Initial import

5 files changed, 4131 insertions, 0 deletions

diff --git a/drivers/net/xen-netback/Makefile b/drivers/net/xen-netback/Makefile
new file mode 100644
index 000000000..e346e8125
--- /dev/null
+++ b/drivers/net/xen-netback/Makefile
@@ -0,0 +1,3 @@
+obj-$(CONFIG_XEN_NETDEV_BACKEND) := xen-netback.o
+
+xen-netback-y := netback.o xenbus.o interface.o
diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
new file mode 100644
index 000000000..8a495b318
--- /dev/null
+++ b/drivers/net/xen-netback/common.h
@@ -0,0 +1,347 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#ifndef __XEN_NETBACK__COMMON_H__
+#define __XEN_NETBACK__COMMON_H__
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/ip.h>
+#include <linux/in.h>
+#include <linux/io.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
+
+#include <xen/interface/io/netif.h>
+#include <xen/interface/grant_table.h>
+#include <xen/grant_table.h>
+#include <xen/xenbus.h>
+#include <linux/debugfs.h>
+
+typedef unsigned int pending_ring_idx_t;
+#define INVALID_PENDING_RING_IDX (~0U)
+
+struct pending_tx_info {
+	struct xen_netif_tx_request req; /* tx request */
+	/* Callback data for released SKBs. The callback is always
+	 * xenvif_zerocopy_callback, desc contains the pending_idx, which is
+	 * also an index in pending_tx_info array. It is initialized in
+	 * xenvif_alloc and it never changes.
+	 * skb_shinfo(skb)->destructor_arg points to the first mapped slot's
+	 * callback_struct in this array of struct pending_tx_info's, then ctx
+	 * to the next, or NULL if there is no more slot for this skb.
+	 * ubuf_to_vif is a helper which finds the struct xenvif from a pointer
+	 * to this field.
+	 */
+	struct ubuf_info callback_struct;
+};
+
+#define XEN_NETIF_TX_RING_SIZE __CONST_RING_SIZE(xen_netif_tx, PAGE_SIZE)
+#define XEN_NETIF_RX_RING_SIZE __CONST_RING_SIZE(xen_netif_rx, PAGE_SIZE)
+
+struct xenvif_rx_meta {
+	int id;
+	int size;
+	int gso_type;
+	int gso_size;
+};
+
+#define GSO_BIT(type) \
+	(1 << XEN_NETIF_GSO_TYPE_ ## type)
+
+/* Discriminate from any valid pending_idx value. */
+#define INVALID_PENDING_IDX 0xFFFF
+
+#define MAX_BUFFER_OFFSET PAGE_SIZE
+
+#define MAX_PENDING_REQS XEN_NETIF_TX_RING_SIZE
+
+/* It's possible for an skb to have a maximal number of frags
+ * but still be less than MAX_BUFFER_OFFSET in size. Thus the
+ * worst-case number of copy operations is MAX_SKB_FRAGS per
+ * ring slot.
+ */
+#define MAX_GRANT_COPY_OPS (MAX_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE)
+
+#define NETBACK_INVALID_HANDLE -1
+
+/* To avoid confusion, we define XEN_NETBK_LEGACY_SLOTS_MAX indicating
+ * the maximum slots a valid packet can use. Now this value is defined
+ * to be XEN_NETIF_NR_SLOTS_MIN, which is supposed to be supported by
+ * all backend.
+ */
+#define XEN_NETBK_LEGACY_SLOTS_MAX XEN_NETIF_NR_SLOTS_MIN
+
+/* Queue name is interface name with "-qNNN" appended */
+#define QUEUE_NAME_SIZE (IFNAMSIZ + 5)
+
+/* IRQ name is queue name with "-tx" or "-rx" appended */
+#define IRQ_NAME_SIZE (QUEUE_NAME_SIZE + 3)
+
+struct xenvif;
+
+struct xenvif_stats {
+	/* Stats fields to be updated per-queue.
+	 * A subset of struct net_device_stats that contains only the
+	 * fields that are updated in netback.c for each queue.
+	 */
+	unsigned int rx_bytes;
+	unsigned int rx_packets;
+	unsigned int tx_bytes;
+	unsigned int tx_packets;
+
+	/* Additional stats used by xenvif */
+	unsigned long rx_gso_checksum_fixup;
+	unsigned long tx_zerocopy_sent;
+	unsigned long tx_zerocopy_success;
+	unsigned long tx_zerocopy_fail;
+	unsigned long tx_frag_overflow;
+};
+
+struct xenvif_queue { /* Per-queue data for xenvif */
+	unsigned int id; /* Queue ID, 0-based */
+	char name[QUEUE_NAME_SIZE]; /* DEVNAME-qN */
+	struct xenvif *vif; /* Parent VIF */
+
+	/* Use NAPI for guest TX */
+	struct napi_struct napi;
+	/* When feature-split-event-channels = 0, tx_irq = rx_irq. */
+	unsigned int tx_irq;
+	/* Only used when feature-split-event-channels = 1 */
+	char tx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-tx */
+	struct xen_netif_tx_back_ring tx;
+	struct sk_buff_head tx_queue;
+	struct page *mmap_pages[MAX_PENDING_REQS];
+	pending_ring_idx_t pending_prod;
+	pending_ring_idx_t pending_cons;
+	u16 pending_ring[MAX_PENDING_REQS];
+	struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
+	grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
+
+	struct gnttab_copy tx_copy_ops[MAX_PENDING_REQS];
+	struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
+	struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
+	/* passed to gnttab_[un]map_refs with pages under (un)mapping */
+	struct page *pages_to_map[MAX_PENDING_REQS];
+	struct page *pages_to_unmap[MAX_PENDING_REQS];
+
+	/* This prevents zerocopy callbacks  to race over dealloc_ring */
+	spinlock_t callback_lock;
+	/* This prevents dealloc thread and NAPI instance to race over response
+	 * creation and pending_ring in xenvif_idx_release. In xenvif_tx_err
+	 * it only protect response creation
+	 */
+	spinlock_t response_lock;
+	pending_ring_idx_t dealloc_prod;
+	pending_ring_idx_t dealloc_cons;
+	u16 dealloc_ring[MAX_PENDING_REQS];
+	struct task_struct *dealloc_task;
+	wait_queue_head_t dealloc_wq;
+	atomic_t inflight_packets;
+
+	/* Use kthread for guest RX */
+	struct task_struct *task;
+	wait_queue_head_t wq;
+	/* When feature-split-event-channels = 0, tx_irq = rx_irq. */
+	unsigned int rx_irq;
+	/* Only used when feature-split-event-channels = 1 */
+	char rx_irq_name[IRQ_NAME_SIZE]; /* DEVNAME-qN-rx */
+	struct xen_netif_rx_back_ring rx;
+	struct sk_buff_head rx_queue;
+
+	unsigned int rx_queue_max;
+	unsigned int rx_queue_len;
+	unsigned long last_rx_time;
+	bool stalled;
+
+	struct gnttab_copy grant_copy_op[MAX_GRANT_COPY_OPS];
+
+	/* We create one meta structure per ring request we consume, so
+	 * the maximum number is the same as the ring size.
+	 */
+	struct xenvif_rx_meta meta[XEN_NETIF_RX_RING_SIZE];
+
+	/* Transmit shaping: allow 'credit_bytes' every 'credit_usec'. */
+	unsigned long   credit_bytes;
+	unsigned long   credit_usec;
+	unsigned long   remaining_credit;
+	struct timer_list credit_timeout;
+	u64 credit_window_start;
+
+	/* Statistics */
+	struct xenvif_stats stats;
+};
+
+/* Maximum number of Rx slots a to-guest packet may use, including the
+ * slot needed for GSO meta-data.
+ */
+#define XEN_NETBK_RX_SLOTS_MAX (MAX_SKB_FRAGS + 1)
+
+enum state_bit_shift {
+	/* This bit marks that the vif is connected */
+	VIF_STATUS_CONNECTED,
+};
+
+struct xenvif {
+	/* Unique identifier for this interface. */
+	domid_t          domid;
+	unsigned int     handle;
+
+	u8               fe_dev_addr[6];
+
+	/* Frontend feature information. */
+	int gso_mask;
+	int gso_prefix_mask;
+
+	u8 can_sg:1;
+	u8 ip_csum:1;
+	u8 ipv6_csum:1;
+
+	/* Is this interface disabled? True when backend discovers
+	 * frontend is rogue.
+	 */
+	bool disabled;
+	unsigned long status;
+	unsigned long drain_timeout;
+	unsigned long stall_timeout;
+
+	/* Queues */
+	struct xenvif_queue *queues;
+	unsigned int num_queues; /* active queues, resource allocated */
+	unsigned int stalled_queues;
+
+	struct xenbus_watch credit_watch;
+
+	spinlock_t lock;
+
+#ifdef CONFIG_DEBUG_FS
+	struct dentry *xenvif_dbg_root;
+#endif
+
+	/* Miscellaneous private stuff. */
+	struct net_device *dev;
+};
+
+struct xenvif_rx_cb {
+	unsigned long expires;
+	int meta_slots_used;
+};
+
+#define XENVIF_RX_CB(skb) ((struct xenvif_rx_cb *)(skb)->cb)
+
+static inline struct xenbus_device *xenvif_to_xenbus_device(struct xenvif *vif)
+{
+	return to_xenbus_device(vif->dev->dev.parent);
+}
+
+void xenvif_tx_credit_callback(unsigned long data);
+
+struct xenvif *xenvif_alloc(struct device *parent,
+			    domid_t domid,
+			    unsigned int handle);
+
+int xenvif_init_queue(struct xenvif_queue *queue);
+void xenvif_deinit_queue(struct xenvif_queue *queue);
+
+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);
+void xenvif_disconnect(struct xenvif *vif);
+void xenvif_free(struct xenvif *vif);
+
+int xenvif_xenbus_init(void);
+void xenvif_xenbus_fini(void);
+
+int xenvif_schedulable(struct xenvif *vif);
+
+int xenvif_queue_stopped(struct xenvif_queue *queue);
+void xenvif_wake_queue(struct xenvif_queue *queue);
+
+/* (Un)Map communication rings. */
+void xenvif_unmap_frontend_rings(struct xenvif_queue *queue);
+int xenvif_map_frontend_rings(struct xenvif_queue *queue,
+			      grant_ref_t tx_ring_ref,
+			      grant_ref_t rx_ring_ref);
+
+/* Check for SKBs from frontend and schedule backend processing */
+void xenvif_napi_schedule_or_enable_events(struct xenvif_queue *queue);
+
+/* Prevent the device from generating any further traffic. */
+void xenvif_carrier_off(struct xenvif *vif);
+
+int xenvif_tx_action(struct xenvif_queue *queue, int budget);
+
+int xenvif_kthread_guest_rx(void *data);
+void xenvif_kick_thread(struct xenvif_queue *queue);
+
+int xenvif_dealloc_kthread(void *data);
+
+void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb);
+
+/* Determine whether the needed number of slots (req) are available,
+ * and set req_event if not.
+ */
+bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue, int needed);
+
+void xenvif_carrier_on(struct xenvif *vif);
+
+/* Callback from stack when TX packet can be released */
+void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success);
+
+/* Unmap a pending page and release it back to the guest */
+void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx);
+
+static inline pending_ring_idx_t nr_pending_reqs(struct xenvif_queue *queue)
+{
+	return MAX_PENDING_REQS -
+		queue->pending_prod + queue->pending_cons;
+}
+
+/* Callback from stack when TX packet can be released */
+void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success);
+
+irqreturn_t xenvif_interrupt(int irq, void *dev_id);
+
+extern bool separate_tx_rx_irq;
+
+extern unsigned int rx_drain_timeout_msecs;
+extern unsigned int rx_stall_timeout_msecs;
+extern unsigned int xenvif_max_queues;
+
+#ifdef CONFIG_DEBUG_FS
+extern struct dentry *xen_netback_dbg_root;
+#endif
+
+void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
+				 struct sk_buff *skb);
+void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue);
+
+#endif /* __XEN_NETBACK__COMMON_H__ */
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
new file mode 100644
index 000000000..1a83e190f
--- /dev/null
+++ b/drivers/net/xen-netback/interface.c
@@ -0,0 +1,689 @@
+/*
+ * Network-device interface management.
+ *
+ * Copyright (c) 2004-2005, Keir Fraser
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "common.h"
+
+#include <linux/kthread.h>
+#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>
+#include <xen/balloon.h>
+
+#define XENVIF_QUEUE_LENGTH 32
+#define XENVIF_NAPI_WEIGHT  64
+
+/* Number of bytes allowed on the internal guest Rx queue. */
+#define XENVIF_RX_QUEUE_BYTES (XEN_NETIF_RX_RING_SIZE/2 * PAGE_SIZE)
+
+/* This function is used to set SKBTX_DEV_ZEROCOPY as well as
+ * increasing the inflight counter. We need to increase the inflight
+ * counter because core driver calls into xenvif_zerocopy_callback
+ * which calls xenvif_skb_zerocopy_complete.
