Merge branch 'xdp-grow-tail'

Jesper Dangaard Brouer says:

====================
V4:
- Fixup checkpatch.pl issues
- Collected more ACKs

V3:
- Fix issue on virtio_net patch spotted by Jason Wang
- Adjust name for variable in mlx5 patch
- Collected more ACKs

V2:
- Fix bug in mlx5 for XDP_PASS case
- Collected nitpicks and ACKs from mailing list

V1:
- Fix bug in dpaa2

XDP have evolved to support several frame sizes, but xdp_buff was not
updated with this information. This have caused the side-effect that
XDP frame data hard end is unknown. This have limited the BPF-helper
bpf_xdp_adjust_tail to only shrink the packet. This patchset address
this and add packet tail extend/grow.

The purpose of the patchset is ALSO to reserve a memory area that can be
used for storing extra information, specifically for extending XDP with
multi-buffer support. One proposal is to use same layout as
skb_shared_info, which is why this area is currently 320 bytes.

When converting xdp_frame to SKB (veth and cpumap), the full tailroom
area can now be used and SKB truesize is now correct. For most
drivers this result in a much larger tailroom in SKB "head" data
area. The network stack can now take advantage of this when doing SKB
coalescing. Thus, a good driver test is to use xdp_redirect_cpu from
samples/bpf/ and do some TCP stream testing.

Use-cases for tail grow/extend:
(1) IPsec / XFRM needs a tail extend[1][2].
(2) DNS-cache responses in XDP.
(3) HAProxy ALOHA would need it to convert to XDP.
(4) Add tail info e.g. timestamp and collect via tcpdump

[1] http://vger.kernel.org/netconf2019_files/xfrm_xdp.pdf
[2] http://vger.kernel.org/netconf2019.html

Examples on howto access the tail area of an XDP packet is shown in the
XDP-tutorial example[3].

[3] https://github.com/xdp-project/xdp-tutorial/blob/master/experiment01-tailgrow/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 27 insertions, 7 deletions

diff --git a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
index 4622c4ea2e46..a39e2cb384dd 100644
--- a/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
+++ b/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c
@@ -1095,19 +1095,31 @@ xdp_out:
 	return ERR_PTR(-result);
 }
 
+static unsigned int ixgbevf_rx_frame_truesize(struct ixgbevf_ring *rx_ring,
+					      unsigned int size)
+{
+	unsigned int truesize;
+
+#if (PAGE_SIZE < 8192)
+	truesize = ixgbevf_rx_pg_size(rx_ring) / 2; /* Must be power-of-2 */
+#else
+	truesize = ring_uses_build_skb(rx_ring) ?
+		SKB_DATA_ALIGN(IXGBEVF_SKB_PAD + size) +
+		SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) :
+		SKB_DATA_ALIGN(size);
+#endif
+	return truesize;
+}
+
 static void ixgbevf_rx_buffer_flip(struct ixgbevf_ring *rx_ring,
 				   struct ixgbevf_rx_buffer *rx_buffer,
 				   unsigned int size)
 {
-#if (PAGE_SIZE < 8192)
-	unsigned int truesize = ixgbevf_rx_pg_size(rx_ring) / 2;
+	unsigned int truesize = ixgbevf_rx_frame_truesize(rx_ring, size);
 
+#if (PAGE_SIZE < 8192)
 	rx_buffer->page_offset ^= truesize;
 #else
-	unsigned int truesize = ring_uses_build_skb(rx_ring) ?
-				SKB_DATA_ALIGN(IXGBEVF_SKB_PAD + size) :
-				SKB_DATA_ALIGN(size);
-
 	rx_buffer->page_offset += truesize;
 #endif
 }
@@ -1125,6 +1137,11 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
 
 	xdp.rxq = &rx_ring->xdp_rxq;
 
+	/* Frame size depend on rx_ring setup when PAGE_SIZE=4K */
+#if (PAGE_SIZE < 8192)
+	xdp.frame_sz = ixgbevf_rx_frame_truesize(rx_ring, 0);
+#endif
+
 	while (likely(total_rx_packets < budget)) {
 		struct ixgbevf_rx_buffer *rx_buffer;
 		union ixgbe_adv_rx_desc *rx_desc;
@@ -1157,7 +1174,10 @@ static int ixgbevf_clean_rx_irq(struct ixgbevf_q_vector *q_vector,
 			xdp.data_hard_start = xdp.data -
 					      ixgbevf_rx_offset(rx_ring);
 			xdp.data_end = xdp.data + size;
-
+#if (PAGE_SIZE > 4096)
+			/* At larger PAGE_SIZE, frame_sz depend on len size */
+			xdp.frame_sz = ixgbevf_rx_frame_truesize(rx_ring, size);
+#endif
 			skb = ixgbevf_run_xdp(adapter, rx_ring, &xdp);
 		}