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

[Xing, Beilei]

> -----Original Message-----
> From: Min Hu (Connor) <humin29 at huawei.com>
> Sent: Wednesday, June 30, 2021 7:22 PM
> To: Yigit, Ferruh <ferruh.yigit at intel.com>; dev at dpdk.org; Thomas Monjalon
> <thomas at monjalon.net>; Andrew Rybchenko
> <andrew.rybchenko at oktetlabs.ru>
> Cc: Xing, Beilei <beilei.xing at intel.com>; Matan Azrad
> <matan at mellanox.com>; shahafs at nvidia.com; viacheslavo at nvidia.com
> Subject: Re: Question about 'rxm->hash.rss' and 'mb->hash.fdir'
> 
> Hi, Beilei, Matan, Shahaf, Viacheslav,
> 
> 	how about your opinion?

Agree with Ferruh.

> 
> 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?
> 
> > .
> >