xen-scsiback: Add Xen PV SCSI backend driver

Introduces the Xen pvSCSI backend. With pvSCSI it is possible for a
Xen domU to issue SCSI commands to a SCSI LUN assigned to that
domU. The SCSI commands are passed to the pvSCSI backend in a driver
domain (usually Dom0) which is owner of the physical device. This
allows e.g. to use SCSI tape drives in a Xen domU.

The code is taken from the pvSCSI implementation in Xen done by
Fujitsu based on Linux kernel 2.6.18.

Changes from the original version are:
- port to upstream kernel
- put all code in just one source file
- adapt to Linux style guide
- use target core infrastructure instead doing pure pass-through
- enable module unloading
- support SG-list in grant page(s)
- support task abort
- remove redundant struct backend
- allocate resources dynamically
- correct minor error in scsiback_fast_flush_area
- free allocated resources in case of error during I/O preparation
- remove CDB emulation, now handled by target core infrastructure

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

3 files changed, 2134 insertions, 0 deletions

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 8bc0183..b812462 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -172,6 +172,15 @@ config XEN_PCIDEV_BACKEND
 
 	  If in doubt, say m.
 
+config XEN_SCSI_BACKEND
+	tristate "XEN SCSI backend driver"
+	depends on XEN && XEN_BACKEND && TARGET_CORE
+	help
+	  The SCSI backend driver allows the kernel to export its SCSI Devices
+	  to other guests via a high-performance shared-memory interface.
+	  Only needed for systems running as XEN driver domains (e.g. Dom0) and
+	  if guests need generic access to SCSI devices.
+
 config XEN_PRIVCMD
 	tristate
 	depends on XEN
diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
index 84044b5..2140398 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_XEN_ACPI_HOTPLUG_MEMORY)	+= xen-acpi-memhotplug.o
 obj-$(CONFIG_XEN_ACPI_HOTPLUG_CPU)	+= xen-acpi-cpuhotplug.o
 obj-$(CONFIG_XEN_ACPI_PROCESSOR)	+= xen-acpi-processor.o
 obj-$(CONFIG_XEN_EFI)			+= efi.o
+obj-$(CONFIG_XEN_SCSI_BACKEND)		+= xen-scsiback.o
 xen-evtchn-y				:= evtchn.o
 xen-gntdev-y				:= gntdev.o
 xen-gntalloc-y				:= gntalloc.o
diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
new file mode 100644
index 0000000..7b565632
--- /dev/null
+++ b/drivers/xen/xen-scsiback.c
@@ -0,0 +1,2124 @@
+/*
+ * Xen SCSI backend driver
+ *
+ * Copyright (c) 2008, FUJITSU Limited
+ *
+ * Based on the blkback driver code.
+ * Adaption to kernel taget core infrastructure taken from vhost/scsi.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation; or, when distributed
+ * separately from the Linux kernel or incorporated into other
+ * software packages, subject to the following license:
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this source file (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use, copy, modify,
+ * merge, publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdarg.h>
+
+#include <linux/module.h>
+#include <linux/utsname.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+#include <linux/sched.h>
+#include <linux/list.h>
+#include <linux/gfp.h>
+#include <linux/delay.h>
+#include <linux/spinlock.h>
+#include <linux/configfs.h>
+
+#include <generated/utsrelease.h>
+
+#include <scsi/scsi_dbg.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_tcq.h>
+
+#include <target/target_core_base.h>
+#include <target/target_core_fabric.h>
+#include <target/target_core_configfs.h>
+#include <target/target_core_fabric_configfs.h>
+
+#include <asm/hypervisor.h>
+
+#include <xen/xen.h>
+#include <xen/balloon.h>
+#include <xen/events.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/page.h>
+
+#include <xen/interface/grant_table.h>
+#include <xen/interface/io/vscsiif.h>
+
+#define DPRINTK(_f, _a...)			\
+	pr_debug("(file=%s, line=%d) " _f, __FILE__ , __LINE__ , ## _a)
+
+#define VSCSI_VERSION	"v0.1"
+#define VSCSI_NAMELEN	32
+
+struct ids_tuple {
+	unsigned int hst;		/* host    */
+	unsigned int chn;		/* channel */
+	unsigned int tgt;		/* target  */
+	unsigned int lun;		/* LUN     */
+};
+
+struct v2p_entry {
+	struct ids_tuple v;		/* translate from */
+	struct scsiback_tpg *tpg;	/* translate to   */
+	unsigned int lun;
+	struct kref kref;
+	struct list_head l;
+};
+
+struct vscsibk_info {
+	struct xenbus_device *dev;
+
+	domid_t domid;
+	unsigned int irq;
+
+	struct vscsiif_back_ring ring;
+	int ring_error;
+
+	spinlock_t ring_lock;
+	atomic_t nr_unreplied_reqs;
+
+	spinlock_t v2p_lock;
+	struct list_head v2p_entry_lists;
+
+	wait_queue_head_t waiting_to_free;
+};
+
+/* theoretical maximum of grants for one request */
+#define VSCSI_MAX_GRANTS	(SG_ALL + VSCSIIF_SG_TABLESIZE)
+
+/*
+ * VSCSI_GRANT_BATCH is the maximum number of grants to be processed in one
+ * call to map/unmap grants. Don't choose it too large, as there are arrays
+ * with VSCSI_GRANT_BATCH elements allocated on the stack.
+ */
+#define VSCSI_GRANT_BATCH	16
+
+struct vscsibk_pend {
+	uint16_t rqid;
+
+	uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE];
+	uint8_t cmd_len;
+
+	uint8_t sc_data_direction;
+	uint16_t n_sg;		/* real length of SG list */
+	uint16_t n_grants;	/* SG pages and potentially SG list */
+	uint32_t data_len;
+	uint32_t result;
+
+	struct vscsibk_info *info;
+	struct v2p_entry *v2p;
+	struct scatterlist *sgl;
+
+	uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
+
+	grant_handle_t grant_handles[VSCSI_MAX_GRANTS];
+	struct page *pages[VSCSI_MAX_GRANTS];
+
+	struct se_cmd se_cmd;
+};
+
+struct scsiback_tmr {
+	atomic_t tmr_complete;
+	wait_queue_head_t tmr_wait;
+};
+
+struct scsiback_nexus {
+	/* Pointer to TCM session for I_T Nexus */
+	struct se_session *tvn_se_sess;
+};
+
+struct scsiback_tport {
+	/* SCSI protocol the tport is providing */
+	u8 tport_proto_id;
+	/* Binary World Wide unique Port Name for pvscsi Target port */
+	u64 tport_wwpn;
+	/* ASCII formatted WWPN for pvscsi Target port */
+	char tport_name[VSCSI_NAMELEN];
+	/* Returned by scsiback_make_tport() */
+	struct se_wwn tport_wwn;
+};
+
+struct scsiback_tpg {
+	/* scsiback port target portal group tag for TCM */
+	u16 tport_tpgt;
+	/* track number of TPG Port/Lun Links wrt explicit I_T Nexus shutdown */
+	int tv_tpg_port_count;
+	/* xen-pvscsi references to tpg_nexus, protected by tv_tpg_mutex */
+	int tv_tpg_fe_count;
+	/* list for scsiback_list */
+	struct list_head tv_tpg_list;
+	/* Used to protect access for tpg_nexus */