+ */
+void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
+				 struct sk_buff *skb)
+{
+	skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
+	atomic_inc(&queue->inflight_packets);
+}
+
+void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue)
+{
+	atomic_dec(&queue->inflight_packets);
+}
+
+int xenvif_schedulable(struct xenvif *vif)
+{
+	return netif_running(vif->dev) &&
+		test_bit(VIF_STATUS_CONNECTED, &vif->status) &&
+		!vif->disabled;
+}
+
+static irqreturn_t xenvif_tx_interrupt(int irq, void *dev_id)
+{
+	struct xenvif_queue *queue = dev_id;
+
+	if (RING_HAS_UNCONSUMED_REQUESTS(&queue->tx))
+		napi_schedule(&queue->napi);
+
+	return IRQ_HANDLED;
+}
+
+static int xenvif_poll(struct napi_struct *napi, int budget)
+{
+	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(queue->vif->disabled)) {
+		napi_complete(napi);
+		return 0;
+	}
+
+	work_done = xenvif_tx_action(queue, budget);
+
+	if (work_done < budget) {
+		napi_complete(napi);
+		xenvif_napi_schedule_or_enable_events(queue);
+	}
+
+	return work_done;
+}
+
+static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
+{
+	struct xenvif_queue *queue = dev_id;
+
+	xenvif_kick_thread(queue);
+
+	return IRQ_HANDLED;
+}
+
+irqreturn_t xenvif_interrupt(int irq, void *dev_id)
+{
+	xenvif_tx_interrupt(irq, dev_id);
+	xenvif_rx_interrupt(irq, dev_id);
+
+	return IRQ_HANDLED;
+}
+
+int xenvif_queue_stopped(struct xenvif_queue *queue)
+{
+	struct net_device *dev = queue->vif->dev;
+	unsigned int id = queue->id;
+	return netif_tx_queue_stopped(netdev_get_tx_queue(dev, id));
+}
+
+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));
+}
+
+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 = vif->num_queues;
+	u16 index;
+	struct xenvif_rx_cb *cb;
+
+	BUG_ON(skb->dev != dev);
+
+	/* 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;
+
+	cb = XENVIF_RX_CB(skb);
+	cb->expires = jiffies + vif->drain_timeout;
+
+	xenvif_rx_queue_tail(queue, skb);
+	xenvif_kick_thread(queue);
+
+	return NETDEV_TX_OK;
+
+ drop:
+	vif->dev->stats.tx_dropped++;
+	dev_kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+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 = vif->num_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)
+{
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->num_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)
+{
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->num_queues;
+	unsigned int queue_index;
+
+	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+		queue = &vif->queues[queue_index];
+		disable_irq(queue->tx_irq);
+		if (queue->tx_irq != queue->rx_irq)
+			disable_irq(queue->rx_irq);
+		napi_disable(&queue->napi);
+		del_timer_sync(&queue->credit_timeout);
+	}
+}
+
+static int xenvif_open(struct net_device *dev)
+{
+	struct xenvif *vif = netdev_priv(dev);
+	if (test_bit(VIF_STATUS_CONNECTED, &vif->status))
+		xenvif_up(vif);
+	netif_tx_start_all_queues(dev);
+	return 0;
+}
+
+static int xenvif_close(struct net_device *dev)
+{
+	struct xenvif *vif = netdev_priv(dev);
+	if (test_bit(VIF_STATUS_CONNECTED, &vif->status))
+		xenvif_down(vif);
+	netif_tx_stop_all_queues(dev);
+	return 0;
+}
+
+static int xenvif_change_mtu(struct net_device *dev, int mtu)
+{
+	struct xenvif *vif = netdev_priv(dev);
+	int max = vif->can_sg ? 65535 - VLAN_ETH_HLEN : ETH_DATA_LEN;
+
+	if (mtu > max)
+		return -EINVAL;
+	dev->mtu = mtu;
+	return 0;
+}
+
+static netdev_features_t xenvif_fix_features(struct net_device *dev,
+	netdev_features_t features)
+{
+	struct xenvif *vif = netdev_priv(dev);
+
+	if (!vif->can_sg)
+		features &= ~NETIF_F_SG;
+	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV4))
+		features &= ~NETIF_F_TSO;
+	if (~(vif->gso_mask | vif->gso_prefix_mask) & GSO_BIT(TCPV6))
+		features &= ~NETIF_F_TSO6;
+	if (!vif->ip_csum)
+		features &= ~NETIF_F_IP_CSUM;
+	if (!vif->ipv6_csum)
+		features &= ~NETIF_F_IPV6_CSUM;
+
+	return features;
+}
+
+static const struct xenvif_stat {
+	char name[ETH_GSTRING_LEN];
+	u16 offset;
+} xenvif_stats[] = {
+	{
+		"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_stats, tx_zerocopy_sent),
+	},
+	{
+		"tx_zerocopy_success",
+		offsetof(struct xenvif_stats, tx_zerocopy_success),
+	},
+	{
+		"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_stats, tx_frag_overflow)
+	},
+};
+
+static int xenvif_get_sset_count(struct net_device *dev, int string_set)
+{
+	switch (string_set) {
+	case ETH_SS_STATS:
+		return ARRAY_SIZE(xenvif_stats);
+	default:
+		return -EINVAL;
+	}
+}
+
+static void xenvif_get_ethtool_stats(struct net_device *dev,
+				     struct ethtool_stats *stats, u64 * data)
+{
+	struct xenvif *vif = netdev_priv(dev);
+	unsigned int num_queues = vif->num_queues;
+	int i;
+	unsigned int queue_index;
+
+	for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++) {
+		unsigned long accum = 0;
+		for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+			void *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)
+{
+	int i;
+
+	switch (stringset) {
+	case ETH_SS_STATS:
+		for (i = 0; i < ARRAY_SIZE(xenvif_stats); i++)
+			memcpy(data + i * ETH_GSTRING_LEN,
+			       xenvif_stats[i].name, ETH_GSTRING_LEN);
+		break;
+	}
+}
+
+static const struct ethtool_ops xenvif_ethtool_ops = {
+	.get_link	= ethtool_op_get_link,
+
+	.get_sset_count = xenvif_get_sset_count,
+	.get_ethtool_stats = xenvif_get_ethtool_stats,
+	.get_strings = xenvif_get_strings,
+};
+
+static const struct net_device_ops xenvif_netdev_ops = {
+	.ndo_start_xmit	= xenvif_start_xmit,
+	.ndo_get_stats	= xenvif_get_stats,
+	.ndo_open	= xenvif_open,
+	.ndo_stop	= xenvif_close,
+	.ndo_change_mtu	= xenvif_change_mtu,
+	.ndo_fix_features = xenvif_fix_features,
+	.ndo_set_mac_address = eth_mac_addr,
+	.ndo_validate_addr   = eth_validate_addr,
+};
+
+struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
+			    unsigned int handle)
+{
+	int err;
+	struct net_device *dev;
+	struct xenvif *vif;
+	char name[IFNAMSIZ] = {};
+
+	snprintf(name, IFNAMSIZ - 1, "vif%u.%u", domid, handle);
+	/* 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_*_queues().
+	 */
+	dev = alloc_netdev_mq(sizeof(struct xenvif), name, NET_NAME_UNKNOWN,
+			      ether_setup, xenvif_max_queues);
+	if (dev == NULL) {
+		pr_warn("Could not allocate netdev for %s\n", name);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	SET_NETDEV_DEV(dev, parent);
+
+	vif = netdev_priv(dev);
+
+	vif->domid  = domid;
+	vif->handle = handle;
+	vif->can_sg = 1;
+	vif->ip_csum = 1;
+	vif->dev = dev;
+	vif->disabled = false;
+	vif->drain_timeout = msecs_to_jiffies(rx_drain_timeout_msecs);
+	vif->stall_timeout = msecs_to_jiffies(rx_stall_timeout_msecs);
+
+	/* Start out with no queues. */
+	vif->queues = NULL;
+	vif->num_queues = 0;
+
+	spin_lock_init(&vif->lock);
+
+	dev->netdev_ops	= &xenvif_netdev_ops;
+	dev->hw_features = NETIF_F_SG |
+		NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
+		NETIF_F_TSO | NETIF_F_TSO6;
+	dev->features = dev->hw_features | NETIF_F_RXCSUM;
+	dev->ethtool_ops = &xenvif_ethtool_ops;
+
+	dev->tx_queue_len = XENVIF_QUEUE_LENGTH;
+
+	/*
+	 * Initialise a dummy MAC address. We choose the numerically
+	 * largest non-broadcast address to prevent the address getting
+	 * stolen by an Ethernet bridge for STP purposes.
+	 * (FE:FF:FF:FF:FF:FF)
+	 */
+	eth_broadcast_addr(dev->dev_addr);
+	dev->dev_addr[0] &= ~0x01;
+
+	netif_carrier_off(dev);
+
+	err = register_netdev(dev);
+	if (err) {
+		netdev_warn(dev, "Could not register device: err=%d\n", err);
+		free_netdev(dev);
+		return ERR_PTR(err);
+	}
+
+	netdev_dbg(dev, "Successfully created xenvif\n");
+
+	__module_get(THIS_MODULE);
+
+	return vif;
+}
+
+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_timeout.function = xenvif_tx_credit_callback;
+	queue->credit_window_start = get_jiffies_64();
+
+	queue->rx_queue_max = XENVIF_RX_QUEUE_BYTES;
+
+	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 = gnttab_alloc_pages(MAX_PENDING_REQS,
+				 queue->mmap_pages);
+	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;
+	}
+
+	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);
+	set_bit(VIF_STATUS_CONNECTED, &vif->status);
+	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(queue->tx_irq);
+	BUG_ON(queue->task);
+	BUG_ON(queue->dealloc_task);
+
+	err = xenvif_map_frontend_rings(queue, tx_ring_ref, rx_ring_ref);
+	if (err < 0)
+		goto err;
+
+	init_waitqueue_head(&queue->wq);
+	init_waitqueue_head(&queue->dealloc_wq);
+	atomic_set(&queue->inflight_packets, 0);
+
+	netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
+			XENVIF_NAPI_WEIGHT);
+
+	if (tx_evtchn == rx_evtchn) {
+		/* feature-split-event-channels == 0 */
+		err = bind_interdomain_evtchn_to_irqhandler(
+			queue->vif->domid, tx_evtchn, xenvif_interrupt, 0,
+			queue->name, queue);
+		if (err < 0)
+			goto err_unmap;
+		queue->tx_irq = queue->rx_irq = err;
+		disable_irq(queue->tx_irq);
+	} else {
+		/* feature-split-event-channels == 1 */
+		snprintf(queue->tx_irq_name, sizeof(queue->tx_irq_name),
+			 "%s-tx", queue->name);
+		err = bind_interdomain_evtchn_to_irqhandler(
+			queue->vif->domid, tx_evtchn, xenvif_tx_interrupt, 0,
+			queue->tx_irq_name, queue);
+		if (err < 0)
+			goto err_unmap;
+		queue->tx_irq = err;
+		disable_irq(queue->tx_irq);
+
+		snprintf(queue->rx_irq_name, sizeof(queue->rx_irq_name),
+			 "%s-rx", queue->name);
+		err = bind_interdomain_evtchn_to_irqhandler(
+			queue->vif->domid, rx_evtchn, xenvif_rx_interrupt, 0,
+			queue->rx_irq_name, queue);
+		if (err < 0)
+			goto err_tx_unbind;
+		queue->rx_irq = err;
+		disable_irq(queue->rx_irq);
+	}
+
+	queue->stalled = true;
+
+	task = kthread_create(xenvif_kthread_guest_rx,
+			      (void *)queue, "%s-guest-rx", queue->name);
+	if (IS_ERR(task)) {
+		pr_warn("Could not allocate kthread for %s\n", queue->name);
+		err = PTR_ERR(task);
+		goto err_rx_unbind;
+	}
+	queue->task = task;
+	get_task_struct(task);
+
+	task = kthread_create(xenvif_dealloc_kthread,
+			      (void *)queue, "%s-dealloc", queue->name);
+	if (IS_ERR(task)) {
+		pr_warn("Could not allocate kthread for %s\n", queue->name);
+		err = PTR_ERR(task);
+		goto err_rx_unbind;
+	}
+	queue->dealloc_task = task;
+
+	wake_up_process(queue->task);
+	wake_up_process(queue->dealloc_task);
+
+	return 0;
+
+err_rx_unbind:
+	unbind_from_irqhandler(queue->rx_irq, queue);
+	queue->rx_irq = 0;
+err_tx_unbind:
+	unbind_from_irqhandler(queue->tx_irq, queue);
+	queue->tx_irq = 0;
+err_unmap:
+	xenvif_unmap_frontend_rings(queue);
+err:
+	module_put(THIS_MODULE);
+	return err;
+}
+
+void xenvif_carrier_off(struct xenvif *vif)
+{
+	struct net_device *dev = vif->dev;
+
+	rtnl_lock();
+	if (test_and_clear_bit(VIF_STATUS_CONNECTED, &vif->status)) {
+		netif_carrier_off(dev); /* discard queued packets */
+		if (netif_running(dev))
+			xenvif_down(vif);
+	}
+	rtnl_unlock();
+}
+
+void xenvif_disconnect(struct xenvif *vif)
+{
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->num_queues;
+	unsigned int queue_index;
+
+	xenvif_carrier_off(vif);
+
+	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+		queue = &vif->queues[queue_index];
+
+		netif_napi_del(&queue->napi);
+
+		if (queue->task) {
+			kthread_stop(queue->task);
+			put_task_struct(queue->task);
+			queue->task = NULL;
+		}
+
+		if (queue->dealloc_task) {
+			kthread_stop(queue->dealloc_task);
+			queue->dealloc_task = NULL;
+		}
+
+		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);
+	}
+}
+
+/* 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)
+{
+	gnttab_free_pages(MAX_PENDING_REQS, queue->mmap_pages);
+}
+
+void xenvif_free(struct xenvif *vif)
+{
+	struct xenvif_queue *queue = NULL;
+	unsigned int num_queues = vif->num_queues;
+	unsigned int queue_index;
+
+	unregister_netdev(vif->dev);
+
+	for (queue_index = 0; queue_index < num_queues; ++queue_index) {
+		queue = &vif->queues[queue_index];
+		xenvif_deinit_queue(queue);
+	}
+
+	vfree(vif->queues);
+	vif->queues = NULL;
+	vif->num_queues = 0;
+
+	free_netdev(vif->dev);
+
+	module_put(THIS_MODULE);
+}
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
new file mode 100644
index 000000000..0d2594395
--- /dev/null
+++ b/drivers/net/xen-netback/netback.c
@@ -0,0 +1,2049 @@
+/*
+ * Back-end of the driver for virtual network devices. This portion of the
+ * driver exports a 'unified' network-device interface that can be accessed
+ * by any operating system that implements a compatible front end. A
+ * reference front-end implementation can be found in:
+ *  drivers/net/xen-netfront.c
+ *
+ * Copyright (c) 2002-2005, K A Fraser
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "common.h"
+
+#include <linux/kthread.h>
+#include <linux/if_vlan.h>
+#include <linux/udp.h>
+#include <linux/highmem.h>
+
+#include <net/tcp.h>
+
+#include <xen/xen.h>
+#include <xen/events.h>
+#include <xen/interface/memory.h>
+
+#include <asm/xen/hypercall.h>
+#include <asm/xen/page.h>
+
+/* Provide an option to disable split event channels at load time as
+ * event channels are limited resource. Split event channels are
+ * enabled by default.
+ */
+bool separate_tx_rx_irq = 1;
+module_param(separate_tx_rx_irq, bool, 0644);
+
+/* The time that packets can stay on the guest Rx internal queue
+ * before they are dropped.
+ */
+unsigned int rx_drain_timeout_msecs = 10000;
+module_param(rx_drain_timeout_msecs, uint, 0444);
+
+/* The length of time before the frontend is considered unresponsive
+ * because it isn't providing Rx slots.
+ */
+unsigned int rx_stall_timeout_msecs = 60000;
+module_param(rx_stall_timeout_msecs, uint, 0444);
+
+unsigned int xenvif_max_queues;
+module_param_named(max_queues, xenvif_max_queues, uint, 0644);
+MODULE_PARM_DESC(max_queues,
+		 "Maximum number of queues per virtual interface");
+
+/*
+ * This is the maximum slots a skb can have. If a guest sends a skb
+ * which exceeds this limit it is considered malicious.
+ */
+#define FATAL_SKB_SLOTS_DEFAULT 20
+static unsigned int fatal_skb_slots = FATAL_SKB_SLOTS_DEFAULT;
+module_param(fatal_skb_slots, uint, 0444);
+
+/* The amount to copy out of the first guest Tx slot into the skb's
+ * linear area.  If the first slot has more data, it will be mapped
+ * and put into the first frag.
+ *
+ * This is sized to avoid pulling headers from the frags for most
+ * TCP/IP packets.
+ */
+#define XEN_NETBACK_TX_COPY_LEN 128
+
+
+static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx,
+			       u8 status);
+
+static void make_tx_response(struct xenvif_queue *queue,
+			     struct xen_netif_tx_request *txp,
+			     s8       st);
+static void push_tx_responses(struct xenvif_queue *queue);
+
+static inline int tx_work_todo(struct xenvif_queue *queue);
+
+static struct xen_netif_rx_response *make_rx_response(struct xenvif_queue *queue,
+					     u16      id,
+					     s8       st,
+					     u16      offset,
+					     u16      size,
+					     u16      flags);
+
+static inline unsigned long idx_to_pfn(struct xenvif_queue *queue,
+				       u16 idx)
+{
+	return page_to_pfn(queue->mmap_pages[idx]);
+}
+
+static inline unsigned long idx_to_kaddr(struct xenvif_queue *queue,
+					 u16 idx)
+{
+	return (unsigned long)pfn_to_kaddr(idx_to_pfn(queue, idx));
+}
+
+#define callback_param(vif, pending_idx) \
+	(vif->pending_tx_info[pending_idx].callback_struct)
+
+/* Find the containing VIF's structure from a pointer in pending_tx_info array
+ */
+static inline struct xenvif_queue *ubuf_to_queue(const struct ubuf_info *ubuf)
+{
+	u16 pending_idx = ubuf->desc;
+	struct pending_tx_info *temp =
+		container_of(ubuf, struct pending_tx_info, callback_struct);
+	return container_of(temp - pending_idx,
+			    struct xenvif_queue,
+			    pending_tx_info[0]);
+}
+
+static u16 frag_get_pending_idx(skb_frag_t *frag)
+{
+	return (u16)frag->page_offset;
+}
+
+static void frag_set_pending_idx(skb_frag_t *frag, u16 pending_idx)
+{
+	frag->page_offset = pending_idx;
+}
+
+static inline pending_ring_idx_t pending_index(unsigned i)
+{
+	return i & (MAX_PENDING_REQS-1);
+}
+
+bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue, int needed)
+{
+	RING_IDX prod, cons;
+
+	do {
+		prod = queue->rx.sring->req_prod;
+		cons = queue->rx.req_cons;
+
+		if (prod - cons >= needed)
+			return true;
+
+		queue->rx.sring->req_event = prod + 1;
+
+		/* Make sure event is visible before we check prod
+		 * again.
