libeth: xdp: add XDP_TX buffers sending

Start adding XDP-specific code to libeth, namely handling XDP_TX buffers
(only sending).
The idea is that we accumulate up to 16 buffers on the stack, then,
if either the limit is reached or the polling is finished, flush them
at once with only one XDPSQ cleaning (if needed). The main sending
function will be aware of the sending budget and already have all the
info to send the buffers, so it can't fail.
Drivers need to provide 2 inline callbacks to the main sending function:
for cleaning an XDPSQ and for filling descriptors; the library code
takes care of the rest.
Note that unlike the generic code, multi-buffer support is not wrapped
here with unlikely() to not hurt header split setups.

&libeth_xdp_buff is a simple extension over &xdp_buff which has a direct
pointer to the corresponding Rx descriptor (and, luckily, precisely 1 CL
size and 16-byte alignment on x86_64).

Suggested-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com> # xmit logic
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/include/net/libeth/tx.h b/include/net/libeth/tx.h
index 35614f9523f6..3e68d11914f7 100644
--- a/include/net/libeth/tx.h
+++ b/include/net/libeth/tx.h
@@ -1,5 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
-/* Copyright (C) 2024 Intel Corporation */
+/* Copyright (C) 2024-2025 Intel Corporation */
 
 #ifndef __LIBETH_TX_H
 #define __LIBETH_TX_H
@@ -12,11 +12,13 @@
 
 /**
  * enum libeth_sqe_type - type of &libeth_sqe to act on Tx completion
- * @LIBETH_SQE_EMPTY: unused/empty, no action required
+ * @LIBETH_SQE_EMPTY: unused/empty OR XDP_TX frag, no action required
  * @LIBETH_SQE_CTX: context descriptor with empty SQE, no action required
  * @LIBETH_SQE_SLAB: kmalloc-allocated buffer, unmap and kfree()
  * @LIBETH_SQE_FRAG: mapped skb frag, only unmap DMA
  * @LIBETH_SQE_SKB: &sk_buff, unmap and napi_consume_skb(), update stats
+ * @__LIBETH_SQE_XDP_START: separator between skb and XDP types
+ * @LIBETH_SQE_XDP_TX: &skb_shared_info, libeth_xdp_return_buff_bulk(), stats
  */
 enum libeth_sqe_type {
 	LIBETH_SQE_EMPTY		= 0U,
@@ -24,6 +26,9 @@ enum libeth_sqe_type {
 	LIBETH_SQE_SLAB,
 	LIBETH_SQE_FRAG,
 	LIBETH_SQE_SKB,
+
+	__LIBETH_SQE_XDP_START,
+	LIBETH_SQE_XDP_TX		= __LIBETH_SQE_XDP_START,
 };
 
 /**
@@ -32,6 +37,7 @@ enum libeth_sqe_type {
  * @rs_idx: index of the last buffer from the batch this one was sent in
  * @raw: slab buffer to free via kfree()
  * @skb: &sk_buff to consume
+ * @sinfo: skb shared info of an XDP_TX frame
  * @dma: DMA address to unmap
  * @len: length of the mapped region to unmap
  * @nr_frags: number of frags in the frame this buffer belongs to
@@ -46,6 +52,7 @@ struct libeth_sqe {
 	union {
 		void				*raw;
 		struct sk_buff			*skb;
+		struct skb_shared_info		*sinfo;
 	};
 
 	DEFINE_DMA_UNMAP_ADDR(dma);