+	struct mutex tv_tpg_mutex;
+	/* Pointer to the TCM pvscsi I_T Nexus for this TPG endpoint */
+	struct scsiback_nexus *tpg_nexus;
+	/* Pointer back to scsiback_tport */
+	struct scsiback_tport *tport;
+	/* Returned by scsiback_make_tpg() */
+	struct se_portal_group se_tpg;
+	/* alias used in xenstore */
+	char param_alias[VSCSI_NAMELEN];
+	/* list of info structures related to this target portal group */
+	struct list_head info_list;
+};
+
+#define SCSIBACK_INVALID_HANDLE (~0)
+
+static bool log_print_stat;
+module_param(log_print_stat, bool, 0644);
+
+static int scsiback_max_buffer_pages = 1024;
+module_param_named(max_buffer_pages, scsiback_max_buffer_pages, int, 0644);
+MODULE_PARM_DESC(max_buffer_pages,
+"Maximum number of free pages to keep in backend buffer");
+
+static struct kmem_cache *scsiback_cachep;
+static DEFINE_SPINLOCK(free_pages_lock);
+static int free_pages_num;
+static LIST_HEAD(scsiback_free_pages);
+
+/* Global spinlock to protect scsiback TPG list */
+static DEFINE_MUTEX(scsiback_mutex);
+static LIST_HEAD(scsiback_list);
+
+/* Local pointer to allocated TCM configfs fabric module */
+static struct target_fabric_configfs *scsiback_fabric_configfs;
+
+static void scsiback_get(struct vscsibk_info *info)
+{
+	atomic_inc(&info->nr_unreplied_reqs);
+}
+
+static void scsiback_put(struct vscsibk_info *info)
+{
+	if (atomic_dec_and_test(&info->nr_unreplied_reqs))
+		wake_up(&info->waiting_to_free);
+}
+
+static void put_free_pages(struct page **page, int num)
+{
+	unsigned long flags;
+	int i = free_pages_num + num, n = num;
+
+	if (num == 0)
+		return;
+	if (i > scsiback_max_buffer_pages) {
+		n = min(num, i - scsiback_max_buffer_pages);
+		free_xenballooned_pages(n, page + num - n);
+		n = num - n;
+	}
+	spin_lock_irqsave(&free_pages_lock, flags);
+	for (i = 0; i < n; i++)
+		list_add(&page[i]->lru, &scsiback_free_pages);
+	free_pages_num += n;
+	spin_unlock_irqrestore(&free_pages_lock, flags);
+}
+
+static int get_free_page(struct page **page)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&free_pages_lock, flags);
+	if (list_empty(&scsiback_free_pages)) {
+		spin_unlock_irqrestore(&free_pages_lock, flags);
+		return alloc_xenballooned_pages(1, page, false);
+	}
+	page[0] = list_first_entry(&scsiback_free_pages, struct page, lru);
+	list_del(&page[0]->lru);
+	free_pages_num--;
+	spin_unlock_irqrestore(&free_pages_lock, flags);
+	return 0;
+}
+
+static unsigned long vaddr_page(struct page *page)
+{
+	unsigned long pfn = page_to_pfn(page);
+
+	return (unsigned long)pfn_to_kaddr(pfn);
+}
+
+static unsigned long vaddr(struct vscsibk_pend *req, int seg)
+{
+	return vaddr_page(req->pages[seg]);
+}
+
+static void scsiback_print_status(char *sense_buffer, int errors,
+					struct vscsibk_pend *pending_req)
+{
+	struct scsiback_tpg *tpg = pending_req->v2p->tpg;
+
+	pr_err("xen-pvscsi[%s:%d] cmnd[0]=%02x -> st=%02x msg=%02x host=%02x drv=%02x\n",
+	       tpg->tport->tport_name, pending_req->v2p->lun,
+	       pending_req->cmnd[0], status_byte(errors), msg_byte(errors),
+	       host_byte(errors), driver_byte(errors));
+
+	if (CHECK_CONDITION & status_byte(errors))
+		__scsi_print_sense("xen-pvscsi", sense_buffer,
+				   SCSI_SENSE_BUFFERSIZE);
+}
+
+static void scsiback_fast_flush_area(struct vscsibk_pend *req)
+{
+	struct gnttab_unmap_grant_ref unmap[VSCSI_GRANT_BATCH];
+	struct page *pages[VSCSI_GRANT_BATCH];
+	unsigned int i, invcount = 0;
+	grant_handle_t handle;
+	int err;
+
+	kfree(req->sgl);
+	req->sgl = NULL;
+	req->n_sg = 0;
+
+	if (!req->n_grants)
+		return;
+
+	for (i = 0; i < req->n_grants; i++) {
+		handle = req->grant_handles[i];
+		if (handle == SCSIBACK_INVALID_HANDLE)
+			continue;
+		gnttab_set_unmap_op(&unmap[invcount], vaddr(req, i),
+				    GNTMAP_host_map, handle);
+		req->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
+		pages[invcount] = req->pages[i];
+		put_page(pages[invcount]);
+		invcount++;
+		if (invcount < VSCSI_GRANT_BATCH)
+			continue;
+		err = gnttab_unmap_refs(unmap, NULL, pages, invcount);
+		BUG_ON(err);
+		invcount = 0;
+	}
+
+	if (invcount) {
+		err = gnttab_unmap_refs(unmap, NULL, pages, invcount);
+		BUG_ON(err);
+	}
+
+	put_free_pages(req->pages, req->n_grants);
+	req->n_grants = 0;
+}
+
+static void scsiback_free_translation_entry(struct kref *kref)
+{
+	struct v2p_entry *entry = container_of(kref, struct v2p_entry, kref);
+	struct scsiback_tpg *tpg = entry->tpg;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_fe_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	kfree(entry);
+}
+
+static void scsiback_do_resp_with_sense(char *sense_buffer, int32_t result,
+			uint32_t resid, struct vscsibk_pend *pending_req)
+{
+	struct vscsiif_response *ring_res;
+	struct vscsibk_info *info = pending_req->info;
+	int notify;
+	struct scsi_sense_hdr sshdr;
+	unsigned long flags;
+	unsigned len;
+
+	spin_lock_irqsave(&info->ring_lock, flags);
+
+	ring_res = RING_GET_RESPONSE(&info->ring, info->ring.rsp_prod_pvt);
+	info->ring.rsp_prod_pvt++;
+
+	ring_res->rslt   = result;
+	ring_res->rqid   = pending_req->rqid;
+
+	if (sense_buffer != NULL &&
+	    scsi_normalize_sense(sense_buffer, VSCSIIF_SENSE_BUFFERSIZE,
+				 &sshdr)) {
+		len = min_t(unsigned, 8 + sense_buffer[7],
+			    VSCSIIF_SENSE_BUFFERSIZE);
+		memcpy(ring_res->sense_buffer, sense_buffer, len);
+		ring_res->sense_len = len;
+	} else {
+		ring_res->sense_len = 0;
+	}
+
+	ring_res->residual_len = resid;
+
+	RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&info->ring, notify);
+	spin_unlock_irqrestore(&info->ring_lock, flags);
+
+	if (notify)
+		notify_remote_via_irq(info->irq);
+
+	if (pending_req->v2p)
+		kref_put(&pending_req->v2p->kref,
+			 scsiback_free_translation_entry);
+}
+
+static void scsiback_cmd_done(struct vscsibk_pend *pending_req)
+{
+	struct vscsibk_info *info = pending_req->info;
+	unsigned char *sense_buffer;
+	unsigned int resid;
+	int errors;
+
+	sense_buffer = pending_req->sense_buffer;
+	resid        = pending_req->se_cmd.residual_count;
+	errors       = pending_req->result;
+
+	if (errors && log_print_stat)
+		scsiback_print_status(sense_buffer, errors, pending_req);
+
+	scsiback_fast_flush_area(pending_req);
+	scsiback_do_resp_with_sense(sense_buffer, errors, resid, pending_req);
+	scsiback_put(info);
+}
+
+static void scsiback_cmd_exec(struct vscsibk_pend *pending_req)
+{
+	struct se_cmd *se_cmd = &pending_req->se_cmd;
+	struct se_session *sess = pending_req->v2p->tpg->tpg_nexus->tvn_se_sess;
