netdev - [PATCH net-next v2 11/33] dpaa2-eth: add XDP frame size

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Message-ID: <158824567733.2172139.9600745532300479989.stgit@firesoul>
Date:   Thu, 30 Apr 2020 13:21:17 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     sameehj@...zon.com
Cc:     Ioana Radulescu <ruxandra.radulescu@....com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org, zorik@...zon.com,
        akiyano@...zon.com, gtzalik@...zon.com,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        David Ahern <dsahern@...il.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        steffen.klassert@...unet.com
Subject: [PATCH net-next v2 11/33] dpaa2-eth: add XDP frame size

The dpaa2-eth driver reserve some headroom used for hardware and
software annotation area in RX/TX buffers. Thus, xdp.data_hard_start
doesn't start at page boundary.

When XDP is configured the area reserved via dpaa2_fd_get_offset(fd) is
448 bytes of which XDP have reserved 256 bytes. As frame_sz is
calculated as an offset from xdp_buff.data_hard_start, an adjust from
the full PAGE_SIZE == DPAA2_ETH_RX_BUF_RAW_SIZE.

When doing XDP_REDIRECT, the driver doesn't need this reserved headroom
any-longer and allows xdp_do_redirect() to use it. This is an advantage
for the drivers own ndo-xdp_xmit, as it uses part of this headroom for
itself.  Patch also adjust frame_sz in this case.

The driver cannot support XDP data_meta, because it uses the headroom
just before xdp.data for struct dpaa2_eth_swa (DPAA2_ETH_SWA_SIZE=64),
when transmitting the packet. When transmitting a xdp_frame in
dpaa2_eth_xdp_xmit_frame (call via ndo_xdp_xmit) is uses this area to
store a pointer to xdp_frame and dma_size, which is used in TX
completion (free_tx_fd) to return frame via xdp_return_frame().

Cc: Ioana Radulescu <ruxandra.radulescu@....com>
Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
---
 drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index 8ec435ba7d27..a517b5190c8c 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -302,6 +302,9 @@ static u32 run_xdp(struct dpaa2_eth_priv *priv,
 	xdp_set_data_meta_invalid(&xdp);
 	xdp.rxq = &ch->xdp_rxq;

+	xdp.frame_sz = DPAA2_ETH_RX_BUF_RAW_SIZE -
+		(dpaa2_fd_get_offset(fd) - XDP_PACKET_HEADROOM);
+
 	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);

 	/* xdp.data pointer may have changed */
@@ -337,7 +340,11 @@ static u32 run_xdp(struct dpaa2_eth_priv *priv,
 		dma_unmap_page(priv->net_dev->dev.parent, addr,
 			       DPAA2_ETH_RX_BUF_SIZE, DMA_BIDIRECTIONAL);
 		ch->buf_count--;
+
+		/* Allow redirect use of full headroom */
 		xdp.data_hard_start = vaddr;
+		xdp.frame_sz = DPAA2_ETH_RX_BUF_RAW_SIZE;
+
 		err = xdp_do_redirect(priv->net_dev, &xdp, xdp_prog);
 		if (unlikely(err))
 			ch->stats.xdp_drop++;