[PATCH 23.11 1/3] net/gve: send whole packet when mbuf is large

[Joshua Washington]

Before this patch, only one descriptor would be written per mbuf in a
packet. In cases like TSO, it is possible for a single mbuf to have more
bytes than GVE_MAX_TX_BUF_SIZE_DQO. As such, instead of simply
truncating the data down to this size, the driver should actually write
descriptors for the rest of the buffers in the mbuf segment.

To that effect, the number of descriptors needed to send a packet must
be corrected to account for the potential additional descriptors.

Fixes: 4022f9999f56 ("net/gve: support basic Tx data path for DQO")
Cc: stable at dpdk.org

Signed-off-by: Joshua Washington <joshwash at google.com>
Reviewed-by: Ankit Garg <nktgrg at google.com>
---
 .mailmap                     |  1 +
 drivers/net/gve/gve_tx_dqo.c | 53 ++++++++++++++++++++++++++----------
 2 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/.mailmap b/.mailmap
index 96b7809f89..eb6a3afa44 100644
--- a/.mailmap
+++ b/.mailmap
@@ -119,6 +119,7 @@ Andy Green <andy at warmcat.com>
 Andy Moreton <andy.moreton at amd.com> <amoreton at xilinx.com> <amoreton at solarflare.com>
 Andy Pei <andy.pei at intel.com>
 Anirudh Venkataramanan <anirudh.venkataramanan at intel.com>
+Ankit Garg <nktgrg at google.com>
 Ankur Dwivedi <adwivedi at marvell.com> <ankur.dwivedi at caviumnetworks.com> <ankur.dwivedi at cavium.com>
 Anna Lukin <annal at silicom.co.il>
 Anoob Joseph <anoobj at marvell.com> <anoob.joseph at caviumnetworks.com>
diff --git a/drivers/net/gve/gve_tx_dqo.c b/drivers/net/gve/gve_tx_dqo.c
index 95a02bab17..a4ba8c3536 100644
--- a/drivers/net/gve/gve_tx_dqo.c
+++ b/drivers/net/gve/gve_tx_dqo.c
@@ -74,6 +74,19 @@ gve_tx_clean_dqo(struct gve_tx_queue *txq)
 	txq->complq_tail = next;
 }
 
+static uint16_t
+gve_tx_pkt_nb_data_descs(struct rte_mbuf *tx_pkt)
+{
+	int nb_descs = 0;
+
+	while (tx_pkt) {
+		nb_descs += (GVE_TX_MAX_BUF_SIZE_DQO - 1 + tx_pkt->data_len) /
+			GVE_TX_MAX_BUF_SIZE_DQO;
+		tx_pkt = tx_pkt->next;
+	}
+	return nb_descs;
+}
+
 uint16_t
 gve_tx_burst_dqo(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 {
@@ -88,7 +101,7 @@ gve_tx_burst_dqo(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 	const char *reason;
 	uint16_t nb_tx = 0;
 	uint64_t ol_flags;
-	uint16_t nb_used;
+	uint16_t nb_descs;
 	uint16_t tx_id;
 	uint16_t sw_id;
 	uint64_t bytes;
@@ -122,11 +135,14 @@ gve_tx_burst_dqo(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 		}
 
 		ol_flags = tx_pkt->ol_flags;
-		nb_used = tx_pkt->nb_segs;
 		first_sw_id = sw_id;
 
 		csum = !!(ol_flags & GVE_TX_CKSUM_OFFLOAD_MASK_DQO);
 
+		nb_descs = gve_tx_pkt_nb_data_descs(tx_pkt);
+		if (txq->nb_free < nb_descs)
+			break;
+
 		do {
 			if (sw_ring[sw_id] != NULL)
 				PMD_DRV_LOG(DEBUG, "Overwriting an entry in sw_ring");
@@ -135,22 +151,29 @@ gve_tx_burst_dqo(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 			if (!tx_pkt->data_len)
 				goto finish_mbuf;
 
-			txd = &txr[tx_id];
 			sw_ring[sw_id] = tx_pkt;
 
-			/* fill Tx descriptor */
-			txd->pkt.buf_addr = rte_cpu_to_le_64(rte_mbuf_data_iova(tx_pkt));
-			txd->pkt.dtype = GVE_TX_PKT_DESC_DTYPE_DQO;
-			txd->pkt.compl_tag = rte_cpu_to_le_16(first_sw_id);
-			txd->pkt.buf_size = RTE_MIN(tx_pkt->data_len, GVE_TX_MAX_BUF_SIZE_DQO);
-			txd->pkt.end_of_packet = 0;
-			txd->pkt.checksum_offload_enable = csum;
+			/* fill Tx descriptors */
+			int mbuf_offset = 0;
+			while (mbuf_offset < tx_pkt->data_len) {
+				uint64_t buf_addr = rte_mbuf_data_iova(tx_pkt) +
+					mbuf_offset;
+
+				txd = &txr[tx_id];
+				txd->pkt.buf_addr = rte_cpu_to_le_64(buf_addr);
+				txd->pkt.compl_tag = rte_cpu_to_le_16(first_sw_id);
+				txd->pkt.dtype = GVE_TX_PKT_DESC_DTYPE_DQO;
+				txd->pkt.buf_size = RTE_MIN(tx_pkt->data_len - mbuf_offset,
+							    GVE_TX_MAX_BUF_SIZE_DQO);
+				txd->pkt.end_of_packet = 0;
+				txd->pkt.checksum_offload_enable = csum;
+
+				mbuf_offset += txd->pkt.buf_size;
+				tx_id = (tx_id + 1) & mask;
+			}
 
-			/* size of desc_ring and sw_ring could be different */
-			tx_id = (tx_id + 1) & mask;
 finish_mbuf:
 			sw_id = (sw_id + 1) & sw_mask;
-
 			bytes += tx_pkt->data_len;
 			tx_pkt = tx_pkt->next;
 		} while (tx_pkt);
@@ -159,8 +182,8 @@ gve_tx_burst_dqo(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 		txd = &txr[(tx_id - 1) & mask];
 		txd->pkt.end_of_packet = 1;
 
-		txq->nb_free -= nb_used;
-		txq->nb_used += nb_used;
+		txq->nb_free -= nb_descs;
+		txq->nb_used += nb_descs;
 	}
 
 	/* update the tail pointer if any packets were processed */
-- 
2.52.0.351.gbe84eed79e-goog