+	int rc;
+
+	memset(pending_req->sense_buffer, 0, VSCSIIF_SENSE_BUFFERSIZE);
+
+	memset(se_cmd, 0, sizeof(*se_cmd));
+
+	scsiback_get(pending_req->info);
+	rc = target_submit_cmd_map_sgls(se_cmd, sess, pending_req->cmnd,
+			pending_req->sense_buffer, pending_req->v2p->lun,
+			pending_req->data_len, 0,
+			pending_req->sc_data_direction, 0,
+			pending_req->sgl, pending_req->n_sg,
+			NULL, 0, NULL, 0);
+	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 int scsiback_gnttab_data_map_batch(struct gnttab_map_grant_ref *map,
+	struct page **pg, grant_handle_t *grant, int cnt)
+{
+	int err, i;
+
+	if (!cnt)
+		return 0;
+
+	err = gnttab_map_refs(map, NULL, pg, cnt);
+	BUG_ON(err);
+	for (i = 0; i < cnt; i++) {
+		if (unlikely(map[i].status != GNTST_okay)) {
+			pr_err("xen-pvscsi: invalid buffer -- could not remap it\n");
+			map[i].handle = SCSIBACK_INVALID_HANDLE;
+			err = -ENOMEM;
+		} else {
+			get_page(pg[i]);
+		}
+		grant[i] = map[i].handle;
+	}
+	return err;
+}
+
+static int scsiback_gnttab_data_map_list(struct vscsibk_pend *pending_req,
+			struct scsiif_request_segment *seg, struct page **pg,
+			grant_handle_t *grant, int cnt, u32 flags)
+{
+	int mapcount = 0, i, err = 0;
+	struct gnttab_map_grant_ref map[VSCSI_GRANT_BATCH];
+	struct vscsibk_info *info = pending_req->info;
+
+	for (i = 0; i < cnt; i++) {
+		if (get_free_page(pg + mapcount)) {
+			put_free_pages(pg, mapcount);
+			pr_err("xen-pvscsi: no grant page\n");
+			return -ENOMEM;
+		}
+		gnttab_set_map_op(&map[mapcount], vaddr_page(pg[mapcount]),
+				  flags, seg[i].gref, info->domid);
+		mapcount++;
+		if (mapcount < VSCSI_GRANT_BATCH)
+			continue;
+		err = scsiback_gnttab_data_map_batch(map, pg, grant, mapcount);
+		pg += mapcount;
+		grant += mapcount;
+		pending_req->n_grants += mapcount;
+		if (err)
+			return err;
+		mapcount = 0;
+	}
+	err = scsiback_gnttab_data_map_batch(map, pg, grant, mapcount);
+	pending_req->n_grants += mapcount;
+	return err;
+}
+
+static int scsiback_gnttab_data_map(struct vscsiif_request *ring_req,
+					struct vscsibk_pend *pending_req)
+{
+	u32 flags;
+	int i, err, n_segs, i_seg = 0;
+	struct page **pg;
+	struct scsiif_request_segment *seg;
+	unsigned long end_seg = 0;
+	unsigned int nr_segments = (unsigned int)ring_req->nr_segments;
+	unsigned int nr_sgl = 0;
+	struct scatterlist *sg;
+	grant_handle_t *grant;
+
+	pending_req->n_sg = 0;
+	pending_req->n_grants = 0;
+	pending_req->data_len = 0;
+
+	nr_segments &= ~VSCSIIF_SG_GRANT;
+	if (!nr_segments)
+		return 0;
+
+	if (nr_segments > VSCSIIF_SG_TABLESIZE) {
+		DPRINTK("xen-pvscsi: invalid parameter nr_seg = %d\n",
+			ring_req->nr_segments);
+		return -EINVAL;
+	}
+
+	if (ring_req->nr_segments & VSCSIIF_SG_GRANT) {
+		err = scsiback_gnttab_data_map_list(pending_req, ring_req->seg,
+			pending_req->pages, pending_req->grant_handles,
+			nr_segments, GNTMAP_host_map | GNTMAP_readonly);
+		if (err)
+			return err;
+		nr_sgl = nr_segments;
+		nr_segments = 0;
+		for (i = 0; i < nr_sgl; i++) {
+			n_segs = ring_req->seg[i].length /
+				 sizeof(struct scsiif_request_segment);
+			if ((unsigned)ring_req->seg[i].offset +
+			    (unsigned)ring_req->seg[i].length > PAGE_SIZE ||
+			    n_segs * sizeof(struct scsiif_request_segment) !=
+			    ring_req->seg[i].length)
+				return -EINVAL;
+			nr_segments += n_segs;
+		}
+		if (nr_segments > SG_ALL) {
+			DPRINTK("xen-pvscsi: invalid nr_seg = %d\n",
+				nr_segments);
+			return -EINVAL;
+		}
+	}
+
+	/* free of (sgl) in fast_flush_area()*/
+	pending_req->sgl = kmalloc_array(nr_segments,
+					sizeof(struct scatterlist), GFP_KERNEL);
+	if (!pending_req->sgl)
+		return -ENOMEM;
+
+	sg_init_table(pending_req->sgl, nr_segments);
+	pending_req->n_sg = nr_segments;
+
+	flags = GNTMAP_host_map;
+	if (pending_req->sc_data_direction == DMA_TO_DEVICE)
+		flags |= GNTMAP_readonly;
+
+	pg = pending_req->pages + nr_sgl;
+	grant = pending_req->grant_handles + nr_sgl;
+	if (!nr_sgl) {
+		seg = ring_req->seg;
+		err = scsiback_gnttab_data_map_list(pending_req, seg,
+			pg, grant, nr_segments, flags);
+		if (err)
+			return err;
+	} else {
+		for (i = 0; i < nr_sgl; i++) {
+			seg = (struct scsiif_request_segment *)(
+			      vaddr(pending_req, i) + ring_req->seg[i].offset);
+			n_segs = ring_req->seg[i].length /
+				 sizeof(struct scsiif_request_segment);
+			err = scsiback_gnttab_data_map_list(pending_req, seg,
+				pg, grant, n_segs, flags);
+			if (err)
+				return err;
+			pg += n_segs;
+			grant += n_segs;
+		}
+		end_seg = vaddr(pending_req, 0) + ring_req->seg[0].offset;
+		seg = (struct scsiif_request_segment *)end_seg;
+		end_seg += ring_req->seg[0].length;
+		pg = pending_req->pages + nr_sgl;
+	}
+
+	for_each_sg(pending_req->sgl, sg, nr_segments, i) {
+		sg_set_page(sg, pg[i], seg->length, seg->offset);
+		pending_req->data_len += seg->length;
+		seg++;
+		if (nr_sgl && (unsigned long)seg >= end_seg) {
+			i_seg++;
+			end_seg = vaddr(pending_req, i_seg) +
+				  ring_req->seg[i_seg].offset;
+			seg = (struct scsiif_request_segment *)end_seg;
+			end_seg += ring_req->seg[i_seg].length;
+		}
+		if (sg->offset >= PAGE_SIZE ||
+		    sg->length > PAGE_SIZE ||
+		    sg->offset + sg->length > PAGE_SIZE)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static void scsiback_disconnect(struct vscsibk_info *info)
+{
+	wait_event(info->waiting_to_free,
+		atomic_read(&info->nr_unreplied_reqs) == 0);
+
+	unbind_from_irqhandler(info->irq, info);
+	info->irq = 0;
+	xenbus_unmap_ring_vfree(info->dev, info->ring.sring);
+}
+
+static void scsiback_device_action(struct vscsibk_pend *pending_req,
+	enum tcm_tmreq_table act, int tag)
+{
+	int rc, err = FAILED;
+	struct scsiback_tpg *tpg = pending_req->v2p->tpg;
+	struct se_cmd *se_cmd = &pending_req->se_cmd;
+	struct scsiback_tmr *tmr;
+
+	tmr = kzalloc(sizeof(struct scsiback_tmr), GFP_KERNEL);
+	if (!tmr)
+		goto out;
+
+	init_waitqueue_head(&tmr->tmr_wait);
+
+	transport_init_se_cmd(se_cmd, tpg->se_tpg.se_tpg_tfo,
+		tpg->tpg_nexus->tvn_se_sess, 0, DMA_NONE, MSG_SIMPLE_TAG,
+		&pending_req->sense_buffer[0]);
+
+	rc = core_tmr_alloc_req(se_cmd, tmr, act, GFP_KERNEL);
+	if (rc < 0)
+		goto out;
+
+	se_cmd->se_tmr_req->ref_task_tag = tag;
+
+	if (transport_lookup_tmr_lun(se_cmd, pending_req->v2p->lun) < 0)
+		goto out;
+
+	transport_generic_handle_tmr(se_cmd);
+	wait_event(tmr->tmr_wait, atomic_read(&tmr->tmr_complete));
+
+	err = (se_cmd->se_tmr_req->response == TMR_FUNCTION_COMPLETE) ?
