tcm_vhost: Initial merge for vhost level target fabric driver

This patch adds the initial code for tcm_vhost, a Vhost level TCM
fabric driver for virtio SCSI initiators into KVM guest.

This code is currently up and running on v3.5-rc2 host+guest
from target-pending/for-next-merge.

Using tcm_vhost requires Zhi's -> Stefan -> nab's qemu vhost-scsi tree here:

  http://git.kernel.org/?p=virt/kvm/nab/qemu-kvm.git;a=shortlog;h=refs/heads/vhost-scsi

--

Changelog v4 -> v5:

  Expose ABI version via VHOST_SCSI_GET_ABI_VERSION + use Rev 0 as
  starting point for v3.6-rc code (Stefan + ALiguori + nab)
  Convert vhost_scsi_handle_vq() to vq_err() (nab + MST)
  Minor style fixes from checkpatch (nab)

Changelog v3 -> v4:

  Rename vhost_vring_target -> vhost_scsi_target (mst + nab)
  Use TRANSPORT_IQN_LEN in vhost_scsi_target->vhost_wwpn[] def (nab)
  Move back to drivers/vhost/, and just use drivers/vhost/Kconfig.tcm (mst)
  Move TCM_VHOST related ioctl defines from include/linux/vhost.h ->
  drivers/vhost/tcm_vhost.h as requested by MST (nab)
  Move Kbuild.tcm include from drivers/staging -> drivers/vhost/, and
  just use 'if STAGING' around 'source drivers/vhost/Kbuild.tcm'

Changelog v2 -> v3:

  Unlock on error in tcm_vhost_drop_nexus() (DanC)
  Fix strlen() doesn't count the terminator (DanC)
  Call kfree() on an error path (DanC)
  Convert tcm_vhost_write_pending to use target_execute_cmd (hch + nab)
  Fix another strlen() off by one in tcm_vhost_make_tport (DanC)
  Add option under drivers/staging/Kconfig, and move to drivers/vhost/tcm/
  as requested by MST (nab)

Changelog v1 -> v2:

  Fix tv_cmd completion -> release SGL memory leak (nab)
  Fix sparse warnings for static variable usage ((Fengguang Wu)
  Fix sparse warnings for min() typing + printk format specs (Fengguang Wu)
  Convert to cmwq submission for I/O dispatch (nab + hch)

Changelog v0 -> v1:

  Merge into single source + header file, and move to drivers/vhost/
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>
Cc: Zhi Yong Wu <wuzhy@cn.ibm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

drivers/vhost/Kconfig

@@ -9,3 +9,6 @@ config VHOST_NET
 	  To compile this driver as a module, choose M here: the module will
 	  be called vhost_net.
 
+if STAGING
+source "drivers/vhost/Kconfig.tcm"
+endif

drivers/vhost/Kconfig.tcm

+config TCM_VHOST
+	tristate "TCM_VHOST fabric module (EXPERIMENTAL)"
+	depends on TARGET_CORE && EVENTFD && EXPERIMENTAL && m
+	default n
+	---help---
+	Say M here to enable the TCM_VHOST fabric module for use with virtio-scsi guests

drivers/vhost/Makefile

 obj-$(CONFIG_VHOST_NET) += vhost_net.o
 vhost_net-y := vhost.o net.o
+
+obj-$(CONFIG_TCM_VHOST) += tcm_vhost.o