+		 */
+		mb();
+	} while (queue->rx.sring->req_prod != prod);
+
+	return false;
+}
+
+void xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&queue->rx_queue.lock, flags);
+
+	__skb_queue_tail(&queue->rx_queue, skb);
+
+	queue->rx_queue_len += skb->len;
+	if (queue->rx_queue_len > queue->rx_queue_max)
+		netif_tx_stop_queue(netdev_get_tx_queue(queue->vif->dev, queue->id));
+
+	spin_unlock_irqrestore(&queue->rx_queue.lock, flags);
+}
+
+static struct sk_buff *xenvif_rx_dequeue(struct xenvif_queue *queue)
+{
+	struct sk_buff *skb;
+
+	spin_lock_irq(&queue->rx_queue.lock);
+
+	skb = __skb_dequeue(&queue->rx_queue);
+	if (skb)
+		queue->rx_queue_len -= skb->len;
+
+	spin_unlock_irq(&queue->rx_queue.lock);
+
+	return skb;
+}
+
+static void xenvif_rx_queue_maybe_wake(struct xenvif_queue *queue)
+{
+	spin_lock_irq(&queue->rx_queue.lock);
+
+	if (queue->rx_queue_len < queue->rx_queue_max)
+		netif_tx_wake_queue(netdev_get_tx_queue(queue->vif->dev, queue->id));
+
+	spin_unlock_irq(&queue->rx_queue.lock);
+}
+
+
+static void xenvif_rx_queue_purge(struct xenvif_queue *queue)
+{
+	struct sk_buff *skb;
+	while ((skb = xenvif_rx_dequeue(queue)) != NULL)
+		kfree_skb(skb);
+}
+
+static void xenvif_rx_queue_drop_expired(struct xenvif_queue *queue)
+{
+	struct sk_buff *skb;
+
+	for(;;) {
+		skb = skb_peek(&queue->rx_queue);
+		if (!skb)
+			break;
+		if (time_before(jiffies, XENVIF_RX_CB(skb)->expires))
+			break;
+		xenvif_rx_dequeue(queue);
+		kfree_skb(skb);
+	}
+}
+
+struct netrx_pending_operations {
+	unsigned copy_prod, copy_cons;
+	unsigned meta_prod, meta_cons;
+	struct gnttab_copy *copy;
+	struct xenvif_rx_meta *meta;
+	int copy_off;
+	grant_ref_t copy_gref;
+};
+
+static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif_queue *queue,
+						 struct netrx_pending_operations *npo)
+{
+	struct xenvif_rx_meta *meta;
+	struct xen_netif_rx_request *req;
+
+	req = RING_GET_REQUEST(&queue->rx, queue->rx.req_cons++);
+
+	meta = npo->meta + npo->meta_prod++;
+	meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;
+	meta->gso_size = 0;
+	meta->size = 0;
+	meta->id = req->id;
+
+	npo->copy_off = 0;
+	npo->copy_gref = req->gref;
+
+	return meta;
+}
+
+/*
+ * Set up the grant operations for this fragment. If it's a flipping
+ * interface, we also set up the unmap request from here.
+ */
+static void xenvif_gop_frag_copy(struct xenvif_queue *queue, struct sk_buff *skb,
+				 struct netrx_pending_operations *npo,
+				 struct page *page, unsigned long size,
+				 unsigned long offset, int *head)
+{
+	struct gnttab_copy *copy_gop;
+	struct xenvif_rx_meta *meta;
+	unsigned long bytes;
+	int gso_type = XEN_NETIF_GSO_TYPE_NONE;
+
+	/* Data must not cross a page boundary. */
+	BUG_ON(size + offset > PAGE_SIZE<<compound_order(page));
+
+	meta = npo->meta + npo->meta_prod - 1;
+
+	/* Skip unused frames from start of page */
+	page += offset >> PAGE_SHIFT;
+	offset &= ~PAGE_MASK;
+
+	while (size > 0) {
+		struct xen_page_foreign *foreign;
+
+		BUG_ON(offset >= PAGE_SIZE);
+		BUG_ON(npo->copy_off > MAX_BUFFER_OFFSET);
+
+		if (npo->copy_off == MAX_BUFFER_OFFSET)
+			meta = get_next_rx_buffer(queue, npo);
+
+		bytes = PAGE_SIZE - offset;
+		if (bytes > size)
+			bytes = size;
+
+		if (npo->copy_off + bytes > MAX_BUFFER_OFFSET)
+			bytes = MAX_BUFFER_OFFSET - npo->copy_off;
+
+		copy_gop = npo->copy + npo->copy_prod++;
+		copy_gop->flags = GNTCOPY_dest_gref;
+		copy_gop->len = bytes;
+
+		foreign = xen_page_foreign(page);
+		if (foreign) {
+			copy_gop->source.domid = foreign->domid;
+			copy_gop->source.u.ref = foreign->gref;
+			copy_gop->flags |= GNTCOPY_source_gref;
+		} else {
+			copy_gop->source.domid = DOMID_SELF;
+			copy_gop->source.u.gmfn =
+				virt_to_mfn(page_address(page));
+		}
+		copy_gop->source.offset = offset;
+
+		copy_gop->dest.domid = queue->vif->domid;
+		copy_gop->dest.offset = npo->copy_off;
+		copy_gop->dest.u.ref = npo->copy_gref;
+
+		npo->copy_off += bytes;
+		meta->size += bytes;
+
+		offset += bytes;
+		size -= bytes;
+
+		/* Next frame */
+		if (offset == PAGE_SIZE && size) {
+			BUG_ON(!PageCompound(page));
+			page++;
+			offset = 0;
+		}
+
+		/* Leave a gap for the GSO descriptor. */
+		if (skb_is_gso(skb)) {
+			if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+				gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
+			else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+				gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
+		}
+
+		if (*head && ((1 << gso_type) & queue->vif->gso_mask))
+			queue->rx.req_cons++;
+
+		*head = 0; /* There must be something in this buffer now. */
+
+	}
+}
+
+/*
+ * Prepare an SKB to be transmitted to the frontend.
+ *
+ * This function is responsible for allocating grant operations, meta
+ * structures, etc.
+ *
+ * It returns the number of meta structures consumed. The number of
+ * ring slots used is always equal to the number of meta slots used
+ * plus the number of GSO descriptors used. Currently, we use either
+ * zero GSO descriptors (for non-GSO packets) or one descriptor (for
+ * frontend-side LRO).
+ */
+static int xenvif_gop_skb(struct sk_buff *skb,
+			  struct netrx_pending_operations *npo,
+			  struct xenvif_queue *queue)
+{
+	struct xenvif *vif = netdev_priv(skb->dev);
+	int nr_frags = skb_shinfo(skb)->nr_frags;
+	int i;
+	struct xen_netif_rx_request *req;
+	struct xenvif_rx_meta *meta;
+	unsigned char *data;
+	int head = 1;
+	int old_meta_prod;
+	int gso_type;
+
+	old_meta_prod = npo->meta_prod;
+
+	gso_type = XEN_NETIF_GSO_TYPE_NONE;
+	if (skb_is_gso(skb)) {
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+			gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
+		else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+			gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
+	}
+
+	/* Set up a GSO prefix descriptor, if necessary */
+	if ((1 << gso_type) & vif->gso_prefix_mask) {
+		req = RING_GET_REQUEST(&queue->rx, queue->rx.req_cons++);
+		meta = npo->meta + npo->meta_prod++;
+		meta->gso_type = gso_type;
+		meta->gso_size = skb_shinfo(skb)->gso_size;
+		meta->size = 0;
+		meta->id = req->id;
+	}
+
+	req = RING_GET_REQUEST(&queue->rx, queue->rx.req_cons++);
+	meta = npo->meta + npo->meta_prod++;
+
+	if ((1 << gso_type) & vif->gso_mask) {
+		meta->gso_type = gso_type;
+		meta->gso_size = skb_shinfo(skb)->gso_size;
+	} else {
+		meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;
+		meta->gso_size = 0;
+	}
+
+	meta->size = 0;
+	meta->id = req->id;
+	npo->copy_off = 0;
+	npo->copy_gref = req->gref;
+
+	data = skb->data;
+	while (data < skb_tail_pointer(skb)) {
+		unsigned int offset = offset_in_page(data);
+		unsigned int len = PAGE_SIZE - offset;
+
+		if (data + len > skb_tail_pointer(skb))
+			len = skb_tail_pointer(skb) - data;
+
+		xenvif_gop_frag_copy(queue, skb, npo,
+				     virt_to_page(data), len, offset, &head);
+		data += len;
+	}
+
+	for (i = 0; i < nr_frags; i++) {
+		xenvif_gop_frag_copy(queue, skb, npo,
+				     skb_frag_page(&skb_shinfo(skb)->frags[i]),
+				     skb_frag_size(&skb_shinfo(skb)->frags[i]),
+				     skb_shinfo(skb)->frags[i].page_offset,
+				     &head);
+	}
+
+	return npo->meta_prod - old_meta_prod;
+}
+
+/*
+ * This is a twin to xenvif_gop_skb.  Assume that xenvif_gop_skb was
+ * used to set up the operations on the top of
+ * netrx_pending_operations, which have since been done.  Check that
+ * they didn't give any errors and advance over them.
+ */
+static int xenvif_check_gop(struct xenvif *vif, int nr_meta_slots,
+			    struct netrx_pending_operations *npo)
+{
+	struct gnttab_copy     *copy_op;
+	int status = XEN_NETIF_RSP_OKAY;
+	int i;
+
+	for (i = 0; i < nr_meta_slots; i++) {
+		copy_op = npo->copy + npo->copy_cons++;
+		if (copy_op->status != GNTST_okay) {
+			netdev_dbg(vif->dev,
+				   "Bad status %d from copy to DOM%d.\n",
+				   copy_op->status, vif->domid);
+			status = XEN_NETIF_RSP_ERROR;
+		}
+	}
+
+	return status;
+}
+
+static void xenvif_add_frag_responses(struct xenvif_queue *queue, int status,
+				      struct xenvif_rx_meta *meta,
+				      int nr_meta_slots)
+{
+	int i;
+	unsigned long offset;
+
+	/* No fragments used */
+	if (nr_meta_slots <= 1)
+		return;
+
+	nr_meta_slots--;
+
+	for (i = 0; i < nr_meta_slots; i++) {
+		int flags;
+		if (i == nr_meta_slots - 1)
+			flags = 0;
+		else
+			flags = XEN_NETRXF_more_data;
+
+		offset = 0;
+		make_rx_response(queue, meta[i].id, status, offset,
+				 meta[i].size, flags);
+	}
+}
+
+void xenvif_kick_thread(struct xenvif_queue *queue)
+{
+	wake_up(&queue->wq);
+}
+
+static void xenvif_rx_action(struct xenvif_queue *queue)
+{
+	s8 status;
+	u16 flags;
+	struct xen_netif_rx_response *resp;
+	struct sk_buff_head rxq;
+	struct sk_buff *skb;
+	LIST_HEAD(notify);
+	int ret;
+	unsigned long offset;
+	bool need_to_notify = false;
+
+	struct netrx_pending_operations npo = {
+		.copy  = queue->grant_copy_op,
+		.meta  = queue->meta,
+	};
+
+	skb_queue_head_init(&rxq);
+
+	while (xenvif_rx_ring_slots_available(queue, XEN_NETBK_RX_SLOTS_MAX)
+	       && (skb = xenvif_rx_dequeue(queue)) != NULL) {
+		RING_IDX old_req_cons;
+		RING_IDX ring_slots_used;
+
+		queue->last_rx_time = jiffies;
+
+		old_req_cons = queue->rx.req_cons;
+		XENVIF_RX_CB(skb)->meta_slots_used = xenvif_gop_skb(skb, &npo, queue);
+		ring_slots_used = queue->rx.req_cons - old_req_cons;
+
+		__skb_queue_tail(&rxq, skb);
+	}
+
+	BUG_ON(npo.meta_prod > ARRAY_SIZE(queue->meta));
+
+	if (!npo.copy_prod)
+		goto done;
+
+	BUG_ON(npo.copy_prod > MAX_GRANT_COPY_OPS);
+	gnttab_batch_copy(queue->grant_copy_op, npo.copy_prod);
+
+	while ((skb = __skb_dequeue(&rxq)) != NULL) {
+
+		if ((1 << queue->meta[npo.meta_cons].gso_type) &
+		    queue->vif->gso_prefix_mask) {
+			resp = RING_GET_RESPONSE(&queue->rx,
+						 queue->rx.rsp_prod_pvt++);
+
+			resp->flags = XEN_NETRXF_gso_prefix | XEN_NETRXF_more_data;
+
+			resp->offset = queue->meta[npo.meta_cons].gso_size;
+			resp->id = queue->meta[npo.meta_cons].id;
+			resp->status = XENVIF_RX_CB(skb)->meta_slots_used;
+
+			npo.meta_cons++;
+			XENVIF_RX_CB(skb)->meta_slots_used--;
+		}
+
+
+		queue->stats.tx_bytes += skb->len;
+		queue->stats.tx_packets++;
+
+		status = xenvif_check_gop(queue->vif,
+					  XENVIF_RX_CB(skb)->meta_slots_used,
+					  &npo);
+
+		if (XENVIF_RX_CB(skb)->meta_slots_used == 1)
+			flags = 0;
+		else
+			flags = XEN_NETRXF_more_data;
+
+		if (skb->ip_summed == CHECKSUM_PARTIAL) /* local packet? */
+			flags |= XEN_NETRXF_csum_blank | XEN_NETRXF_data_validated;
+		else if (skb->ip_summed == CHECKSUM_UNNECESSARY)
+			/* remote but checksummed. */
+			flags |= XEN_NETRXF_data_validated;
+
+		offset = 0;
+		resp = make_rx_response(queue, queue->meta[npo.meta_cons].id,
+					status, offset,
+					queue->meta[npo.meta_cons].size,
+					flags);
+
+		if ((1 << queue->meta[npo.meta_cons].gso_type) &
+		    queue->vif->gso_mask) {
+			struct xen_netif_extra_info *gso =
+				(struct xen_netif_extra_info *)
+				RING_GET_RESPONSE(&queue->rx,
+						  queue->rx.rsp_prod_pvt++);
+
+			resp->flags |= XEN_NETRXF_extra_info;
+
+			gso->u.gso.type = queue->meta[npo.meta_cons].gso_type;
+			gso->u.gso.size = queue->meta[npo.meta_cons].gso_size;
+			gso->u.gso.pad = 0;
+			gso->u.gso.features = 0;
+
+			gso->type = XEN_NETIF_EXTRA_TYPE_GSO;
+			gso->flags = 0;
+		}
+
+		xenvif_add_frag_responses(queue, status,
+					  queue->meta + npo.meta_cons + 1,
+					  XENVIF_RX_CB(skb)->meta_slots_used);
+
+		RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->rx, ret);
+
+		need_to_notify |= !!ret;
+
+		npo.meta_cons += XENVIF_RX_CB(skb)->meta_slots_used;
+		dev_kfree_skb(skb);
+	}
+
+done:
+	if (need_to_notify)
+		notify_remote_via_irq(queue->rx_irq);
+}
+
+void xenvif_napi_schedule_or_enable_events(struct xenvif_queue *queue)
+{
+	int more_to_do;
+
+	RING_FINAL_CHECK_FOR_REQUESTS(&queue->tx, more_to_do);
+
+	if (more_to_do)
+		napi_schedule(&queue->napi);
+}
+
+static void tx_add_credit(struct xenvif_queue *queue)
+{
+	unsigned long max_burst, max_credit;
+
+	/*
+	 * Allow a burst big enough to transmit a jumbo packet of up to 128kB.
+	 * Otherwise the interface can seize up due to insufficient credit.
+	 */
+	max_burst = RING_GET_REQUEST(&queue->tx, queue->tx.req_cons)->size;
+	max_burst = min(max_burst, 131072UL);
+	max_burst = max(max_burst, queue->credit_bytes);
+
+	/* Take care that adding a new chunk of credit doesn't wrap to zero. */
+	max_credit = queue->remaining_credit + queue->credit_bytes;
+	if (max_credit < queue->remaining_credit)
+		max_credit = ULONG_MAX; /* wrapped: clamp to ULONG_MAX */
+
+	queue->remaining_credit = min(max_credit, max_burst);
+}
+
+void xenvif_tx_credit_callback(unsigned long data)
+{
+	struct xenvif_queue *queue = (struct xenvif_queue *)data;
+	tx_add_credit(queue);
+	xenvif_napi_schedule_or_enable_events(queue);
+}
+
+static void xenvif_tx_err(struct xenvif_queue *queue,
+			  struct xen_netif_tx_request *txp, RING_IDX end)
+{
+	RING_IDX cons = queue->tx.req_cons;
+	unsigned long flags;
+
+	do {
+		spin_lock_irqsave(&queue->response_lock, flags);
+		make_tx_response(queue, txp, XEN_NETIF_RSP_ERROR);
+		push_tx_responses(queue);
+		spin_unlock_irqrestore(&queue->response_lock, flags);
+		if (cons == end)
+			break;
+		txp = RING_GET_REQUEST(&queue->tx, cons++);
+	} while (1);
+	queue->tx.req_cons = cons;
+}
+
+static void xenvif_fatal_tx_err(struct xenvif *vif)
+{
+	netdev_err(vif->dev, "fatal error; disabling device\n");
+	vif->disabled = true;
+	/* Disable the vif from queue 0's kthread */
+	if (vif->queues)
+		xenvif_kick_thread(&vif->queues[0]);
+}
+
+static int xenvif_count_requests(struct xenvif_queue *queue,
+				 struct xen_netif_tx_request *first,
+				 struct xen_netif_tx_request *txp,
+				 int work_to_do)
+{
+	RING_IDX cons = queue->tx.req_cons;
+	int slots = 0;
+	int drop_err = 0;
+	int more_data;
+
+	if (!(first->flags & XEN_NETTXF_more_data))
+		return 0;
+
+	do {
+		struct xen_netif_tx_request dropped_tx = { 0 };
+
+		if (slots >= work_to_do) {
+			netdev_err(queue->vif->dev,
+				   "Asked for %d slots but exceeds this limit\n",
+				   work_to_do);
+			xenvif_fatal_tx_err(queue->vif);
+			return -ENODATA;
+		}
+
+		/* This guest is really using too many slots and
+		 * considered malicious.