+		SUCCESS : FAILED;
+
+out:
+	if (tmr) {
+		transport_generic_free_cmd(&pending_req->se_cmd, 1);
+		kfree(tmr);
+	}
+
+	scsiback_do_resp_with_sense(NULL, err, 0, pending_req);
+
+	kmem_cache_free(scsiback_cachep, pending_req);
+}
+
+/*
+  Perform virtual to physical translation
+*/
+static struct v2p_entry *scsiback_do_translation(struct vscsibk_info *info,
+			struct ids_tuple *v)
+{
+	struct v2p_entry *entry;
+	struct list_head *head = &(info->v2p_entry_lists);
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+	list_for_each_entry(entry, head, l) {
+		if ((entry->v.chn == v->chn) &&
+		    (entry->v.tgt == v->tgt) &&
+		    (entry->v.lun == v->lun)) {
+			kref_get(&entry->kref);
+			goto out;
+		}
+	}
+	entry = NULL;
+
+out:
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+	return entry;
+}
+
+static int prepare_pending_reqs(struct vscsibk_info *info,
+				struct vscsiif_request *ring_req,
+				struct vscsibk_pend *pending_req)
+{
+	struct v2p_entry *v2p;
+	struct ids_tuple vir;
+
+	pending_req->rqid       = ring_req->rqid;
+	pending_req->info       = info;
+
+	vir.chn = ring_req->channel;
+	vir.tgt = ring_req->id;
+	vir.lun = ring_req->lun;
+
+	v2p = scsiback_do_translation(info, &vir);
+	if (!v2p) {
+		pending_req->v2p = NULL;
+		DPRINTK("xen-pvscsi: doesn't exist.\n");
+		return -ENODEV;
+	}
+	pending_req->v2p = v2p;
+
+	/* request range check from frontend */
+	pending_req->sc_data_direction = ring_req->sc_data_direction;
+	if ((pending_req->sc_data_direction != DMA_BIDIRECTIONAL) &&
+		(pending_req->sc_data_direction != DMA_TO_DEVICE) &&
+		(pending_req->sc_data_direction != DMA_FROM_DEVICE) &&
+		(pending_req->sc_data_direction != DMA_NONE)) {
+		DPRINTK("xen-pvscsi: invalid parameter data_dir = %d\n",
+			pending_req->sc_data_direction);
+		return -EINVAL;
+	}
+
+	pending_req->cmd_len = ring_req->cmd_len;
+	if (pending_req->cmd_len > VSCSIIF_MAX_COMMAND_SIZE) {
+		DPRINTK("xen-pvscsi: invalid parameter cmd_len = %d\n",
+			pending_req->cmd_len);
+		return -EINVAL;
+	}
+	memcpy(pending_req->cmnd, ring_req->cmnd, pending_req->cmd_len);
+
+	return 0;
+}
+
+static int scsiback_do_cmd_fn(struct vscsibk_info *info)
+{
+	struct vscsiif_back_ring *ring = &info->ring;
+	struct vscsiif_request *ring_req;
+	struct vscsibk_pend *pending_req;
+	RING_IDX rc, rp;
+	int err, more_to_do;
+	uint32_t result;
+	uint8_t act;
+
+	rc = ring->req_cons;
+	rp = ring->sring->req_prod;
+	rmb();	/* guest system is accessing ring, too */
+
+	if (RING_REQUEST_PROD_OVERFLOW(ring, rp)) {
+		rc = ring->rsp_prod_pvt;
+		pr_warn("xen-pvscsi: Dom%d provided bogus ring requests (%#x - %#x = %u). Halting ring processing\n",
+			   info->domid, rp, rc, rp - rc);
+		info->ring_error = 1;
+		return 0;
+	}
+
+	while ((rc != rp)) {
+		if (RING_REQUEST_CONS_OVERFLOW(ring, rc))
+			break;
+		pending_req = kmem_cache_alloc(scsiback_cachep, GFP_KERNEL);
+		if (!pending_req)
+			return 1;
+
+		ring_req = RING_GET_REQUEST(ring, rc);
+		ring->req_cons = ++rc;
+
+		act = ring_req->act;
+		err = prepare_pending_reqs(info, ring_req, pending_req);
+		if (err) {
+			switch (err) {
+			case -ENODEV:
+				result = DID_NO_CONNECT;
+				break;
+			default:
+				result = DRIVER_ERROR;
+				break;
+			}
+			scsiback_do_resp_with_sense(NULL, result << 24, 0,
+						    pending_req);
+			kmem_cache_free(scsiback_cachep, pending_req);
+			return 1;
+		}
+
+		switch (act) {
+		case VSCSIIF_ACT_SCSI_CDB:
+			if (scsiback_gnttab_data_map(ring_req, pending_req)) {
+				scsiback_fast_flush_area(pending_req);
+				scsiback_do_resp_with_sense(NULL,
+					DRIVER_ERROR << 24, 0, pending_req);
+				kmem_cache_free(scsiback_cachep, pending_req);
+			} else {
+				scsiback_cmd_exec(pending_req);
+			}
+			break;
+		case VSCSIIF_ACT_SCSI_ABORT:
+			scsiback_device_action(pending_req, TMR_ABORT_TASK,
+				ring_req->ref_rqid);
+			break;
+		case VSCSIIF_ACT_SCSI_RESET:
+			scsiback_device_action(pending_req, TMR_LUN_RESET, 0);
+			break;
+		default:
+			pr_err_ratelimited("xen-pvscsi: invalid request\n");
+			scsiback_do_resp_with_sense(NULL, DRIVER_ERROR << 24,
+						    0, pending_req);
+			kmem_cache_free(scsiback_cachep, pending_req);
+			break;
+		}
+
+		/* Yield point for this unbounded loop. */
+		cond_resched();
+	}
+
+	RING_FINAL_CHECK_FOR_REQUESTS(&info->ring, more_to_do);
+	return more_to_do;
+}
+
+static irqreturn_t scsiback_irq_fn(int irq, void *dev_id)
+{
+	struct vscsibk_info *info = dev_id;
+
+	if (info->ring_error)
+		return IRQ_HANDLED;
+
+	while (scsiback_do_cmd_fn(info))
+		cond_resched();
+
+	return IRQ_HANDLED;
+}
+
+static int scsiback_init_sring(struct vscsibk_info *info, grant_ref_t ring_ref,
+			evtchn_port_t evtchn)
+{
+	void *area;
+	struct vscsiif_sring *sring;
+	int err;
+
+	if (info->irq)
+		return -1;
+
+	err = xenbus_map_ring_valloc(info->dev, ring_ref, &area);
+	if (err)
+		return err;
+
+	sring = (struct vscsiif_sring *)area;
+	BACK_RING_INIT(&info->ring, sring, PAGE_SIZE);
+
+	err = bind_interdomain_evtchn_to_irq(info->domid, evtchn);
+	if (err < 0)
+		goto unmap_page;
+
+	info->irq = err;
+
+	err = request_threaded_irq(info->irq, NULL, scsiback_irq_fn,
+				   IRQF_ONESHOT, "vscsiif-backend", info);
+	if (err)
+		goto free_irq;
+
+	return 0;
+
+free_irq:
+	unbind_from_irqhandler(info->irq, info);
+	info->irq = 0;
+unmap_page:
+	xenbus_unmap_ring_vfree(info->dev, area);
+
+	return err;
+}
+
+static int scsiback_map(struct vscsibk_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	unsigned int ring_ref, evtchn;
+	int err;
+
+	err = xenbus_gather(XBT_NIL, dev->otherend,
+			"ring-ref", "%u", &ring_ref,
+			"event-channel", "%u", &evtchn, NULL);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "reading %s ring", dev->otherend);
+		return err;
+	}
+
+	return scsiback_init_sring(info, ring_ref, evtchn);
+}
+
+/*
+  Add a new translation entry
+*/
+static int scsiback_add_translation_entry(struct vscsibk_info *info,
+					  char *phy, struct ids_tuple *v)
+{
+	int err = 0;
+	struct v2p_entry *entry;
+	struct v2p_entry *new;
+	struct list_head *head = &(info->v2p_entry_lists);
