Subject: [net-next V3 14/15] net/mlx5e: XSK, Exclude tailroom from non-linear SKBs memory calculations

From: Saeed Mahameed <[email-masked]>
Date: Fri, 2 Feb 2024 11:08:53 -0800

From: Carolina Jubran <[email-masked]>

Packet data buffers lack reserved headroom or tailroom,
and SKBs are allocated on a side memory when needed.

Exclude the tailroom from the SKB size calculations.

Signed-off-by: Carolina Jubran <[email-masked]>
Reviewed-by: Tariq Toukan <[email-masked]>
Signed-off-by: Saeed Mahameed <[email-masked]>
---
 .../net/ethernet/mellanox/mlx5/core/en/params.c   | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
index 5d213a9886f1..b9d39ef8053c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/params.c
@@ -240,11 +240,14 @@ static u32 mlx5e_rx_get_linear_sz_xsk(struct mlx5e_params *params,
 	return xsk->headroom + hw_mtu;
 }
 
-static u32 mlx5e_rx_get_linear_sz_skb(struct mlx5e_params *params, bool xsk)
+static u32 mlx5e_rx_get_linear_sz_skb(struct mlx5e_params *params, bool no_head_tail_room)
 {
-	/* SKBs built on XDP_PASS on XSK RQs don't have headroom. */
-	u16 headroom = xsk ? 0 : mlx5e_get_linear_rq_headroom(params, NULL);
 	u32 hw_mtu = MLX5E_SW2HW_MTU(params, params->sw_mtu);
+	u16 headroom;
+
+	if (no_head_tail_room)
+		return SKB_DATA_ALIGN(hw_mtu);
+	headroom = mlx5e_get_linear_rq_headroom(params, NULL);
 
 	return MLX5_SKB_FRAG_SZ(headroom + hw_mtu);
 }
@@ -289,7 +292,11 @@ bool mlx5e_rx_is_linear_skb(struct mlx5_core_dev *mdev,
 	if (params->packet_merge.type != MLX5E_PACKET_MERGE_NONE)
 		return false;
 
-	/* Both XSK and non-XSK cases allocate an SKB on XDP_PASS. Packet data
+	/* Call mlx5e_rx_get_linear_sz_skb with the no_head_tail_room parameter set
+	 * to exclude headroom and tailroom from calculations.
+	 * no_head_tail_room is true when SKB is built on XDP_PASS on XSK RQs
+	 * since packet data buffers don't have headroom and tailroom resreved for the SKB.
+	 * Both XSK and non-XSK cases allocate an SKB on XDP_PASS. Packet data
 	 * must fit into a CPU page.
 	 */
 	if (mlx5e_rx_get_linear_sz_skb(params, xsk) > PAGE_SIZE)
-- 
2.43.0