+		 */
+		if (unlikely(slots >= fatal_skb_slots)) {
+			netdev_err(queue->vif->dev,
+				   "Malicious frontend using %d slots, threshold %u\n",
+				   slots, fatal_skb_slots);
+			xenvif_fatal_tx_err(queue->vif);
+			return -E2BIG;
+		}
+
+		/* Xen network protocol had implicit dependency on
+		 * MAX_SKB_FRAGS. XEN_NETBK_LEGACY_SLOTS_MAX is set to
+		 * the historical MAX_SKB_FRAGS value 18 to honor the
+		 * same behavior as before. Any packet using more than
+		 * 18 slots but less than fatal_skb_slots slots is
+		 * dropped
+		 */
+		if (!drop_err && slots >= XEN_NETBK_LEGACY_SLOTS_MAX) {
+			if (net_ratelimit())
+				netdev_dbg(queue->vif->dev,
+					   "Too many slots (%d) exceeding limit (%d), dropping packet\n",
+					   slots, XEN_NETBK_LEGACY_SLOTS_MAX);
+			drop_err = -E2BIG;
+		}
+
+		if (drop_err)
+			txp = &dropped_tx;
+
+		memcpy(txp, RING_GET_REQUEST(&queue->tx, cons + slots),
+		       sizeof(*txp));
+
+		/* If the guest submitted a frame >= 64 KiB then
+		 * first->size overflowed and following slots will
+		 * appear to be larger than the frame.
+		 *
+		 * This cannot be fatal error as there are buggy
+		 * frontends that do this.
+		 *
+		 * Consume all slots and drop the packet.
+		 */
+		if (!drop_err && txp->size > first->size) {
+			if (net_ratelimit())
+				netdev_dbg(queue->vif->dev,
+					   "Invalid tx request, slot size %u > remaining size %u\n",
+					   txp->size, first->size);
+			drop_err = -EIO;
+		}
+
+		first->size -= txp->size;
+		slots++;
+
+		if (unlikely((txp->offset + txp->size) > PAGE_SIZE)) {
+			netdev_err(queue->vif->dev, "Cross page boundary, txp->offset: %x, size: %u\n",
+				 txp->offset, txp->size);
+			xenvif_fatal_tx_err(queue->vif);
+			return -EINVAL;
+		}
+
+		more_data = txp->flags & XEN_NETTXF_more_data;
+
+		if (!drop_err)
+			txp++;
+
+	} while (more_data);
+
+	if (drop_err) {
+		xenvif_tx_err(queue, first, cons + slots);
+		return drop_err;
+	}
+
+	return slots;
+}
+
+
+struct xenvif_tx_cb {
+	u16 pending_idx;
+};
+
+#define XENVIF_TX_CB(skb) ((struct xenvif_tx_cb *)(skb)->cb)
+
+static inline void xenvif_tx_create_map_op(struct xenvif_queue *queue,
+					  u16 pending_idx,
+					  struct xen_netif_tx_request *txp,
+					  struct gnttab_map_grant_ref *mop)
+{
+	queue->pages_to_map[mop-queue->tx_map_ops] = queue->mmap_pages[pending_idx];
+	gnttab_set_map_op(mop, idx_to_kaddr(queue, pending_idx),
+			  GNTMAP_host_map | GNTMAP_readonly,
+			  txp->gref, queue->vif->domid);
+
+	memcpy(&queue->pending_tx_info[pending_idx].req, txp,
+	       sizeof(*txp));
+}
+
+static inline struct sk_buff *xenvif_alloc_skb(unsigned int size)
+{
+	struct sk_buff *skb =
+		alloc_skb(size + NET_SKB_PAD + NET_IP_ALIGN,
+			  GFP_ATOMIC | __GFP_NOWARN);
+	if (unlikely(skb == NULL))
+		return NULL;
+
+	/* Packets passed to netif_rx() must have some headroom. */
+	skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
+
+	/* Initialize it here to avoid later surprises */
+	skb_shinfo(skb)->destructor_arg = NULL;
+
+	return skb;
+}
+
+static struct gnttab_map_grant_ref *xenvif_get_requests(struct xenvif_queue *queue,
+							struct sk_buff *skb,
+							struct xen_netif_tx_request *txp,
+							struct gnttab_map_grant_ref *gop)
+{
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	skb_frag_t *frags = shinfo->frags;
+	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
+	int start;
+	pending_ring_idx_t index;
+	unsigned int nr_slots, frag_overflow = 0;
+
+	/* At this point shinfo->nr_frags is in fact the number of
+	 * slots, which can be as large as XEN_NETBK_LEGACY_SLOTS_MAX.
+	 */
+	if (shinfo->nr_frags > MAX_SKB_FRAGS) {
+		frag_overflow = shinfo->nr_frags - MAX_SKB_FRAGS;
+		BUG_ON(frag_overflow > MAX_SKB_FRAGS);
+		shinfo->nr_frags = MAX_SKB_FRAGS;
+	}
+	nr_slots = shinfo->nr_frags;
+
+	/* Skip first skb fragment if it is on same page as header fragment. */
+	start = (frag_get_pending_idx(&shinfo->frags[0]) == pending_idx);
+
+	for (shinfo->nr_frags = start; shinfo->nr_frags < nr_slots;
+	     shinfo->nr_frags++, txp++, gop++) {
+		index = pending_index(queue->pending_cons++);
+		pending_idx = queue->pending_ring[index];
+		xenvif_tx_create_map_op(queue, pending_idx, txp, gop);
+		frag_set_pending_idx(&frags[shinfo->nr_frags], pending_idx);
+	}
+
+	if (frag_overflow) {
+		struct sk_buff *nskb = xenvif_alloc_skb(0);
+		if (unlikely(nskb == NULL)) {
+			if (net_ratelimit())
+				netdev_err(queue->vif->dev,
+					   "Can't allocate the frag_list skb.\n");
+			return NULL;
+		}
+
+		shinfo = skb_shinfo(nskb);
+		frags = shinfo->frags;
+
+		for (shinfo->nr_frags = 0; shinfo->nr_frags < frag_overflow;
+		     shinfo->nr_frags++, txp++, gop++) {
+			index = pending_index(queue->pending_cons++);
+			pending_idx = queue->pending_ring[index];
+			xenvif_tx_create_map_op(queue, pending_idx, txp, gop);
+			frag_set_pending_idx(&frags[shinfo->nr_frags],
+					     pending_idx);
+		}
+
+		skb_shinfo(skb)->frag_list = nskb;
+	}
+
+	return gop;
+}
+
+static inline void xenvif_grant_handle_set(struct xenvif_queue *queue,
+					   u16 pending_idx,
+					   grant_handle_t handle)
+{
+	if (unlikely(queue->grant_tx_handle[pending_idx] !=
+		     NETBACK_INVALID_HANDLE)) {
+		netdev_err(queue->vif->dev,
+			   "Trying to overwrite active handle! pending_idx: %x\n",
+			   pending_idx);
+		BUG();
+	}
+	queue->grant_tx_handle[pending_idx] = handle;
+}
+
+static inline void xenvif_grant_handle_reset(struct xenvif_queue *queue,
+					     u16 pending_idx)
+{
+	if (unlikely(queue->grant_tx_handle[pending_idx] ==
+		     NETBACK_INVALID_HANDLE)) {
+		netdev_err(queue->vif->dev,
+			   "Trying to unmap invalid handle! pending_idx: %x\n",
+			   pending_idx);
+		BUG();
+	}
+	queue->grant_tx_handle[pending_idx] = NETBACK_INVALID_HANDLE;
+}
+
+static int xenvif_tx_check_gop(struct xenvif_queue *queue,
+			       struct sk_buff *skb,
+			       struct gnttab_map_grant_ref **gopp_map,
+			       struct gnttab_copy **gopp_copy)
+{
+	struct gnttab_map_grant_ref *gop_map = *gopp_map;
+	u16 pending_idx = XENVIF_TX_CB(skb)->pending_idx;
+	/* This always points to the shinfo of the skb being checked, which
+	 * could be either the first or the one on the frag_list
+	 */
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	/* If this is non-NULL, we are currently checking the frag_list skb, and
+	 * this points to the shinfo of the first one
+	 */
+	struct skb_shared_info *first_shinfo = NULL;
+	int nr_frags = shinfo->nr_frags;
+	const bool sharedslot = nr_frags &&
+				frag_get_pending_idx(&shinfo->frags[0]) == pending_idx;
+	int i, err;
+
+	/* Check status of header. */
+	err = (*gopp_copy)->status;
+	if (unlikely(err)) {
+		if (net_ratelimit())
+			netdev_dbg(queue->vif->dev,
+				   "Grant copy of header failed! status: %d pending_idx: %u ref: %u\n",
+				   (*gopp_copy)->status,
+				   pending_idx,
+				   (*gopp_copy)->source.u.ref);
+		/* The first frag might still have this slot mapped */
+		if (!sharedslot)
+			xenvif_idx_release(queue, pending_idx,
+					   XEN_NETIF_RSP_ERROR);
+	}
+	(*gopp_copy)++;
+
+check_frags:
+	for (i = 0; i < nr_frags; i++, gop_map++) {
+		int j, newerr;
+
+		pending_idx = frag_get_pending_idx(&shinfo->frags[i]);
+
+		/* Check error status: if okay then remember grant handle. */
+		newerr = gop_map->status;
+
+		if (likely(!newerr)) {
+			xenvif_grant_handle_set(queue,
+						pending_idx,
+						gop_map->handle);
+			/* Had a previous error? Invalidate this fragment. */
+			if (unlikely(err)) {
+				xenvif_idx_unmap(queue, pending_idx);
+				/* If the mapping of the first frag was OK, but
+				 * the header's copy failed, and they are
+				 * sharing a slot, send an error
+				 */
+				if (i == 0 && sharedslot)
+					xenvif_idx_release(queue, pending_idx,
+							   XEN_NETIF_RSP_ERROR);
+				else
+					xenvif_idx_release(queue, pending_idx,
+							   XEN_NETIF_RSP_OKAY);
+			}
+			continue;
+		}
+
+		/* Error on this fragment: respond to client with an error. */
+		if (net_ratelimit())
+			netdev_dbg(queue->vif->dev,
+				   "Grant map of %d. frag failed! status: %d pending_idx: %u ref: %u\n",
+				   i,
+				   gop_map->status,
+				   pending_idx,
+				   gop_map->ref);
+
+		xenvif_idx_release(queue, pending_idx, XEN_NETIF_RSP_ERROR);
+
+		/* Not the first error? Preceding frags already invalidated. */
+		if (err)
+			continue;
+
+		/* First error: if the header haven't shared a slot with the
+		 * first frag, release it as well.
+		 */
+		if (!sharedslot)
+			xenvif_idx_release(queue,
+					   XENVIF_TX_CB(skb)->pending_idx,
+					   XEN_NETIF_RSP_OKAY);
+
+		/* Invalidate preceding fragments of this skb. */
+		for (j = 0; j < i; j++) {
+			pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
+			xenvif_idx_unmap(queue, pending_idx);
+			xenvif_idx_release(queue, pending_idx,
+					   XEN_NETIF_RSP_OKAY);
+		}
+
+		/* And if we found the error while checking the frag_list, unmap
+		 * the first skb's frags
+		 */
+		if (first_shinfo) {
+			for (j = 0; j < first_shinfo->nr_frags; j++) {
+				pending_idx = frag_get_pending_idx(&first_shinfo->frags[j]);
+				xenvif_idx_unmap(queue, pending_idx);
+				xenvif_idx_release(queue, pending_idx,
+						   XEN_NETIF_RSP_OKAY);
+			}
+		}
+
+		/* Remember the error: invalidate all subsequent fragments. */
+		err = newerr;
+	}
+
+	if (skb_has_frag_list(skb) && !first_shinfo) {
+		first_shinfo = skb_shinfo(skb);
+		shinfo = skb_shinfo(skb_shinfo(skb)->frag_list);
+		nr_frags = shinfo->nr_frags;
+
+		goto check_frags;
+	}
+
+	*gopp_map = gop_map;
+	return err;
+}
+
+static void xenvif_fill_frags(struct xenvif_queue *queue, struct sk_buff *skb)
+{
+	struct skb_shared_info *shinfo = skb_shinfo(skb);
+	int nr_frags = shinfo->nr_frags;
+	int i;
+	u16 prev_pending_idx = INVALID_PENDING_IDX;
+
+	for (i = 0; i < nr_frags; i++) {
+		skb_frag_t *frag = shinfo->frags + i;
+		struct xen_netif_tx_request *txp;
+		struct page *page;
+		u16 pending_idx;
+
+		pending_idx = frag_get_pending_idx(frag);
+
+		/* If this is not the first frag, chain it to the previous*/
+		if (prev_pending_idx == INVALID_PENDING_IDX)
+			skb_shinfo(skb)->destructor_arg =
+				&callback_param(queue, pending_idx);
+		else
+			callback_param(queue, prev_pending_idx).ctx =
+				&callback_param(queue, pending_idx);
+
+		callback_param(queue, pending_idx).ctx = NULL;
+		prev_pending_idx = pending_idx;
+
+		txp = &queue->pending_tx_info[pending_idx].req;
+		page = virt_to_page(idx_to_kaddr(queue, pending_idx));
+		__skb_fill_page_desc(skb, i, page, txp->offset, txp->size);
+		skb->len += txp->size;
+		skb->data_len += txp->size;
+		skb->truesize += txp->size;
+
+		/* Take an extra reference to offset network stack's put_page */
+		get_page(queue->mmap_pages[pending_idx]);
+	}
+}
+
+static int xenvif_get_extras(struct xenvif_queue *queue,
+				struct xen_netif_extra_info *extras,
+				int work_to_do)
+{
+	struct xen_netif_extra_info extra;
+	RING_IDX cons = queue->tx.req_cons;
+
+	do {
+		if (unlikely(work_to_do-- <= 0)) {
+			netdev_err(queue->vif->dev, "Missing extra info\n");
+			xenvif_fatal_tx_err(queue->vif);
+			return -EBADR;
+		}
+
+		memcpy(&extra, RING_GET_REQUEST(&queue->tx, cons),
+		       sizeof(extra));
+		if (unlikely(!extra.type ||
+			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
+			queue->tx.req_cons = ++cons;
+			netdev_err(queue->vif->dev,
+				   "Invalid extra type: %d\n", extra.type);
+			xenvif_fatal_tx_err(queue->vif);
+			return -EINVAL;
+		}
+
+		memcpy(&extras[extra.type - 1], &extra, sizeof(extra));
+		queue->tx.req_cons = ++cons;
+	} while (extra.flags & XEN_NETIF_EXTRA_FLAG_MORE);
+
+	return work_to_do;
+}
+
+static int xenvif_set_skb_gso(struct xenvif *vif,
+			      struct sk_buff *skb,
+			      struct xen_netif_extra_info *gso)
+{
+	if (!gso->u.gso.size) {
+		netdev_err(vif->dev, "GSO size must not be zero.\n");
+		xenvif_fatal_tx_err(vif);
+		return -EINVAL;
+	}
+
+	switch (gso->u.gso.type) {
+	case XEN_NETIF_GSO_TYPE_TCPV4:
+		skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
+		break;
+	case XEN_NETIF_GSO_TYPE_TCPV6:
+		skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
+		break;
+	default:
+		netdev_err(vif->dev, "Bad GSO type %d.\n", gso->u.gso.type);
+		xenvif_fatal_tx_err(vif);
+		return -EINVAL;
+	}
+
+	skb_shinfo(skb)->gso_size = gso->u.gso.size;
+	/* gso_segs will be calculated later */
+
+	return 0;
+}
+
+static int checksum_setup(struct xenvif_queue *queue, struct sk_buff *skb)
+{
+	bool recalculate_partial_csum = false;
+
+	/* A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
+	 * peers can fail to set NETRXF_csum_blank when sending a GSO
+	 * frame. In this case force the SKB to CHECKSUM_PARTIAL and
+	 * recalculate the partial checksum.
