net/mlx5e: XDP TX forwarding support

Adding support for XDP_TX forwarding from xdp program.
Using XDP, now user can loop packets out of the same port.

We create a dedicated TX SQ for each channel that will serve
XDP programs that return XDP_TX action to loop packets back to
the wire directly from the channel RQ RX path.

For that RX pages will now need to be mapped bi-directionally,
and on XDP_TX action we will sync the page back to device then
queue it into SQ for transmission.  The XDP xmit frame function will
report back to the RX path if the page was consumed (transmitted), if so,
RX path will forget about that page as if it were released to the stack.
Later on, on XDP TX completion, the page will be released back to the
page cache.

For simplicity this patch will hit a doorbell on every XDP TX packet.

Next patch will introduce a xmit more like mechanism that will
queue up more than one packet into SQ w/o notifying the hardware,
once RX napi loop is done we will hit doorbell once for all XDP TX
packets form the previous loop.  This should drastically improve
XDP TX performance.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 35 insertions, 4 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
index f02f24cfcb7a..70a717382357 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tx.c
@@ -495,16 +495,13 @@ bool mlx5e_poll_tx_cq(struct mlx5e_cq *cq, int napi_budget)
 	return (i == MLX5E_TX_CQ_POLL_BUDGET);
 }
 
-void mlx5e_free_tx_descs(struct mlx5e_sq *sq)
+static void mlx5e_free_txq_sq_descs(struct mlx5e_sq *sq)
 {
 	struct mlx5e_tx_wqe_info *wi;
 	struct sk_buff *skb;
 	u16 ci;
 	int i;
 
-	if (sq->type != MLX5E_SQ_TXQ)
-		return;
-
 	while (sq->cc != sq->pc) {
 		ci = sq->cc & sq->wq.sz_m1;
 		skb = sq->db.txq.skb[ci];
@@ -526,3 +523,37 @@ void mlx5e_free_tx_descs(struct mlx5e_sq *sq)
 		sq->cc += wi->num_wqebbs;
 	}
 }
+
+static void mlx5e_free_xdp_sq_descs(struct mlx5e_sq *sq)
+{
+	struct mlx5e_sq_wqe_info *wi;
+	struct mlx5e_dma_info *di;
+	u16 ci;
+
+	while (sq->cc != sq->pc) {
+		ci = sq->cc & sq->wq.sz_m1;
+		di = &sq->db.xdp.di[ci];
+		wi = &sq->db.xdp.wqe_info[ci];
+
+		if (wi->opcode == MLX5_OPCODE_NOP) {
+			sq->cc++;
+			continue;
+		}
+
+		sq->cc += wi->num_wqebbs;
+
+		mlx5e_page_release(&sq->channel->rq, di, false);
+	}
+}
+
+void mlx5e_free_sq_descs(struct mlx5e_sq *sq)
+{
+	switch (sq->type) {
+	case MLX5E_SQ_TXQ:
+		mlx5e_free_txq_sq_descs(sq);
+		break;
+	case MLX5E_SQ_XDP:
+		mlx5e_free_xdp_sq_descs(sq);
+		break;
+	}
+}