Initial import

9 files changed, 6773 insertions, 0 deletions

diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
new file mode 100644
index 000000000..017a1e8a8
--- /dev/null
+++ b/drivers/vhost/Kconfig
@@ -0,0 +1,34 @@
+config VHOST_NET
+	tristate "Host kernel accelerator for virtio net"
+	depends on NET && EVENTFD && (TUN || !TUN) && (MACVTAP || !MACVTAP)
+	select VHOST
+	select VHOST_RING
+	---help---
+	  This kernel module can be loaded in host kernel to accelerate
+	  guest networking with virtio_net. Not to be confused with virtio_net
+	  module itself which needs to be loaded in guest kernel.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called vhost_net.
+
+config VHOST_SCSI
+	tristate "VHOST_SCSI TCM fabric driver"
+	depends on TARGET_CORE && EVENTFD && m
+	select VHOST
+	select VHOST_RING
+	default n
+	---help---
+	Say M here to enable the vhost_scsi TCM fabric module
+	for use with virtio-scsi guests
+
+config VHOST_RING
+	tristate
+	---help---
+	  This option is selected by any driver which needs to access
+	  the host side of a virtio ring.
+
+config VHOST
+	tristate
+	---help---
+	  This option is selected by any driver which needs to access
+	  the core of vhost.
diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
new file mode 100644
index 000000000..e0441c34d
--- /dev/null
+++ b/drivers/vhost/Makefile
@@ -0,0 +1,8 @@
+obj-$(CONFIG_VHOST_NET) += vhost_net.o
+vhost_net-y := net.o
+
+obj-$(CONFIG_VHOST_SCSI) += vhost_scsi.o
+vhost_scsi-y := scsi.o
+
+obj-$(CONFIG_VHOST_RING) += vringh.o
+obj-$(CONFIG_VHOST)	+= vhost.o
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
new file mode 100644
index 000000000..7d137a43c
--- /dev/null
+++ b/drivers/vhost/net.c
@@ -0,0 +1,1138 @@
+/* Copyright (C) 2009 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * virtio-net server in host kernel.
+ */
+
+#include <linux/compat.h>
+#include <linux/eventfd.h>
+#include <linux/vhost.h>
+#include <linux/virtio_net.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/mutex.h>
+#include <linux/workqueue.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+#include <linux/net.h>
+#include <linux/if_packet.h>
+#include <linux/if_arp.h>
+#include <linux/if_tun.h>
+#include <linux/if_macvlan.h>
+#include <linux/if_vlan.h>
+
+#include <net/sock.h>
+
+#include "vhost.h"
+
+static int experimental_zcopytx = 1;
+module_param(experimental_zcopytx, int, 0444);
+MODULE_PARM_DESC(experimental_zcopytx, "Enable Zero Copy TX;"
+		                       " 1 -Enable; 0 - Disable");
+
+/* Max number of bytes transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others. */
+#define VHOST_NET_WEIGHT 0x80000
+
+/* MAX number of TX used buffers for outstanding zerocopy */
+#define VHOST_MAX_PEND 128
+#define VHOST_GOODCOPY_LEN 256
+
+/*
+ * For transmit, used buffer len is unused; we override it to track buffer
+ * status internally; used for zerocopy tx only.
+ */
+/* Lower device DMA failed */
+#define VHOST_DMA_FAILED_LEN	((__force __virtio32)3)
+/* Lower device DMA done */
+#define VHOST_DMA_DONE_LEN	((__force __virtio32)2)
+/* Lower device DMA in progress */
+#define VHOST_DMA_IN_PROGRESS	((__force __virtio32)1)
+/* Buffer unused */
+#define VHOST_DMA_CLEAR_LEN	((__force __virtio32)0)
+
+#define VHOST_DMA_IS_DONE(len) ((__force u32)(len) >= (__force u32)VHOST_DMA_DONE_LEN)
+
+enum {
+	VHOST_NET_FEATURES = VHOST_FEATURES |
+			 (1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
+			 (1ULL << VIRTIO_NET_F_MRG_RXBUF) |
+			 (1ULL << VIRTIO_F_VERSION_1),
+};
+
+enum {
+	VHOST_NET_VQ_RX = 0,
+	VHOST_NET_VQ_TX = 1,
+	VHOST_NET_VQ_MAX = 2,
+};
+
+struct vhost_net_ubuf_ref {
+	/* refcount follows semantics similar to kref:
+	 *  0: object is released
+	 *  1: no outstanding ubufs
+	 * >1: outstanding ubufs
+	 */
+	atomic_t refcount;
+	wait_queue_head_t wait;
+	struct vhost_virtqueue *vq;
+};
+
+struct vhost_net_virtqueue {
+	struct vhost_virtqueue vq;
+	size_t vhost_hlen;
+	size_t sock_hlen;
+	/* vhost zerocopy support fields below: */
+	/* last used idx for outstanding DMA zerocopy buffers */
+	int upend_idx;
+	/* first used idx for DMA done zerocopy buffers */
+	int done_idx;
+	/* an array of userspace buffers info */
+	struct ubuf_info *ubuf_info;
+	/* Reference counting for outstanding ubufs.
+	 * Protected by vq mutex. Writers must also take device mutex. */
+	struct vhost_net_ubuf_ref *ubufs;
+};
+
+struct vhost_net {
+	struct vhost_dev dev;
+	struct vhost_net_virtqueue vqs[VHOST_NET_VQ_MAX];
+	struct vhost_poll poll[VHOST_NET_VQ_MAX];
+	/* Number of TX recently submitted.
+	 * Protected by tx vq lock. */
+	unsigned tx_packets;
+	/* Number of times zerocopy TX recently failed.
+	 * Protected by tx vq lock. */
+	unsigned tx_zcopy_err;
+	/* Flush in progress. Protected by tx vq lock. */
+	bool tx_flush;
+};
+
+static unsigned vhost_net_zcopy_mask __read_mostly;
+
+static void vhost_net_enable_zcopy(int vq)
+{
+	vhost_net_zcopy_mask |= 0x1 << vq;
+}
+
+static struct vhost_net_ubuf_ref *
+vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy)
+{
+	struct vhost_net_ubuf_ref *ubufs;
+	/* No zero copy backend? Nothing to count. */
+	if (!zcopy)
+		return NULL;
+	ubufs = kmalloc(sizeof(*ubufs), GFP_KERNEL);
+	if (!ubufs)
+		return ERR_PTR(-ENOMEM);
+	atomic_set(&ubufs->refcount, 1);
+	init_waitqueue_head(&ubufs->wait);
+	ubufs->vq = vq;
+	return ubufs;
+}
+
+static int vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs)
+{
+	int r = atomic_sub_return(1, &ubufs->refcount);
+	if (unlikely(!r))
+		wake_up(&ubufs->wait);
+	return r;
+}
+
+static void vhost_net_ubuf_put_and_wait(struct vhost_net_ubuf_ref *ubufs)
+{
+	vhost_net_ubuf_put(ubufs);
+	wait_event(ubufs->wait, !atomic_read(&ubufs->refcount));
+}
+
+static void vhost_net_ubuf_put_wait_and_free(struct vhost_net_ubuf_ref *ubufs)
+{
+	vhost_net_ubuf_put_and_wait(ubufs);
+	kfree(ubufs);
+}
+
+static void vhost_net_clear_ubuf_info(struct vhost_net *n)
+{
+	int i;
+
+	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
+		kfree(n->vqs[i].ubuf_info);
+		n->vqs[i].ubuf_info = NULL;
+	}
+}
+
+static int vhost_net_set_ubuf_info(struct vhost_net *n)
+{
+	bool zcopy;
+	int i;
+
+	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
+		zcopy = vhost_net_zcopy_mask & (0x1 << i);
+		if (!zcopy)
+			continue;
+		n->vqs[i].ubuf_info = kmalloc(sizeof(*n->vqs[i].ubuf_info) *
+					      UIO_MAXIOV, GFP_KERNEL);
+		if  (!n->vqs[i].ubuf_info)
+			goto err;
+	}
+	return 0;
+
+err:
+	vhost_net_clear_ubuf_info(n);
+	return -ENOMEM;
+}
+
+static void vhost_net_vq_reset(struct vhost_net *n)
+{
+	int i;
+
+	vhost_net_clear_ubuf_info(n);
+
+	for (i = 0; i < VHOST_NET_VQ_MAX; i++) {
+		n->vqs[i].done_idx = 0;
+		n->vqs[i].upend_idx = 0;
+		n->vqs[i].ubufs = NULL;
+		n->vqs[i].vhost_hlen = 0;
+		n->vqs[i].sock_hlen = 0;
+	}
+
+}
+
+static void vhost_net_tx_packet(struct vhost_net *net)
+{
+	++net->tx_packets;
+	if (net->tx_packets < 1024)
+		return;
+	net->tx_packets = 0;
+	net->tx_zcopy_err = 0;
+}
+
+static void vhost_net_tx_err(struct vhost_net *net)
+{
+	++net->tx_zcopy_err;
+}
+
+static bool vhost_net_tx_select_zcopy(struct vhost_net *net)
+{
+	/* TX flush waits for outstanding DMAs to be done.
+	 * Don't start new DMAs.
+	 */
+	return !net->tx_flush &&
+		net->tx_packets / 64 >= net->tx_zcopy_err;
+}
+
+static bool vhost_sock_zcopy(struct socket *sock)
+{
+	return unlikely(experimental_zcopytx) &&
+		sock_flag(sock->sk, SOCK_ZEROCOPY);
+}
+
+/* In case of DMA done not in order in lower device driver for some reason.
+ * upend_idx is used to track end of used idx, done_idx is used to track head
+ * of used idx. Once lower device DMA done contiguously, we will signal KVM
+ * guest used idx.
+ */
+static void vhost_zerocopy_signal_used(struct vhost_net *net,
+				       struct vhost_virtqueue *vq)
+{
+	struct vhost_net_virtqueue *nvq =
+		container_of(vq, struct vhost_net_virtqueue, vq);
+	int i, add;
+	int j = 0;
+
+	for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
+		if (vq->heads[i].len == VHOST_DMA_FAILED_LEN)
+			vhost_net_tx_err(net);
+		if (VHOST_DMA_IS_DONE(vq->heads[i].len)) {
+			vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
+			++j;
+		} else
+			break;
+	}
+	while (j) {
+		add = min(UIO_MAXIOV - nvq->done_idx, j);
+		vhost_add_used_and_signal_n(vq->dev, vq,
+					    &vq->heads[nvq->done_idx], add);
+		nvq->done_idx = (nvq->done_idx + add) % UIO_MAXIOV;
+		j -= add;
+	}
+}
+
+static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
+{
+	struct vhost_net_ubuf_ref *ubufs = ubuf->ctx;
+	struct vhost_virtqueue *vq = ubufs->vq;
+	int cnt;
+
+	rcu_read_lock_bh();
+
+	/* set len to mark this desc buffers done DMA */
+	vq->heads[ubuf->desc].len = success ?
+		VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;
+	cnt = vhost_net_ubuf_put(ubufs);
+
+	/*
+	 * Trigger polling thread if guest stopped submitting new buffers:
+	 * in this case, the refcount after decrement will eventually reach 1.
+	 * We also trigger polling periodically after each 16 packets
+	 * (the value 16 here is more or less arbitrary, it's tuned to trigger
+	 * less than 10% of times).
+	 */
+	if (cnt <= 1 || !(cnt % 16))
+		vhost_poll_queue(&vq->poll);
+
+	rcu_read_unlock_bh();
+}
+
+/* Expects to be always run from workqueue - which acts as
+ * read-size critical section for our kind of RCU. */
+static void handle_tx(struct vhost_net *net)
+{
+	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
+	struct vhost_virtqueue *vq = &nvq->vq;
+	unsigned out, in;
+	int head;
+	struct msghdr msg = {
+		.msg_name = NULL,
+		.msg_namelen = 0,
+		.msg_control = NULL,
+		.msg_controllen = 0,
+		.msg_flags = MSG_DONTWAIT,
+	};
+	size_t len, total_len = 0;
+	int err;
+	size_t hdr_size;
+	struct socket *sock;
+	struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
+	bool zcopy, zcopy_used;
+
+	mutex_lock(&vq->mutex);
+	sock = vq->private_data;
+	if (!sock)
+		goto out;
+
+	vhost_disable_notify(&net->dev, vq);
+
+	hdr_size = nvq->vhost_hlen;
+	zcopy = nvq->ubufs;
+
+	for (;;) {
+		/* Release DMAs done buffers first */
+		if (zcopy)
+			vhost_zerocopy_signal_used(net, vq);
+
+		/* If more outstanding DMAs, queue the work.
+		 * Handle upend_idx wrap around
+		 */
+		if (unlikely((nvq->upend_idx + vq->num - VHOST_MAX_PEND)
+			      % UIO_MAXIOV == nvq->done_idx))
+			break;
+
+		head = vhost_get_vq_desc(vq, vq->iov,
+					 ARRAY_SIZE(vq->iov),
+					 &out, &in,
+					 NULL, NULL);
+		/* On error, stop handling until the next kick. */
+		if (unlikely(head < 0))
+			break;
+		/* Nothing new?  Wait for eventfd to tell us they refilled. */
+		if (head == vq->num) {
+			if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+				vhost_disable_notify(&net->dev, vq);
+				continue;
+			}
+			break;
+		}
+		if (in) {
+			vq_err(vq, "Unexpected descriptor format for TX: "
+			       "out %d, int %d\n", out, in);
+			break;
+		}
+		/* Skip header. TODO: support TSO. */
+		len = iov_length(vq->iov, out);
+		iov_iter_init(&msg.msg_iter, WRITE, vq->iov, out, len);
+		iov_iter_advance(&msg.msg_iter, hdr_size);
+		/* Sanity check */
+		if (!msg_data_left(&msg)) {
+			vq_err(vq, "Unexpected header len for TX: "
+			       "%zd expected %zd\n",
+			       len, hdr_size);
+			break;
+		}
+		len = msg_data_left(&msg);
+
+		zcopy_used = zcopy && len >= VHOST_GOODCOPY_LEN
+				   && (nvq->upend_idx + 1) % UIO_MAXIOV !=
+				      nvq->done_idx
+				   && vhost_net_tx_select_zcopy(net);
+
+		/* use msg_control to pass vhost zerocopy ubuf info to skb */
+		if (zcopy_used) {
+			struct ubuf_info *ubuf;
+			ubuf = nvq->ubuf_info + nvq->upend_idx;
+
+			vq->heads[nvq->upend_idx].id = cpu_to_vhost32(vq, head);
+			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
+			ubuf->callback = vhost_zerocopy_callback;
+			ubuf->ctx = nvq->ubufs;
+			ubuf->desc = nvq->upend_idx;
+			msg.msg_control = ubuf;
+			msg.msg_controllen = sizeof(ubuf);
+			ubufs = nvq->ubufs;
+			atomic_inc(&ubufs->refcount);
+			nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;
+		} else {
+			msg.msg_control = NULL;
+			ubufs = NULL;
+		}
+		/* TODO: Check specific error and bomb out unless ENOBUFS? */
+		err = sock->ops->sendmsg(sock, &msg, len);
+		if (unlikely(err < 0)) {
+			if (zcopy_used) {
+				vhost_net_ubuf_put(ubufs);
+				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
+					% UIO_MAXIOV;
+			}
+			vhost_discard_vq_desc(vq, 1);
+			break;
+		}
+		if (err != len)
+			pr_debug("Truncated TX packet: "
+				 " len %d != %zd\n", err, len);
+		if (!zcopy_used)
+			vhost_add_used_and_signal(&net->dev, vq, head, 0);
+		else
+			vhost_zerocopy_signal_used(net, vq);
+		total_len += len;
+		vhost_net_tx_packet(net);
+		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
+			vhost_poll_queue(&vq->poll);
+			break;
+		}
+	}
+out:
+	mutex_unlock(&vq->mutex);
+}
+
+static int peek_head_len(struct sock *sk)
+{
+	struct sk_buff *head;
+	int len = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&sk->sk_receive_queue.lock, flags);
+	head = skb_peek(&sk->sk_receive_queue);
+	if (likely(head)) {
+		len = head->len;
+		if (skb_vlan_tag_present(head))
+			len += VLAN_HLEN;
+	}
+
+	spin_unlock_irqrestore(&sk->sk_receive_queue.lock, flags);
+	return len;
+}
+
+/* This is a multi-buffer version of vhost_get_desc, that works if
+ *	vq has read descriptors only.
+ * @vq		- the relevant virtqueue
+ * @datalen	- data length we'll be reading
+ * @iovcount	- returned count of io vectors we fill
+ * @log		- vhost log
+ * @log_num	- log offset
+ * @quota       - headcount quota, 1 for big buffer
+ *	returns number of buffer heads allocated, negative on error
+ */
+static int get_rx_bufs(struct vhost_virtqueue *vq,
+		       struct vring_used_elem *heads,
+		       int datalen,
+		       unsigned *iovcount,
+		       struct vhost_log *log,
+		       unsigned *log_num,
+		       unsigned int quota)
+{
+	unsigned int out, in;
+	int seg = 0;
+	int headcount = 0;
+	unsigned d;
+	int r, nlogs = 0;
+	/* len is always initialized before use since we are always called with
+	 * datalen > 0.
+	 */
+	u32 uninitialized_var(len);
+
+	while (datalen > 0 && headcount < quota) {
+		if (unlikely(seg >= UIO_MAXIOV)) {
+			r = -ENOBUFS;
+			goto err;
+		}
+		r = vhost_get_vq_desc(vq, vq->iov + seg,
+				      ARRAY_SIZE(vq->iov) - seg, &out,
+				      &in, log, log_num);
+		if (unlikely(r < 0))
+			goto err;
+
+		d = r;
+		if (d == vq->num) {
+			r = 0;
+			goto err;
+		}
+		if (unlikely(out || in <= 0)) {
+			vq_err(vq, "unexpected descriptor format for RX: "
+				"out %d, in %d\n", out, in);
+			r = -EINVAL;
+			goto err;
+		}
+		if (unlikely(log)) {
+			nlogs += *log_num;
+			log += *log_num;
+		}
+		heads[headcount].id = cpu_to_vhost32(vq, d);
+		len = iov_length(vq->iov + seg, in);
+		heads[headcount].len = cpu_to_vhost32(vq, len);
+		datalen -= len;
+		++headcount;
+		seg += in;
+	}
+	heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
+	*iovcount = seg;
+	if (unlikely(log))
+		*log_num = nlogs;
+
+	/* Detect overrun */
+	if (unlikely(datalen > 0)) {
+		r = UIO_MAXIOV + 1;
+		goto err;
+	}
+	return headcount;
+err:
+	vhost_discard_vq_desc(vq, headcount);
+	return r;
+}
+
+/* Expects to be always run from workqueue - which acts as
+ * read-size critical section for our kind of RCU. */
+static void handle_rx(struct vhost_net *net)
+{
+	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_RX];
+	struct vhost_virtqueue *vq = &nvq->vq;
+	unsigned uninitialized_var(in), log;
+	struct vhost_log *vq_log;
+	struct msghdr msg = {
+		.msg_name = NULL,
+		.msg_namelen = 0,
+		.msg_control = NULL, /* FIXME: get and handle RX aux data. */
+		.msg_controllen = 0,
+		.msg_flags = MSG_DONTWAIT,
+	};
+	struct virtio_net_hdr hdr = {
+		.flags = 0,
+		.gso_type = VIRTIO_NET_HDR_GSO_NONE
+	};
+	size_t total_len = 0;
+	int err, mergeable;
+	s16 headcount;
+	size_t vhost_hlen, sock_hlen;
+	size_t vhost_len, sock_len;
+	struct socket *sock;
+	struct iov_iter fixup;
+	__virtio16 num_buffers;
+
+	mutex_lock(&vq->mutex);
+	sock = vq->private_data;
+	if (!sock)
+		goto out;
+	vhost_disable_notify(&net->dev, vq);
+
+	vhost_hlen = nvq->vhost_hlen;
+	sock_hlen = nvq->sock_hlen;
+
+	vq_log = unlikely(vhost_has_feature(vq, VHOST_F_LOG_ALL)) ?
+		vq->log : NULL;
+	mergeable = vhost_has_feature(vq, VIRTIO_NET_F_MRG_RXBUF);
+
+	while ((sock_len = peek_head_len(sock->sk))) {
+		sock_len += sock_hlen;
+		vhost_len = sock_len + vhost_hlen;
+		headcount = get_rx_bufs(vq, vq->heads, vhost_len,
+					&in, vq_log, &log,
+					likely(mergeable) ? UIO_MAXIOV : 1);
+		/* On error, stop handling until the next kick. */
+		if (unlikely(headcount < 0))
+			break;
+		/* On overrun, truncate and discard */
+		if (unlikely(headcount > UIO_MAXIOV)) {
+			iov_iter_init(&msg.msg_iter, READ, vq->iov, 1, 1);
+			err = sock->ops->recvmsg(sock, &msg,
+						 1, MSG_DONTWAIT | MSG_TRUNC);
+			pr_debug("Discarded rx packet: len %zd\n", sock_len);
+			continue;
+		}
+		/* OK, now we need to know about added descriptors. */
+		if (!headcount) {
+			if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+				/* They have slipped one in as we were
+				 * doing that: check again. */
+				vhost_disable_notify(&net->dev, vq);
+				continue;
+			}
+			/* Nothing new?  Wait for eventfd to tell us
+			 * they refilled. */
+			break;
+		}
+		/* We don't need to be notified again. */
+		iov_iter_init(&msg.msg_iter, READ, vq->iov, in, vhost_len);
+		fixup = msg.msg_iter;
+		if (unlikely((vhost_hlen))) {
+			/* We will supply the header ourselves
+			 * TODO: support TSO.
