Subject: [PATCH net-next v3 1/3] netvsc: transparent VF management

From: Stephen Hemminger <[email-masked]>
Date: Tue, 1 Aug 2017 19:58:53 -0700

This patch implements transparent fail over from synthetic NIC to
SR-IOV virtual function NIC in Hyper-V environment. It is a better
alternative to using bonding as is done now. Instead, the receive and
transmit fail over is done internally inside the driver.

Using bonding driver has lots of issues because it depends on the
script being run early enough in the boot process and with sufficient
information to make the association. This patch moves all that
functionality into the kernel.

Signed-off-by: Stephen Hemminger <[email-masked]>
---
v3 - fix merge conflict (due to comment change) 

 drivers/net/hyperv/hyperv_net.h |  12 ++
 drivers/net/hyperv/netvsc_drv.c | 419 +++++++++++++++++++++++++++++++---------
 2 files changed, 342 insertions(+), 89 deletions(-)

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index f2cef5aaed1f..c701b059c5ac 100644
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -680,6 +680,15 @@ struct netvsc_ethtool_stats {
 	unsigned long tx_busy;
 };
 
+struct netvsc_vf_pcpu_stats {
+	u64     rx_packets;
+	u64     rx_bytes;
+	u64     tx_packets;
+	u64     tx_bytes;
+	struct u64_stats_sync   syncp;
+	u32	tx_dropped;
+};
+
 struct netvsc_reconfig {
 	struct list_head list;
 	u32 event;
@@ -713,6 +722,9 @@ struct net_device_context {
 
 	/* State to manage the associated VF interface. */
 	struct net_device __rcu *vf_netdev;
+	struct netvsc_vf_pcpu_stats __percpu *vf_stats;
+	struct work_struct vf_takeover;
+	struct work_struct vf_notify;
 
 	/* 1: allocated, serial number is valid. 0: not allocated */
 	u32 vf_alloc;
diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 9453eef6d09f..c71728d82049 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -34,6 +34,7 @@
 #include <linux/in.h>
 #include <linux/slab.h>
 #include <linux/rtnetlink.h>
+#include <linux/netpoll.h>
 
 #include <net/arp.h>
 #include <net/route.h>
@@ -71,6 +72,7 @@ static void netvsc_set_multicast_list(struct net_device *net)
 static int netvsc_open(struct net_device *net)
 {
 	struct net_device_context *ndev_ctx = netdev_priv(net);
+	struct net_device *vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev);
 	struct netvsc_device *nvdev = rtnl_dereference(ndev_ctx->nvdev);
 	struct rndis_device *rdev;
 	int ret = 0;
@@ -87,15 +89,29 @@ static int netvsc_open(struct net_device *net)
 	netif_tx_wake_all_queues(net);
 
 	rdev = nvdev->extension;
-	if (!rdev->link_state && !ndev_ctx->datapath)
+
+	if (!rdev->link_state)
 		netif_carrier_on(net);
 
-	return ret;
+	if (vf_netdev) {
+		/* Setting synthetic device up transparently sets
+		 * slave as up. If open fails, then slave will be
+		 * still be offline (and not used).
+		 */
+		ret = dev_open(vf_netdev);
+		if (ret)
+			netdev_warn(net,
+				    "unable to open slave: %s: %d\n",
+				    vf_netdev->name, ret);
+	}
+	return 0;
 }
 
 static int netvsc_close(struct net_device *net)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(net);
+	struct net_device *vf_netdev
+		= rtnl_dereference(net_device_ctx->vf_netdev);
 	struct netvsc_device *nvdev = rtnl_dereference(net_device_ctx->nvdev);
 	int ret;
 	u32 aread, i, msec = 10, retry = 0, retry_max = 20;
@@ -141,6 +157,9 @@ static int netvsc_close(struct net_device *net)
 		ret = -ETIMEDOUT;
 	}
 
