From 120ae502af169310aa53359d4faf2494dcee6927 Mon Sep 17 00:00:00 2001
From: Tallapragada Kalyan <quic_ktallapr@quicinc.com>
Date: Thu, 9 Jun 2022 09:32:38 +0530
Subject: [PATCH 267/281] net: set skb's fast_xmit flag in dev_fast_xmit API

set skb's fast_xmit flag in dev_fast_xmit API for linear packets
WiFi tx path can avoid some overhead due to checks based on this flag

Change-Id: Ied29f9d615d0cf48dd9dcd7fcf0fb210eb259a8f
Signed-off-by: Tallapragada Kalyan <quic_ktallapr@quicinc.com>
---
 include/linux/skbuff.h | 2 ++
 net/core/dev.c         | 4 ++++
 2 files changed, 6 insertions(+)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -990,6 +990,8 @@ struct sk_buff {
 	__u8			csum_not_inet:1;
 #endif
 	__u8			fast_forwarded:1;
+	/* Linear packets processed by dev_fast_xmit() */
+	__u8			fast_xmit:1;
 	/* 1 or 3 bit hole */
 
 #if defined(CONFIG_NET_SCHED) || defined(CONFIG_NET_XGRESS)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4305,6 +4305,144 @@ struct netdev_queue *netdev_core_pick_tx
 }
 
 /**
+ *	dev_fast_xmit_vp - fast xmit the skb to a PPE virtual port
+ *	@skb:buffer to transmit
+ *	@dev: the device to be transmited to
+ *	sucessful return true
+ *	failed return false
+ */
+bool dev_fast_xmit_vp(struct sk_buff *skb,
+		struct net_device *dev)
+{
+	struct netdev_queue *txq;
+	int cpu;
+	netdev_tx_t rc;
+
+	if (unlikely(!(dev->flags & IFF_UP))) {
+		return false;
+	}
+
+	if (unlikely(skb_is_nonlinear(skb))) {
+		return false;
+	}
+
+	rcu_read_lock_bh();
+	cpu = smp_processor_id();
+
+	/*
+	 * TODO: Skip this altogether and eventually move this call to ppe_vp
+	 * this would avoid multiple function calls when giving packet to wifi VAP.
+	 */
+	txq = netdev_core_pick_tx(dev, skb, NULL);
+
+	if (likely(txq->xmit_lock_owner != cpu)) {
+#define FAST_VP_HARD_TX_LOCK(txq, cpu) {	\
+		__netif_tx_lock(txq, cpu);		\
+}
+
+#define FAST_VP_HARD_TX_UNLOCK(txq) {		\
+		__netif_tx_unlock(txq);			\
+}
+		skb->fast_xmit = 1;
+		FAST_VP_HARD_TX_LOCK(txq, cpu);
+		if (likely(!netif_xmit_stopped(txq))) {
+			rc = netdev_start_xmit(skb, dev, txq, 0);
+			if (unlikely(!dev_xmit_complete(rc))) {
+				FAST_VP_HARD_TX_UNLOCK(txq);
+				goto q_xmit;
+			}
+			FAST_VP_HARD_TX_UNLOCK(txq);
+			rcu_read_unlock_bh();
+			return true;
+		}
+		FAST_VP_HARD_TX_UNLOCK(txq);
+	}
+q_xmit:
+	skb->fast_xmit = 0;
+	rcu_read_unlock_bh();
+	return false;
+}
+EXPORT_SYMBOL(dev_fast_xmit_vp);
+
+/**
+ *	dev_fast_xmit - fast xmit the skb
+ *	@skb:buffer to transmit
+ *	@dev: the device to be transmited to
+ *	@features: the skb features could bed used
+ *	sucessful return true
+ *	failed return false
+ */
+bool dev_fast_xmit(struct sk_buff *skb,
+		struct net_device *dev,
+		netdev_features_t features)
+{
+	struct netdev_queue *txq;
+	int cpu;
+	netdev_tx_t rc;
+
+	/* the fast_xmit flag will avoid multiple checks in wifi xmit path */
+	if (likely(!skb_is_nonlinear(skb)))
+		skb->fast_xmit = 1;
+
+	if (unlikely(!(dev->flags & IFF_UP))) {
+		return false;
+	}
+
+	if (unlikely(skb_needs_linearize(skb, features))) {
+		return false;
+	}
+
+	rcu_read_lock_bh();
+	cpu = smp_processor_id();
+
+	/* If device don't need the dst, release it now, otherwise make sure
+	 * the refcount increased.
+	 */
+	if (likely(dev->priv_flags & IFF_XMIT_DST_RELEASE)) {
+		skb_dst_drop(skb);
+	} else {
+		skb_dst_force(skb);
+	}
+
+	txq = netdev_core_pick_tx(dev, skb, NULL);
+
+	if (likely(txq->xmit_lock_owner != cpu)) {
+#define FAST_HARD_TX_LOCK(features, txq, cpu) {		\
+	if ((features & NETIF_F_LLTX) == 0) {		\
+		__netif_tx_lock(txq, cpu);		\
+	} else {					\
+		__netif_tx_acquire(txq);		\
+	}						\
+}
+
+#define FAST_HARD_TX_UNLOCK(features, txq) {		\
+	if ((features & NETIF_F_LLTX) == 0) {		\
+		__netif_tx_unlock(txq);			\
+	} else {					\
+		__netif_tx_release(txq);		\
+	}						\
+}
+		netdev_features_t dev_features = dev->features;
+		FAST_HARD_TX_LOCK(dev_features, txq, cpu);
+		if (likely(!netif_xmit_stopped(txq))) {
+			rc = netdev_start_xmit(skb, dev, txq, 0);
+			if (unlikely(!dev_xmit_complete(rc))) {
+				FAST_HARD_TX_UNLOCK(dev_features, txq);
+				goto fail;
+			}
+			FAST_HARD_TX_UNLOCK(dev_features, txq);
+			rcu_read_unlock_bh();
+			return true;
+		}
+		FAST_HARD_TX_UNLOCK(dev_features, txq);
+	}
+fail:
+	rcu_read_unlock_bh();
+	return false;
+}
+EXPORT_SYMBOL(dev_fast_xmit);
+
+/**
  * __dev_queue_xmit() - transmit a buffer
  * @skb:	buffer to transmit
  * @sb_dev:	suboordinate device used for L2 forwarding offload