+			 */
+			iov_iter_advance(&msg.msg_iter, vhost_hlen);
+		}
+		err = sock->ops->recvmsg(sock, &msg,
+					 sock_len, MSG_DONTWAIT | MSG_TRUNC);
+		/* Userspace might have consumed the packet meanwhile:
+		 * it's not supposed to do this usually, but might be hard
+		 * to prevent. Discard data we got (if any) and keep going. */
+		if (unlikely(err != sock_len)) {
+			pr_debug("Discarded rx packet: "
+				 " len %d, expected %zd\n", err, sock_len);
+			vhost_discard_vq_desc(vq, headcount);
+			continue;
+		}
+		/* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
+		if (unlikely(vhost_hlen)) {
+			if (copy_to_iter(&hdr, sizeof(hdr),
+					 &fixup) != sizeof(hdr)) {
+				vq_err(vq, "Unable to write vnet_hdr "
+				       "at addr %p\n", vq->iov->iov_base);
+				break;
+			}
+		} else {
+			/* Header came from socket; we'll need to patch
+			 * ->num_buffers over if VIRTIO_NET_F_MRG_RXBUF
+			 */
+			iov_iter_advance(&fixup, sizeof(hdr));
+		}
+		/* TODO: Should check and handle checksum. */
+
+		num_buffers = cpu_to_vhost16(vq, headcount);
+		if (likely(mergeable) &&
+		    copy_to_iter(&num_buffers, sizeof num_buffers,
+				 &fixup) != sizeof num_buffers) {
+			vq_err(vq, "Failed num_buffers write");
+			vhost_discard_vq_desc(vq, headcount);
+			break;
+		}
+		vhost_add_used_and_signal_n(&net->dev, vq, vq->heads,
+					    headcount);
+		if (unlikely(vq_log))
+			vhost_log_write(vq, vq_log, log, vhost_len);
+		total_len += vhost_len;
+		if (unlikely(total_len >= VHOST_NET_WEIGHT)) {
+			vhost_poll_queue(&vq->poll);
+			break;
+		}
+	}
+out:
+	mutex_unlock(&vq->mutex);
+}
+
+static void handle_tx_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						  poll.work);
+	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);
+
+	handle_tx(net);
+}
+
+static void handle_rx_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						  poll.work);
+	struct vhost_net *net = container_of(vq->dev, struct vhost_net, dev);
+
+	handle_rx(net);
+}
+
+static void handle_tx_net(struct vhost_work *work)
+{
+	struct vhost_net *net = container_of(work, struct vhost_net,
+					     poll[VHOST_NET_VQ_TX].work);
+	handle_tx(net);
+}
+
+static void handle_rx_net(struct vhost_work *work)
+{
+	struct vhost_net *net = container_of(work, struct vhost_net,
+					     poll[VHOST_NET_VQ_RX].work);
+	handle_rx(net);
+}
+
+static int vhost_net_open(struct inode *inode, struct file *f)
+{
+	struct vhost_net *n;
+	struct vhost_dev *dev;
+	struct vhost_virtqueue **vqs;
+	int i;
+
+	n = kmalloc(sizeof *n, GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
+	if (!n) {
+		n = vmalloc(sizeof *n);
+		if (!n)
+			return -ENOMEM;
+	}
+	vqs = kmalloc(VHOST_NET_VQ_MAX * sizeof(*vqs), GFP_KERNEL);
+	if (!vqs) {
+		kvfree(n);
+		return -ENOMEM;
+	}
+
+	dev = &n->dev;
+	vqs[VHOST_NET_VQ_TX] = &n->vqs[VHOST_NET_VQ_TX].vq;
+	vqs[VHOST_NET_VQ_RX] = &n->vqs[VHOST_NET_VQ_RX].vq;
+	n->vqs[VHOST_NET_VQ_TX].vq.handle_kick = handle_tx_kick;
+	n->vqs[VHOST_NET_VQ_RX].vq.handle_kick = handle_rx_kick;
+	for (i = 0; i < VHOST_NET_VQ_MAX; i++) {
+		n->vqs[i].ubufs = NULL;
+		n->vqs[i].ubuf_info = NULL;
+		n->vqs[i].upend_idx = 0;
+		n->vqs[i].done_idx = 0;
+		n->vqs[i].vhost_hlen = 0;
+		n->vqs[i].sock_hlen = 0;
+	}
+	vhost_dev_init(dev, vqs, VHOST_NET_VQ_MAX);
+
+	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT, dev);
+	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN, dev);
+
+	f->private_data = n;
+
+	return 0;
+}
+
+static void vhost_net_disable_vq(struct vhost_net *n,
+				 struct vhost_virtqueue *vq)
+{
+	struct vhost_net_virtqueue *nvq =
+		container_of(vq, struct vhost_net_virtqueue, vq);
+	struct vhost_poll *poll = n->poll + (nvq - n->vqs);
+	if (!vq->private_data)
+		return;
+	vhost_poll_stop(poll);
+}
+
+static int vhost_net_enable_vq(struct vhost_net *n,
+				struct vhost_virtqueue *vq)
+{
+	struct vhost_net_virtqueue *nvq =
+		container_of(vq, struct vhost_net_virtqueue, vq);
+	struct vhost_poll *poll = n->poll + (nvq - n->vqs);
+	struct socket *sock;
+
+	sock = vq->private_data;
+	if (!sock)
+		return 0;
+
+	return vhost_poll_start(poll, sock->file);
+}
+
+static struct socket *vhost_net_stop_vq(struct vhost_net *n,
+					struct vhost_virtqueue *vq)
+{
+	struct socket *sock;
+
+	mutex_lock(&vq->mutex);
+	sock = vq->private_data;
+	vhost_net_disable_vq(n, vq);
+	vq->private_data = NULL;
+	mutex_unlock(&vq->mutex);
+	return sock;
+}
+
+static void vhost_net_stop(struct vhost_net *n, struct socket **tx_sock,
+			   struct socket **rx_sock)
+{
+	*tx_sock = vhost_net_stop_vq(n, &n->vqs[VHOST_NET_VQ_TX].vq);
+	*rx_sock = vhost_net_stop_vq(n, &n->vqs[VHOST_NET_VQ_RX].vq);
+}
+
+static void vhost_net_flush_vq(struct vhost_net *n, int index)
+{
+	vhost_poll_flush(n->poll + index);
+	vhost_poll_flush(&n->vqs[index].vq.poll);
+}
+
+static void vhost_net_flush(struct vhost_net *n)
+{
+	vhost_net_flush_vq(n, VHOST_NET_VQ_TX);
+	vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
+	if (n->vqs[VHOST_NET_VQ_TX].ubufs) {
+		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+		n->tx_flush = true;
+		mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+		/* Wait for all lower device DMAs done. */
+		vhost_net_ubuf_put_and_wait(n->vqs[VHOST_NET_VQ_TX].ubufs);
+		mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+		n->tx_flush = false;
+		atomic_set(&n->vqs[VHOST_NET_VQ_TX].ubufs->refcount, 1);
+		mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
+	}
+}
+
+static int vhost_net_release(struct inode *inode, struct file *f)
+{
+	struct vhost_net *n = f->private_data;
+	struct socket *tx_sock;
+	struct socket *rx_sock;
+
+	vhost_net_stop(n, &tx_sock, &rx_sock);
+	vhost_net_flush(n);
+	vhost_dev_stop(&n->dev);
+	vhost_dev_cleanup(&n->dev, false);
+	vhost_net_vq_reset(n);
+	if (tx_sock)
+		sockfd_put(tx_sock);
+	if (rx_sock)
+		sockfd_put(rx_sock);
+	/* Make sure no callbacks are outstanding */
+	synchronize_rcu_bh();
+	/* We do an extra flush before freeing memory,
+	 * since jobs can re-queue themselves. */
+	vhost_net_flush(n);
+	kfree(n->dev.vqs);
+	kvfree(n);
+	return 0;
+}
+
+static struct socket *get_raw_socket(int fd)
+{
+	struct {
+		struct sockaddr_ll sa;
+		char  buf[MAX_ADDR_LEN];
+	} uaddr;
+	int uaddr_len = sizeof uaddr, r;
+	struct socket *sock = sockfd_lookup(fd, &r);
+
+	if (!sock)
+		return ERR_PTR(-ENOTSOCK);
+
+	/* Parameter checking */
+	if (sock->sk->sk_type != SOCK_RAW) {
+		r = -ESOCKTNOSUPPORT;
+		goto err;
+	}
+
+	r = sock->ops->getname(sock, (struct sockaddr *)&uaddr.sa,
+			       &uaddr_len, 0);
+	if (r)
+		goto err;
+
+	if (uaddr.sa.sll_family != AF_PACKET) {
+		r = -EPFNOSUPPORT;
+		goto err;
+	}
+	return sock;
+err:
+	sockfd_put(sock);
+	return ERR_PTR(r);
+}
+
+static struct socket *get_tap_socket(int fd)
+{
+	struct file *file = fget(fd);
+	struct socket *sock;
+
+	if (!file)
+		return ERR_PTR(-EBADF);
+	sock = tun_get_socket(file);
+	if (!IS_ERR(sock))
+		return sock;
+	sock = macvtap_get_socket(file);
+	if (IS_ERR(sock))
+		fput(file);
+	return sock;
+}
+
+static struct socket *get_socket(int fd)
+{
+	struct socket *sock;
+
+	/* special case to disable backend */
+	if (fd == -1)
+		return NULL;
+	sock = get_raw_socket(fd);
+	if (!IS_ERR(sock))
+		return sock;
+	sock = get_tap_socket(fd);
+	if (!IS_ERR(sock))
+		return sock;
+	return ERR_PTR(-ENOTSOCK);
+}
+
+static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
+{
+	struct socket *sock, *oldsock;
+	struct vhost_virtqueue *vq;
+	struct vhost_net_virtqueue *nvq;
+	struct vhost_net_ubuf_ref *ubufs, *oldubufs = NULL;
+	int r;
+
+	mutex_lock(&n->dev.mutex);
+	r = vhost_dev_check_owner(&n->dev);
+	if (r)
+		goto err;
+
+	if (index >= VHOST_NET_VQ_MAX) {
+		r = -ENOBUFS;
+		goto err;
+	}
+	vq = &n->vqs[index].vq;
+	nvq = &n->vqs[index];
+	mutex_lock(&vq->mutex);
+
+	/* Verify that ring has been setup correctly. */
+	if (!vhost_vq_access_ok(vq)) {
+		r = -EFAULT;
+		goto err_vq;
+	}
+	sock = get_socket(fd);
+	if (IS_ERR(sock)) {
+		r = PTR_ERR(sock);
+		goto err_vq;
+	}
+
+	/* start polling new socket */
+	oldsock = vq->private_data;
+	if (sock != oldsock) {
+		ubufs = vhost_net_ubuf_alloc(vq,
+					     sock && vhost_sock_zcopy(sock));
+		if (IS_ERR(ubufs)) {
+			r = PTR_ERR(ubufs);
+			goto err_ubufs;
+		}
+
+		vhost_net_disable_vq(n, vq);
+		vq->private_data = sock;
+		r = vhost_init_used(vq);
+		if (r)
+			goto err_used;
+		r = vhost_net_enable_vq(n, vq);
+		if (r)
+			goto err_used;
+
+		oldubufs = nvq->ubufs;
+		nvq->ubufs = ubufs;
+
+		n->tx_packets = 0;
+		n->tx_zcopy_err = 0;
+		n->tx_flush = false;
+	}
+
+	mutex_unlock(&vq->mutex);
+
+	if (oldubufs) {
+		vhost_net_ubuf_put_wait_and_free(oldubufs);
+		mutex_lock(&vq->mutex);
+		vhost_zerocopy_signal_used(n, vq);
+		mutex_unlock(&vq->mutex);
+	}
+
+	if (oldsock) {
+		vhost_net_flush_vq(n, index);
+		sockfd_put(oldsock);
+	}
+
+	mutex_unlock(&n->dev.mutex);
+	return 0;
+
+err_used:
+	vq->private_data = oldsock;
+	vhost_net_enable_vq(n, vq);
+	if (ubufs)
+		vhost_net_ubuf_put_wait_and_free(ubufs);
+err_ubufs:
+	sockfd_put(sock);
+err_vq:
+	mutex_unlock(&vq->mutex);
+err:
+	mutex_unlock(&n->dev.mutex);
+	return r;
+}
+
+static long vhost_net_reset_owner(struct vhost_net *n)
+{
+	struct socket *tx_sock = NULL;
+	struct socket *rx_sock = NULL;
+	long err;
+	struct vhost_memory *memory;
+
+	mutex_lock(&n->dev.mutex);
+	err = vhost_dev_check_owner(&n->dev);
+	if (err)
+		goto done;
+	memory = vhost_dev_reset_owner_prepare();
+	if (!memory) {
+		err = -ENOMEM;
+		goto done;
+	}
+	vhost_net_stop(n, &tx_sock, &rx_sock);
+	vhost_net_flush(n);
+	vhost_dev_reset_owner(&n->dev, memory);
+	vhost_net_vq_reset(n);
+done:
+	mutex_unlock(&n->dev.mutex);
+	if (tx_sock)
+		sockfd_put(tx_sock);
+	if (rx_sock)
+		sockfd_put(rx_sock);
+	return err;
+}
+
+static int vhost_net_set_features(struct vhost_net *n, u64 features)
+{
+	size_t vhost_hlen, sock_hlen, hdr_len;
+	int i;
+
+	hdr_len = (features & ((1ULL << VIRTIO_NET_F_MRG_RXBUF) |
+			       (1ULL << VIRTIO_F_VERSION_1))) ?
+			sizeof(struct virtio_net_hdr_mrg_rxbuf) :
+			sizeof(struct virtio_net_hdr);
+	if (features & (1 << VHOST_NET_F_VIRTIO_NET_HDR)) {
+		/* vhost provides vnet_hdr */
+		vhost_hlen = hdr_len;
+		sock_hlen = 0;
+	} else {
+		/* socket provides vnet_hdr */
+		vhost_hlen = 0;
+		sock_hlen = hdr_len;
+	}
+	mutex_lock(&n->dev.mutex);
+	if ((features & (1 << VHOST_F_LOG_ALL)) &&
+	    !vhost_log_access_ok(&n->dev)) {
+		mutex_unlock(&n->dev.mutex);
+		return -EFAULT;
+	}
+	for (i = 0; i < VHOST_NET_VQ_MAX; ++i) {
+		mutex_lock(&n->vqs[i].vq.mutex);
+		n->vqs[i].vq.acked_features = features;
+		n->vqs[i].vhost_hlen = vhost_hlen;
+		n->vqs[i].sock_hlen = sock_hlen;
+		mutex_unlock(&n->vqs[i].vq.mutex);
+	}
+	mutex_unlock(&n->dev.mutex);
+	return 0;
+}
+
+static long vhost_net_set_owner(struct vhost_net *n)
+{
+	int r;
+
+	mutex_lock(&n->dev.mutex);
+	if (vhost_dev_has_owner(&n->dev)) {
+		r = -EBUSY;
+		goto out;
+	}
+	r = vhost_net_set_ubuf_info(n);
+	if (r)
+		goto out;
+	r = vhost_dev_set_owner(&n->dev);
+	if (r)
+		vhost_net_clear_ubuf_info(n);
+	vhost_net_flush(n);
+out:
+	mutex_unlock(&n->dev.mutex);
+	return r;
+}
+
+static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
+			    unsigned long arg)
+{
+	struct vhost_net *n = f->private_data;
+	void __user *argp = (void __user *)arg;
+	u64 __user *featurep = argp;
+	struct vhost_vring_file backend;
+	u64 features;
+	int r;
+
+	switch (ioctl) {
+	case VHOST_NET_SET_BACKEND:
+		if (copy_from_user(&backend, argp, sizeof backend))
+			return -EFAULT;
+		return vhost_net_set_backend(n, backend.index, backend.fd);
+	case VHOST_GET_FEATURES:
+		features = VHOST_NET_FEATURES;
+		if (copy_to_user(featurep, &features, sizeof features))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES:
+		if (copy_from_user(&features, featurep, sizeof features))
+			return -EFAULT;
+		if (features & ~VHOST_NET_FEATURES)
+			return -EOPNOTSUPP;
+		return vhost_net_set_features(n, features);
+	case VHOST_RESET_OWNER:
+		return vhost_net_reset_owner(n);
+	case VHOST_SET_OWNER:
+		return vhost_net_set_owner(n);
+	default:
+		mutex_lock(&n->dev.mutex);
+		r = vhost_dev_ioctl(&n->dev, ioctl, argp);
+		if (r == -ENOIOCTLCMD)
+			r = vhost_vring_ioctl(&n->dev, ioctl, argp);
+		else
+			vhost_net_flush(n);
+		mutex_unlock(&n->dev.mutex);
+		return r;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static long vhost_net_compat_ioctl(struct file *f, unsigned int ioctl,
+				   unsigned long arg)
+{
+	return vhost_net_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+static const struct file_operations vhost_net_fops = {
+	.owner          = THIS_MODULE,
+	.release        = vhost_net_release,
+	.unlocked_ioctl = vhost_net_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = vhost_net_compat_ioctl,
+#endif
+	.open           = vhost_net_open,
+	.llseek		= noop_llseek,
+};
+
+static struct miscdevice vhost_net_misc = {
+	.minor = VHOST_NET_MINOR,
+	.name = "vhost-net",
+	.fops = &vhost_net_fops,
+};
+
+static int vhost_net_init(void)
+{
+	if (experimental_zcopytx)
+		vhost_net_enable_zcopy(VHOST_NET_VQ_TX);
+	return misc_register(&vhost_net_misc);
+}
+module_init(vhost_net_init);
+
+static void vhost_net_exit(void)
+{
+	misc_deregister(&vhost_net_misc);
+}
+module_exit(vhost_net_exit);
+
+MODULE_VERSION("0.0.1");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Michael S. Tsirkin");
+MODULE_DESCRIPTION("Host kernel accelerator for virtio net");
+MODULE_ALIAS_MISCDEV(VHOST_NET_MINOR);
+MODULE_ALIAS("devname:vhost-net");
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
new file mode 100644
index 000000000..ea32b3867
--- /dev/null
+++ b/drivers/vhost/scsi.c
@@ -0,0 +1,2422 @@
+/*******************************************************************************
+ * Vhost kernel TCM fabric driver for virtio SCSI initiators
+ *
+ * (C) Copyright 2010-2013 Datera, Inc.
+ * (C) Copyright 2010-2012 IBM Corp.
+ *
+ * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
+ *
+ * Authors: Nicholas A. Bellinger <nab@daterainc.com>
+ *          Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <generated/utsrelease.h>
+#include <linux/utsname.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/kthread.h>
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/configfs.h>
+#include <linux/ctype.h>
+#include <linux/compat.h>
+#include <linux/eventfd.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <asm/unaligned.h>
+#include <scsi/scsi.h>
+#include <target/target_core_base.h>
+#include <target/target_core_fabric.h>
+#include <target/target_core_fabric_configfs.h>
+#include <target/target_core_configfs.h>
+#include <target/configfs_macros.h>
+#include <linux/vhost.h>
+#include <linux/virtio_scsi.h>
+#include <linux/llist.h>
+#include <linux/bitmap.h>
+#include <linux/percpu_ida.h>
+
+#include "vhost.h"
+
+#define VHOST_SCSI_VERSION  "v0.1"
+#define VHOST_SCSI_NAMELEN 256
+#define VHOST_SCSI_MAX_CDB_SIZE 32
+#define VHOST_SCSI_DEFAULT_TAGS 256
+#define VHOST_SCSI_PREALLOC_SGLS 2048
+#define VHOST_SCSI_PREALLOC_UPAGES 2048
+#define VHOST_SCSI_PREALLOC_PROT_SGLS 512
+
+struct vhost_scsi_inflight {
+	/* Wait for the flush operation to finish */
+	struct completion comp;
+	/* Refcount for the inflight reqs */
+	struct kref kref;
+};
+
+struct vhost_scsi_cmd {
+	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
+	int tvc_vq_desc;
+	/* virtio-scsi initiator task attribute */
+	int tvc_task_attr;
+	/* virtio-scsi response incoming iovecs */
+	int tvc_in_iovs;
+	/* virtio-scsi initiator data direction */
+	enum dma_data_direction tvc_data_direction;
+	/* Expected data transfer length from virtio-scsi header */
+	u32 tvc_exp_data_len;
+	/* The Tag from include/linux/virtio_scsi.h:struct virtio_scsi_cmd_req */
+	u64 tvc_tag;
+	/* The number of scatterlists associated with this cmd */
+	u32 tvc_sgl_count;
+	u32 tvc_prot_sgl_count;
+	/* Saved unpacked SCSI LUN for vhost_scsi_submission_work() */
+	u32 tvc_lun;
+	/* Pointer to the SGL formatted memory from virtio-scsi */
+	struct scatterlist *tvc_sgl;
+	struct scatterlist *tvc_prot_sgl;
+	struct page **tvc_upages;
+	/* Pointer to response header iovec */
+	struct iovec *tvc_resp_iov;
+	/* Pointer to vhost_scsi for our device */
+	struct vhost_scsi *tvc_vhost;
+	/* Pointer to vhost_virtqueue for the cmd */
+	struct vhost_virtqueue *tvc_vq;
+	/* Pointer to vhost nexus memory */
+	struct vhost_scsi_nexus *tvc_nexus;
+	/* The TCM I/O descriptor that is accessed via container_of() */
+	struct se_cmd tvc_se_cmd;
+	/* work item used for cmwq dispatch to vhost_scsi_submission_work() */
+	struct work_struct work;
+	/* Copy of the incoming SCSI command descriptor block (CDB) */
+	unsigned char tvc_cdb[VHOST_SCSI_MAX_CDB_SIZE];
+	/* Sense buffer that will be mapped into outgoing status */
+	unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
+	/* Completed commands list, serviced from vhost worker thread */
+	struct llist_node tvc_completion_list;
+	/* Used to track inflight cmd */
+	struct vhost_scsi_inflight *inflight;
+};
+
+struct vhost_scsi_nexus {
+	/* Pointer to TCM session for I_T Nexus */
+	struct se_session *tvn_se_sess;
+};
+
+struct vhost_scsi_nacl {
+	/* Binary World Wide unique Port Name for Vhost Initiator port */
+	u64 iport_wwpn;
+	/* ASCII formatted WWPN for Sas Initiator port */
+	char iport_name[VHOST_SCSI_NAMELEN];
+	/* Returned by vhost_scsi_make_nodeacl() */
+	struct se_node_acl se_node_acl;
+};
+
+struct vhost_scsi_tpg {
+	/* Vhost port target portal group tag for TCM */
+	u16 tport_tpgt;
+	/* Used to track number of TPG Port/Lun Links wrt to explict I_T Nexus shutdown */
+	int tv_tpg_port_count;
+	/* Used for vhost_scsi device reference to tpg_nexus, protected by tv_tpg_mutex */
+	int tv_tpg_vhost_count;
+	/* Used for enabling T10-PI with legacy devices */
+	int tv_fabric_prot_type;
+	/* list for vhost_scsi_list */
+	struct list_head tv_tpg_list;
+	/* Used to protect access for tpg_nexus */
+	struct mutex tv_tpg_mutex;
+	/* Pointer to the TCM VHost I_T Nexus for this TPG endpoint */
+	struct vhost_scsi_nexus *tpg_nexus;
+	/* Pointer back to vhost_scsi_tport */
+	struct vhost_scsi_tport *tport;
+	/* Returned by vhost_scsi_make_tpg() */
+	struct se_portal_group se_tpg;
+	/* Pointer back to vhost_scsi, protected by tv_tpg_mutex */
+	struct vhost_scsi *vhost_scsi;
+};
+
+struct vhost_scsi_tport {
+	/* SCSI protocol the tport is providing */
+	u8 tport_proto_id;
+	/* Binary World Wide unique Port Name for Vhost Target port */
+	u64 tport_wwpn;
+	/* ASCII formatted WWPN for Vhost Target port */
+	char tport_name[VHOST_SCSI_NAMELEN];
+	/* Returned by vhost_scsi_make_tport() */
+	struct se_wwn tport_wwn;
+};
+
+struct vhost_scsi_evt {
+	/* event to be sent to guest */
+	struct virtio_scsi_event event;
+	/* event list, serviced from vhost worker thread */
+	struct llist_node list;
+};
+
+enum {
+	VHOST_SCSI_VQ_CTL = 0,
+	VHOST_SCSI_VQ_EVT = 1,
+	VHOST_SCSI_VQ_IO = 2,
+};
+
+/* Note: can't set VIRTIO_F_VERSION_1 yet, since that implies ANY_LAYOUT. */
+enum {
+	VHOST_SCSI_FEATURES = VHOST_FEATURES | (1ULL << VIRTIO_SCSI_F_HOTPLUG) |
+					       (1ULL << VIRTIO_SCSI_F_T10_PI) |
+					       (1ULL << VIRTIO_F_ANY_LAYOUT) |
+					       (1ULL << VIRTIO_F_VERSION_1)
+};
+
+#define VHOST_SCSI_MAX_TARGET	256
+#define VHOST_SCSI_MAX_VQ	128
+#define VHOST_SCSI_MAX_EVENT	128
+
+struct vhost_scsi_virtqueue {
+	struct vhost_virtqueue vq;
+	/*
+	 * Reference counting for inflight reqs, used for flush operation. At
+	 * each time, one reference tracks new commands submitted, while we
+	 * wait for another one to reach 0.
+	 */
+	struct vhost_scsi_inflight inflights[2];
+	/*
+	 * Indicate current inflight in use, protected by vq->mutex.
+	 * Writers must also take dev mutex and flush under it.
+	 */
+	int inflight_idx;
+};
+
+struct vhost_scsi {
+	/* Protected by vhost_scsi->dev.mutex */
+	struct vhost_scsi_tpg **vs_tpg;
+	char vs_vhost_wwpn[TRANSPORT_IQN_LEN];
+
+	struct vhost_dev dev;
+	struct vhost_scsi_virtqueue vqs[VHOST_SCSI_MAX_VQ];
+
+	struct vhost_work vs_completion_work; /* cmd completion work item */
+	struct llist_head vs_completion_list; /* cmd completion queue */
+
+	struct vhost_work vs_event_work; /* evt injection work item */
+	struct llist_head vs_event_list; /* evt injection queue */
+
+	bool vs_events_missed; /* any missed events, protected by vq->mutex */
+	int vs_events_nr; /* num of pending events, protected by vq->mutex */
+};
+
+static struct target_core_fabric_ops vhost_scsi_ops;
+static struct workqueue_struct *vhost_scsi_workqueue;
+
+/* Global spinlock to protect vhost_scsi TPG list for vhost IOCTL access */
+static DEFINE_MUTEX(vhost_scsi_mutex);
+static LIST_HEAD(vhost_scsi_list);
+
+static int iov_num_pages(void __user *iov_base, size_t iov_len)
+{
+	return (PAGE_ALIGN((unsigned long)iov_base + iov_len) -
+	       ((unsigned long)iov_base & PAGE_MASK)) >> PAGE_SHIFT;
+}
+
+static void vhost_scsi_done_inflight(struct kref *kref)
+{
+	struct vhost_scsi_inflight *inflight;
+
+	inflight = container_of(kref, struct vhost_scsi_inflight, kref);
+	complete(&inflight->comp);
+}
+
+static void vhost_scsi_init_inflight(struct vhost_scsi *vs,
+				    struct vhost_scsi_inflight *old_inflight[])
+{
+	struct vhost_scsi_inflight *new_inflight;
+	struct vhost_virtqueue *vq;
+	int idx, i;
+
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
+		vq = &vs->vqs[i].vq;
+
+		mutex_lock(&vq->mutex);
+
+		/* store old infight */
+		idx = vs->vqs[i].inflight_idx;
+		if (old_inflight)
+			old_inflight[i] = &vs->vqs[i].inflights[idx];
+
+		/* setup new infight */
+		vs->vqs[i].inflight_idx = idx ^ 1;
+		new_inflight = &vs->vqs[i].inflights[idx ^ 1];
+		kref_init(&new_inflight->kref);
+		init_completion(&new_inflight->comp);
+
+		mutex_unlock(&vq->mutex);
+	}
+}
+
+static struct vhost_scsi_inflight *
+vhost_scsi_get_inflight(struct vhost_virtqueue *vq)
+{
+	struct vhost_scsi_inflight *inflight;
+	struct vhost_scsi_virtqueue *svq;
+
+	svq = container_of(vq, struct vhost_scsi_virtqueue, vq);
+	inflight = &svq->inflights[svq->inflight_idx];
+	kref_get(&inflight->kref);
+
+	return inflight;
+}
+
+static void vhost_scsi_put_inflight(struct vhost_scsi_inflight *inflight)
+{
+	kref_put(&inflight->kref, vhost_scsi_done_inflight);
+}
+
+static int vhost_scsi_check_true(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static int vhost_scsi_check_false(struct se_portal_group *se_tpg)
+{
+	return 0;
+}
+
+static char *vhost_scsi_get_fabric_name(void)
+{
+	return "vhost";
+}
+
+static u8 vhost_scsi_get_fabric_proto_ident(struct se_portal_group *se_tpg)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	struct vhost_scsi_tport *tport = tpg->tport;
+
+	switch (tport->tport_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_get_fabric_proto_ident(se_tpg);
+	case SCSI_PROTOCOL_FCP:
+		return fc_get_fabric_proto_ident(se_tpg);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_get_fabric_proto_ident(se_tpg);
+	default:
+		pr_err("Unknown tport_proto_id: 0x%02x, using"
+			" SAS emulation\n", tport->tport_proto_id);
+		break;
+	}
+
+	return sas_get_fabric_proto_ident(se_tpg);
+}
+
+static char *vhost_scsi_get_fabric_wwn(struct se_portal_group *se_tpg)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	struct vhost_scsi_tport *tport = tpg->tport;
+
+	return &tport->tport_name[0];
+}
+
+static u16 vhost_scsi_get_tpgt(struct se_portal_group *se_tpg)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	return tpg->tport_tpgt;
+}
+
+static u32 vhost_scsi_get_default_depth(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static u32
+vhost_scsi_get_pr_transport_id(struct se_portal_group *se_tpg,
+			      struct se_node_acl *se_nacl,
+			      struct t10_pr_registration *pr_reg,
+			      int *format_code,
+			      unsigned char *buf)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	struct vhost_scsi_tport *tport = tpg->tport;
+
+	switch (tport->tport_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+					format_code, buf);
+	case SCSI_PROTOCOL_FCP:
+		return fc_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+					format_code, buf);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+					format_code, buf);
+	default:
+		pr_err("Unknown tport_proto_id: 0x%02x, using"
+			" SAS emulation\n", tport->tport_proto_id);
+		break;
+	}
+
+	return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+			format_code, buf);
+}
+
+static u32
+vhost_scsi_get_pr_transport_id_len(struct se_portal_group *se_tpg,
+				  struct se_node_acl *se_nacl,
+				  struct t10_pr_registration *pr_reg,
+				  int *format_code)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	struct vhost_scsi_tport *tport = tpg->tport;
+
+	switch (tport->tport_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+					format_code);
+	case SCSI_PROTOCOL_FCP:
+		return fc_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+					format_code);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+					format_code);
+	default:
+		pr_err("Unknown tport_proto_id: 0x%02x, using"
+			" SAS emulation\n", tport->tport_proto_id);
+		break;
+	}
+
+	return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+			format_code);
+}
+
+static char *
+vhost_scsi_parse_pr_out_transport_id(struct se_portal_group *se_tpg,
+				    const char *buf,
+				    u32 *out_tid_len,
+				    char **port_nexus_ptr)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	struct vhost_scsi_tport *tport = tpg->tport;
+
+	switch (tport->tport_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+					port_nexus_ptr);
+	case SCSI_PROTOCOL_FCP:
+		return fc_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+					port_nexus_ptr);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+					port_nexus_ptr);
+	default:
+		pr_err("Unknown tport_proto_id: 0x%02x, using"
+			" SAS emulation\n", tport->tport_proto_id);
+		break;
+	}
+
+	return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+			port_nexus_ptr);
+}
+
+static int vhost_scsi_check_prot_fabric_only(struct se_portal_group *se_tpg)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+
+	return tpg->tv_fabric_prot_type;
+}
+
+static struct se_node_acl *
+vhost_scsi_alloc_fabric_acl(struct se_portal_group *se_tpg)
+{
+	struct vhost_scsi_nacl *nacl;
+
+	nacl = kzalloc(sizeof(struct vhost_scsi_nacl), GFP_KERNEL);
+	if (!nacl) {
+		pr_err("Unable to allocate struct vhost_scsi_nacl\n");
+		return NULL;
+	}
+
+	return &nacl->se_node_acl;
+}
+
+static void
+vhost_scsi_release_fabric_acl(struct se_portal_group *se_tpg,
+			     struct se_node_acl *se_nacl)
+{
+	struct vhost_scsi_nacl *nacl = container_of(se_nacl,
+			struct vhost_scsi_nacl, se_node_acl);
+	kfree(nacl);
+}
+
+static u32 vhost_scsi_tpg_get_inst_index(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)
+{
+	struct vhost_scsi_cmd *tv_cmd = container_of(se_cmd,
+				struct vhost_scsi_cmd, tvc_se_cmd);
+	struct se_session *se_sess = tv_cmd->tvc_nexus->tvn_se_sess;
+	int i;
+
+	if (tv_cmd->tvc_sgl_count) {
+		for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
+			put_page(sg_page(&tv_cmd->tvc_sgl[i]));
+	}
+	if (tv_cmd->tvc_prot_sgl_count) {
+		for (i = 0; i < tv_cmd->tvc_prot_sgl_count; i++)
+			put_page(sg_page(&tv_cmd->tvc_prot_sgl[i]));
+	}
+
+	vhost_scsi_put_inflight(tv_cmd->inflight);
+	percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
+}
+
+static int vhost_scsi_shutdown_session(struct se_session *se_sess)
+{
+	return 0;
+}
+
+static void vhost_scsi_close_session(struct se_session *se_sess)
+{
+	return;
+}
+
+static u32 vhost_scsi_sess_get_index(struct se_session *se_sess)
+{
+	return 0;
+}
+
+static int vhost_scsi_write_pending(struct se_cmd *se_cmd)
+{
+	/* Go ahead and process the write immediately */
+	target_execute_cmd(se_cmd);
+	return 0;
+}
+
+static int vhost_scsi_write_pending_status(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static void vhost_scsi_set_default_node_attrs(struct se_node_acl *nacl)
+{
+	return;
+}
+
+static u32 vhost_scsi_get_task_tag(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static int vhost_scsi_get_cmd_state(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static void vhost_scsi_complete_cmd(struct vhost_scsi_cmd *cmd)
+{
+	struct vhost_scsi *vs = cmd->tvc_vhost;
+
+	llist_add(&cmd->tvc_completion_list, &vs->vs_completion_list);
+
+	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
+}
+
+static int vhost_scsi_queue_data_in(struct se_cmd *se_cmd)
+{
+	struct vhost_scsi_cmd *cmd = container_of(se_cmd,
+				struct vhost_scsi_cmd, tvc_se_cmd);
+	vhost_scsi_complete_cmd(cmd);
+	return 0;
+}
+
+static int vhost_scsi_queue_status(struct se_cmd *se_cmd)
+{
+	struct vhost_scsi_cmd *cmd = container_of(se_cmd,
+				struct vhost_scsi_cmd, tvc_se_cmd);
+	vhost_scsi_complete_cmd(cmd);
+	return 0;
+}
+
+static void vhost_scsi_queue_tm_rsp(struct se_cmd *se_cmd)
+{
+	return;
+}
+
+static void vhost_scsi_aborted_task(struct se_cmd *se_cmd)
+{
+	return;
+}
+
+static void vhost_scsi_free_evt(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
+{
+	vs->vs_events_nr--;
+	kfree(evt);
+}
+
+static struct vhost_scsi_evt *
+vhost_scsi_allocate_evt(struct vhost_scsi *vs,
+		       u32 event, u32 reason)
+{
+	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
+	struct vhost_scsi_evt *evt;
+
+	if (vs->vs_events_nr > VHOST_SCSI_MAX_EVENT) {
+		vs->vs_events_missed = true;
+		return NULL;
+	}
+
+	evt = kzalloc(sizeof(*evt), GFP_KERNEL);
+	if (!evt) {
+		vq_err(vq, "Failed to allocate vhost_scsi_evt\n");
+		vs->vs_events_missed = true;
+		return NULL;
+	}
+
+	evt->event.event = cpu_to_vhost32(vq, event);
+	evt->event.reason = cpu_to_vhost32(vq, reason);
+	vs->vs_events_nr++;
+
+	return evt;
+}
+
+static void vhost_scsi_free_cmd(struct vhost_scsi_cmd *cmd)
+{
+	struct se_cmd *se_cmd = &cmd->tvc_se_cmd;
+
+	/* TODO locking against target/backend threads? */
+	transport_generic_free_cmd(se_cmd, 0);
+
+}
+
+static int vhost_scsi_check_stop_free(struct se_cmd *se_cmd)
+{
+	return target_put_sess_cmd(se_cmd->se_sess, se_cmd);
+}
+
+static void
+vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
+{
+	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
+	struct virtio_scsi_event *event = &evt->event;
+	struct virtio_scsi_event __user *eventp;
+	unsigned out, in;
+	int head, ret;
+
+	if (!vq->private_data) {
+		vs->vs_events_missed = true;
+		return;
+	}
+
+again:
+	vhost_disable_notify(&vs->dev, vq);
+	head = vhost_get_vq_desc(vq, vq->iov,
+			ARRAY_SIZE(vq->iov), &out, &in,
+			NULL, NULL);
+	if (head < 0) {
+		vs->vs_events_missed = true;
+		return;
+	}
+	if (head == vq->num) {
+		if (vhost_enable_notify(&vs->dev, vq))
+			goto again;
+		vs->vs_events_missed = true;
+		return;
+	}
+
+	if ((vq->iov[out].iov_len != sizeof(struct virtio_scsi_event))) {
+		vq_err(vq, "Expecting virtio_scsi_event, got %zu bytes\n",
+				vq->iov[out].iov_len);
+		vs->vs_events_missed = true;
+		return;
+	}
+
+	if (vs->vs_events_missed) {
+		event->event |= cpu_to_vhost32(vq, VIRTIO_SCSI_T_EVENTS_MISSED);
+		vs->vs_events_missed = false;
+	}
+
+	eventp = vq->iov[out].iov_base;
+	ret = __copy_to_user(eventp, event, sizeof(*event));
+	if (!ret)
+		vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+	else
+		vq_err(vq, "Faulted on vhost_scsi_send_event\n");
+}
+
+static void vhost_scsi_evt_work(struct vhost_work *work)
+{
+	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
+					vs_event_work);
+	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
+	struct vhost_scsi_evt *evt;
+	struct llist_node *llnode;
+
+	mutex_lock(&vq->mutex);
+	llnode = llist_del_all(&vs->vs_event_list);
+	while (llnode) {
+		evt = llist_entry(llnode, struct vhost_scsi_evt, list);
+		llnode = llist_next(llnode);
+		vhost_scsi_do_evt_work(vs, evt);
+		vhost_scsi_free_evt(vs, evt);
+	}
+	mutex_unlock(&vq->mutex);
+}
+
+/* Fill in status and signal that we are done processing this command
+ *
+ * This is scheduled in the vhost work queue so we are called with the owner
+ * process mm and can access the vring.