+	if (vf_netdev)
+		dev_close(vf_netdev);
+
 	return ret;
 }
 
@@ -224,13 +243,11 @@ static inline int netvsc_get_tx_queue(struct net_device *ndev,
  *
  * TODO support XPS - but get_xps_queue not exported
  */
-static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
-			void *accel_priv, select_queue_fallback_t fallback)
+static u16 netvsc_pick_tx(struct net_device *ndev, struct sk_buff *skb)
 {
-	unsigned int num_tx_queues = ndev->real_num_tx_queues;
 	int q_idx = sk_tx_queue_get(skb->sk);
 
-	if (q_idx < 0 || skb->ooo_okay) {
+	if (q_idx < 0 || skb->ooo_okay || q_idx >= ndev->real_num_tx_queues) {
 		/* If forwarding a packet, we use the recorded queue when
 		 * available for better cache locality.
 		 */
@@ -240,12 +257,33 @@ static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
 			q_idx = netvsc_get_tx_queue(ndev, skb, q_idx);
 	}
 
-	while (unlikely(q_idx >= num_tx_queues))
-		q_idx -= num_tx_queues;
-
 	return q_idx;
 }
 
+static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
+			       void *accel_priv,
+			       select_queue_fallback_t fallback)
+{
+	struct net_device_context *ndc = netdev_priv(ndev);
+	struct net_device *vf_netdev;
+	u16 txq;
+
+	rcu_read_lock();
+	vf_netdev = rcu_dereference(ndc->vf_netdev);
+	if (vf_netdev) {
+		txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : 0;
+		qdisc_skb_cb(skb)->slave_dev_queue_mapping = skb->queue_mapping;
+	} else {
+		txq = netvsc_pick_tx(ndev, skb);
+	}
+	rcu_read_unlock();
+
+	while (unlikely(txq >= ndev->real_num_tx_queues))
+		txq -= ndev->real_num_tx_queues;
+
+	return txq;
+}
+
 static u32 fill_pg_buf(struct page *page, u32 offset, u32 len,
 			struct hv_page_buffer *pb)
 {
@@ -367,6 +405,33 @@ static u32 net_checksum_info(struct sk_buff *skb)
 	return TRANSPORT_INFO_NOT_IP;
 }
 
+/* Send skb on the slave VF device. */
+static int netvsc_vf_xmit(struct net_device *net, struct net_device *vf_netdev,
+			  struct sk_buff *skb)
+{
+	struct net_device_context *ndev_ctx = netdev_priv(net);
+	unsigned int len = skb->len;
+	int rc;
+
+	skb->dev = vf_netdev;
+	skb->queue_mapping = qdisc_skb_cb(skb)->slave_dev_queue_mapping;
+
+	rc = dev_queue_xmit(skb);
+	if (likely(rc == NET_XMIT_SUCCESS || rc == NET_XMIT_CN)) {
+		struct netvsc_vf_pcpu_stats *pcpu_stats
+			= this_cpu_ptr(ndev_ctx->vf_stats);
+
+		u64_stats_update_begin(&pcpu_stats->syncp);
+		pcpu_stats->tx_packets++;
+		pcpu_stats->tx_bytes += len;
+		u64_stats_update_end(&pcpu_stats->syncp);
+	} else {
+		this_cpu_inc(ndev_ctx->vf_stats->tx_dropped);
+	}
+
+	return rc;
+}
+
 static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(net);
@@ -375,11 +440,20 @@ static int netvsc_start_xmit(struct sk_buff *skb, struct net_device *net)
 	unsigned int num_data_pgs;
 	struct rndis_message *rndis_msg;
 	struct rndis_packet *rndis_pkt;
+	struct net_device *vf_netdev;
 	u32 rndis_msg_size;
 	struct rndis_per_packet_info *ppi;
 	u32 hash;
 	struct hv_page_buffer pb[MAX_PAGE_BUFFER_COUNT];
 
