Re: [dpdk-dev] Question about jumbo frame support on ixgbe

["Zhao1, Wei" <wei.zhao1@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Stephen
> Hemminger
> Sent: Wednesday, October 31, 2018 11:49 PM
> To: Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp>
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] Question about jumbo frame support on ixgbe
> 
> On Wed, 31 Oct 2018 17:22:02 +0900
> Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp> wrote:
> 
> > Hi,
> >
> > I have a very basic question about jumbo frame support for ixgbe.
> >
> > I understand that some drivers support jumbo frame and if it receive
> > jumbo packet (greater than 1500 byte), it creates mbuf chains and pass
> > it to DPDK application through e.g. rte_eth_rx_burst.
> >
> > However it looks that ixgbe driver does not support jumbo frame.
> >
> > Q1. Is my understanding above correct?
> > Q2. If A1 equals YES, then are there any future plan to support jumbo
> > frame on ixgbe?
> >
> > BR,
> > Hideyuki Yamashita
> > NTT TechnoCross
> >
> 
> I don't work for Intel, and haven't tried jumbo frames on ixgbe.
> The hardware does support jumbo frames.
> You might be confusing the overlapping receive offload values.
> 
> The setting for using jumbo frames is in current DPDK is shown as available in
> device as:
> 	rx_offload_capa & DEV_RX_OFFLOAD_JUMBO_FRAME In order to
> use it, this bit must be setn in rx_conf that is passed to
> rte_eth_rx_queue_setup
> 

Yes, 
dev_conf.rxmode.offloads bits of DEV_RX_OFFLOAD_JUMBO_FRAME should be set to 1 when start port in API rte_eth_dev_start().
IF you are using testpmd  APP, you should set struct rte_eth_rxmode rx_mode  offloads bits of DEV_RX_OFFLOAD_JUMBO_FRAME.
 but  I think only set this bit of DEV_RX_OFFLOAD_JUMBO_FRAME is not sufficient for enable this jumbo frame feature,
Because in PMD code, this flag do not set bit of  IXGBE_HLREG0_JUMBOEN in register IXGBE_HLREG0, I think this is something
We need update.

> 
> The feature bit that creates multiple mbuf's if necessary on receive is:
> 	rx_offload_capa  & DEV_RX_OFFLOAD_SCATTER Likewise to enable it,
> this must be set in rte_eth_rx_queue_setup rx_conf.
> 
> 

Yes, this step can chose scatter rx function for PMD, but not MUST, details of discussion for this is in other mail.
https://mails.dpdk.org/archives/dev/2018-November/117771.html