+	unsigned long flags;
+	char *lunp;
+	unsigned int lun;
+	struct scsiback_tpg *tpg_entry, *tpg = NULL;
+	char *error = "doesn't exist";
+
+	lunp = strrchr(phy, ':');
+	if (!lunp) {
+		pr_err("xen-pvscsi: illegal format of physical device %s\n",
+			phy);
+		return -EINVAL;
+	}
+	*lunp = 0;
+	lunp++;
+	if (kstrtouint(lunp, 10, &lun) || lun >= TRANSPORT_MAX_LUNS_PER_TPG) {
+		pr_err("xen-pvscsi: lun number not valid: %s\n", lunp);
+		return -EINVAL;
+	}
+
+	mutex_lock(&scsiback_mutex);
+	list_for_each_entry(tpg_entry, &scsiback_list, tv_tpg_list) {
+		if (!strcmp(phy, tpg_entry->tport->tport_name) ||
+		    !strcmp(phy, tpg_entry->param_alias)) {
+			spin_lock(&tpg_entry->se_tpg.tpg_lun_lock);
+			if (tpg_entry->se_tpg.tpg_lun_list[lun]->lun_status ==
+			    TRANSPORT_LUN_STATUS_ACTIVE) {
+				if (!tpg_entry->tpg_nexus)
+					error = "nexus undefined";
+				else
+					tpg = tpg_entry;
+			}
+			spin_unlock(&tpg_entry->se_tpg.tpg_lun_lock);
+			break;
+		}
+	}
+	if (tpg) {
+		mutex_lock(&tpg->tv_tpg_mutex);
+		tpg->tv_tpg_fe_count++;
+		mutex_unlock(&tpg->tv_tpg_mutex);
+	}
+	mutex_unlock(&scsiback_mutex);
+
+	if (!tpg) {
+		pr_err("xen-pvscsi: %s:%d %s\n", phy, lun, error);
+		return -ENODEV;
+	}
+
+	new = kmalloc(sizeof(struct v2p_entry), GFP_KERNEL);
+	if (new == NULL) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+
+	/* Check double assignment to identical virtual ID */
+	list_for_each_entry(entry, head, l) {
+		if ((entry->v.chn == v->chn) &&
+		    (entry->v.tgt == v->tgt) &&
+		    (entry->v.lun == v->lun)) {
+			pr_warn("xen-pvscsi: Virtual ID is already used. Assignment was not performed.\n");
+			err = -EEXIST;
+			goto out;
+		}
+
+	}
+
+	/* Create a new translation entry and add to the list */
+	kref_init(&new->kref);
+	new->v = *v;
+	new->tpg = tpg;
+	new->lun = lun;
+	list_add_tail(&new->l, head);
+
+out:
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+
+out_free:
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_fe_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	if (err)
+		kfree(new);
+
+	return err;
+}
+
+static void __scsiback_del_translation_entry(struct v2p_entry *entry)
+{
+	list_del(&entry->l);
+	kref_put(&entry->kref, scsiback_free_translation_entry);
+}
+
+/*
+  Delete the translation entry specfied
+*/
+static int scsiback_del_translation_entry(struct vscsibk_info *info,
+					  struct ids_tuple *v)
+{
+	struct v2p_entry *entry;
+	struct list_head *head = &(info->v2p_entry_lists);
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+	/* Find out the translation entry specified */
+	list_for_each_entry(entry, head, l) {
+		if ((entry->v.chn == v->chn) &&
+		    (entry->v.tgt == v->tgt) &&
+		    (entry->v.lun == v->lun)) {
+			goto found;
+		}
+	}
+
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+	return 1;
+
+found:
+	/* Delete the translation entry specfied */
+	__scsiback_del_translation_entry(entry);
+
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+	return 0;
+}
+
+static void scsiback_do_add_lun(struct vscsibk_info *info, const char *state,
+				char *phy, struct ids_tuple *vir)
+{
+	if (!scsiback_add_translation_entry(info, phy, vir)) {
+		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
+				  "%d", XenbusStateInitialised)) {
+			pr_err("xen-pvscsi: xenbus_printf error %s\n", state);
+			scsiback_del_translation_entry(info, vir);
+		}
+	} else {
+		xenbus_printf(XBT_NIL, info->dev->nodename, state,
+			      "%d", XenbusStateClosed);
+	}
+}
+
+static void scsiback_do_del_lun(struct vscsibk_info *info, const char *state,
+				struct ids_tuple *vir)
+{
+	if (!scsiback_del_translation_entry(info, vir)) {
+		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
+				  "%d", XenbusStateClosed))
+			pr_err("xen-pvscsi: xenbus_printf error %s\n", state);
+	}
+}
+
+#define VSCSIBACK_OP_ADD_OR_DEL_LUN	1
+#define VSCSIBACK_OP_UPDATEDEV_STATE	2
+
+static void scsiback_do_1lun_hotplug(struct vscsibk_info *info, int op,
+				     char *ent)
+{
+	int err;
+	struct ids_tuple vir;
+	char *val;
+	int device_state;
+	char phy[VSCSI_NAMELEN];
+	char str[64];
+	char state[64];
+	struct xenbus_device *dev = info->dev;
+
+	/* read status */
+	snprintf(state, sizeof(state), "vscsi-devs/%s/state", ent);
+	err = xenbus_scanf(XBT_NIL, dev->nodename, state, "%u", &device_state);
+	if (XENBUS_EXIST_ERR(err))
+		return;
+
+	/* physical SCSI device */
+	snprintf(str, sizeof(str), "vscsi-devs/%s/p-dev", ent);
+	val = xenbus_read(XBT_NIL, dev->nodename, str, NULL);
+	if (IS_ERR(val)) {
+		xenbus_printf(XBT_NIL, dev->nodename, state,
+			      "%d", XenbusStateClosed);
+		return;
+	}
+	strlcpy(phy, val, VSCSI_NAMELEN);
+	kfree(val);
+
+	/* virtual SCSI device */
+	snprintf(str, sizeof(str), "vscsi-devs/%s/v-dev", ent);
+	err = xenbus_scanf(XBT_NIL, dev->nodename, str, "%u:%u:%u:%u",
+			   &vir.hst, &vir.chn, &vir.tgt, &vir.lun);
+	if (XENBUS_EXIST_ERR(err)) {
+		xenbus_printf(XBT_NIL, dev->nodename, state,
+			      "%d", XenbusStateClosed);
+		return;
+	}
+
+	switch (op) {
+	case VSCSIBACK_OP_ADD_OR_DEL_LUN:
+		if (device_state == XenbusStateInitialising)
+			scsiback_do_add_lun(info, state, phy, &vir);
+		if (device_state == XenbusStateClosing)
+			scsiback_do_del_lun(info, state, &vir);
+		break;
+
+	case VSCSIBACK_OP_UPDATEDEV_STATE:
+		if (device_state == XenbusStateInitialised) {
+			/* modify vscsi-devs/dev-x/state */
+			if (xenbus_printf(XBT_NIL, dev->nodename, state,
+					  "%d", XenbusStateConnected)) {
+				pr_err("xen-pvscsi: xenbus_printf error %s\n",
+				       str);
+				scsiback_del_translation_entry(info, &vir);
+				xenbus_printf(XBT_NIL, dev->nodename, state,
+					      "%d", XenbusStateClosed);
+			}
+		}
+		break;
+	/*When it is necessary, processing is added here.*/
+	default:
+		break;
+	}
+}
+
+static void scsiback_do_lun_hotplug(struct vscsibk_info *info, int op)
+{
+	int i;
+	char **dir;
+	unsigned int ndir = 0;
+
+	dir = xenbus_directory(XBT_NIL, info->dev->nodename, "vscsi-devs",
+			       &ndir);
+	if (IS_ERR(dir))
+		return;
+
+	for (i = 0; i < ndir; i++)
