Merge branch 'xen-netback-netfront-multiqueue'

Wei Liu says:

====================
This is rebased version of Andrew's V8 patch series. The original cover letter:

--------------------
xen-net{back,	front}: Multiple transmit and receive queues

This patch series implements multiple transmit and receive queues (i.e.
multiple shared rings) for the xen virtual network interfaces.

The series is split up as follows:
 - Patch 1 brings the 'grant_copy_op' array back into struct xenvif, in
   preparation for multi-queue support. See the patch itself for more details.
- Patches 2 and 4 factor out the queue-specific data for netback and
  netfront respectively, and modify the rest of the code to use these
  as appropriate.
- Patches 3 and 5 introduce new XenStore keys to negotiate and use
  multiple shared rings and event channels, and code to connect these
  as appropriate.
- Patch 6 documents the XenStore keys required for the new feature
  in include/xen/interface/io/netif.h

All other transmit and receive processing remains unchanged, i.e. there
is a kthread per queue and a NAPI context per queue.

The performance of these patches has been analysed in detail, with
results available at:

http://wiki.xenproject.org/wiki/Xen-netback_and_xen-netfront_multi-queue_performance_testing

To summarise:
  * Using multiple queues allows a VM to transmit at line rate on a 10
    Gbit/s NIC, compared with a maximum aggregate throughput of 6 Gbit/s
    with a single queue.
  * For intra-host VM--VM traffic, eight queues provide 171% of the
    throughput of a single queue; almost 12 Gbit/s instead of 6 Gbit/s.
  * There is a corresponding increase in total CPU usage, i.e. this is a
    scaling out over available resources, not an efficiency improvement.
  * Results depend on the availability of sufficient CPUs, as well as the
    distribution of interrupts and the distribution of TCP streams across
    the queues.

Queue selection is currently achieved via an L4 hash on the packet (i.e.
TCP src/dst port, IP src/dst address) and is not negotiated between the
frontend and backend, since only one option exists. Future patches to
support other frontends (particularly Windows) will need to add some
capability to negotiate not only the hash algorithm selection, but also
allow the frontend to specify some parameters to this.

Note that queue selection is a decision by the transmitting system about
which queue to use for a particular packet. In general, the algorithm
may differ between the frontend and the backend with no adverse effects.

Queue-specific XenStore entries for ring references and event channels
are stored hierarchically, i.e. under .../queue-N/... where N varies
from 0 to one less than the requested number of queues (inclusive). If
only one queue is requested, it falls back to the flat structure where
the ring references and event channels are written at the same level as
other vif information.

V8:
- Squash the queue error handling code into patch 3.
- Update the documentation (patch 6) according to comments on the
  equivalent patch to Xen.

V7:
- Rebase on latest net-next, which includes the netback grant mapping
  patch series from Zoltan Kiss
- Reduce QUEUE_NAME_SIZE by 1 to avoid double-counting the trailing '\0'
- Simplify the queue hashing by using (hash % num_queues) instead of
  multiply & shift.
- Add ratelimited warning for invalid queue selection.
- Fix error handling to correctly tear down already setup queues.
- Use dev->real_num_tx_queues instead of separately maintaining a
  count of the number of queues.

V6:
- Use 'max_queues' as the module param. name for both netback and netfront.

V5:
- Fix bug in xenvif_free() that could lead to an attempt to transmit an
  skb after the queue structures had been freed.
- Improve the XenStore protocol documentation in netif.h.
- Fix IRQ_NAME_SIZE double-accounting for null terminator.
- Move rx_gso_checksum_fixup stat into struct xenvif_stats (per-queue).
- Don't initialise a local variable that is set in both branches (xspath).

V4:
- Add MODULE_PARM_DESC() for the multi-queue parameters for netback
  and netfront modules.
- Move del_timer_sync() in netfront to after unregister_netdev, which
  restores the order in which these functions were called before applying
  these patches.

V3:
- Further indentation and style fixups.

V2:
- Rebase onto net-next.
- Change queue->number to queue->id.
- Add atomic operations around the small number of stats variables that
  are not queue-specific or per-cpu.
- Fixup formatting and style issues.
- XenStore protocol changes documented in netif.h.
- Default max. number of queues to num_online_cpus().
- Check requested number of queues does not exceed maximum.
--------------------

I rebased this on top of net-next. No functional change is introduced.  The
patch that needed some extra care was "xen-netback: Factor queue-specific data
into queue struct" because it clashed with a fix introduced in net. A simple
test of creating guest, iperf, then shutting down guest worked as expected.