+ */
+static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
+{
+	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
+					vs_completion_work);
+	DECLARE_BITMAP(signal, VHOST_SCSI_MAX_VQ);
+	struct virtio_scsi_cmd_resp v_rsp;
+	struct vhost_scsi_cmd *cmd;
+	struct llist_node *llnode;
+	struct se_cmd *se_cmd;
+	struct iov_iter iov_iter;
+	int ret, vq;
+
+	bitmap_zero(signal, VHOST_SCSI_MAX_VQ);
+	llnode = llist_del_all(&vs->vs_completion_list);
+	while (llnode) {
+		cmd = llist_entry(llnode, struct vhost_scsi_cmd,
+				     tvc_completion_list);
+		llnode = llist_next(llnode);
+		se_cmd = &cmd->tvc_se_cmd;
+
+		pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
+			cmd, se_cmd->residual_count, se_cmd->scsi_status);
+
+		memset(&v_rsp, 0, sizeof(v_rsp));
+		v_rsp.resid = cpu_to_vhost32(cmd->tvc_vq, se_cmd->residual_count);
+		/* TODO is status_qualifier field needed? */
+		v_rsp.status = se_cmd->scsi_status;
+		v_rsp.sense_len = cpu_to_vhost32(cmd->tvc_vq,
+						 se_cmd->scsi_sense_length);
+		memcpy(v_rsp.sense, cmd->tvc_sense_buf,
+		       se_cmd->scsi_sense_length);
+
+		iov_iter_init(&iov_iter, READ, cmd->tvc_resp_iov,
+			      cmd->tvc_in_iovs, sizeof(v_rsp));
+		ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
+		if (likely(ret == sizeof(v_rsp))) {
+			struct vhost_scsi_virtqueue *q;
+			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
+			q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);
+			vq = q - vs->vqs;
+			__set_bit(vq, signal);
+		} else
+			pr_err("Faulted on virtio_scsi_cmd_resp\n");
+
+		vhost_scsi_free_cmd(cmd);
+	}
+
+	vq = -1;
+	while ((vq = find_next_bit(signal, VHOST_SCSI_MAX_VQ, vq + 1))
+		< VHOST_SCSI_MAX_VQ)
+		vhost_signal(&vs->dev, &vs->vqs[vq].vq);
+}
+
+static struct vhost_scsi_cmd *
+vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,
+		   unsigned char *cdb, u64 scsi_tag, u16 lun, u8 task_attr,
+		   u32 exp_data_len, int data_direction)
+{
+	struct vhost_scsi_cmd *cmd;
+	struct vhost_scsi_nexus *tv_nexus;
+	struct se_session *se_sess;
+	struct scatterlist *sg, *prot_sg;
+	struct page **pages;
+	int tag;
+
+	tv_nexus = tpg->tpg_nexus;
+	if (!tv_nexus) {
+		pr_err("Unable to locate active struct vhost_scsi_nexus\n");
+		return ERR_PTR(-EIO);
+	}
+	se_sess = tv_nexus->tvn_se_sess;
+
+	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, TASK_RUNNING);
+	if (tag < 0) {
+		pr_err("Unable to obtain tag for vhost_scsi_cmd\n");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	cmd = &((struct vhost_scsi_cmd *)se_sess->sess_cmd_map)[tag];
+	sg = cmd->tvc_sgl;
+	prot_sg = cmd->tvc_prot_sgl;
+	pages = cmd->tvc_upages;
+	memset(cmd, 0, sizeof(struct vhost_scsi_cmd));
+
+	cmd->tvc_sgl = sg;
+	cmd->tvc_prot_sgl = prot_sg;
+	cmd->tvc_upages = pages;
+	cmd->tvc_se_cmd.map_tag = tag;
+	cmd->tvc_tag = scsi_tag;
+	cmd->tvc_lun = lun;
+	cmd->tvc_task_attr = task_attr;
+	cmd->tvc_exp_data_len = exp_data_len;
+	cmd->tvc_data_direction = data_direction;
+	cmd->tvc_nexus = tv_nexus;
+	cmd->inflight = vhost_scsi_get_inflight(vq);
+
+	memcpy(cmd->tvc_cdb, cdb, VHOST_SCSI_MAX_CDB_SIZE);
+
+	return cmd;
+}
+
+/*
+ * Map a user memory range into a scatterlist
+ *
+ * Returns the number of scatterlist entries used or -errno on error.
+ */
+static int
+vhost_scsi_map_to_sgl(struct vhost_scsi_cmd *cmd,
+		      void __user *ptr,
+		      size_t len,
+		      struct scatterlist *sgl,
+		      bool write)
+{
+	unsigned int npages = 0, offset, nbytes;
+	unsigned int pages_nr = iov_num_pages(ptr, len);
+	struct scatterlist *sg = sgl;
+	struct page **pages = cmd->tvc_upages;
+	int ret, i;
+
+	if (pages_nr > VHOST_SCSI_PREALLOC_UPAGES) {
+		pr_err("vhost_scsi_map_to_sgl() pages_nr: %u greater than"
+		       " preallocated VHOST_SCSI_PREALLOC_UPAGES: %u\n",
+			pages_nr, VHOST_SCSI_PREALLOC_UPAGES);
+		return -ENOBUFS;
+	}
+
+	ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages);
+	/* No pages were pinned */
+	if (ret < 0)
+		goto out;
+	/* Less pages pinned than wanted */
+	if (ret != pages_nr) {
+		for (i = 0; i < ret; i++)
+			put_page(pages[i]);
+		ret = -EFAULT;
+		goto out;
+	}
+
+	while (len > 0) {
+		offset = (uintptr_t)ptr & ~PAGE_MASK;
+		nbytes = min_t(unsigned int, PAGE_SIZE - offset, len);
+		sg_set_page(sg, pages[npages], nbytes, offset);
+		ptr += nbytes;
+		len -= nbytes;
+		sg++;
+		npages++;
+	}
+
+out:
+	return ret;
+}
+
+static int
+vhost_scsi_calc_sgls(struct iov_iter *iter, size_t bytes, int max_sgls)
+{
+	int sgl_count = 0;
+
+	if (!iter || !iter->iov) {
+		pr_err("%s: iter->iov is NULL, but expected bytes: %zu"
+		       " present\n", __func__, bytes);
+		return -EINVAL;
+	}
+
+	sgl_count = iov_iter_npages(iter, 0xffff);
+	if (sgl_count > max_sgls) {
+		pr_err("%s: requested sgl_count: %d exceeds pre-allocated"
+		       " max_sgls: %d\n", __func__, sgl_count, max_sgls);
+		return -EINVAL;
+	}
+	return sgl_count;
+}
+
+static int
+vhost_scsi_iov_to_sgl(struct vhost_scsi_cmd *cmd, bool write,
+		      struct iov_iter *iter,
+		      struct scatterlist *sg, int sg_count)
+{
+	size_t off = iter->iov_offset;
+	int i, ret;
+
+	for (i = 0; i < iter->nr_segs; i++) {
+		void __user *base = iter->iov[i].iov_base + off;
+		size_t len = iter->iov[i].iov_len - off;
+
+		ret = vhost_scsi_map_to_sgl(cmd, base, len, sg, write);
+		if (ret < 0) {
+			for (i = 0; i < sg_count; i++) {
+				struct page *page = sg_page(&sg[i]);
+				if (page)
+					put_page(page);
+			}
+			return ret;
+		}
+		sg += ret;
+		off = 0;
+	}
+	return 0;
+}
+
+static int
+vhost_scsi_mapal(struct vhost_scsi_cmd *cmd,
+		 size_t prot_bytes, struct iov_iter *prot_iter,
+		 size_t data_bytes, struct iov_iter *data_iter)
+{
+	int sgl_count, ret;
+	bool write = (cmd->tvc_data_direction == DMA_FROM_DEVICE);
+
+	if (prot_bytes) {
+		sgl_count = vhost_scsi_calc_sgls(prot_iter, prot_bytes,
+						 VHOST_SCSI_PREALLOC_PROT_SGLS);
+		if (sgl_count < 0)
+			return sgl_count;
+
+		sg_init_table(cmd->tvc_prot_sgl, sgl_count);
+		cmd->tvc_prot_sgl_count = sgl_count;
+		pr_debug("%s prot_sg %p prot_sgl_count %u\n", __func__,
+			 cmd->tvc_prot_sgl, cmd->tvc_prot_sgl_count);
+
+		ret = vhost_scsi_iov_to_sgl(cmd, write, prot_iter,
+					    cmd->tvc_prot_sgl,
+					    cmd->tvc_prot_sgl_count);
+		if (ret < 0) {
+			cmd->tvc_prot_sgl_count = 0;
+			return ret;
+		}
+	}
+	sgl_count = vhost_scsi_calc_sgls(data_iter, data_bytes,
+					 VHOST_SCSI_PREALLOC_SGLS);
+	if (sgl_count < 0)
+		return sgl_count;
+
+	sg_init_table(cmd->tvc_sgl, sgl_count);
+	cmd->tvc_sgl_count = sgl_count;
+	pr_debug("%s data_sg %p data_sgl_count %u\n", __func__,
+		  cmd->tvc_sgl, cmd->tvc_sgl_count);
+
+	ret = vhost_scsi_iov_to_sgl(cmd, write, data_iter,
+				    cmd->tvc_sgl, cmd->tvc_sgl_count);
+	if (ret < 0) {
+		cmd->tvc_sgl_count = 0;
+		return ret;
+	}
+	return 0;
+}
+
+static int vhost_scsi_to_tcm_attr(int attr)
+{
+	switch (attr) {
+	case VIRTIO_SCSI_S_SIMPLE:
+		return TCM_SIMPLE_TAG;
+	case VIRTIO_SCSI_S_ORDERED:
+		return TCM_ORDERED_TAG;
+	case VIRTIO_SCSI_S_HEAD:
+		return TCM_HEAD_TAG;
+	case VIRTIO_SCSI_S_ACA:
+		return TCM_ACA_TAG;
+	default:
+		break;
+	}
+	return TCM_SIMPLE_TAG;
+}
+
+static void vhost_scsi_submission_work(struct work_struct *work)
+{
+	struct vhost_scsi_cmd *cmd =
+		container_of(work, struct vhost_scsi_cmd, work);
+	struct vhost_scsi_nexus *tv_nexus;
+	struct se_cmd *se_cmd = &cmd->tvc_se_cmd;
+	struct scatterlist *sg_ptr, *sg_prot_ptr = NULL;
+	int rc;
+
+	/* FIXME: BIDI operation */
+	if (cmd->tvc_sgl_count) {
+		sg_ptr = cmd->tvc_sgl;
+
+		if (cmd->tvc_prot_sgl_count)
+			sg_prot_ptr = cmd->tvc_prot_sgl;
+		else
+			se_cmd->prot_pto = true;
+	} else {
+		sg_ptr = NULL;
+	}
+	tv_nexus = cmd->tvc_nexus;
+
+	rc = target_submit_cmd_map_sgls(se_cmd, tv_nexus->tvn_se_sess,
+			cmd->tvc_cdb, &cmd->tvc_sense_buf[0],
+			cmd->tvc_lun, cmd->tvc_exp_data_len,
+			vhost_scsi_to_tcm_attr(cmd->tvc_task_attr),
+			cmd->tvc_data_direction, TARGET_SCF_ACK_KREF,
+			sg_ptr, cmd->tvc_sgl_count, NULL, 0, sg_prot_ptr,
+			cmd->tvc_prot_sgl_count);
+	if (rc < 0) {
+		transport_send_check_condition_and_sense(se_cmd,
+				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);
+		transport_generic_free_cmd(se_cmd, 0);
+	}
+}
+
+static void
+vhost_scsi_send_bad_target(struct vhost_scsi *vs,
+			   struct vhost_virtqueue *vq,
+			   int head, unsigned out)
+{
+	struct virtio_scsi_cmd_resp __user *resp;
+	struct virtio_scsi_cmd_resp rsp;
+	int ret;
+
+	memset(&rsp, 0, sizeof(rsp));
+	rsp.response = VIRTIO_SCSI_S_BAD_TARGET;
+	resp = vq->iov[out].iov_base;
+	ret = __copy_to_user(resp, &rsp, sizeof(rsp));
+	if (!ret)
+		vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+	else
+		pr_err("Faulted on virtio_scsi_cmd_resp\n");
+}
+
+static void
+vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
+{
+	struct vhost_scsi_tpg **vs_tpg, *tpg;
+	struct virtio_scsi_cmd_req v_req;
+	struct virtio_scsi_cmd_req_pi v_req_pi;
+	struct vhost_scsi_cmd *cmd;
+	struct iov_iter out_iter, in_iter, prot_iter, data_iter;
+	u64 tag;
+	u32 exp_data_len, data_direction;
+	unsigned out, in;
+	int head, ret, prot_bytes;
+	size_t req_size, rsp_size = sizeof(struct virtio_scsi_cmd_resp);
+	size_t out_size, in_size;
+	u16 lun;
+	u8 *target, *lunp, task_attr;
+	bool t10_pi = vhost_has_feature(vq, VIRTIO_SCSI_F_T10_PI);
+	void *req, *cdb;
+
+	mutex_lock(&vq->mutex);
+	/*
+	 * We can handle the vq only after the endpoint is setup by calling the
+	 * VHOST_SCSI_SET_ENDPOINT ioctl.
+	 */
+	vs_tpg = vq->private_data;
+	if (!vs_tpg)
+		goto out;
+
+	vhost_disable_notify(&vs->dev, vq);
+
+	for (;;) {
+		head = vhost_get_vq_desc(vq, vq->iov,
+					 ARRAY_SIZE(vq->iov), &out, &in,
+					 NULL, NULL);
+		pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
+			 head, out, in);
+		/* On error, stop handling until the next kick. */
+		if (unlikely(head < 0))
+			break;
+		/* Nothing new?  Wait for eventfd to tell us they refilled. */
+		if (head == vq->num) {
+			if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
+				vhost_disable_notify(&vs->dev, vq);
+				continue;
+			}
+			break;
+		}
+		/*
+		 * Check for a sane response buffer so we can report early
+		 * errors back to the guest.
+		 */
+		if (unlikely(vq->iov[out].iov_len < rsp_size)) {
+			vq_err(vq, "Expecting at least virtio_scsi_cmd_resp"
+				" size, got %zu bytes\n", vq->iov[out].iov_len);
+			break;
+		}
+		/*
+		 * Setup pointers and values based upon different virtio-scsi
+		 * request header if T10_PI is enabled in KVM guest.
+		 */
+		if (t10_pi) {
+			req = &v_req_pi;
+			req_size = sizeof(v_req_pi);
+			lunp = &v_req_pi.lun[0];
+			target = &v_req_pi.lun[1];
+		} else {
+			req = &v_req;
+			req_size = sizeof(v_req);
+			lunp = &v_req.lun[0];
+			target = &v_req.lun[1];
+		}
+		/*
+		 * FIXME: Not correct for BIDI operation
+		 */
+		out_size = iov_length(vq->iov, out);
+		in_size = iov_length(&vq->iov[out], in);
+
+		/*
+		 * Copy over the virtio-scsi request header, which for a
+		 * ANY_LAYOUT enabled guest may span multiple iovecs, or a
+		 * single iovec may contain both the header + outgoing
+		 * WRITE payloads.
+		 *
+		 * copy_from_iter() will advance out_iter, so that it will
+		 * point at the start of the outgoing WRITE payload, if
+		 * DMA_TO_DEVICE is set.
+		 */
+		iov_iter_init(&out_iter, WRITE, vq->iov, out, out_size);
+
+		ret = copy_from_iter(req, req_size, &out_iter);
+		if (unlikely(ret != req_size)) {
+			vq_err(vq, "Faulted on copy_from_iter\n");
+			vhost_scsi_send_bad_target(vs, vq, head, out);
+			continue;
+		}
+		/* virtio-scsi spec requires byte 0 of the lun to be 1 */
+		if (unlikely(*lunp != 1)) {
+			vq_err(vq, "Illegal virtio-scsi lun: %u\n", *lunp);
+			vhost_scsi_send_bad_target(vs, vq, head, out);
+			continue;
+		}
+
+		tpg = ACCESS_ONCE(vs_tpg[*target]);
+		if (unlikely(!tpg)) {
+			/* Target does not exist, fail the request */
+			vhost_scsi_send_bad_target(vs, vq, head, out);
+			continue;
+		}
+		/*
+		 * Determine data_direction by calculating the total outgoing
+		 * iovec sizes + incoming iovec sizes vs. virtio-scsi request +
+		 * response headers respectively.
+		 *
+		 * For DMA_TO_DEVICE this is out_iter, which is already pointing
+		 * to the right place.
+		 *
+		 * For DMA_FROM_DEVICE, the iovec will be just past the end
+		 * of the virtio-scsi response header in either the same
+		 * or immediately following iovec.
+		 *
+		 * Any associated T10_PI bytes for the outgoing / incoming
+		 * payloads are included in calculation of exp_data_len here.
+		 */
+		prot_bytes = 0;
+
+		if (out_size > req_size) {
+			data_direction = DMA_TO_DEVICE;
+			exp_data_len = out_size - req_size;
+			data_iter = out_iter;
+		} else if (in_size > rsp_size) {
+			data_direction = DMA_FROM_DEVICE;
+			exp_data_len = in_size - rsp_size;
+
+			iov_iter_init(&in_iter, READ, &vq->iov[out], in,
+				      rsp_size + exp_data_len);
+			iov_iter_advance(&in_iter, rsp_size);
+			data_iter = in_iter;
+		} else {
+			data_direction = DMA_NONE;
+			exp_data_len = 0;
+		}
+		/*
+		 * If T10_PI header + payload is present, setup prot_iter values
+		 * and recalculate data_iter for vhost_scsi_mapal() mapping to
+		 * host scatterlists via get_user_pages_fast().
+		 */
+		if (t10_pi) {
+			if (v_req_pi.pi_bytesout) {
+				if (data_direction != DMA_TO_DEVICE) {
+					vq_err(vq, "Received non zero pi_bytesout,"
+						" but wrong data_direction\n");
+					vhost_scsi_send_bad_target(vs, vq, head, out);
+					continue;
+				}
+				prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesout);
+			} else if (v_req_pi.pi_bytesin) {
+				if (data_direction != DMA_FROM_DEVICE) {
+					vq_err(vq, "Received non zero pi_bytesin,"
+						" but wrong data_direction\n");
+					vhost_scsi_send_bad_target(vs, vq, head, out);
+					continue;
+				}
+				prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesin);
+			}
+			/*
+			 * Set prot_iter to data_iter, and advance past any
+			 * preceeding prot_bytes that may be present.
+			 *
+			 * Also fix up the exp_data_len to reflect only the
+			 * actual data payload length.
+			 */
+			if (prot_bytes) {
+				exp_data_len -= prot_bytes;
+				prot_iter = data_iter;
+				iov_iter_advance(&data_iter, prot_bytes);
+			}
+			tag = vhost64_to_cpu(vq, v_req_pi.tag);
+			task_attr = v_req_pi.task_attr;
+			cdb = &v_req_pi.cdb[0];
+			lun = ((v_req_pi.lun[2] << 8) | v_req_pi.lun[3]) & 0x3FFF;
+		} else {
+			tag = vhost64_to_cpu(vq, v_req.tag);
+			task_attr = v_req.task_attr;
+			cdb = &v_req.cdb[0];
+			lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
+		}
+		/*
+		 * Check that the received CDB size does not exceeded our
+		 * hardcoded max for vhost-scsi, then get a pre-allocated
+		 * cmd descriptor for the new virtio-scsi tag.
+		 *
+		 * TODO what if cdb was too small for varlen cdb header?
+		 */
+		if (unlikely(scsi_command_size(cdb) > VHOST_SCSI_MAX_CDB_SIZE)) {
+			vq_err(vq, "Received SCSI CDB with command_size: %d that"
+				" exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
+				scsi_command_size(cdb), VHOST_SCSI_MAX_CDB_SIZE);
+			vhost_scsi_send_bad_target(vs, vq, head, out);
+			continue;
+		}
+		cmd = vhost_scsi_get_tag(vq, tpg, cdb, tag, lun, task_attr,
+					 exp_data_len + prot_bytes,
+					 data_direction);
+		if (IS_ERR(cmd)) {
+			vq_err(vq, "vhost_scsi_get_tag failed %ld\n",
+			       PTR_ERR(cmd));
+			vhost_scsi_send_bad_target(vs, vq, head, out);
+			continue;
+		}
+		cmd->tvc_vhost = vs;
+		cmd->tvc_vq = vq;
+		cmd->tvc_resp_iov = &vq->iov[out];
+		cmd->tvc_in_iovs = in;
+
+		pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
+			 cmd->tvc_cdb[0], cmd->tvc_lun);
+		pr_debug("cmd: %p exp_data_len: %d, prot_bytes: %d data_direction:"
+			 " %d\n", cmd, exp_data_len, prot_bytes, data_direction);
+
+		if (data_direction != DMA_NONE) {
+			ret = vhost_scsi_mapal(cmd,
+					       prot_bytes, &prot_iter,
+					       exp_data_len, &data_iter);
+			if (unlikely(ret)) {
+				vq_err(vq, "Failed to map iov to sgl\n");
+				vhost_scsi_release_cmd(&cmd->tvc_se_cmd);
+				vhost_scsi_send_bad_target(vs, vq, head, out);
+				continue;
+			}
+		}
+		/*
+		 * Save the descriptor from vhost_get_vq_desc() to be used to
+		 * complete the virtio-scsi request in TCM callback context via
+		 * vhost_scsi_queue_data_in() and vhost_scsi_queue_status()
+		 */
+		cmd->tvc_vq_desc = head;
+		/*
+		 * Dispatch cmd descriptor for cmwq execution in process
+		 * context provided by vhost_scsi_workqueue.  This also ensures
+		 * cmd is executed on the same kworker CPU as this vhost
+		 * thread to gain positive L2 cache locality effects.
+		 */
+		INIT_WORK(&cmd->work, vhost_scsi_submission_work);
+		queue_work(vhost_scsi_workqueue, &cmd->work);
+	}
+out:
+	mutex_unlock(&vq->mutex);
+}
+
+static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
+{
+	pr_debug("%s: The handling func for control queue.\n", __func__);
+}
+
+static void
+vhost_scsi_send_evt(struct vhost_scsi *vs,
+		   struct vhost_scsi_tpg *tpg,
+		   struct se_lun *lun,
+		   u32 event,
+		   u32 reason)
+{
+	struct vhost_scsi_evt *evt;
+
+	evt = vhost_scsi_allocate_evt(vs, event, reason);
+	if (!evt)
+		return;
+
+	if (tpg && lun) {
+		/* TODO: share lun setup code with virtio-scsi.ko */
+		/*
+		 * Note: evt->event is zeroed when we allocate it and
+		 * lun[4-7] need to be zero according to virtio-scsi spec.
