[PATCH V3 0/4] Add XEN pvSCSI support

[PATCH V3 0/4] Add XEN pvSCSI support

[jgross]

This series adds XEN pvSCSI support. With pvSCSI it is possible to use physical
SCSI devices from a XEN domain.

The support consists of a backend in the privileged Domain-0 doing the real
I/O and a frontend in the unprivileged domU passing I/O-requests to the backend.

The code is taken (and adapted) from the original pvSCSI implementation done
for Linux 2.6 in 2008 by Fujitsu.

[PATCH V2 1/4] Add XEN pvSCSI protocol description
[PATCH V2 2/4] Introduce xen-scsifront module
[PATCH V2 3/4] Introduce XEN scsiback module
[PATCH V2 4/4] add xen pvscsi maintainer

Changes in V3:
- added some comments to the protocol header file
- removed the CDB emulation from xen-scsiback, handled by core target
  infrastructure
- several changes in xen-scsifront after comments from Christoph Hellwig

Changes in V2:
- use core target infrastructure by backend instead of pure SCSI passthrough
- add support for larger SG lists by putting them in grant page(s)
- add command abort capability

[PATCH V3 1/4] Add XEN pvSCSI protocol description

[jgross]

From: Juergen Gross <jgross@suse.com>

Add the definition of pvSCSI protocol used between the pvSCSI frontend in a
XEN domU and the pvSCSI backend in a XEN driver domain (usually Dom0).

This header was originally provided by Fujitsu for XEN based on Linux 2.6.18.
Changes are:
- added comment
- adapt to Linux style guide
- add support for larger SG-lists by putting them in an own granted page
- remove stale definitions

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 include/xen/interface/io/vscsiif.h | 208 +++++++++++++++++++++++++++++++++++++
 1 file changed, 208 insertions(+)
 create mode 100644 include/xen/interface/io/vscsiif.h

diff --git a/include/xen/interface/io/vscsiif.h b/include/xen/interface/io/vscsiif.h
new file mode 100644
index 0000000..ead1c0b
--- /dev/null
+++ b/include/xen/interface/io/vscsiif.h
@@ -0,0 +1,208 @@
+/******************************************************************************
+ * vscsiif.h
+ *
+ * Based on the blkif.h code.
+ *
+ * This interface is to be regarded as a stable API between XEN domains
+ * running potentially different Linux kernel versions.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (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.
+ *
+ * Copyright(c) FUJITSU Limited 2008.
+ */
+
+#ifndef __XEN__PUBLIC_IO_SCSI_H__
+#define __XEN__PUBLIC_IO_SCSI_H__
+
+#include "ring.h"
+#include "../grant_table.h"
+
+/*
+ * Front->back notifications: When enqueuing a new request, sending a
+ * notification can be made conditional on req_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Backends must set
+ * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
+ *
+ * Back->front notifications: When enqueuing a new response, sending a
+ * notification can be made conditional on rsp_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Frontends must set
+ * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
+ */
+
+/*
+ * Feature and Parameter Negotiation
+ * =================================
+ * The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to
+ * communicate capabilities and to negotiate operating parameters.  This
+ * section enumerates these nodes which reside in the respective front and
+ * backend portions of the XenStore, following the XenBus convention.
+ *
+ * All data in the XenStore is stored as strings.  Nodes specifying numeric
+ * values are encoded in decimal.  Integer value ranges listed below are
+ * expressed as fixed sized integer types capable of storing the conversion
+ * of a properly formated node string, without loss of information.
+ *
+ * Any specified default value is in effect if the corresponding XenBus node
+ * is not present in the XenStore.
+ *
+ * XenStore nodes in sections marked "PRIVATE" are solely for use by the
+ * driver side whose XenBus tree contains them.
+ *
+ *****************************************************************************
+ *                            Backend XenBus Nodes
+ *****************************************************************************
+ *
+ *------------------ Backend Device Identification (PRIVATE) ------------------
+ *
+ * p-devname
+ *      Values:         string
+ *
+ *      A free string used to identify the physical device (e.g. a disk name).
+ *
+ * p-dev
+ *      Values:         string
+ *
+ *      A string specifying the backend device: either a 4-tuple "h:c:t:l"
+ *      (host, controller, target, lun, all integers), or a WWN (e.g.
+ *      "naa.60014054ac780582").
+ *
+ * v-dev
+ *      Values:         string
+ *
+ *      A string specifying the frontend device in form of a 4-tuple "h:c:t:l"
+ *      (host, controller, target, lun, all integers).
+ *
+ *--------------------------------- Features ---------------------------------
+ *
+ * feature-sg-grant
+ *      Values:         <uint16_t>
+ *      Default Value:  0
+ *
+ *      Specifies the maximum number of scatter/gather elements in grant pages
+ *      supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE
+ *      SG elements specified directly in the request.
+ *
+ *****************************************************************************
+ *                            Frontend XenBus Nodes
+ *****************************************************************************
+ *
+ *----------------------- Request Transport Parameters -----------------------
+ *
+ * event-channel
+ *      Values:         <uint32_t>
+ *
+ *      The identifier of the Xen event channel used to signal activity
+ *      in the ring buffer.
+ *
+ * ring-ref
+ *      Values:         <uint32_t>
+ *
+ * protocol
+ *      Values:         string (XEN_IO_PROTO_ABI_*)
+ *      Default Value:  XEN_IO_PROTO_ABI_NATIVE
+ *
+ *      The machine ABI rules governing the format of all ring request and
+ *      response structures.
+ */
+
+/* Requests from the frontend to the backend */
+
+/*
+ * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
+ * The target is specified via channel, id and lun.
+ */
+#define VSCSIIF_ACT_SCSI_CDB		1
+
+/*
+ * Request abort of a running operation for the specified target given by
+ * channel, id, lun and the operation's rqid in ref_rqid.
+ */
+#define VSCSIIF_ACT_SCSI_ABORT		2
+
+/*
+ * Request a device reset of the specified target (channel and id).
+ */
+#define VSCSIIF_ACT_SCSI_RESET		3
+
+/*
+ * Maximum scatter/gather segments per request.
+ *
+ * Considering balance between allocating at least 16 "vscsiif_request"
+ * structures on one page (4096 bytes) and the number of scatter/gather
+ * elements needed, we decided to use 26 as a magic number.
+ *
+ * If "feature-sg-grant" is set, more scatter/gather elements can be specified
+ * by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages.
+ * In this case the vscsiif_request seg elements don't contain references to
+ * the user data, but to the SG elements referencing the user data.
+ */
+#define VSCSIIF_SG_TABLESIZE		26
+
+/*
+ * based on Linux kernel 2.6.18, still valid
+ * Changing these values requires support of multiple protocols via the rings
+ * as "old clients" will blindly use these values and the resulting structure
+ * sizes.
+ */
+#define VSCSIIF_MAX_COMMAND_SIZE	16
+#define VSCSIIF_SENSE_BUFFERSIZE	96
+
+struct scsiif_request_segment {
+	grant_ref_t gref;
+	uint16_t offset;
+	uint16_t length;
+};
+
+/* Size of one request is 252 bytes */
+struct vscsiif_request {
+	uint16_t rqid;		/* private guest value, echoed in resp  */
+	uint8_t act;		/* command between backend and frontend */
+	uint8_t cmd_len;	/* valid CDB bytes */
+
+	uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE];	/* the CDB */
+	uint16_t timeout_per_command;
+	uint16_t channel, id, lun;	/* (virtual) device specification */
+	uint16_t ref_rqid;		/* command abort reference */
+	uint8_t sc_data_direction;	/* for DMA_TO_DEVICE(1)
+					   DMA_FROM_DEVICE(2)
+					   DMA_NONE(3) requests */
+	uint8_t nr_segments;		/* Number of pieces of scatter-gather */
+#define VSCSIIF_SG_GRANT	0x80	/* flag: SG elements via grant page */
+					/* nr_segments counts grant pages with
+					   SG elements
+					   usable if "feature-sg-grant" set */
+
+	struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
+	uint32_t reserved[3];
+};
+
+struct vscsiif_response {
+	uint16_t rqid;		/* identifies request */
+	uint8_t padding;
+	uint8_t sense_len;
+	uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
+	int32_t rslt;
+	uint32_t residual_len;	/* request bufflen -
+				   return the value from physical device */
+	uint32_t reserved[36];
+};
+
+DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response);
+
+#endif /*__XEN__PUBLIC_IO_SCSI_H__*/
-- 
1.8.4.5

[PATCH V3 1/4] Add XEN pvSCSI protocol description

[jgross]

From: Juergen Gross <jgross@suse.com>

Add the definition of pvSCSI protocol used between the pvSCSI frontend in a
XEN domU and the pvSCSI backend in a XEN driver domain (usually Dom0).