+	 */
+	if (skb->ip_summed != CHECKSUM_PARTIAL && skb_is_gso(skb)) {
+		queue->stats.rx_gso_checksum_fixup++;
+		skb->ip_summed = CHECKSUM_PARTIAL;
+		recalculate_partial_csum = true;
+	}
+
+	/* A non-CHECKSUM_PARTIAL SKB does not require setup. */
+	if (skb->ip_summed != CHECKSUM_PARTIAL)
+		return 0;
+
+	return skb_checksum_setup(skb, recalculate_partial_csum);
+}
+
+static bool tx_credit_exceeded(struct xenvif_queue *queue, unsigned size)
+{
+	u64 now = get_jiffies_64();
+	u64 next_credit = queue->credit_window_start +
+		msecs_to_jiffies(queue->credit_usec / 1000);
+
+	/* Timer could already be pending in rare cases. */
+	if (timer_pending(&queue->credit_timeout))
+		return true;
+
+	/* Passed the point where we can replenish credit? */
+	if (time_after_eq64(now, next_credit)) {
+		queue->credit_window_start = now;
+		tx_add_credit(queue);
+	}
+
+	/* Still too big to send right now? Set a callback. */
+	if (size > queue->remaining_credit) {
+		queue->credit_timeout.data     =
+			(unsigned long)queue;
+		mod_timer(&queue->credit_timeout,
+			  next_credit);
+		queue->credit_window_start = next_credit;
+
+		return true;
+	}
+
+	return false;
+}
+
+static void xenvif_tx_build_gops(struct xenvif_queue *queue,
+				     int budget,
+				     unsigned *copy_ops,
+				     unsigned *map_ops)
+{
+	struct gnttab_map_grant_ref *gop = queue->tx_map_ops, *request_gop;
+	struct sk_buff *skb;
+	int ret;
+
+	while (skb_queue_len(&queue->tx_queue) < budget) {
+		struct xen_netif_tx_request txreq;
+		struct xen_netif_tx_request txfrags[XEN_NETBK_LEGACY_SLOTS_MAX];
+		struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX-1];
+		u16 pending_idx;
+		RING_IDX idx;
+		int work_to_do;
+		unsigned int data_len;
+		pending_ring_idx_t index;
+
+		if (queue->tx.sring->req_prod - queue->tx.req_cons >
+		    XEN_NETIF_TX_RING_SIZE) {
+			netdev_err(queue->vif->dev,
+				   "Impossible number of requests. "
+				   "req_prod %d, req_cons %d, size %ld\n",
+				   queue->tx.sring->req_prod, queue->tx.req_cons,
+				   XEN_NETIF_TX_RING_SIZE);
+			xenvif_fatal_tx_err(queue->vif);
+			break;
+		}
+
+		work_to_do = RING_HAS_UNCONSUMED_REQUESTS(&queue->tx);
+		if (!work_to_do)
+			break;
+
+		idx = queue->tx.req_cons;
+		rmb(); /* Ensure that we see the request before we copy it. */
+		memcpy(&txreq, RING_GET_REQUEST(&queue->tx, idx), sizeof(txreq));
+
+		/* Credit-based scheduling. */
+		if (txreq.size > queue->remaining_credit &&
+		    tx_credit_exceeded(queue, txreq.size))
+			break;
+
+		queue->remaining_credit -= txreq.size;
+
+		work_to_do--;
+		queue->tx.req_cons = ++idx;
+
+		memset(extras, 0, sizeof(extras));
+		if (txreq.flags & XEN_NETTXF_extra_info) {
+			work_to_do = xenvif_get_extras(queue, extras,
+						       work_to_do);
+			idx = queue->tx.req_cons;
+			if (unlikely(work_to_do < 0))
+				break;
+		}
+
+		ret = xenvif_count_requests(queue, &txreq, txfrags, work_to_do);
+		if (unlikely(ret < 0))
+			break;
+
+		idx += ret;
+
+		if (unlikely(txreq.size < ETH_HLEN)) {
+			netdev_dbg(queue->vif->dev,
+				   "Bad packet size: %d\n", txreq.size);
+			xenvif_tx_err(queue, &txreq, idx);
+			break;
+		}
+
+		/* No crossing a page as the payload mustn't fragment. */
+		if (unlikely((txreq.offset + txreq.size) > PAGE_SIZE)) {
+			netdev_err(queue->vif->dev,
+				   "txreq.offset: %x, size: %u, end: %lu\n",
+				   txreq.offset, txreq.size,
+				   (unsigned long)(txreq.offset&~PAGE_MASK) + txreq.size);
+			xenvif_fatal_tx_err(queue->vif);
+			break;
+		}
+
+		index = pending_index(queue->pending_cons);
+		pending_idx = queue->pending_ring[index];
+
+		data_len = (txreq.size > XEN_NETBACK_TX_COPY_LEN &&
+			    ret < XEN_NETBK_LEGACY_SLOTS_MAX) ?
+			XEN_NETBACK_TX_COPY_LEN : txreq.size;
+
+		skb = xenvif_alloc_skb(data_len);
+		if (unlikely(skb == NULL)) {
+			netdev_dbg(queue->vif->dev,
+				   "Can't allocate a skb in start_xmit.\n");
+			xenvif_tx_err(queue, &txreq, idx);
+			break;
+		}
+
+		if (extras[XEN_NETIF_EXTRA_TYPE_GSO - 1].type) {
+			struct xen_netif_extra_info *gso;
+			gso = &extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];
+
+			if (xenvif_set_skb_gso(queue->vif, skb, gso)) {
+				/* Failure in xenvif_set_skb_gso is fatal. */
+				kfree_skb(skb);
+				break;
+			}
+		}
+
+		XENVIF_TX_CB(skb)->pending_idx = pending_idx;
+
+		__skb_put(skb, data_len);
+		queue->tx_copy_ops[*copy_ops].source.u.ref = txreq.gref;
+		queue->tx_copy_ops[*copy_ops].source.domid = queue->vif->domid;
+		queue->tx_copy_ops[*copy_ops].source.offset = txreq.offset;
+
+		queue->tx_copy_ops[*copy_ops].dest.u.gmfn =
+			virt_to_mfn(skb->data);
+		queue->tx_copy_ops[*copy_ops].dest.domid = DOMID_SELF;
+		queue->tx_copy_ops[*copy_ops].dest.offset =
+			offset_in_page(skb->data);
+
+		queue->tx_copy_ops[*copy_ops].len = data_len;
+		queue->tx_copy_ops[*copy_ops].flags = GNTCOPY_source_gref;
+
+		(*copy_ops)++;
+
+		skb_shinfo(skb)->nr_frags = ret;
+		if (data_len < txreq.size) {
+			skb_shinfo(skb)->nr_frags++;
+			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
+					     pending_idx);
+			xenvif_tx_create_map_op(queue, pending_idx, &txreq, gop);
+			gop++;
+		} else {
+			frag_set_pending_idx(&skb_shinfo(skb)->frags[0],
+					     INVALID_PENDING_IDX);
+			memcpy(&queue->pending_tx_info[pending_idx].req, &txreq,
+			       sizeof(txreq));
+		}
+
+		queue->pending_cons++;
+
+		request_gop = xenvif_get_requests(queue, skb, txfrags, gop);
+		if (request_gop == NULL) {
+			kfree_skb(skb);
+			xenvif_tx_err(queue, &txreq, idx);
+			break;
+		}
+		gop = request_gop;
+
+		__skb_queue_tail(&queue->tx_queue, skb);
+
+		queue->tx.req_cons = idx;
+
+		if (((gop-queue->tx_map_ops) >= ARRAY_SIZE(queue->tx_map_ops)) ||
+		    (*copy_ops >= ARRAY_SIZE(queue->tx_copy_ops)))
+			break;
+	}
+
+	(*map_ops) = gop - queue->tx_map_ops;
+	return;
+}
+
+/* Consolidate skb with a frag_list into a brand new one with local pages on
+ * frags. Returns 0 or -ENOMEM if can't allocate new pages.
+ */
+static int xenvif_handle_frag_list(struct xenvif_queue *queue, struct sk_buff *skb)
+{
+	unsigned int offset = skb_headlen(skb);
+	skb_frag_t frags[MAX_SKB_FRAGS];
+	int i, f;
+	struct ubuf_info *uarg;
+	struct sk_buff *nskb = skb_shinfo(skb)->frag_list;
+
+	queue->stats.tx_zerocopy_sent += 2;
+	queue->stats.tx_frag_overflow++;
+
+	xenvif_fill_frags(queue, nskb);
+	/* Subtract frags size, we will correct it later */
+	skb->truesize -= skb->data_len;
+	skb->len += nskb->len;
+	skb->data_len += nskb->len;
+
+	/* create a brand new frags array and coalesce there */
+	for (i = 0; offset < skb->len; i++) {
+		struct page *page;
+		unsigned int len;
+
+		BUG_ON(i >= MAX_SKB_FRAGS);
+		page = alloc_page(GFP_ATOMIC);
+		if (!page) {
+			int j;
+			skb->truesize += skb->data_len;
+			for (j = 0; j < i; j++)
+				put_page(frags[j].page.p);
+			return -ENOMEM;
+		}
+
+		if (offset + PAGE_SIZE < skb->len)
+			len = PAGE_SIZE;
+		else
+			len = skb->len - offset;
+		if (skb_copy_bits(skb, offset, page_address(page), len))
+			BUG();
+
+		offset += len;
+		frags[i].page.p = page;
+		frags[i].page_offset = 0;
+		skb_frag_size_set(&frags[i], len);
+	}
+
+	/* Copied all the bits from the frag list -- free it. */
+	skb_frag_list_init(skb);
+	xenvif_skb_zerocopy_prepare(queue, nskb);
+	kfree_skb(nskb);
+
+	/* Release all the original (foreign) frags. */
+	for (f = 0; f < skb_shinfo(skb)->nr_frags; f++)
+		skb_frag_unref(skb, f);
+	uarg = skb_shinfo(skb)->destructor_arg;
+	/* increase inflight counter to offset decrement in callback */
+	atomic_inc(&queue->inflight_packets);
+	uarg->callback(uarg, true);
+	skb_shinfo(skb)->destructor_arg = NULL;
+
+	/* Fill the skb with the new (local) frags. */
+	memcpy(skb_shinfo(skb)->frags, frags, i * sizeof(skb_frag_t));
+	skb_shinfo(skb)->nr_frags = i;
+	skb->truesize += i * PAGE_SIZE;
+
+	return 0;
+}
+
+static int xenvif_tx_submit(struct xenvif_queue *queue)
+{
+	struct gnttab_map_grant_ref *gop_map = queue->tx_map_ops;
+	struct gnttab_copy *gop_copy = queue->tx_copy_ops;
+	struct sk_buff *skb;
+	int work_done = 0;
+
+	while ((skb = __skb_dequeue(&queue->tx_queue)) != NULL) {
+		struct xen_netif_tx_request *txp;
+		u16 pending_idx;
+		unsigned data_len;
+
+		pending_idx = XENVIF_TX_CB(skb)->pending_idx;
+		txp = &queue->pending_tx_info[pending_idx].req;
+
+		/* Check the remap error code. */
+		if (unlikely(xenvif_tx_check_gop(queue, skb, &gop_map, &gop_copy))) {
+			/* If there was an error, xenvif_tx_check_gop is
+			 * expected to release all the frags which were mapped,
+			 * so kfree_skb shouldn't do it again
+			 */
+			skb_shinfo(skb)->nr_frags = 0;
+			if (skb_has_frag_list(skb)) {
+				struct sk_buff *nskb =
+						skb_shinfo(skb)->frag_list;
+				skb_shinfo(nskb)->nr_frags = 0;
+			}
+			kfree_skb(skb);
+			continue;
+		}
+
+		data_len = skb->len;
+		callback_param(queue, pending_idx).ctx = NULL;
+		if (data_len < txp->size) {
+			/* Append the packet payload as a fragment. */
+			txp->offset += data_len;
+			txp->size -= data_len;
+		} else {
+			/* Schedule a response immediately. */
+			xenvif_idx_release(queue, pending_idx,
+					   XEN_NETIF_RSP_OKAY);
+		}
+
+		if (txp->flags & XEN_NETTXF_csum_blank)
+			skb->ip_summed = CHECKSUM_PARTIAL;
+		else if (txp->flags & XEN_NETTXF_data_validated)
+			skb->ip_summed = CHECKSUM_UNNECESSARY;
+
+		xenvif_fill_frags(queue, skb);
+
+		if (unlikely(skb_has_frag_list(skb))) {
+			if (xenvif_handle_frag_list(queue, skb)) {
+				if (net_ratelimit())
+					netdev_err(queue->vif->dev,
+						   "Not enough memory to consolidate frag_list!\n");
+				xenvif_skb_zerocopy_prepare(queue, skb);
+				kfree_skb(skb);
+				continue;
+			}
+		}
+
+		skb->dev      = queue->vif->dev;
+		skb->protocol = eth_type_trans(skb, skb->dev);
+		skb_reset_network_header(skb);
+
+		if (checksum_setup(queue, skb)) {
+			netdev_dbg(queue->vif->dev,
+				   "Can't setup checksum in net_tx_action\n");
+			/* We have to set this flag to trigger the callback */
+			if (skb_shinfo(skb)->destructor_arg)
+				xenvif_skb_zerocopy_prepare(queue, skb);
+			kfree_skb(skb);
+			continue;
+		}
+
+		skb_probe_transport_header(skb, 0);
+
+		/* If the packet is GSO then we will have just set up the
+		 * transport header offset in checksum_setup so it's now
+		 * straightforward to calculate gso_segs.
+		 */
+		if (skb_is_gso(skb)) {
+			int mss = skb_shinfo(skb)->gso_size;
+			int hdrlen = skb_transport_header(skb) -
+				skb_mac_header(skb) +
+				tcp_hdrlen(skb);
+
+			skb_shinfo(skb)->gso_segs =
+				DIV_ROUND_UP(skb->len - hdrlen, mss);
+		}
+
+		queue->stats.rx_bytes += skb->len;
+		queue->stats.rx_packets++;
+
+		work_done++;
+
+		/* Set this flag right before netif_receive_skb, otherwise
+		 * someone might think this packet already left netback, and
+		 * do a skb_copy_ubufs while we are still in control of the
+		 * skb. E.g. the __pskb_pull_tail earlier can do such thing.
+		 */
+		if (skb_shinfo(skb)->destructor_arg) {
+			xenvif_skb_zerocopy_prepare(queue, skb);
+			queue->stats.tx_zerocopy_sent++;
+		}
+
+		netif_receive_skb(skb);
+	}
+
+	return work_done;
+}
+
+void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
+{
+	unsigned long flags;
+	pending_ring_idx_t index;
+	struct xenvif_queue *queue = ubuf_to_queue(ubuf);
+
+	/* This is the only place where we grab this lock, to protect callbacks
+	 * from each other.
+	 */
+	spin_lock_irqsave(&queue->callback_lock, flags);
+	do {
+		u16 pending_idx = ubuf->desc;
+		ubuf = (struct ubuf_info *) ubuf->ctx;
+		BUG_ON(queue->dealloc_prod - queue->dealloc_cons >=
+			MAX_PENDING_REQS);
+		index = pending_index(queue->dealloc_prod);
+		queue->dealloc_ring[index] = pending_idx;
+		/* Sync with xenvif_tx_dealloc_action:
+		 * insert idx then incr producer.