+		 */
+		evt->event.lun[0] = 0x01;
+		evt->event.lun[1] = tpg->tport_tpgt;
+		if (lun->unpacked_lun >= 256)
+			evt->event.lun[2] = lun->unpacked_lun >> 8 | 0x40 ;
+		evt->event.lun[3] = lun->unpacked_lun & 0xFF;
+	}
+
+	llist_add(&evt->list, &vs->vs_event_list);
+	vhost_work_queue(&vs->dev, &vs->vs_event_work);
+}
+
+static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						poll.work);
+	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
+
+	mutex_lock(&vq->mutex);
+	if (!vq->private_data)
+		goto out;
+
+	if (vs->vs_events_missed)
+		vhost_scsi_send_evt(vs, NULL, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
+out:
+	mutex_unlock(&vq->mutex);
+}
+
+static void vhost_scsi_handle_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						poll.work);
+	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
+
+	vhost_scsi_handle_vq(vs, vq);
+}
+
+static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
+{
+	vhost_poll_flush(&vs->vqs[index].vq.poll);
+}
+
+/* Callers must hold dev mutex */
+static void vhost_scsi_flush(struct vhost_scsi *vs)
+{
+	struct vhost_scsi_inflight *old_inflight[VHOST_SCSI_MAX_VQ];
+	int i;
+
+	/* Init new inflight and remember the old inflight */
+	vhost_scsi_init_inflight(vs, old_inflight);
+
+	/*
+	 * The inflight->kref was initialized to 1. We decrement it here to
+	 * indicate the start of the flush operation so that it will reach 0
+	 * when all the reqs are finished.
+	 */
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
+		kref_put(&old_inflight[i]->kref, vhost_scsi_done_inflight);
+
+	/* Flush both the vhost poll and vhost work */
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
+		vhost_scsi_flush_vq(vs, i);
+	vhost_work_flush(&vs->dev, &vs->vs_completion_work);
+	vhost_work_flush(&vs->dev, &vs->vs_event_work);
+
+	/* Wait for all reqs issued before the flush to be finished */
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
+		wait_for_completion(&old_inflight[i]->comp);
+}
+
+/*
+ * Called from vhost_scsi_ioctl() context to walk the list of available
+ * vhost_scsi_tpg with an active struct vhost_scsi_nexus
+ *
+ *  The lock nesting rule is:
+ *    vhost_scsi_mutex -> vs->dev.mutex -> tpg->tv_tpg_mutex -> vq->mutex
+ */
+static int
+vhost_scsi_set_endpoint(struct vhost_scsi *vs,
+			struct vhost_scsi_target *t)
+{
+	struct se_portal_group *se_tpg;
+	struct vhost_scsi_tport *tv_tport;
+	struct vhost_scsi_tpg *tpg;
+	struct vhost_scsi_tpg **vs_tpg;
+	struct vhost_virtqueue *vq;
+	int index, ret, i, len;
+	bool match = false;
+
+	mutex_lock(&vhost_scsi_mutex);
+	mutex_lock(&vs->dev.mutex);
+
+	/* Verify that ring has been setup correctly. */
+	for (index = 0; index < vs->dev.nvqs; ++index) {
+		/* Verify that ring has been setup correctly. */
+		if (!vhost_vq_access_ok(&vs->vqs[index].vq)) {
+			ret = -EFAULT;
+			goto out;
+		}
+	}
+
+	len = sizeof(vs_tpg[0]) * VHOST_SCSI_MAX_TARGET;
+	vs_tpg = kzalloc(len, GFP_KERNEL);
+	if (!vs_tpg) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	if (vs->vs_tpg)
+		memcpy(vs_tpg, vs->vs_tpg, len);
+
+	list_for_each_entry(tpg, &vhost_scsi_list, tv_tpg_list) {
+		mutex_lock(&tpg->tv_tpg_mutex);
+		if (!tpg->tpg_nexus) {
+			mutex_unlock(&tpg->tv_tpg_mutex);
+			continue;
+		}
+		if (tpg->tv_tpg_vhost_count != 0) {
+			mutex_unlock(&tpg->tv_tpg_mutex);
+			continue;
+		}
+		tv_tport = tpg->tport;
+
+		if (!strcmp(tv_tport->tport_name, t->vhost_wwpn)) {
+			if (vs->vs_tpg && vs->vs_tpg[tpg->tport_tpgt]) {
+				kfree(vs_tpg);
+				mutex_unlock(&tpg->tv_tpg_mutex);
+				ret = -EEXIST;
+				goto out;
+			}
+			/*
+			 * In order to ensure individual vhost-scsi configfs
+			 * groups cannot be removed while in use by vhost ioctl,
+			 * go ahead and take an explicit se_tpg->tpg_group.cg_item
+			 * dependency now.
+			 */
+			se_tpg = &tpg->se_tpg;
+			ret = target_depend_item(&se_tpg->tpg_group.cg_item);
+			if (ret) {
+				pr_warn("configfs_depend_item() failed: %d\n", ret);
+				kfree(vs_tpg);
+				mutex_unlock(&tpg->tv_tpg_mutex);
+				goto out;
+			}
+			tpg->tv_tpg_vhost_count++;
+			tpg->vhost_scsi = vs;
+			vs_tpg[tpg->tport_tpgt] = tpg;
+			smp_mb__after_atomic();
+			match = true;
+		}
+		mutex_unlock(&tpg->tv_tpg_mutex);
+	}
+
+	if (match) {
+		memcpy(vs->vs_vhost_wwpn, t->vhost_wwpn,
+		       sizeof(vs->vs_vhost_wwpn));
+		for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
+			vq = &vs->vqs[i].vq;
+			mutex_lock(&vq->mutex);
+			vq->private_data = vs_tpg;
+			vhost_init_used(vq);
+			mutex_unlock(&vq->mutex);
+		}
+		ret = 0;
+	} else {
+		ret = -EEXIST;
+	}
+
+	/*
+	 * Act as synchronize_rcu to make sure access to
+	 * old vs->vs_tpg is finished.
+	 */
+	vhost_scsi_flush(vs);
+	kfree(vs->vs_tpg);
+	vs->vs_tpg = vs_tpg;
+
+out:
+	mutex_unlock(&vs->dev.mutex);
+	mutex_unlock(&vhost_scsi_mutex);
+	return ret;
+}
+
+static int
+vhost_scsi_clear_endpoint(struct vhost_scsi *vs,
+			  struct vhost_scsi_target *t)
+{
+	struct se_portal_group *se_tpg;
+	struct vhost_scsi_tport *tv_tport;
+	struct vhost_scsi_tpg *tpg;
+	struct vhost_virtqueue *vq;
+	bool match = false;
+	int index, ret, i;
+	u8 target;
+
+	mutex_lock(&vhost_scsi_mutex);
+	mutex_lock(&vs->dev.mutex);
+	/* Verify that ring has been setup correctly. */
+	for (index = 0; index < vs->dev.nvqs; ++index) {
+		if (!vhost_vq_access_ok(&vs->vqs[index].vq)) {
+			ret = -EFAULT;
+			goto err_dev;
+		}
+	}
+
+	if (!vs->vs_tpg) {
+		ret = 0;
+		goto err_dev;
+	}
+
+	for (i = 0; i < VHOST_SCSI_MAX_TARGET; i++) {
+		target = i;
+		tpg = vs->vs_tpg[target];
+		if (!tpg)
+			continue;
+
+		mutex_lock(&tpg->tv_tpg_mutex);
+		tv_tport = tpg->tport;
+		if (!tv_tport) {
+			ret = -ENODEV;
+			goto err_tpg;
+		}
+
+		if (strcmp(tv_tport->tport_name, t->vhost_wwpn)) {
+			pr_warn("tv_tport->tport_name: %s, tpg->tport_tpgt: %hu"
+				" does not match t->vhost_wwpn: %s, t->vhost_tpgt: %hu\n",
+				tv_tport->tport_name, tpg->tport_tpgt,
+				t->vhost_wwpn, t->vhost_tpgt);
+			ret = -EINVAL;
+			goto err_tpg;
+		}
+		tpg->tv_tpg_vhost_count--;
+		tpg->vhost_scsi = NULL;
+		vs->vs_tpg[target] = NULL;
+		match = true;
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		/*
+		 * Release se_tpg->tpg_group.cg_item configfs dependency now
+		 * to allow vhost-scsi WWPN se_tpg->tpg_group shutdown to occur.
+		 */
+		se_tpg = &tpg->se_tpg;
+		target_undepend_item(&se_tpg->tpg_group.cg_item);
+	}
+	if (match) {
+		for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
+			vq = &vs->vqs[i].vq;
+			mutex_lock(&vq->mutex);
+			vq->private_data = NULL;
+			mutex_unlock(&vq->mutex);
+		}
+	}
+	/*
+	 * Act as synchronize_rcu to make sure access to
+	 * old vs->vs_tpg is finished.
+	 */
+	vhost_scsi_flush(vs);
+	kfree(vs->vs_tpg);
+	vs->vs_tpg = NULL;
+	WARN_ON(vs->vs_events_nr);
+	mutex_unlock(&vs->dev.mutex);
+	mutex_unlock(&vhost_scsi_mutex);
+	return 0;
+
+err_tpg:
+	mutex_unlock(&tpg->tv_tpg_mutex);
+err_dev:
+	mutex_unlock(&vs->dev.mutex);
+	mutex_unlock(&vhost_scsi_mutex);
+	return ret;
+}
+
+static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
+{
+	struct vhost_virtqueue *vq;
+	int i;
+
+	if (features & ~VHOST_SCSI_FEATURES)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&vs->dev.mutex);
+	if ((features & (1 << VHOST_F_LOG_ALL)) &&
+	    !vhost_log_access_ok(&vs->dev)) {
+		mutex_unlock(&vs->dev.mutex);
+		return -EFAULT;
+	}
+
+	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
+		vq = &vs->vqs[i].vq;
+		mutex_lock(&vq->mutex);
+		vq->acked_features = features;
+		mutex_unlock(&vq->mutex);
+	}
+	mutex_unlock(&vs->dev.mutex);
+	return 0;
+}
+
+static int vhost_scsi_open(struct inode *inode, struct file *f)
+{
+	struct vhost_scsi *vs;
+	struct vhost_virtqueue **vqs;
+	int r = -ENOMEM, i;
+
+	vs = kzalloc(sizeof(*vs), GFP_KERNEL | __GFP_NOWARN | __GFP_REPEAT);
+	if (!vs) {
+		vs = vzalloc(sizeof(*vs));
+		if (!vs)
+			goto err_vs;
+	}
+
+	vqs = kmalloc(VHOST_SCSI_MAX_VQ * sizeof(*vqs), GFP_KERNEL);
+	if (!vqs)
+		goto err_vqs;
+
+	vhost_work_init(&vs->vs_completion_work, vhost_scsi_complete_cmd_work);
+	vhost_work_init(&vs->vs_event_work, vhost_scsi_evt_work);
+
+	vs->vs_events_nr = 0;
+	vs->vs_events_missed = false;
+
+	vqs[VHOST_SCSI_VQ_CTL] = &vs->vqs[VHOST_SCSI_VQ_CTL].vq;
+	vqs[VHOST_SCSI_VQ_EVT] = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
+	vs->vqs[VHOST_SCSI_VQ_CTL].vq.handle_kick = vhost_scsi_ctl_handle_kick;
+	vs->vqs[VHOST_SCSI_VQ_EVT].vq.handle_kick = vhost_scsi_evt_handle_kick;
+	for (i = VHOST_SCSI_VQ_IO; i < VHOST_SCSI_MAX_VQ; i++) {
+		vqs[i] = &vs->vqs[i].vq;
+		vs->vqs[i].vq.handle_kick = vhost_scsi_handle_kick;
+	}
+	vhost_dev_init(&vs->dev, vqs, VHOST_SCSI_MAX_VQ);
+
+	vhost_scsi_init_inflight(vs, NULL);
+
+	f->private_data = vs;
+	return 0;
+
+err_vqs:
+	kvfree(vs);
+err_vs:
+	return r;
+}
+
+static int vhost_scsi_release(struct inode *inode, struct file *f)
+{
+	struct vhost_scsi *vs = f->private_data;
+	struct vhost_scsi_target t;
+
+	mutex_lock(&vs->dev.mutex);
+	memcpy(t.vhost_wwpn, vs->vs_vhost_wwpn, sizeof(t.vhost_wwpn));
+	mutex_unlock(&vs->dev.mutex);
+	vhost_scsi_clear_endpoint(vs, &t);
+	vhost_dev_stop(&vs->dev);
+	vhost_dev_cleanup(&vs->dev, false);
+	/* Jobs can re-queue themselves in evt kick handler. Do extra flush. */
+	vhost_scsi_flush(vs);
+	kfree(vs->dev.vqs);
+	kvfree(vs);
+	return 0;
+}
+
+static long
+vhost_scsi_ioctl(struct file *f,
+		 unsigned int ioctl,
+		 unsigned long arg)
+{
+	struct vhost_scsi *vs = f->private_data;
+	struct vhost_scsi_target backend;
+	void __user *argp = (void __user *)arg;
+	u64 __user *featurep = argp;
+	u32 __user *eventsp = argp;
+	u32 events_missed;
+	u64 features;
+	int r, abi_version = VHOST_SCSI_ABI_VERSION;
+	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
+
+	switch (ioctl) {
+	case VHOST_SCSI_SET_ENDPOINT:
+		if (copy_from_user(&backend, argp, sizeof backend))
+			return -EFAULT;
+		if (backend.reserved != 0)
+			return -EOPNOTSUPP;
+
+		return vhost_scsi_set_endpoint(vs, &backend);
+	case VHOST_SCSI_CLEAR_ENDPOINT:
+		if (copy_from_user(&backend, argp, sizeof backend))
+			return -EFAULT;
+		if (backend.reserved != 0)
+			return -EOPNOTSUPP;
+
+		return vhost_scsi_clear_endpoint(vs, &backend);
+	case VHOST_SCSI_GET_ABI_VERSION:
+		if (copy_to_user(argp, &abi_version, sizeof abi_version))
+			return -EFAULT;
+		return 0;
+	case VHOST_SCSI_SET_EVENTS_MISSED:
+		if (get_user(events_missed, eventsp))
+			return -EFAULT;
+		mutex_lock(&vq->mutex);
+		vs->vs_events_missed = events_missed;
+		mutex_unlock(&vq->mutex);
+		return 0;
+	case VHOST_SCSI_GET_EVENTS_MISSED:
+		mutex_lock(&vq->mutex);
+		events_missed = vs->vs_events_missed;
+		mutex_unlock(&vq->mutex);
+		if (put_user(events_missed, eventsp))
+			return -EFAULT;
+		return 0;
+	case VHOST_GET_FEATURES:
+		features = VHOST_SCSI_FEATURES;
+		if (copy_to_user(featurep, &features, sizeof features))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES:
+		if (copy_from_user(&features, featurep, sizeof features))
+			return -EFAULT;
+		return vhost_scsi_set_features(vs, features);
+	default:
+		mutex_lock(&vs->dev.mutex);
+		r = vhost_dev_ioctl(&vs->dev, ioctl, argp);
+		/* TODO: flush backend after dev ioctl. */
+		if (r == -ENOIOCTLCMD)
+			r = vhost_vring_ioctl(&vs->dev, ioctl, argp);
+		mutex_unlock(&vs->dev.mutex);
+		return r;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static long vhost_scsi_compat_ioctl(struct file *f, unsigned int ioctl,
+				unsigned long arg)
+{
+	return vhost_scsi_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+static const struct file_operations vhost_scsi_fops = {
+	.owner          = THIS_MODULE,
+	.release        = vhost_scsi_release,
+	.unlocked_ioctl = vhost_scsi_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= vhost_scsi_compat_ioctl,
+#endif
+	.open           = vhost_scsi_open,
+	.llseek		= noop_llseek,
+};
+
+static struct miscdevice vhost_scsi_misc = {
+	MISC_DYNAMIC_MINOR,
+	"vhost-scsi",
+	&vhost_scsi_fops,
+};
+
+static int __init vhost_scsi_register(void)
+{
+	return misc_register(&vhost_scsi_misc);
+}
+
+static int vhost_scsi_deregister(void)
+{
+	return misc_deregister(&vhost_scsi_misc);
+}
+
+static char *vhost_scsi_dump_proto_id(struct vhost_scsi_tport *tport)
+{
+	switch (tport->tport_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return "SAS";
+	case SCSI_PROTOCOL_FCP:
+		return "FCP";
+	case SCSI_PROTOCOL_ISCSI:
+		return "iSCSI";
+	default:
+		break;
+	}
+
+	return "Unknown";
+}
+
+static void
+vhost_scsi_do_plug(struct vhost_scsi_tpg *tpg,
+		  struct se_lun *lun, bool plug)
+{
+
+	struct vhost_scsi *vs = tpg->vhost_scsi;
+	struct vhost_virtqueue *vq;
+	u32 reason;
+
+	if (!vs)
+		return;
+
+	mutex_lock(&vs->dev.mutex);
+
+	if (plug)
+		reason = VIRTIO_SCSI_EVT_RESET_RESCAN;
+	else
+		reason = VIRTIO_SCSI_EVT_RESET_REMOVED;
+
+	vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
+	mutex_lock(&vq->mutex);
+	if (vhost_has_feature(vq, VIRTIO_SCSI_F_HOTPLUG))
+		vhost_scsi_send_evt(vs, tpg, lun,
+				   VIRTIO_SCSI_T_TRANSPORT_RESET, reason);
+	mutex_unlock(&vq->mutex);
+	mutex_unlock(&vs->dev.mutex);
+}
+
+static void vhost_scsi_hotplug(struct vhost_scsi_tpg *tpg, struct se_lun *lun)
+{
+	vhost_scsi_do_plug(tpg, lun, true);
+}
+
+static void vhost_scsi_hotunplug(struct vhost_scsi_tpg *tpg, struct se_lun *lun)
+{
+	vhost_scsi_do_plug(tpg, lun, false);
+}
+
+static int vhost_scsi_port_link(struct se_portal_group *se_tpg,
+			       struct se_lun *lun)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+
+	mutex_lock(&vhost_scsi_mutex);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count++;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	vhost_scsi_hotplug(tpg, lun);
+
+	mutex_unlock(&vhost_scsi_mutex);
+
+	return 0;
+}
+
+static void vhost_scsi_port_unlink(struct se_portal_group *se_tpg,
+				  struct se_lun *lun)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+
+	mutex_lock(&vhost_scsi_mutex);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	vhost_scsi_hotunplug(tpg, lun);
+
+	mutex_unlock(&vhost_scsi_mutex);
+}
+
+static struct se_node_acl *
+vhost_scsi_make_nodeacl(struct se_portal_group *se_tpg,
+		       struct config_group *group,
+		       const char *name)
+{
+	struct se_node_acl *se_nacl, *se_nacl_new;
+	struct vhost_scsi_nacl *nacl;
+	u64 wwpn = 0;
+	u32 nexus_depth;
+
+	/* vhost_scsi_parse_wwn(name, &wwpn, 1) < 0)
+		return ERR_PTR(-EINVAL); */
+	se_nacl_new = vhost_scsi_alloc_fabric_acl(se_tpg);
+	if (!se_nacl_new)
+		return ERR_PTR(-ENOMEM);
+
+	nexus_depth = 1;
+	/*
+	 * se_nacl_new may be released by core_tpg_add_initiator_node_acl()
+	 * when converting a NodeACL from demo mode -> explict
+	 */
+	se_nacl = core_tpg_add_initiator_node_acl(se_tpg, se_nacl_new,
+				name, nexus_depth);
+	if (IS_ERR(se_nacl)) {
+		vhost_scsi_release_fabric_acl(se_tpg, se_nacl_new);
+		return se_nacl;
+	}
+	/*
+	 * Locate our struct vhost_scsi_nacl and set the FC Nport WWPN
+	 */
+	nacl = container_of(se_nacl, struct vhost_scsi_nacl, se_node_acl);
+	nacl->iport_wwpn = wwpn;
+
+	return se_nacl;
+}
+
+static void vhost_scsi_drop_nodeacl(struct se_node_acl *se_acl)
+{
+	struct vhost_scsi_nacl *nacl = container_of(se_acl,
+				struct vhost_scsi_nacl, se_node_acl);
+	core_tpg_del_initiator_node_acl(se_acl->se_tpg, se_acl, 1);
+	kfree(nacl);
+}
+
+static void vhost_scsi_free_cmd_map_res(struct vhost_scsi_nexus *nexus,
+				       struct se_session *se_sess)
+{
+	struct vhost_scsi_cmd *tv_cmd;
+	unsigned int i;
+
+	if (!se_sess->sess_cmd_map)
+		return;
+
+	for (i = 0; i < VHOST_SCSI_DEFAULT_TAGS; i++) {
+		tv_cmd = &((struct vhost_scsi_cmd *)se_sess->sess_cmd_map)[i];
+
+		kfree(tv_cmd->tvc_sgl);
+		kfree(tv_cmd->tvc_prot_sgl);
+		kfree(tv_cmd->tvc_upages);
+	}
+}
+
+static ssize_t vhost_scsi_tpg_attrib_store_fabric_prot_type(
+	struct se_portal_group *se_tpg,
+	const char *page,
+	size_t count)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	unsigned long val;
+	int ret = kstrtoul(page, 0, &val);
+
+	if (ret) {
+		pr_err("kstrtoul() returned %d for fabric_prot_type\n", ret);
+		return ret;
+	}
+	if (val != 0 && val != 1 && val != 3) {
+		pr_err("Invalid vhost_scsi fabric_prot_type: %lu\n", val);
+		return -EINVAL;
+	}
+	tpg->tv_fabric_prot_type = val;
+
+	return count;
+}
+
+static ssize_t vhost_scsi_tpg_attrib_show_fabric_prot_type(
+	struct se_portal_group *se_tpg,
+	char *page)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+
+	return sprintf(page, "%d\n", tpg->tv_fabric_prot_type);
+}
+TF_TPG_ATTRIB_ATTR(vhost_scsi, fabric_prot_type, S_IRUGO | S_IWUSR);
+
+static struct configfs_attribute *vhost_scsi_tpg_attrib_attrs[] = {
+	&vhost_scsi_tpg_attrib_fabric_prot_type.attr,
+	NULL,
+};
+
+static int vhost_scsi_make_nexus(struct vhost_scsi_tpg *tpg,
+				const char *name)
+{
+	struct se_portal_group *se_tpg;
+	struct se_session *se_sess;
+	struct vhost_scsi_nexus *tv_nexus;
+	struct vhost_scsi_cmd *tv_cmd;
+	unsigned int i;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	if (tpg->tpg_nexus) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_debug("tpg->tpg_nexus already exists\n");
+		return -EEXIST;
+	}
+	se_tpg = &tpg->se_tpg;
+
+	tv_nexus = kzalloc(sizeof(struct vhost_scsi_nexus), GFP_KERNEL);
+	if (!tv_nexus) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to allocate struct vhost_scsi_nexus\n");
+		return -ENOMEM;
+	}
+	/*
+	 *  Initialize the struct se_session pointer and setup tagpool
+	 *  for struct vhost_scsi_cmd descriptors
+	 */
+	tv_nexus->tvn_se_sess = transport_init_session_tags(
+					VHOST_SCSI_DEFAULT_TAGS,
+					sizeof(struct vhost_scsi_cmd),
+					TARGET_PROT_DIN_PASS | TARGET_PROT_DOUT_PASS);
+	if (IS_ERR(tv_nexus->tvn_se_sess)) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		kfree(tv_nexus);
+		return -ENOMEM;
+	}
+	se_sess = tv_nexus->tvn_se_sess;
+	for (i = 0; i < VHOST_SCSI_DEFAULT_TAGS; i++) {
+		tv_cmd = &((struct vhost_scsi_cmd *)se_sess->sess_cmd_map)[i];
+
+		tv_cmd->tvc_sgl = kzalloc(sizeof(struct scatterlist) *
+					VHOST_SCSI_PREALLOC_SGLS, GFP_KERNEL);
+		if (!tv_cmd->tvc_sgl) {
+			mutex_unlock(&tpg->tv_tpg_mutex);
+			pr_err("Unable to allocate tv_cmd->tvc_sgl\n");
+			goto out;
+		}
+
+		tv_cmd->tvc_upages = kzalloc(sizeof(struct page *) *
+					VHOST_SCSI_PREALLOC_UPAGES, GFP_KERNEL);
+		if (!tv_cmd->tvc_upages) {
+			mutex_unlock(&tpg->tv_tpg_mutex);
+			pr_err("Unable to allocate tv_cmd->tvc_upages\n");
+			goto out;
+		}
+
+		tv_cmd->tvc_prot_sgl = kzalloc(sizeof(struct scatterlist) *
+					VHOST_SCSI_PREALLOC_PROT_SGLS, GFP_KERNEL);
+		if (!tv_cmd->tvc_prot_sgl) {
+			mutex_unlock(&tpg->tv_tpg_mutex);
+			pr_err("Unable to allocate tv_cmd->tvc_prot_sgl\n");
+			goto out;
+		}
+	}
+	/*
+	 * Since we are running in 'demo mode' this call with generate a
+	 * struct se_node_acl for the vhost_scsi struct se_portal_group with
+	 * the SCSI Initiator port name of the passed configfs group 'name'.
+	 */
+	tv_nexus->tvn_se_sess->se_node_acl = core_tpg_check_initiator_node_acl(
+				se_tpg, (unsigned char *)name);
+	if (!tv_nexus->tvn_se_sess->se_node_acl) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_debug("core_tpg_check_initiator_node_acl() failed"
+				" for %s\n", name);
+		goto out;
+	}
+	/*
+	 * Now register the TCM vhost virtual I_T Nexus as active.
+	 */
+	transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
+			tv_nexus->tvn_se_sess, tv_nexus);
+	tpg->tpg_nexus = tv_nexus;
+
+	mutex_unlock(&tpg->tv_tpg_mutex);
+	return 0;
+
+out:
+	vhost_scsi_free_cmd_map_res(tv_nexus, se_sess);
+	transport_free_session(se_sess);
+	kfree(tv_nexus);
+	return -ENOMEM;
+}
+
+static int vhost_scsi_drop_nexus(struct vhost_scsi_tpg *tpg)
+{
+	struct se_session *se_sess;
+	struct vhost_scsi_nexus *tv_nexus;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tv_nexus = tpg->tpg_nexus;
+	if (!tv_nexus) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		return -ENODEV;
+	}
+
+	se_sess = tv_nexus->tvn_se_sess;
+	if (!se_sess) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		return -ENODEV;
+	}
+
+	if (tpg->tv_tpg_port_count != 0) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to remove TCM_vhost I_T Nexus with"
+			" active TPG port count: %d\n",
+			tpg->tv_tpg_port_count);
+		return -EBUSY;
+	}
+
+	if (tpg->tv_tpg_vhost_count != 0) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to remove TCM_vhost I_T Nexus with"
+			" active TPG vhost count: %d\n",
+			tpg->tv_tpg_vhost_count);
+		return -EBUSY;
+	}
+
+	pr_debug("TCM_vhost_ConfigFS: Removing I_T Nexus to emulated"
+		" %s Initiator Port: %s\n", vhost_scsi_dump_proto_id(tpg->tport),
+		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
+
+	vhost_scsi_free_cmd_map_res(tv_nexus, se_sess);
+	/*
+	 * Release the SCSI I_T Nexus to the emulated vhost Target Port
+	 */
+	transport_deregister_session(tv_nexus->tvn_se_sess);
+	tpg->tpg_nexus = NULL;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	kfree(tv_nexus);
+	return 0;
+}
+
+static ssize_t vhost_scsi_tpg_show_nexus(struct se_portal_group *se_tpg,
+					char *page)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	struct vhost_scsi_nexus *tv_nexus;
+	ssize_t ret;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tv_nexus = tpg->tpg_nexus;
+	if (!tv_nexus) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		return -ENODEV;
+	}
+	ret = snprintf(page, PAGE_SIZE, "%s\n",
+			tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return ret;
+}
+
+static ssize_t vhost_scsi_tpg_store_nexus(struct se_portal_group *se_tpg,
+					 const char *page,
+					 size_t count)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+	struct vhost_scsi_tport *tport_wwn = tpg->tport;
+	unsigned char i_port[VHOST_SCSI_NAMELEN], *ptr, *port_ptr;
+	int ret;
+	/*
+	 * Shutdown the active I_T nexus if 'NULL' is passed..