The last patch fixes a minor problem that queue name is not initialised in
xen-netfront, resulting in names like "-tx" "-rx" in /proc/interrupt.

Changes since v9 (no functional change introduced):
* include commit summary in the commit message of first patch
* fold David Vrabel's Reviewed-by into last patch
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 337 insertions, 185 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 53cdcdf3dfa..6929bcb61cf 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -34,7 +34,6 @@
 #include <linux/ethtool.h>
 #include <linux/rtnetlink.h>
 #include <linux/if_vlan.h>
-#include <linux/vmalloc.h>
 
 #include <xen/events.h>
 #include <asm/xen/hypercall.h>
@@ -43,6 +42,16 @@
 #define XENVIF_QUEUE_LENGTH 32
 #define XENVIF_NAPI_WEIGHT  64
 
+static inline void xenvif_stop_queue(struct xenvif_queue *queue)
+{
+	struct net_device *dev = queue->vif->dev;
+
+	if (!queue->vif->can_queue)
+		return;
+
+	netif_tx_stop_queue(netdev_get_tx_queue(dev, queue->id));
+}
+
 int xenvif_schedulable(struct xenvif *vif)
 {
 	return netif_running(vif->dev) && netif_carrier_ok(vif->dev);
@@ -50,33 +59,34 @@ int xenvif_schedulable(struct xenvif *vif)
 
 static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
 {
-	struct xenvif *vif = dev_id;
+	struct xenvif_queue *queue = dev_id;
 
-	if (RING_HAS_UNCONSUMED_REQUESTS(&vif->tx))
-		napi_schedule(&vif->napi);
+	if (RING_HAS_UNCONSUMED_REQUESTS(&queue->tx))
+		napi_schedule(&queue->napi);
 
 	return IRQ_HANDLED;
 }
 
-static int xenvif_poll(struct napi_struct *napi, int budget)
+int xenvif_poll(struct napi_struct *napi, int budget)
 {
-	struct xenvif *vif = container_of(napi, struct xenvif, napi);
+	struct xenvif_queue *queue =
+		container_of(napi, struct xenvif_queue, napi);
 	int work_done;
 
 	/* This vif is rogue, we pretend we've there is nothing to do
 	 * for this vif to deschedule it from NAPI. But this interface
 	 * will be turned off in thread context later.
 	 */
-	if (unlikely(vif->disabled)) {
+	if (unlikely(queue->vif->disabled)) {
 		napi_complete(napi);
 		return 0;
 	}
 
-	work_done = xenvif_tx_action(vif, budget);
+	work_done = xenvif_tx_action(queue, budget);
 
 	if (work_done < budget) {
 		napi_complete(napi);
-		xenvif_napi_schedule_or_enable_events(vif);
+		xenvif_napi_schedule_or_enable_events(queue);
 	}
 
 	return work_done;
@@ -84,9 +94,9 @@ static int xenvif_poll(struct napi_struct *napi, int budget)
 
 static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
 {
-	struct xenvif *vif = dev_id;
+	struct xenvif_queue *queue = dev_id;
 
-	xenvif_kick_thread(vif);
+	xenvif_kick_thread(queue);
 
 	return IRQ_HANDLED;
 }
@@ -99,28 +109,80 @@ static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static void xenvif_wake_queue(unsigned long data)
+int xenvif_queue_stopped(struct xenvif_queue *queue)
 {
-	struct xenvif *vif = (struct xenvif *)data;
+	struct net_device *dev = queue->vif->dev;
+	unsigned int id = queue->id;
+	return netif_tx_queue_stopped(netdev_get_tx_queue(dev, id));
+}
 
-	if (netif_queue_stopped(vif->dev)) {
-		netdev_err(vif->dev, "draining TX queue\n");
-		vif->rx_queue_purge = true;
-		xenvif_kick_thread(vif);
-		netif_wake_queue(vif->dev);
+void xenvif_wake_queue(struct xenvif_queue *queue)
+{
+	struct net_device *dev = queue->vif->dev;
+	unsigned int id = queue->id;
+	netif_tx_wake_queue(netdev_get_tx_queue(dev, id));
+}
+
+/* Callback to wake the queue and drain it on timeout */
+static void xenvif_wake_queue_callback(unsigned long data)
+{
+	struct xenvif_queue *queue = (struct xenvif_queue *)data;
+
+	if (xenvif_queue_stopped(queue)) {
+		netdev_err(queue->vif->dev, "draining TX queue\n");
+		queue->rx_queue_purge = true;
+		xenvif_kick_thread(queue);
+		xenvif_wake_queue(queue);
 	}
 }
 
