[PATCH v3 next 5/7] net/vmxnet3: limit number of TXDs used for TSO packet

[Ronak Doshi <doshir@vmware.com>]

Currently, vmxnet3 does not have a limit on number of descriptors
used for a TSO packet. However, with UPT, for hardware performance
reasons, this patch limits the number of transmit descriptors to 24
for a TSO packet.

Signed-off-by: Ronak Doshi <doshir@vmware.com>
Acked-by: Jochen Behrens <jbehrens@vmware.com>
---
 drivers/net/vmxnet3/base/vmxnet3_defs.h |  2 ++
 drivers/net/vmxnet3/vmxnet3_rxtx.c      | 18 ++++++++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/drivers/net/vmxnet3/base/vmxnet3_defs.h b/drivers/net/vmxnet3/base/vmxnet3_defs.h
index d8cc295b08..24c235876e 100644
--- a/drivers/net/vmxnet3/base/vmxnet3_defs.h
+++ b/drivers/net/vmxnet3/base/vmxnet3_defs.h
@@ -419,6 +419,8 @@ typedef union Vmxnet3_GenericDesc {
 
 /* max # of tx descs for a non-tso pkt */
 #define VMXNET3_MAX_TXD_PER_PKT 16
+/* max # of tx descs for a tso pkt */
+#define VMXNET3_MAX_TSO_TXD_PER_PKT 24
 
 /* Max size of a single rx buffer */
 #define VMXNET3_MAX_RX_BUF_SIZE  ((1 << 14) - 1)
diff --git a/drivers/net/vmxnet3/vmxnet3_rxtx.c b/drivers/net/vmxnet3/vmxnet3_rxtx.c
index e31878ecab..7bbae4177e 100644
--- a/drivers/net/vmxnet3/vmxnet3_rxtx.c
+++ b/drivers/net/vmxnet3/vmxnet3_rxtx.c
@@ -364,6 +364,14 @@ vmxnet3_prep_pkts(__rte_unused void *tx_queue, struct rte_mbuf **tx_pkts,
 			rte_errno = EINVAL;
 			return i;
 		}
+		/* TSO packet cannot occupy more than
+		 * VMXNET3_MAX_TSO_TXD_PER_PKT TX descriptors.
+		 */
+		if ((ol_flags & RTE_MBUF_F_TX_TCP_SEG) != 0 &&
+				m->nb_segs > VMXNET3_MAX_TSO_TXD_PER_PKT) {
+			rte_errno = EINVAL;
+			return i;
+		}
 
 		/* check that only supported TX offloads are requested. */
 		if ((ol_flags & VMXNET3_TX_OFFLOAD_NOTSUP_MASK) != 0 ||
@@ -444,10 +452,12 @@ vmxnet3_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 			continue;
 		}
 
-		/* Drop non-TSO packet that is excessively fragmented */
-		if (unlikely(!tso && count > VMXNET3_MAX_TXD_PER_PKT)) {
-			PMD_TX_LOG(ERR, "Non-TSO packet cannot occupy more than %d tx "
-				   "descriptors. Packet dropped.", VMXNET3_MAX_TXD_PER_PKT);
+		/* Drop non-TSO or TSO packet that is excessively fragmented */
+		if (unlikely((!tso && count > VMXNET3_MAX_TXD_PER_PKT) ||
+			     (tso && count > VMXNET3_MAX_TSO_TXD_PER_PKT))) {
+			PMD_TX_LOG(ERR, "Non-TSO or TSO packet cannot occupy more than "
+				   "%d or %d tx descriptors respectively. Packet dropped.",
+				   VMXNET3_MAX_TXD_PER_PKT, VMXNET3_MAX_TSO_TXD_PER_PKT);
 			txq->stats.drop_too_many_segs++;
 			txq->stats.drop_total++;
 			rte_pktmbuf_free(txm);
-- 
2.11.0