drivers/vhost/tcm_vhost.c

+/*******************************************************************************
+ * Vhost kernel TCM fabric driver for virtio SCSI initiators
+ *
+ * (C) Copyright 2010-2012 RisingTide Systems LLC.
+ * (C) Copyright 2010-2012 IBM Corp.
+ *
+ * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
+ *
+ * Authors: Nicholas A. Bellinger <nab@risingtidesystems.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/vhost.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <asm/unaligned.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_tcq.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_net.h> /* TODO vhost.h currently depends on this */
+#include <linux/virtio_scsi.h>
+
+#include "vhost.c"
+#include "vhost.h"
+#include "tcm_vhost.h"
+
+struct vhost_scsi {
+	atomic_t vhost_ref_cnt;
+	struct tcm_vhost_tpg *vs_tpg;
+	struct vhost_dev dev;
+	struct vhost_virtqueue vqs[3];
+
+	struct vhost_work vs_completion_work; /* cmd completion work item */
+	struct list_head vs_completion_list;  /* cmd completion queue */
+	spinlock_t vs_completion_lock;        /* protects s_completion_list */
+};
+
+/* Local pointer to allocated TCM configfs fabric module */
+static struct target_fabric_configfs *tcm_vhost_fabric_configfs;
+
+static struct workqueue_struct *tcm_vhost_workqueue;
+
+/* Global spinlock to protect tcm_vhost TPG list for vhost IOCTL access */
+static DEFINE_MUTEX(tcm_vhost_mutex);
+static LIST_HEAD(tcm_vhost_list);
+
+static int tcm_vhost_check_true(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static int tcm_vhost_check_false(struct se_portal_group *se_tpg)
+{
+	return 0;
+}
+
+static char *tcm_vhost_get_fabric_name(void)
+{
+	return "vhost";
+}
+
+static u8 tcm_vhost_get_fabric_proto_ident(struct se_portal_group *se_tpg)
+{
+	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	struct tcm_vhost_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 *tcm_vhost_get_fabric_wwn(struct se_portal_group *se_tpg)
+{
+	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	struct tcm_vhost_tport *tport = tpg->tport;
+
+	return &tport->tport_name[0];
+}
+
+static u16 tcm_vhost_get_tag(struct se_portal_group *se_tpg)
+{
+	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	return tpg->tport_tpgt;
+}
+
+static u32 tcm_vhost_get_default_depth(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static u32 tcm_vhost_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 tcm_vhost_tpg *tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	struct tcm_vhost_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 tcm_vhost_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 tcm_vhost_tpg *tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	struct tcm_vhost_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 *tcm_vhost_parse_pr_out_transport_id(
+	struct se_portal_group *se_tpg,
+	const char *buf,
+	u32 *out_tid_len,
+	char **port_nexus_ptr)
+{
+	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	struct tcm_vhost_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 struct se_node_acl *tcm_vhost_alloc_fabric_acl(
+	struct se_portal_group *se_tpg)
+{
+	struct tcm_vhost_nacl *nacl;
+
+	nacl = kzalloc(sizeof(struct tcm_vhost_nacl), GFP_KERNEL);
+	if (!nacl) {
+		pr_err("Unable to alocate struct tcm_vhost_nacl\n");
+		return NULL;
+	}
+
+	return &nacl->se_node_acl;
+}
+
+static void tcm_vhost_release_fabric_acl(
+	struct se_portal_group *se_tpg,
+	struct se_node_acl *se_nacl)
+{
+	struct tcm_vhost_nacl *nacl = container_of(se_nacl,
+			struct tcm_vhost_nacl, se_node_acl);
+	kfree(nacl);
+}
+
+static u32 tcm_vhost_tpg_get_inst_index(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static void tcm_vhost_release_cmd(struct se_cmd *se_cmd)
+{
+	return;
+}
+
+static int tcm_vhost_shutdown_session(struct se_session *se_sess)
+{
+	return 0;
+}
+
+static void tcm_vhost_close_session(struct se_session *se_sess)
+{
+	return;
+}
+
+static u32 tcm_vhost_sess_get_index(struct se_session *se_sess)
+{
+	return 0;
+}
+
+static int tcm_vhost_write_pending(struct se_cmd *se_cmd)
+{
+	/* Go ahead and process the write immediately */
+	target_execute_cmd(se_cmd);
+	return 0;
+}
+
+static int tcm_vhost_write_pending_status(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static void tcm_vhost_set_default_node_attrs(struct se_node_acl *nacl)
+{
+	return;
+}
+
+static u32 tcm_vhost_get_task_tag(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static int tcm_vhost_get_cmd_state(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *);
+
+static int tcm_vhost_queue_data_in(struct se_cmd *se_cmd)
+{
+	struct tcm_vhost_cmd *tv_cmd = container_of(se_cmd,
+				struct tcm_vhost_cmd, tvc_se_cmd);
+	vhost_scsi_complete_cmd(tv_cmd);
+	return 0;
+}
+
+static int tcm_vhost_queue_status(struct se_cmd *se_cmd)
+{
+	struct tcm_vhost_cmd *tv_cmd = container_of(se_cmd,
+				struct tcm_vhost_cmd, tvc_se_cmd);
+	vhost_scsi_complete_cmd(tv_cmd);
+	return 0;
+}
+
+static int tcm_vhost_queue_tm_rsp(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static u16 tcm_vhost_set_fabric_sense_len(struct se_cmd *se_cmd,
+	u32 sense_length)
+{
+	return 0;
+}
+
+static u16 tcm_vhost_get_fabric_sense_len(void)
+{
+	return 0;
+}
+
+static void vhost_scsi_free_cmd(struct tcm_vhost_cmd *tv_cmd)
+{
+	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
+
+	/* TODO locking against target/backend threads? */
+	transport_generic_free_cmd(se_cmd, 1);
+
+	if (tv_cmd->tvc_sgl_count) {
+		u32 i;
+		for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
+			put_page(sg_page(&tv_cmd->tvc_sgl[i]));
+
+		kfree(tv_cmd->tvc_sgl);
+	}
+
+	kfree(tv_cmd);
+}
+
+/* Dequeue a command from the completion list */
+static struct tcm_vhost_cmd *vhost_scsi_get_cmd_from_completion(
+	struct vhost_scsi *vs)
+{
+	struct tcm_vhost_cmd *tv_cmd = NULL;
+
+	spin_lock_bh(&vs->vs_completion_lock);
+	if (list_empty(&vs->vs_completion_list)) {
+		spin_unlock_bh(&vs->vs_completion_lock);
+		return NULL;
