_lso = sizeof(struct mlx5_wqe_ctrl_seg); + overhead_ud_lso += sizeof(struct mlx5_wqe_eth_pad); + overhead_ud_lso += sizeof(struct mlx5_wqe_eth_seg); + overhead_ud_lso += sizeof(struct mlx5_wqe_datagram_seg); + + return max(max_overhead_xrc, overhead_ud_lso); +} + +static u32 mlx5_ib_calc_max_qp_wr(struct mlx5_ib_dev *dev) +{ + struct mlx5_core_dev *mdev = dev->mdev; + u32 max_wqe_bb_units = 1 << MLX5_CAP_GEN(mdev, log_max_qp_sz); + u32 max_wqe_size; + /* max QP overhead + 1 SGE, no inline, no special features */ + max_wqe_size = mlx5_ib_calc_max_sq_overhead() + + sizeof(struct mlx5_wqe_data_seg); + + max_wqe_size = roundup_pow_of_two(max_wqe_size); + + max_wqe_size = ALIGN(max_wqe_size, MLX5_SEND_WQE_BB); + + return (max_wqe_bb_units * MLX5_SEND_WQE_BB) / max_wqe_size; +} + static int mlx5_ib_query_device(struct ib_device *ibdev, struct ib_device_attr *props, struct ib_udata *uhw) @@ -1023,7 +1069,7 @@ static int mlx5_ib_query_device(struct ib_device *ibdev, props->max_mr_size = ~0ull; props->page_size_cap = ~(min_page_size - 1); props->max_qp = 1 << MLX5_CAP_GEN(mdev, log_max_qp); - props->max_qp_wr = 1 << MLX5_CAP_GEN(mdev, log_max_qp_sz); + props->max_qp_wr = mlx5_ib_calc_max_qp_wr(dev); max_rq_sg = MLX5_CAP_GEN(mdev, max_wqe_sz_rq) / sizeof(struct mlx5_wqe_data_seg); max_sq_desc = min_t(int, MLX5_CAP_GEN(mdev, max_wqe_sz_sq), 512);