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>
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