+	 */
+	if (!strncmp(page, "NULL", 4)) {
+		ret = vhost_scsi_drop_nexus(tpg);
+		return (!ret) ? count : ret;
+	}
+	/*
+	 * Otherwise make sure the passed virtual Initiator port WWN matches
+	 * the fabric protocol_id set in vhost_scsi_make_tport(), and call
+	 * vhost_scsi_make_nexus().
+	 */
+	if (strlen(page) >= VHOST_SCSI_NAMELEN) {
+		pr_err("Emulated NAA Sas Address: %s, exceeds"
+				" max: %d\n", page, VHOST_SCSI_NAMELEN);
+		return -EINVAL;
+	}
+	snprintf(&i_port[0], VHOST_SCSI_NAMELEN, "%s", page);
+
+	ptr = strstr(i_port, "naa.");
+	if (ptr) {
+		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_SAS) {
+			pr_err("Passed SAS Initiator Port %s does not"
+				" match target port protoid: %s\n", i_port,
+				vhost_scsi_dump_proto_id(tport_wwn));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[0];
+		goto check_newline;
+	}
+	ptr = strstr(i_port, "fc.");
+	if (ptr) {
+		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_FCP) {
+			pr_err("Passed FCP Initiator Port %s does not"
+				" match target port protoid: %s\n", i_port,
+				vhost_scsi_dump_proto_id(tport_wwn));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[3]; /* Skip over "fc." */
+		goto check_newline;
+	}
+	ptr = strstr(i_port, "iqn.");
+	if (ptr) {
+		if (tport_wwn->tport_proto_id != SCSI_PROTOCOL_ISCSI) {
+			pr_err("Passed iSCSI Initiator Port %s does not"
+				" match target port protoid: %s\n", i_port,
+				vhost_scsi_dump_proto_id(tport_wwn));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[0];
+		goto check_newline;
+	}
+	pr_err("Unable to locate prefix for emulated Initiator Port:"
+			" %s\n", i_port);
+	return -EINVAL;
+	/*
+	 * Clear any trailing newline for the NAA WWN
+	 */
+check_newline:
+	if (i_port[strlen(i_port)-1] == '\n')
+		i_port[strlen(i_port)-1] = '\0';
+
+	ret = vhost_scsi_make_nexus(tpg, port_ptr);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+TF_TPG_BASE_ATTR(vhost_scsi, nexus, S_IRUGO | S_IWUSR);
+
+static struct configfs_attribute *vhost_scsi_tpg_attrs[] = {
+	&vhost_scsi_tpg_nexus.attr,
+	NULL,
+};
+
+static struct se_portal_group *
+vhost_scsi_make_tpg(struct se_wwn *wwn,
+		   struct config_group *group,
+		   const char *name)
+{
+	struct vhost_scsi_tport *tport = container_of(wwn,
+			struct vhost_scsi_tport, tport_wwn);
+
+	struct vhost_scsi_tpg *tpg;
+	u16 tpgt;
+	int ret;
+
+	if (strstr(name, "tpgt_") != name)
+		return ERR_PTR(-EINVAL);
+	if (kstrtou16(name + 5, 10, &tpgt) || tpgt >= VHOST_SCSI_MAX_TARGET)
+		return ERR_PTR(-EINVAL);
+
+	tpg = kzalloc(sizeof(struct vhost_scsi_tpg), GFP_KERNEL);
+	if (!tpg) {
+		pr_err("Unable to allocate struct vhost_scsi_tpg");
+		return ERR_PTR(-ENOMEM);
+	}
+	mutex_init(&tpg->tv_tpg_mutex);
+	INIT_LIST_HEAD(&tpg->tv_tpg_list);
+	tpg->tport = tport;
+	tpg->tport_tpgt = tpgt;
+
+	ret = core_tpg_register(&vhost_scsi_ops, wwn,
+				&tpg->se_tpg, tpg, TRANSPORT_TPG_TYPE_NORMAL);
+	if (ret < 0) {
+		kfree(tpg);
+		return NULL;
+	}
+	mutex_lock(&vhost_scsi_mutex);
+	list_add_tail(&tpg->tv_tpg_list, &vhost_scsi_list);
+	mutex_unlock(&vhost_scsi_mutex);
+
+	return &tpg->se_tpg;
+}
+
+static void vhost_scsi_drop_tpg(struct se_portal_group *se_tpg)
+{
+	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
+				struct vhost_scsi_tpg, se_tpg);
+
+	mutex_lock(&vhost_scsi_mutex);
+	list_del(&tpg->tv_tpg_list);
+	mutex_unlock(&vhost_scsi_mutex);
+	/*
+	 * Release the virtual I_T Nexus for this vhost TPG
+	 */
+	vhost_scsi_drop_nexus(tpg);
+	/*
+	 * Deregister the se_tpg from TCM..
+	 */
+	core_tpg_deregister(se_tpg);
+	kfree(tpg);
+}
+
+static struct se_wwn *
+vhost_scsi_make_tport(struct target_fabric_configfs *tf,
+		     struct config_group *group,
+		     const char *name)
+{
+	struct vhost_scsi_tport *tport;
+	char *ptr;
+	u64 wwpn = 0;
+	int off = 0;
+
+	/* if (vhost_scsi_parse_wwn(name, &wwpn, 1) < 0)
+		return ERR_PTR(-EINVAL); */
+
+	tport = kzalloc(sizeof(struct vhost_scsi_tport), GFP_KERNEL);
+	if (!tport) {
+		pr_err("Unable to allocate struct vhost_scsi_tport");
+		return ERR_PTR(-ENOMEM);
+	}
+	tport->tport_wwpn = wwpn;
+	/*
+	 * Determine the emulated Protocol Identifier and Target Port Name
+	 * based on the incoming configfs directory name.
+	 */
+	ptr = strstr(name, "naa.");
+	if (ptr) {
+		tport->tport_proto_id = SCSI_PROTOCOL_SAS;
+		goto check_len;
+	}
+	ptr = strstr(name, "fc.");
+	if (ptr) {
+		tport->tport_proto_id = SCSI_PROTOCOL_FCP;
+		off = 3; /* Skip over "fc." */
+		goto check_len;
+	}
+	ptr = strstr(name, "iqn.");
+	if (ptr) {
+		tport->tport_proto_id = SCSI_PROTOCOL_ISCSI;
+		goto check_len;
+	}
+
+	pr_err("Unable to locate prefix for emulated Target Port:"
+			" %s\n", name);
+	kfree(tport);
+	return ERR_PTR(-EINVAL);
+
+check_len:
+	if (strlen(name) >= VHOST_SCSI_NAMELEN) {
+		pr_err("Emulated %s Address: %s, exceeds"
+			" max: %d\n", name, vhost_scsi_dump_proto_id(tport),
+			VHOST_SCSI_NAMELEN);
+		kfree(tport);
+		return ERR_PTR(-EINVAL);
+	}
+	snprintf(&tport->tport_name[0], VHOST_SCSI_NAMELEN, "%s", &name[off]);
+
+	pr_debug("TCM_VHost_ConfigFS: Allocated emulated Target"
+		" %s Address: %s\n", vhost_scsi_dump_proto_id(tport), name);
+
+	return &tport->tport_wwn;
+}
+
+static void vhost_scsi_drop_tport(struct se_wwn *wwn)
+{
+	struct vhost_scsi_tport *tport = container_of(wwn,
+				struct vhost_scsi_tport, tport_wwn);
+
+	pr_debug("TCM_VHost_ConfigFS: Deallocating emulated Target"
+		" %s Address: %s\n", vhost_scsi_dump_proto_id(tport),
+		tport->tport_name);
+
+	kfree(tport);
+}
+
+static ssize_t
+vhost_scsi_wwn_show_attr_version(struct target_fabric_configfs *tf,
+				char *page)
+{
+	return sprintf(page, "TCM_VHOST fabric module %s on %s/%s"
+		"on "UTS_RELEASE"\n", VHOST_SCSI_VERSION, utsname()->sysname,
+		utsname()->machine);
+}
+
+TF_WWN_ATTR_RO(vhost_scsi, version);
+
+static struct configfs_attribute *vhost_scsi_wwn_attrs[] = {
+	&vhost_scsi_wwn_version.attr,
+	NULL,
+};
+
+static struct target_core_fabric_ops vhost_scsi_ops = {
+	.module				= THIS_MODULE,
+	.name				= "vhost",
+	.get_fabric_name		= vhost_scsi_get_fabric_name,
+	.get_fabric_proto_ident		= vhost_scsi_get_fabric_proto_ident,
+	.tpg_get_wwn			= vhost_scsi_get_fabric_wwn,
+	.tpg_get_tag			= vhost_scsi_get_tpgt,
+	.tpg_get_default_depth		= vhost_scsi_get_default_depth,
+	.tpg_get_pr_transport_id	= vhost_scsi_get_pr_transport_id,
+	.tpg_get_pr_transport_id_len	= vhost_scsi_get_pr_transport_id_len,
+	.tpg_parse_pr_out_transport_id	= vhost_scsi_parse_pr_out_transport_id,
+	.tpg_check_demo_mode		= vhost_scsi_check_true,
+	.tpg_check_demo_mode_cache	= vhost_scsi_check_true,
+	.tpg_check_demo_mode_write_protect = vhost_scsi_check_false,
+	.tpg_check_prod_mode_write_protect = vhost_scsi_check_false,
+	.tpg_check_prot_fabric_only	= vhost_scsi_check_prot_fabric_only,
+	.tpg_alloc_fabric_acl		= vhost_scsi_alloc_fabric_acl,
+	.tpg_release_fabric_acl		= vhost_scsi_release_fabric_acl,
+	.tpg_get_inst_index		= vhost_scsi_tpg_get_inst_index,
+	.release_cmd			= vhost_scsi_release_cmd,
+	.check_stop_free		= vhost_scsi_check_stop_free,
+	.shutdown_session		= vhost_scsi_shutdown_session,
+	.close_session			= vhost_scsi_close_session,
+	.sess_get_index			= vhost_scsi_sess_get_index,
+	.sess_get_initiator_sid		= NULL,
+	.write_pending			= vhost_scsi_write_pending,
+	.write_pending_status		= vhost_scsi_write_pending_status,
+	.set_default_node_attributes	= vhost_scsi_set_default_node_attrs,
+	.get_task_tag			= vhost_scsi_get_task_tag,
+	.get_cmd_state			= vhost_scsi_get_cmd_state,
+	.queue_data_in			= vhost_scsi_queue_data_in,
+	.queue_status			= vhost_scsi_queue_status,
+	.queue_tm_rsp			= vhost_scsi_queue_tm_rsp,
+	.aborted_task			= vhost_scsi_aborted_task,
+	/*
+	 * Setup callers for generic logic in target_core_fabric_configfs.c
+	 */
+	.fabric_make_wwn		= vhost_scsi_make_tport,
+	.fabric_drop_wwn		= vhost_scsi_drop_tport,
+	.fabric_make_tpg		= vhost_scsi_make_tpg,
+	.fabric_drop_tpg		= vhost_scsi_drop_tpg,
+	.fabric_post_link		= vhost_scsi_port_link,
+	.fabric_pre_unlink		= vhost_scsi_port_unlink,
+	.fabric_make_np			= NULL,
+	.fabric_drop_np			= NULL,
+	.fabric_make_nodeacl		= vhost_scsi_make_nodeacl,
+	.fabric_drop_nodeacl		= vhost_scsi_drop_nodeacl,
+
+	.tfc_wwn_attrs			= vhost_scsi_wwn_attrs,
+	.tfc_tpg_base_attrs		= vhost_scsi_tpg_attrs,
+	.tfc_tpg_attrib_attrs		= vhost_scsi_tpg_attrib_attrs,
+};
+
+static int __init vhost_scsi_init(void)
+{
+	int ret = -ENOMEM;
+
+	pr_debug("TCM_VHOST fabric module %s on %s/%s"
+		" on "UTS_RELEASE"\n", VHOST_SCSI_VERSION, utsname()->sysname,
+		utsname()->machine);
+
+	/*
+	 * Use our own dedicated workqueue for submitting I/O into
+	 * target core to avoid contention within system_wq.
+	 */
+	vhost_scsi_workqueue = alloc_workqueue("vhost_scsi", 0, 0);
+	if (!vhost_scsi_workqueue)
+		goto out;
+
+	ret = vhost_scsi_register();
+	if (ret < 0)
+		goto out_destroy_workqueue;
+
+	ret = target_register_template(&vhost_scsi_ops);
+	if (ret < 0)
+		goto out_vhost_scsi_deregister;
+
+	return 0;
+
+out_vhost_scsi_deregister:
+	vhost_scsi_deregister();
+out_destroy_workqueue:
+	destroy_workqueue(vhost_scsi_workqueue);
+out:
+	return ret;
+};
+
+static void vhost_scsi_exit(void)
+{
+	target_unregister_template(&vhost_scsi_ops);
+	vhost_scsi_deregister();
+	destroy_workqueue(vhost_scsi_workqueue);
+};
+
+MODULE_DESCRIPTION("VHOST_SCSI series fabric driver");
+MODULE_ALIAS("tcm_vhost");
+MODULE_LICENSE("GPL");
+module_init(vhost_scsi_init);
+module_exit(vhost_scsi_exit);
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c
new file mode 100644
index 000000000..d9c501eaa
--- /dev/null
+++ b/drivers/vhost/test.c
@@ -0,0 +1,338 @@
+/* Copyright (C) 2009 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * test virtio server in host kernel.
+ */
+
+#include <linux/compat.h>
+#include <linux/eventfd.h>
+#include <linux/vhost.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/workqueue.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+
+#include "test.h"
+#include "vhost.h"
+
+/* Max number of bytes transferred before requeueing the job.
+ * Using this limit prevents one virtqueue from starving others. */
+#define VHOST_TEST_WEIGHT 0x80000
+
+enum {
+	VHOST_TEST_VQ = 0,
+	VHOST_TEST_VQ_MAX = 1,
+};
+
+struct vhost_test {
+	struct vhost_dev dev;
+	struct vhost_virtqueue vqs[VHOST_TEST_VQ_MAX];
+};
+
+/* Expects to be always run from workqueue - which acts as
+ * read-size critical section for our kind of RCU. */
+static void handle_vq(struct vhost_test *n)
+{
+	struct vhost_virtqueue *vq = &n->vqs[VHOST_TEST_VQ];
+	unsigned out, in;
+	int head;
+	size_t len, total_len = 0;
+	void *private;
+
+	mutex_lock(&vq->mutex);
+	private = vq->private_data;
+	if (!private) {
+		mutex_unlock(&vq->mutex);
+		return;
+	}
+
+	vhost_disable_notify(&n->dev, vq);
+
+	for (;;) {
+		head = vhost_get_vq_desc(vq, vq->iov,
+					 ARRAY_SIZE(vq->iov),
+					 &out, &in,
+					 NULL, NULL);
+		/* On error, stop handling until the next kick. */
+		if (unlikely(head < 0))
+			break;
+		/* Nothing new?  Wait for eventfd to tell us they refilled. */
+		if (head == vq->num) {
+			if (unlikely(vhost_enable_notify(&n->dev, vq))) {
+				vhost_disable_notify(&n->dev, vq);
+				continue;
+			}
+			break;
+		}
+		if (in) {
+			vq_err(vq, "Unexpected descriptor format for TX: "
+			       "out %d, int %d\n", out, in);
+			break;
+		}
+		len = iov_length(vq->iov, out);
+		/* Sanity check */
+		if (!len) {
+			vq_err(vq, "Unexpected 0 len for TX\n");
+			break;
+		}
+		vhost_add_used_and_signal(&n->dev, vq, head, 0);
+		total_len += len;
+		if (unlikely(total_len >= VHOST_TEST_WEIGHT)) {
+			vhost_poll_queue(&vq->poll);
+			break;
+		}
+	}
+
+	mutex_unlock(&vq->mutex);
+}
+
+static void handle_vq_kick(struct vhost_work *work)
+{
+	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
+						  poll.work);
+	struct vhost_test *n = container_of(vq->dev, struct vhost_test, dev);
+
+	handle_vq(n);
+}
+
+static int vhost_test_open(struct inode *inode, struct file *f)
+{
+	struct vhost_test *n = kmalloc(sizeof *n, GFP_KERNEL);
+	struct vhost_dev *dev;
+	struct vhost_virtqueue **vqs;
+
+	if (!n)
+		return -ENOMEM;
+	vqs = kmalloc(VHOST_TEST_VQ_MAX * sizeof(*vqs), GFP_KERNEL);
+	if (!vqs) {
+		kfree(n);
+		return -ENOMEM;
+	}
+
+	dev = &n->dev;
+	vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ];
+	n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick;
+	vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX);
+
+	f->private_data = n;
+
+	return 0;
+}
+
+static void *vhost_test_stop_vq(struct vhost_test *n,
+				struct vhost_virtqueue *vq)
+{
+	void *private;
+
+	mutex_lock(&vq->mutex);
+	private = vq->private_data;
+	vq->private_data = NULL;
+	mutex_unlock(&vq->mutex);
+	return private;
+}
+
+static void vhost_test_stop(struct vhost_test *n, void **privatep)
+{
+	*privatep = vhost_test_stop_vq(n, n->vqs + VHOST_TEST_VQ);
+}
+
+static void vhost_test_flush_vq(struct vhost_test *n, int index)
+{
+	vhost_poll_flush(&n->vqs[index].poll);
+}
+
+static void vhost_test_flush(struct vhost_test *n)
+{
+	vhost_test_flush_vq(n, VHOST_TEST_VQ);
+}
+
+static int vhost_test_release(struct inode *inode, struct file *f)
+{
+	struct vhost_test *n = f->private_data;
+	void  *private;
+
+	vhost_test_stop(n, &private);
+	vhost_test_flush(n);
+	vhost_dev_cleanup(&n->dev, false);
+	/* We do an extra flush before freeing memory,
+	 * since jobs can re-queue themselves. */
+	vhost_test_flush(n);
+	kfree(n);
+	return 0;
+}
+
+static long vhost_test_run(struct vhost_test *n, int test)
+{
+	void *priv, *oldpriv;
+	struct vhost_virtqueue *vq;
+	int r, index;
+
+	if (test < 0 || test > 1)
+		return -EINVAL;
+
+	mutex_lock(&n->dev.mutex);
+	r = vhost_dev_check_owner(&n->dev);
+	if (r)
+		goto err;
+
+	for (index = 0; index < n->dev.nvqs; ++index) {
+		/* Verify that ring has been setup correctly. */
+		if (!vhost_vq_access_ok(&n->vqs[index])) {
+			r = -EFAULT;
+			goto err;
+		}
+	}
+
+	for (index = 0; index < n->dev.nvqs; ++index) {
+		vq = n->vqs + index;
+		mutex_lock(&vq->mutex);
+		priv = test ? n : NULL;
+
+		/* start polling new socket */
+		oldpriv = vq->private_data;
+		vq->private_data = priv;
+
+		r = vhost_init_used(&n->vqs[index]);
+
+		mutex_unlock(&vq->mutex);
+
+		if (r)
+			goto err;
+
+		if (oldpriv) {
+			vhost_test_flush_vq(n, index);
+		}
+	}
+
+	mutex_unlock(&n->dev.mutex);
+	return 0;
+
+err:
+	mutex_unlock(&n->dev.mutex);
+	return r;
+}
+
+static long vhost_test_reset_owner(struct vhost_test *n)
+{
+	void *priv = NULL;
+	long err;
+	struct vhost_memory *memory;
+
+	mutex_lock(&n->dev.mutex);
+	err = vhost_dev_check_owner(&n->dev);
+	if (err)
+		goto done;
+	memory = vhost_dev_reset_owner_prepare();
+	if (!memory) {
+		err = -ENOMEM;
+		goto done;
+	}
+	vhost_test_stop(n, &priv);
+	vhost_test_flush(n);
+	vhost_dev_reset_owner(&n->dev, memory);
+done:
+	mutex_unlock(&n->dev.mutex);
+	return err;
+}
+
+static int vhost_test_set_features(struct vhost_test *n, u64 features)
+{
+	struct vhost_virtqueue *vq;
+
+	mutex_lock(&n->dev.mutex);
+	if ((features & (1 << VHOST_F_LOG_ALL)) &&
+	    !vhost_log_access_ok(&n->dev)) {
+		mutex_unlock(&n->dev.mutex);
+		return -EFAULT;
+	}
+	vq = &n->vqs[VHOST_TEST_VQ];
+	mutex_lock(&vq->mutex);
+	vq->acked_features = features;
+	mutex_unlock(&vq->mutex);
+	mutex_unlock(&n->dev.mutex);
+	return 0;
+}
+
+static long vhost_test_ioctl(struct file *f, unsigned int ioctl,
+			     unsigned long arg)
+{
+	struct vhost_test *n = f->private_data;
+	void __user *argp = (void __user *)arg;
+	u64 __user *featurep = argp;
+	int test;
+	u64 features;
+	int r;
+	switch (ioctl) {
+	case VHOST_TEST_RUN:
+		if (copy_from_user(&test, argp, sizeof test))
+			return -EFAULT;
+		return vhost_test_run(n, test);
+	case VHOST_GET_FEATURES:
+		features = VHOST_FEATURES;
+		if (copy_to_user(featurep, &features, sizeof features))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES:
+		if (copy_from_user(&features, featurep, sizeof features))
+			return -EFAULT;
+		if (features & ~VHOST_FEATURES)
+			return -EOPNOTSUPP;
+		return vhost_test_set_features(n, features);
+	case VHOST_RESET_OWNER:
+		return vhost_test_reset_owner(n);
+	default:
+		mutex_lock(&n->dev.mutex);
+		r = vhost_dev_ioctl(&n->dev, ioctl, argp);
+                if (r == -ENOIOCTLCMD)
+                        r = vhost_vring_ioctl(&n->dev, ioctl, argp);
+		vhost_test_flush(n);
+		mutex_unlock(&n->dev.mutex);
+		return r;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+static long vhost_test_compat_ioctl(struct file *f, unsigned int ioctl,
+				   unsigned long arg)
+{
+	return vhost_test_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+static const struct file_operations vhost_test_fops = {
+	.owner          = THIS_MODULE,
+	.release        = vhost_test_release,
+	.unlocked_ioctl = vhost_test_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = vhost_test_compat_ioctl,
+#endif
+	.open           = vhost_test_open,
+	.llseek		= noop_llseek,
+};
+
+static struct miscdevice vhost_test_misc = {
+	MISC_DYNAMIC_MINOR,
+	"vhost-test",
+	&vhost_test_fops,
+};
+
+static int vhost_test_init(void)
+{
+	return misc_register(&vhost_test_misc);
+}
+module_init(vhost_test_init);
+
+static void vhost_test_exit(void)
+{
+	misc_deregister(&vhost_test_misc);
+}
+module_exit(vhost_test_exit);
+
+MODULE_VERSION("0.0.1");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Michael S. Tsirkin");
+MODULE_DESCRIPTION("Host kernel side for virtio simulator");
diff --git a/drivers/vhost/test.h b/drivers/vhost/test.h
new file mode 100644
index 000000000..1fef5df82
--- /dev/null
+++ b/drivers/vhost/test.h
@@ -0,0 +1,7 @@
+#ifndef LINUX_VHOST_TEST_H
+#define LINUX_VHOST_TEST_H
+
+/* Start a given test on the virtio null device. 0 stops all tests. */
+#define VHOST_TEST_RUN _IOW(VHOST_VIRTIO, 0x31, int)
+
+#endif
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
new file mode 100644
index 000000000..2ee28266f
--- /dev/null
+++ b/drivers/vhost/vhost.c
@@ -0,0 +1,1583 @@
+/* Copyright (C) 2009 Red Hat, Inc.
+ * Copyright (C) 2006 Rusty Russell IBM Corporation
+ *
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ *
+ * Inspiration, some code, and most witty comments come from
+ * Documentation/virtual/lguest/lguest.c, by Rusty Russell
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Generic code for virtio server in host kernel.
