linux-kernel - [PATCH net-next 6/8] vmxnet3: limit number of TXDs used for TSO packet

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Date:   Fri, 27 May 2022 18:17:56 -0700
From:   Ronak Doshi <doshir@...are.com>
To:     <netdev@...r.kernel.org>
CC:     Ronak Doshi <doshir@...are.com>,
        VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: [PATCH net-next 6/8] vmxnet3: limit number of TXDs used for TSO packet

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@...are.com>
Acked-by: Guolin Yang <gyang@...are.com>
---
 drivers/net/vmxnet3/vmxnet3_defs.h |  2 ++
 drivers/net/vmxnet3/vmxnet3_drv.c  | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/net/vmxnet3/vmxnet3_defs.h b/drivers/net/vmxnet3/vmxnet3_defs.h
index 415e4c9993ef..cb9dc72f2b3d 100644
--- a/drivers/net/vmxnet3/vmxnet3_defs.h
+++ b/drivers/net/vmxnet3/vmxnet3_defs.h
@@ -400,6 +400,8 @@ 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_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
index 2ba263966989..6e013ae0b5ea 100644
--- a/drivers/net/vmxnet3/vmxnet3_drv.c
+++ b/drivers/net/vmxnet3/vmxnet3_drv.c
@@ -1061,6 +1061,23 @@ vmxnet3_tq_xmit(struct sk_buff *skb, struct vmxnet3_tx_queue *tq,
 			}
 			tq->stats.copy_skb_header++;
 		}
+		if (unlikely(count > VMXNET3_MAX_TSO_TXD_PER_PKT)) {
+			/* tso pkts must not use more than
+			 * VMXNET3_MAX_TSO_TXD_PER_PKT entries
+			 */
+			if (skb_linearize(skb) != 0) {
+				tq->stats.drop_too_many_frags++;
+				goto drop_pkt;
+			}
+			tq->stats.linearized++;
+
+			/* recalculate the # of descriptors to use */
+			count = VMXNET3_TXD_NEEDED(skb_headlen(skb)) + 1;
+			if (unlikely(count > VMXNET3_MAX_TSO_TXD_PER_PKT)) {
+				tq->stats.drop_too_many_frags++;
+				goto drop_pkt;
+			}
+		}
 		if (skb->encapsulation) {
 			vmxnet3_prepare_inner_tso(skb, &ctx);
 		} else {
-- 
2.11.0