+	}
+
+	list_for_each_entry(tv_cmd, &vs->vs_completion_list,
+			    tvc_completion_list) {
+		list_del(&tv_cmd->tvc_completion_list);
+		break;
+	}
+	spin_unlock_bh(&vs->vs_completion_lock);
+	return tv_cmd;
+}
+
+/* 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);
+	struct tcm_vhost_cmd *tv_cmd;
+
+	while ((tv_cmd = vhost_scsi_get_cmd_from_completion(vs)) != NULL) {
+		struct virtio_scsi_cmd_resp v_rsp;
+		struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
+		int ret;
+
+		pr_debug("%s tv_cmd %p resid %u status %#02x\n", __func__,
+			tv_cmd, se_cmd->residual_count, se_cmd->scsi_status);
+
+		memset(&v_rsp, 0, sizeof(v_rsp));
+		v_rsp.resid = se_cmd->residual_count;
+		/* TODO is status_qualifier field needed? */
+		v_rsp.status = se_cmd->scsi_status;
+		v_rsp.sense_len = se_cmd->scsi_sense_length;
+		memcpy(v_rsp.sense, tv_cmd->tvc_sense_buf,
+		       v_rsp.sense_len);
+		ret = copy_to_user(tv_cmd->tvc_resp, &v_rsp, sizeof(v_rsp));
+		if (likely(ret == 0))
+			vhost_add_used(&vs->vqs[2], tv_cmd->tvc_vq_desc, 0);
+		else
+			pr_err("Faulted on virtio_scsi_cmd_resp\n");
+
+		vhost_scsi_free_cmd(tv_cmd);
+	}
+
+	vhost_signal(&vs->dev, &vs->vqs[2]);
+}
+
+static void vhost_scsi_complete_cmd(struct tcm_vhost_cmd *tv_cmd)
+{
+	struct vhost_scsi *vs = tv_cmd->tvc_vhost;
+
+	pr_debug("%s tv_cmd %p\n", __func__, tv_cmd);
+
+	spin_lock_bh(&vs->vs_completion_lock);
+	list_add_tail(&tv_cmd->tvc_completion_list, &vs->vs_completion_list);
+	spin_unlock_bh(&vs->vs_completion_lock);
+
+	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
+}
+
+static struct tcm_vhost_cmd *vhost_scsi_allocate_cmd(
+	struct tcm_vhost_tpg *tv_tpg,
+	struct virtio_scsi_cmd_req *v_req,
+	u32 exp_data_len,
+	int data_direction)
+{
+	struct tcm_vhost_cmd *tv_cmd;
+	struct tcm_vhost_nexus *tv_nexus;
+	struct se_portal_group *se_tpg = &tv_tpg->se_tpg;
+	struct se_session *se_sess;
+	struct se_cmd *se_cmd;
+	int sam_task_attr;
+
+	tv_nexus = tv_tpg->tpg_nexus;
+	if (!tv_nexus) {
+		pr_err("Unable to locate active struct tcm_vhost_nexus\n");
+		return ERR_PTR(-EIO);
+	}
+	se_sess = tv_nexus->tvn_se_sess;
+
+	tv_cmd = kzalloc(sizeof(struct tcm_vhost_cmd), GFP_ATOMIC);
+	if (!tv_cmd) {
+		pr_err("Unable to allocate struct tcm_vhost_cmd\n");
+		return ERR_PTR(-ENOMEM);
+	}
+	INIT_LIST_HEAD(&tv_cmd->tvc_completion_list);
+	tv_cmd->tvc_tag = v_req->tag;
+
+	se_cmd = &tv_cmd->tvc_se_cmd;
+	/*
+	 * Locate the SAM Task Attr from virtio_scsi_cmd_req
+	 */
+	sam_task_attr = v_req->task_attr;
+	/*
+	 * Initialize struct se_cmd descriptor from TCM infrastructure
+	 */
+	transport_init_se_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess, exp_data_len,
+				data_direction, sam_task_attr,
+				&tv_cmd->tvc_sense_buf[0]);
+
+#if 0	/* FIXME: vhost_scsi_allocate_cmd() BIDI operation */
+	if (bidi)
+		se_cmd->se_cmd_flags |= SCF_BIDI;
+#endif
+	return tv_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 scatterlist *sgl,
+	unsigned int sgl_count, void __user *ptr, size_t len, int write)
+{
+	struct scatterlist *sg = sgl;
+	unsigned int npages = 0;
+	int ret;
+
+	while (len > 0) {
+		struct page *page;
+		unsigned int offset = (uintptr_t)ptr & ~PAGE_MASK;
+		unsigned int nbytes = min_t(unsigned int,
+				PAGE_SIZE - offset, len);
+
+		if (npages == sgl_count) {
+			ret = -ENOBUFS;
+			goto err;
+		}
+
+		ret = get_user_pages_fast((unsigned long)ptr, 1, write, &page);
+		BUG_ON(ret == 0); /* we should either get our page or fail */
+		if (ret < 0)
+			goto err;
+
+		sg_set_page(sg, page, nbytes, offset);
+		ptr += nbytes;
+		len -= nbytes;
+		sg++;
+		npages++;
+	}
+	return npages;
+
+err:
+	/* Put pages that we hold */
+	for (sg = sgl; sg != &sgl[npages]; sg++)
+		put_page(sg_page(sg));
+	return ret;
+}
+
+static int vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *tv_cmd,
+	struct iovec *iov, unsigned int niov, int write)
+{
+	int ret;
+	unsigned int i;
+	u32 sgl_count;
+	struct scatterlist *sg;
+
+	/*
+	 * Find out how long sglist needs to be
+	 */
+	sgl_count = 0;
+	for (i = 0; i < niov; i++) {
+		sgl_count += (((uintptr_t)iov[i].iov_base + iov[i].iov_len +
+				PAGE_SIZE - 1) >> PAGE_SHIFT) -
+				((uintptr_t)iov[i].iov_base >> PAGE_SHIFT);
+	}
+	/* TODO overflow checking */
+
+	sg = kmalloc(sizeof(tv_cmd->tvc_sgl[0]) * sgl_count, GFP_ATOMIC);
+	if (!sg)
+		return -ENOMEM;
+	pr_debug("%s sg %p sgl_count %u is_err %ld\n", __func__,
+	       sg, sgl_count, IS_ERR(sg));
+	sg_init_table(sg, sgl_count);
+
+	tv_cmd->tvc_sgl = sg;
+	tv_cmd->tvc_sgl_count = sgl_count;
+
+	pr_debug("Mapping %u iovecs for %u pages\n", niov, sgl_count);
+	for (i = 0; i < niov; i++) {
+		ret = vhost_scsi_map_to_sgl(sg, sgl_count, iov[i].iov_base,
+					iov[i].iov_len, write);
+		if (ret < 0) {
+			for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
+				put_page(sg_page(&tv_cmd->tvc_sgl[i]));
+			kfree(tv_cmd->tvc_sgl);
+			tv_cmd->tvc_sgl = NULL;
+			tv_cmd->tvc_sgl_count = 0;
+			return ret;
+		}
+
+		sg += ret;
+		sgl_count -= ret;
+	}
+	return 0;
+}
+
+static void tcm_vhost_submission_work(struct work_struct *work)
+{
+	struct tcm_vhost_cmd *tv_cmd =
+		container_of(work, struct tcm_vhost_cmd, work);
+	struct se_cmd *se_cmd = &tv_cmd->tvc_se_cmd;
+	struct scatterlist *sg_ptr, *sg_bidi_ptr = NULL;
+	int rc, sg_no_bidi = 0;
+	/*
+	 * Locate the struct se_lun pointer based on v_req->lun, and
+	 * attach it to struct se_cmd
+	 */
+	rc = transport_lookup_cmd_lun(&tv_cmd->tvc_se_cmd, tv_cmd->tvc_lun);
+	if (rc < 0) {
+		pr_err("Failed to look up lun: %d\n", tv_cmd->tvc_lun);
+		transport_send_check_condition_and_sense(&tv_cmd->tvc_se_cmd,
+			tv_cmd->tvc_se_cmd.scsi_sense_reason, 0);
+		transport_generic_free_cmd(se_cmd, 0);
+		return;
+	}
+
+	rc = target_setup_cmd_from_cdb(se_cmd, tv_cmd->tvc_cdb);
+	if (rc == -ENOMEM) {
+		transport_send_check_condition_and_sense(se_cmd,
+				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);
+		transport_generic_free_cmd(se_cmd, 0);
+		return;
+	} else if (rc < 0) {
