net/mlx5: split Rx flows to provide metadata copy

net/mlx5: split Rx flows to provide metadata copy

Values set by MARK and SET_META actions should be carried over
to the VF representor in case of flow miss on Tx path. However,
as not all metadata registers are preserved across the different
domains (NIC Rx/Tx and E-Switch FDB), as a workaround, those
values should be carried by reg_c's which are preserved across
domains and copied to STE flow_tag (MARK) and reg_b (META) fields
in the last stage of flow steering, in order to scatter those
values to flow_tag and flow_table_metadata of CQE.

While reg_c[meta] can be copied to reg_b simply by modify-header
action (it is supported by hardware), it is not possible to copy
reg_c[mark] to the STE flow_tag as flow_tag is not a metadata
register and this is not supported by hardware. Instead, it should
be manually set by a flow per MARK ID. For this purpose, there
should be a dedicated flow table - RX_CP_TBL and all the Rx flow
should pass by the table to properly copy values.

As the last action of Rx flow steering must be a terminal action
such as QUEUE, RSS or DROP, if a user flow has Q/RSS action, the
flow must be split in order to pass by the RX_CP_TBL. And the
remained Q/RSS action will be performed by another dedicated
action table - RX_ACT_TBL.

For example, for an ingress flow:
    pattern,
    actions_having_QRSS
it must be split into two flows. The first one is,
    pattern,
    actions_except_QRSS / copy (reg_c[2] := flow_id) / jump to RX_CP_TBL
and the second one in RX_ACT_TBL.
    (if reg_c[2] == flow_id),
    action_QRSS
where flow_id is uniquely allocated and managed identifier.

This patch implements the Rx flow splitting and build the RX_ACT_TBL.
Also, per each egress flow on NIC Tx, a copy action (reg_c[]= reg_a)
should be added in order to transfer metadata from WQE.

Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>