+static u16 xenvif_select_queue(struct net_device *dev, struct sk_buff *skb,
+			       void *accel_priv, select_queue_fallback_t fallback)
+{
+	unsigned int num_queues = dev->real_num_tx_queues;
+	u32 hash;
+	u16 queue_index;
+
+	/* First, check if there is only one queue to optimise the
+	 * single-queue or old frontend scenario.
+	 */
+	if (num_queues == 1) {
+		queue_index = 0;
+	} else {
+		/* Use skb_get_hash to obtain an L4 hash if available */
+		hash = skb_get_hash(skb);
+		queue_index = hash % num_queues;
+	}
+
+	return queue_index;
+}
+
 static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct xenvif *vif = netdev_priv(dev);
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = dev->real_num_tx_queues;
+	u16 index;
 	int min_slots_needed;
 
 	BUG_ON(skb->dev != dev);
 
-	/* Drop the packet if vif is not ready */
-	if (vif->task == NULL ||
-	    vif->dealloc_task == NULL ||
+	/* Drop the packet if queues are not set up */
+	if (num_queues < 1)
+		goto drop;
+
+	/* Obtain the queue to be used to transmit this packet */
+	index = skb_get_queue_mapping(skb);
+	if (index >= num_queues) {
+		pr_warn_ratelimited("Invalid queue %hu for packet on interface %s\n.",
+				    index, vif->dev->name);
+		index %= num_queues;
+	}
+	queue = &vif->queues[index];
+
+	/* Drop the packet if queue is not ready */
+	if (queue->task == NULL ||
+	    queue->dealloc_task == NULL ||
 	    !xenvif_schedulable(vif))
 		goto drop;
 
@@ -139,16 +201,16 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	 * then turn off the queue to give the ring a chance to
 	 * drain.
 	 */
-	if (!xenvif_rx_ring_slots_available(vif, min_slots_needed)) {
-		vif->wake_queue.function = xenvif_wake_queue;
-		vif->wake_queue.data = (unsigned long)vif;
-		xenvif_stop_queue(vif);
-		mod_timer(&vif->wake_queue,
+	if (!xenvif_rx_ring_slots_available(queue, min_slots_needed)) {
+		queue->wake_queue.function = xenvif_wake_queue_callback;
+		queue->wake_queue.data = (unsigned long)queue;
+		xenvif_stop_queue(queue);
+		mod_timer(&queue->wake_queue,
 			jiffies + rx_drain_timeout_jiffies);
 	}
 
-	skb_queue_tail(&vif->rx_queue, skb);
-	xenvif_kick_thread(vif);
+	skb_queue_tail(&queue->rx_queue, skb);
+	xenvif_kick_thread(queue);
 
 	return NETDEV_TX_OK;
 
@@ -161,25 +223,65 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 static struct net_device_stats *xenvif_get_stats(struct net_device *dev)
 {
 	struct xenvif *vif = netdev_priv(dev);
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = dev->real_num_tx_queues;
+	unsigned long rx_bytes = 0;
+	unsigned long rx_packets = 0;
+	unsigned long tx_bytes = 0;
+	unsigned long tx_packets = 0;
+	unsigned int index;
+
+	if (vif->queues == NULL)
+		goto out;
+
+	/* Aggregate tx and rx stats from each queue */
+	for (index = 0; index < num_queues; ++index) {
+		queue = &vif->queues[index];
+		rx_bytes += queue->stats.rx_bytes;
+		rx_packets += queue->stats.rx_packets;
+		tx_bytes += queue->stats.tx_bytes;
+		tx_packets += queue->stats.tx_packets;
+	}
+
+out:
+	vif->dev->stats.rx_bytes = rx_bytes;
+	vif->dev->stats.rx_packets = rx_packets;
+	vif->dev->stats.tx_bytes = tx_bytes;
+	vif->dev->stats.tx_packets = tx_packets;
+
 	return &vif->dev->stats;
 }
 