+		if (se_cmd->se_cmd_flags & SCF_SCSI_RESERVATION_CONFLICT)
+			tcm_vhost_queue_status(se_cmd);
+		else
+			transport_send_check_condition_and_sense(se_cmd,
+					se_cmd->scsi_sense_reason, 0);
+		transport_generic_free_cmd(se_cmd, 0);
+		return;
+	}
+
+	if (tv_cmd->tvc_sgl_count) {
+		sg_ptr = tv_cmd->tvc_sgl;
+		/*
+		 * For BIDI commands, pass in the extra READ buffer
+		 * to transport_generic_map_mem_to_cmd() below..
+		 */
+/* FIXME: Fix BIDI operation in tcm_vhost_submission_work() */
+#if 0
+		if (se_cmd->se_cmd_flags & SCF_BIDI) {
+			sg_bidi_ptr = NULL;
+			sg_no_bidi = 0;
+		}
+#endif
+	} else {
+		sg_ptr = NULL;
+	}
+
+	rc = transport_generic_map_mem_to_cmd(se_cmd, sg_ptr,
+				tv_cmd->tvc_sgl_count, sg_bidi_ptr,
+				sg_no_bidi);
+	if (rc < 0) {
+		transport_send_check_condition_and_sense(se_cmd,
+				se_cmd->scsi_sense_reason, 0);
+		transport_generic_free_cmd(se_cmd, 0);
+		return;
+	}
+	transport_handle_cdb_direct(se_cmd);
+}
+
+static void vhost_scsi_handle_vq(struct vhost_scsi *vs)
+{
+	struct vhost_virtqueue *vq = &vs->vqs[2];
+	struct virtio_scsi_cmd_req v_req;
+	struct tcm_vhost_tpg *tv_tpg;
+	struct tcm_vhost_cmd *tv_cmd;
+	u32 exp_data_len, data_first, data_num, data_direction;
+	unsigned out, in, i;
+	int head, ret;
+
+	/* Must use ioctl VHOST_SCSI_SET_ENDPOINT */
+	tv_tpg = vs->vs_tpg;
+	if (unlikely(!tv_tpg)) {
+		pr_err("%s endpoint not set\n", __func__);
+		return;
+	}
+
+	mutex_lock(&vq->mutex);
+	vhost_disable_notify(&vs->dev, vq);
+
+	for (;;) {
+		head = vhost_get_vq_desc(&vs->dev, 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;
+		}
+
+/* FIXME: BIDI operation */
+		if (out == 1 && in == 1) {
+			data_direction = DMA_NONE;
+			data_first = 0;
+			data_num = 0;
+		} else if (out == 1 && in > 1) {
+			data_direction = DMA_FROM_DEVICE;
+			data_first = out + 1;
+			data_num = in - 1;
+		} else if (out > 1 && in == 1) {
+			data_direction = DMA_TO_DEVICE;
+			data_first = 1;
+			data_num = out - 1;
+		} else {
+			vq_err(vq, "Invalid buffer layout out: %u in: %u\n",
+					out, in);
+			break;
+		}
+
+		/*
+		 * Check for a sane resp buffer so we can report errors to
+		 * the guest.
+		 */
+		if (unlikely(vq->iov[out].iov_len !=
+					sizeof(struct virtio_scsi_cmd_resp))) {
+			vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
+				" bytes\n", vq->iov[out].iov_len);
+			break;
+		}
+
+		if (unlikely(vq->iov[0].iov_len != sizeof(v_req))) {
+			vq_err(vq, "Expecting virtio_scsi_cmd_req, got %zu"
+				" bytes\n", vq->iov[0].iov_len);
+			break;
+		}
+		pr_debug("Calling __copy_from_user: vq->iov[0].iov_base: %p,"
+			" len: %zu\n", vq->iov[0].iov_base, sizeof(v_req));
+		ret = __copy_from_user(&v_req, vq->iov[0].iov_base,
+				sizeof(v_req));
+		if (unlikely(ret)) {
+			vq_err(vq, "Faulted on virtio_scsi_cmd_req\n");
+			break;
+		}
+
+		exp_data_len = 0;
+		for (i = 0; i < data_num; i++)
+			exp_data_len += vq->iov[data_first + i].iov_len;
+
+		tv_cmd = vhost_scsi_allocate_cmd(tv_tpg, &v_req,
+					exp_data_len, data_direction);
+		if (IS_ERR(tv_cmd)) {
+			vq_err(vq, "vhost_scsi_allocate_cmd failed %ld\n",
+					PTR_ERR(tv_cmd));
+			break;
+		}
+		pr_debug("Allocated tv_cmd: %p exp_data_len: %d, data_direction"
+			": %d\n", tv_cmd, exp_data_len, data_direction);
+
+		tv_cmd->tvc_vhost = vs;
+
+		if (unlikely(vq->iov[out].iov_len !=
+				sizeof(struct virtio_scsi_cmd_resp))) {
+			vq_err(vq, "Expecting virtio_scsi_cmd_resp, got %zu"
+				" bytes, out: %d, in: %d\n",
+				vq->iov[out].iov_len, out, in);
+			break;
+		}
+
+		tv_cmd->tvc_resp = vq->iov[out].iov_base;
+
+		/*
+		 * Copy in the recieved CDB descriptor into tv_cmd->tvc_cdb
+		 * that will be used by tcm_vhost_new_cmd_map() and down into
+		 * target_setup_cmd_from_cdb()
+		 */
+		memcpy(tv_cmd->tvc_cdb, v_req.cdb, TCM_VHOST_MAX_CDB_SIZE);
+		/*
+		 * Check that the recieved CDB size does not exceeded our
+		 * hardcoded max for tcm_vhost
+		 */
+		/* TODO what if cdb was too small for varlen cdb header? */
+		if (unlikely(scsi_command_size(tv_cmd->tvc_cdb) >
+					TCM_VHOST_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(tv_cmd->tvc_cdb),
+				TCM_VHOST_MAX_CDB_SIZE);
+			break; /* TODO */
+		}
+		tv_cmd->tvc_lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
+
+		pr_debug("vhost_scsi got command opcode: %#02x, lun: %d\n",
+			tv_cmd->tvc_cdb[0], tv_cmd->tvc_lun);
+
+		if (data_direction != DMA_NONE) {
+			ret = vhost_scsi_map_iov_to_sgl(tv_cmd,
+					&vq->iov[data_first], data_num,
+					data_direction == DMA_TO_DEVICE);
+			if (unlikely(ret)) {
+				vq_err(vq, "Failed to map iov to sgl\n");
+				break; /* TODO */
+			}
+		}
+
+		/*
+		 * Save the descriptor from vhost_get_vq_desc() to be used to
+		 * complete the virtio-scsi request in TCM callback context via
+		 * tcm_vhost_queue_data_in() and tcm_vhost_queue_status()
+		 */
+		tv_cmd->tvc_vq_desc = head;
+		/*
+		 * Dispatch tv_cmd descriptor for cmwq execution in process
+		 * context provided by tcm_vhost_workqueue.  This also ensures
+		 * tv_cmd is executed on the same kworker CPU as this vhost
+		 * thread to gain positive L2 cache locality effects..
+		 */
+		INIT_WORK(&tv_cmd->work, tcm_vhost_submission_work);
+		queue_work(tcm_vhost_workqueue, &tv_cmd->work);
+	}
+
+	mutex_unlock(&vq->mutex);
+}
+
+static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
+{
+	pr_err("%s: The handling func for control queue.\n", __func__);
+}
+
+static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
+{
+	pr_err("%s: The handling func for event queue.\n", __func__);
+}
+
+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);
+}
+
+/*
+ * Called from vhost_scsi_ioctl() context to walk the list of available
+ * tcm_vhost_tpg with an active struct tcm_vhost_nexus
+ */
+static int vhost_scsi_set_endpoint(
+	struct vhost_scsi *vs,
+	struct vhost_scsi_target *t)
+{
+	struct tcm_vhost_tport *tv_tport;
+	struct tcm_vhost_tpg *tv_tpg;
+	int index;
+
+	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])) {
