From: Maxim Mikityanskiy <maximmi@nvidia.com>
Date: Sat, 1 Oct 2022 21:56:25 -0700
Subject: net/mlx5e: xsk: Print a warning in slow configurations
Patch-mainline: v6.1-rc1
Git-commit: c6f0420468fb2e7bbe006ed492608d63a4ac9e28
References: jsc#PED-1549

On striding RQ, when the XSK frame size doesn't match the MKey page
size, KLM is used for memory mappings, which is a slower mechanism than
MTT or KSM. It may happen in two cases:

1. Frame size is not a power of two (only possible in the unaligned mode
of XSK).

2. Frame size is 2048 bytes, and the firmware doesn't support MKey pages
smaller than 4096 bytes.

Depending on the case, print a warning and recommend to disable striding
RQ or upgrade the firmware.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/xsk/pool.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/pool.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xsk/pool.c
@@ -99,6 +99,15 @@ static int mlx5e_xsk_enable_locked(struc
 
 	mlx5e_build_xsk_param(pool, &xsk);
 
+	if (priv->channels.params.rq_wq_type == MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ &&
+	    mlx5e_mpwrq_umr_mode(priv->mdev, &xsk) == MLX5E_MPWRQ_UMR_MODE_OVERSIZED) {
+		const char *recommendation = is_power_of_2(xsk.chunk_size) ?
+			"Upgrade firmware" : "Disable striding RQ";
+
+		mlx5_core_warn(priv->mdev, "Expected slowdown with XSK frame size %u. %s for better performance.\n",
+			       xsk.chunk_size, recommendation);
+	}
+
 	if (!test_bit(MLX5E_STATE_OPENED, &priv->state)) {
 		/* XSK objects will be created on open. */
 		goto validate_closed;