+		scsiback_do_1lun_hotplug(info, op, dir[i]);
+
+	kfree(dir);
+}
+
+static void scsiback_frontend_changed(struct xenbus_device *dev,
+					enum xenbus_state frontend_state)
+{
+	struct vscsibk_info *info = dev_get_drvdata(&dev->dev);
+
+	switch (frontend_state) {
+	case XenbusStateInitialising:
+		break;
+
+	case XenbusStateInitialised:
+		if (scsiback_map(info))
+			break;
+
+		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_ADD_OR_DEL_LUN);
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateConnected:
+		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_UPDATEDEV_STATE);
+
+		if (dev->state == XenbusStateConnected)
+			break;
+
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosing:
+		if (info->irq)
+			scsiback_disconnect(info);
+
+		xenbus_switch_state(dev, XenbusStateClosing);
+		break;
+
+	case XenbusStateClosed:
+		xenbus_switch_state(dev, XenbusStateClosed);
+		if (xenbus_dev_is_online(dev))
+			break;
+		/* fall through if not online */
+	case XenbusStateUnknown:
+		device_unregister(&dev->dev);
+		break;
+
+	case XenbusStateReconfiguring:
+		scsiback_do_lun_hotplug(info, VSCSIBACK_OP_ADD_OR_DEL_LUN);
+		xenbus_switch_state(dev, XenbusStateReconfigured);
+
+		break;
+
+	default:
+		xenbus_dev_fatal(dev, -EINVAL, "saw state %d at frontend",
+					frontend_state);
+		break;
+	}
+}
+
+/*
+  Release the translation entry specfied
+*/
+static void scsiback_release_translation_entry(struct vscsibk_info *info)
+{
+	struct v2p_entry *entry, *tmp;
+	struct list_head *head = &(info->v2p_entry_lists);
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->v2p_lock, flags);
+
+	list_for_each_entry_safe(entry, tmp, head, l)
+		__scsiback_del_translation_entry(entry);
+
+	spin_unlock_irqrestore(&info->v2p_lock, flags);
+}
+
+static int scsiback_remove(struct xenbus_device *dev)
+{
+	struct vscsibk_info *info = dev_get_drvdata(&dev->dev);
+
+	if (info->irq)
+		scsiback_disconnect(info);
+
+	scsiback_release_translation_entry(info);
+
+	dev_set_drvdata(&dev->dev, NULL);
+
+	return 0;
+}
+
+static int scsiback_probe(struct xenbus_device *dev,
+			   const struct xenbus_device_id *id)
+{
+	int err;
+
+	struct vscsibk_info *info = kzalloc(sizeof(struct vscsibk_info),
+					    GFP_KERNEL);
+
+	DPRINTK("%p %d\n", dev, dev->otherend_id);
+
+	if (!info) {
+		xenbus_dev_fatal(dev, -ENOMEM, "allocating backend structure");
+		return -ENOMEM;
+	}
+	info->dev = dev;
+	dev_set_drvdata(&dev->dev, info);
+
+	info->domid = dev->otherend_id;
+	spin_lock_init(&info->ring_lock);
+	info->ring_error = 0;
+	atomic_set(&info->nr_unreplied_reqs, 0);
+	init_waitqueue_head(&info->waiting_to_free);
+	info->dev = dev;
+	info->irq = 0;
+	INIT_LIST_HEAD(&info->v2p_entry_lists);
+	spin_lock_init(&info->v2p_lock);
+
+	err = xenbus_printf(XBT_NIL, dev->nodename, "feature-sg-grant", "%u",
+			    SG_ALL);
+	if (err)
+		xenbus_dev_error(dev, err, "writing feature-sg-grant");
+
+	err = xenbus_switch_state(dev, XenbusStateInitWait);
+	if (err)
+		goto fail;
+
+	return 0;
+
+fail:
+	pr_warn("xen-pvscsi: %s failed\n", __func__);
+	scsiback_remove(dev);
+
+	return err;
+}
+
+static char *scsiback_dump_proto_id(struct scsiback_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 u8 scsiback_get_fabric_proto_ident(struct se_portal_group *se_tpg)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_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 *scsiback_get_fabric_wwn(struct se_portal_group *se_tpg)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_tport *tport = tpg->tport;
+
+	return &tport->tport_name[0];
+}
+
+static u16 scsiback_get_tag(struct se_portal_group *se_tpg)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	return tpg->tport_tpgt;
+}
+
+static u32 scsiback_get_default_depth(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static u32
+scsiback_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 scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_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
+scsiback_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 scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_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 *
+scsiback_parse_pr_out_transport_id(struct se_portal_group *se_tpg,
+				    const char *buf,
+				    u32 *out_tid_len,
+				    char **port_nexus_ptr)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_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_wwn *
+scsiback_make_tport(struct target_fabric_configfs *tf,
+		     struct config_group *group,
+		     const char *name)
+{
+	struct scsiback_tport *tport;
+	char *ptr;
+	u64 wwpn = 0;
+	int off = 0;
+
+	tport = kzalloc(sizeof(struct scsiback_tport), GFP_KERNEL);
+	if (!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) >= VSCSI_NAMELEN) {
+		pr_err("Emulated %s Address: %s, exceeds max: %d\n", name,
+			scsiback_dump_proto_id(tport), VSCSI_NAMELEN);
+		kfree(tport);
+		return ERR_PTR(-EINVAL);
+	}
+	snprintf(&tport->tport_name[0], VSCSI_NAMELEN, "%s", &name[off]);
+
+	pr_debug("xen-pvscsi: Allocated emulated Target %s Address: %s\n",
+		 scsiback_dump_proto_id(tport), name);
+
+	return &tport->tport_wwn;
+}
+
+static void scsiback_drop_tport(struct se_wwn *wwn)
+{
+	struct scsiback_tport *tport = container_of(wwn,
+				struct scsiback_tport, tport_wwn);
+
+	pr_debug("xen-pvscsi: Deallocating emulated Target %s Address: %s\n",
+		 scsiback_dump_proto_id(tport), tport->tport_name);
+
+	kfree(tport);
+}
+
+static struct se_node_acl *
+scsiback_alloc_fabric_acl(struct se_portal_group *se_tpg)
+{
+	return kzalloc(sizeof(struct se_node_acl), GFP_KERNEL);
+}
+
+static void
+scsiback_release_fabric_acl(struct se_portal_group *se_tpg,
+			     struct se_node_acl *se_nacl)
+{
+	kfree(se_nacl);
+}
+
+static u32 scsiback_tpg_get_inst_index(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static int scsiback_check_stop_free(struct se_cmd *se_cmd)
+{
+	/*
+	 * Do not release struct se_cmd's containing a valid TMR
+	 * pointer.  These will be released directly in scsiback_device_action()
+	 * with transport_generic_free_cmd().