+ */
+
+#include <linux/eventfd.h>
+#include <linux/vhost.h>
+#include <linux/uio.h>
+#include <linux/mm.h>
+#include <linux/mmu_context.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/poll.h>
+#include <linux/file.h>
+#include <linux/highmem.h>
+#include <linux/slab.h>
+#include <linux/kthread.h>
+#include <linux/cgroup.h>
+#include <linux/module.h>
+
+#include "vhost.h"
+
+enum {
+	VHOST_MEMORY_MAX_NREGIONS = 64,
+	VHOST_MEMORY_F_LOG = 0x1,
+};
+
+#define vhost_used_event(vq) ((__virtio16 __user *)&vq->avail->ring[vq->num])
+#define vhost_avail_event(vq) ((__virtio16 __user *)&vq->used->ring[vq->num])
+
+static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
+			    poll_table *pt)
+{
+	struct vhost_poll *poll;
+
+	poll = container_of(pt, struct vhost_poll, table);
+	poll->wqh = wqh;
+	add_wait_queue(wqh, &poll->wait);
+}
+
+static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
+			     void *key)
+{
+	struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
+
+	if (!((unsigned long)key & poll->mask))
+		return 0;
+
+	vhost_poll_queue(poll);
+	return 0;
+}
+
+void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
+{
+	INIT_LIST_HEAD(&work->node);
+	work->fn = fn;
+	init_waitqueue_head(&work->done);
+	work->flushing = 0;
+	work->queue_seq = work->done_seq = 0;
+}
+EXPORT_SYMBOL_GPL(vhost_work_init);
+
+/* Init poll structure */
+void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
+		     unsigned long mask, struct vhost_dev *dev)
+{
+	init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
+	init_poll_funcptr(&poll->table, vhost_poll_func);
+	poll->mask = mask;
+	poll->dev = dev;
+	poll->wqh = NULL;
+
+	vhost_work_init(&poll->work, fn);
+}
+EXPORT_SYMBOL_GPL(vhost_poll_init);
+
+/* Start polling a file. We add ourselves to file's wait queue. The caller must
+ * keep a reference to a file until after vhost_poll_stop is called. */
+int vhost_poll_start(struct vhost_poll *poll, struct file *file)
+{
+	unsigned long mask;
+	int ret = 0;
+
+	if (poll->wqh)
+		return 0;
+
+	mask = file->f_op->poll(file, &poll->table);
+	if (mask)
+		vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
+	if (mask & POLLERR) {
+		if (poll->wqh)
+			remove_wait_queue(poll->wqh, &poll->wait);
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(vhost_poll_start);
+
+/* Stop polling a file. After this function returns, it becomes safe to drop the
+ * file reference. You must also flush afterwards. */
+void vhost_poll_stop(struct vhost_poll *poll)
+{
+	if (poll->wqh) {
+		remove_wait_queue(poll->wqh, &poll->wait);
+		poll->wqh = NULL;
+	}
+}
+EXPORT_SYMBOL_GPL(vhost_poll_stop);
+
+static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
+				unsigned seq)
+{
+	int left;
+
+	spin_lock_irq(&dev->work_lock);
+	left = seq - work->done_seq;
+	spin_unlock_irq(&dev->work_lock);
+	return left <= 0;
+}
+
+void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
+{
+	unsigned seq;
+	int flushing;
+
+	spin_lock_irq(&dev->work_lock);
+	seq = work->queue_seq;
+	work->flushing++;
+	spin_unlock_irq(&dev->work_lock);
+	wait_event(work->done, vhost_work_seq_done(dev, work, seq));
+	spin_lock_irq(&dev->work_lock);
+	flushing = --work->flushing;
+	spin_unlock_irq(&dev->work_lock);
+	BUG_ON(flushing < 0);
+}
+EXPORT_SYMBOL_GPL(vhost_work_flush);
+
+/* Flush any work that has been scheduled. When calling this, don't hold any
+ * locks that are also used by the callback. */
+void vhost_poll_flush(struct vhost_poll *poll)
+{
+	vhost_work_flush(poll->dev, &poll->work);
+}
+EXPORT_SYMBOL_GPL(vhost_poll_flush);
+
+void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->work_lock, flags);
+	if (list_empty(&work->node)) {
+		list_add_tail(&work->node, &dev->work_list);
+		work->queue_seq++;
+		spin_unlock_irqrestore(&dev->work_lock, flags);
+		wake_up_process(dev->worker);
+	} else {
+		spin_unlock_irqrestore(&dev->work_lock, flags);
+	}
+}
+EXPORT_SYMBOL_GPL(vhost_work_queue);
+
+void vhost_poll_queue(struct vhost_poll *poll)
+{
+	vhost_work_queue(poll->dev, &poll->work);
+}
+EXPORT_SYMBOL_GPL(vhost_poll_queue);
+
+static void vhost_vq_reset(struct vhost_dev *dev,
+			   struct vhost_virtqueue *vq)
+{
+	vq->num = 1;
+	vq->desc = NULL;
+	vq->avail = NULL;
+	vq->used = NULL;
+	vq->last_avail_idx = 0;
+	vq->avail_idx = 0;
+	vq->last_used_idx = 0;
+	vq->signalled_used = 0;
+	vq->signalled_used_valid = false;
+	vq->used_flags = 0;
+	vq->log_used = false;
+	vq->log_addr = -1ull;
+	vq->private_data = NULL;
+	vq->acked_features = 0;
+	vq->log_base = NULL;
+	vq->error_ctx = NULL;
+	vq->error = NULL;
+	vq->kick = NULL;
+	vq->call_ctx = NULL;
+	vq->call = NULL;
+	vq->log_ctx = NULL;
+	vq->memory = NULL;
+}
+
+static int vhost_worker(void *data)
+{
+	struct vhost_dev *dev = data;
+	struct vhost_work *work = NULL;
+	unsigned uninitialized_var(seq);
+	mm_segment_t oldfs = get_fs();
+
+	set_fs(USER_DS);
+	use_mm(dev->mm);
+
+	for (;;) {
+		/* mb paired w/ kthread_stop */
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		spin_lock_irq(&dev->work_lock);
+		if (work) {
+			work->done_seq = seq;
+			if (work->flushing)
+				wake_up_all(&work->done);
+		}
+
+		if (kthread_should_stop()) {
+			spin_unlock_irq(&dev->work_lock);
+			__set_current_state(TASK_RUNNING);
+			break;
+		}
+		if (!list_empty(&dev->work_list)) {
+			work = list_first_entry(&dev->work_list,
+						struct vhost_work, node);
+			list_del_init(&work->node);
+			seq = work->queue_seq;
+		} else
+			work = NULL;
+		spin_unlock_irq(&dev->work_lock);
+
+		if (work) {
+			__set_current_state(TASK_RUNNING);
+			work->fn(work);
+			if (need_resched())
+				schedule();
+		} else
+			schedule();
+
+	}
+	unuse_mm(dev->mm);
+	set_fs(oldfs);
+	return 0;
+}
+
+static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
+{
+	kfree(vq->indirect);
+	vq->indirect = NULL;
+	kfree(vq->log);
+	vq->log = NULL;
+	kfree(vq->heads);
+	vq->heads = NULL;
+}
+
+/* Helper to allocate iovec buffers for all vqs. */
+static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
+{
+	struct vhost_virtqueue *vq;
+	int i;
+
+	for (i = 0; i < dev->nvqs; ++i) {
+		vq = dev->vqs[i];
+		vq->indirect = kmalloc(sizeof *vq->indirect * UIO_MAXIOV,
+				       GFP_KERNEL);
+		vq->log = kmalloc(sizeof *vq->log * UIO_MAXIOV, GFP_KERNEL);
+		vq->heads = kmalloc(sizeof *vq->heads * UIO_MAXIOV, GFP_KERNEL);
+		if (!vq->indirect || !vq->log || !vq->heads)
+			goto err_nomem;
+	}
+	return 0;
+
+err_nomem:
+	for (; i >= 0; --i)
+		vhost_vq_free_iovecs(dev->vqs[i]);
+	return -ENOMEM;
+}
+
+static void vhost_dev_free_iovecs(struct vhost_dev *dev)
+{
+	int i;
+
+	for (i = 0; i < dev->nvqs; ++i)
+		vhost_vq_free_iovecs(dev->vqs[i]);
+}
+
+void vhost_dev_init(struct vhost_dev *dev,
+		    struct vhost_virtqueue **vqs, int nvqs)
+{
+	struct vhost_virtqueue *vq;
+	int i;
+
+	dev->vqs = vqs;
+	dev->nvqs = nvqs;
+	mutex_init(&dev->mutex);
+	dev->log_ctx = NULL;
+	dev->log_file = NULL;
+	dev->memory = NULL;
+	dev->mm = NULL;
+	spin_lock_init(&dev->work_lock);
+	INIT_LIST_HEAD(&dev->work_list);
+	dev->worker = NULL;
+
+	for (i = 0; i < dev->nvqs; ++i) {
+		vq = dev->vqs[i];
+		vq->log = NULL;
+		vq->indirect = NULL;
+		vq->heads = NULL;
+		vq->dev = dev;
+		mutex_init(&vq->mutex);
+		vhost_vq_reset(dev, vq);
+		if (vq->handle_kick)
+			vhost_poll_init(&vq->poll, vq->handle_kick,
+					POLLIN, dev);
+	}
+}
+EXPORT_SYMBOL_GPL(vhost_dev_init);
+
+/* Caller should have device mutex */
+long vhost_dev_check_owner(struct vhost_dev *dev)
+{
+	/* Are you the owner? If not, I don't think you mean to do that */
+	return dev->mm == current->mm ? 0 : -EPERM;
+}
+EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
+
+struct vhost_attach_cgroups_struct {
+	struct vhost_work work;
+	struct task_struct *owner;
+	int ret;
+};
+
+static void vhost_attach_cgroups_work(struct vhost_work *work)
+{
+	struct vhost_attach_cgroups_struct *s;
+
+	s = container_of(work, struct vhost_attach_cgroups_struct, work);
+	s->ret = cgroup_attach_task_all(s->owner, current);
+}
+
+static int vhost_attach_cgroups(struct vhost_dev *dev)
+{
+	struct vhost_attach_cgroups_struct attach;
+
+	attach.owner = current;
+	vhost_work_init(&attach.work, vhost_attach_cgroups_work);
+	vhost_work_queue(dev, &attach.work);
+	vhost_work_flush(dev, &attach.work);
+	return attach.ret;
+}
+
+/* Caller should have device mutex */
+bool vhost_dev_has_owner(struct vhost_dev *dev)
+{
+	return dev->mm;
+}
+EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
+
+/* Caller should have device mutex */
+long vhost_dev_set_owner(struct vhost_dev *dev)
+{
+	struct task_struct *worker;
+	int err;
+
+	/* Is there an owner already? */
+	if (vhost_dev_has_owner(dev)) {
+		err = -EBUSY;
+		goto err_mm;
+	}
+
+	/* No owner, become one */
+	dev->mm = get_task_mm(current);
+	worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
+	if (IS_ERR(worker)) {
+		err = PTR_ERR(worker);
+		goto err_worker;
+	}
+
+	dev->worker = worker;
+	wake_up_process(worker);	/* avoid contributing to loadavg */
+
+	err = vhost_attach_cgroups(dev);
+	if (err)
+		goto err_cgroup;
+
+	err = vhost_dev_alloc_iovecs(dev);
+	if (err)
+		goto err_cgroup;
+
+	return 0;
+err_cgroup:
+	kthread_stop(worker);
+	dev->worker = NULL;
+err_worker:
+	if (dev->mm)
+		mmput(dev->mm);
+	dev->mm = NULL;
+err_mm:
+	return err;
+}
+EXPORT_SYMBOL_GPL(vhost_dev_set_owner);
+
+struct vhost_memory *vhost_dev_reset_owner_prepare(void)
+{
+	return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(vhost_dev_reset_owner_prepare);
+
+/* Caller should have device mutex */
+void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory *memory)
+{
+	int i;
+
+	vhost_dev_cleanup(dev, true);
+
+	/* Restore memory to default empty mapping. */
+	memory->nregions = 0;
+	dev->memory = memory;
+	/* We don't need VQ locks below since vhost_dev_cleanup makes sure
+	 * VQs aren't running.
+	 */
+	for (i = 0; i < dev->nvqs; ++i)
+		dev->vqs[i]->memory = memory;
+}
+EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
+
+void vhost_dev_stop(struct vhost_dev *dev)
+{
+	int i;
+
+	for (i = 0; i < dev->nvqs; ++i) {
+		if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
+			vhost_poll_stop(&dev->vqs[i]->poll);
+			vhost_poll_flush(&dev->vqs[i]->poll);
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(vhost_dev_stop);
+
+/* Caller should have device mutex if and only if locked is set */
+void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
+{
+	int i;
+
+	for (i = 0; i < dev->nvqs; ++i) {
+		if (dev->vqs[i]->error_ctx)
+			eventfd_ctx_put(dev->vqs[i]->error_ctx);
+		if (dev->vqs[i]->error)
+			fput(dev->vqs[i]->error);
+		if (dev->vqs[i]->kick)
+			fput(dev->vqs[i]->kick);
+		if (dev->vqs[i]->call_ctx)
+			eventfd_ctx_put(dev->vqs[i]->call_ctx);
+		if (dev->vqs[i]->call)
+			fput(dev->vqs[i]->call);
+		vhost_vq_reset(dev, dev->vqs[i]);
+	}
+	vhost_dev_free_iovecs(dev);
+	if (dev->log_ctx)
+		eventfd_ctx_put(dev->log_ctx);
+	dev->log_ctx = NULL;
+	if (dev->log_file)
+		fput(dev->log_file);
+	dev->log_file = NULL;
+	/* No one will access memory at this point */
+	kfree(dev->memory);
+	dev->memory = NULL;
+	WARN_ON(!list_empty(&dev->work_list));
+	if (dev->worker) {
+		kthread_stop(dev->worker);
+		dev->worker = NULL;
+	}
+	if (dev->mm)
+		mmput(dev->mm);
+	dev->mm = NULL;
+}
+EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
+
+static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
+{
+	u64 a = addr / VHOST_PAGE_SIZE / 8;
+
+	/* Make sure 64 bit math will not overflow. */
+	if (a > ULONG_MAX - (unsigned long)log_base ||
+	    a + (unsigned long)log_base > ULONG_MAX)
+		return 0;
+
+	return access_ok(VERIFY_WRITE, log_base + a,
+			 (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
+}
+
+/* Caller should have vq mutex and device mutex. */
+static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
+			       int log_all)
+{
+	int i;
+
+	if (!mem)
+		return 0;
+
+	for (i = 0; i < mem->nregions; ++i) {
+		struct vhost_memory_region *m = mem->regions + i;
+		unsigned long a = m->userspace_addr;
+		if (m->memory_size > ULONG_MAX)
+			return 0;
+		else if (!access_ok(VERIFY_WRITE, (void __user *)a,
+				    m->memory_size))
+			return 0;
+		else if (log_all && !log_access_ok(log_base,
+						   m->guest_phys_addr,
+						   m->memory_size))
+			return 0;
+	}
+	return 1;
+}
+
+/* Can we switch to this memory table? */
+/* Caller should have device mutex but not vq mutex */
+static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
+			    int log_all)
+{
+	int i;
+
+	for (i = 0; i < d->nvqs; ++i) {
+		int ok;
+		bool log;
+
+		mutex_lock(&d->vqs[i]->mutex);
+		log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
+		/* If ring is inactive, will check when it's enabled. */
+		if (d->vqs[i]->private_data)
+			ok = vq_memory_access_ok(d->vqs[i]->log_base, mem, log);
+		else
+			ok = 1;
+		mutex_unlock(&d->vqs[i]->mutex);
+		if (!ok)
+			return 0;
+	}
+	return 1;
+}
+
+static int vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
+			struct vring_desc __user *desc,
+			struct vring_avail __user *avail,
+			struct vring_used __user *used)
+{
+	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
+	return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
+	       access_ok(VERIFY_READ, avail,
+			 sizeof *avail + num * sizeof *avail->ring + s) &&
+	       access_ok(VERIFY_WRITE, used,
+			sizeof *used + num * sizeof *used->ring + s);
+}
+
+/* Can we log writes? */
+/* Caller should have device mutex but not vq mutex */
+int vhost_log_access_ok(struct vhost_dev *dev)
+{
+	return memory_access_ok(dev, dev->memory, 1);
+}
+EXPORT_SYMBOL_GPL(vhost_log_access_ok);
+
+/* Verify access for write logging. */
+/* Caller should have vq mutex and device mutex */
+static int vq_log_access_ok(struct vhost_virtqueue *vq,
+			    void __user *log_base)
+{
+	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
+
+	return vq_memory_access_ok(log_base, vq->memory,
+				   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
+		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
+					sizeof *vq->used +
+					vq->num * sizeof *vq->used->ring + s));
+}
+
+/* Can we start vq? */
+/* Caller should have vq mutex and device mutex */
+int vhost_vq_access_ok(struct vhost_virtqueue *vq)
+{
+	return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used) &&
+		vq_log_access_ok(vq, vq->log_base);
+}
+EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
+
+static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
+{
+	struct vhost_memory mem, *newmem, *oldmem;
+	unsigned long size = offsetof(struct vhost_memory, regions);
+	int i;
+
+	if (copy_from_user(&mem, m, size))
+		return -EFAULT;
+	if (mem.padding)
+		return -EOPNOTSUPP;
+	if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
+		return -E2BIG;
+	newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
+	if (!newmem)
+		return -ENOMEM;
+
+	memcpy(newmem, &mem, size);
+	if (copy_from_user(newmem->regions, m->regions,
+			   mem.nregions * sizeof *m->regions)) {
+		kfree(newmem);
+		return -EFAULT;
+	}
+
+	if (!memory_access_ok(d, newmem, 0)) {
+		kfree(newmem);
+		return -EFAULT;
+	}
+	oldmem = d->memory;
+	d->memory = newmem;
+
+	/* All memory accesses are done under some VQ mutex. */
+	for (i = 0; i < d->nvqs; ++i) {
+		mutex_lock(&d->vqs[i]->mutex);
+		d->vqs[i]->memory = newmem;
+		mutex_unlock(&d->vqs[i]->mutex);
+	}
+	kfree(oldmem);
+	return 0;
+}
+
+long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
+{
+	struct file *eventfp, *filep = NULL;
+	bool pollstart = false, pollstop = false;
+	struct eventfd_ctx *ctx = NULL;
+	u32 __user *idxp = argp;
+	struct vhost_virtqueue *vq;
+	struct vhost_vring_state s;
+	struct vhost_vring_file f;
+	struct vhost_vring_addr a;
+	u32 idx;
+	long r;
+
+	r = get_user(idx, idxp);
+	if (r < 0)
+		return r;
+	if (idx >= d->nvqs)
+		return -ENOBUFS;
+
+	vq = d->vqs[idx];
+
+	mutex_lock(&vq->mutex);
+
+	switch (ioctl) {
+	case VHOST_SET_VRING_NUM:
+		/* Resizing ring with an active backend?
+		 * You don't want to do that. */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof s)) {
+			r = -EFAULT;
+			break;
+		}
+		if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
+			r = -EINVAL;
+			break;
+		}
+		vq->num = s.num;
+		break;
+	case VHOST_SET_VRING_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that. */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof s)) {
+			r = -EFAULT;
+			break;
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
+		vq->last_avail_idx = s.num;
+		/* Forget the cached index value. */
+		vq->avail_idx = vq->last_avail_idx;
+		break;
+	case VHOST_GET_VRING_BASE:
+		s.index = idx;
+		s.num = vq->last_avail_idx;
+		if (copy_to_user(argp, &s, sizeof s))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_ADDR:
+		if (copy_from_user(&a, argp, sizeof a)) {
+			r = -EFAULT;
+			break;
+		}
+		if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
+			r = -EOPNOTSUPP;
+			break;
+		}
+		/* For 32bit, verify that the top 32bits of the user
+		   data are set to zero. */
+		if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
+		    (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
+		    (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
+			r = -EFAULT;
+			break;
+		}
+
+		/* Make sure it's safe to cast pointers to vring types. */
+		BUILD_BUG_ON(__alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE);
+		BUILD_BUG_ON(__alignof__ *vq->used > VRING_USED_ALIGN_SIZE);
+		if ((a.avail_user_addr & (VRING_AVAIL_ALIGN_SIZE - 1)) ||
+		    (a.used_user_addr & (VRING_USED_ALIGN_SIZE - 1)) ||
+		    (a.log_guest_addr & (sizeof(u64) - 1))) {
+			r = -EINVAL;
+			break;
+		}
+
+		/* We only verify access here if backend is configured.
+		 * If it is not, we don't as size might not have been setup.
+		 * We will verify when backend is configured. */
+		if (vq->private_data) {
+			if (!vq_access_ok(vq, vq->num,
+				(void __user *)(unsigned long)a.desc_user_addr,
+				(void __user *)(unsigned long)a.avail_user_addr,
+				(void __user *)(unsigned long)a.used_user_addr)) {
+				r = -EINVAL;
+				break;
+			}
+
+			/* Also validate log access for used ring if enabled. */
+			if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
+			    !log_access_ok(vq->log_base, a.log_guest_addr,
+					   sizeof *vq->used +
+					   vq->num * sizeof *vq->used->ring)) {
+				r = -EINVAL;
+				break;
+			}
+		}
+
+		vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
+		vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
+		vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
+		vq->log_addr = a.log_guest_addr;
+		vq->used = (void __user *)(unsigned long)a.used_user_addr;
+		break;
+	case VHOST_SET_VRING_KICK:
+		if (copy_from_user(&f, argp, sizeof f)) {
+			r = -EFAULT;
+			break;
+		}
+		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
+		if (IS_ERR(eventfp)) {
+			r = PTR_ERR(eventfp);
+			break;
+		}
+		if (eventfp != vq->kick) {
+			pollstop = (filep = vq->kick) != NULL;
+			pollstart = (vq->kick = eventfp) != NULL;
+		} else
+			filep = eventfp;
+		break;
+	case VHOST_SET_VRING_CALL:
+		if (copy_from_user(&f, argp, sizeof f)) {
+			r = -EFAULT;
+			break;
+		}
+		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
+		if (IS_ERR(eventfp)) {
+			r = PTR_ERR(eventfp);
+			break;
+		}
+		if (eventfp != vq->call) {
+			filep = vq->call;
+			ctx = vq->call_ctx;
+			vq->call = eventfp;
+			vq->call_ctx = eventfp ?
+				eventfd_ctx_fileget(eventfp) : NULL;
+		} else
+			filep = eventfp;
+		break;
+	case VHOST_SET_VRING_ERR:
+		if (copy_from_user(&f, argp, sizeof f)) {
+			r = -EFAULT;
+			break;
+		}
+		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
+		if (IS_ERR(eventfp)) {
+			r = PTR_ERR(eventfp);
+			break;
+		}
+		if (eventfp != vq->error) {
+			filep = vq->error;
+			vq->error = eventfp;
+			ctx = vq->error_ctx;
+			vq->error_ctx = eventfp ?
+				eventfd_ctx_fileget(eventfp) : NULL;
+		} else
+			filep = eventfp;
+		break;
+	default:
+		r = -ENOIOCTLCMD;
+	}
+
+	if (pollstop && vq->handle_kick)
+		vhost_poll_stop(&vq->poll);
+
+	if (ctx)
+		eventfd_ctx_put(ctx);
+	if (filep)
+		fput(filep);
+
+	if (pollstart && vq->handle_kick)
+		r = vhost_poll_start(&vq->poll, vq->kick);
+
+	mutex_unlock(&vq->mutex);
+
+	if (pollstop && vq->handle_kick)
+		vhost_poll_flush(&vq->poll);
+	return r;
+}
+EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
+
+/* Caller must have device mutex */
+long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
+{
+	struct file *eventfp, *filep = NULL;
+	struct eventfd_ctx *ctx = NULL;
+	u64 p;
+	long r;
+	int i, fd;
+
+	/* If you are not the owner, you can become one */
+	if (ioctl == VHOST_SET_OWNER) {
+		r = vhost_dev_set_owner(d);
+		goto done;
+	}
+
+	/* You must be the owner to do anything else */
+	r = vhost_dev_check_owner(d);
+	if (r)
+		goto done;
+
+	switch (ioctl) {
+	case VHOST_SET_MEM_TABLE:
+		r = vhost_set_memory(d, argp);
+		break;
+	case VHOST_SET_LOG_BASE:
+		if (copy_from_user(&p, argp, sizeof p)) {
+			r = -EFAULT;
+			break;
+		}
+		if ((u64)(unsigned long)p != p) {
+			r = -EFAULT;
+			break;
+		}
+		for (i = 0; i < d->nvqs; ++i) {
+			struct vhost_virtqueue *vq;
+			void __user *base = (void __user *)(unsigned long)p;
+			vq = d->vqs[i];
+			mutex_lock(&vq->mutex);
+			/* If ring is inactive, will check when it's enabled. */
+			if (vq->private_data && !vq_log_access_ok(vq, base))
+				r = -EFAULT;
+			else
+				vq->log_base = base;
+			mutex_unlock(&vq->mutex);
+		}
+		break;
+	case VHOST_SET_LOG_FD:
+		r = get_user(fd, (int __user *)argp);
+		if (r < 0)
+			break;
+		eventfp = fd == -1 ? NULL : eventfd_fget(fd);
+		if (IS_ERR(eventfp)) {
+			r = PTR_ERR(eventfp);
+			break;
+		}
+		if (eventfp != d->log_file) {
+			filep = d->log_file;
+			ctx = d->log_ctx;
+			d->log_ctx = eventfp ?
+				eventfd_ctx_fileget(eventfp) : NULL;
+		} else
+			filep = eventfp;
+		for (i = 0; i < d->nvqs; ++i) {
+			mutex_lock(&d->vqs[i]->mutex);
+			d->vqs[i]->log_ctx = d->log_ctx;
+			mutex_unlock(&d->vqs[i]->mutex);
+		}
+		if (ctx)
+			eventfd_ctx_put(ctx);
+		if (filep)
+			fput(filep);
+		break;
+	default:
+		r = -ENOIOCTLCMD;
+		break;
+	}
+done:
+	return r;
+}
+EXPORT_SYMBOL_GPL(vhost_dev_ioctl);
+
+static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
+						     __u64 addr, __u32 len)
+{
+	struct vhost_memory_region *reg;
+	int i;
+
+	/* linear search is not brilliant, but we really have on the order of 6
+	 * regions in practice */
+	for (i = 0; i < mem->nregions; ++i) {
+		reg = mem->regions + i;
+		if (reg->guest_phys_addr <= addr &&
+		    reg->guest_phys_addr + reg->memory_size - 1 >= addr)
+			return reg;
+	}
+	return NULL;
+}
+
+/* TODO: This is really inefficient.  We need something like get_user()
+ * (instruction directly accesses the data, with an exception table entry
+ * returning -EFAULT). See Documentation/x86/exception-tables.txt.
+ */
+static int set_bit_to_user(int nr, void __user *addr)
+{
+	unsigned long log = (unsigned long)addr;
+	struct page *page;
+	void *base;
+	int bit = nr + (log % PAGE_SIZE) * 8;
+	int r;
+
+	r = get_user_pages_fast(log, 1, 1, &page);
+	if (r < 0)
+		return r;
+	BUG_ON(r != 1);
+	base = kmap_atomic(page);
+	set_bit(bit, base);
+	kunmap_atomic(base);
+	set_page_dirty_lock(page);
+	put_page(page);
+	return 0;
+}
+
+static int log_write(void __user *log_base,
+		     u64 write_address, u64 write_length)
+{
+	u64 write_page = write_address / VHOST_PAGE_SIZE;
+	int r;
+
+	if (!write_length)
+		return 0;
+	write_length += write_address % VHOST_PAGE_SIZE;
+	for (;;) {
+		u64 base = (u64)(unsigned long)log_base;
+		u64 log = base + write_page / 8;
+		int bit = write_page % 8;
+		if ((u64)(unsigned long)log != log)
+			return -EFAULT;
+		r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
+		if (r < 0)
+			return r;
+		if (write_length <= VHOST_PAGE_SIZE)
+			break;
+		write_length -= VHOST_PAGE_SIZE;
+		write_page += 1;
+	}
+	return r;
+}
+
+int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
+		    unsigned int log_num, u64 len)
+{
+	int i, r;
+
+	/* Make sure data written is seen before log. */
+	smp_wmb();
+	for (i = 0; i < log_num; ++i) {
+		u64 l = min(log[i].len, len);
+		r = log_write(vq->log_base, log[i].addr, l);
+		if (r < 0)
+			return r;
+		len -= l;
+		if (!len) {
+			if (vq->log_ctx)
+				eventfd_signal(vq->log_ctx, 1);
+			return 0;
+		}
+	}
+	/* Length written exceeds what we have stored. This is a bug. */
+	BUG();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vhost_log_write);
+
+static int vhost_update_used_flags(struct vhost_virtqueue *vq)
+{
+	void __user *used;
+	if (__put_user(cpu_to_vhost16(vq, vq->used_flags), &vq->used->flags) < 0)
+		return -EFAULT;
+	if (unlikely(vq->log_used)) {
+		/* Make sure the flag is seen before log. */
+		smp_wmb();
+		/* Log used flag write. */
+		used = &vq->used->flags;
+		log_write(vq->log_base, vq->log_addr +
+			  (used - (void __user *)vq->used),
+			  sizeof vq->used->flags);
+		if (vq->log_ctx)
+			eventfd_signal(vq->log_ctx, 1);
+	}
+	return 0;
+}
+
+static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
+{
+	if (__put_user(cpu_to_vhost16(vq, vq->avail_idx), vhost_avail_event(vq)))
+		return -EFAULT;
+	if (unlikely(vq->log_used)) {
+		void __user *used;
+		/* Make sure the event is seen before log. */
+		smp_wmb();
+		/* Log avail event write */
+		used = vhost_avail_event(vq);
+		log_write(vq->log_base, vq->log_addr +
+			  (used - (void __user *)vq->used),
+			  sizeof *vhost_avail_event(vq));
+		if (vq->log_ctx)
+			eventfd_signal(vq->log_ctx, 1);
+	}
+	return 0;
+}
+
+int vhost_init_used(struct vhost_virtqueue *vq)
+{
+	__virtio16 last_used_idx;
+	int r;
+	if (!vq->private_data)
+		return 0;
+
+	r = vhost_update_used_flags(vq);
+	if (r)
+		return r;
+	vq->signalled_used_valid = false;
+	if (!access_ok(VERIFY_READ, &vq->used->idx, sizeof vq->used->idx))
+		return -EFAULT;
+	r = __get_user(last_used_idx, &vq->used->idx);
+	if (r)
+		return r;
+	vq->last_used_idx = vhost16_to_cpu(vq, last_used_idx);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vhost_init_used);
+
+static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
+			  struct iovec iov[], int iov_size)
+{
+	const struct vhost_memory_region *reg;
+	struct vhost_memory *mem;
+	struct iovec *_iov;
+	u64 s = 0;
+	int ret = 0;
+
+	mem = vq->memory;
+	while ((u64)len > s) {
+		u64 size;
+		if (unlikely(ret >= iov_size)) {
+			ret = -ENOBUFS;
+			break;
+		}
+		reg = find_region(mem, addr, len);
+		if (unlikely(!reg)) {
+			ret = -EFAULT;
+			break;
+		}
+		_iov = iov + ret;
+		size = reg->memory_size - addr + reg->guest_phys_addr;
+		_iov->iov_len = min((u64)len - s, size);
+		_iov->iov_base = (void __user *)(unsigned long)
+			(reg->userspace_addr + addr - reg->guest_phys_addr);
+		s += size;
+		addr += size;
+		++ret;
+	}
+
+	return ret;
+}
+
+/* Each buffer in the virtqueues is actually a chain of descriptors.  This
+ * function returns the next descriptor in the chain,
+ * or -1U if we're at the end. */
+static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc)
+{
+	unsigned int next;
+
+	/* If this descriptor says it doesn't chain, we're done. */
+	if (!(desc->flags & cpu_to_vhost16(vq, VRING_DESC_F_NEXT)))
+		return -1U;
+
+	/* Check they're not leading us off end of descriptors. */
+	next = vhost16_to_cpu(vq, desc->next);
+	/* Make sure compiler knows to grab that: we don't want it changing! */
+	/* We will use the result as an index in an array, so most
+	 * architectures only need a compiler barrier here. */
+	read_barrier_depends();
+
+	return next;
+}
+
+static int get_indirect(struct vhost_virtqueue *vq,
+			struct iovec iov[], unsigned int iov_size,
+			unsigned int *out_num, unsigned int *in_num,
+			struct vhost_log *log, unsigned int *log_num,
+			struct vring_desc *indirect)
+{
+	struct vring_desc desc;
+	unsigned int i = 0, count, found = 0;
+	u32 len = vhost32_to_cpu(vq, indirect->len);
+	struct iov_iter from;
+	int ret;
+
+	/* Sanity check */
+	if (unlikely(len % sizeof desc)) {
+		vq_err(vq, "Invalid length in indirect descriptor: "
+		       "len 0x%llx not multiple of 0x%zx\n",
+		       (unsigned long long)len,
+		       sizeof desc);
+		return -EINVAL;
+	}
+
+	ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len, vq->indirect,
+			     UIO_MAXIOV);
+	if (unlikely(ret < 0)) {
+		vq_err(vq, "Translation failure %d in indirect.\n", ret);
+		return ret;
+	}
+	iov_iter_init(&from, READ, vq->indirect, ret, len);
+
+	/* We will use the result as an address to read from, so most
+	 * architectures only need a compiler barrier here. */
+	read_barrier_depends();
+
+	count = len / sizeof desc;
+	/* Buffers are chained via a 16 bit next field, so
+	 * we can have at most 2^16 of these. */
+	if (unlikely(count > USHRT_MAX + 1)) {
+		vq_err(vq, "Indirect buffer length too big: %d\n",
+		       indirect->len);
+		return -E2BIG;
+	}
+
+	do {
+		unsigned iov_count = *in_num + *out_num;
+		if (unlikely(++found > count)) {
+			vq_err(vq, "Loop detected: last one at %u "
+			       "indirect size %u\n",
+			       i, count);
+			return -EINVAL;
+		}
+		if (unlikely(copy_from_iter(&desc, sizeof(desc), &from) !=
+			     sizeof(desc))) {
+			vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
+			       i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
+			return -EINVAL;
+		}
+		if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) {
+			vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
+			       i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
+			return -EINVAL;
+		}
+
+		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
+				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
+				     iov_size - iov_count);
+		if (unlikely(ret < 0)) {
+			vq_err(vq, "Translation failure %d indirect idx %d\n",
+			       ret, i);
+			return ret;
+		}
+		/* If this is an input descriptor, increment that count. */
+		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) {
+			*in_num += ret;
+			if (unlikely(log)) {
+				log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
+				log[*log_num].len = vhost32_to_cpu(vq, desc.len);
+				++*log_num;
+			}
+		} else {
+			/* If it's an output descriptor, they're all supposed
+			 * to come before any input descriptors. */
+			if (unlikely(*in_num)) {
+				vq_err(vq, "Indirect descriptor "
+				       "has out after in: idx %d\n", i);
+				return -EINVAL;
+			}
+			*out_num += ret;
+		}
+	} while ((i = next_desc(vq, &desc)) != -1);
+	return 0;
+}
+
+/* This looks in the virtqueue and for the first available buffer, and converts
+ * it to an iovec for convenient access.  Since descriptors consist of some
+ * number of output then some number of input descriptors, it's actually two
+ * iovecs, but we pack them into one and note how many of each there were.