+	/* if VF is present and up then redirect packets
+	 * already called with rcu_read_lock_bh
+	 */
+	vf_netdev = rcu_dereference_bh(net_device_ctx->vf_netdev);
+	if (vf_netdev && netif_running(vf_netdev) &&
+	    !netpoll_tx_running(net))
+		return netvsc_vf_xmit(net, vf_netdev, skb);
+
 	/* We will atmost need two pages to describe the rndis
 	 * header. We can only transmit MAX_PAGE_BUFFER_COUNT number
 	 * of pages in a single packet. If skb is scattered around
@@ -658,29 +732,18 @@ int netvsc_recv_callback(struct net_device *net,
 	struct netvsc_device *net_device;
 	u16 q_idx = channel->offermsg.offer.sub_channel_index;
 	struct netvsc_channel *nvchan;
-	struct net_device *vf_netdev;
 	struct sk_buff *skb;
 	struct netvsc_stats *rx_stats;
 
 	if (net->reg_state != NETREG_REGISTERED)
 		return NVSP_STAT_FAIL;
 
-	/*
-	 * If necessary, inject this packet into the VF interface.
-	 * On Hyper-V, multicast and brodcast packets are only delivered
-	 * to the synthetic interface (after subjecting these to
-	 * policy filters on the host). Deliver these via the VF
-	 * interface in the guest.
-	 */
 	rcu_read_lock();
 	net_device = rcu_dereference(net_device_ctx->nvdev);
 	if (unlikely(!net_device))
 		goto drop;
 
 	nvchan = &net_device->chan_table[q_idx];
-	vf_netdev = rcu_dereference(net_device_ctx->vf_netdev);
-	if (vf_netdev && (vf_netdev->flags & IFF_UP))
-		net = vf_netdev;
 
 	/* Allocate a skb - TODO direct I/O to pages? */
 	skb = netvsc_alloc_recv_skb(net, &nvchan->napi,
@@ -692,8 +755,7 @@ int netvsc_recv_callback(struct net_device *net,
 		return NVSP_STAT_FAIL;
 	}
 
-	if (net != vf_netdev)
-		skb_record_rx_queue(skb, q_idx);
+	skb_record_rx_queue(skb, q_idx);
 
 	/*
 	 * Even if injecting the packet, record the statistics
@@ -853,6 +915,7 @@ static int netvsc_set_link_ksettings(struct net_device *dev,
 static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 {
 	struct net_device_context *ndevctx = netdev_priv(ndev);
+	struct net_device *vf_netdev = rtnl_dereference(ndevctx->vf_netdev);
 	struct netvsc_device *nvdev = rtnl_dereference(ndevctx->nvdev);
 	struct hv_device *hdev = ndevctx->device_ctx;
 	int orig_mtu = ndev->mtu;
@@ -863,6 +926,13 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 	if (!nvdev || nvdev->destroy)
 		return -ENODEV;
 
+	/* Change MTU of underlying VF netdev first. */
+	if (vf_netdev) {
+		ret = dev_set_mtu(vf_netdev, mtu);
+		if (ret)
+			return ret;
+	}
+
 	netif_device_detach(ndev);
 	was_opened = rndis_filter_opened(nvdev);
 	if (was_opened)
@@ -883,6 +953,9 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 		/* Attempt rollback to original MTU */
 		ndev->mtu = orig_mtu;
 		rndis_filter_device_add(hdev, &device_info);
+
+		if (vf_netdev)
+			dev_set_mtu(vf_netdev, orig_mtu);
 	}
 
 	if (was_opened)
@@ -896,16 +969,56 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 	return ret;
 }
 