This header was originally provided by Fujitsu for XEN based on Linux 2.6.18.
Changes are:
- added comment
- adapt to Linux style guide
- add support for larger SG-lists by putting them in an own granted page
- remove stale definitions

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 include/xen/interface/io/vscsiif.h | 208 +++++++++++++++++++++++++++++++++++++
 1 file changed, 208 insertions(+)
 create mode 100644 include/xen/interface/io/vscsiif.h

diff --git a/include/xen/interface/io/vscsiif.h b/include/xen/interface/io/vscsiif.h
new file mode 100644
index 0000000..ead1c0b
--- /dev/null
+++ b/include/xen/interface/io/vscsiif.h
@@ -0,0 +1,208 @@
+/******************************************************************************
+ * vscsiif.h
+ *
+ * Based on the blkif.h code.
+ *
+ * This interface is to be regarded as a stable API between XEN domains
+ * running potentially different Linux kernel versions.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (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.
+ *
+ * Copyright(c) FUJITSU Limited 2008.
+ */
+
+#ifndef __XEN__PUBLIC_IO_SCSI_H__
+#define __XEN__PUBLIC_IO_SCSI_H__
+
+#include "ring.h"
+#include "../grant_table.h"
+
+/*
+ * Front->back notifications: When enqueuing a new request, sending a
+ * notification can be made conditional on req_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Backends must set
+ * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
+ *
+ * Back->front notifications: When enqueuing a new response, sending a
+ * notification can be made conditional on rsp_event (i.e., the generic
+ * hold-off mechanism provided by the ring macros). Frontends must set
+ * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
+ */
+
+/*
+ * Feature and Parameter Negotiation
+ * =================================
+ * The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to
+ * communicate capabilities and to negotiate operating parameters.  This
+ * section enumerates these nodes which reside in the respective front and
+ * backend portions of the XenStore, following the XenBus convention.
+ *
+ * All data in the XenStore is stored as strings.  Nodes specifying numeric
+ * values are encoded in decimal.  Integer value ranges listed below are
+ * expressed as fixed sized integer types capable of storing the conversion
+ * of a properly formated node string, without loss of information.
+ *
+ * Any specified default value is in effect if the corresponding XenBus node
+ * is not present in the XenStore.
+ *
+ * XenStore nodes in sections marked "PRIVATE" are solely for use by the
+ * driver side whose XenBus tree contains them.
+ *
+ *****************************************************************************
+ *                            Backend XenBus Nodes
+ *****************************************************************************
+ *
+ *------------------ Backend Device Identification (PRIVATE) ------------------
+ *
+ * p-devname
+ *      Values:         string
+ *
+ *      A free string used to identify the physical device (e.g. a disk name).
+ *
+ * p-dev
+ *      Values:         string
+ *
+ *      A string specifying the backend device: either a 4-tuple "h:c:t:l"
+ *      (host, controller, target, lun, all integers), or a WWN (e.g.
+ *      "naa.60014054ac780582").
+ *
+ * v-dev
+ *      Values:         string
+ *
+ *      A string specifying the frontend device in form of a 4-tuple "h:c:t:l"
+ *      (host, controller, target, lun, all integers).
+ *
+ *--------------------------------- Features ---------------------------------
+ *
+ * feature-sg-grant
+ *      Values:         <uint16_t>
+ *      Default Value:  0
+ *
+ *      Specifies the maximum number of scatter/gather elements in grant pages
+ *      supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE
+ *      SG elements specified directly in the request.
+ *
+ *****************************************************************************
+ *                            Frontend XenBus Nodes
+ *****************************************************************************
+ *
+ *----------------------- Request Transport Parameters -----------------------
+ *
+ * event-channel
+ *      Values:         <uint32_t>
+ *
+ *      The identifier of the Xen event channel used to signal activity
+ *      in the ring buffer.
+ *
+ * ring-ref
+ *      Values:         <uint32_t>
+ *
+ * protocol
+ *      Values:         string (XEN_IO_PROTO_ABI_*)
+ *      Default Value:  XEN_IO_PROTO_ABI_NATIVE
+ *
+ *      The machine ABI rules governing the format of all ring request and
+ *      response structures.
+ */
+
+/* Requests from the frontend to the backend */
+
+/*
+ * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
+ * The target is specified via channel, id and lun.
+ */
+#define VSCSIIF_ACT_SCSI_CDB		1
+
+/*
+ * Request abort of a running operation for the specified target given by
+ * channel, id, lun and the operation's rqid in ref_rqid.
+ */
+#define VSCSIIF_ACT_SCSI_ABORT		2
+
+/*
+ * Request a device reset of the specified target (channel and id).
+ */
+#define VSCSIIF_ACT_SCSI_RESET		3
+
+/*
+ * Maximum scatter/gather segments per request.
+ *
+ * Considering balance between allocating at least 16 "vscsiif_request"
+ * structures on one page (4096 bytes) and the number of scatter/gather
+ * elements needed, we decided to use 26 as a magic number.
+ *
+ * If "feature-sg-grant" is set, more scatter/gather elements can be specified
+ * by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages.
+ * In this case the vscsiif_request seg elements don't contain references to
+ * the user data, but to the SG elements referencing the user data.
+ */
+#define VSCSIIF_SG_TABLESIZE		26
+
+/*
+ * based on Linux kernel 2.6.18, still valid
+ * Changing these values requires support of multiple protocols via the rings
+ * as "old clients" will blindly use these values and the resulting structure
+ * sizes.
+ */
+#define VSCSIIF_MAX_COMMAND_SIZE	16
+#define VSCSIIF_SENSE_BUFFERSIZE	96
+
+struct scsiif_request_segment {
+	grant_ref_t gref;
+	uint16_t offset;
+	uint16_t length;
+};
+
+/* Size of one request is 252 bytes */
+struct vscsiif_request {
+	uint16_t rqid;		/* private guest value, echoed in resp  */
+	uint8_t act;		/* command between backend and frontend */
+	uint8_t cmd_len;	/* valid CDB bytes */
+
+	uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE];	/* the CDB */
+	uint16_t timeout_per_command;
+	uint16_t channel, id, lun;	/* (virtual) device specification */
+	uint16_t ref_rqid;		/* command abort reference */
+	uint8_t sc_data_direction;	/* for DMA_TO_DEVICE(1)
+					   DMA_FROM_DEVICE(2)
+					   DMA_NONE(3) requests */
+	uint8_t nr_segments;		/* Number of pieces of scatter-gather */
+#define VSCSIIF_SG_GRANT	0x80	/* flag: SG elements via grant page */
+					/* nr_segments counts grant pages with
+					   SG elements
+					   usable if "feature-sg-grant" set */
+
+	struct scsiif_request_segment seg[VSCSIIF_SG_TABLESIZE];
+	uint32_t reserved[3];
+};
+
+struct vscsiif_response {
+	uint16_t rqid;		/* identifies request */
+	uint8_t padding;
+	uint8_t sense_len;
+	uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
+	int32_t rslt;
+	uint32_t residual_len;	/* request bufflen -
+				   return the value from physical device */
+	uint32_t reserved[36];
+};
+
+DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response);
+
+#endif /*__XEN__PUBLIC_IO_SCSI_H__*/
-- 
1.8.4.5

[PATCH V3 2/4] Introduce xen-scsifront module

[jgross]

From: Juergen Gross <jgross@suse.com>

Introduces the XEN pvSCSI frontend. 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
- move module to appropriate location in kernel tree
- adapt to Linux style guide
- some minor code simplifications
- replace constants with defines
- remove not used defines
- add support for larger SG lists by putting them in a granted page

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/scsi/Kconfig         |    9 +
 drivers/scsi/Makefile        |    1 +
 drivers/scsi/xen-scsifront.c | 1011 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1021 insertions(+)
 create mode 100644 drivers/scsi/xen-scsifront.c

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index baca589..e860c16 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -611,6 +611,15 @@ config VMWARE_PVSCSI
 	  To compile this driver as a module, choose M here: the
 	  module will be called vmw_pvscsi.
 