+ *
+ * This function returns the descriptor number found, or vq->num (which is
+ * never a valid descriptor number) if none was found.  A negative code is
+ * returned on error. */
+int vhost_get_vq_desc(struct vhost_virtqueue *vq,
+		      struct iovec iov[], unsigned int iov_size,
+		      unsigned int *out_num, unsigned int *in_num,
+		      struct vhost_log *log, unsigned int *log_num)
+{
+	struct vring_desc desc;
+	unsigned int i, head, found = 0;
+	u16 last_avail_idx;
+	__virtio16 avail_idx;
+	__virtio16 ring_head;
+	int ret;
+
+	/* Check it isn't doing very strange things with descriptor numbers. */
+	last_avail_idx = vq->last_avail_idx;
+	if (unlikely(__get_user(avail_idx, &vq->avail->idx))) {
+		vq_err(vq, "Failed to access avail idx at %p\n",
+		       &vq->avail->idx);
+		return -EFAULT;
+	}
+	vq->avail_idx = vhost16_to_cpu(vq, avail_idx);
+
+	if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
+		vq_err(vq, "Guest moved used index from %u to %u",
+		       last_avail_idx, vq->avail_idx);
+		return -EFAULT;
+	}
+
+	/* If there's nothing new since last we looked, return invalid. */
+	if (vq->avail_idx == last_avail_idx)
+		return vq->num;
+
+	/* Only get avail ring entries after they have been exposed by guest. */
+	smp_rmb();
+
+	/* Grab the next descriptor number they're advertising, and increment
+	 * the index we've seen. */
+	if (unlikely(__get_user(ring_head,
+				&vq->avail->ring[last_avail_idx % vq->num]))) {
+		vq_err(vq, "Failed to read head: idx %d address %p\n",
+		       last_avail_idx,
+		       &vq->avail->ring[last_avail_idx % vq->num]);
+		return -EFAULT;
+	}
+
+	head = vhost16_to_cpu(vq, ring_head);
+
+	/* If their number is silly, that's an error. */
+	if (unlikely(head >= vq->num)) {
+		vq_err(vq, "Guest says index %u > %u is available",
+		       head, vq->num);
+		return -EINVAL;
+	}
+
+	/* When we start there are none of either input nor output. */
+	*out_num = *in_num = 0;
+	if (unlikely(log))
+		*log_num = 0;
+
+	i = head;
+	do {
+		unsigned iov_count = *in_num + *out_num;
+		if (unlikely(i >= vq->num)) {
+			vq_err(vq, "Desc index is %u > %u, head = %u",
+			       i, vq->num, head);
+			return -EINVAL;
+		}
+		if (unlikely(++found > vq->num)) {
+			vq_err(vq, "Loop detected: last one at %u "
+			       "vq size %u head %u\n",
+			       i, vq->num, head);
+			return -EINVAL;
+		}
+		ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
+		if (unlikely(ret)) {
+			vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
+			       i, vq->desc + i);
+			return -EFAULT;
+		}
+		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
+			ret = get_indirect(vq, iov, iov_size,
+					   out_num, in_num,
+					   log, log_num, &desc);
+			if (unlikely(ret < 0)) {
+				vq_err(vq, "Failure detected "
+				       "in indirect descriptor at idx %d\n", i);
+				return ret;
+			}
+			continue;
+		}
+
+		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
+				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
+				     iov_size - iov_count);
+		if (unlikely(ret < 0)) {
+			vq_err(vq, "Translation failure %d descriptor idx %d\n",
+			       ret, i);
+			return ret;
+		}
+		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) {
+			/* If this is an input descriptor,
+			 * increment that count. */
+			*in_num += ret;
+			if (unlikely(log)) {
+				log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
+				log[*log_num].len = vhost32_to_cpu(vq, desc.len);
+				++*log_num;
+			}
+		} else {
+			/* If it's an output descriptor, they're all supposed
+			 * to come before any input descriptors. */
+			if (unlikely(*in_num)) {
+				vq_err(vq, "Descriptor has out after in: "
+				       "idx %d\n", i);
+				return -EINVAL;
+			}
+			*out_num += ret;
+		}
+	} while ((i = next_desc(vq, &desc)) != -1);
+
+	/* On success, increment avail index. */
+	vq->last_avail_idx++;
+
+	/* Assume notifications from guest are disabled at this point,
+	 * if they aren't we would need to update avail_event index. */
+	BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
+	return head;
+}
+EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
+
+/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
+void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
+{
+	vq->last_avail_idx -= n;
+}
+EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
+
+/* After we've used one of their buffers, we tell them about it.  We'll then
+ * want to notify the guest, using eventfd. */
+int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
+{
+	struct vring_used_elem heads = {
+		cpu_to_vhost32(vq, head),
+		cpu_to_vhost32(vq, len)
+	};
+
+	return vhost_add_used_n(vq, &heads, 1);
+}
+EXPORT_SYMBOL_GPL(vhost_add_used);
+
+static int __vhost_add_used_n(struct vhost_virtqueue *vq,
+			    struct vring_used_elem *heads,
+			    unsigned count)
+{
+	struct vring_used_elem __user *used;
+	u16 old, new;
+	int start;
+
+	start = vq->last_used_idx % vq->num;
+	used = vq->used->ring + start;
+	if (count == 1) {
+		if (__put_user(heads[0].id, &used->id)) {
+			vq_err(vq, "Failed to write used id");
+			return -EFAULT;
+		}
+		if (__put_user(heads[0].len, &used->len)) {
+			vq_err(vq, "Failed to write used len");
+			return -EFAULT;
+		}
+	} else if (__copy_to_user(used, heads, count * sizeof *used)) {
+		vq_err(vq, "Failed to write used");
+		return -EFAULT;
+	}
+	if (unlikely(vq->log_used)) {
+		/* Make sure data is seen before log. */
+		smp_wmb();
+		/* Log used ring entry write. */
+		log_write(vq->log_base,
+			  vq->log_addr +
+			   ((void __user *)used - (void __user *)vq->used),
+			  count * sizeof *used);
+	}
+	old = vq->last_used_idx;
+	new = (vq->last_used_idx += count);
+	/* If the driver never bothers to signal in a very long while,
+	 * used index might wrap around. If that happens, invalidate
+	 * signalled_used index we stored. TODO: make sure driver
+	 * signals at least once in 2^16 and remove this. */
+	if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
+		vq->signalled_used_valid = false;
+	return 0;
+}
+
+/* After we've used one of their buffers, we tell them about it.  We'll then
+ * want to notify the guest, using eventfd. */
+int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
+		     unsigned count)
+{
+	int start, n, r;
+
+	start = vq->last_used_idx % vq->num;
+	n = vq->num - start;
+	if (n < count) {
+		r = __vhost_add_used_n(vq, heads, n);
+		if (r < 0)
+			return r;
+		heads += n;
+		count -= n;
+	}
+	r = __vhost_add_used_n(vq, heads, count);
+
+	/* Make sure buffer is written before we update index. */
+	smp_wmb();
+	if (__put_user(cpu_to_vhost16(vq, vq->last_used_idx), &vq->used->idx)) {
+		vq_err(vq, "Failed to increment used idx");
+		return -EFAULT;
+	}
+	if (unlikely(vq->log_used)) {
+		/* Log used index update. */
+		log_write(vq->log_base,
+			  vq->log_addr + offsetof(struct vring_used, idx),
+			  sizeof vq->used->idx);
+		if (vq->log_ctx)
+			eventfd_signal(vq->log_ctx, 1);
+	}
+	return r;
+}
+EXPORT_SYMBOL_GPL(vhost_add_used_n);
+
+static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	__u16 old, new;
+	__virtio16 event;
+	bool v;
+	/* Flush out used index updates. This is paired
+	 * with the barrier that the Guest executes when enabling
+	 * interrupts. */
+	smp_mb();
+
+	if (vhost_has_feature(vq, VIRTIO_F_NOTIFY_ON_EMPTY) &&
+	    unlikely(vq->avail_idx == vq->last_avail_idx))
+		return true;
+
+	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
+		__virtio16 flags;
+		if (__get_user(flags, &vq->avail->flags)) {
+			vq_err(vq, "Failed to get flags");
+			return true;
+		}
+		return !(flags & cpu_to_vhost16(vq, VRING_AVAIL_F_NO_INTERRUPT));
+	}
+	old = vq->signalled_used;
+	v = vq->signalled_used_valid;
+	new = vq->signalled_used = vq->last_used_idx;
+	vq->signalled_used_valid = true;
+
+	if (unlikely(!v))
+		return true;
+
+	if (__get_user(event, vhost_used_event(vq))) {
+		vq_err(vq, "Failed to get used event idx");
+		return true;
+	}
+	return vring_need_event(vhost16_to_cpu(vq, event), new, old);
+}
+
+/* This actually signals the guest, using eventfd. */
+void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	/* Signal the Guest tell them we used something up. */
+	if (vq->call_ctx && vhost_notify(dev, vq))
+		eventfd_signal(vq->call_ctx, 1);
+}
+EXPORT_SYMBOL_GPL(vhost_signal);
+
+/* And here's the combo meal deal.  Supersize me! */
+void vhost_add_used_and_signal(struct vhost_dev *dev,
+			       struct vhost_virtqueue *vq,
+			       unsigned int head, int len)
+{
+	vhost_add_used(vq, head, len);
+	vhost_signal(dev, vq);
+}
+EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
+
+/* multi-buffer version of vhost_add_used_and_signal */
+void vhost_add_used_and_signal_n(struct vhost_dev *dev,
+				 struct vhost_virtqueue *vq,
+				 struct vring_used_elem *heads, unsigned count)
+{
+	vhost_add_used_n(vq, heads, count);
+	vhost_signal(dev, vq);
+}
+EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
+
+/* OK, now we need to know about added descriptors. */
+bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	__virtio16 avail_idx;
+	int r;
+
+	if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
+		return false;
+	vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
+	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
+		r = vhost_update_used_flags(vq);
+		if (r) {
+			vq_err(vq, "Failed to enable notification at %p: %d\n",
+			       &vq->used->flags, r);
+			return false;
+		}
+	} else {
+		r = vhost_update_avail_event(vq, vq->avail_idx);
+		if (r) {
+			vq_err(vq, "Failed to update avail event index at %p: %d\n",
+			       vhost_avail_event(vq), r);
+			return false;
+		}
+	}
+	/* They could have slipped one in as we were doing that: make
+	 * sure it's written, then check again. */
+	smp_mb();
+	r = __get_user(avail_idx, &vq->avail->idx);
+	if (r) {
+		vq_err(vq, "Failed to check avail idx at %p: %d\n",
+		       &vq->avail->idx, r);
+		return false;
+	}
+
+	return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx;
+}
+EXPORT_SYMBOL_GPL(vhost_enable_notify);
+
+/* We don't need to be notified again. */
+void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	int r;
+
+	if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
+		return;
+	vq->used_flags |= VRING_USED_F_NO_NOTIFY;
+	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
+		r = vhost_update_used_flags(vq);
+		if (r)
+			vq_err(vq, "Failed to enable notification at %p: %d\n",
+			       &vq->used->flags, r);
+	}
+}
+EXPORT_SYMBOL_GPL(vhost_disable_notify);
+
+static int __init vhost_init(void)
+{
+	return 0;
+}
+
+static void __exit vhost_exit(void)
+{
+}
+
+module_init(vhost_init);
+module_exit(vhost_exit);
+
+MODULE_VERSION("0.0.1");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Michael S. Tsirkin");
+MODULE_DESCRIPTION("Host kernel accelerator for virtio");
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
new file mode 100644
index 000000000..8c1c79290
--- /dev/null
+++ b/drivers/vhost/vhost.h
@@ -0,0 +1,206 @@
+#ifndef _VHOST_H
+#define _VHOST_H
+
+#include <linux/eventfd.h>
+#include <linux/vhost.h>
+#include <linux/mm.h>
+#include <linux/mutex.h>
+#include <linux/poll.h>
+#include <linux/file.h>
+#include <linux/uio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ring.h>
+#include <linux/atomic.h>
+
+struct vhost_work;
+typedef void (*vhost_work_fn_t)(struct vhost_work *work);
+
+struct vhost_work {
+	struct list_head	  node;
+	vhost_work_fn_t		  fn;
+	wait_queue_head_t	  done;
+	int			  flushing;
+	unsigned		  queue_seq;
+	unsigned		  done_seq;
+};
+
+/* Poll a file (eventfd or socket) */
+/* Note: there's nothing vhost specific about this structure. */
+struct vhost_poll {
+	poll_table                table;
+	wait_queue_head_t        *wqh;
+	wait_queue_t              wait;
+	struct vhost_work	  work;
+	unsigned long		  mask;
+	struct vhost_dev	 *dev;
+};
+
+void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
+void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
+
+void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
+		     unsigned long mask, struct vhost_dev *dev);
+int vhost_poll_start(struct vhost_poll *poll, struct file *file);
+void vhost_poll_stop(struct vhost_poll *poll);
+void vhost_poll_flush(struct vhost_poll *poll);
+void vhost_poll_queue(struct vhost_poll *poll);
+void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work);
+long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp);
+
+struct vhost_log {
+	u64 addr;
+	u64 len;
+};
+
+/* The virtqueue structure describes a queue attached to a device. */
+struct vhost_virtqueue {
+	struct vhost_dev *dev;
+
+	/* The actual ring of buffers. */
+	struct mutex mutex;
+	unsigned int num;
+	struct vring_desc __user *desc;
+	struct vring_avail __user *avail;
+	struct vring_used __user *used;
+	struct file *kick;
+	struct file *call;
+	struct file *error;
+	struct eventfd_ctx *call_ctx;
+	struct eventfd_ctx *error_ctx;
+	struct eventfd_ctx *log_ctx;
+
+	struct vhost_poll poll;
+
+	/* The routine to call when the Guest pings us, or timeout. */
+	vhost_work_fn_t handle_kick;
+
+	/* Last available index we saw. */
+	u16 last_avail_idx;
+
+	/* Caches available index value from user. */
+	u16 avail_idx;
+
+	/* Last index we used. */
+	u16 last_used_idx;
+
+	/* Used flags */
+	u16 used_flags;
+
+	/* Last used index value we have signalled on */
+	u16 signalled_used;
+
+	/* Last used index value we have signalled on */
+	bool signalled_used_valid;
+
+	/* Log writes to used structure. */
+	bool log_used;
+	u64 log_addr;
+
+	struct iovec iov[UIO_MAXIOV];
+	struct iovec *indirect;
+	struct vring_used_elem *heads;
+	/* Protected by virtqueue mutex. */
+	struct vhost_memory *memory;
+	void *private_data;
+	u64 acked_features;
+	/* Log write descriptors */
+	void __user *log_base;
+	struct vhost_log *log;
+};
+
+struct vhost_dev {
+	struct vhost_memory *memory;
+	struct mm_struct *mm;
+	struct mutex mutex;
+	struct vhost_virtqueue **vqs;
+	int nvqs;
+	struct file *log_file;
+	struct eventfd_ctx *log_ctx;
+	spinlock_t work_lock;
+	struct list_head work_list;
+	struct task_struct *worker;
+};
+
+void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs, int nvqs);
+long vhost_dev_set_owner(struct vhost_dev *dev);
+bool vhost_dev_has_owner(struct vhost_dev *dev);
+long vhost_dev_check_owner(struct vhost_dev *);
+struct vhost_memory *vhost_dev_reset_owner_prepare(void);
+void vhost_dev_reset_owner(struct vhost_dev *, struct vhost_memory *);
+void vhost_dev_cleanup(struct vhost_dev *, bool locked);
+void vhost_dev_stop(struct vhost_dev *);
+long vhost_dev_ioctl(struct vhost_dev *, unsigned int ioctl, void __user *argp);
+long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp);
+int vhost_vq_access_ok(struct vhost_virtqueue *vq);
+int vhost_log_access_ok(struct vhost_dev *);
+
+int vhost_get_vq_desc(struct vhost_virtqueue *,
+		      struct iovec iov[], unsigned int iov_count,
+		      unsigned int *out_num, unsigned int *in_num,
+		      struct vhost_log *log, unsigned int *log_num);
+void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
+
+int vhost_init_used(struct vhost_virtqueue *);
+int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
+int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
+		     unsigned count);
+void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
+			       unsigned int id, int len);
+void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
+			       struct vring_used_elem *heads, unsigned count);
+void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
+void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *);
+bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
+
+int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
+		    unsigned int log_num, u64 len);
+
+#define vq_err(vq, fmt, ...) do {                                  \
+		pr_debug(pr_fmt(fmt), ##__VA_ARGS__);       \
+		if ((vq)->error_ctx)                               \
+				eventfd_signal((vq)->error_ctx, 1);\
+	} while (0)
+
+enum {
+	VHOST_FEATURES = (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
+			 (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
+			 (1ULL << VIRTIO_RING_F_EVENT_IDX) |
+			 (1ULL << VHOST_F_LOG_ALL),
+};
+
+static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)
+{
+	return vq->acked_features & (1ULL << bit);
+}
+
+/* Memory accessors */
+static inline u16 vhost16_to_cpu(struct vhost_virtqueue *vq, __virtio16 val)
+{
+	return __virtio16_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+}
+
+static inline __virtio16 cpu_to_vhost16(struct vhost_virtqueue *vq, u16 val)
+{
+	return __cpu_to_virtio16(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+}
+
+static inline u32 vhost32_to_cpu(struct vhost_virtqueue *vq, __virtio32 val)
+{
+	return __virtio32_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+}
+
+static inline __virtio32 cpu_to_vhost32(struct vhost_virtqueue *vq, u32 val)
+{
+	return __cpu_to_virtio32(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+}
+
+static inline u64 vhost64_to_cpu(struct vhost_virtqueue *vq, __virtio64 val)
+{
+	return __virtio64_to_cpu(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+}
+
+static inline __virtio64 cpu_to_vhost64(struct vhost_virtqueue *vq, u64 val)
+{
+	return __cpu_to_virtio64(vhost_has_feature(vq, VIRTIO_F_VERSION_1), val);
+}
+#endif
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
new file mode 100644
index 000000000..3bb02c60a
--- /dev/null
+++ b/drivers/vhost/vringh.c
@@ -0,0 +1,1037 @@
+/*
+ * Helpers for the host side of a virtio ring.
+ *
+ * Since these may be in userspace, we use (inline) accessors.
+ */
+#include <linux/module.h>
+#include <linux/vringh.h>
+#include <linux/virtio_ring.h>
+#include <linux/kernel.h>
+#include <linux/ratelimit.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <uapi/linux/virtio_config.h>
+
+static __printf(1,2) __cold void vringh_bad(const char *fmt, ...)