+			mutex_unlock(&vs->dev.mutex);
+			return -EFAULT;
+		}
+	}
+
+	if (vs->vs_tpg) {
+		mutex_unlock(&vs->dev.mutex);
+		return -EEXIST;
+	}
+	mutex_unlock(&vs->dev.mutex);
+
+	mutex_lock(&tcm_vhost_mutex);
+	list_for_each_entry(tv_tpg, &tcm_vhost_list, tv_tpg_list) {
+		mutex_lock(&tv_tpg->tv_tpg_mutex);
+		if (!tv_tpg->tpg_nexus) {
+			mutex_unlock(&tv_tpg->tv_tpg_mutex);
+			continue;
+		}
+		if (atomic_read(&tv_tpg->tv_tpg_vhost_count)) {
+			mutex_unlock(&tv_tpg->tv_tpg_mutex);
+			continue;
+		}
+		tv_tport = tv_tpg->tport;
+
+		if (!strcmp(tv_tport->tport_name, t->vhost_wwpn) &&
+		    (tv_tpg->tport_tpgt == t->vhost_tpgt)) {
+			atomic_inc(&tv_tpg->tv_tpg_vhost_count);
+			smp_mb__after_atomic_inc();
+			mutex_unlock(&tv_tpg->tv_tpg_mutex);
+			mutex_unlock(&tcm_vhost_mutex);
+
+			mutex_lock(&vs->dev.mutex);
+			vs->vs_tpg = tv_tpg;
+			atomic_inc(&vs->vhost_ref_cnt);
+			smp_mb__after_atomic_inc();
+			mutex_unlock(&vs->dev.mutex);
+			return 0;
+		}
+		mutex_unlock(&tv_tpg->tv_tpg_mutex);
+	}
+	mutex_unlock(&tcm_vhost_mutex);
+	return -EINVAL;
+}
+
+static int vhost_scsi_clear_endpoint(
+	struct vhost_scsi *vs,
+	struct vhost_scsi_target *t)
+{
+	struct tcm_vhost_tport *tv_tport;
+	struct tcm_vhost_tpg *tv_tpg;
+	int index;
+
+	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])) {
+			mutex_unlock(&vs->dev.mutex);
+			return -EFAULT;
+		}
+	}
+
+	if (!vs->vs_tpg) {
+		mutex_unlock(&vs->dev.mutex);
+		return -ENODEV;
+	}
+	tv_tpg = vs->vs_tpg;
+	tv_tport = tv_tpg->tport;
+
+	if (strcmp(tv_tport->tport_name, t->vhost_wwpn) ||
+	    (tv_tpg->tport_tpgt != t->vhost_tpgt)) {
+		mutex_unlock(&vs->dev.mutex);
+		pr_warn("tv_tport->tport_name: %s, tv_tpg->tport_tpgt: %hu"
+			" does not match t->vhost_wwpn: %s, t->vhost_tpgt: %hu\n",
+			tv_tport->tport_name, tv_tpg->tport_tpgt,
+			t->vhost_wwpn, t->vhost_tpgt);
+		return -EINVAL;
+	}
+	atomic_dec(&tv_tpg->tv_tpg_vhost_count);
+	vs->vs_tpg = NULL;
+	mutex_unlock(&vs->dev.mutex);
+
+	return 0;
+}
+
+static int vhost_scsi_open(struct inode *inode, struct file *f)
+{
+	struct vhost_scsi *s;
+	int r;
+
+	s = kzalloc(sizeof(*s), GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+
+	vhost_work_init(&s->vs_completion_work, vhost_scsi_complete_cmd_work);
+	INIT_LIST_HEAD(&s->vs_completion_list);
+	spin_lock_init(&s->vs_completion_lock);
+
+	s->vqs[0].handle_kick = vhost_scsi_ctl_handle_kick;
+	s->vqs[1].handle_kick = vhost_scsi_evt_handle_kick;
+	s->vqs[2].handle_kick = vhost_scsi_handle_kick;
+	r = vhost_dev_init(&s->dev, s->vqs, 3);
+	if (r < 0) {
+		kfree(s);
+		return r;
+	}
+
+	f->private_data = s;
+	return 0;
+}
+
+static int vhost_scsi_release(struct inode *inode, struct file *f)
+{
+	struct vhost_scsi *s = f->private_data;
+
+	if (s->vs_tpg && s->vs_tpg->tport) {
+		struct vhost_scsi_target backend;
+
+		memcpy(backend.vhost_wwpn, s->vs_tpg->tport->tport_name,
+				sizeof(backend.vhost_wwpn));
+		backend.vhost_tpgt = s->vs_tpg->tport_tpgt;
+		vhost_scsi_clear_endpoint(s, &backend);
+	}
+
+	vhost_dev_cleanup(&s->dev, false);
+	kfree(s);
+	return 0;
+}
+
+static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
+{
+	if (features & ~VHOST_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;
+	}
+	vs->dev.acked_features = features;
+	/* TODO possibly smp_wmb() and flush vqs */
+	mutex_unlock(&vs->dev.mutex);
+	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;
+	u64 features;
+	int r;
+
+	switch (ioctl) {
+	case VHOST_SCSI_SET_ENDPOINT:
+		if (copy_from_user(&backend, argp, sizeof backend))
+			return -EFAULT;
+
+		return vhost_scsi_set_endpoint(vs, &backend);
+	case VHOST_SCSI_CLEAR_ENDPOINT:
+		if (copy_from_user(&backend, argp, sizeof backend))
+			return -EFAULT;
+
+		return vhost_scsi_clear_endpoint(vs, &backend);
+	case VHOST_SCSI_GET_ABI_VERSION:
+		if (copy_from_user(&backend, argp, sizeof backend))
+			return -EFAULT;
+
+		backend.abi_version = VHOST_SCSI_ABI_VERSION;
+
+		if (copy_to_user(argp, &backend, sizeof backend))
+			return -EFAULT;
+		return 0;
+	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;
+		return vhost_scsi_set_features(vs, features);
+	default:
+		mutex_lock(&vs->dev.mutex);
+		r = vhost_dev_ioctl(&vs->dev, ioctl, arg);
+		mutex_unlock(&vs->dev.mutex);
+		return r;
+	}
+}
+
+static const struct file_operations vhost_scsi_fops = {
+	.owner          = THIS_MODULE,
+	.release        = vhost_scsi_release,
+	.unlocked_ioctl = vhost_scsi_ioctl,
+	/* TODO compat ioctl? */
+	.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 *tcm_vhost_dump_proto_id(struct tcm_vhost_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 int tcm_vhost_port_link(
+	struct se_portal_group *se_tpg,
+	struct se_lun *lun)
+{
+	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+
+	atomic_inc(&tv_tpg->tv_tpg_port_count);
+	smp_mb__after_atomic_inc();
+
+	return 0;
+}
+
+static void tcm_vhost_port_unlink(
+	struct se_portal_group *se_tpg,
+	struct se_lun *se_lun)
+{
+	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+
+	atomic_dec(&tv_tpg->tv_tpg_port_count);
+	smp_mb__after_atomic_dec();
+}
+
+static struct se_node_acl *tcm_vhost_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 tcm_vhost_nacl *nacl;
+	u64 wwpn = 0;
+	u32 nexus_depth;
+
+	/* tcm_vhost_parse_wwn(name, &wwpn, 1) < 0)
+		return ERR_PTR(-EINVAL); */
+	se_nacl_new = tcm_vhost_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)) {
+		tcm_vhost_release_fabric_acl(se_tpg, se_nacl_new);
+		return se_nacl;
+	}
+	/*
+	 * Locate our struct tcm_vhost_nacl and set the FC Nport WWPN
+	 */
+	nacl = container_of(se_nacl, struct tcm_vhost_nacl, se_node_acl);
+	nacl->iport_wwpn = wwpn;
+
+	return se_nacl;
+}
+
+static void tcm_vhost_drop_nodeacl(struct se_node_acl *se_acl)
+{
+	struct tcm_vhost_nacl *nacl = container_of(se_acl,
+				struct tcm_vhost_nacl, se_node_acl);
+	core_tpg_del_initiator_node_acl(se_acl->se_tpg, se_acl, 1);
+	kfree(nacl);
+}
+
+static int tcm_vhost_make_nexus(