+config XEN_SCSI_FRONTEND
+	tristate "XEN SCSI frontend driver"
+	depends on SCSI && XEN
+	help
+	  The XEN SCSI frontend driver allows the kernel to access SCSI Devices
+	  within another guest OS (usually Dom0).
+	  Only needed if the kernel is running in a XEN guest and generic
+	  SCSI access to a device is needed.
+
 config HYPERV_STORAGE
 	tristate "Microsoft Hyper-V virtual storage driver"
 	depends on SCSI && HYPERV
diff --git a/drivers/scsi/Makefile b/drivers/scsi/Makefile
index e172d4f..a4ee9c5 100644
--- a/drivers/scsi/Makefile
+++ b/drivers/scsi/Makefile
@@ -144,6 +144,7 @@ obj-$(CONFIG_SCSI_ESAS2R)	+= esas2r/
 obj-$(CONFIG_SCSI_PMCRAID)	+= pmcraid.o
 obj-$(CONFIG_SCSI_VIRTIO)	+= virtio_scsi.o
 obj-$(CONFIG_VMWARE_PVSCSI)	+= vmw_pvscsi.o
+obj-$(CONFIG_XEN_SCSI_FRONTEND)	+= xen-scsifront.o
 obj-$(CONFIG_HYPERV_STORAGE)	+= hv_storvsc.o
 