+static void netvsc_get_vf_stats(struct net_device *net,
+				struct netvsc_vf_pcpu_stats *tot)
+{
+	struct net_device_context *ndev_ctx = netdev_priv(net);
+	int i;
+
+	memset(tot, 0, sizeof(*tot));
+
+	for_each_possible_cpu(i) {
+		const struct netvsc_vf_pcpu_stats *stats
+			= per_cpu_ptr(ndev_ctx->vf_stats, i);
+		u64 rx_packets, rx_bytes, tx_packets, tx_bytes;
+		unsigned int start;
+
+		do {
+			start = u64_stats_fetch_begin_irq(&stats->syncp);
+			rx_packets = stats->rx_packets;
+			tx_packets = stats->tx_packets;
+			rx_bytes = stats->rx_bytes;
+			tx_bytes = stats->tx_bytes;
+		} while (u64_stats_fetch_retry_irq(&stats->syncp, start));
+
+		tot->rx_packets += rx_packets;
+		tot->tx_packets += tx_packets;
+		tot->rx_bytes   += rx_bytes;
+		tot->tx_bytes   += tx_bytes;
+		tot->tx_dropped += stats->tx_dropped;
+	}
+}
+
 static void netvsc_get_stats64(struct net_device *net,
 			       struct rtnl_link_stats64 *t)
 {
 	struct net_device_context *ndev_ctx = netdev_priv(net);
 	struct netvsc_device *nvdev = rcu_dereference_rtnl(ndev_ctx->nvdev);
-	int i;
+	struct netvsc_vf_pcpu_stats vf_tot;
+		int i;
 
 	if (!nvdev)
 		return;
 
+	netdev_stats_to_stats64(t, &net->stats);
+
+	netvsc_get_vf_stats(net, &vf_tot);
+	t->rx_packets += vf_tot.rx_packets;
+	t->tx_packets += vf_tot.tx_packets;
+	t->rx_bytes   += vf_tot.rx_bytes;
+	t->tx_bytes   += vf_tot.tx_bytes;
+	t->tx_dropped += vf_tot.tx_dropped;
+
 	for (i = 0; i < nvdev->num_chn; i++) {
 		const struct netvsc_channel *nvchan = &nvdev->chan_table[i];
 		const struct netvsc_stats *stats;
@@ -934,12 +1047,6 @@ static void netvsc_get_stats64(struct net_device *net,
 		t->rx_packets	+= packets;
 		t->multicast	+= multicast;
 	}
-
-	t->tx_dropped	= net->stats.tx_dropped;
-	t->tx_errors	= net->stats.tx_errors;
-
-	t->rx_dropped	= net->stats.rx_dropped;
-	t->rx_errors	= net->stats.rx_errors;
 }
 
 static int netvsc_set_mac_addr(struct net_device *ndev, void *p)
@@ -980,9 +1087,16 @@ static const struct {
 	{ "tx_no_space",  offsetof(struct netvsc_ethtool_stats, tx_no_space) },
 	{ "tx_too_big",	  offsetof(struct netvsc_ethtool_stats, tx_too_big) },
 	{ "tx_busy",	  offsetof(struct netvsc_ethtool_stats, tx_busy) },
+}, vf_stats[] = {
+	{ "vf_rx_packets", offsetof(struct netvsc_vf_pcpu_stats, rx_packets) },
+	{ "vf_rx_bytes",   offsetof(struct netvsc_vf_pcpu_stats, rx_bytes) },
+	{ "vf_tx_packets", offsetof(struct netvsc_vf_pcpu_stats, tx_packets) },
+	{ "vf_tx_bytes",   offsetof(struct netvsc_vf_pcpu_stats, tx_bytes) },
+	{ "vf_tx_dropped", offsetof(struct netvsc_vf_pcpu_stats, tx_dropped) },
 };
 
 #define NETVSC_GLOBAL_STATS_LEN	ARRAY_SIZE(netvsc_stats)
+#define NETVSC_VF_STATS_LEN	ARRAY_SIZE(vf_stats)
 
