[PATCH net-next v2] i40e: xsk: use xdp_build_skb_from_zc() for XDP_PASS

[PATCH net-next v2] i40e: xsk: use xdp_build_skb_from_zc() for XDP_PASS

[Chenguang Zhao]

From: Chenguang Zhao <zhaochenguang@kylinos.cn>

Replace the driver-local i40e_construct_skb_zc() with the common
helper xdp_build_skb_from_zc(). On failure, free the xdp buff in
the caller.

xdp_build_skb_from_zc() already calls skb_record_rx_queue() and
eth_type_trans(), so pull the remaining descriptor field setup into
__i40e_process_skb_fields() and use that on the XDP_PASS path.
Briefly restore the Ethernet header around eth_skb_pad() so padding
sees the full L2 frame length.

Signed-off-by: Chenguang Zhao <zhaochenguang@kylinos.cn>
---
v2:
- Extract descriptor field setup into __i40e_process_skb_fields() and
  use it on the XDP_PASS path, so skb_record_rx_queue()/eth_type_trans()
  are not repeated after xdp_build_skb_from_zc().
- Keep a brief __skb_push()/__skb_pull() around eth_skb_pad() so padding
  still sees the full L2 frame length.

v1:
 - https://lore.kernel.org/all/20260724020125.246333-1-chenguang.zhao@linux.dev/
---
 drivers/net/ethernet/intel/i40e/i40e_txrx.c   | 32 ++++++--
 .../ethernet/intel/i40e/i40e_txrx_common.h    |  2 +
 drivers/net/ethernet/intel/i40e/i40e_xsk.c    | 76 +++----------------
 3 files changed, 36 insertions(+), 74 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index ef5e657816f0..87553b14d34a 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -1833,17 +1833,17 @@ static inline void i40e_rx_hash(struct i40e_ring *ring,
 }
 
 /**
- * i40e_process_skb_fields - Populate skb header fields from Rx descriptor
+ * __i40e_process_skb_fields - Populate skb fields from Rx descriptor
  * @rx_ring: rx descriptor ring packet is being transacted on
  * @rx_desc: pointer to the EOP Rx descriptor
  * @skb: pointer to current skb being populated
  *
- * This function checks the ring, descriptor, and packet information in
- * order to populate the hash, checksum, VLAN, protocol, and
- * other fields within the skb.
+ * Populate hash, checksum, PTP timestamp and VLAN from @rx_desc. Does not
+ * call skb_record_rx_queue() or eth_type_trans(); callers that already got
+ * those from xdp_build_skb_from_zc() should use this helper.
  **/
-void i40e_process_skb_fields(struct i40e_ring *rx_ring,
-			     union i40e_rx_desc *rx_desc, struct sk_buff *skb)
+void __i40e_process_skb_fields(struct i40e_ring *rx_ring,
+			       union i40e_rx_desc *rx_desc, struct sk_buff *skb)
 {
 	u64 qword = le64_to_cpu(rx_desc->wb.qword1.status_error_len);
 	u32 rx_status = FIELD_GET(I40E_RXD_QW1_STATUS_MASK, qword);
@@ -1858,14 +1858,30 @@ void i40e_process_skb_fields(struct i40e_ring *rx_ring,
 
 	i40e_rx_checksum(rx_ring->vsi, skb, rx_desc);
 
-	skb_record_rx_queue(skb, rx_ring->queue_index);
-
 	if (qword & BIT(I40E_RX_DESC_STATUS_L2TAG1P_SHIFT)) {
 		__le16 vlan_tag = rx_desc->wb.qword0.lo_dword.l2tag1;
 
 		__vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q),
 				       le16_to_cpu(vlan_tag));
 	}
+}
+
+/**
+ * i40e_process_skb_fields - Populate skb header fields from Rx descriptor
+ * @rx_ring: rx descriptor ring packet is being transacted on
+ * @rx_desc: pointer to the EOP Rx descriptor
+ * @skb: pointer to current skb being populated
+ *
+ * This function checks the ring, descriptor, and packet information in
+ * order to populate the hash, checksum, VLAN, protocol, and
+ * other fields within the skb.
+ **/
+void i40e_process_skb_fields(struct i40e_ring *rx_ring,
+			     union i40e_rx_desc *rx_desc, struct sk_buff *skb)
+{
+	__i40e_process_skb_fields(rx_ring, rx_desc, skb);
+
+	skb_record_rx_queue(skb, rx_ring->queue_index);
 