+		 */
+		smp_wmb();
+		queue->dealloc_prod++;
+	} while (ubuf);
+	wake_up(&queue->dealloc_wq);
+	spin_unlock_irqrestore(&queue->callback_lock, flags);
+
+	if (likely(zerocopy_success))
+		queue->stats.tx_zerocopy_success++;
+	else
+		queue->stats.tx_zerocopy_fail++;
+	xenvif_skb_zerocopy_complete(queue);
+}
+
+static inline void xenvif_tx_dealloc_action(struct xenvif_queue *queue)
+{
+	struct gnttab_unmap_grant_ref *gop;
+	pending_ring_idx_t dc, dp;
+	u16 pending_idx, pending_idx_release[MAX_PENDING_REQS];
+	unsigned int i = 0;
+
+	dc = queue->dealloc_cons;
+	gop = queue->tx_unmap_ops;
+
+	/* Free up any grants we have finished using */
+	do {
+		dp = queue->dealloc_prod;
+
+		/* Ensure we see all indices enqueued by all
+		 * xenvif_zerocopy_callback().
+		 */
+		smp_rmb();
+
+		while (dc != dp) {
+			BUG_ON(gop - queue->tx_unmap_ops > MAX_PENDING_REQS);
+			pending_idx =
+				queue->dealloc_ring[pending_index(dc++)];
+
+			pending_idx_release[gop-queue->tx_unmap_ops] =
+				pending_idx;
+			queue->pages_to_unmap[gop-queue->tx_unmap_ops] =
+				queue->mmap_pages[pending_idx];
+			gnttab_set_unmap_op(gop,
+					    idx_to_kaddr(queue, pending_idx),
+					    GNTMAP_host_map,
+					    queue->grant_tx_handle[pending_idx]);
+			xenvif_grant_handle_reset(queue, pending_idx);
+			++gop;
+		}
+
+	} while (dp != queue->dealloc_prod);
+
+	queue->dealloc_cons = dc;
+
+	if (gop - queue->tx_unmap_ops > 0) {
+		int ret;
+		ret = gnttab_unmap_refs(queue->tx_unmap_ops,
+					NULL,
+					queue->pages_to_unmap,
+					gop - queue->tx_unmap_ops);
+		if (ret) {
+			netdev_err(queue->vif->dev, "Unmap fail: nr_ops %tx ret %d\n",
+				   gop - queue->tx_unmap_ops, ret);
+			for (i = 0; i < gop - queue->tx_unmap_ops; ++i) {
+				if (gop[i].status != GNTST_okay)
+					netdev_err(queue->vif->dev,
+						   " host_addr: %llx handle: %x status: %d\n",
+						   gop[i].host_addr,
+						   gop[i].handle,
+						   gop[i].status);
+			}
+			BUG();
+		}
+	}
+
+	for (i = 0; i < gop - queue->tx_unmap_ops; ++i)
+		xenvif_idx_release(queue, pending_idx_release[i],
+				   XEN_NETIF_RSP_OKAY);
+}
+
+
+/* Called after netfront has transmitted */
+int xenvif_tx_action(struct xenvif_queue *queue, int budget)
+{
+	unsigned nr_mops, nr_cops = 0;
+	int work_done, ret;
+
+	if (unlikely(!tx_work_todo(queue)))
+		return 0;
+
+	xenvif_tx_build_gops(queue, budget, &nr_cops, &nr_mops);
+
+	if (nr_cops == 0)
+		return 0;
+
+	gnttab_batch_copy(queue->tx_copy_ops, nr_cops);
+	if (nr_mops != 0) {
+		ret = gnttab_map_refs(queue->tx_map_ops,
+				      NULL,
+				      queue->pages_to_map,
+				      nr_mops);
+		BUG_ON(ret);
+	}
+
+	work_done = xenvif_tx_submit(queue);
+
+	return work_done;
+}
+
+static void xenvif_idx_release(struct xenvif_queue *queue, u16 pending_idx,
+			       u8 status)
+{
+	struct pending_tx_info *pending_tx_info;
+	pending_ring_idx_t index;
+	unsigned long flags;
+
+	pending_tx_info = &queue->pending_tx_info[pending_idx];
+
+	spin_lock_irqsave(&queue->response_lock, flags);
+
+	make_tx_response(queue, &pending_tx_info->req, status);
+
+	/* Release the pending index before pusing the Tx response so
+	 * its available before a new Tx request is pushed by the
+	 * frontend.
+	 */
+	index = pending_index(queue->pending_prod++);
+	queue->pending_ring[index] = pending_idx;
+
+	push_tx_responses(queue);
+
+	spin_unlock_irqrestore(&queue->response_lock, flags);
+}
+
+
+static void make_tx_response(struct xenvif_queue *queue,
+			     struct xen_netif_tx_request *txp,
+			     s8       st)
+{
+	RING_IDX i = queue->tx.rsp_prod_pvt;
+	struct xen_netif_tx_response *resp;
+
+	resp = RING_GET_RESPONSE(&queue->tx, i);
+	resp->id     = txp->id;
+	resp->status = st;
+
+	if (txp->flags & XEN_NETTXF_extra_info)
+		RING_GET_RESPONSE(&queue->tx, ++i)->status = XEN_NETIF_RSP_NULL;
+
+	queue->tx.rsp_prod_pvt = ++i;
+}
+
+static void push_tx_responses(struct xenvif_queue *queue)
+{
+	int notify;
+
+	RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->tx, notify);
+	if (notify)
+		notify_remote_via_irq(queue->tx_irq);
+}
+
+static struct xen_netif_rx_response *make_rx_response(struct xenvif_queue *queue,
+					     u16      id,
+					     s8       st,
+					     u16      offset,
+					     u16      size,
+					     u16      flags)
+{
+	RING_IDX i = queue->rx.rsp_prod_pvt;
+	struct xen_netif_rx_response *resp;
+
+	resp = RING_GET_RESPONSE(&queue->rx, i);
+	resp->offset     = offset;
+	resp->flags      = flags;
+	resp->id         = id;
+	resp->status     = (s16)size;
+	if (st < 0)
+		resp->status = (s16)st;
+
+	queue->rx.rsp_prod_pvt = ++i;
+
+	return resp;
+}
+
+void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx)
+{
+	int ret;
+	struct gnttab_unmap_grant_ref tx_unmap_op;
+
+	gnttab_set_unmap_op(&tx_unmap_op,
+			    idx_to_kaddr(queue, pending_idx),
+			    GNTMAP_host_map,
+			    queue->grant_tx_handle[pending_idx]);
+	xenvif_grant_handle_reset(queue, pending_idx);
+
+	ret = gnttab_unmap_refs(&tx_unmap_op, NULL,
+				&queue->mmap_pages[pending_idx], 1);
+	if (ret) {
+		netdev_err(queue->vif->dev,
+			   "Unmap fail: ret: %d pending_idx: %d host_addr: %llx handle: %x status: %d\n",
+			   ret,
+			   pending_idx,
+			   tx_unmap_op.host_addr,
+			   tx_unmap_op.handle,
+			   tx_unmap_op.status);
+		BUG();
+	}
+}
+
+static inline int tx_work_todo(struct xenvif_queue *queue)
+{
+	if (likely(RING_HAS_UNCONSUMED_REQUESTS(&queue->tx)))
+		return 1;
+
+	return 0;
+}
+
+static inline bool tx_dealloc_work_todo(struct xenvif_queue *queue)
+{
+	return queue->dealloc_cons != queue->dealloc_prod;
+}
+
+void xenvif_unmap_frontend_rings(struct xenvif_queue *queue)
+{
+	if (queue->tx.sring)
+		xenbus_unmap_ring_vfree(xenvif_to_xenbus_device(queue->vif),
+					queue->tx.sring);
+	if (queue->rx.sring)
+		xenbus_unmap_ring_vfree(xenvif_to_xenbus_device(queue->vif),
+					queue->rx.sring);
+}
+
+int xenvif_map_frontend_rings(struct xenvif_queue *queue,
+			      grant_ref_t tx_ring_ref,
+			      grant_ref_t rx_ring_ref)
+{
+	void *addr;
+	struct xen_netif_tx_sring *txs;
+	struct xen_netif_rx_sring *rxs;
+
+	int err = -ENOMEM;
+
+	err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif),
+				     &tx_ring_ref, 1, &addr);
+	if (err)
+		goto err;
+
+	txs = (struct xen_netif_tx_sring *)addr;
+	BACK_RING_INIT(&queue->tx, txs, PAGE_SIZE);
+
+	err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif),
+				     &rx_ring_ref, 1, &addr);
+	if (err)
+		goto err;
+
+	rxs = (struct xen_netif_rx_sring *)addr;
+	BACK_RING_INIT(&queue->rx, rxs, PAGE_SIZE);
+
+	return 0;
+
+err:
+	xenvif_unmap_frontend_rings(queue);
+	return err;
+}
+
+static void xenvif_queue_carrier_off(struct xenvif_queue *queue)
+{
+	struct xenvif *vif = queue->vif;
+
+	queue->stalled = true;
+
+	/* At least one queue has stalled? Disable the carrier. */
+	spin_lock(&vif->lock);
+	if (vif->stalled_queues++ == 0) {
+		netdev_info(vif->dev, "Guest Rx stalled");
+		netif_carrier_off(vif->dev);
+	}
+	spin_unlock(&vif->lock);
+}
+
+static void xenvif_queue_carrier_on(struct xenvif_queue *queue)
+{
+	struct xenvif *vif = queue->vif;
+
+	queue->last_rx_time = jiffies; /* Reset Rx stall detection. */
+	queue->stalled = false;
+
+	/* All queues are ready? Enable the carrier. */
+	spin_lock(&vif->lock);
+	if (--vif->stalled_queues == 0) {
+		netdev_info(vif->dev, "Guest Rx ready");
+		netif_carrier_on(vif->dev);
+	}
+	spin_unlock(&vif->lock);
+}
+
+static bool xenvif_rx_queue_stalled(struct xenvif_queue *queue)
+{
+	RING_IDX prod, cons;
+
+	prod = queue->rx.sring->req_prod;
+	cons = queue->rx.req_cons;
+
+	return !queue->stalled
+		&& prod - cons < XEN_NETBK_RX_SLOTS_MAX
+		&& time_after(jiffies,
+			      queue->last_rx_time + queue->vif->stall_timeout);
+}
+
+static bool xenvif_rx_queue_ready(struct xenvif_queue *queue)
+{
+	RING_IDX prod, cons;
+
+	prod = queue->rx.sring->req_prod;
+	cons = queue->rx.req_cons;
+
+	return queue->stalled
+		&& prod - cons >= XEN_NETBK_RX_SLOTS_MAX;
+}
+
+static bool xenvif_have_rx_work(struct xenvif_queue *queue)
+{
+	return (!skb_queue_empty(&queue->rx_queue)
+		&& xenvif_rx_ring_slots_available(queue, XEN_NETBK_RX_SLOTS_MAX))
+		|| (queue->vif->stall_timeout &&
+		    (xenvif_rx_queue_stalled(queue)
+		     || xenvif_rx_queue_ready(queue)))
+		|| kthread_should_stop()
+		|| queue->vif->disabled;
+}
+
+static long xenvif_rx_queue_timeout(struct xenvif_queue *queue)
+{
+	struct sk_buff *skb;
+	long timeout;
+
+	skb = skb_peek(&queue->rx_queue);
+	if (!skb)
+		return MAX_SCHEDULE_TIMEOUT;
+
+	timeout = XENVIF_RX_CB(skb)->expires - jiffies;
+	return timeout < 0 ? 0 : timeout;
+}
+
+/* Wait until the guest Rx thread has work.
+ *
+ * The timeout needs to be adjusted based on the current head of the
+ * queue (and not just the head at the beginning).  In particular, if
+ * the queue is initially empty an infinite timeout is used and this
+ * needs to be reduced when a skb is queued.
+ *
+ * This cannot be done with wait_event_timeout() because it only
+ * calculates the timeout once.
+ */
+static void xenvif_wait_for_rx_work(struct xenvif_queue *queue)
+{
+	DEFINE_WAIT(wait);
+
+	if (xenvif_have_rx_work(queue))
+		return;
+
+	for (;;) {
+		long ret;
+
+		prepare_to_wait(&queue->wq, &wait, TASK_INTERRUPTIBLE);
+		if (xenvif_have_rx_work(queue))
+			break;
+		ret = schedule_timeout(xenvif_rx_queue_timeout(queue));
+		if (!ret)
+			break;
+	}
+	finish_wait(&queue->wq, &wait);
+}
+
+int xenvif_kthread_guest_rx(void *data)
+{
+	struct xenvif_queue *queue = data;
+	struct xenvif *vif = queue->vif;
+
+	if (!vif->stall_timeout)
+		xenvif_queue_carrier_on(queue);
+
+	for (;;) {
+		xenvif_wait_for_rx_work(queue);
+
+		if (kthread_should_stop())
+			break;
+
+		/* This frontend is found to be rogue, disable it in
+		 * kthread context. Currently this is only set when
+		 * netback finds out frontend sends malformed packet,
+		 * but we cannot disable the interface in softirq
+		 * context so we defer it here, if this thread is
+		 * associated with queue 0.
+		 */
+		if (unlikely(vif->disabled && queue->id == 0)) {
+			xenvif_carrier_off(vif);
+			break;
+		}
+
+		if (!skb_queue_empty(&queue->rx_queue))
+			xenvif_rx_action(queue);
+
+		/* If the guest hasn't provided any Rx slots for a
+		 * while it's probably not responsive, drop the
+		 * carrier so packets are dropped earlier.
+		 */
+		if (vif->stall_timeout) {
+			if (xenvif_rx_queue_stalled(queue))
+				xenvif_queue_carrier_off(queue);
+			else if (xenvif_rx_queue_ready(queue))
+				xenvif_queue_carrier_on(queue);
+		}
+
+		/* Queued packets may have foreign pages from other
+		 * domains.  These cannot be queued indefinitely as
+		 * this would starve guests of grant refs and transmit
+		 * slots.
+		 */
+		xenvif_rx_queue_drop_expired(queue);
+
+		xenvif_rx_queue_maybe_wake(queue);
+
+		cond_resched();
+	}
+
+	/* Bin any remaining skbs */
+	xenvif_rx_queue_purge(queue);
+
+	return 0;
+}
+
+static bool xenvif_dealloc_kthread_should_stop(struct xenvif_queue *queue)
+{
+	/* Dealloc thread must remain running until all inflight
+	 * packets complete.
+	 */
+	return kthread_should_stop() &&
+		!atomic_read(&queue->inflight_packets);
+}
+
+int xenvif_dealloc_kthread(void *data)
+{
+	struct xenvif_queue *queue = data;
+
+	for (;;) {
+		wait_event_interruptible(queue->dealloc_wq,
+					 tx_dealloc_work_todo(queue) ||
+					 xenvif_dealloc_kthread_should_stop(queue));
+		if (xenvif_dealloc_kthread_should_stop(queue))
+			break;
+
+		xenvif_tx_dealloc_action(queue);
+		cond_resched();
+	}
+
+	/* Unmap anything remaining*/
+	if (tx_dealloc_work_todo(queue))
+		xenvif_tx_dealloc_action(queue);
+
+	return 0;
+}
+
+static int __init netback_init(void)
+{
+	int rc = 0;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	/* Allow as many queues as there are CPUs, by default */
+	xenvif_max_queues = num_online_cpus();
+
+	if (fatal_skb_slots < XEN_NETBK_LEGACY_SLOTS_MAX) {
+		pr_info("fatal_skb_slots too small (%d), bump it to XEN_NETBK_LEGACY_SLOTS_MAX (%d)\n",
+			fatal_skb_slots, XEN_NETBK_LEGACY_SLOTS_MAX);
+		fatal_skb_slots = XEN_NETBK_LEGACY_SLOTS_MAX;
+	}
+
+	rc = xenvif_xenbus_init();
+	if (rc)
+		goto failed_init;
+
+#ifdef CONFIG_DEBUG_FS
+	xen_netback_dbg_root = debugfs_create_dir("xen-netback", NULL);
+	if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+		pr_warn("Init of debugfs returned %ld!\n",
+			PTR_ERR(xen_netback_dbg_root));
+#endif /* CONFIG_DEBUG_FS */
+
+	return 0;
+
+failed_init:
+	return rc;
+}
+
+module_init(netback_init);
+
+static void __exit netback_fini(void)
+{
+#ifdef CONFIG_DEBUG_FS
+	if (!IS_ERR_OR_NULL(xen_netback_dbg_root))
+		debugfs_remove_recursive(xen_netback_dbg_root);
+#endif /* CONFIG_DEBUG_FS */
+	xenvif_xenbus_fini();
+}
+module_exit(netback_fini);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("xen-backend:vif");
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
new file mode 100644
index 000000000..ec383b0f5
--- /dev/null
+++ b/drivers/net/xen-netback/xenbus.c
@@ -0,0 +1,1043 @@
+/*
+ * Xenbus code for netif backend
+ *
+ * Copyright (C) 2005 Rusty Russell <rusty@rustcorp.com.au>
+ * Copyright (C) 2005 XenSource Ltd
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "common.h"
+#include <linux/vmalloc.h>
+#include <linux/rtnetlink.h>
+
+struct backend_info {
+	struct xenbus_device *dev;
+	struct xenvif *vif;
+
+	/* This is the state that will be reflected in xenstore when any
+	 * active hotplug script completes.
