net/mlx5e: SHAMPO, Fix skb size check for 64K pages

net/mlx5e: SHAMPO, Fix skb size check for 64K pages

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 uses the skb->len instead. Within this context,
the check is safe from fragment overflow because the hardware
will continuously fill the data up to the reservation size of 64K
and the driver will coalesce all data from the same page to the same
fragment. This means that the data will span one fragment or at most
two for such a large page size.

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>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/1762238915-1027590-3-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>