On Sat 1 Feb 2025, 10:03 Ariel Otilibili, <ariel.otilibili@6wind.com> wrote:
Both legs of the loop share the same logic: the common parts are about
reserving and filling both address and length into the description.

This is moved into reserve_and_fill().

Bugzilla ID: 1440
Suggested-by: Maryam Tahhan <mtahhan@redhat.com>
Signed-off-by: Ariel Otilibili <ariel.otilibili@6wind.com>
---
 drivers/net/af_xdp/rte_eth_af_xdp.c | 62 ++++++++++++++++-------------
 1 file changed, 34 insertions(+), 28 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 092bcb73aa0a..840a12dbf508 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -536,6 +536,31 @@ kick_tx(struct pkt_tx_queue *txq, struct xsk_ring_cons *cq)
                }
 }

+static inline struct xdp_desc *
+reserve_and_fill(struct pkt_tx_queue *txq, struct rte_mbuf *mbuf,
+                struct xsk_umem_info *umem)
+{
+       struct xdp_desc *desc = NULL;
+       uint32_t *idx_tx = NULL;
+       uint64_t addr, offset;
+
+       if (!xsk_ring_prod__reserve(&txq->tx, 1, idx_tx))
+               goto out;
+
+       desc = xsk_ring_prod__tx_desc(&txq->tx, *idx_tx);
+       desc->len = mbuf->pkt_len;
+
+       addr = (uint64_t)mbuf - (uint64_t)umem->buffer
+               - umem->mb_pool->header_size;
+       offset = rte_pktmbuf_mtod(mbuf, uint64_t) - (uint64_t)mbuf
+               + umem->mb_pool->header_size;
+       offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
+       desc->addr = addr | offset;
+
+out:
+       return desc;
+}
+
 #if defined(XDP_UMEM_UNALIGNED_CHUNK_FLAG)
 static uint16_t
 af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
@@ -545,10 +570,8 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
        struct rte_mbuf *mbuf;
        unsigned long tx_bytes = 0;
        int i;
-       uint32_t idx_tx;
        uint16_t count = 0;
        struct xdp_desc *desc;
-       uint64_t addr, offset;
        struct xsk_ring_cons *cq = &txq->pair->cq;
        uint32_t free_thresh = cq->size >> 1;

@@ -559,21 +582,12 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
                mbuf = bufs[i];

                if (mbuf->pool == umem->mb_pool) {
-                       if (!xsk_ring_prod__reserve(&txq->tx, 1, &idx_tx)) {
+                       if (!(desc = reserve_and_fill(txq, mbuf, umem))) {
                                kick_tx(txq, cq);
-                               if (!xsk_ring_prod__reserve(&txq->tx, 1,
-                                                           &idx_tx))
+                               if (!(desc = reserve_and_fill(txq, mbuf, umem)))
                                        goto out;
                        }
-                       desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
-                       desc->len = mbuf->pkt_len;
-                       addr = (uint64_t)mbuf - (uint64_t)umem->buffer -
-                                       umem->mb_pool->header_size;
-                       offset = rte_pktmbuf_mtod(mbuf, uint64_t) -
-                                       (uint64_t)mbuf +
-                                       umem->mb_pool->header_size;
-                       offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
-                       desc->addr = addr | offset;
+
                        tx_bytes += desc->len;
                        count++;
                } else {
@@ -584,26 +598,18 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
                        if (local_mbuf == NULL)
                                goto out;

-                       if (!xsk_ring_prod__reserve(&txq->tx, 1, &idx_tx)) {
+                       if (!(desc = reserve_and_fill(txq, local_mbuf, umem))) {
                                rte_pktmbuf_free(local_mbuf);
                                goto out;
                        }

-                       desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
-                       desc->len = mbuf->pkt_len;
-

So I think i spotted one issue, you might need override desc->len after the call to the reserve_and_fill function so as it's not taken supposed to be from local_mbuf here.

-                       addr = (uint64_t)local_mbuf - (uint64_t)umem->buffer -
-                                       umem->mb_pool->header_size;
-                       offset = rte_pktmbuf_mtod(local_mbuf, uint64_t) -
-                                       (uint64_t)local_mbuf +
-                                       umem->mb_pool->header_size;
-                       pkt = xsk_umem__get_data(umem->buffer, addr + offset);
-                       offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
-                       desc->addr = addr | offset;
+                       pkt = xsk_umem__get_data(umem->buffer,
+                                                (desc->addr & ~0xFFF)
+                                                + (desc->addr & 0xFFF));

Would prefer to move this pkt assignment to reserve_and_fill()
What if we passed a void **ppkt to reserve_and_fill()  then kept the original logic just wrapped in a NULL check?

 if (ppkt) {
      *ppkt = xsk_umem__get_data(umem->buffer, addr + offset);
    }


Before the offset and desc->addr 
    offset = offset << XSK_UNALIGNED_BUF_OFFSET_SHIFT;
    desc->addr = addr | offset;

WDYT? 

                        rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
-                                       desc->len);
-                       tx_bytes += desc->len;
+                                  desc->len);
                        rte_pktmbuf_free(mbuf);
+                       tx_bytes += desc->len;
                        count++;
                }
        }
--
2.30.2