+	struct tcm_vhost_tpg *tv_tpg,
+	const char *name)
+{
+	struct se_portal_group *se_tpg;
+	struct tcm_vhost_nexus *tv_nexus;
+
+	mutex_lock(&tv_tpg->tv_tpg_mutex);
+	if (tv_tpg->tpg_nexus) {
+		mutex_unlock(&tv_tpg->tv_tpg_mutex);
+		pr_debug("tv_tpg->tpg_nexus already exists\n");
+		return -EEXIST;
+	}
+	se_tpg = &tv_tpg->se_tpg;
+
+	tv_nexus = kzalloc(sizeof(struct tcm_vhost_nexus), GFP_KERNEL);
+	if (!tv_nexus) {
+		mutex_unlock(&tv_tpg->tv_tpg_mutex);
+		pr_err("Unable to allocate struct tcm_vhost_nexus\n");
+		return -ENOMEM;
+	}
+	/*
+	 *  Initialize the struct se_session pointer
+	 */
+	tv_nexus->tvn_se_sess = transport_init_session();
+	if (IS_ERR(tv_nexus->tvn_se_sess)) {
+		mutex_unlock(&tv_tpg->tv_tpg_mutex);
+		kfree(tv_nexus);
+		return -ENOMEM;
+	}
+	/*
+	 * Since we are running in 'demo mode' this call with generate a
+	 * struct se_node_acl for the tcm_vhost 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(&tv_tpg->tv_tpg_mutex);
+		pr_debug("core_tpg_check_initiator_node_acl() failed"
+				" for %s\n", name);
+		transport_free_session(tv_nexus->tvn_se_sess);
+		kfree(tv_nexus);
+		return -ENOMEM;
+	}
+	/*
+	 * Now register the TCM vHost virtual I_T Nexus as active with the
+	 * call to __transport_register_session()
+	 */
+	__transport_register_session(se_tpg, tv_nexus->tvn_se_sess->se_node_acl,
+			tv_nexus->tvn_se_sess, tv_nexus);
+	tv_tpg->tpg_nexus = tv_nexus;
+
+	mutex_unlock(&tv_tpg->tv_tpg_mutex);
+	return 0;
+}
+
+static int tcm_vhost_drop_nexus(
+	struct tcm_vhost_tpg *tpg)
+{
+	struct se_session *se_sess;
+	struct tcm_vhost_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 (atomic_read(&tpg->tv_tpg_port_count)) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to remove TCM_vHost I_T Nexus with"
+			" active TPG port count: %d\n",
+			atomic_read(&tpg->tv_tpg_port_count));
+		return -EPERM;
+	}
+
+	if (atomic_read(&tpg->tv_tpg_vhost_count)) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to remove TCM_vHost I_T Nexus with"
+			" active TPG vhost count: %d\n",
+			atomic_read(&tpg->tv_tpg_vhost_count));
+		return -EPERM;
+	}
+
+	pr_debug("TCM_vHost_ConfigFS: Removing I_T Nexus to emulated"
+		" %s Initiator Port: %s\n", tcm_vhost_dump_proto_id(tpg->tport),
+		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
+	/*
+	 * 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 tcm_vhost_tpg_show_nexus(
+	struct se_portal_group *se_tpg,
+	char *page)
+{
+	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	struct tcm_vhost_nexus *tv_nexus;
+	ssize_t ret;
+
+	mutex_lock(&tv_tpg->tv_tpg_mutex);
+	tv_nexus = tv_tpg->tpg_nexus;
+	if (!tv_nexus) {
+		mutex_unlock(&tv_tpg->tv_tpg_mutex);
+		return -ENODEV;
+	}
+	ret = snprintf(page, PAGE_SIZE, "%s\n",
+			tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
+	mutex_unlock(&tv_tpg->tv_tpg_mutex);
+
+	return ret;
+}
+
+static ssize_t tcm_vhost_tpg_store_nexus(
+	struct se_portal_group *se_tpg,
+	const char *page,
+	size_t count)
+{
+	struct tcm_vhost_tpg *tv_tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+	struct tcm_vhost_tport *tport_wwn = tv_tpg->tport;
+	unsigned char i_port[TCM_VHOST_NAMELEN], *ptr, *port_ptr;
+	int ret;
+	/*
+	 * Shutdown the active I_T nexus if 'NULL' is passed..
+	 */
+	if (!strncmp(page, "NULL", 4)) {
+		ret = tcm_vhost_drop_nexus(tv_tpg);
+		return (!ret) ? count : ret;
+	}
+	/*
+	 * Otherwise make sure the passed virtual Initiator port WWN matches
+	 * the fabric protocol_id set in tcm_vhost_make_tport(), and call
+	 * tcm_vhost_make_nexus().
+	 */
+	if (strlen(page) >= TCM_VHOST_NAMELEN) {
+		pr_err("Emulated NAA Sas Address: %s, exceeds"
+				" max: %d\n", page, TCM_VHOST_NAMELEN);
+		return -EINVAL;
+	}
+	snprintf(&i_port[0], TCM_VHOST_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,
+				tcm_vhost_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,
+				tcm_vhost_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,
+				tcm_vhost_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 = tcm_vhost_make_nexus(tv_tpg, port_ptr);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+TF_TPG_BASE_ATTR(tcm_vhost, nexus, S_IRUGO | S_IWUSR);
+
+static struct configfs_attribute *tcm_vhost_tpg_attrs[] = {
+	&tcm_vhost_tpg_nexus.attr,
+	NULL,
+};
+
+static struct se_portal_group *tcm_vhost_make_tpg(
+	struct se_wwn *wwn,
+	struct config_group *group,
+	const char *name)
+{
+	struct tcm_vhost_tport *tport = container_of(wwn,
+			struct tcm_vhost_tport, tport_wwn);
+
+	struct tcm_vhost_tpg *tpg;
+	unsigned long tpgt;
+	int ret;
+
+	if (strstr(name, "tpgt_") != name)
+		return ERR_PTR(-EINVAL);
+	if (kstrtoul(name + 5, 10, &tpgt) || tpgt > UINT_MAX)
+		return ERR_PTR(-EINVAL);
+
+	tpg = kzalloc(sizeof(struct tcm_vhost_tpg), GFP_KERNEL);
+	if (!tpg) {
+		pr_err("Unable to allocate struct tcm_vhost_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(&tcm_vhost_fabric_configfs->tf_ops, wwn,
+				&tpg->se_tpg, tpg, TRANSPORT_TPG_TYPE_NORMAL);
+	if (ret < 0) {
+		kfree(tpg);
+		return NULL;
+	}
+	mutex_lock(&tcm_vhost_mutex);
+	list_add_tail(&tpg->tv_tpg_list, &tcm_vhost_list);
+	mutex_unlock(&tcm_vhost_mutex);
+
+	return &tpg->se_tpg;
+}
+
+static void tcm_vhost_drop_tpg(struct se_portal_group *se_tpg)
+{
+	struct tcm_vhost_tpg *tpg = container_of(se_tpg,
+				struct tcm_vhost_tpg, se_tpg);
+
+	mutex_lock(&tcm_vhost_mutex);
+	list_del(&tpg->tv_tpg_list);
+	mutex_unlock(&tcm_vhost_mutex);
+	/*
+	 * Release the virtual I_T Nexus for this vHost TPG
+	 */
+	tcm_vhost_drop_nexus(tpg);
+	/*
+	 * Deregister the se_tpg from TCM..
+	 */
+	core_tpg_deregister(se_tpg);
+	kfree(tpg);
+}
+
+static struct se_wwn *tcm_vhost_make_tport(
+	struct target_fabric_configfs *tf,
+	struct config_group *group,
+	const char *name)
+{
+	struct tcm_vhost_tport *tport;
+	char *ptr;
+	u64 wwpn = 0;
+	int off = 0;
+
+	/* if (tcm_vhost_parse_wwn(name, &wwpn, 1) < 0)
+		return ERR_PTR(-EINVAL); */
+
+	tport = kzalloc(sizeof(struct tcm_vhost_tport), GFP_KERNEL);
+	if (!tport) {