 /* 4 statistics per queue (rx/tx packets/bytes) */
 #define NETVSC_QUEUE_STATS_LEN(dev) ((dev)->num_chn * 4)
@@ -997,7 +1111,9 @@ static int netvsc_get_sset_count(struct net_device *dev, int string_set)
 
 	switch (string_set) {
 	case ETH_SS_STATS:
-		return NETVSC_GLOBAL_STATS_LEN + NETVSC_QUEUE_STATS_LEN(nvdev);
+		return NETVSC_GLOBAL_STATS_LEN
+			+ NETVSC_VF_STATS_LEN
+			+ NETVSC_QUEUE_STATS_LEN(nvdev);
 	default:
 		return -EINVAL;
 	}
@@ -1010,6 +1126,7 @@ static void netvsc_get_ethtool_stats(struct net_device *dev,
 	struct netvsc_device *nvdev = rtnl_dereference(ndc->nvdev);
 	const void *nds = &ndc->eth_stats;
 	const struct netvsc_stats *qstats;
+	struct netvsc_vf_pcpu_stats sum;
 	unsigned int start;
 	u64 packets, bytes;
 	int i, j;
@@ -1020,6 +1137,10 @@ static void netvsc_get_ethtool_stats(struct net_device *dev,
 	for (i = 0; i < NETVSC_GLOBAL_STATS_LEN; i++)
 		data[i] = *(unsigned long *)(nds + netvsc_stats[i].offset);
 
+	netvsc_get_vf_stats(dev, &sum);
+	for (j = 0; j < NETVSC_VF_STATS_LEN; j++)
+		data[i++] = *(u64 *)((void *)&sum + vf_stats[j].offset);
+
 	for (j = 0; j < nvdev->num_chn; j++) {
 		qstats = &nvdev->chan_table[j].tx_stats;
 
@@ -1054,11 +1175,16 @@ static void netvsc_get_strings(struct net_device *dev, u32 stringset, u8 *data)
 
 	switch (stringset) {
 	case ETH_SS_STATS:
-		for (i = 0; i < ARRAY_SIZE(netvsc_stats); i++)
-			memcpy(p + i * ETH_GSTRING_LEN,
-			       netvsc_stats[i].name, ETH_GSTRING_LEN);
+		for (i = 0; i < ARRAY_SIZE(netvsc_stats); i++) {
+			memcpy(p, netvsc_stats[i].name, ETH_GSTRING_LEN);
+			p += ETH_GSTRING_LEN;
+		}
+
+		for (i = 0; i < ARRAY_SIZE(vf_stats); i++) {
+			memcpy(p, vf_stats[i].name, ETH_GSTRING_LEN);
+			p += ETH_GSTRING_LEN;
+		}
 
-		p += i * ETH_GSTRING_LEN;
 		for (i = 0; i < nvdev->num_chn; i++) {
 			sprintf(p, "tx_queue_%u_packets", i);
 			p += ETH_GSTRING_LEN;
@@ -1298,8 +1424,7 @@ static void netvsc_link_change(struct work_struct *w)
 	case RNDIS_STATUS_MEDIA_CONNECT:
 		if (rdev->link_state) {
 			rdev->link_state = false;
-			if (!ndev_ctx->datapath)
-				netif_carrier_on(net);
+			netif_carrier_on(net);
 			netif_tx_wake_all_queues(net);
 		} else {
 			notify = true;
@@ -1386,6 +1511,104 @@ static struct net_device *get_netvsc_byref(struct net_device *vf_netdev)
 	return NULL;
 }
 
