[dpdk-dev] Question about 'rxm->hash.rss' and 'mb->hash.fdir'

[Min Hu (Connor)]

Hi, Beilei, Matan, Shahaf, Viacheslav,

	how about your opinion?

在 2021/6/30 17:34, Ferruh Yigit 写道:
> On 6/30/2021 3:45 AM, Min Hu (Connor) wrote:
>> Hi, all
>>      one question about 'rxm->hash.rss' and 'mb->hash.fdir'.
>>
>>      In Rx recv packets function,
>>      'rxm->hash.rss' will report rss hash result from Rx desc.
>>      'rxm->hash.fdir' will report filter identifier from Rx desc.
>>
>>      But function implementation differs from some PMDs. for example:
>>      i40e, MLX5 report the two at the same time if pkt_flags is set,like:
>> ******************************************
>>          if (pkt_flags & PKT_RX_RSS_HASH) {
>>              rxm->hash.rss =
>> rte_le_to_cpu_32(rxd.wb.qword0.hi_dword.rss);
>>          }
>>          if (pkt_flags & PKT_RX_FDIR) {
>>              mb->hash.fdir.hi =
>>          rte_le_to_cpu_32(rxdp->wb.qword3.hi_dword.fd_id);
>>          }
>> ********************************************
>>
>>      While, ixgbe only report one of the two. like:
>> ******************************************
>>          if (likely(pkt_flags & PKT_RX_RSS_HASH))
>>              mb->hash.rss = rte_le_to_cpu_32(
>>                  rxdp[j].wb.lower.hi_dword.rss);
>>          else if (pkt_flags & PKT_RX_FDIR) {
>>              mb->hash.fdir.hash = rte_le_to_cpu_16(
>>                  rxdp[j].wb.lower.hi_dword.csum_ip.csum) &
>>                  IXGBE_ATR_HASH_MASK;
>>              mb->hash.fdir.id = rte_le_to_cpu_16(
>>                  rxdp[j].wb.lower.hi_dword.csum_ip.ip_id);
>>          }
>> ********************************************
>>      So, what is application scenario for 'rxm->hash.rss' and 'mb->hash.fdir',
>> that is, why the two should be reported? How about reporting the two at the same
>> time?
>>      Thanks for  your reply.
> 
> 
> Hi Connor,
> 
> mbuf->hash is union, so it is not possible to set both 'hash.rss' & 'hash.fdir'.
> 
> I assume for i40e & mlx5 case 'pkt_flags' indicate which one is valid and only
> one is set in practice. Cc'ed driver mainteriners for more comment.

Thanks Ferruh,
	another question, why does user need this information:  rxm->hash.rss 
or mb->hash.fdir.hi ? what is the function?

> .
>