 static void xenvif_up(struct xenvif *vif)
 {
-	napi_enable(&vif->napi);
-	enable_irq(vif->tx_irq);
-	if (vif->tx_irq != vif->rx_irq)
-		enable_irq(vif->rx_irq);
-	xenvif_napi_schedule_or_enable_events(vif);
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->dev->real_num_tx_queues;
+	unsigned int queue_index;
+
+	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+		queue = &vif->queues[queue_index];
+		napi_enable(&queue->napi);
+		enable_irq(queue->tx_irq);
+		if (queue->tx_irq != queue->rx_irq)
+			enable_irq(queue->rx_irq);
+		xenvif_napi_schedule_or_enable_events(queue);
+	}
 }
 
 static void xenvif_down(struct xenvif *vif)
 {
-	napi_disable(&vif->napi);
-	disable_irq(vif->tx_irq);
-	if (vif->tx_irq != vif->rx_irq)
-		disable_irq(vif->rx_irq);
-	del_timer_sync(&vif->credit_timeout);
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->dev->real_num_tx_queues;
+	unsigned int queue_index;
+
+	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+		queue = &vif->queues[queue_index];
+		napi_disable(&queue->napi);
+		disable_irq(queue->tx_irq);
+		if (queue->tx_irq != queue->rx_irq)
+			disable_irq(queue->rx_irq);
+		del_timer_sync(&queue->credit_timeout);
+	}
 }
 
 static int xenvif_open(struct net_device *dev)
@@ -187,7 +289,7 @@ static int xenvif_open(struct net_device *dev)
 	struct xenvif *vif = netdev_priv(dev);
 	if (netif_carrier_ok(dev))
 		xenvif_up(vif);
-	netif_start_queue(dev);
+	netif_tx_start_all_queues(dev);
 	return 0;
 }
 
@@ -196,7 +298,7 @@ static int xenvif_close(struct net_device *dev)
 	struct xenvif *vif = netdev_priv(dev);
 	if (netif_carrier_ok(dev))
 		xenvif_down(vif);
-	netif_stop_queue(dev);
+	netif_tx_stop_all_queues(dev);
 	return 0;
 }
 
@@ -236,29 +338,29 @@ static const struct xenvif_stat {
 } xenvif_stats[] = {
 	{
 		"rx_gso_checksum_fixup",
-		offsetof(struct xenvif, rx_gso_checksum_fixup)
+		offsetof(struct xenvif_stats, rx_gso_checksum_fixup)
 	},
 	/* If (sent != success + fail), there are probably packets never
 	 * freed up properly!
 	 */
 	{
 		"tx_zerocopy_sent",
-		offsetof(struct xenvif, tx_zerocopy_sent),
+		offsetof(struct xenvif_stats, tx_zerocopy_sent),
 	},
 	{
 		"tx_zerocopy_success",
-		offsetof(struct xenvif, tx_zerocopy_success),
+		offsetof(struct xenvif_stats, tx_zerocopy_success),
 	},
 	{
 		"tx_zerocopy_fail",
-		offsetof(struct xenvif, tx_zerocopy_fail)
+		offsetof(struct xenvif_stats, tx_zerocopy_fail)
 	},
 	/* Number of packets exceeding MAX_SKB_FRAG slots. You should use
 	 * a guest with the same MAX_SKB_FRAG
 	 */
 	{
 		"tx_frag_overflow",
-		offsetof(struct xenvif, tx_frag_overflow)
+		offsetof(struct xenvif_stats, tx_frag_overflow)
 	},
 };
 
@@ -275,11 +377,20 @@ static int xenvif_get_sset_count(struct net_device *dev, int string_set)
 static void xenvif_get_ethtool_stats(struct net_device *dev,
 				     struct ethtool_stats *stats, u64 * data)
 {
-	void *vif = netdev_priv(dev);
+	struct xenvif *vif = netdev_priv(dev);
+	unsigned int num_queues = dev->real_num_tx_queues;
 	int i;
-
-	for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++)
-		data[i] = *(unsigned long *)(vif + xenvif_stats[i].offset);
+	unsigned int queue_index;
+	struct xenvif_stats *vif_stats;
+
+	for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++) {
+		unsigned long accum = 0;
+		for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+			vif_stats = &vif->queues[queue_index].stats;
+			accum += *(unsigned long *)(vif_stats + xenvif_stats[i].offset);
+		}
+		data[i] = accum;
+	}
 }
 