+		pr_err("Unable to allocate struct tcm_vhost_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) >= TCM_VHOST_NAMELEN) {
+		pr_err("Emulated %s Address: %s, exceeds"
+			" max: %d\n", name, tcm_vhost_dump_proto_id(tport),
+			TCM_VHOST_NAMELEN);
+		kfree(tport);
+		return ERR_PTR(-EINVAL);
+	}
+	snprintf(&tport->tport_name[0], TCM_VHOST_NAMELEN, "%s", &name[off]);
+
+	pr_debug("TCM_VHost_ConfigFS: Allocated emulated Target"
+		" %s Address: %s\n", tcm_vhost_dump_proto_id(tport), name);
+
+	return &tport->tport_wwn;
+}
+
+static void tcm_vhost_drop_tport(struct se_wwn *wwn)
+{
+	struct tcm_vhost_tport *tport = container_of(wwn,
+				struct tcm_vhost_tport, tport_wwn);
+
+	pr_debug("TCM_VHost_ConfigFS: Deallocating emulated Target"
+		" %s Address: %s\n", tcm_vhost_dump_proto_id(tport),
+		tport->tport_name);
+
+	kfree(tport);
+}
+
+static ssize_t tcm_vhost_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", TCM_VHOST_VERSION, utsname()->sysname,
+		utsname()->machine);
+}
+
+TF_WWN_ATTR_RO(tcm_vhost, version);
+
+static struct configfs_attribute *tcm_vhost_wwn_attrs[] = {
+	&tcm_vhost_wwn_version.attr,
+	NULL,
+};
+
+static struct target_core_fabric_ops tcm_vhost_ops = {
+	.get_fabric_name		= tcm_vhost_get_fabric_name,
+	.get_fabric_proto_ident		= tcm_vhost_get_fabric_proto_ident,
+	.tpg_get_wwn			= tcm_vhost_get_fabric_wwn,
+	.tpg_get_tag			= tcm_vhost_get_tag,
+	.tpg_get_default_depth		= tcm_vhost_get_default_depth,
+	.tpg_get_pr_transport_id	= tcm_vhost_get_pr_transport_id,
+	.tpg_get_pr_transport_id_len	= tcm_vhost_get_pr_transport_id_len,
+	.tpg_parse_pr_out_transport_id	= tcm_vhost_parse_pr_out_transport_id,
+	.tpg_check_demo_mode		= tcm_vhost_check_true,
+	.tpg_check_demo_mode_cache	= tcm_vhost_check_true,
+	.tpg_check_demo_mode_write_protect = tcm_vhost_check_false,
+	.tpg_check_prod_mode_write_protect = tcm_vhost_check_false,
+	.tpg_alloc_fabric_acl		= tcm_vhost_alloc_fabric_acl,
+	.tpg_release_fabric_acl		= tcm_vhost_release_fabric_acl,
+	.tpg_get_inst_index		= tcm_vhost_tpg_get_inst_index,
+	.release_cmd			= tcm_vhost_release_cmd,
+	.shutdown_session		= tcm_vhost_shutdown_session,
+	.close_session			= tcm_vhost_close_session,
+	.sess_get_index			= tcm_vhost_sess_get_index,
+	.sess_get_initiator_sid		= NULL,
+	.write_pending			= tcm_vhost_write_pending,
+	.write_pending_status		= tcm_vhost_write_pending_status,
+	.set_default_node_attributes	= tcm_vhost_set_default_node_attrs,
+	.get_task_tag			= tcm_vhost_get_task_tag,
+	.get_cmd_state			= tcm_vhost_get_cmd_state,
+	.queue_data_in			= tcm_vhost_queue_data_in,
+	.queue_status			= tcm_vhost_queue_status,
+	.queue_tm_rsp			= tcm_vhost_queue_tm_rsp,
+	.get_fabric_sense_len		= tcm_vhost_get_fabric_sense_len,
+	.set_fabric_sense_len		= tcm_vhost_set_fabric_sense_len,
+	/*
+	 * Setup callers for generic logic in target_core_fabric_configfs.c
+	 */
+	.fabric_make_wwn		= tcm_vhost_make_tport,
+	.fabric_drop_wwn		= tcm_vhost_drop_tport,
+	.fabric_make_tpg		= tcm_vhost_make_tpg,
+	.fabric_drop_tpg		= tcm_vhost_drop_tpg,
+	.fabric_post_link		= tcm_vhost_port_link,
+	.fabric_pre_unlink		= tcm_vhost_port_unlink,
+	.fabric_make_np			= NULL,
+	.fabric_drop_np			= NULL,
+	.fabric_make_nodeacl		= tcm_vhost_make_nodeacl,
+	.fabric_drop_nodeacl		= tcm_vhost_drop_nodeacl,
+};
+
+static int tcm_vhost_register_configfs(void)
+{
+	struct target_fabric_configfs *fabric;
+	int ret;
+
+	pr_debug("TCM_VHOST fabric module %s on %s/%s"
+		" on "UTS_RELEASE"\n", TCM_VHOST_VERSION, utsname()->sysname,
+		utsname()->machine);
+	/*
+	 * Register the top level struct config_item_type with TCM core
+	 */
+	fabric = target_fabric_configfs_init(THIS_MODULE, "vhost");
+	if (IS_ERR(fabric)) {
+		pr_err("target_fabric_configfs_init() failed\n");
+		return PTR_ERR(fabric);
+	}
+	/*
+	 * Setup fabric->tf_ops from our local tcm_vhost_ops
+	 */
+	fabric->tf_ops = tcm_vhost_ops;
+	/*
+	 * Setup default attribute lists for various fabric->tf_cit_tmpl
+	 */
+	TF_CIT_TMPL(fabric)->tfc_wwn_cit.ct_attrs = tcm_vhost_wwn_attrs;
+	TF_CIT_TMPL(fabric)->tfc_tpg_base_cit.ct_attrs = tcm_vhost_tpg_attrs;
+	TF_CIT_TMPL(fabric)->tfc_tpg_attrib_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_param_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_np_base_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_base_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_attrib_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_auth_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_nacl_param_cit.ct_attrs = NULL;
+	/*
+	 * Register the fabric for use within TCM
+	 */
+	ret = target_fabric_configfs_register(fabric);
+	if (ret < 0) {
+		pr_err("target_fabric_configfs_register() failed"
+				" for TCM_VHOST\n");
+		return ret;
+	}
+	/*
+	 * Setup our local pointer to *fabric
+	 */
+	tcm_vhost_fabric_configfs = fabric;
+	pr_debug("TCM_VHOST[0] - Set fabric -> tcm_vhost_fabric_configfs\n");
+	return 0;
+};
+
+static void tcm_vhost_deregister_configfs(void)
+{
+	if (!tcm_vhost_fabric_configfs)
+		return;
+
+	target_fabric_configfs_deregister(tcm_vhost_fabric_configfs);
+	tcm_vhost_fabric_configfs = NULL;
+	pr_debug("TCM_VHOST[0] - Cleared tcm_vhost_fabric_configfs\n");
+};
+
+static int __init tcm_vhost_init(void)
+{
+	int ret = -ENOMEM;
+
+	tcm_vhost_workqueue = alloc_workqueue("tcm_vhost", 0, 0);
+	if (!tcm_vhost_workqueue)
+		goto out;
+
+	ret = vhost_scsi_register();
+	if (ret < 0)
+		goto out_destroy_workqueue;
+
+	ret = tcm_vhost_register_configfs();
+	if (ret < 0)
+		goto out_vhost_scsi_deregister;
+
+	return 0;
+
+out_vhost_scsi_deregister:
+	vhost_scsi_deregister();
+out_destroy_workqueue:
+	destroy_workqueue(tcm_vhost_workqueue);
+out:
+	return ret;
+};
+
+static void tcm_vhost_exit(void)
+{
+	tcm_vhost_deregister_configfs();
+	vhost_scsi_deregister();
+	destroy_workqueue(tcm_vhost_workqueue);
+};
+
+MODULE_DESCRIPTION("TCM_VHOST series fabric driver");
+MODULE_LICENSE("GPL");
+module_init(tcm_vhost_init);
+module_exit(tcm_vhost_exit);

