[PATCH 1/8] net/txgbe: fix Rx buffer size in configure register

[Jiawen Wu]

On Friday, January 27, 2023 11:36 PM, Ferruh Yigit wrote:
> On 1/18/2023 6:00 AM, Jiawen Wu wrote:
> > When round up buffer size to 1K, to configure the register, hardware
> > will receive packets exceeding the buffer size in LRO mode. It will
> > cause a segment fault in the receive function.
> >
> > Fixes: be797cbf4582 ("net/txgbe: add Rx and Tx init")
> > Cc: stable at dpdk.org
> >
> > Signed-off-by: Jiawen Wu <jiawenwu at trustnetic.com>
> > ---
> >  drivers/net/txgbe/txgbe_rxtx.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/txgbe/txgbe_rxtx.c
> > b/drivers/net/txgbe/txgbe_rxtx.c index ac1bba08a3..ae70ca3beb 100644
> > --- a/drivers/net/txgbe/txgbe_rxtx.c
> > +++ b/drivers/net/txgbe/txgbe_rxtx.c
> > @@ -4382,7 +4382,7 @@ txgbe_dev_rx_init(struct rte_eth_dev *dev)
> >  		 */
> >  		buf_size = (uint16_t)(rte_pktmbuf_data_room_size(rxq->mb_pool) -
> >  			RTE_PKTMBUF_HEADROOM);
> > -		buf_size = ROUND_UP(buf_size, 0x1 << 10);
> > +		buf_size = ROUND_DOWN(buf_size, 0x1 << 10);
> >  		srrctl |= TXGBE_RXCFG_PKTLEN(buf_size);
> >
> 
> What if 'buf_size' is less than 1K, won't 'ROUND_DOWN' make it 0, and I assume
> setting 0 to register may cause problem.
> 

It is indeed a problem, I will fix it.

> And according to the code comment for 'buf_size' [1], buffer size can't be more than
> 16K, but technically 'buf_size' can be more than 16K.
> Does the HW constrain values larger than 16K? If not the 'buf_size'
> value needs to be checked against the 16K limit.
> 

There is a macro that defines the conversion to limit 16K.

#define PKTLEN(v)     ROUND_OVER(v, 14, 10)
#define ROUND_OVER(x, maxbits, unitbits) \
	((x) >= 1 << (maxbits) ? 0 : (x) >> (unitbits))

> 
> 
> 
> [1]
>  /*
>   * Configure the RX buffer size in the PKTLEN field of
>   * the RXCFG register of the queue.
>   * The value is in 1 KB resolution. Valid values can be from
>   * 1 KB to 16 KB.
>   */
>