 static void xenvif_get_strings(struct net_device *dev, u32 stringset, u8 * data)
@@ -312,6 +423,7 @@ static const struct net_device_ops xenvif_netdev_ops = {
 	.ndo_fix_features = xenvif_fix_features,
 	.ndo_set_mac_address = eth_mac_addr,
 	.ndo_validate_addr   = eth_validate_addr,
+	.ndo_select_queue = xenvif_select_queue,
 };
 
 struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
@@ -321,10 +433,14 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 	struct net_device *dev;
 	struct xenvif *vif;
 	char name[IFNAMSIZ] = {};
-	int i;
 
 	snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle);
-	dev = alloc_netdev(sizeof(struct xenvif), name, ether_setup);
+	/* Allocate a netdev with the max. supported number of queues.
+	 * When the guest selects the desired number, it will be updated
+	 * via netif_set_real_num_tx_queues().
+	 */
+	dev = alloc_netdev_mq(sizeof(struct xenvif), name, ether_setup,
+			      xenvif_max_queues);
 	if (dev == NULL) {
 		pr_warn("Could not allocate netdev for %s\n", name);
 		return ERR_PTR(-ENOMEM);
@@ -334,28 +450,18 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 
 	vif = netdev_priv(dev);
 
-	vif->grant_copy_op = vmalloc(sizeof(struct gnttab_copy) *
-				     MAX_GRANT_COPY_OPS);
-	if (vif->grant_copy_op == NULL) {
-		pr_warn("Could not allocate grant copy space for %s\n", name);
-		free_netdev(dev);
-		return ERR_PTR(-ENOMEM);
-	}
-
 	vif->domid  = domid;
 	vif->handle = handle;
 	vif->can_sg = 1;
 	vif->ip_csum = 1;
 	vif->dev = dev;
-
 	vif->disabled = false;
 
-	vif->credit_bytes = vif->remaining_credit = ~0UL;
-	vif->credit_usec  = 0UL;
-	init_timer(&vif->credit_timeout);
-	vif->credit_window_start = get_jiffies_64();
-
-	init_timer(&vif->wake_queue);
+	/* Start out with no queues. The call below does not require
+	 * rtnl_lock() as it happens before register_netdev().
+	 */
+	vif->queues = NULL;
+	netif_set_real_num_tx_queues(dev, 0);
 
 	dev->netdev_ops	= &xenvif_netdev_ops;
 	dev->hw_features = NETIF_F_SG |
@@ -366,34 +472,6 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 
 	dev->tx_queue_len = XENVIF_QUEUE_LENGTH;
 
-	skb_queue_head_init(&vif->rx_queue);
-	skb_queue_head_init(&vif->tx_queue);
-
-	vif->pending_cons = 0;
-	vif->pending_prod = MAX_PENDING_REQS;
-	for (i = 0; i < MAX_PENDING_REQS; i++)
-		vif->pending_ring[i] = i;
-	spin_lock_init(&vif->callback_lock);
-	spin_lock_init(&vif->response_lock);
-	/* If ballooning is disabled, this will consume real memory, so you
-	 * better enable it. The long term solution would be to use just a
-	 * bunch of valid page descriptors, without dependency on ballooning
-	 */
-	err = alloc_xenballooned_pages(MAX_PENDING_REQS,
-				       vif->mmap_pages,
-				       false);
-	if (err) {
-		netdev_err(dev, "Could not reserve mmap_pages\n");
-		return ERR_PTR(-ENOMEM);
-	}
-	for (i = 0; i < MAX_PENDING_REQS; i++) {
-		vif->pending_tx_info[i].callback_struct = (struct ubuf_info)
-			{ .callback = xenvif_zerocopy_callback,
-			  .ctx = NULL,
-			  .desc = i };
-		vif->grant_tx_handle[i] = NETBACK_INVALID_HANDLE;
-	}
-
 	/*
 	 * Initialise a dummy MAC address. We choose the numerically
 	 * largest non-broadcast address to prevent the address getting
@@ -403,8 +481,6 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 	memset(dev->dev_addr, 0xFF, ETH_ALEN);
 	dev->dev_addr[0] &= ~0x01;
 
-	netif_napi_add(dev, &vif->napi, xenvif_poll, XENVIF_NAPI_WEIGHT);
-
 	netif_carrier_off(dev);
 
 	err = register_netdev(dev);
@@ -421,98 +497,147 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
 	return vif;
 }
 