+	 */
+	if (se_cmd->se_cmd_flags & SCF_SCSI_TMR_CDB)
+		return 0;
+
+	transport_generic_free_cmd(se_cmd, 0);
+	return 1;
+}
+
+static void scsiback_release_cmd(struct se_cmd *se_cmd)
+{
+	struct vscsibk_pend *pending_req = container_of(se_cmd,
+				struct vscsibk_pend, se_cmd);
+
+	kmem_cache_free(scsiback_cachep, pending_req);
+}
+
+static int scsiback_shutdown_session(struct se_session *se_sess)
+{
+	return 0;
+}
+
+static void scsiback_close_session(struct se_session *se_sess)
+{
+}
+
+static u32 scsiback_sess_get_index(struct se_session *se_sess)
+{
+	return 0;
+}
+
+static int scsiback_write_pending(struct se_cmd *se_cmd)
+{
+	/* Go ahead and process the write immediately */
+	target_execute_cmd(se_cmd);
+
+	return 0;
+}
+
+static int scsiback_write_pending_status(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static void scsiback_set_default_node_attrs(struct se_node_acl *nacl)
+{
+}
+
+static u32 scsiback_get_task_tag(struct se_cmd *se_cmd)
+{
+	struct vscsibk_pend *pending_req = container_of(se_cmd,
+				struct vscsibk_pend, se_cmd);
+
+	return pending_req->rqid;
+}
+
+static int scsiback_get_cmd_state(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static int scsiback_queue_data_in(struct se_cmd *se_cmd)
+{
+	struct vscsibk_pend *pending_req = container_of(se_cmd,
+				struct vscsibk_pend, se_cmd);
+
+	pending_req->result = SAM_STAT_GOOD;
+	scsiback_cmd_done(pending_req);
+	return 0;
+}
+
+static int scsiback_queue_status(struct se_cmd *se_cmd)
+{
+	struct vscsibk_pend *pending_req = container_of(se_cmd,
+				struct vscsibk_pend, se_cmd);
+
+	if (se_cmd->sense_buffer &&
+	    ((se_cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) ||
+	     (se_cmd->se_cmd_flags & SCF_EMULATED_TASK_SENSE)))
+		pending_req->result = (DRIVER_SENSE << 24) |
+				      SAM_STAT_CHECK_CONDITION;
+	else
+		pending_req->result = se_cmd->scsi_status;
+
+	scsiback_cmd_done(pending_req);
+	return 0;
+}
+
+static void scsiback_queue_tm_rsp(struct se_cmd *se_cmd)
+{
+	struct se_tmr_req *se_tmr = se_cmd->se_tmr_req;
+	struct scsiback_tmr *tmr = se_tmr->fabric_tmr_ptr;
+
+	atomic_set(&tmr->tmr_complete, 1);
+	wake_up(&tmr->tmr_wait);
+}
+
+static void scsiback_aborted_task(struct se_cmd *se_cmd)
+{
+}
+
+static ssize_t scsiback_tpg_param_show_alias(struct se_portal_group *se_tpg,
+					     char *page)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg, struct scsiback_tpg,
+						se_tpg);
+	ssize_t rb;
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	rb = snprintf(page, PAGE_SIZE, "%s\n", tpg->param_alias);
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return rb;
+}
+
+static ssize_t scsiback_tpg_param_store_alias(struct se_portal_group *se_tpg,
+					      const char *page, size_t count)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg, struct scsiback_tpg,
+						se_tpg);
+	int len;
+
+	if (strlen(page) >= VSCSI_NAMELEN) {
+		pr_err("param alias: %s, exceeds max: %d\n", page,
+			VSCSI_NAMELEN);
+		return -EINVAL;
+	}
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	len = snprintf(tpg->param_alias, VSCSI_NAMELEN, "%s", page);
+	if (tpg->param_alias[len - 1] == '\n')
+		tpg->param_alias[len - 1] = '\0';
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return count;
+}
+
+TF_TPG_PARAM_ATTR(scsiback, alias, S_IRUGO | S_IWUSR);
+
+static struct configfs_attribute *scsiback_param_attrs[] = {
+	&scsiback_tpg_param_alias.attr,
+	NULL,
+};
+
+static int scsiback_make_nexus(struct scsiback_tpg *tpg,
+				const char *name)
+{
+	struct se_portal_group *se_tpg;
+	struct se_session *se_sess;
+	struct scsiback_nexus *tv_nexus;
+
+	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 scsiback_nexus), GFP_KERNEL);
+	if (!tv_nexus) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		return -ENOMEM;
+	}
+	/*
+	 *  Initialize the struct se_session pointer
+	 */
+	tv_nexus->tvn_se_sess = transport_init_session(TARGET_PROT_NORMAL);
+	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;
+	/*
+	 * Since we are running in 'demo mode' this call with generate a
+	 * struct se_node_acl for the scsiback 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 pvscsi 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);
+	tpg->tpg_nexus = tv_nexus;
+
+	mutex_unlock(&tpg->tv_tpg_mutex);
+	return 0;
+
+out:
+	transport_free_session(se_sess);
+	kfree(tv_nexus);
+	return -ENOMEM;
+}
+
+static int scsiback_drop_nexus(struct scsiback_tpg *tpg)
+{
+	struct se_session *se_sess;
+	struct scsiback_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 xen-pvscsi I_T Nexus with active TPG port count: %d\n",
+			tpg->tv_tpg_port_count);
+		return -EBUSY;
+	}
+
+	if (tpg->tv_tpg_fe_count != 0) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		pr_err("Unable to remove xen-pvscsi I_T Nexus with active TPG frontend count: %d\n",
+			tpg->tv_tpg_fe_count);
+		return -EBUSY;
+	}
+
+	pr_debug("xen-pvscsi: Removing I_T Nexus to emulated %s Initiator Port: %s\n",
+		scsiback_dump_proto_id(tpg->tport),
+		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
+
+	/*
+	 * Release the SCSI I_T Nexus to the emulated xen-pvscsi 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 scsiback_tpg_show_nexus(struct se_portal_group *se_tpg,
+					char *page)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_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 scsiback_tpg_store_nexus(struct se_portal_group *se_tpg,
+					 const char *page,
+					 size_t count)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+	struct scsiback_tport *tport_wwn = tpg->tport;
+	unsigned char i_port[VSCSI_NAMELEN], *ptr, *port_ptr;
+	int ret;
+	/*
+	 * Shutdown the active I_T nexus if 'NULL' is passed..
+	 */
+	if (!strncmp(page, "NULL", 4)) {
+		ret = scsiback_drop_nexus(tpg);
+		return (!ret) ? count : ret;
+	}
+	/*
+	 * Otherwise make sure the passed virtual Initiator port WWN matches
+	 * the fabric protocol_id set in scsiback_make_tport(), and call
+	 * scsiback_make_nexus().
+	 */
+	if (strlen(page) >= VSCSI_NAMELEN) {
+		pr_err("Emulated NAA Sas Address: %s, exceeds max: %d\n",
+			page, VSCSI_NAMELEN);
+		return -EINVAL;
+	}
+	snprintf(&i_port[0], VSCSI_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, scsiback_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, scsiback_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, scsiback_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 = scsiback_make_nexus(tpg, port_ptr);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+TF_TPG_BASE_ATTR(scsiback, nexus, S_IRUGO | S_IWUSR);
+
+static struct configfs_attribute *scsiback_tpg_attrs[] = {
+	&scsiback_tpg_nexus.attr,
+	NULL,
+};
+
+static ssize_t
+scsiback_wwn_show_attr_version(struct target_fabric_configfs *tf,
+				char *page)
+{
+	return sprintf(page, "xen-pvscsi fabric module %s on %s/%s on "
+		UTS_RELEASE"\n",
+		VSCSI_VERSION, utsname()->sysname, utsname()->machine);
+}
+
+TF_WWN_ATTR_RO(scsiback, version);
+
+static struct configfs_attribute *scsiback_wwn_attrs[] = {
+	&scsiback_wwn_version.attr,
+	NULL,
+};
+
+static char *scsiback_get_fabric_name(void)
+{
+	return "xen-pvscsi";
+}
+
+static int scsiback_port_link(struct se_portal_group *se_tpg,
+			       struct se_lun *lun)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count++;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	return 0;
+}
+
+static void scsiback_port_unlink(struct se_portal_group *se_tpg,
+				  struct se_lun *lun)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+}
+
+static struct se_portal_group *
+scsiback_make_tpg(struct se_wwn *wwn,
+		   struct config_group *group,
+		   const char *name)
+{
+	struct scsiback_tport *tport = container_of(wwn,
+			struct scsiback_tport, tport_wwn);
+
+	struct scsiback_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 scsiback_tpg), GFP_KERNEL);
+	if (!tpg)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_init(&tpg->tv_tpg_mutex);
+	INIT_LIST_HEAD(&tpg->tv_tpg_list);
+	INIT_LIST_HEAD(&tpg->info_list);
+	tpg->tport = tport;
+	tpg->tport_tpgt = tpgt;
+
+	ret = core_tpg_register(&scsiback_fabric_configfs->tf_ops, wwn,
+				&tpg->se_tpg, tpg, TRANSPORT_TPG_TYPE_NORMAL);
+	if (ret < 0) {
+		kfree(tpg);
+		return NULL;
+	}
+	mutex_lock(&scsiback_mutex);
+	list_add_tail(&tpg->tv_tpg_list, &scsiback_list);
+	mutex_unlock(&scsiback_mutex);
+
+	return &tpg->se_tpg;
+}
+
+static void scsiback_drop_tpg(struct se_portal_group *se_tpg)
+{
+	struct scsiback_tpg *tpg = container_of(se_tpg,
+				struct scsiback_tpg, se_tpg);
+
+	mutex_lock(&scsiback_mutex);
+	list_del(&tpg->tv_tpg_list);
+	mutex_unlock(&scsiback_mutex);
+	/*
+	 * Release the virtual I_T Nexus for this xen-pvscsi TPG
+	 */
+	scsiback_drop_nexus(tpg);
+	/*
+	 * Deregister the se_tpg from TCM..