 obj-$(CONFIG_ARM)		+= arm/
diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
new file mode 100644
index 0000000..7c60c68
--- /dev/null
+++ b/drivers/scsi/xen-scsifront.c
@@ -0,0 +1,1011 @@
+/*
+ * Xen SCSI frontend driver
+ *
+ * Copyright (c) 2008, FUJITSU Limited
+ *
+ * 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.
+ */
+
+#define DEBUG
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/wait.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+#include <linux/blkdev.h>
+#include <linux/pfn.h>
+#include <linux/slab.h>
+
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_host.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/page.h>
+
+#include <xen/interface/grant_table.h>
+#include <xen/interface/io/vscsiif.h>
+#include <xen/interface/io/protocols.h>
+
+#include <asm/xen/hypervisor.h>
+
+
+#define GRANT_INVALID_REF	0
+
+#define VSCSIFRONT_OP_ADD_LUN	1
+#define VSCSIFRONT_OP_DEL_LUN	2
+
+#define DEFAULT_TASK_COMM_LEN	TASK_COMM_LEN
+
+/* tuning point*/
+#define VSCSIIF_DEFAULT_CMD_PER_LUN 10
+#define VSCSIIF_MAX_TARGET          64
+#define VSCSIIF_MAX_LUN             255
+
+#define VSCSIIF_RING_SIZE	__CONST_RING_SIZE(vscsiif, PAGE_SIZE)
+#define VSCSIIF_MAX_REQS	VSCSIIF_RING_SIZE
+
+#define vscsiif_grants_sg(_sg)	(PFN_UP((_sg) *		\
+				sizeof(struct scsiif_request_segment)))
+
+struct vscsifrnt_shadow {
+	/* command between backend and frontend */
+	unsigned char act;
+	uint16_t rqid;
+
+	/* Number of pieces of scatter-gather */
+	unsigned int nr_grants;
+	struct scsiif_request_segment *sg;
+
+	/* do reset or abort function */
+	wait_queue_head_t wq_reset;	/* reset work queue           */
+	int wait_reset;			/* reset work queue condition */
+	int32_t rslt_reset;		/* reset response status      */
+					/* (SUCESS or FAILED)         */
+
+	/* requested struct scsi_cmnd is stored from kernel */
+	struct scsi_cmnd *sc;
+	int gref[vscsiif_grants_sg(SG_ALL) + SG_ALL];
+};
+
+struct vscsifrnt_info {
+	struct xenbus_device *dev;
+
+	struct Scsi_Host *host;
+	int host_active;
+
+	spinlock_t shadow_lock;
+	unsigned int evtchn;
+	unsigned int irq;
+
+	grant_ref_t ring_ref;
+	struct vscsiif_front_ring ring;
+	struct vscsiif_response	ring_res;
+
+	unsigned long shadow_free;
+	struct vscsifrnt_shadow *shadow[VSCSIIF_MAX_REQS];
+
+	wait_queue_head_t wq_sync;
+	unsigned int waiting_sync:1;
+};
+
+#define DPRINTK(_f, _a...)				\
+	pr_debug("(file=%s, line=%d) " _f, __FILE__ , __LINE__ , ## _a)
+
+#define PREFIX(lvl) KERN_##lvl "scsifront: "
+
+static void scsifront_wake_up(struct vscsifrnt_info *info)
+{
+	info->waiting_sync = 0;
+	wake_up(&info->wq_sync);
+}
+
+static int scsifront_get_rqid(struct vscsifrnt_info *info)
+{
+	unsigned long flags;
+	int free;
+
+	spin_lock_irqsave(&info->shadow_lock, flags);
+
+	free = find_first_bit(&info->shadow_free, VSCSIIF_MAX_REQS);
+	info->shadow_free &= ~(1UL << free);
+
+	spin_unlock_irqrestore(&info->shadow_lock, flags);
+
+	return free;
+}
+
+static int _scsifront_put_rqid(struct vscsifrnt_info *info, uint32_t id)
+{
+	info->shadow_free |= 1UL << id;
+	info->shadow[id] = NULL;
+
+	return (info->shadow_free == 1UL << id || info->waiting_sync);
+}
+
+static void scsifront_put_rqid(struct vscsifrnt_info *info, uint32_t id)
+{
+	unsigned long flags;
+	int was_empty;
+
+	spin_lock_irqsave(&info->shadow_lock, flags);
+	was_empty = _scsifront_put_rqid(info, id);
+	spin_unlock_irqrestore(&info->shadow_lock, flags);
+
+	if (was_empty)
+		scsifront_wake_up(info);
+}
+
+static struct vscsiif_request *scsifront_pre_req(struct vscsifrnt_info *info)
+{
+	struct vscsiif_front_ring *ring = &(info->ring);
+	struct vscsiif_request *ring_req;
+	uint32_t id;
+
+	id = scsifront_get_rqid(info);	/* use id by response */
+	if (id >= VSCSIIF_MAX_REQS)
+		return NULL;
+
+	ring_req = RING_GET_REQUEST(&(info->ring), ring->req_prod_pvt);
+
+	ring->req_prod_pvt++;
+
+	ring_req->rqid = (uint16_t)id;
+
+	return ring_req;
+}
+
+static void scsifront_do_request(struct vscsifrnt_info *info)
+{
+	struct vscsiif_front_ring *ring = &(info->ring);
+	int notify;
+
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(ring, notify);
+	if (notify)
+		notify_remote_via_irq(info->irq);
+}
+
+static void scsifront_gnttab_done(struct vscsifrnt_info *info, uint32_t id)
+{
+	struct vscsifrnt_shadow *s = info->shadow[id];
+	int i;
+
+	if (s->sc->sc_data_direction == DMA_NONE)
+		return;
+
+	for (i = 0; i < s->nr_grants; i++) {
+		if (unlikely(gnttab_query_foreign_access(s->gref[i]) != 0)) {
+			shost_printk(PREFIX(ALERT), info->host,
+				     "grant still in use by backend\n");
+			BUG();
+		}
+		gnttab_end_foreign_access(s->gref[i], 0, 0UL);
+	}
+
+	kfree(s->sg);
+}
+
+static void scsifront_cdb_cmd_done(struct vscsifrnt_info *info,
+				   struct vscsiif_response *ring_res)
+{
+	struct scsi_cmnd *sc;
+	uint32_t id;
+	uint8_t sense_len;
+
+	id = ring_res->rqid;
+	sc = info->shadow[id]->sc;
+
+	BUG_ON(sc == NULL);
+
+	scsifront_gnttab_done(info, id);
+	scsifront_put_rqid(info, id);
+
+	sc->result = ring_res->rslt;
+	scsi_set_resid(sc, ring_res->residual_len);
+
+	sense_len = min_t(uint8_t, VSCSIIF_SENSE_BUFFERSIZE,
+			  ring_res->sense_len);
+
+	if (sense_len)
+		memcpy(sc->sense_buffer, ring_res->sense_buffer, sense_len);
+
+	sc->scsi_done(sc);
+}
+
+static void scsifront_sync_cmd_done(struct vscsifrnt_info *info,
+				    struct vscsiif_response *ring_res)
+{
+	uint16_t id = ring_res->rqid;
+	unsigned long flags;
+	struct vscsifrnt_shadow *shadow = info->shadow[id];
+	int was_empty;
+
+	spin_lock_irqsave(&info->shadow_lock, flags);
+	shadow->wait_reset = 1;
+	switch (shadow->rslt_reset) {
+	case 0:
+		shadow->rslt_reset = ring_res->rslt;
+		break;
+	case -1:
+		was_empty = _scsifront_put_rqid(info, id);
+		spin_unlock_irqrestore(&info->shadow_lock, flags);
+		kfree(shadow);
+		if (was_empty)
+			scsifront_wake_up(info);
+		return;
+	default:
+		shost_printk(PREFIX(ERR), info->host,
+			     "bad reset state %d, possibly leaking %u\n",
+			     shadow->rslt_reset, id);
+		break;
+	}
+	spin_unlock_irqrestore(&info->shadow_lock, flags);
+
+	wake_up(&shadow->wq_reset);
+}
+
+static int scsifront_cmd_done(struct vscsifrnt_info *info)
+{
+	struct vscsiif_response *ring_res;
+	RING_IDX i, rp;
+	int more_to_do = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(info->host->host_lock, flags);
+
+	rp = info->ring.sring->rsp_prod;
+	rmb();	/* ordering required respective to dom0 */
+	for (i = info->ring.rsp_cons; i != rp; i++) {
+
+		ring_res = RING_GET_RESPONSE(&info->ring, i);
+
+		if (info->shadow[ring_res->rqid]->act == VSCSIIF_ACT_SCSI_CDB)
+			scsifront_cdb_cmd_done(info, ring_res);
+		else
+			scsifront_sync_cmd_done(info, ring_res);
+	}
+
+	info->ring.rsp_cons = i;
+
+	if (i != info->ring.req_prod_pvt)
+		RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
+	else
+		info->ring.sring->rsp_event = i + 1;
+
+	info->waiting_sync = 0;
+
+	spin_unlock_irqrestore(info->host->host_lock, flags);
+
+	wake_up(&info->wq_sync);
+
+	return more_to_do;
+}
+
+static irqreturn_t scsifront_irq_fn(int irq, void *dev_id)
+{
+	struct vscsifrnt_info *info = dev_id;
+
+	while (scsifront_cmd_done(info))
+		/* Yield point for this unbounded loop. */
+		cond_resched();
+
+	return IRQ_HANDLED;
+}
+
+static int map_data_for_request(struct vscsifrnt_info *info,
+				struct scsi_cmnd *sc,
+				struct vscsiif_request *ring_req,
+				struct vscsifrnt_shadow *shadow)
+{
+	grant_ref_t gref_head;
+	struct page *page;
+	int err, ref, ref_cnt = 0;
+	int write = (sc->sc_data_direction == DMA_TO_DEVICE);
+	unsigned int i, off, len, bytes;
+	unsigned int data_len = scsi_bufflen(sc);
+	unsigned int data_grants = 0, seg_grants = 0;
+	struct scatterlist *sg;
+	unsigned long mfn;
+	struct scsiif_request_segment *seg;
+
+	ring_req->nr_segments = 0;
+	if (sc->sc_data_direction == DMA_NONE || !data_len)
+		return 0;
+
+	scsi_for_each_sg(sc, sg, scsi_sg_count(sc), i)
+		data_grants += PFN_UP(sg->offset + sg->length);
+
+	if (data_grants > VSCSIIF_SG_TABLESIZE) {
+		if (data_grants > info->host->sg_tablesize) {
+			shost_printk(PREFIX(ERR), info->host,
+			     "Unable to map request_buffer for command!\n");
+			return -E2BIG;