+{
+	static DEFINE_RATELIMIT_STATE(vringh_rs,
+				      DEFAULT_RATELIMIT_INTERVAL,
+				      DEFAULT_RATELIMIT_BURST);
+	if (__ratelimit(&vringh_rs)) {
+		va_list ap;
+		va_start(ap, fmt);
+		printk(KERN_NOTICE "vringh:");
+		vprintk(fmt, ap);
+		va_end(ap);
+	}
+}
+
+/* Returns vring->num if empty, -ve on error. */
+static inline int __vringh_get_head(const struct vringh *vrh,
+				    int (*getu16)(const struct vringh *vrh,
+						  u16 *val, const __virtio16 *p),
+				    u16 *last_avail_idx)
+{
+	u16 avail_idx, i, head;
+	int err;
+
+	err = getu16(vrh, &avail_idx, &vrh->vring.avail->idx);
+	if (err) {
+		vringh_bad("Failed to access avail idx at %p",
+			   &vrh->vring.avail->idx);
+		return err;
+	}
+
+	if (*last_avail_idx == avail_idx)
+		return vrh->vring.num;
+
+	/* Only get avail ring entries after they have been exposed by guest. */
+	virtio_rmb(vrh->weak_barriers);
+
+	i = *last_avail_idx & (vrh->vring.num - 1);
+
+	err = getu16(vrh, &head, &vrh->vring.avail->ring[i]);
+	if (err) {
+		vringh_bad("Failed to read head: idx %d address %p",
+			   *last_avail_idx, &vrh->vring.avail->ring[i]);
+		return err;
+	}
+
+	if (head >= vrh->vring.num) {
+		vringh_bad("Guest says index %u > %u is available",
+			   head, vrh->vring.num);
+		return -EINVAL;
+	}
+
+	(*last_avail_idx)++;
+	return head;
+}
+
+/* Copy some bytes to/from the iovec.  Returns num copied. */
+static inline ssize_t vringh_iov_xfer(struct vringh_kiov *iov,
+				      void *ptr, size_t len,
+				      int (*xfer)(void *addr, void *ptr,
+						  size_t len))
+{
+	int err, done = 0;
+
+	while (len && iov->i < iov->used) {
+		size_t partlen;
+
+		partlen = min(iov->iov[iov->i].iov_len, len);
+		err = xfer(iov->iov[iov->i].iov_base, ptr, partlen);
+		if (err)
+			return err;
+		done += partlen;
+		len -= partlen;
+		ptr += partlen;
+		iov->consumed += partlen;
+		iov->iov[iov->i].iov_len -= partlen;
+		iov->iov[iov->i].iov_base += partlen;
+
+		if (!iov->iov[iov->i].iov_len) {
+			/* Fix up old iov element then increment. */
+			iov->iov[iov->i].iov_len = iov->consumed;
+			iov->iov[iov->i].iov_base -= iov->consumed;
+			
+			iov->consumed = 0;
+			iov->i++;
+		}
+	}
+	return done;
+}
+
+/* May reduce *len if range is shorter. */
+static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len,
+			       struct vringh_range *range,
+			       bool (*getrange)(struct vringh *,
+						u64, struct vringh_range *))
+{
+	if (addr < range->start || addr > range->end_incl) {
+		if (!getrange(vrh, addr, range))
+			return false;
+	}
+	BUG_ON(addr < range->start || addr > range->end_incl);
+
+	/* To end of memory? */
+	if (unlikely(addr + *len == 0)) {
+		if (range->end_incl == -1ULL)
+			return true;
+		goto truncate;
+	}
+
+	/* Otherwise, don't wrap. */
+	if (addr + *len < addr) {
+		vringh_bad("Wrapping descriptor %zu@0x%llx",
+			   *len, (unsigned long long)addr);
+		return false;
+	}
+
+	if (unlikely(addr + *len - 1 > range->end_incl))
+		goto truncate;
+	return true;
+
+truncate:
+	*len = range->end_incl + 1 - addr;
+	return true;
+}
+
+static inline bool no_range_check(struct vringh *vrh, u64 addr, size_t *len,
+				  struct vringh_range *range,
+				  bool (*getrange)(struct vringh *,
+						   u64, struct vringh_range *))
+{
+	return true;
+}
+
+/* No reason for this code to be inline. */
+static int move_to_indirect(const struct vringh *vrh,
+			    int *up_next, u16 *i, void *addr,
+			    const struct vring_desc *desc,
+			    struct vring_desc **descs, int *desc_max)
+{
+	u32 len;
+
+	/* Indirect tables can't have indirect. */
+	if (*up_next != -1) {
+		vringh_bad("Multilevel indirect %u->%u", *up_next, *i);
+		return -EINVAL;
+	}
+
+	len = vringh32_to_cpu(vrh, desc->len);
+	if (unlikely(len % sizeof(struct vring_desc))) {
+		vringh_bad("Strange indirect len %u", desc->len);
+		return -EINVAL;
+	}
+
+	/* We will check this when we follow it! */
+	if (desc->flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT))
+		*up_next = vringh16_to_cpu(vrh, desc->next);
+	else
+		*up_next = -2;
+	*descs = addr;
+	*desc_max = len / sizeof(struct vring_desc);
+
+	/* Now, start at the first indirect. */
+	*i = 0;
+	return 0;
+}
+
+static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
+{
+	struct kvec *new;
+	unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
+
+	if (new_num < 8)
+		new_num = 8;
+
+	flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
+	if (flag)
+		new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
+	else {
+		new = kmalloc(new_num * sizeof(struct iovec), gfp);
+		if (new) {
+			memcpy(new, iov->iov,
+			       iov->max_num * sizeof(struct iovec));
+			flag = VRINGH_IOV_ALLOCATED;
+		}
+	}
+	if (!new)
+		return -ENOMEM;
+	iov->iov = new;
+	iov->max_num = (new_num | flag);
+	return 0;
+}
+
+static u16 __cold return_from_indirect(const struct vringh *vrh, int *up_next,
+				       struct vring_desc **descs, int *desc_max)
+{
+	u16 i = *up_next;
+
+	*up_next = -1;
+	*descs = vrh->vring.desc;
+	*desc_max = vrh->vring.num;
+	return i;
+}
+
+static int slow_copy(struct vringh *vrh, void *dst, const void *src,
+		     bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
+				    struct vringh_range *range,
+				    bool (*getrange)(struct vringh *vrh,
+						     u64,
+						     struct vringh_range *)),
+		     bool (*getrange)(struct vringh *vrh,
+				      u64 addr,
+				      struct vringh_range *r),
+		     struct vringh_range *range,
+		     int (*copy)(void *dst, const void *src, size_t len))
+{
+	size_t part, len = sizeof(struct vring_desc);
+
+	do {
+		u64 addr;
+		int err;
+
+		part = len;
+		addr = (u64)(unsigned long)src - range->offset;
+
+		if (!rcheck(vrh, addr, &part, range, getrange))
+			return -EINVAL;
+
+		err = copy(dst, src, part);
+		if (err)
+			return err;
+
+		dst += part;
+		src += part;
+		len -= part;
+	} while (len);
+	return 0;
+}
+
+static inline int
+__vringh_iov(struct vringh *vrh, u16 i,
+	     struct vringh_kiov *riov,
+	     struct vringh_kiov *wiov,
+	     bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
+			    struct vringh_range *range,
+			    bool (*getrange)(struct vringh *, u64,
+					     struct vringh_range *)),
+	     bool (*getrange)(struct vringh *, u64, struct vringh_range *),
+	     gfp_t gfp,
+	     int (*copy)(void *dst, const void *src, size_t len))
+{
+	int err, count = 0, up_next, desc_max;
+	struct vring_desc desc, *descs;
+	struct vringh_range range = { -1ULL, 0 }, slowrange;
+	bool slow = false;
+
+	/* We start traversing vring's descriptor table. */
+	descs = vrh->vring.desc;
+	desc_max = vrh->vring.num;
+	up_next = -1;
+
+	if (riov)
+		riov->i = riov->used = 0;
+	else if (wiov)
+		wiov->i = wiov->used = 0;
+	else
+		/* You must want something! */
+		BUG();
+
+	for (;;) {
+		void *addr;
+		struct vringh_kiov *iov;
+		size_t len;
+
+		if (unlikely(slow))
+			err = slow_copy(vrh, &desc, &descs[i], rcheck, getrange,
+					&slowrange, copy);
+		else
+			err = copy(&desc, &descs[i], sizeof(desc));
+		if (unlikely(err))
+			goto fail;
+
+		if (unlikely(desc.flags &
+			     cpu_to_vringh16(vrh, VRING_DESC_F_INDIRECT))) {
+			u64 a = vringh64_to_cpu(vrh, desc.addr);
+
+			/* Make sure it's OK, and get offset. */
+			len = vringh32_to_cpu(vrh, desc.len);
+			if (!rcheck(vrh, a, &len, &range, getrange)) {
+				err = -EINVAL;
+				goto fail;
+			}
+
+			if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
+				slow = true;
+				/* We need to save this range to use offset */
+				slowrange = range;
+			}
+
+			addr = (void *)(long)(a + range.offset);
+			err = move_to_indirect(vrh, &up_next, &i, addr, &desc,
+					       &descs, &desc_max);
+			if (err)
+				goto fail;
+			continue;
+		}
+
+		if (count++ == vrh->vring.num) {
+			vringh_bad("Descriptor loop in %p", descs);
+			err = -ELOOP;
+			goto fail;
+		}
+
+		if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_WRITE))
+			iov = wiov;
+		else {
+			iov = riov;
+			if (unlikely(wiov && wiov->i)) {
+				vringh_bad("Readable desc %p after writable",
+					   &descs[i]);
+				err = -EINVAL;
+				goto fail;
+			}
+		}
+
+		if (!iov) {
+			vringh_bad("Unexpected %s desc",
+				   !wiov ? "writable" : "readable");
+			err = -EPROTO;
+			goto fail;
+		}
+
+	again:
+		/* Make sure it's OK, and get offset. */
+		len = vringh32_to_cpu(vrh, desc.len);
+		if (!rcheck(vrh, vringh64_to_cpu(vrh, desc.addr), &len, &range,
+			    getrange)) {
+			err = -EINVAL;
+			goto fail;
+		}
+		addr = (void *)(unsigned long)(vringh64_to_cpu(vrh, desc.addr) +
+					       range.offset);
+
+		if (unlikely(iov->used == (iov->max_num & ~VRINGH_IOV_ALLOCATED))) {
+			err = resize_iovec(iov, gfp);
+			if (err)
+				goto fail;
+		}
+
+		iov->iov[iov->used].iov_base = addr;
+		iov->iov[iov->used].iov_len = len;
+		iov->used++;
+
+		if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
+			desc.len = cpu_to_vringh32(vrh,
+				   vringh32_to_cpu(vrh, desc.len) - len);
+			desc.addr = cpu_to_vringh64(vrh,
+				    vringh64_to_cpu(vrh, desc.addr) + len);
+			goto again;
+		}
+
+		if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT)) {
+			i = vringh16_to_cpu(vrh, desc.next);
+		} else {
+			/* Just in case we need to finish traversing above. */
+			if (unlikely(up_next > 0)) {
+				i = return_from_indirect(vrh, &up_next,
+							 &descs, &desc_max);
+				slow = false;
+			} else
+				break;
+		}
+
+		if (i >= desc_max) {
+			vringh_bad("Chained index %u > %u", i, desc_max);
+			err = -EINVAL;
+			goto fail;
+		}
+	}
+
+	return 0;
+
+fail:
+	return err;
+}
+
+static inline int __vringh_complete(struct vringh *vrh,
+				    const struct vring_used_elem *used,
+				    unsigned int num_used,
+				    int (*putu16)(const struct vringh *vrh,
+						  __virtio16 *p, u16 val),
+				    int (*putused)(struct vring_used_elem *dst,
+						   const struct vring_used_elem
+						   *src, unsigned num))
+{
+	struct vring_used *used_ring;
+	int err;
+	u16 used_idx, off;
+
+	used_ring = vrh->vring.used;
+	used_idx = vrh->last_used_idx + vrh->completed;
+
+	off = used_idx % vrh->vring.num;
+
+	/* Compiler knows num_used == 1 sometimes, hence extra check */
+	if (num_used > 1 && unlikely(off + num_used >= vrh->vring.num)) {
+		u16 part = vrh->vring.num - off;
+		err = putused(&used_ring->ring[off], used, part);
+		if (!err)
+			err = putused(&used_ring->ring[0], used + part,
+				      num_used - part);
+	} else
+		err = putused(&used_ring->ring[off], used, num_used);
+
+	if (err) {
+		vringh_bad("Failed to write %u used entries %u at %p",
+			   num_used, off, &used_ring->ring[off]);
+		return err;
+	}
+
+	/* Make sure buffer is written before we update index. */
+	virtio_wmb(vrh->weak_barriers);
+
+	err = putu16(vrh, &vrh->vring.used->idx, used_idx + num_used);
+	if (err) {
+		vringh_bad("Failed to update used index at %p",
+			   &vrh->vring.used->idx);
+		return err;
+	}
+
+	vrh->completed += num_used;
+	return 0;
+}
+
+
+static inline int __vringh_need_notify(struct vringh *vrh,
+				       int (*getu16)(const struct vringh *vrh,
+						     u16 *val,
+						     const __virtio16 *p))
+{
+	bool notify;
+	u16 used_event;
+	int err;
+
+	/* Flush out used index update. This is paired with the
+	 * barrier that the Guest executes when enabling
+	 * interrupts. */
+	virtio_mb(vrh->weak_barriers);
+
+	/* Old-style, without event indices. */
+	if (!vrh->event_indices) {
+		u16 flags;
+		err = getu16(vrh, &flags, &vrh->vring.avail->flags);
+		if (err) {
+			vringh_bad("Failed to get flags at %p",
+				   &vrh->vring.avail->flags);
+			return err;
+		}
+		return (!(flags & VRING_AVAIL_F_NO_INTERRUPT));
+	}
+
+	/* Modern: we know when other side wants to know. */
+	err = getu16(vrh, &used_event, &vring_used_event(&vrh->vring));
+	if (err) {
+		vringh_bad("Failed to get used event idx at %p",
+			   &vring_used_event(&vrh->vring));
+		return err;
+	}
+
+	/* Just in case we added so many that we wrap. */
+	if (unlikely(vrh->completed > 0xffff))
+		notify = true;
+	else
+		notify = vring_need_event(used_event,
+					  vrh->last_used_idx + vrh->completed,
+					  vrh->last_used_idx);
+
+	vrh->last_used_idx += vrh->completed;
+	vrh->completed = 0;
+	return notify;
+}
+
+static inline bool __vringh_notify_enable(struct vringh *vrh,
+					  int (*getu16)(const struct vringh *vrh,
+							u16 *val, const __virtio16 *p),
+					  int (*putu16)(const struct vringh *vrh,
+							__virtio16 *p, u16 val))
+{
+	u16 avail;
+
+	if (!vrh->event_indices) {
+		/* Old-school; update flags. */
+		if (putu16(vrh, &vrh->vring.used->flags, 0) != 0) {
+			vringh_bad("Clearing used flags %p",
+				   &vrh->vring.used->flags);
+			return true;
+		}
+	} else {
+		if (putu16(vrh, &vring_avail_event(&vrh->vring),
+			   vrh->last_avail_idx) != 0) {
+			vringh_bad("Updating avail event index %p",
+				   &vring_avail_event(&vrh->vring));
+			return true;
+		}
+	}
+
+	/* They could have slipped one in as we were doing that: make
+	 * sure it's written, then check again. */
+	virtio_mb(vrh->weak_barriers);
+
+	if (getu16(vrh, &avail, &vrh->vring.avail->idx) != 0) {
+		vringh_bad("Failed to check avail idx at %p",
+			   &vrh->vring.avail->idx);
+		return true;
+	}
+
+	/* This is unlikely, so we just leave notifications enabled
+	 * (if we're using event_indices, we'll only get one
+	 * notification anyway). */
+	return avail == vrh->last_avail_idx;
+}
+
+static inline void __vringh_notify_disable(struct vringh *vrh,
+					   int (*putu16)(const struct vringh *vrh,
+							 __virtio16 *p, u16 val))
+{
+	if (!vrh->event_indices) {
+		/* Old-school; update flags. */
+		if (putu16(vrh, &vrh->vring.used->flags,
+			   VRING_USED_F_NO_NOTIFY)) {
+			vringh_bad("Setting used flags %p",
+				   &vrh->vring.used->flags);
+		}
+	}
+}
+
+/* Userspace access helpers: in this case, addresses are really userspace. */
+static inline int getu16_user(const struct vringh *vrh, u16 *val, const __virtio16 *p)
+{
+	__virtio16 v = 0;
+	int rc = get_user(v, (__force __virtio16 __user *)p);
+	*val = vringh16_to_cpu(vrh, v);
+	return rc;
+}
+
+static inline int putu16_user(const struct vringh *vrh, __virtio16 *p, u16 val)
+{
+	__virtio16 v = cpu_to_vringh16(vrh, val);
+	return put_user(v, (__force __virtio16 __user *)p);
+}
+
+static inline int copydesc_user(void *dst, const void *src, size_t len)
+{
+	return copy_from_user(dst, (__force void __user *)src, len) ?
+		-EFAULT : 0;
+}
+
+static inline int putused_user(struct vring_used_elem *dst,
+			       const struct vring_used_elem *src,
+			       unsigned int num)
+{
+	return copy_to_user((__force void __user *)dst, src,
+			    sizeof(*dst) * num) ? -EFAULT : 0;
+}
+
+static inline int xfer_from_user(void *src, void *dst, size_t len)
+{
+	return copy_from_user(dst, (__force void __user *)src, len) ?
+		-EFAULT : 0;
+}
+
+static inline int xfer_to_user(void *dst, void *src, size_t len)
+{
+	return copy_to_user((__force void __user *)dst, src, len) ?
+		-EFAULT : 0;
+}
+
+/**
+ * vringh_init_user - initialize a vringh for a userspace vring.
+ * @vrh: the vringh to initialize.
+ * @features: the feature bits for this ring.
+ * @num: the number of elements.
+ * @weak_barriers: true if we only need memory barriers, not I/O.
+ * @desc: the userpace descriptor pointer.
+ * @avail: the userpace avail pointer.
+ * @used: the userpace used pointer.
+ *
+ * Returns an error if num is invalid: you should check pointers
+ * yourself!
+ */
+int vringh_init_user(struct vringh *vrh, u64 features,
+		     unsigned int num, bool weak_barriers,
+		     struct vring_desc __user *desc,
+		     struct vring_avail __user *avail,
+		     struct vring_used __user *used)
+{
+	/* Sane power of 2 please! */
+	if (!num || num > 0xffff || (num & (num - 1))) {
+		vringh_bad("Bad ring size %u", num);
+		return -EINVAL;
+	}
+
+	vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
+	vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
+	vrh->weak_barriers = weak_barriers;
+	vrh->completed = 0;
+	vrh->last_avail_idx = 0;
+	vrh->last_used_idx = 0;
+	vrh->vring.num = num;
+	/* vring expects kernel addresses, but only used via accessors. */
+	vrh->vring.desc = (__force struct vring_desc *)desc;
+	vrh->vring.avail = (__force struct vring_avail *)avail;
+	vrh->vring.used = (__force struct vring_used *)used;
+	return 0;
+}
+EXPORT_SYMBOL(vringh_init_user);
+
+/**
+ * vringh_getdesc_user - get next available descriptor from userspace ring.
+ * @vrh: the userspace vring.
+ * @riov: where to put the readable descriptors (or NULL)
+ * @wiov: where to put the writable descriptors (or NULL)
+ * @getrange: function to call to check ranges.
+ * @head: head index we received, for passing to vringh_complete_user().
+ *
+ * Returns 0 if there was no descriptor, 1 if there was, or -errno.
+ *
+ * Note that on error return, you can tell the difference between an
+ * invalid ring and a single invalid descriptor: in the former case,
+ * *head will be vrh->vring.num.  You may be able to ignore an invalid
+ * descriptor, but there's not much you can do with an invalid ring.
+ *
+ * Note that you may need to clean up riov and wiov, even on error!
+ */
+int vringh_getdesc_user(struct vringh *vrh,
+			struct vringh_iov *riov,
+			struct vringh_iov *wiov,
+			bool (*getrange)(struct vringh *vrh,
+					 u64 addr, struct vringh_range *r),
+			u16 *head)
+{
+	int err;
+
+	*head = vrh->vring.num;
+	err = __vringh_get_head(vrh, getu16_user, &vrh->last_avail_idx);
+	if (err < 0)
+		return err;
+
+	/* Empty... */
+	if (err == vrh->vring.num)
+		return 0;
+
+	/* We need the layouts to be the identical for this to work */
+	BUILD_BUG_ON(sizeof(struct vringh_kiov) != sizeof(struct vringh_iov));
+	BUILD_BUG_ON(offsetof(struct vringh_kiov, iov) !=
+		     offsetof(struct vringh_iov, iov));
+	BUILD_BUG_ON(offsetof(struct vringh_kiov, i) !=
+		     offsetof(struct vringh_iov, i));
+	BUILD_BUG_ON(offsetof(struct vringh_kiov, used) !=
+		     offsetof(struct vringh_iov, used));
+	BUILD_BUG_ON(offsetof(struct vringh_kiov, max_num) !=
+		     offsetof(struct vringh_iov, max_num));
+	BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
+	BUILD_BUG_ON(offsetof(struct iovec, iov_base) !=
+		     offsetof(struct kvec, iov_base));
+	BUILD_BUG_ON(offsetof(struct iovec, iov_len) !=
+		     offsetof(struct kvec, iov_len));
+	BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_base)
+		     != sizeof(((struct kvec *)NULL)->iov_base));
+	BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_len)
+		     != sizeof(((struct kvec *)NULL)->iov_len));
+
+	*head = err;
+	err = __vringh_iov(vrh, *head, (struct vringh_kiov *)riov,
+			   (struct vringh_kiov *)wiov,
+			   range_check, getrange, GFP_KERNEL, copydesc_user);
+	if (err)
+		return err;
+
+	return 1;
+}
+EXPORT_SYMBOL(vringh_getdesc_user);
+
+/**
+ * vringh_iov_pull_user - copy bytes from vring_iov.
+ * @riov: the riov as passed to vringh_getdesc_user() (updated as we consume)
+ * @dst: the place to copy.
+ * @len: the maximum length to copy.
+ *
+ * Returns the bytes copied <= len or a negative errno.
+ */
+ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
+{
+	return vringh_iov_xfer((struct vringh_kiov *)riov,
+			       dst, len, xfer_from_user);
+}
+EXPORT_SYMBOL(vringh_iov_pull_user);
+
+/**
+ * vringh_iov_push_user - copy bytes into vring_iov.
+ * @wiov: the wiov as passed to vringh_getdesc_user() (updated as we consume)
+ * @dst: the place to copy.
+ * @len: the maximum length to copy.
+ *
+ * Returns the bytes copied <= len or a negative errno.
+ */
+ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
+			     const void *src, size_t len)
+{
+	return vringh_iov_xfer((struct vringh_kiov *)wiov,
+			       (void *)src, len, xfer_to_user);
+}
+EXPORT_SYMBOL(vringh_iov_push_user);
+
+/**
+ * vringh_abandon_user - we've decided not to handle the descriptor(s).
+ * @vrh: the vring.
+ * @num: the number of descriptors to put back (ie. num
+ *	 vringh_get_user() to undo).
+ *
+ * The next vringh_get_user() will return the old descriptor(s) again.
+ */
+void vringh_abandon_user(struct vringh *vrh, unsigned int num)
+{
+	/* We only update vring_avail_event(vr) when we want to be notified,
+	 * so we haven't changed that yet. */
+	vrh->last_avail_idx -= num;
+}
+EXPORT_SYMBOL(vringh_abandon_user);
+
+/**
+ * vringh_complete_user - we've finished with descriptor, publish it.
+ * @vrh: the vring.
+ * @head: the head as filled in by vringh_getdesc_user.
+ * @len: the length of data we have written.
+ *
+ * You should check vringh_need_notify_user() after one or more calls
+ * to this function.
+ */
+int vringh_complete_user(struct vringh *vrh, u16 head, u32 len)
+{
+	struct vring_used_elem used;
+
+	used.id = cpu_to_vringh32(vrh, head);
+	used.len = cpu_to_vringh32(vrh, len);
+	return __vringh_complete(vrh, &used, 1, putu16_user, putused_user);
+}
+EXPORT_SYMBOL(vringh_complete_user);
+
+/**
+ * vringh_complete_multi_user - we've finished with many descriptors.
+ * @vrh: the vring.
+ * @used: the head, length pairs.
+ * @num_used: the number of used elements.
+ *
+ * You should check vringh_need_notify_user() after one or more calls
+ * to this function.
+ */
+int vringh_complete_multi_user(struct vringh *vrh,
+			       const struct vring_used_elem used[],
+			       unsigned num_used)
+{
+	return __vringh_complete(vrh, used, num_used,
+				 putu16_user, putused_user);
+}
+EXPORT_SYMBOL(vringh_complete_multi_user);
+
+/**
+ * vringh_notify_enable_user - we want to know if something changes.
+ * @vrh: the vring.
+ *
+ * This always enables notifications, but returns false if there are
+ * now more buffers available in the vring.
+ */
+bool vringh_notify_enable_user(struct vringh *vrh)
+{
+	return __vringh_notify_enable(vrh, getu16_user, putu16_user);
+}
+EXPORT_SYMBOL(vringh_notify_enable_user);
+
+/**
+ * vringh_notify_disable_user - don't tell us if something changes.
+ * @vrh: the vring.
+ *
+ * This is our normal running state: we disable and then only enable when
+ * we're going to sleep.
+ */
+void vringh_notify_disable_user(struct vringh *vrh)
+{
+	__vringh_notify_disable(vrh, putu16_user);
+}
+EXPORT_SYMBOL(vringh_notify_disable_user);
+
+/**
+ * vringh_need_notify_user - must we tell the other side about used buffers?
+ * @vrh: the vring we've called vringh_complete_user() on.
+ *
+ * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
+ */
+int vringh_need_notify_user(struct vringh *vrh)
+{
+	return __vringh_need_notify(vrh, getu16_user);
+}
+EXPORT_SYMBOL(vringh_need_notify_user);
+
+/* Kernelspace access helpers. */
+static inline int getu16_kern(const struct vringh *vrh,
+			      u16 *val, const __virtio16 *p)
+{
+	*val = vringh16_to_cpu(vrh, ACCESS_ONCE(*p));
+	return 0;
+}
+
+static inline int putu16_kern(const struct vringh *vrh, __virtio16 *p, u16 val)
+{
+	ACCESS_ONCE(*p) = cpu_to_vringh16(vrh, val);
+	return 0;
+}
+
+static inline int copydesc_kern(void *dst, const void *src, size_t len)
+{
+	memcpy(dst, src, len);
+	return 0;
+}
+
+static inline int putused_kern(struct vring_used_elem *dst,
+			       const struct vring_used_elem *src,
+			       unsigned int num)
+{
+	memcpy(dst, src, num * sizeof(*dst));
+	return 0;
+}
+
+static inline int xfer_kern(void *src, void *dst, size_t len)
+{
+	memcpy(dst, src, len);
+	return 0;
+}
+
+/**
+ * vringh_init_kern - initialize a vringh for a kernelspace vring.
+ * @vrh: the vringh to initialize.
+ * @features: the feature bits for this ring.
+ * @num: the number of elements.
+ * @weak_barriers: true if we only need memory barriers, not I/O.
+ * @desc: the userpace descriptor pointer.
+ * @avail: the userpace avail pointer.
+ * @used: the userpace used pointer.
+ *
+ * Returns an error if num is invalid.
+ */
+int vringh_init_kern(struct vringh *vrh, u64 features,
+		     unsigned int num, bool weak_barriers,
+		     struct vring_desc *desc,
+		     struct vring_avail *avail,
+		     struct vring_used *used)
+{
+	/* Sane power of 2 please! */
+	if (!num || num > 0xffff || (num & (num - 1))) {
+		vringh_bad("Bad ring size %u", num);
+		return -EINVAL;
+	}
+
+	vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
+	vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
+	vrh->weak_barriers = weak_barriers;
+	vrh->completed = 0;
+	vrh->last_avail_idx = 0;
+	vrh->last_used_idx = 0;
+	vrh->vring.num = num;
+	vrh->vring.desc = desc;
+	vrh->vring.avail = avail;
+	vrh->vring.used = used;
+	return 0;
+}
+EXPORT_SYMBOL(vringh_init_kern);
+
+/**
+ * vringh_getdesc_kern - get next available descriptor from kernelspace ring.
+ * @vrh: the kernelspace vring.
+ * @riov: where to put the readable descriptors (or NULL)
+ * @wiov: where to put the writable descriptors (or NULL)
+ * @head: head index we received, for passing to vringh_complete_kern().
+ * @gfp: flags for allocating larger riov/wiov.
+ *
+ * Returns 0 if there was no descriptor, 1 if there was, or -errno.
+ *
+ * Note that on error return, you can tell the difference between an
+ * invalid ring and a single invalid descriptor: in the former case,
+ * *head will be vrh->vring.num.  You may be able to ignore an invalid
+ * descriptor, but there's not much you can do with an invalid ring.
+ *
+ * Note that you may need to clean up riov and wiov, even on error!
+ */
+int vringh_getdesc_kern(struct vringh *vrh,
+			struct vringh_kiov *riov,
+			struct vringh_kiov *wiov,
+			u16 *head,
+			gfp_t gfp)
+{
+	int err;
+
+	err = __vringh_get_head(vrh, getu16_kern, &vrh->last_avail_idx);
+	if (err < 0)
+		return err;
+
+	/* Empty... */
+	if (err == vrh->vring.num)
+		return 0;
+
+	*head = err;
+	err = __vringh_iov(vrh, *head, riov, wiov, no_range_check, NULL,
+			   gfp, copydesc_kern);
+	if (err)
+		return err;
+
+	return 1;
+}
+EXPORT_SYMBOL(vringh_getdesc_kern);
+
+/**
+ * vringh_iov_pull_kern - copy bytes from vring_iov.
+ * @riov: the riov as passed to vringh_getdesc_kern() (updated as we consume)
+ * @dst: the place to copy.
+ * @len: the maximum length to copy.
+ *
+ * Returns the bytes copied <= len or a negative errno.
+ */
+ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len)
+{
+	return vringh_iov_xfer(riov, dst, len, xfer_kern);
+}
+EXPORT_SYMBOL(vringh_iov_pull_kern);
+
+/**
+ * vringh_iov_push_kern - copy bytes into vring_iov.
+ * @wiov: the wiov as passed to vringh_getdesc_kern() (updated as we consume)
+ * @dst: the place to copy.
+ * @len: the maximum length to copy.
+ *
+ * Returns the bytes copied <= len or a negative errno.
+ */
+ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
+			     const void *src, size_t len)
+{
+	return vringh_iov_xfer(wiov, (void *)src, len, xfer_kern);
+}
+EXPORT_SYMBOL(vringh_iov_push_kern);
+
+/**
+ * vringh_abandon_kern - we've decided not to handle the descriptor(s).
+ * @vrh: the vring.
+ * @num: the number of descriptors to put back (ie. num
+ *	 vringh_get_kern() to undo).
+ *
+ * The next vringh_get_kern() will return the old descriptor(s) again.
+ */
+void vringh_abandon_kern(struct vringh *vrh, unsigned int num)
+{
+	/* We only update vring_avail_event(vr) when we want to be notified,
+	 * so we haven't changed that yet. */
+	vrh->last_avail_idx -= num;
+}
+EXPORT_SYMBOL(vringh_abandon_kern);
+
+/**
+ * vringh_complete_kern - we've finished with descriptor, publish it.
+ * @vrh: the vring.
+ * @head: the head as filled in by vringh_getdesc_kern.
+ * @len: the length of data we have written.
+ *
+ * You should check vringh_need_notify_kern() after one or more calls
+ * to this function.
+ */
+int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len)
+{
+	struct vring_used_elem used;
+
+	used.id = cpu_to_vringh32(vrh, head);
+	used.len = cpu_to_vringh32(vrh, len);
+
+	return __vringh_complete(vrh, &used, 1, putu16_kern, putused_kern);
+}
+EXPORT_SYMBOL(vringh_complete_kern);
+
+/**
+ * vringh_notify_enable_kern - we want to know if something changes.
+ * @vrh: the vring.
+ *
+ * This always enables notifications, but returns false if there are
+ * now more buffers available in the vring.
+ */
+bool vringh_notify_enable_kern(struct vringh *vrh)
+{
+	return __vringh_notify_enable(vrh, getu16_kern, putu16_kern);
+}
+EXPORT_SYMBOL(vringh_notify_enable_kern);
+
+/**
+ * vringh_notify_disable_kern - don't tell us if something changes.
+ * @vrh: the vring.
+ *
+ * This is our normal running state: we disable and then only enable when
+ * we're going to sleep.
+ */
+void vringh_notify_disable_kern(struct vringh *vrh)
+{
+	__vringh_notify_disable(vrh, putu16_kern);
+}
+EXPORT_SYMBOL(vringh_notify_disable_kern);
+
+/**
+ * vringh_need_notify_kern - must we tell the other side about used buffers?
+ * @vrh: the vring we've called vringh_complete_kern() on.
+ *
+ * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
+ */
+int vringh_need_notify_kern(struct vringh *vrh)
+{
+	return __vringh_need_notify(vrh, getu16_kern);
+}
+EXPORT_SYMBOL(vringh_need_notify_kern);
+
+MODULE_LICENSE("GPL");