[PATCH net 2/3] net/mlx5e: SHAMPO, Fix skb size check for 64K pages

[Tariq Toukan <tariqt@nvidia.com>]

From: Dragos Tatulea <dtatulea@nvidia.com>

mlx5e_hw_gro_skb_has_enough_space() uses a formula to check if there is
enough space in the skb frags to store more data. This formula is
incorrect for 64K page sizes and it triggers early GRO session
termination because the first fragment will blow up beyond
GRO_LEGACY_MAX_SIZE.

This patch adds a special case for page sizes >= GRO_LEGACY_MAX_SIZE
(64K) which will uses the skb->data_len instead. Within this context,
this check will be safe from fragment overflow.

It is expected that the if statement will be optimized out as the
check is done with constants.

Fixes: 92552d3abd32 ("net/mlx5e: HW_GRO cqe handler implementation")
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 77f7a1ca091d..ea4e7f486c8b 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -2350,7 +2350,10 @@ mlx5e_hw_gro_skb_has_enough_space(struct sk_buff *skb, u16 data_bcnt)
 {
 	int nr_frags = skb_shinfo(skb)->nr_frags;
 
-	return PAGE_SIZE * nr_frags + data_bcnt <= GRO_LEGACY_MAX_SIZE;
+	if (PAGE_SIZE >= GRO_LEGACY_MAX_SIZE)
+		return skb->len + data_bcnt <= GRO_LEGACY_MAX_SIZE;
+	else
+		return PAGE_SIZE * nr_frags + data_bcnt <= GRO_LEGACY_MAX_SIZE;
 }
 
 static void mlx5e_handle_rx_cqe_mpwrq_shampo(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe)
-- 
2.31.1