+		}
+		seg_grants = vscsiif_grants_sg(data_grants);
+		shadow->sg = kcalloc(data_grants,
+			sizeof(struct scsiif_request_segment), GFP_NOIO);
+		if (!shadow->sg)
+			return -ENOMEM;
+	}
+	seg = shadow->sg ? : ring_req->seg;
+
+	err = gnttab_alloc_grant_references(seg_grants + data_grants,
+					    &gref_head);
+	if (err) {
+		kfree(shadow->sg);
+		shost_printk(PREFIX(ERR), info->host,
+			     "gnttab_alloc_grant_references() error\n");
+		return -ENOMEM;
+	}
+
+	if (seg_grants) {
+		page = virt_to_page(seg);
+		off = (unsigned long)seg & ~PAGE_MASK;
+		len = sizeof(struct scsiif_request_segment) * data_grants;
+		while (len > 0) {
+			bytes = min_t(unsigned int, len, PAGE_SIZE - off);
+
+			ref = gnttab_claim_grant_reference(&gref_head);
+			BUG_ON(ref == -ENOSPC);
+
+			mfn = pfn_to_mfn(page_to_pfn(page));
+			gnttab_grant_foreign_access_ref(ref,
+				info->dev->otherend_id, mfn, 1);
+			shadow->gref[ref_cnt] = ref;
+			ring_req->seg[ref_cnt].gref   = ref;
+			ring_req->seg[ref_cnt].offset = (uint16_t)off;
+			ring_req->seg[ref_cnt].length = (uint16_t)bytes;
+
+			page++;
+			len -= bytes;
+			off = 0;
+			ref_cnt++;
+		}
+		BUG_ON(seg_grants < ref_cnt);
+		seg_grants = ref_cnt;
+	}
+
+	scsi_for_each_sg(sc, sg, scsi_sg_count(sc), i) {
+		page = sg_page(sg);
+		off = sg->offset;
+		len = sg->length;
+
+		while (len > 0 && data_len > 0) {
+			/*
+			 * sg sends a scatterlist that is larger than
+			 * the data_len it wants transferred for certain
+			 * IO sizes
+			 */
+			bytes = min_t(unsigned int, len, PAGE_SIZE - off);
+			bytes = min(bytes, data_len);
+
+			ref = gnttab_claim_grant_reference(&gref_head);
+			BUG_ON(ref == -ENOSPC);
+
+			mfn = pfn_to_mfn(page_to_pfn(page));
+			gnttab_grant_foreign_access_ref(ref,
+				info->dev->otherend_id, mfn, write);
+
+			shadow->gref[ref_cnt] = ref;
+			seg->gref   = ref;
+			seg->offset = (uint16_t)off;
+			seg->length = (uint16_t)bytes;
+
+			page++;
+			seg++;
+			len -= bytes;
+			data_len -= bytes;
+			off = 0;
+			ref_cnt++;
+		}
+	}
+
+	if (seg_grants)
+		ring_req->nr_segments = VSCSIIF_SG_GRANT | seg_grants;
+	else
+		ring_req->nr_segments = (uint8_t)ref_cnt;
+	shadow->nr_grants = ref_cnt;
+
+	return 0;
+}
+
+static struct vscsiif_request *scsifront_command2ring(
+		struct vscsifrnt_info *info, struct scsi_cmnd *sc,
+		struct vscsifrnt_shadow *shadow)
+{
+	struct vscsiif_request *ring_req;
+
+	memset(shadow, 0, sizeof(*shadow));
+
+	ring_req = scsifront_pre_req(info);
+	if (!ring_req)
+		return NULL;
+
+	info->shadow[ring_req->rqid] = shadow;
+	shadow->rqid = ring_req->rqid;
+
+	ring_req->id      = sc->device->id;
+	ring_req->lun     = sc->device->lun;
+	ring_req->channel = sc->device->channel;
+	ring_req->cmd_len = sc->cmd_len;
+
+	BUG_ON(sc->cmd_len > VSCSIIF_MAX_COMMAND_SIZE);
+
+	if (sc->cmd_len)
+		memcpy(ring_req->cmnd, sc->cmnd, sc->cmd_len);
+	else
+		memset(ring_req->cmnd, 0, VSCSIIF_MAX_COMMAND_SIZE);
+
+	ring_req->sc_data_direction   = (uint8_t)sc->sc_data_direction;
+	ring_req->timeout_per_command = sc->request->timeout / HZ;
+
+	return ring_req;
+}
+
+static int scsifront_queuecommand(struct Scsi_Host *shost,
+				  struct scsi_cmnd *sc)
+{
+	struct vscsifrnt_info *info = shost_priv(shost);
+	struct vscsiif_request *ring_req;
+	struct vscsifrnt_shadow *shadow = scsi_cmd_priv(sc);
+	unsigned long flags;
+	int err;
+	uint16_t rqid;
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	if (RING_FULL(&info->ring))
+		goto busy;
+
+	ring_req = scsifront_command2ring(info, sc, shadow);
+	if (!ring_req)
+		goto busy;
+
+	sc->result    = 0;
+
+	rqid              = ring_req->rqid;
+	ring_req->act     = VSCSIIF_ACT_SCSI_CDB;
+
+	shadow->sc  = sc;
+	shadow->act = VSCSIIF_ACT_SCSI_CDB;
+
+	err = map_data_for_request(info, sc, ring_req, shadow);
+	if (err < 0) {
+		DPRINTK("%s: err %d\n", __func__, err);
+		scsifront_put_rqid(info, rqid);
+		spin_unlock_irqrestore(shost->host_lock, flags);
+		if (err == -ENOMEM)
+			return SCSI_MLQUEUE_HOST_BUSY;
+		sc->result = DID_ERROR << 16;
+		sc->scsi_done(sc);
+		return 0;
+	}
+
+	scsifront_do_request(info);
+	spin_unlock_irqrestore(shost->host_lock, flags);
+
+	return 0;
+
+busy:
+	spin_unlock_irqrestore(shost->host_lock, flags);
+	DPRINTK("%s: busy\n", __func__);
+	return SCSI_MLQUEUE_HOST_BUSY;
+}
+
+static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
+{
+	struct Scsi_Host *host = sc->device->host;
+	struct vscsifrnt_info *info = shost_priv(host);
+	struct vscsifrnt_shadow *shadow, *s = scsi_cmd_priv(sc);
+	struct vscsiif_request *ring_req;
+	int err = 0;
+
+	shadow = kmalloc(sizeof(*shadow), GFP_NOIO);
+	if (!shadow)
+		return FAILED;
+
+	for (;;) {
+		spin_lock_irq(host->host_lock);
+		if (!RING_FULL(&info->ring)) {
+			ring_req = scsifront_command2ring(info, sc, shadow);
+			if (ring_req)
+				break;
+		}
+		if (err) {
+			spin_unlock_irq(host->host_lock);
+			kfree(shadow);
+			return FAILED;
+		}
+		info->waiting_sync = 1;
+		spin_unlock_irq(host->host_lock);
+		err = wait_event_interruptible(info->wq_sync,
+					       !info->waiting_sync);
+		spin_lock_irq(host->host_lock);
+	}
+
+	ring_req->act = act;
+	ring_req->ref_rqid = s->rqid;
+
+	shadow->act = act;
+	shadow->rslt_reset = 0;
+	init_waitqueue_head(&shadow->wq_reset);
+
+	ring_req->nr_segments         = 0;
+
+	scsifront_do_request(info);
+
+	spin_unlock_irq(host->host_lock);
+	err = wait_event_interruptible(shadow->wq_reset, shadow->wait_reset);
+	spin_lock_irq(host->host_lock);
+
+	if (!err) {
+		err = shadow->rslt_reset;
+		scsifront_put_rqid(info, shadow->rqid);
+		kfree(shadow);
+	} else {
+		spin_lock(&info->shadow_lock);
+		shadow->rslt_reset = -1;
+		spin_unlock(&info->shadow_lock);
+		err = FAILED;
+	}
+
+	spin_unlock_irq(host->host_lock);
+	return err;
+}
+
+static int scsifront_eh_abort_handler(struct scsi_cmnd *sc)
+{
+	DPRINTK("%s\n", __func__);
+	return scsifront_action_handler(sc, VSCSIIF_ACT_SCSI_ABORT);
+}
+
+static int scsifront_dev_reset_handler(struct scsi_cmnd *sc)
+{
+	DPRINTK("%s\n", __func__);
+	return scsifront_action_handler(sc, VSCSIIF_ACT_SCSI_RESET);
+}
+
+static int scsifront_sdev_alloc(struct scsi_device *sdev)
+{
+	/* set hostdata to not NULL indicating new allocation */
+	sdev->hostdata = sdev;
+	return 0;
+}
+
+static struct scsi_host_template scsifront_sht = {
+	.module			= THIS_MODULE,
+	.name			= "Xen SCSI frontend driver",
+	.queuecommand		= scsifront_queuecommand,
+	.eh_abort_handler	= scsifront_eh_abort_handler,
+	.eh_device_reset_handler = scsifront_dev_reset_handler,
+	.slave_alloc		= scsifront_sdev_alloc,
+	.cmd_per_lun		= VSCSIIF_DEFAULT_CMD_PER_LUN,
+	.can_queue		= VSCSIIF_MAX_REQS,
+	.this_id		= -1,
+	.cmd_size		= sizeof(struct vscsifrnt_shadow),
+	.sg_tablesize		= VSCSIIF_SG_TABLESIZE,
+	.use_clustering		= DISABLE_CLUSTERING,
+	.proc_name		= "scsifront",
+};
+
+static void scsifront_free(struct vscsifrnt_info *info)
+{
+	if (info->host && info->host_active) {
+		/* Scsi_host not yet removed */
+		scsi_remove_host(info->host);
+		info->host_active = 0;
+	}
+
+	if (info->ring_ref != GRANT_INVALID_REF) {
+		gnttab_end_foreign_access(info->ring_ref, 0,
+					  (unsigned long)info->ring.sring);
+		info->ring_ref = GRANT_INVALID_REF;
+		info->ring.sring = NULL;
+	}
+
+	if (info->irq)
+		unbind_from_irqhandler(info->irq, info);
+	info->irq = 0;
+	info->evtchn = 0;
+
+	if (info->host)
+		scsi_host_put(info->host);
+}
+
+static int scsifront_alloc_ring(struct vscsifrnt_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	struct vscsiif_sring *sring;
+	int err = -ENOMEM;
+
+	info->ring_ref = GRANT_INVALID_REF;
+
+	/***** Frontend to Backend ring start *****/
+	sring = (struct vscsiif_sring *) __get_free_page(GFP_KERNEL);
+	if (!sring) {
+		xenbus_dev_fatal(dev, err,
+			"fail to allocate shared ring (Front to Back)");
+		return err;
+	}
+	SHARED_RING_INIT(sring);
+	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
+
+	err = xenbus_grant_ring(dev, virt_to_mfn(sring));
+	if (err < 0) {
+		free_page((unsigned long) sring);
+		info->ring.sring = NULL;
+		xenbus_dev_fatal(dev, err,
+			"fail to grant shared ring (Front to Back)");
+		goto free_sring;
+	}
+	info->ring_ref = err;