+/* Called when VF is injecting data into network stack.
+ * Change the associated network device from VF to netvsc.
+ * note: already called with rcu_read_lock
+ */
+static rx_handler_result_t netvsc_vf_handle_frame(struct sk_buff **pskb)
+{
+	struct sk_buff *skb = *pskb;
+	struct net_device *ndev = rcu_dereference(skb->dev->rx_handler_data);
+	struct net_device_context *ndev_ctx = netdev_priv(ndev);
+	struct netvsc_vf_pcpu_stats *pcpu_stats
+		 = this_cpu_ptr(ndev_ctx->vf_stats);
+
+	skb->dev = ndev;
+
+	u64_stats_update_begin(&pcpu_stats->syncp);
+	pcpu_stats->rx_packets++;
+	pcpu_stats->rx_bytes += skb->len;
+	u64_stats_update_end(&pcpu_stats->syncp);
+
+	return RX_HANDLER_ANOTHER;
+}
+
+static int netvsc_vf_join(struct net_device *vf_netdev,
+			  struct net_device *ndev)
+{
+	struct net_device_context *ndev_ctx = netdev_priv(ndev);
+	int ret;
+
+	ret = netdev_rx_handler_register(vf_netdev,
+					 netvsc_vf_handle_frame, ndev);
+	if (ret != 0) {
+		netdev_err(vf_netdev,
+			   "can not register netvsc VF receive handler (err = %d)\n",
+			   ret);
+		goto rx_handler_failed;
+	}
+
+	ret = netdev_upper_dev_link(vf_netdev, ndev);
+	if (ret != 0) {
+		netdev_err(vf_netdev,
+			   "can not set master device %s (err = %d)\n",
+			   ndev->name, ret);
+		goto upper_link_failed;
+	}
+
+	/* set slave flag before open to prevent IPv6 addrconf */
+	vf_netdev->flags |= IFF_SLAVE;
+
+	schedule_work(&ndev_ctx->vf_takeover);
+
+	netdev_info(vf_netdev, "joined to %s\n", ndev->name);
+	return 0;
+
+upper_link_failed:
+	netdev_rx_handler_unregister(vf_netdev);
+rx_handler_failed:
+	return ret;
+}
+
+static void __netvsc_vf_setup(struct net_device *ndev,
+			      struct net_device *vf_netdev)
+{
+	int ret;
+
+	call_netdevice_notifiers(NETDEV_JOIN, vf_netdev);
+
+	/* Align MTU of VF with master */
+	ret = dev_set_mtu(vf_netdev, ndev->mtu);
+	if (ret)
+		netdev_warn(vf_netdev,
+			    "unable to change mtu to %u\n", ndev->mtu);
+
+	if (netif_running(ndev)) {
+		ret = dev_open(vf_netdev);
+		if (ret)
+			netdev_warn(vf_netdev,
+				    "unable to open: %d\n", ret);
+	}
+}
+
+/* Setup VF as slave of the synthetic device.
+ * Runs in workqueue to avoid recursion in netlink callbacks.
+ */
+static void netvsc_vf_setup(struct work_struct *w)
+{
+	struct net_device_context *ndev_ctx
+		= container_of(w, struct net_device_context, vf_takeover);
+	struct net_device *ndev = hv_get_drvdata(ndev_ctx->device_ctx);
+	struct net_device *vf_netdev;
+
+	rtnl_lock();
+	vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev);
+	if (vf_netdev)
+		__netvsc_vf_setup(ndev, vf_netdev);
+
+	rtnl_unlock();
+}
+
 static int netvsc_register_vf(struct net_device *vf_netdev)
 {
 	struct net_device *ndev;
@@ -1409,10 +1632,12 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
 	if (!netvsc_dev || rtnl_dereference(net_device_ctx->vf_netdev))
 		return NOTIFY_DONE;
 
+	if (netvsc_vf_join(vf_netdev, ndev) != 0)
+		return NOTIFY_DONE;
+
 	netdev_info(ndev, "VF registering: %s\n", vf_netdev->name);
-	/*
-	 * Take a reference on the module.
-	 */
+
+	/* Prevent this module from being unloaded while VF is registered */
 	try_module_get(THIS_MODULE);
 
 	dev_hold(vf_netdev);
@@ -1420,61 +1645,59 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
 	return NOTIFY_OK;
 }
 