+	 */
+	core_tpg_deregister(se_tpg);
+	kfree(tpg);
+}
+
+static int scsiback_check_true(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static int scsiback_check_false(struct se_portal_group *se_tpg)
+{
+	return 0;
+}
+
+static struct target_core_fabric_ops scsiback_ops = {
+	.get_fabric_name		= scsiback_get_fabric_name,
+	.get_fabric_proto_ident		= scsiback_get_fabric_proto_ident,
+	.tpg_get_wwn			= scsiback_get_fabric_wwn,
+	.tpg_get_tag			= scsiback_get_tag,
+	.tpg_get_default_depth		= scsiback_get_default_depth,
+	.tpg_get_pr_transport_id	= scsiback_get_pr_transport_id,
+	.tpg_get_pr_transport_id_len	= scsiback_get_pr_transport_id_len,
+	.tpg_parse_pr_out_transport_id	= scsiback_parse_pr_out_transport_id,
+	.tpg_check_demo_mode		= scsiback_check_true,
+	.tpg_check_demo_mode_cache	= scsiback_check_true,
+	.tpg_check_demo_mode_write_protect = scsiback_check_false,
+	.tpg_check_prod_mode_write_protect = scsiback_check_false,
+	.tpg_alloc_fabric_acl		= scsiback_alloc_fabric_acl,
+	.tpg_release_fabric_acl		= scsiback_release_fabric_acl,
+	.tpg_get_inst_index		= scsiback_tpg_get_inst_index,
+	.check_stop_free		= scsiback_check_stop_free,
+	.release_cmd			= scsiback_release_cmd,
+	.put_session			= NULL,
+	.shutdown_session		= scsiback_shutdown_session,
+	.close_session			= scsiback_close_session,
+	.sess_get_index			= scsiback_sess_get_index,
+	.sess_get_initiator_sid		= NULL,
+	.write_pending			= scsiback_write_pending,
+	.write_pending_status		= scsiback_write_pending_status,
+	.set_default_node_attributes	= scsiback_set_default_node_attrs,
+	.get_task_tag			= scsiback_get_task_tag,
+	.get_cmd_state			= scsiback_get_cmd_state,
+	.queue_data_in			= scsiback_queue_data_in,
+	.queue_status			= scsiback_queue_status,
+	.queue_tm_rsp			= scsiback_queue_tm_rsp,
+	.aborted_task			= scsiback_aborted_task,
+	/*
+	 * Setup callers for generic logic in target_core_fabric_configfs.c
+	 */
+	.fabric_make_wwn		= scsiback_make_tport,
+	.fabric_drop_wwn		= scsiback_drop_tport,
+	.fabric_make_tpg		= scsiback_make_tpg,
+	.fabric_drop_tpg		= scsiback_drop_tpg,
+	.fabric_post_link		= scsiback_port_link,
+	.fabric_pre_unlink		= scsiback_port_unlink,
+	.fabric_make_np			= NULL,
+	.fabric_drop_np			= NULL,
+#if 0
+	.fabric_make_nodeacl		= scsiback_make_nodeacl,
+	.fabric_drop_nodeacl		= scsiback_drop_nodeacl,
+#endif
+};
+
+static int scsiback_register_configfs(void)
+{
+	struct target_fabric_configfs *fabric;
+	int ret;
+
+	pr_debug("xen-pvscsi: fabric module %s on %s/%s on "UTS_RELEASE"\n",
+		 VSCSI_VERSION, utsname()->sysname, utsname()->machine);
+	/*
+	 * Register the top level struct config_item_type with TCM core
+	 */
+	fabric = target_fabric_configfs_init(THIS_MODULE, "xen-pvscsi");
+	if (IS_ERR(fabric))
+		return PTR_ERR(fabric);
+
+	/*
+	 * Setup fabric->tf_ops from our local scsiback_ops
+	 */
+	fabric->tf_ops = scsiback_ops;
+	/*
+	 * Setup default attribute lists for various fabric->tf_cit_tmpl
+	 */
+	fabric->tf_cit_tmpl.tfc_wwn_cit.ct_attrs = scsiback_wwn_attrs;
+	fabric->tf_cit_tmpl.tfc_tpg_base_cit.ct_attrs = scsiback_tpg_attrs;
+	fabric->tf_cit_tmpl.tfc_tpg_attrib_cit.ct_attrs = NULL;
+	fabric->tf_cit_tmpl.tfc_tpg_param_cit.ct_attrs = scsiback_param_attrs;
+	fabric->tf_cit_tmpl.tfc_tpg_np_base_cit.ct_attrs = NULL;
+	fabric->tf_cit_tmpl.tfc_tpg_nacl_base_cit.ct_attrs = NULL;
+	fabric->tf_cit_tmpl.tfc_tpg_nacl_attrib_cit.ct_attrs = NULL;
+	fabric->tf_cit_tmpl.tfc_tpg_nacl_auth_cit.ct_attrs = NULL;
+	fabric->tf_cit_tmpl.tfc_tpg_nacl_param_cit.ct_attrs = NULL;
+	/*
+	 * Register the fabric for use within TCM
+	 */
+	ret = target_fabric_configfs_register(fabric);
+	if (ret < 0) {
+		target_fabric_configfs_free(fabric);
+		return ret;
+	}
+	/*
+	 * Setup our local pointer to *fabric
+	 */
+	scsiback_fabric_configfs = fabric;
+	pr_debug("xen-pvscsi: Set fabric -> scsiback_fabric_configfs\n");
+	return 0;
+};
+
+static void scsiback_deregister_configfs(void)
+{
+	if (!scsiback_fabric_configfs)
+		return;
+
+	target_fabric_configfs_deregister(scsiback_fabric_configfs);
+	scsiback_fabric_configfs = NULL;
+	pr_debug("xen-pvscsi: Cleared scsiback_fabric_configfs\n");
+};
+
+static const struct xenbus_device_id scsiback_ids[] = {
+	{ "vscsi" },
+	{ "" }
+};
+
+static DEFINE_XENBUS_DRIVER(scsiback, ,
+	.probe			= scsiback_probe,
+	.remove			= scsiback_remove,
+	.otherend_changed	= scsiback_frontend_changed
+);
+
+static void scsiback_init_pend(void *p)
+{
+	struct vscsibk_pend *pend = p;
+	int i;
+
+	memset(pend, 0, sizeof(*pend));
+	for (i = 0; i < VSCSI_MAX_GRANTS; i++)
+		pend->grant_handles[i] = SCSIBACK_INVALID_HANDLE;
+}
+
+static int __init scsiback_init(void)
+{
+	int ret;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	scsiback_cachep = kmem_cache_create("vscsiif_cache",
+		sizeof(struct vscsibk_pend), 0, 0, scsiback_init_pend);
+	if (!scsiback_cachep)
+		return -ENOMEM;
+
+	ret = xenbus_register_backend(&scsiback_driver);
+	if (ret)
+		goto out_cache_destroy;
+
+	ret = scsiback_register_configfs();
+	if (ret)
+		goto out_unregister_xenbus;
+
+	return 0;
+
+out_unregister_xenbus:
+	xenbus_unregister_driver(&scsiback_driver);
+out_cache_destroy:
+	kmem_cache_destroy(scsiback_cachep);
+	pr_err("xen-pvscsi: %s: error %d\n", __func__, ret);
+	return ret;
+}
+
+static void __exit scsiback_exit(void)
+{
+	struct page *page;
+
+	while (free_pages_num) {
+		if (get_free_page(&page))
+			BUG();
+		free_xenballooned_pages(1, &page);
+	}
+	scsiback_deregister_configfs();
+	xenbus_unregister_driver(&scsiback_driver);
+	kmem_cache_destroy(scsiback_cachep);
+}
+
+module_init(scsiback_init);
+module_exit(scsiback_exit);
+
+MODULE_DESCRIPTION("Xen SCSI backend driver");
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS("xen-backend:vscsi");
+MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");