-int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
+int xenvif_init_queue(struct xenvif_queue *queue)
+{
+	int err, i;
+
+	queue->credit_bytes = queue->remaining_credit = ~0UL;
+	queue->credit_usec  = 0UL;
+	init_timer(&queue->credit_timeout);
+	queue->credit_window_start = get_jiffies_64();
+
+	skb_queue_head_init(&queue->rx_queue);
+	skb_queue_head_init(&queue->tx_queue);
+
+	queue->pending_cons = 0;
+	queue->pending_prod = MAX_PENDING_REQS;
+	for (i = 0; i < MAX_PENDING_REQS; ++i)
+		queue->pending_ring[i] = i;
+
+	spin_lock_init(&queue->callback_lock);
+	spin_lock_init(&queue->response_lock);
+
+	/* If ballooning is disabled, this will consume real memory, so you
+	 * better enable it. The long term solution would be to use just a
+	 * bunch of valid page descriptors, without dependency on ballooning
+	 */
+	err = alloc_xenballooned_pages(MAX_PENDING_REQS,
+				       queue->mmap_pages,
+				       false);
+	if (err) {
+		netdev_err(queue->vif->dev, "Could not reserve mmap_pages\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < MAX_PENDING_REQS; i++) {
+		queue->pending_tx_info[i].callback_struct = (struct ubuf_info)
+			{ .callback = xenvif_zerocopy_callback,
+			  .ctx = NULL,
+			  .desc = i };
+		queue->grant_tx_handle[i] = NETBACK_INVALID_HANDLE;
+	}
+
+	init_timer(&queue->wake_queue);
+
+	netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
+			XENVIF_NAPI_WEIGHT);
+
+	return 0;
+}
+
+void xenvif_carrier_on(struct xenvif *vif)
+{
+	rtnl_lock();
+	if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
+		dev_set_mtu(vif->dev, ETH_DATA_LEN);
+	netdev_update_features(vif->dev);
+	netif_carrier_on(vif->dev);
+	if (netif_running(vif->dev))
+		xenvif_up(vif);
+	rtnl_unlock();
+}
+
+int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
 		   unsigned long rx_ring_ref, unsigned int tx_evtchn,
 		   unsigned int rx_evtchn)
 {
 	struct task_struct *task;
 	int err = -ENOMEM;
 
-	BUG_ON(vif->tx_irq);
-	BUG_ON(vif->task);
-	BUG_ON(vif->dealloc_task);
+	BUG_ON(queue->tx_irq);
+	BUG_ON(queue->task);
+	BUG_ON(queue->dealloc_task);
 
-	err = xenvif_map_frontend_rings(vif, tx_ring_ref, rx_ring_ref);
+	err = xenvif_map_frontend_rings(queue, tx_ring_ref, rx_ring_ref);
 	if (err < 0)
 		goto err;
 
-	init_waitqueue_head(&vif->wq);
-	init_waitqueue_head(&vif->dealloc_wq);
+	init_waitqueue_head(&queue->wq);
+	init_waitqueue_head(&queue->dealloc_wq);
 
 	if (tx_evtchn == rx_evtchn) {
 		/* feature-split-event-channels == 0 */
 		err = bind_interdomain_evtchn_to_irqhandler(
-			vif->domid, tx_evtchn, xenvif_interrupt, 0,
-			vif->dev->name, vif);
+			queue->vif->domid, tx_evtchn, xenvif_interrupt, 0,
+			queue->name, queue);
 		if (err < 0)
 			goto err_unmap;
-		vif->tx_irq = vif->rx_irq = err;
-		disable_irq(vif->tx_irq);
+		queue->tx_irq = queue->rx_irq = err;
+		disable_irq(queue->tx_irq);
 	} else {
 		/* feature-split-event-channels == 1 */
-		snprintf(vif->tx_irq_name, sizeof(vif->tx_irq_name),
-			 "%s-tx", vif->dev->name);
+		snprintf(queue->tx_irq_name, sizeof(queue->tx_irq_name),
+			 "%s-tx", queue->name);
 		err = bind_interdomain_evtchn_to_irqhandler(
-			vif->domid, tx_evtchn, xenvif_tx_interrupt, 0,
-			vif->tx_irq_name, vif);
+			queue->vif->domid, tx_evtchn, xenvif_tx_interrupt, 0,
+			queue->tx_irq_name, queue);
 		if (err < 0)
 			goto err_unmap;
-		vif->tx_irq = err;
-		disable_irq(vif->tx_irq);
+		queue->tx_irq = err;
+		disable_irq(queue->tx_irq);
 