-static int netvsc_vf_up(struct net_device *vf_netdev)
+/* Change datapath */
+static void netvsc_vf_update(struct work_struct *w)
 {
-	struct net_device *ndev;
+	struct net_device_context *ndev_ctx
+		= container_of(w, struct net_device_context, vf_notify);
+	struct net_device *ndev = hv_get_drvdata(ndev_ctx->device_ctx);
 	struct netvsc_device *netvsc_dev;
-	struct net_device_context *net_device_ctx;
-
-	ndev = get_netvsc_byref(vf_netdev);
-	if (!ndev)
-		return NOTIFY_DONE;
-
-	net_device_ctx = netdev_priv(ndev);
-	netvsc_dev = rtnl_dereference(net_device_ctx->nvdev);
-
-	netdev_info(ndev, "VF up: %s\n", vf_netdev->name);
-
-	/*
-	 * Open the device before switching data path.
-	 */
-	rndis_filter_open(netvsc_dev);
-
-	/*
-	 * notify the host to switch the data path.
-	 */
-	netvsc_switch_datapath(ndev, true);
-	netdev_info(ndev, "Data path switched to VF: %s\n", vf_netdev->name);
-
-	netif_carrier_off(ndev);
+	struct net_device *vf_netdev;
+	bool vf_is_up;
 
-	/* Now notify peers through VF device. */
-	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, vf_netdev);
+	rtnl_lock();
+	vf_netdev = rtnl_dereference(ndev_ctx->vf_netdev);
+	if (!vf_netdev)
+		goto unlock;
+
+	netvsc_dev = rtnl_dereference(ndev_ctx->nvdev);
+	if (!netvsc_dev)
+		goto unlock;
+
+	vf_is_up = netif_running(vf_netdev);
+	if (vf_is_up != ndev_ctx->datapath) {
+		if (vf_is_up) {
+			netdev_info(ndev, "VF up: %s\n", vf_netdev->name);
+			rndis_filter_open(netvsc_dev);
+			netvsc_switch_datapath(ndev, true);
+			netdev_info(ndev, "Data path switched to VF: %s\n",
+				    vf_netdev->name);
+		} else {
+			netdev_info(ndev, "VF down: %s\n", vf_netdev->name);
+			netvsc_switch_datapath(ndev, false);
+			rndis_filter_close(netvsc_dev);
+			netdev_info(ndev, "Data path switched from VF: %s\n",
+				    vf_netdev->name);
+		}
 
-	return NOTIFY_OK;
+		/* Now notify peers through VF device. */
+		call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, ndev);
+	}
+unlock:
+	rtnl_unlock();
 }
 
-static int netvsc_vf_down(struct net_device *vf_netdev)
+static int netvsc_vf_notify(struct net_device *vf_netdev)
 {
-	struct net_device *ndev;
-	struct netvsc_device *netvsc_dev;
 	struct net_device_context *net_device_ctx;
+	struct net_device *ndev;
 
 	ndev = get_netvsc_byref(vf_netdev);
 	if (!ndev)
 		return NOTIFY_DONE;
 
 	net_device_ctx = netdev_priv(ndev);
-	netvsc_dev = rtnl_dereference(net_device_ctx->nvdev);
-
-	netdev_info(ndev, "VF down: %s\n", vf_netdev->name);
-	netvsc_switch_datapath(ndev, false);
-	netdev_info(ndev, "Data path switched from VF: %s\n", vf_netdev->name);
-	rndis_filter_close(netvsc_dev);
-	netif_carrier_on(ndev);
-
-	/* Now notify peers through netvsc device. */
-	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, ndev);
+	schedule_work(&net_device_ctx->vf_notify);
 
 	return NOTIFY_OK;
 }
@@ -1489,9 +1712,12 @@ static int netvsc_unregister_vf(struct net_device *vf_netdev)
 		return NOTIFY_DONE;
 
 	net_device_ctx = netdev_priv(ndev);
+	cancel_work_sync(&net_device_ctx->vf_takeover);
+	cancel_work_sync(&net_device_ctx->vf_notify);
 
 	netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name);
 
