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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: linux-kernel@vger.kernel.org, Joe Damato Subject: [RFC net-next 08/10] net: bnxt: Implement software USO Date: Tue, 10 Mar 2026 14:21:56 -0700 Message-ID: <20260310212209.2263939-9-joe@dama.to> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260310212209.2263939-1-joe@dama.to> References: <20260310212209.2263939-1-joe@dama.to> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Implement bnxt_sw_udp_gso_xmit() using the core tso_dma_map API and the pre-allocated TX inline buffer for per-segment headers. The xmit path: 1. Calls tso_start() to initialize TSO state 2. Stack-allocates a tso_dma_map and calls tso_dma_map_init() to DMA-map the linear payload and all frags upfront. 3. For each segment: - Copies and patches headers via tso_build_hdr() into the pre-allocated tx_inline_buf (DMA-synced per segment) - Counts payload BDs via tso_dma_map_count() - Emits long BD (header) + ext BD + payload BDs - Payload BDs use tso_dma_map_next() which yields (dma_addr, chunk_len, mapping_len) tuples; mapping_len is set as dma_unmap_len on the first BD of each DMA mapping so the completion path can unmap per-BD Header BDs set dma_unmap_len=3D0 since the inline buffer is pre-allocated and unmapped only at ring teardown. Suggested-by: Jakub Kicinski Signed-off-by: Joe Damato --- drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c | 158 ++++++++++++++++++ 1 file changed, 158 insertions(+) diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c b/drivers/net/et= hernet/broadcom/bnxt/bnxt_gso.c index b296769ee4fe..fe1f791681e1 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_gso.c @@ -19,11 +19,169 @@ #include "bnxt.h" #include "bnxt_gso.h" =20 +static u32 bnxt_sw_gso_lhint(unsigned int len) +{ + if (len <=3D 512) + return TX_BD_FLAGS_LHINT_512_AND_SMALLER; + else if (len <=3D 1023) + return TX_BD_FLAGS_LHINT_512_TO_1023; + else if (len <=3D 2047) + return TX_BD_FLAGS_LHINT_1024_TO_2047; + else + return TX_BD_FLAGS_LHINT_2048_AND_LARGER; +} + netdev_tx_t bnxt_sw_udp_gso_xmit(struct bnxt *bp, struct bnxt_tx_ring_info *txr, struct netdev_queue *txq, struct sk_buff *skb) { + unsigned int hdr_len, mss, num_segs; + struct pci_dev *pdev =3D bp->pdev; + unsigned int total_payload; + struct tso_dma_map map; + u32 vlan_tag_flags =3D 0; + int i, bds_needed; + struct tso_t tso; + u16 cfa_action; + u16 prod; + + hdr_len =3D tso_start(skb, &tso); + mss =3D skb_shinfo(skb)->gso_size; + total_payload =3D skb->len - hdr_len; + num_segs =3D DIV_ROUND_UP(total_payload, mss); + + /* Zero the csum fields so tso_build_hdr will propagate zeroes into + * every segment header. HW csum offload will recompute from scratch. + */ + udp_hdr(skb)->check =3D 0; + if (!tso.ipv6) + ip_hdr(skb)->check =3D 0; + + if (unlikely(num_segs <=3D 1)) + return NETDEV_TX_OK; + + /* Upper bound on the number of descriptors needed. + * + * Each segment uses 1 long BD + 1 ext BD + payload BDs, which is + * at most num_segs + nr_frags (each frag boundary crossing adds at + * most 1 extra BD). + */ + bds_needed =3D 3 * num_segs + skb_shinfo(skb)->nr_frags + 1; + + if (unlikely(bnxt_tx_avail(bp, txr) < bds_needed)) { + netif_txq_try_stop(txq, bnxt_tx_avail(bp, txr), + bp->tx_wake_thresh); + return NETDEV_TX_BUSY; + } + + if (unlikely(tso_dma_map_init(&map, &pdev->dev, skb, hdr_len))) + goto drop; + + cfa_action =3D bnxt_xmit_get_cfa_action(skb); + if (skb_vlan_tag_present(skb)) { + vlan_tag_flags =3D TX_BD_CFA_META_KEY_VLAN | + skb_vlan_tag_get(skb); + if (skb->vlan_proto =3D=3D htons(ETH_P_8021Q)) + vlan_tag_flags |=3D 1 << TX_BD_CFA_META_TPID_SHIFT; + } + + prod =3D txr->tx_prod; + + for (i =3D 0; i < num_segs; i++) { + unsigned int seg_payload =3D min_t(unsigned int, mss, + total_payload - i * mss); + dma_addr_t this_hdr_dma =3D txr->tx_inline_dma + i * hdr_len; + void *this_hdr =3D txr->tx_inline_buf + i * hdr_len; + struct bnxt_sw_tx_bd *tx_buf; + unsigned int mapping_len; + unsigned int chunk_len; + dma_addr_t dma_addr; + struct tx_bd *txbd; + int bd_count; + __le32 csum; + bool last; + u32 flags; + + last =3D (i =3D=3D num_segs - 1); + + tso_build_hdr(skb, this_hdr, &tso, seg_payload, last); + + dma_sync_single_for_device(&pdev->dev, this_hdr_dma, + hdr_len, DMA_TO_DEVICE); + + bd_count =3D tso_dma_map_count(&map, seg_payload); + + tx_buf =3D &txr->tx_buf_ring[RING_TX(bp, prod)]; + txbd =3D &txr->tx_desc_ring[TX_RING(bp, prod)][TX_IDX(prod)]; + + tx_buf->skb =3D skb; + tx_buf->nr_frags =3D bd_count; + tx_buf->is_push =3D 0; + tx_buf->is_ts_pkt =3D 0; + + dma_unmap_addr_set(tx_buf, mapping, this_hdr_dma); + dma_unmap_len_set(tx_buf, len, 0); + + tx_buf->is_sw_gso =3D last ? BNXT_SW_GSO_LAST : BNXT_SW_GSO_MID; + + flags =3D (hdr_len << TX_BD_LEN_SHIFT) | + TX_BD_TYPE_LONG_TX_BD | + TX_BD_CNT(2 + bd_count); + + flags |=3D bnxt_sw_gso_lhint(hdr_len + seg_payload); + + txbd->tx_bd_len_flags_type =3D cpu_to_le32(flags); + txbd->tx_bd_haddr =3D cpu_to_le64(this_hdr_dma); + txbd->tx_bd_opaque =3D SET_TX_OPAQUE(bp, txr, prod, + 2 + bd_count); + + csum =3D cpu_to_le32(TX_BD_FLAGS_TCP_UDP_CHKSUM | + TX_BD_FLAGS_IP_CKSUM); + + prod =3D NEXT_TX(prod); + bnxt_init_ext_bd(bp, txr, prod, csum, + vlan_tag_flags, cfa_action); + + while (tso_dma_map_next(&map, &dma_addr, &chunk_len, + &mapping_len, seg_payload)) { + prod =3D NEXT_TX(prod); + txbd =3D &txr->tx_desc_ring[TX_RING(bp, prod)][TX_IDX(prod)]; + tx_buf =3D &txr->tx_buf_ring[RING_TX(bp, prod)]; + + txbd->tx_bd_haddr =3D cpu_to_le64(dma_addr); + dma_unmap_addr_set(tx_buf, mapping, dma_addr); + dma_unmap_len_set(tx_buf, len, mapping_len); + tx_buf->skb =3D NULL; + tx_buf->is_sw_gso =3D 0; + + flags =3D chunk_len << TX_BD_LEN_SHIFT; + txbd->tx_bd_len_flags_type =3D cpu_to_le32(flags); + txbd->tx_bd_opaque =3D 0; + + seg_payload -=3D chunk_len; + } + + txbd->tx_bd_len_flags_type |=3D + cpu_to_le32(TX_BD_FLAGS_PACKET_END); + + prod =3D NEXT_TX(prod); + } + + netdev_tx_sent_queue(txq, skb->len); + + WRITE_ONCE(txr->tx_prod, prod); + /* Sync BDs before doorbell */ + wmb(); + bnxt_db_write(bp, &txr->tx_db, prod); + + if (unlikely(bnxt_tx_avail(bp, txr) <=3D bp->tx_wake_thresh)) + netif_txq_try_stop(txq, bnxt_tx_avail(bp, txr), + bp->tx_wake_thresh); + + return NETDEV_TX_OK; + +drop: dev_kfree_skb_any(skb); dev_core_stats_tx_dropped_inc(bp->dev); return NETDEV_TX_OK; --=20 2.52.0