net/bnxt: limit per-poll Rx representor pkts

Limit number of representor packets transferred per poll
to requested burst size.

Fixes: 6dc83230b43b ("net/bnxt: support port representor data path")
Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
Reviewed-by: Ajit Kumar Khaparde <ajit.khaparde@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Cc: stable@dpdk.org
---
 drivers/net/bnxt/bnxt_rxr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On Mon, Dec 14, 2020 at 10:54 AM Lance Richardson
<lance.richardson@broadcom.com> wrote:
>
> Limit number of representor packets transferred per poll
> to requested burst size.
>
> Fixes: 6dc83230b43b ("net/bnxt: support port representor data path")
> Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
> Reviewed-by: Ajit Kumar Khaparde <ajit.khaparde@broadcom.com>
> Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
> Cc: stable@dpdk.org

Patch applied to dpdk-next-net-brcm. Thanks

> ---
>  drivers/net/bnxt/bnxt_rxr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/bnxt/bnxt_rxr.c b/drivers/net/bnxt/bnxt_rxr.c
> index 2b1dd97617..ffdeeecc3a 100644
> --- a/drivers/net/bnxt/bnxt_rxr.c
> +++ b/drivers/net/bnxt/bnxt_rxr.c
> @@ -901,7 +901,7 @@ uint16_t bnxt_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>                 }
>
>                 raw_cons = NEXT_RAW_CMP(raw_cons);
> -               if (nb_rx_pkts == nb_pkts || evt)
> +               if (nb_rx_pkts == nb_pkts || nb_rep_rx_pkts == nb_pkts || evt)
>                         break;
>                 /* Post some Rx buf early in case of larger burst processing */
>                 if (nb_rx_pkts == BNXT_RX_POST_THRESH)
> --
> 2.25.1
>
>
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On 12/14/2020 6:53 PM, Lance Richardson wrote:
> Limit number of representor packets transferred per poll
> to requested burst size.
> 

Hi Lance,

Can you please describe the impact of the change? Since it has a fixes line, it 
seems it is fixing something but it is not clear what is fixed.

> Fixes: 6dc83230b43b ("net/bnxt: support port representor data path")
> Signed-off-by: Lance Richardson <lance.richardson@broadcom.com>
> Reviewed-by: Ajit Kumar Khaparde <ajit.khaparde@broadcom.com>
> Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
> Cc: stable@dpdk.org
> ---
>   drivers/net/bnxt/bnxt_rxr.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/bnxt/bnxt_rxr.c b/drivers/net/bnxt/bnxt_rxr.c
> index 2b1dd97617..ffdeeecc3a 100644
> --- a/drivers/net/bnxt/bnxt_rxr.c
> +++ b/drivers/net/bnxt/bnxt_rxr.c
> @@ -901,7 +901,7 @@ uint16_t bnxt_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
>   		}
>   
>   		raw_cons = NEXT_RAW_CMP(raw_cons);
> -		if (nb_rx_pkts == nb_pkts || evt)
> +		if (nb_rx_pkts == nb_pkts || nb_rep_rx_pkts == nb_pkts || evt)
>   			break;
>   		/* Post some Rx buf early in case of larger burst processing */
>   		if (nb_rx_pkts == BNXT_RX_POST_THRESH)
>

On Wed, Jan 6, 2021 at 4:27 AM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>
> On 12/14/2020 6:53 PM, Lance Richardson wrote:
> > Limit number of representor packets transferred per poll
> > to requested burst size.
> >
>
> Hi Lance,
>
> Can you please describe the impact of the change? Since it has a fixes line, it
> seems it is fixing something but it is not clear what is fixed.
>
Hi Ferruh,

How does this look:

Without some limit on the number of packets transferred from the
hw ring to the representor ring per burst receive call, an entire ring's
worth of packets can be transferred. This can break assumptions
about ring indices (index on return could be identical to the index
on entry, which is assumed to mean that no packets were processed),
and can result in representor packets being dropped unnecessarily
due to representor ring overflow.

Fix by limiting the number of representor packets transferred per
poll to requested burst size.

Thanks,
    Lance

On 1/6/2021 8:54 PM, Lance Richardson wrote:
> On Wed, Jan 6, 2021 at 4:27 AM Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>>
>> On 12/14/2020 6:53 PM, Lance Richardson wrote:
>>> Limit number of representor packets transferred per poll
>>> to requested burst size.
>>>
>>
>> Hi Lance,
>>
>> Can you please describe the impact of the change? Since it has a fixes line, it
>> seems it is fixing something but it is not clear what is fixed.
>>
> Hi Ferruh,
> 
> How does this look:
> 
> Without some limit on the number of packets transferred from the
> hw ring to the representor ring per burst receive call, an entire ring's
> worth of packets can be transferred. This can break assumptions
> about ring indices (index on return could be identical to the index
> on entry, which is assumed to mean that no packets were processed),
> and can result in representor packets being dropped unnecessarily
> due to representor ring overflow.
> 
> Fix by limiting the number of representor packets transferred per
> poll to requested burst size.
> 

Thank you, updated the commit log in next-net.