+
+	err = xenbus_alloc_evtchn(dev, &info->evtchn);
+	if (err)
+		goto free_sring;
+
+	err = bind_evtchn_to_irq(info->evtchn);
+	if (err <= 0) {
+		xenbus_dev_fatal(dev, err, "bind_evtchn_to_irq");
+		goto free_sring;
+	}
+
+	info->irq = err;
+
+	err = request_threaded_irq(info->irq, NULL, scsifront_irq_fn,
+				   IRQF_ONESHOT, "scsifront", info);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "request_threaded_irq");
+		goto free_sring;
+	}
+
+	return 0;
+
+/* free resource */
+free_sring:
+	scsifront_free(info);
+
+	return err;
+}
+
+static int scsifront_init_ring(struct vscsifrnt_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	struct xenbus_transaction xbt;
+	int err;
+
+	DPRINTK("%s\n", __func__);
+
+	err = scsifront_alloc_ring(info);
+	if (err)
+		return err;
+	DPRINTK("%u %u\n", info->ring_ref, info->evtchn);
+
+again:
+	err = xenbus_transaction_start(&xbt);
+	if (err)
+		xenbus_dev_fatal(dev, err, "starting transaction");
+
+	err = xenbus_printf(xbt, dev->nodename, "ring-ref", "%u",
+			    info->ring_ref);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "%s", "writing ring-ref");
+		goto fail;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
+			    info->evtchn);
+
+	if (err) {
+		xenbus_dev_fatal(dev, err, "%s", "writing event-channel");
+		goto fail;
+	}
+
+	err = xenbus_transaction_end(xbt, 0);
+	if (err) {
+		if (err == -EAGAIN)
+			goto again;
+		xenbus_dev_fatal(dev, err, "completing transaction");
+		goto free_sring;
+	}
+
+	return 0;
+
+fail:
+	xenbus_transaction_end(xbt, 1);
+free_sring:
+	/* free resource */
+	scsifront_free(info);
+
+	return err;
+}
+
+
+static int scsifront_probe(struct xenbus_device *dev,
+			   const struct xenbus_device_id *id)
+{
+	struct vscsifrnt_info *info;
+	struct Scsi_Host *host;
+	int err = -ENOMEM;
+	char name[DEFAULT_TASK_COMM_LEN];
+
+	host = scsi_host_alloc(&scsifront_sht, sizeof(*info));
+	if (!host) {
+		xenbus_dev_fatal(dev, err, "fail to allocate scsi host");
+		return err;
+	}
+	info = (struct vscsifrnt_info *)host->hostdata;
+
+	dev_set_drvdata(&dev->dev, info);
+	info->dev  = dev;
+
+	info->shadow_free = (1UL << VSCSIIF_MAX_REQS) - 1;
+
+	err = scsifront_init_ring(info);
+	if (err) {
+		scsi_host_put(host);
+		return err;
+	}
+
+	init_waitqueue_head(&info->wq_sync);
+	spin_lock_init(&info->shadow_lock);
+
+	snprintf(name, DEFAULT_TASK_COMM_LEN, "vscsiif.%d", host->host_no);
+
+	host->max_id      = VSCSIIF_MAX_TARGET;
+	host->max_channel = 0;
+	host->max_lun     = VSCSIIF_MAX_LUN;
+	host->max_sectors = (host->sg_tablesize - 1) * PAGE_SIZE / 512;
+	host->max_cmd_len = VSCSIIF_MAX_COMMAND_SIZE;
+
+	err = scsi_add_host(host, &dev->dev);
+	if (err) {
+		dev_err(&dev->dev, "fail to add scsi host %d\n", err);
+		goto free_sring;
+	}
+	info->host = host;
+	info->host_active = 1;
+
+	xenbus_switch_state(dev, XenbusStateInitialised);
+
+	return 0;
+
+free_sring:
+	/* free resource */
+	scsifront_free(info);
+	scsi_host_put(host);
+	return err;
+}
+
+static int scsifront_remove(struct xenbus_device *dev)
+{
+	struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
+
+	DPRINTK("%s: %s removed\n", __func__, dev->nodename);
+
+	scsifront_free(info);
+
+	return 0;
+}
+
+static void scsifront_disconnect(struct vscsifrnt_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	struct Scsi_Host *host = info->host;
+
+	DPRINTK("%s: %s disconnect\n", __func__, dev->nodename);
+
+	/*
+	 * When this function is executed,  all devices of
+	 * Frontend have been deleted.
+	 * Therefore, it need not block I/O before remove_host.
+	 */
+
+	if (info->host_active)
+		scsi_remove_host(host);
+	info->host_active = 0;
+
+	xenbus_frontend_closed(dev);
+}
+
+static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op)
+{
+	struct xenbus_device *dev = info->dev;
+	int i, err = 0;
+	char str[64], state_str[64];
+	char **dir;
+	unsigned int dir_n = 0;
+	unsigned int device_state;
+	unsigned int hst, chn, tgt, lun;
+	struct scsi_device *sdev;
+
+	dir = xenbus_directory(XBT_NIL, dev->otherend, "vscsi-devs", &dir_n);
+	if (IS_ERR(dir))
+		return;
+
+	for (i = 0; i < dir_n; i++) {
+		/* read status */
+		snprintf(str, sizeof(str), "vscsi-devs/%s/state", dir[i]);
+		err = xenbus_scanf(XBT_NIL, dev->otherend, str, "%u",
+				   &device_state);
+		if (XENBUS_EXIST_ERR(err))
+			continue;
+
+		/* virtual SCSI device */
+		snprintf(str, sizeof(str), "vscsi-devs/%s/v-dev", dir[i]);
+		err = xenbus_scanf(XBT_NIL, dev->otherend, str,
+				   "%u:%u:%u:%u", &hst, &chn, &tgt, &lun);
+		if (XENBUS_EXIST_ERR(err))
+			continue;
+
+		/* front device state path */
+		snprintf(state_str, sizeof(state_str), "vscsi-devs/%s/state",
+			 dir[i]);
+
+		switch (op) {
+		case VSCSIFRONT_OP_ADD_LUN:
+			if (device_state == XenbusStateInitialised) {
+				sdev = __scsi_add_device(info->host, chn, tgt,
+							lun, NULL);
+				err = (IS_ERR(sdev) || !sdev->hostdata);
+				if (!IS_ERR(sdev)) {
+					sdev->hostdata = NULL;
+					scsi_device_put(sdev);
+				}
+
+				if (err) {
+					dev_err(&dev->dev,
+						"Device already in use.\n");
+					xenbus_printf(XBT_NIL, dev->nodename,
+						      state_str, "%d",
+						      XenbusStateClosed);
+				} else {
+					xenbus_printf(XBT_NIL, dev->nodename,
+						      state_str, "%d",
+						      XenbusStateConnected);
+				}
+			}
+			break;
+		case VSCSIFRONT_OP_DEL_LUN:
+			if (device_state == XenbusStateClosing) {
+				sdev = scsi_device_lookup(info->host, chn, tgt,
+							  lun);
+				if (sdev) {
+					scsi_remove_device(sdev);
+					scsi_device_put(sdev);
+					xenbus_printf(XBT_NIL, dev->nodename,
+						      state_str, "%d",
+						      XenbusStateClosed);
+				}
+			}
+			break;
+		default:
+			break;
+		}
+	}
+
+	kfree(dir);
+}
+
+static void scsifront_read_backend_params(struct xenbus_device *dev,
+					  struct vscsifrnt_info *info)
+{
+	unsigned int sg_grant;
+	int ret;
+	struct Scsi_Host *host = info->host;
+
+	ret = xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg-grant", "%u",
+			   &sg_grant);
+	if (ret == 1 && sg_grant) {
+		sg_grant = min_t(unsigned int, sg_grant, SG_ALL);
+		host->sg_tablesize = min_t(unsigned int, sg_grant,
+			VSCSIIF_SG_TABLESIZE * PAGE_SIZE /
+			sizeof(struct scsiif_request_segment));
+		dev_info(&dev->dev, "using up to %d SG entries\n",
+			 host->sg_tablesize);
+		host->max_sectors = (host->sg_tablesize - 1) * PAGE_SIZE / 512;
+	}
+}
+
+static void scsifront_backend_changed(struct xenbus_device *dev,
+				      enum xenbus_state backend_state)
+{
+	struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
+
+	DPRINTK("%p %u %u\n", dev, dev->state, backend_state);
+
+	switch (backend_state) {
+	case XenbusStateUnknown:
+	case XenbusStateInitialising:
+	case XenbusStateInitWait:
+	case XenbusStateInitialised:
+		break;
+
+	case XenbusStateConnected:
+		scsifront_read_backend_params(dev, info);
+		if (xenbus_read_driver_state(dev->nodename) ==
+			XenbusStateInitialised) {
+			scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
+		}
+
+		if (dev->state != XenbusStateConnected)
+			xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		/* Missed the backend's Closing state -- fallthrough */
+	case XenbusStateClosing:
+		scsifront_disconnect(info);
+		break;
+
+	case XenbusStateReconfiguring:
+		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_DEL_LUN);
+		xenbus_switch_state(dev, XenbusStateReconfiguring);
+		break;
+
+	case XenbusStateReconfigured:
+		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+	}
+}
+
+static const struct xenbus_device_id scsifront_ids[] = {
+	{ "vscsi" },
+	{ "" }
+};
+
+static DEFINE_XENBUS_DRIVER(scsifront, ,
+	.probe			= scsifront_probe,
+	.remove			= scsifront_remove,
+	.otherend_changed	= scsifront_backend_changed,
+);
+
+static int __init scsifront_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	return xenbus_register_frontend(&scsifront_driver);
+}
+module_init(scsifront_init);
+
+static void __exit scsifront_exit(void)
+{
+	xenbus_unregister_driver(&scsifront_driver);
+}
+module_exit(scsifront_exit);
+
+MODULE_DESCRIPTION("Xen SCSI frontend driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("xen:vscsi");
-- 
1.8.4.5