+	 */
+	enum xenbus_state state;
+
+	enum xenbus_state frontend_state;
+	struct xenbus_watch hotplug_status_watch;
+	u8 have_hotplug_status_watch:1;
+
+	const char *hotplug_script;
+};
+
+static int connect_rings(struct backend_info *be, struct xenvif_queue *queue);
+static void connect(struct backend_info *be);
+static int read_xenbus_vif_flags(struct backend_info *be);
+static int backend_create_xenvif(struct backend_info *be);
+static void unregister_hotplug_status_watch(struct backend_info *be);
+static void xen_unregister_watchers(struct xenvif *vif);
+static void set_backend_state(struct backend_info *be,
+			      enum xenbus_state state);
+
+#ifdef CONFIG_DEBUG_FS
+struct dentry *xen_netback_dbg_root = NULL;
+
+static int xenvif_read_io_ring(struct seq_file *m, void *v)
+{
+	struct xenvif_queue *queue = m->private;
+	struct xen_netif_tx_back_ring *tx_ring = &queue->tx;
+	struct xen_netif_rx_back_ring *rx_ring = &queue->rx;
+	struct netdev_queue *dev_queue;
+
+	if (tx_ring->sring) {
+		struct xen_netif_tx_sring *sring = tx_ring->sring;
+
+		seq_printf(m, "Queue %d\nTX: nr_ents %u\n", queue->id,
+			   tx_ring->nr_ents);
+		seq_printf(m, "req prod %u (%d) cons %u (%d) event %u (%d)\n",
+			   sring->req_prod,
+			   sring->req_prod - sring->rsp_prod,
+			   tx_ring->req_cons,
+			   tx_ring->req_cons - sring->rsp_prod,
+			   sring->req_event,
+			   sring->req_event - sring->rsp_prod);
+		seq_printf(m, "rsp prod %u (base) pvt %u (%d) event %u (%d)\n",
+			   sring->rsp_prod,
+			   tx_ring->rsp_prod_pvt,
+			   tx_ring->rsp_prod_pvt - sring->rsp_prod,
+			   sring->rsp_event,
+			   sring->rsp_event - sring->rsp_prod);
+		seq_printf(m, "pending prod %u pending cons %u nr_pending_reqs %u\n",
+			   queue->pending_prod,
+			   queue->pending_cons,
+			   nr_pending_reqs(queue));
+		seq_printf(m, "dealloc prod %u dealloc cons %u dealloc_queue %u\n\n",
+			   queue->dealloc_prod,
+			   queue->dealloc_cons,
+			   queue->dealloc_prod - queue->dealloc_cons);
+	}
+
+	if (rx_ring->sring) {
+		struct xen_netif_rx_sring *sring = rx_ring->sring;
+
+		seq_printf(m, "RX: nr_ents %u\n", rx_ring->nr_ents);
+		seq_printf(m, "req prod %u (%d) cons %u (%d) event %u (%d)\n",
+			   sring->req_prod,
+			   sring->req_prod - sring->rsp_prod,
+			   rx_ring->req_cons,
+			   rx_ring->req_cons - sring->rsp_prod,
+			   sring->req_event,
+			   sring->req_event - sring->rsp_prod);
+		seq_printf(m, "rsp prod %u (base) pvt %u (%d) event %u (%d)\n\n",
+			   sring->rsp_prod,
+			   rx_ring->rsp_prod_pvt,
+			   rx_ring->rsp_prod_pvt - sring->rsp_prod,
+			   sring->rsp_event,
+			   sring->rsp_event - sring->rsp_prod);
+	}
+
+	seq_printf(m, "NAPI state: %lx NAPI weight: %d TX queue len %u\n"
+		   "Credit timer_pending: %d, credit: %lu, usec: %lu\n"
+		   "remaining: %lu, expires: %lu, now: %lu\n",
+		   queue->napi.state, queue->napi.weight,
+		   skb_queue_len(&queue->tx_queue),
+		   timer_pending(&queue->credit_timeout),
+		   queue->credit_bytes,
+		   queue->credit_usec,
+		   queue->remaining_credit,
+		   queue->credit_timeout.expires,
+		   jiffies);
+
+	dev_queue = netdev_get_tx_queue(queue->vif->dev, queue->id);
+
+	seq_printf(m, "\nRx internal queue: len %u max %u pkts %u %s\n",
+		   queue->rx_queue_len, queue->rx_queue_max,
+		   skb_queue_len(&queue->rx_queue),
+		   netif_tx_queue_stopped(dev_queue) ? "stopped" : "running");
+
+	return 0;
+}
+
+#define XENVIF_KICK_STR "kick"
+#define BUFFER_SIZE     32
+
+static ssize_t
+xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count,
+		     loff_t *ppos)
+{
+	struct xenvif_queue *queue =
+		((struct seq_file *)filp->private_data)->private;
+	int len;
+	char write[BUFFER_SIZE];
+
+	/* don't allow partial writes and check the length */
+	if (*ppos != 0)
+		return 0;
+	if (count >= sizeof(write))
+		return -ENOSPC;
+
+	len = simple_write_to_buffer(write,
+				     sizeof(write) - 1,
+				     ppos,
+				     buf,
+				     count);
+	if (len < 0)
+		return len;
+
+	write[len] = '\0';
+
+	if (!strncmp(write, XENVIF_KICK_STR, sizeof(XENVIF_KICK_STR) - 1))
+		xenvif_interrupt(0, (void *)queue);
+	else {
+		pr_warn("Unknown command to io_ring_q%d. Available: kick\n",
+			queue->id);
+		count = -EINVAL;
+	}
+	return count;
+}
+
+static int xenvif_dump_open(struct inode *inode, struct file *filp)
+{
+	int ret;
+	void *queue = NULL;
+
+	if (inode->i_private)
+		queue = inode->i_private;
+	ret = single_open(filp, xenvif_read_io_ring, queue);
+	filp->f_mode |= FMODE_PWRITE;
+	return ret;
+}
+
+static const struct file_operations xenvif_dbg_io_ring_ops_fops = {
+	.owner = THIS_MODULE,
+	.open = xenvif_dump_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+	.write = xenvif_write_io_ring,
+};
+
+static void xenvif_debugfs_addif(struct xenvif *vif)
+{
+	struct dentry *pfile;
+	int i;
+
+	if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+		return;
+
+	vif->xenvif_dbg_root = debugfs_create_dir(vif->dev->name,
+						  xen_netback_dbg_root);
+	if (!IS_ERR_OR_NULL(vif->xenvif_dbg_root)) {
+		for (i = 0; i < vif->num_queues; ++i) {
+			char filename[sizeof("io_ring_q") + 4];
+
+			snprintf(filename, sizeof(filename), "io_ring_q%d", i);
+			pfile = debugfs_create_file(filename,
+						    S_IRUSR | S_IWUSR,
+						    vif->xenvif_dbg_root,
+						    &vif->queues[i],
+						    &xenvif_dbg_io_ring_ops_fops);
+			if (IS_ERR_OR_NULL(pfile))
+				pr_warn("Creation of io_ring file returned %ld!\n",
+					PTR_ERR(pfile));
+		}
+	} else
+		netdev_warn(vif->dev,
+			    "Creation of vif debugfs dir returned %ld!\n",
+			    PTR_ERR(vif->xenvif_dbg_root));
+}
+
+static void xenvif_debugfs_delif(struct xenvif *vif)
+{
+	if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+		return;
+
+	if (!IS_ERR_OR_NULL(vif->xenvif_dbg_root))
+		debugfs_remove_recursive(vif->xenvif_dbg_root);
+	vif->xenvif_dbg_root = NULL;
+}
+#endif /* CONFIG_DEBUG_FS */
+
+static int netback_remove(struct xenbus_device *dev)
+{
+	struct backend_info *be = dev_get_drvdata(&dev->dev);
+
+	set_backend_state(be, XenbusStateClosed);
+
+	unregister_hotplug_status_watch(be);
+	if (be->vif) {
+		kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
+		xen_unregister_watchers(be->vif);
+		xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status");
+		xenvif_free(be->vif);
+		be->vif = NULL;
+	}
+	kfree(be->hotplug_script);
+	kfree(be);
+	dev_set_drvdata(&dev->dev, NULL);
+	return 0;
+}
+
+
+/**
+ * Entry point to this code when a new device is created.  Allocate the basic
+ * structures and switch to InitWait.
+ */
+static int netback_probe(struct xenbus_device *dev,
+			 const struct xenbus_device_id *id)
+{
+	const char *message;
+	struct xenbus_transaction xbt;
+	int err;
+	int sg;
+	const char *script;
+	struct backend_info *be = kzalloc(sizeof(struct backend_info),
+					  GFP_KERNEL);
+	if (!be) {
+		xenbus_dev_fatal(dev, -ENOMEM,
+				 "allocating backend structure");
+		return -ENOMEM;
+	}
+
+	be->dev = dev;
+	dev_set_drvdata(&dev->dev, be);
+
+	sg = 1;
+
+	do {
+		err = xenbus_transaction_start(&xbt);
+		if (err) {
+			xenbus_dev_fatal(dev, err, "starting transaction");
+			goto fail;
+		}
+
+		err = xenbus_printf(xbt, dev->nodename, "feature-sg", "%d", sg);
+		if (err) {
+			message = "writing feature-sg";
+			goto abort_transaction;
+		}
+
+		err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv4",
+				    "%d", sg);
+		if (err) {
+			message = "writing feature-gso-tcpv4";
+			goto abort_transaction;
+		}
+
+		err = xenbus_printf(xbt, dev->nodename, "feature-gso-tcpv6",
+				    "%d", sg);
+		if (err) {
+			message = "writing feature-gso-tcpv6";
+			goto abort_transaction;
+		}
+
+		/* We support partial checksum setup for IPv6 packets */
+		err = xenbus_printf(xbt, dev->nodename,
+				    "feature-ipv6-csum-offload",
+				    "%d", 1);
+		if (err) {
+			message = "writing feature-ipv6-csum-offload";
+			goto abort_transaction;
+		}
+
+		/* We support rx-copy path. */
+		err = xenbus_printf(xbt, dev->nodename,
+				    "feature-rx-copy", "%d", 1);
+		if (err) {
+			message = "writing feature-rx-copy";
+			goto abort_transaction;
+		}
+
+		/*
+		 * We don't support rx-flip path (except old guests who don't
+		 * grok this feature flag).
+		 */
+		err = xenbus_printf(xbt, dev->nodename,
+				    "feature-rx-flip", "%d", 0);
+		if (err) {
+			message = "writing feature-rx-flip";
+			goto abort_transaction;
+		}
+
+		err = xenbus_transaction_end(xbt, 0);
+	} while (err == -EAGAIN);
+
+	if (err) {
+		xenbus_dev_fatal(dev, err, "completing transaction");
+		goto fail;
+	}
+
+	/*
+	 * Split event channels support, this is optional so it is not
+	 * put inside the above loop.
+	 */
+	err = xenbus_printf(XBT_NIL, dev->nodename,
+			    "feature-split-event-channels",
+			    "%u", separate_tx_rx_irq);
+	if (err)
+		pr_debug("Error writing feature-split-event-channels\n");
+
+	/* Multi-queue support: This is an optional feature. */
+	err = xenbus_printf(XBT_NIL, dev->nodename,
+			    "multi-queue-max-queues", "%u", xenvif_max_queues);
+	if (err)
+		pr_debug("Error writing multi-queue-max-queues\n");
+
+	script = xenbus_read(XBT_NIL, dev->nodename, "script", NULL);
+	if (IS_ERR(script)) {
+		err = PTR_ERR(script);
+		xenbus_dev_fatal(dev, err, "reading script");
+		goto fail;
+	}
+
+	be->hotplug_script = script;
+
+	err = xenbus_switch_state(dev, XenbusStateInitWait);
+	if (err)
+		goto fail;
+
+	be->state = XenbusStateInitWait;
+
+	/* This kicks hotplug scripts, so do it immediately. */
+	err = backend_create_xenvif(be);
+	if (err)
+		goto fail;
+
+	return 0;
+
+abort_transaction:
+	xenbus_transaction_end(xbt, 1);
+	xenbus_dev_fatal(dev, err, "%s", message);
+fail:
+	pr_debug("failed\n");
+	netback_remove(dev);
+	return err;
+}
+
+
+/*
+ * Handle the creation of the hotplug script environment.  We add the script
+ * and vif variables to the environment, for the benefit of the vif-* hotplug
+ * scripts.
+ */
+static int netback_uevent(struct xenbus_device *xdev,
+			  struct kobj_uevent_env *env)
+{
+	struct backend_info *be = dev_get_drvdata(&xdev->dev);
+
+	if (!be)
+		return 0;
+
+	if (add_uevent_var(env, "script=%s", be->hotplug_script))
+		return -ENOMEM;
+
+	if (!be->vif)
+		return 0;
+
+	return add_uevent_var(env, "vif=%s", be->vif->dev->name);
+}
+
+
+static int backend_create_xenvif(struct backend_info *be)
+{
+	int err;
+	long handle;
+	struct xenbus_device *dev = be->dev;
+	struct xenvif *vif;
+
+	if (be->vif != NULL)
+		return 0;
+
+	err = xenbus_scanf(XBT_NIL, dev->nodename, "handle", "%li", &handle);
+	if (err != 1) {
+		xenbus_dev_fatal(dev, err, "reading handle");
+		return (err < 0) ? err : -EINVAL;
+	}
+
+	vif = xenvif_alloc(&dev->dev, dev->otherend_id, handle);
+	if (IS_ERR(vif)) {
+		err = PTR_ERR(vif);
+		xenbus_dev_fatal(dev, err, "creating interface");
+		return err;
+	}
+	be->vif = vif;
+
+	kobject_uevent(&dev->dev.kobj, KOBJ_ONLINE);
+	return 0;
+}
+
+static void backend_disconnect(struct backend_info *be)
+{
+	if (be->vif) {
+		xen_unregister_watchers(be->vif);
+#ifdef CONFIG_DEBUG_FS
+		xenvif_debugfs_delif(be->vif);
+#endif /* CONFIG_DEBUG_FS */
+		xenvif_disconnect(be->vif);
+	}
+}
+
+static void backend_connect(struct backend_info *be)
+{
+	if (be->vif)
+		connect(be);
+}
+
+static inline void backend_switch_state(struct backend_info *be,
+					enum xenbus_state state)
+{
+	struct xenbus_device *dev = be->dev;
+
+	pr_debug("%s -> %s\n", dev->nodename, xenbus_strstate(state));
+	be->state = state;
+
+	/* If we are waiting for a hotplug script then defer the
+	 * actual xenbus state change.
+	 */
+	if (!be->have_hotplug_status_watch)
+		xenbus_switch_state(dev, state);
+}
+
+/* Handle backend state transitions:
+ *
+ * The backend state starts in InitWait and the following transitions are
+ * allowed.
+ *
+ * InitWait -> Connected
+ *
+ *    ^    \         |
+ *    |     \        |
+ *    |      \       |
+ *    |       \      |
+ *    |        \     |
+ *    |         \    |
+ *    |          V   V
+ *
+ *  Closed  <-> Closing
+ *
+ * The state argument specifies the eventual state of the backend and the
+ * function transitions to that state via the shortest path.