+	netdev_upper_dev_unlink(vf_netdev, ndev);
 	RCU_INIT_POINTER(net_device_ctx->vf_netdev, NULL);
 	dev_put(vf_netdev);
 	module_put(THIS_MODULE);
@@ -1505,12 +1731,12 @@ static int netvsc_probe(struct hv_device *dev,
 	struct net_device_context *net_device_ctx;
 	struct netvsc_device_info device_info;
 	struct netvsc_device *nvdev;
-	int ret;
+	int ret = -ENOMEM;
 
 	net = alloc_etherdev_mq(sizeof(struct net_device_context),
 				VRSS_CHANNEL_MAX);
 	if (!net)
-		return -ENOMEM;
+		goto no_net;
 
 	netif_carrier_off(net);
 
@@ -1529,6 +1755,13 @@ static int netvsc_probe(struct hv_device *dev,
 
 	spin_lock_init(&net_device_ctx->lock);
 	INIT_LIST_HEAD(&net_device_ctx->reconfig_events);
+	INIT_WORK(&net_device_ctx->vf_takeover, netvsc_vf_setup);
+	INIT_WORK(&net_device_ctx->vf_notify, netvsc_vf_update);
+
+	net_device_ctx->vf_stats
+		= netdev_alloc_pcpu_stats(struct netvsc_vf_pcpu_stats);
+	if (!net_device_ctx->vf_stats)
+		goto no_stats;
 
 	net->netdev_ops = &device_ops;
 	net->ethtool_ops = &ethtool_ops;
@@ -1546,10 +1779,9 @@ static int netvsc_probe(struct hv_device *dev,
 	if (IS_ERR(nvdev)) {
 		ret = PTR_ERR(nvdev);
 		netdev_err(net, "unable to add netvsc device (ret %d)\n", ret);
-		free_netdev(net);
-		hv_set_drvdata(dev, NULL);
-		return ret;
+		goto rndis_failed;
 	}
+
 	memcpy(net->dev_addr, device_info.mac_adr, ETH_ALEN);
 
 	/* hw_features computed in rndis_filter_device_add */
@@ -1573,11 +1805,20 @@ static int netvsc_probe(struct hv_device *dev,
 	ret = register_netdev(net);
 	if (ret != 0) {
 		pr_err("Unable to register netdev.\n");
-		rndis_filter_device_remove(dev, nvdev);
-		free_netdev(net);
+		goto register_failed;
 	}
 
 	return ret;
+
+register_failed:
+	rndis_filter_device_remove(dev, nvdev);
+rndis_failed:
+	free_percpu(net_device_ctx->vf_stats);
+no_stats:
+	hv_set_drvdata(dev, NULL);
+	free_netdev(net);
+no_net:
+	return ret;
 }
 
 static int netvsc_remove(struct hv_device *dev)
@@ -1611,6 +1852,7 @@ static int netvsc_remove(struct hv_device *dev)
 
 	hv_set_drvdata(dev, NULL);
 
+	free_percpu(ndev_ctx->vf_stats);
 	free_netdev(net);
 	return 0;
 }
@@ -1665,9 +1907,8 @@ static int netvsc_netdev_event(struct notifier_block *this,
 	case NETDEV_UNREGISTER:
 		return netvsc_unregister_vf(event_dev);
 	case NETDEV_UP:
-		return netvsc_vf_up(event_dev);
 	case NETDEV_DOWN:
-		return netvsc_vf_down(event_dev);
+		return netvsc_vf_notify(event_dev);
 	default:
 		return NOTIFY_DONE;
 	}
-- 
2.11.0