[dpdk-dev] [PATCH v12 0/6] add Tx preparation

[Rahul Lakkireddy]

Hi Thomas,

On Monday, November 11/28/16, 2016 at 16:33:06 +0530, Thomas Monjalon wrote:
> We need attention of every PMD developers on this thread.
> 
> Reminder of what Konstantin suggested:
> "
> - if the PMD supports TX offloads AND
> - if to be able use any of these offloads the upper layer SW would have to:
>     * modify the contents of the packet OR
>     * obey HW specific restrictions
> then it is a PMD developer responsibility to provide tx_prep() that would implement
> expected modifications of the packet contents and restriction checks.
> Otherwise, tx_prep() implementation is not required and can be safely set to NULL.      
> "
> 
> I copy/paste also my previous conclusion:
> 
> Before txprep, there is only one API: the application must prepare the
> packets checksum itself (get_psd_sum in testpmd).
> With txprep, the application have 2 choices: keep doing the job itself
> or call txprep which calls a PMD-specific function.
> The question is: does non-Intel drivers need a checksum preparation for TSO?
> Will it behave well if txprep does nothing in these drivers?
> 
> When looking at the code, most of drivers handle the TSO flags.
> But it is hard to know whether they rely on the pseudo checksum or not.
> 
> git grep -l 'PKT_TX_UDP_CKSUM\|PKT_TX_TCP_CKSUM\|PKT_TX_TCP_SEG' drivers/net/
> 
> drivers/net/bnxt/bnxt_txr.c
> drivers/net/cxgbe/sge.c
> drivers/net/e1000/em_rxtx.c
> drivers/net/e1000/igb_rxtx.c
> drivers/net/ena/ena_ethdev.c
> drivers/net/enic/enic_rxtx.c
> drivers/net/fm10k/fm10k_rxtx.c
> drivers/net/i40e/i40e_rxtx.c
> drivers/net/ixgbe/ixgbe_rxtx.c
> drivers/net/mlx4/mlx4.c
> drivers/net/mlx5/mlx5_rxtx.c
> drivers/net/nfp/nfp_net.c
> drivers/net/qede/qede_rxtx.c
> drivers/net/thunderx/nicvf_rxtx.c
> drivers/net/virtio/virtio_rxtx.c
> drivers/net/vmxnet3/vmxnet3_rxtx.c
> 
> Please, we need a comment for each driver saying
> "it is OK, we do not need any checksum preparation for TSO"
> or
> "yes we have to implement tx_prepare or TSO will not work in this mode"

For CXGBE PMD, "it is OK, we do not need any checksum preparation for
TSO".

Thanks,
Rahul