-		snprintf(vif->rx_irq_name, sizeof(vif->rx_irq_name),
-			 "%s-rx", vif->dev->name);
+		snprintf(queue->rx_irq_name, sizeof(queue->rx_irq_name),
+			 "%s-rx", queue->name);
 		err = bind_interdomain_evtchn_to_irqhandler(
-			vif->domid, rx_evtchn, xenvif_rx_interrupt, 0,
-			vif->rx_irq_name, vif);
+			queue->vif->domid, rx_evtchn, xenvif_rx_interrupt, 0,
+			queue->rx_irq_name, queue);
 		if (err < 0)
 			goto err_tx_unbind;
-		vif->rx_irq = err;
-		disable_irq(vif->rx_irq);
+		queue->rx_irq = err;
+		disable_irq(queue->rx_irq);
 	}
 
 	task = kthread_create(xenvif_kthread_guest_rx,
-			      (void *)vif, "%s-guest-rx", vif->dev->name);
+			      (void *)queue, "%s-guest-rx", queue->name);
 	if (IS_ERR(task)) {
-		pr_warn("Could not allocate kthread for %s\n", vif->dev->name);
+		pr_warn("Could not allocate kthread for %s\n", queue->name);
 		err = PTR_ERR(task);
 		goto err_rx_unbind;
 	}
-
-	vif->task = task;
+	queue->task = task;
 
 	task = kthread_create(xenvif_dealloc_kthread,
-			      (void *)vif, "%s-dealloc", vif->dev->name);
+			      (void *)queue, "%s-dealloc", queue->name);
 	if (IS_ERR(task)) {
-		pr_warn("Could not allocate kthread for %s\n", vif->dev->name);
+		pr_warn("Could not allocate kthread for %s\n", queue->name);
 		err = PTR_ERR(task);
 		goto err_rx_unbind;
 	}
+	queue->dealloc_task = task;
 
-	vif->dealloc_task = task;
-
-	rtnl_lock();
-	if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
-		dev_set_mtu(vif->dev, ETH_DATA_LEN);
-	netdev_update_features(vif->dev);
-	netif_carrier_on(vif->dev);
-	if (netif_running(vif->dev))
-		xenvif_up(vif);
-	rtnl_unlock();
-
-	wake_up_process(vif->task);
-	wake_up_process(vif->dealloc_task);
+	wake_up_process(queue->task);
+	wake_up_process(queue->dealloc_task);
 
 	return 0;
 
 err_rx_unbind:
-	unbind_from_irqhandler(vif->rx_irq, vif);
-	vif->rx_irq = 0;
+	unbind_from_irqhandler(queue->rx_irq, queue);
+	queue->rx_irq = 0;
 err_tx_unbind:
-	unbind_from_irqhandler(vif->tx_irq, vif);
-	vif->tx_irq = 0;
+	unbind_from_irqhandler(queue->tx_irq, queue);
+	queue->tx_irq = 0;
 err_unmap:
-	xenvif_unmap_frontend_rings(vif);
+	xenvif_unmap_frontend_rings(queue);
 err:
 	module_put(THIS_MODULE);
 	return err;
@@ -529,38 +654,77 @@ void xenvif_carrier_off(struct xenvif *vif)
 	rtnl_unlock();
 }
 
+static void xenvif_wait_unmap_timeout(struct xenvif_queue *queue,
+				      unsigned int worst_case_skb_lifetime)
+{
+	int i, unmap_timeout = 0;
+
+	for (i = 0; i < MAX_PENDING_REQS; ++i) {
+		if (queue->grant_tx_handle[i] != NETBACK_INVALID_HANDLE) {
+			unmap_timeout++;
+			schedule_timeout(msecs_to_jiffies(1000));
+			if (unmap_timeout > worst_case_skb_lifetime &&
+			    net_ratelimit())
+				netdev_err(queue->vif->dev,
+					   "Page still granted! Index: %x\n",
+					   i);
+			i = -1;
+		}
+	}
+}
+
 void xenvif_disconnect(struct xenvif *vif)
 {
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->dev->real_num_tx_queues;
+	unsigned int queue_index;
+
 	if (netif_carrier_ok(vif->dev))
 		xenvif_carrier_off(vif);
 