drivers/vhost/tcm_vhost.h

+#define TCM_VHOST_VERSION  "v0.1"
+#define TCM_VHOST_NAMELEN 256
+#define TCM_VHOST_MAX_CDB_SIZE 32
+
+struct tcm_vhost_cmd {
+	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
+	int tvc_vq_desc;
+	/* 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;
+	/* Saved unpacked SCSI LUN for tcm_vhost_submission_work() */
+	u32 tvc_lun;
+	/* Pointer to the SGL formatted memory from virtio-scsi */
+	struct scatterlist *tvc_sgl;
+	/* Pointer to response */
+	struct virtio_scsi_cmd_resp __user *tvc_resp;
+	/* Pointer to vhost_scsi for our device */
+	struct vhost_scsi *tvc_vhost;
+	/* The TCM I/O descriptor that is accessed via container_of() */
+	struct se_cmd tvc_se_cmd;
+	/* work item used for cmwq dispatch to tcm_vhost_submission_work() */
+	struct work_struct work;
+	/* Copy of the incoming SCSI command descriptor block (CDB) */
+	unsigned char tvc_cdb[TCM_VHOST_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 list_head tvc_completion_list;
+};
+
+struct tcm_vhost_nexus {
+	/* Pointer to TCM session for I_T Nexus */
+	struct se_session *tvn_se_sess;
+};
+
+struct tcm_vhost_nacl {
+	/* Binary World Wide unique Port Name for Vhost Initiator port */
+	u64 iport_wwpn;
+	/* ASCII formatted WWPN for Sas Initiator port */
+	char iport_name[TCM_VHOST_NAMELEN];
+	/* Returned by tcm_vhost_make_nodeacl() */
+	struct se_node_acl se_node_acl;
+};
+
+struct tcm_vhost_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 */
+	atomic_t tv_tpg_port_count;
+	/* Used for vhost_scsi device reference to tpg_nexus */
+	atomic_t tv_tpg_vhost_count;
+	/* list for tcm_vhost_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 tcm_vhost_nexus *tpg_nexus;
+	/* Pointer back to tcm_vhost_tport */
+	struct tcm_vhost_tport *tport;
+	/* Returned by tcm_vhost_make_tpg() */
+	struct se_portal_group se_tpg;
+};
+
+struct tcm_vhost_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[TCM_VHOST_NAMELEN];
+	/* Returned by tcm_vhost_make_tport() */
+	struct se_wwn tport_wwn;
+};
+
+/*
+ * As per request from MST, keep TCM_VHOST related ioctl defines out of
+ * linux/vhost.h (user-space) for now..
+ */
+
+#include <linux/vhost.h>
+
+/*
+ * Used by QEMU userspace to ensure a consistent vhost-scsi ABI.
+ *
+ * ABI Rev 0: July 2012 version starting point for v3.6-rc merge candidate +
+ *            RFC-v2 vhost-scsi userspace.  Add GET_ABI_VERSION ioctl usage
+ */
+
+#define VHOST_SCSI_ABI_VERSION	0
+
+struct vhost_scsi_target {
+	int abi_version;
+	unsigned char vhost_wwpn[TRANSPORT_IQN_LEN];
+	unsigned short vhost_tpgt;
+};
+
+/* VHOST_SCSI specific defines */
+#define VHOST_SCSI_SET_ENDPOINT _IOW(VHOST_VIRTIO, 0x40, struct vhost_scsi_target)
+#define VHOST_SCSI_CLEAR_ENDPOINT _IOW(VHOST_VIRTIO, 0x41, struct vhost_scsi_target)
+#define VHOST_SCSI_GET_ABI_VERSION _IOW(VHOST_VIRTIO, 0x42, struct vhost_scsi_target)