Re: [PATCH v4] net/bonding: call Tx prepare before Tx burst

[fengchengwen <fengchengwen@huawei.com>]

Hi Chas,

On 2022/10/11 3:42, Chas Williams wrote:
> 
> 
> On 10/8/22 23:36, Chengwen Feng wrote:
>>       uint16_t slaves[RTE_MAX_ETHPORTS];
>>       uint8_t tx_failed_flag = 0;
>>       uint16_t num_of_slaves;
>> +    uint16_t num_tx_prep;
>>         uint16_t max_nb_of_tx_pkts = 0;
>>   @@ -1320,12 +1339,18 @@ bond_ethdev_tx_burst_broadcast(void *queue, struct rte_mbuf **bufs,
>>       for (i = 0; i < nb_pkts; i++)
>>           rte_pktmbuf_refcnt_update(bufs[i], num_of_slaves - 1);
>>   +    /* It is rare that bond different PMDs together, so just call tx-prepare once */
>> +    num_tx_prep = rte_eth_tx_prepare(slaves[0], bd_tx_q->queue_id,
>> +                    bufs, nb_pkts);
> 
> You probably want to do this before you update the refcnt on the mbufs.
> Otherwise, the common rte_eth_tx_prepare operation, rte_vlan_insert, will
> fail since the refcnt will not be 1.

nice catch
v5 already sent to fix it, please review it. Thanks

> 
>> +    if (unlikely(num_tx_prep < nb_pkts))
>> +        tx_failed_flag = 1;
>> +
>>       /* Transmit burst on each active slave */
>>       for (i = 0; i < num_of_slaves; i++) {
>>           slave_tx_total[i] = rte_eth_tx_burst(slaves[i], bd_tx_q->queue_id,
>> -                    bufs, nb_pkts);
>> +                    bufs, num_tx_prep);
>>   -        if (unlikely(slave_tx_total[i] < nb_pkts))
>> +        if (unlikely(slave_tx_total[i] < num_tx_prep))
>>               tx_failed_flag = 1;
>>             /* record the value and slave index for the slave which transmits the
>> diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
>> index e8d1e1c658..b0396bb86e 100644
>> --- a/lib/ethdev/rte_ethdev.h
>> +++ b/lib/ethdev/rte_ethdev.h
>> @@ -6031,6 +6031,10 @@ uint16_t rte_eth_call_tx_callbacks(uint16_t port_id, uint16_t queue_id,
>>    * @see rte_eth_tx_prepare to perform some prior checks or adjustments
>>    * for offloads.
>>    *
>> + * @note This function must not modify mbufs (including packets data) unless
>> + * the refcnt is 1. The exception is the bonding PMD, which does not have
>> + * tx-prepare function, in this case, mbufs maybe modified.
> 
> Exactly. See my comment about calling prepare before you modify the refcnt.
> 
>> + *
>>    * @param port_id
>>    *   The port identifier of the Ethernet device.
>>    * @param queue_id
> .