+ */
+static void set_backend_state(struct backend_info *be,
+			      enum xenbus_state state)
+{
+	while (be->state != state) {
+		switch (be->state) {
+		case XenbusStateClosed:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateConnected:
+				pr_info("%s: prepare for reconnect\n",
+					be->dev->nodename);
+				backend_switch_state(be, XenbusStateInitWait);
+				break;
+			case XenbusStateClosing:
+				backend_switch_state(be, XenbusStateClosing);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		case XenbusStateInitWait:
+			switch (state) {
+			case XenbusStateConnected:
+				backend_connect(be);
+				backend_switch_state(be, XenbusStateConnected);
+				break;
+			case XenbusStateClosing:
+			case XenbusStateClosed:
+				backend_switch_state(be, XenbusStateClosing);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		case XenbusStateConnected:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateClosing:
+			case XenbusStateClosed:
+				backend_disconnect(be);
+				backend_switch_state(be, XenbusStateClosing);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		case XenbusStateClosing:
+			switch (state) {
+			case XenbusStateInitWait:
+			case XenbusStateConnected:
+			case XenbusStateClosed:
+				backend_switch_state(be, XenbusStateClosed);
+				break;
+			default:
+				BUG();
+			}
+			break;
+		default:
+			BUG();
+		}
+	}
+}
+
+/**
+ * Callback received when the frontend's state changes.
+ */
+static void frontend_changed(struct xenbus_device *dev,
+			     enum xenbus_state frontend_state)
+{
+	struct backend_info *be = dev_get_drvdata(&dev->dev);
+
+	pr_debug("%s -> %s\n", dev->otherend, xenbus_strstate(frontend_state));
+
+	be->frontend_state = frontend_state;
+
+	switch (frontend_state) {
+	case XenbusStateInitialising:
+		set_backend_state(be, XenbusStateInitWait);
+		break;
+
+	case XenbusStateInitialised:
+		break;
+
+	case XenbusStateConnected:
+		set_backend_state(be, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		set_backend_state(be, XenbusStateClosing);
+		break;
+
+	case XenbusStateClosed:
+		set_backend_state(be, XenbusStateClosed);
+		if (xenbus_dev_is_online(dev))
+			break;
+		/* fall through if not online */
+	case XenbusStateUnknown:
+		set_backend_state(be, XenbusStateClosed);
+		device_unregister(&dev->dev);
+		break;
+
+	default:
+		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+				 frontend_state);
+		break;
+	}
+}
+
+
+static void xen_net_read_rate(struct xenbus_device *dev,
+			      unsigned long *bytes, unsigned long *usec)
+{
+	char *s, *e;
+	unsigned long b, u;
+	char *ratestr;
+
+	/* Default to unlimited bandwidth. */
+	*bytes = ~0UL;
+	*usec = 0;
+
+	ratestr = xenbus_read(XBT_NIL, dev->nodename, "rate", NULL);
+	if (IS_ERR(ratestr))
+		return;
+
+	s = ratestr;
+	b = simple_strtoul(s, &e, 10);
+	if ((s == e) || (*e != ','))
+		goto fail;
+
+	s = e + 1;
+	u = simple_strtoul(s, &e, 10);
+	if ((s == e) || (*e != '\0'))
+		goto fail;
+
+	*bytes = b;
+	*usec = u;
+
+	kfree(ratestr);
+	return;
+
+ fail:
+	pr_warn("Failed to parse network rate limit. Traffic unlimited.\n");
+	kfree(ratestr);
+}
+
+static int xen_net_read_mac(struct xenbus_device *dev, u8 mac[])
+{
+	char *s, *e, *macstr;
+	int i;
+
+	macstr = s = xenbus_read(XBT_NIL, dev->nodename, "mac", NULL);
+	if (IS_ERR(macstr))
+		return PTR_ERR(macstr);
+
+	for (i = 0; i < ETH_ALEN; i++) {
+		mac[i] = simple_strtoul(s, &e, 16);
+		if ((s == e) || (*e != ((i == ETH_ALEN-1) ? '\0' : ':'))) {
+			kfree(macstr);
+			return -ENOENT;
+		}
+		s = e+1;
+	}
+
+	kfree(macstr);
+	return 0;
+}
+
+static void xen_net_rate_changed(struct xenbus_watch *watch,
+				const char **vec, unsigned int len)
+{
+	struct xenvif *vif = container_of(watch, struct xenvif, credit_watch);
+	struct xenbus_device *dev = xenvif_to_xenbus_device(vif);
+	unsigned long   credit_bytes;
+	unsigned long   credit_usec;
+	unsigned int queue_index;
+
+	xen_net_read_rate(dev, &credit_bytes, &credit_usec);
+	for (queue_index = 0; queue_index < vif->num_queues; queue_index++) {
+		struct xenvif_queue *queue = &vif->queues[queue_index];
+
+		queue->credit_bytes = credit_bytes;
+		queue->credit_usec = credit_usec;
+		if (!mod_timer_pending(&queue->credit_timeout, jiffies) &&
+			queue->remaining_credit > queue->credit_bytes) {
+			queue->remaining_credit = queue->credit_bytes;
+		}
+	}
+}
+
+static int xen_register_watchers(struct xenbus_device *dev, struct xenvif *vif)
+{
+	int err = 0;
+	char *node;
+	unsigned maxlen = strlen(dev->nodename) + sizeof("/rate");
+
+	if (vif->credit_watch.node)
+		return -EADDRINUSE;
+
+	node = kmalloc(maxlen, GFP_KERNEL);
+	if (!node)
+		return -ENOMEM;
+	snprintf(node, maxlen, "%s/rate", dev->nodename);
+	vif->credit_watch.node = node;
+	vif->credit_watch.callback = xen_net_rate_changed;
+	err = register_xenbus_watch(&vif->credit_watch);
+	if (err) {
+		pr_err("Failed to set watcher %s\n", vif->credit_watch.node);
+		kfree(node);
+		vif->credit_watch.node = NULL;
+		vif->credit_watch.callback = NULL;
+	}
+	return err;
+}
+
+static void xen_unregister_watchers(struct xenvif *vif)
+{
+	if (vif->credit_watch.node) {
+		unregister_xenbus_watch(&vif->credit_watch);
+		kfree(vif->credit_watch.node);
+		vif->credit_watch.node = NULL;
+	}
+}
+
+static void unregister_hotplug_status_watch(struct backend_info *be)
+{
+	if (be->have_hotplug_status_watch) {
+		unregister_xenbus_watch(&be->hotplug_status_watch);
+		kfree(be->hotplug_status_watch.node);
+	}
+	be->have_hotplug_status_watch = 0;
+}
+
+static void hotplug_status_changed(struct xenbus_watch *watch,
+				   const char **vec,
+				   unsigned int vec_size)
+{
+	struct backend_info *be = container_of(watch,
+					       struct backend_info,
+					       hotplug_status_watch);
+	char *str;
+	unsigned int len;
+
+	str = xenbus_read(XBT_NIL, be->dev->nodename, "hotplug-status", &len);
+	if (IS_ERR(str))
+		return;
+	if (len == sizeof("connected")-1 && !memcmp(str, "connected", len)) {
+		/* Complete any pending state change */
+		xenbus_switch_state(be->dev, be->state);
+
+		/* Not interested in this watch anymore. */
+		unregister_hotplug_status_watch(be);
+	}
+	kfree(str);
+}
+
+static void connect(struct backend_info *be)
+{
+	int err;
+	struct xenbus_device *dev = be->dev;
+	unsigned long credit_bytes, credit_usec;
+	unsigned int queue_index;
+	unsigned int requested_num_queues;
+	struct xenvif_queue *queue;
+
+	/* Check whether the frontend requested multiple queues
+	 * and read the number requested.
+	 */
+	err = xenbus_scanf(XBT_NIL, dev->otherend,
+			   "multi-queue-num-queues",
+			   "%u", &requested_num_queues);
+	if (err < 0) {
+		requested_num_queues = 1; /* Fall back to single queue */
+	} else if (requested_num_queues > xenvif_max_queues) {
+		/* buggy or malicious guest */
+		xenbus_dev_fatal(dev, err,
+				 "guest requested %u queues, exceeding the maximum of %u.",
+				 requested_num_queues, xenvif_max_queues);
+		return;
+	}
+
+	err = xen_net_read_mac(dev, be->vif->fe_dev_addr);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "parsing %s/mac", dev->nodename);
+		return;
+	}
+
+	xen_net_read_rate(dev, &credit_bytes, &credit_usec);
+	xen_unregister_watchers(be->vif);
+	xen_register_watchers(dev, be->vif);
+	read_xenbus_vif_flags(be);
+
+	/* Use the number of queues requested by the frontend */
+	be->vif->queues = vzalloc(requested_num_queues *
+				  sizeof(struct xenvif_queue));
+	be->vif->num_queues = requested_num_queues;
+	be->vif->stalled_queues = requested_num_queues;
+
+	for (queue_index = 0; queue_index < requested_num_queues; ++queue_index) {
+		queue = &be->vif->queues[queue_index];
+		queue->vif = be->vif;
+		queue->id = queue_index;
+		snprintf(queue->name, sizeof(queue->name), "%s-q%u",
+				be->vif->dev->name, queue->id);
+
+		err = xenvif_init_queue(queue);
+		if (err) {
+			/* xenvif_init_queue() cleans up after itself on
+			 * failure, but we need to clean up any previously
+			 * initialised queues. Set num_queues to i so that
+			 * earlier queues can be destroyed using the regular
+			 * disconnect logic.
+			 */
+			be->vif->num_queues = queue_index;
+			goto err;
+		}
+
+		queue->credit_bytes = credit_bytes;
+		queue->remaining_credit = credit_bytes;
+		queue->credit_usec = credit_usec;
+
+		err = connect_rings(be, queue);
+		if (err) {
+			/* connect_rings() cleans up after itself on failure,
+			 * but we need to clean up after xenvif_init_queue() here,
+			 * and also clean up any previously initialised queues.
+			 */
+			xenvif_deinit_queue(queue);
+			be->vif->num_queues = queue_index;
+			goto err;
+		}
+	}
+
+#ifdef CONFIG_DEBUG_FS
+	xenvif_debugfs_addif(be->vif);
+#endif /* CONFIG_DEBUG_FS */
+
+	/* Initialisation completed, tell core driver the number of
+	 * active queues.
+	 */
+	rtnl_lock();
+	netif_set_real_num_tx_queues(be->vif->dev, requested_num_queues);
+	netif_set_real_num_rx_queues(be->vif->dev, requested_num_queues);
+	rtnl_unlock();
+
+	xenvif_carrier_on(be->vif);
+
+	unregister_hotplug_status_watch(be);
+	err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch,
+				   hotplug_status_changed,
+				   "%s/%s", dev->nodename, "hotplug-status");
+	if (!err)
+		be->have_hotplug_status_watch = 1;
+
+	netif_tx_wake_all_queues(be->vif->dev);
+
+	return;
+
+err:
+	if (be->vif->num_queues > 0)
+		xenvif_disconnect(be->vif); /* Clean up existing queues */
+	vfree(be->vif->queues);
+	be->vif->queues = NULL;
+	be->vif->num_queues = 0;
+	return;
+}
+
+
+static int connect_rings(struct backend_info *be, struct xenvif_queue *queue)
+{
+	struct xenbus_device *dev = be->dev;
+	unsigned int num_queues = queue->vif->num_queues;
+	unsigned long tx_ring_ref, rx_ring_ref;
+	unsigned int tx_evtchn, rx_evtchn;
+	int err;
+	char *xspath;
+	size_t xspathsize;
+	const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
+
+	/* If the frontend requested 1 queue, or we have fallen back
+	 * to single queue due to lack of frontend support for multi-
+	 * queue, expect the remaining XenStore keys in the toplevel
+	 * directory. Otherwise, expect them in a subdirectory called
+	 * queue-N.
+	 */
+	if (num_queues == 1) {
+		xspath = kzalloc(strlen(dev->otherend) + 1, GFP_KERNEL);
+		if (!xspath) {
+			xenbus_dev_fatal(dev, -ENOMEM,
+					 "reading ring references");
+			return -ENOMEM;
+		}
+		strcpy(xspath, dev->otherend);
+	} else {
+		xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
+		xspath = kzalloc(xspathsize, GFP_KERNEL);
+		if (!xspath) {
+			xenbus_dev_fatal(dev, -ENOMEM,
+					 "reading ring references");
+			return -ENOMEM;
+		}
+		snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend,
+			 queue->id);
+	}
+
+	err = xenbus_gather(XBT_NIL, xspath,
+			    "tx-ring-ref", "%lu", &tx_ring_ref,
+			    "rx-ring-ref", "%lu", &rx_ring_ref, NULL);
+	if (err) {
+		xenbus_dev_fatal(dev, err,
+				 "reading %s/ring-ref",
+				 xspath);
+		goto err;
+	}
+
+	/* Try split event channels first, then single event channel. */
+	err = xenbus_gather(XBT_NIL, xspath,
+			    "event-channel-tx", "%u", &tx_evtchn,
+			    "event-channel-rx", "%u", &rx_evtchn, NULL);
+	if (err < 0) {
+		err = xenbus_scanf(XBT_NIL, xspath,
+				   "event-channel", "%u", &tx_evtchn);
+		if (err < 0) {
+			xenbus_dev_fatal(dev, err,
+					 "reading %s/event-channel(-tx/rx)",
+					 xspath);
+			goto err;
+		}
+		rx_evtchn = tx_evtchn;
+	}
+
+	/* Map the shared frame, irq etc. */
+	err = xenvif_connect(queue, tx_ring_ref, rx_ring_ref,
+			     tx_evtchn, rx_evtchn);
+	if (err) {
+		xenbus_dev_fatal(dev, err,
+				 "mapping shared-frames %lu/%lu port tx %u rx %u",
+				 tx_ring_ref, rx_ring_ref,
+				 tx_evtchn, rx_evtchn);
+		goto err;
+	}
+
+	err = 0;
+err: /* Regular return falls through with err == 0 */
+	kfree(xspath);
+	return err;
+}
+
+static int read_xenbus_vif_flags(struct backend_info *be)
+{
+	struct xenvif *vif = be->vif;
+	struct xenbus_device *dev = be->dev;
+	unsigned int rx_copy;
+	int err, val;
+
+	err = xenbus_scanf(XBT_NIL, dev->otherend, "request-rx-copy", "%u",
+			   &rx_copy);
+	if (err == -ENOENT) {
+		err = 0;
+		rx_copy = 0;
+	}
+	if (err < 0) {
+		xenbus_dev_fatal(dev, err, "reading %s/request-rx-copy",
+				 dev->otherend);
+		return err;
+	}
+	if (!rx_copy)
+		return -EOPNOTSUPP;
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend,
+			 "feature-rx-notify", "%d", &val) < 0)
+		val = 0;
+	if (!val) {
+		/* - Reduce drain timeout to poll more frequently for
+		 *   Rx requests.
+		 * - Disable Rx stall detection.
+		 */
+		be->vif->drain_timeout = msecs_to_jiffies(30);
+		be->vif->stall_timeout = 0;
+	}
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg",
+			 "%d", &val) < 0)
+		val = 0;
+	vif->can_sg = !!val;
+
+	vif->gso_mask = 0;
+	vif->gso_prefix_mask = 0;
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_mask |= GSO_BIT(TCPV4);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv4-prefix",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_prefix_mask |= GSO_BIT(TCPV4);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_mask |= GSO_BIT(TCPV6);
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-gso-tcpv6-prefix",
+			 "%d", &val) < 0)
+		val = 0;
+	if (val)
+		vif->gso_prefix_mask |= GSO_BIT(TCPV6);
+
+	if (vif->gso_mask & vif->gso_prefix_mask) {
+		xenbus_dev_fatal(dev, err,
+				 "%s: gso and gso prefix flags are not "
+				 "mutually exclusive",
+				 dev->otherend);
+		return -EOPNOTSUPP;
+	}
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-no-csum-offload",
+			 "%d", &val) < 0)
+		val = 0;
+	vif->ip_csum = !val;
+
+	if (xenbus_scanf(XBT_NIL, dev->otherend, "feature-ipv6-csum-offload",
+			 "%d", &val) < 0)
+		val = 0;
+	vif->ipv6_csum = !!val;
+
+	return 0;
+}
+
+static const struct xenbus_device_id netback_ids[] = {
+	{ "vif" },
+	{ "" }
+};
+
+static struct xenbus_driver netback_driver = {
+	.ids = netback_ids,
+	.probe = netback_probe,
+	.remove = netback_remove,
+	.uevent = netback_uevent,
+	.otherend_changed = frontend_changed,
+};
+
+int xenvif_xenbus_init(void)
+{
+	return xenbus_register_backend(&netback_driver);
+}
+
+void xenvif_xenbus_fini(void)
+{
+	return xenbus_unregister_driver(&netback_driver);
+}