-	if (vif->task) {
-		del_timer_sync(&vif->wake_queue);
-		kthread_stop(vif->task);
-		vif->task = NULL;
-	}
+	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+		queue = &vif->queues[queue_index];
 
-	if (vif->dealloc_task) {
-		kthread_stop(vif->dealloc_task);
-		vif->dealloc_task = NULL;
-	}
+		if (queue->task) {
+			del_timer_sync(&queue->wake_queue);
+			kthread_stop(queue->task);
+			queue->task = NULL;
+		}
 
-	if (vif->tx_irq) {
-		if (vif->tx_irq == vif->rx_irq)
-			unbind_from_irqhandler(vif->tx_irq, vif);
-		else {
-			unbind_from_irqhandler(vif->tx_irq, vif);
-			unbind_from_irqhandler(vif->rx_irq, vif);
+		if (queue->dealloc_task) {
+			kthread_stop(queue->dealloc_task);
+			queue->dealloc_task = NULL;
 		}
-		vif->tx_irq = 0;
+
+		if (queue->tx_irq) {
+			if (queue->tx_irq == queue->rx_irq)
+				unbind_from_irqhandler(queue->tx_irq, queue);
+			else {
+				unbind_from_irqhandler(queue->tx_irq, queue);
+				unbind_from_irqhandler(queue->rx_irq, queue);
+			}
+			queue->tx_irq = 0;
+		}
+
+		xenvif_unmap_frontend_rings(queue);
 	}
+}
 
-	xenvif_unmap_frontend_rings(vif);
+/* Reverse the relevant parts of xenvif_init_queue().
+ * Used for queue teardown from xenvif_free(), and on the
+ * error handling paths in xenbus.c:connect().
+ */
+void xenvif_deinit_queue(struct xenvif_queue *queue)
+{
+	free_xenballooned_pages(MAX_PENDING_REQS, queue->mmap_pages);
+	netif_napi_del(&queue->napi);
 }
 
 void xenvif_free(struct xenvif *vif)
 {
-	int i, unmap_timeout = 0;
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->dev->real_num_tx_queues;
+	unsigned int queue_index;
 	/* Here we want to avoid timeout messages if an skb can be legitimately
 	 * stuck somewhere else. Realistically this could be an another vif's
 	 * internal or QDisc queue. That another vif also has this
@@ -575,33 +739,21 @@ void xenvif_free(struct xenvif *vif)
 	unsigned int worst_case_skb_lifetime = (rx_drain_timeout_msecs/1000) *
 		DIV_ROUND_UP(XENVIF_QUEUE_LENGTH, (XEN_NETIF_RX_RING_SIZE / MAX_SKB_FRAGS));
 
-	for (i = 0; i < MAX_PENDING_REQS; ++i) {
-		if (vif->grant_tx_handle[i] != NETBACK_INVALID_HANDLE) {
-			unmap_timeout++;
-			schedule_timeout(msecs_to_jiffies(1000));
-			if (unmap_timeout > worst_case_skb_lifetime &&
-			    net_ratelimit())
-				netdev_err(vif->dev,
-					   "Page still granted! Index: %x\n",
-					   i);
-			/* If there are still unmapped pages, reset the loop to
-			 * start checking again. We shouldn't exit here until
-			 * dealloc thread and NAPI instance release all the
-			 * pages. If a kernel bug causes the skbs to stall
-			 * somewhere, the interface cannot be brought down
-			 * properly.
-			 */
-			i = -1;
-		}
-	}
-
-	free_xenballooned_pages(MAX_PENDING_REQS, vif->mmap_pages);
+	unregister_netdev(vif->dev);
 
-	netif_napi_del(&vif->napi);
+	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+		queue = &vif->queues[queue_index];
+		xenvif_wait_unmap_timeout(queue, worst_case_skb_lifetime);
+		xenvif_deinit_queue(queue);
+	}
 
-	unregister_netdev(vif->dev);
+	/* Free the array of queues. The call below does not require
+	 * rtnl_lock() because it happens after unregister_netdev().
+	 */
+	netif_set_real_num_tx_queues(vif->dev, 0);
+	vfree(vif->queues);
+	vif->queues = NULL;
 
-	vfree(vif->grant_copy_op);
 	free_netdev(vif->dev);
 
 	module_put(THIS_MODULE);