net/mlx5e: TC, Offload rewrite and mirror to both internal and external dests

Firmware has the limitation that it cannot offload a rule with rewrite
and mirror to internal and external destinations simultaneously.

This patch adds a workaround to this issue. Here the destination array
is split again, just like what's done in previous commit, but after
the action indexed by split_count - 1. An extra rule is added for the
leftover destinations. Such rule can be offloaded, even there are
destinations to both internal and external destinations, because the
header rewrite is left in the original FTE.

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/20240808055927.2059700-5-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Jianbo Liu

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

@@ -1742,12 +1742,17 @@ has_encap_dests(struct mlx5_flow_attr *attr)
 static int
 extra_split_attr_dests_needed(struct mlx5e_tc_flow *flow, struct mlx5_flow_attr *attr)
 {
+	bool int_dest = false, ext_dest = false;
 	struct mlx5_esw_flow_attr *esw_attr;
+	int i;
 
 	if (flow->attr != attr ||
 	    !list_is_first(&attr->list, &flow->attrs))
 		return 0;
 
+	if (flow_flag_test(flow, SLOW))
+		return 0;
+
 	esw_attr = attr->esw_attr;
 	if (!esw_attr->split_count ||
 	    esw_attr->split_count == esw_attr->out_count - 1)
@@ -1758,6 +1763,18 @@ extra_split_attr_dests_needed(struct mlx5e_tc_flow *flow, struct mlx5_flow_attr
 	     MLX5_ESW_DEST_CHAIN_WITH_SRC_PORT_CHANGE))
 		return esw_attr->split_count + 1;
 
+	for (i = esw_attr->split_count; i < esw_attr->out_count; i++) {
+		/* external dest with encap is considered as internal by firmware */
+		if (esw_attr->dests[i].vport == MLX5_VPORT_UPLINK &&
+		    !(esw_attr->dests[i].flags & MLX5_ESW_DEST_ENCAP_VALID))
+			ext_dest = true;
+		else
+			int_dest = true;
+
+		if (ext_dest && int_dest)
+			return esw_attr->split_count;
+	}
+
 	return 0;
 }