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.