Re: [dpdk-dev] [PATCH] net/igc: fix Rx packet size error

["Wang, Haiyue" <haiyue.wang@intel.com>]

> -----Original Message-----
> From: Zhang, AlvinX <alvinx.zhang@intel.com>
> Sent: Monday, April 19, 2021 15:15
> To: Wang, Haiyue <haiyue.wang@intel.com>; Guo, Jia <jia.guo@intel.com>
> Cc: dev@dpdk.org; stable@dpdk.org
> Subject: RE: [PATCH] net/igc: fix Rx packet size error
> 
> Hi Haiyue,
> 
> Thanks for your review.
> 
> > -----Original Message-----
> > From: Wang, Haiyue <haiyue.wang@intel.com>
> > Sent: Friday, April 16, 2021 9:57 AM
> > To: Zhang, AlvinX <alvinx.zhang@intel.com>; Guo, Jia <jia.guo@intel.com>
> > Cc: dev@dpdk.org; stable@dpdk.org
> > Subject: RE: [PATCH] net/igc: fix Rx packet size error
> >
> > > -----Original Message-----
> > > From: Zhang, AlvinX <alvinx.zhang@intel.com>
> > > Sent: Friday, April 16, 2021 09:14
> > > To: Wang, Haiyue <haiyue.wang@intel.com>; Guo, Jia <jia.guo@intel.com>
> > > Cc: dev@dpdk.org; Zhang, AlvinX <alvinx.zhang@intel.com>;
> > > stable@dpdk.org
> > > Subject: [PATCH] net/igc: fix Rx packet size error
> > >
> > > When DEV_RX_OFFLOAD_KEEP_CRC is enabled, the PMD will minus 4 bytes of
> > > CRC from the size of a packet, but the NIC will strip the CRC because
> > > the CRC strip bit in DVMOLR register is not cleared. This will cause
> > > the size of a packet to be 4 bytes less.
> > >
> > > This patch updates the CRC strip bit according to whether
> > > DEV_RX_OFFLOAD_KEEP_CRC is enabled.
> > >
> > > Fixes: a5aeb2b9e225 ("net/igc: support Rx and Tx")
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: Alvin Zhang <alvinx.zhang@intel.com>
> > > ---
> > >  drivers/net/igc/igc_txrx.c | 22 +++++++++++++---------
> > >  1 file changed, 13 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/net/igc/igc_txrx.c b/drivers/net/igc/igc_txrx.c
> > > index c0a5d5e..68b102d 100644
> > > --- a/drivers/net/igc/igc_txrx.c
> > > +++ b/drivers/net/igc/igc_txrx.c
> > > @@ -1290,20 +1290,24 @@ int eth_igc_rx_descriptor_status(void *rx_queue,
> > uint16_t offset)
> > >  	 * This needs to be done after enable.
> > >  	 */
> > >  	for (i = 0; i < dev->data->nb_rx_queues; i++) {
> > > +		uint32_t dvmolr;
> > > +
> > >  		rxq = dev->data->rx_queues[i];
> > >  		IGC_WRITE_REG(hw, IGC_RDH(rxq->reg_idx), 0);
> > > -		IGC_WRITE_REG(hw, IGC_RDT(rxq->reg_idx),
> > > -				rxq->nb_rx_desc - 1);
> > > +		IGC_WRITE_REG(hw, IGC_RDT(rxq->reg_idx), rxq->nb_rx_desc - 1);
> > > +
> > > +		dvmolr = IGC_READ_REG(hw, IGC_DVMOLR(rxq->queue_id));
> > >
> > >  		/* strip queue vlan offload */
> > > -		if (rxq->offloads & DEV_RX_OFFLOAD_VLAN_STRIP) {
> > > -			uint32_t dvmolr;
> > > -			dvmolr = IGC_READ_REG(hw, IGC_DVMOLR(rxq->queue_id));
> > > +		dvmolr = (rxq->offloads & DEV_RX_OFFLOAD_VLAN_STRIP) ?
> > > +			 (dvmolr | IGC_DVMOLR_STRVLAN) :
> > > +			 (dvmolr & ~IGC_DVMOLR_STRVLAN);
> >
> > Just use "if ... else .."to make code readable:
> >
> > 		if (rxq->offloads & DEV_RX_OFFLOAD_VLAN_STRIP)
> > 			dvmolr |= IGC_DVMOLR_STRVLAN;
> > 		else
> > 			dvmolr &= ~IGC_DVMOLR_STRVLAN;
> >
> >
> > >
> > > -			/* If vlan been stripped off, the CRC is meaningless. */
> >
> > Looks like we need to handle CRC & VLAN_STRIP co-exist issue:
> > 	If user enables VLAN strip, then keep CRC should be rejected,
> > 	and vice versa.
> 
> By default, the DEV_RX_OFFLOAD_KEEP_CRC does not been set,
> so if the user set the DEV_RX_OFFLOAD_KEEP_CRC and DEV_RX_OFFLOAD_VLAN_STRIP bits,
> this means the user really need CRC and VLAN stripped off, although the CRC is meaningless at this
> situation.
> So can we issue some warnings instead of changing the user's settings?

I re-think it again, no need to handle this now, until user complains about something.

Let's just fix the code style issue. ;-)

> 
> >
> > > -			dvmolr |= IGC_DVMOLR_STRVLAN | IGC_DVMOLR_STRCRC;
> > > -			IGC_WRITE_REG(hw, IGC_DVMOLR(rxq->reg_idx), dvmolr);
> > > -		}
> > > +		dvmolr = (offloads & DEV_RX_OFFLOAD_KEEP_CRC) ?
> > > +			 (dvmolr & ~IGC_DVMOLR_STRCRC) :
> > > +			 (dvmolr | IGC_DVMOLR_STRCRC);
> >
> > Just use "if ... else .."to make code readable:
> >
> > 		if (offloads & DEV_RX_OFFLOAD_KEEP_CRC)
> > 			dvmolr &= ~IGC_DVMOLR_STRCRC;
> > 		else
> > 			dvmolr |= IGC_DVMOLR_STRCRC;
> >
> > > +
> > > +		IGC_WRITE_REG(hw, IGC_DVMOLR(rxq->reg_idx), dvmolr);
> > >  	}
> > >
> > >  	return 0;
> > > --
> > > 1.8.3.1