[PATCH V3 2/4] Introduce xen-scsifront module

[jgross]

From: Juergen Gross <jgross@suse.com>

Introduces the XEN pvSCSI frontend. 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
- move module to appropriate location in kernel tree
- adapt to Linux style guide
- some minor code simplifications
- replace constants with defines
- remove not used defines
- add support for larger SG lists by putting them in a granted page

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 drivers/scsi/Kconfig         |    9 +
 drivers/scsi/Makefile        |    1 +
 drivers/scsi/xen-scsifront.c | 1011 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1021 insertions(+)
 create mode 100644 drivers/scsi/xen-scsifront.c

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index baca589..e860c16 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -611,6 +611,15 @@ config VMWARE_PVSCSI
 	  To compile this driver as a module, choose M here: the
 	  module will be called vmw_pvscsi.
 
+config XEN_SCSI_FRONTEND
+	tristate "XEN SCSI frontend driver"
+	depends on SCSI && XEN
+	help
+	  The XEN SCSI frontend driver allows the kernel to access SCSI Devices
+	  within another guest OS (usually Dom0).
+	  Only needed if the kernel is running in a XEN guest and generic
+	  SCSI access to a device is needed.
+
 config HYPERV_STORAGE
 	tristate "Microsoft Hyper-V virtual storage driver"
 	depends on SCSI && HYPERV
diff --git a/drivers/scsi/Makefile b/drivers/scsi/Makefile
index e172d4f..a4ee9c5 100644
--- a/drivers/scsi/Makefile
+++ b/drivers/scsi/Makefile
@@ -144,6 +144,7 @@ obj-$(CONFIG_SCSI_ESAS2R)	+= esas2r/
 obj-$(CONFIG_SCSI_PMCRAID)	+= pmcraid.o
 obj-$(CONFIG_SCSI_VIRTIO)	+= virtio_scsi.o
 obj-$(CONFIG_VMWARE_PVSCSI)	+= vmw_pvscsi.o
+obj-$(CONFIG_XEN_SCSI_FRONTEND)	+= xen-scsifront.o
 obj-$(CONFIG_HYPERV_STORAGE)	+= hv_storvsc.o
 
