Re: [PATCH net V2 2/3] net/mlx5e: SHAMPO, Fix skb size check for 64K pages

[Simon Horman]

On Tue, Nov 04, 2025 at 08:48:34AM +0200, Tariq Toukan wrote:
> From: Dragos Tatulea <dtatulea@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> Signed-off-by: Tariq Toukan <tariqt@xxxxxxxxxx>

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>