 	/* modifies the skb - consumes the enet header */
 	skb->protocol = eth_type_trans(skb, rx_ring->netdev);
diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h b/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h
index e26807fd2123..3c52e0e60487 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx_common.h
@@ -9,6 +9,8 @@
 int i40e_xmit_xdp_tx_ring(struct xdp_buff *xdp, struct i40e_ring *xdp_ring);
 void i40e_clean_programming_status(struct i40e_ring *rx_ring, u64 qword0_raw,
 				   u64 qword1);
+void __i40e_process_skb_fields(struct i40e_ring *rx_ring,
+			       union i40e_rx_desc *rx_desc, struct sk_buff *skb);
 void i40e_process_skb_fields(struct i40e_ring *rx_ring,
 			     union i40e_rx_desc *rx_desc, struct sk_buff *skb);
 void i40e_xdp_ring_update_tail(struct i40e_ring *xdp_ring);
diff --git a/drivers/net/ethernet/intel/i40e/i40e_xsk.c b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
index 9f47388eaba5..8741dff82bd1 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_xsk.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_xsk.c
@@ -3,6 +3,7 @@
 
 #include <linux/bpf_trace.h>
 #include <linux/unroll.h>
+#include <net/xdp.h>
 #include <net/xdp_sock_drv.h>
 #include "i40e_txrx_common.h"
 #include "i40e_xsk.h"
@@ -277,70 +278,6 @@ bool i40e_alloc_rx_buffers_zc(struct i40e_ring *rx_ring, u16 count)
 	return count == nb_buffs;
 }
 
-/**
- * i40e_construct_skb_zc - Create skbuff from zero-copy Rx buffer
- * @rx_ring: Rx ring
- * @xdp: xdp_buff
- *
- * This functions allocates a new skb from a zero-copy Rx buffer.
- *
- * Returns the skb, or NULL on failure.
- **/
-static struct sk_buff *i40e_construct_skb_zc(struct i40e_ring *rx_ring,
-					     struct xdp_buff *xdp)
-{
-	unsigned int totalsize = xdp->data_end - xdp->data_meta;
-	unsigned int metasize = xdp->data - xdp->data_meta;
-	struct skb_shared_info *sinfo = NULL;
-	struct sk_buff *skb;
-	u32 nr_frags = 0;
-
-	if (unlikely(xdp_buff_has_frags(xdp))) {
-		sinfo = xdp_get_shared_info_from_buff(xdp);
-		nr_frags = sinfo->nr_frags;
-	}
-	net_prefetch(xdp->data_meta);
-
-	/* allocate a skb to store the frags */
-	skb = napi_alloc_skb(&rx_ring->q_vector->napi, totalsize);
-	if (unlikely(!skb))
-		goto out;
-
-	memcpy(__skb_put(skb, totalsize), xdp->data_meta,
-	       ALIGN(totalsize, sizeof(long)));
-
-	if (metasize) {
-		skb_metadata_set(skb, metasize);
-		__skb_pull(skb, metasize);
-	}
-
-	if (likely(!xdp_buff_has_frags(xdp)))
-		goto out;
-
-	for (int i = 0; i < nr_frags; i++) {
-		struct skb_shared_info *skinfo = skb_shinfo(skb);
-		skb_frag_t *frag = &sinfo->frags[i];
-		struct page *page;
-		void *addr;
-
-		page = dev_alloc_page();
-		if (!page) {
-			dev_kfree_skb(skb);
-			return NULL;
-		}
-		addr = page_to_virt(page);
-
-		memcpy(addr, skb_frag_page(frag), skb_frag_size(frag));
-
-		__skb_fill_page_desc_noacc(skinfo, skinfo->nr_frags++,
-					   addr, 0, skb_frag_size(frag));
-	}
-
-out:
-	xsk_buff_free(xdp);
-	return skb;
-}
-
 static void i40e_handle_xdp_result_zc(struct i40e_ring *rx_ring,
 				      struct xdp_buff *xdp_buff,
 				      union i40e_rx_desc *rx_desc,
@@ -372,21 +309,28 @@ static void i40e_handle_xdp_result_zc(struct i40e_ring *rx_ring,
 		 * BIT(I40E_RXD_QW1_ERROR_SHIFT). This is due to that
 		 * SBP is *not* set in PRT_SBPVSI (default not set).
 		 */
-		skb = i40e_construct_skb_zc(rx_ring, xdp_buff);
+		skb = xdp_build_skb_from_zc(xdp_buff);
 		if (!skb) {
+			xsk_buff_free(xdp_buff);
 			rx_ring->rx_stats.alloc_buff_failed++;
 			*rx_packets = 0;
 			*rx_bytes = 0;
 			return;
 		}
 
+		/* xdp_build_skb_from_zc() already ran eth_type_trans() and
+		 * skb_record_rx_queue(). Restore the Ethernet header only for
+		 * eth_skb_pad(), then pull it back.
+		 */
+		__skb_push(skb, ETH_HLEN);
 		if (eth_skb_pad(skb)) {
 			*rx_packets = 0;
 			*rx_bytes = 0;
 			return;
 		}
+		__skb_pull(skb, ETH_HLEN);
 
-		i40e_process_skb_fields(rx_ring, rx_desc, skb);
+		__i40e_process_skb_fields(rx_ring, rx_desc, skb);
 		napi_gro_receive(&rx_ring->q_vector->napi, skb);
 		return;
 	}
-- 
2.25.1