 obj-$(CONFIG_ARM)		+= arm/
diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
new file mode 100644
index 0000000..7c60c68
--- /dev/null
+++ b/drivers/scsi/xen-scsifront.c
@@ -0,0 +1,1011 @@
+/*
+ * Xen SCSI frontend driver
+ *
+ * Copyright (c) 2008, FUJITSU Limited
+ *
+ * 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.
+ */
+
+#define DEBUG
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/wait.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+#include <linux/blkdev.h>
+#include <linux/pfn.h>
+#include <linux/slab.h>
+
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_host.h>
+
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+#include <xen/grant_table.h>
+#include <xen/events.h>
+#include <xen/page.h>
+
+#include <xen/interface/grant_table.h>
+#include <xen/interface/io/vscsiif.h>
+#include <xen/interface/io/protocols.h>
+
+#include <asm/xen/hypervisor.h>
+
+
+#define GRANT_INVALID_REF	0
+
+#define VSCSIFRONT_OP_ADD_LUN	1
+#define VSCSIFRONT_OP_DEL_LUN	2
+
+#define DEFAULT_TASK_COMM_LEN	TASK_COMM_LEN
+
+/* tuning point*/
+#define VSCSIIF_DEFAULT_CMD_PER_LUN 10
+#define VSCSIIF_MAX_TARGET          64
+#define VSCSIIF_MAX_LUN             255
+
+#define VSCSIIF_RING_SIZE	__CONST_RING_SIZE(vscsiif, PAGE_SIZE)
+#define VSCSIIF_MAX_REQS	VSCSIIF_RING_SIZE
+
+#define vscsiif_grants_sg(_sg)	(PFN_UP((_sg) *		\
+				sizeof(struct scsiif_request_segment)))
+
+struct vscsifrnt_shadow {
+	/* command between backend and frontend */
+	unsigned char act;
+	uint16_t rqid;
+
+	/* Number of pieces of scatter-gather */
+	unsigned int nr_grants;
+	struct scsiif_request_segment *sg;
+
+	/* do reset or abort function */
+	wait_queue_head_t wq_reset;	/* reset work queue           */
+	int wait_reset;			/* reset work queue condition */
+	int32_t rslt_reset;		/* reset response status      */
+					/* (SUCESS or FAILED)         */
+
+	/* requested struct scsi_cmnd is stored from kernel */
+	struct scsi_cmnd *sc;
+	int gref[vscsiif_grants_sg(SG_ALL) + SG_ALL];
+};
+
+struct vscsifrnt_info {
+	struct xenbus_device *dev;
+
+	struct Scsi_Host *host;
+	int host_active;
+
+	spinlock_t shadow_lock;
+	unsigned int evtchn;
+	unsigned int irq;
+
+	grant_ref_t ring_ref;
+	struct vscsiif_front_ring ring;
+	struct vscsiif_response	ring_res;
+
+	unsigned long shadow_free;
+	struct vscsifrnt_shadow *shadow[VSCSIIF_MAX_REQS];
+
+	wait_queue_head_t wq_sync;
+	unsigned int waiting_sync:1;
+};
+
+#define DPRINTK(_f, _a...)				\
+	pr_debug("(file=%s, line=%d) " _f, __FILE__ , __LINE__ , ## _a)
+
+#define PREFIX(lvl) KERN_##lvl "scsifront: "
+
+static void scsifront_wake_up(struct vscsifrnt_info *info)
+{
+	info->waiting_sync = 0;
+	wake_up(&info->wq_sync);
+}
+
+static int scsifront_get_rqid(struct vscsifrnt_info *info)
+{
+	unsigned long flags;
+	int free;
+
+	spin_lock_irqsave(&info->shadow_lock, flags);
+
+	free = find_first_bit(&info->shadow_free, VSCSIIF_MAX_REQS);
+	info->shadow_free &= ~(1UL << free);
+
+	spin_unlock_irqrestore(&info->shadow_lock, flags);
+
+	return free;
+}
+
+static int _scsifront_put_rqid(struct vscsifrnt_info *info, uint32_t id)
+{
+	info->shadow_free |= 1UL << id;
+	info->shadow[id] = NULL;
+
+	return (info->shadow_free == 1UL << id || info->waiting_sync);
+}
+
+static void scsifront_put_rqid(struct vscsifrnt_info *info, uint32_t id)
+{
+	unsigned long flags;
+	int was_empty;
+
+	spin_lock_irqsave(&info->shadow_lock, flags);
+	was_empty = _scsifront_put_rqid(info, id);
+	spin_unlock_irqrestore(&info->shadow_lock, flags);
+
+	if (was_empty)
+		scsifront_wake_up(info);
+}
+
+static struct vscsiif_request *scsifront_pre_req(struct vscsifrnt_info *info)
+{
+	struct vscsiif_front_ring *ring = &(info->ring);
+	struct vscsiif_request *ring_req;
+	uint32_t id;
+
+	id = scsifront_get_rqid(info);	/* use id by response */
+	if (id >= VSCSIIF_MAX_REQS)
+		return NULL;
+
+	ring_req = RING_GET_REQUEST(&(info->ring), ring->req_prod_pvt);
+
+	ring->req_prod_pvt++;
+
+	ring_req->rqid = (uint16_t)id;
+
+	return ring_req;
+}
+
+static void scsifront_do_request(struct vscsifrnt_info *info)
+{
+	struct vscsiif_front_ring *ring = &(info->ring);
+	int notify;
+
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(ring, notify);
+	if (notify)
+		notify_remote_via_irq(info->irq);
+}
+
+static void scsifront_gnttab_done(struct vscsifrnt_info *info, uint32_t id)
+{
+	struct vscsifrnt_shadow *s = info->shadow[id];
+	int i;
+
+	if (s->sc->sc_data_direction == DMA_NONE)
+		return;
+
+	for (i = 0; i < s->nr_grants; i++) {
+		if (unlikely(gnttab_query_foreign_access(s->gref[i]) != 0)) {
+			shost_printk(PREFIX(ALERT), info->host,
+				     "grant still in use by backend\n");
+			BUG();
+		}
+		gnttab_end_foreign_access(s->gref[i], 0, 0UL);
+	}
+
+	kfree(s->sg);
+}
+
+static void scsifront_cdb_cmd_done(struct vscsifrnt_info *info,
+				   struct vscsiif_response *ring_res)
+{
+	struct scsi_cmnd *sc;
+	uint32_t id;
+	uint8_t sense_len;
+
+	id = ring_res->rqid;
+	sc = info->shadow[id]->sc;
+
+	BUG_ON(sc == NULL);
+
+	scsifront_gnttab_done(info, id);
+	scsifront_put_rqid(info, id);
+
+	sc->result = ring_res->rslt;
+	scsi_set_resid(sc, ring_res->residual_len);
+
+	sense_len = min_t(uint8_t, VSCSIIF_SENSE_BUFFERSIZE,
+			  ring_res->sense_len);
+
+	if (sense_len)
+		memcpy(sc->sense_buffer, ring_res->sense_buffer, sense_len);
+
+	sc->scsi_done(sc);
+}
+
+static void scsifront_sync_cmd_done(struct vscsifrnt_info *info,
+				    struct vscsiif_response *ring_res)
+{
+	uint16_t id = ring_res->rqid;
+	unsigned long flags;
+	struct vscsifrnt_shadow *shadow = info->shadow[id];
+	int was_empty;
+
+	spin_lock_irqsave(&info->shadow_lock, flags);
+	shadow->wait_reset = 1;
+	switch (shadow->rslt_reset) {
+	case 0:
+		shadow->rslt_reset = ring_res->rslt;
+		break;
+	case -1:
+		was_empty = _scsifront_put_rqid(info, id);
+		spin_unlock_irqrestore(&info->shadow_lock, flags);
+		kfree(shadow);
+		if (was_empty)
+			scsifront_wake_up(info);
+		return;
+	default:
+		shost_printk(PREFIX(ERR), info->host,
+			     "bad reset state %d, possibly leaking %u\n",
+			     shadow->rslt_reset, id);
+		break;
+	}
+	spin_unlock_irqrestore(&info->shadow_lock, flags);
+
+	wake_up(&shadow->wq_reset);
+}
+
+static int scsifront_cmd_done(struct vscsifrnt_info *info)
+{
+	struct vscsiif_response *ring_res;
+	RING_IDX i, rp;
+	int more_to_do = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(info->host->host_lock, flags);
+
+	rp = info->ring.sring->rsp_prod;
+	rmb();	/* ordering required respective to dom0 */
+	for (i = info->ring.rsp_cons; i != rp; i++) {
+
+		ring_res = RING_GET_RESPONSE(&info->ring, i);
+
+		if (info->shadow[ring_res->rqid]->act == VSCSIIF_ACT_SCSI_CDB)
+			scsifront_cdb_cmd_done(info, ring_res);
+		else
+			scsifront_sync_cmd_done(info, ring_res);
+	}
+
+	info->ring.rsp_cons = i;
+
+	if (i != info->ring.req_prod_pvt)
+		RING_FINAL_CHECK_FOR_RESPONSES(&info->ring, more_to_do);
+	else
+		info->ring.sring->rsp_event = i + 1;
+
+	info->waiting_sync = 0;
+
+	spin_unlock_irqrestore(info->host->host_lock, flags);
+
+	wake_up(&info->wq_sync);
+
+	return more_to_do;
+}
+
+static irqreturn_t scsifront_irq_fn(int irq, void *dev_id)
+{
+	struct vscsifrnt_info *info = dev_id;
+
+	while (scsifront_cmd_done(info))
+		/* Yield point for this unbounded loop. */
+		cond_resched();
+
+	return IRQ_HANDLED;
+}
+
+static int map_data_for_request(struct vscsifrnt_info *info,
+				struct scsi_cmnd *sc,
+				struct vscsiif_request *ring_req,
+				struct vscsifrnt_shadow *shadow)
+{
+	grant_ref_t gref_head;
+	struct page *page;
+	int err, ref, ref_cnt = 0;
+	int write = (sc->sc_data_direction == DMA_TO_DEVICE);
+	unsigned int i, off, len, bytes;
+	unsigned int data_len = scsi_bufflen(sc);
+	unsigned int data_grants = 0, seg_grants = 0;
+	struct scatterlist *sg;
+	unsigned long mfn;
+	struct scsiif_request_segment *seg;
+
+	ring_req->nr_segments = 0;
+	if (sc->sc_data_direction == DMA_NONE || !data_len)
+		return 0;
+
+	scsi_for_each_sg(sc, sg, scsi_sg_count(sc), i)
+		data_grants += PFN_UP(sg->offset + sg->length);
+
+	if (data_grants > VSCSIIF_SG_TABLESIZE) {
+		if (data_grants > info->host->sg_tablesize) {
+			shost_printk(PREFIX(ERR), info->host,
+			     "Unable to map request_buffer for command!\n");
+			return -E2BIG;
+		}
+		seg_grants = vscsiif_grants_sg(data_grants);
+		shadow->sg = kcalloc(data_grants,
+			sizeof(struct scsiif_request_segment), GFP_NOIO);
+		if (!shadow->sg)
+			return -ENOMEM;
+	}
+	seg = shadow->sg ? : ring_req->seg;
+
+	err = gnttab_alloc_grant_references(seg_grants + data_grants,
+					    &gref_head);
+	if (err) {
+		kfree(shadow->sg);
+		shost_printk(PREFIX(ERR), info->host,
+			     "gnttab_alloc_grant_references() error\n");
+		return -ENOMEM;
+	}
+
+	if (seg_grants) {
+		page = virt_to_page(seg);
+		off = (unsigned long)seg & ~PAGE_MASK;
+		len = sizeof(struct scsiif_request_segment) * data_grants;
+		while (len > 0) {
+			bytes = min_t(unsigned int, len, PAGE_SIZE - off);
+
+			ref = gnttab_claim_grant_reference(&gref_head);
+			BUG_ON(ref == -ENOSPC);
+
+			mfn = pfn_to_mfn(page_to_pfn(page));
+			gnttab_grant_foreign_access_ref(ref,
+				info->dev->otherend_id, mfn, 1);
+			shadow->gref[ref_cnt] = ref;
+			ring_req->seg[ref_cnt].gref   = ref;
+			ring_req->seg[ref_cnt].offset = (uint16_t)off;
+			ring_req->seg[ref_cnt].length = (uint16_t)bytes;
+
+			page++;
+			len -= bytes;
+			off = 0;
+			ref_cnt++;
+		}
+		BUG_ON(seg_grants < ref_cnt);
+		seg_grants = ref_cnt;
+	}
+
+	scsi_for_each_sg(sc, sg, scsi_sg_count(sc), i) {
+		page = sg_page(sg);
+		off = sg->offset;
+		len = sg->length;
+
+		while (len > 0 && data_len > 0) {
+			/*
+			 * sg sends a scatterlist that is larger than
+			 * the data_len it wants transferred for certain
+			 * IO sizes
+			 */
+			bytes = min_t(unsigned int, len, PAGE_SIZE - off);
+			bytes = min(bytes, data_len);
+
+			ref = gnttab_claim_grant_reference(&gref_head);
+			BUG_ON(ref == -ENOSPC);
+
+			mfn = pfn_to_mfn(page_to_pfn(page));
+			gnttab_grant_foreign_access_ref(ref,
+				info->dev->otherend_id, mfn, write);
+
+			shadow->gref[ref_cnt] = ref;
+			seg->gref   = ref;
+			seg->offset = (uint16_t)off;
+			seg->length = (uint16_t)bytes;
+
+			page++;
+			seg++;
+			len -= bytes;
+			data_len -= bytes;
+			off = 0;
+			ref_cnt++;
+		}
+	}
+
+	if (seg_grants)
+		ring_req->nr_segments = VSCSIIF_SG_GRANT | seg_grants;
+	else
+		ring_req->nr_segments = (uint8_t)ref_cnt;
+	shadow->nr_grants = ref_cnt;
+
+	return 0;
+}
+
+static struct vscsiif_request *scsifront_command2ring(
+		struct vscsifrnt_info *info, struct scsi_cmnd *sc,
+		struct vscsifrnt_shadow *shadow)
+{
+	struct vscsiif_request *ring_req;
+
+	memset(shadow, 0, sizeof(*shadow));
+
+	ring_req = scsifront_pre_req(info);
+	if (!ring_req)
+		return NULL;
+
+	info->shadow[ring_req->rqid] = shadow;
+	shadow->rqid = ring_req->rqid;
+
+	ring_req->id      = sc->device->id;
+	ring_req->lun     = sc->device->lun;
+	ring_req->channel = sc->device->channel;
+	ring_req->cmd_len = sc->cmd_len;
+
+	BUG_ON(sc->cmd_len > VSCSIIF_MAX_COMMAND_SIZE);
+
+	if (sc->cmd_len)
+		memcpy(ring_req->cmnd, sc->cmnd, sc->cmd_len);
+	else
+		memset(ring_req->cmnd, 0, VSCSIIF_MAX_COMMAND_SIZE);
+
+	ring_req->sc_data_direction   = (uint8_t)sc->sc_data_direction;
+	ring_req->timeout_per_command = sc->request->timeout / HZ;
+
+	return ring_req;
+}
+
+static int scsifront_queuecommand(struct Scsi_Host *shost,
+				  struct scsi_cmnd *sc)
+{
+	struct vscsifrnt_info *info = shost_priv(shost);
+	struct vscsiif_request *ring_req;
+	struct vscsifrnt_shadow *shadow = scsi_cmd_priv(sc);
+	unsigned long flags;
+	int err;
+	uint16_t rqid;
+
+	spin_lock_irqsave(shost->host_lock, flags);
+	if (RING_FULL(&info->ring))
+		goto busy;
+
+	ring_req = scsifront_command2ring(info, sc, shadow);
+	if (!ring_req)
+		goto busy;
+
+	sc->result    = 0;
+
+	rqid              = ring_req->rqid;
+	ring_req->act     = VSCSIIF_ACT_SCSI_CDB;
+
+	shadow->sc  = sc;
+	shadow->act = VSCSIIF_ACT_SCSI_CDB;
+
+	err = map_data_for_request(info, sc, ring_req, shadow);
+	if (err < 0) {
+		DPRINTK("%s: err %d\n", __func__, err);
+		scsifront_put_rqid(info, rqid);
+		spin_unlock_irqrestore(shost->host_lock, flags);
+		if (err == -ENOMEM)
+			return SCSI_MLQUEUE_HOST_BUSY;
+		sc->result = DID_ERROR << 16;
+		sc->scsi_done(sc);
+		return 0;
+	}
+
+	scsifront_do_request(info);
+	spin_unlock_irqrestore(shost->host_lock, flags);
+
+	return 0;
+
+busy:
+	spin_unlock_irqrestore(shost->host_lock, flags);
+	DPRINTK("%s: busy\n", __func__);
+	return SCSI_MLQUEUE_HOST_BUSY;
+}
+
+static int scsifront_action_handler(struct scsi_cmnd *sc, uint8_t act)
+{
+	struct Scsi_Host *host = sc->device->host;
+	struct vscsifrnt_info *info = shost_priv(host);
+	struct vscsifrnt_shadow *shadow, *s = scsi_cmd_priv(sc);
+	struct vscsiif_request *ring_req;
+	int err = 0;
+
+	shadow = kmalloc(sizeof(*shadow), GFP_NOIO);
+	if (!shadow)
+		return FAILED;
+
+	for (;;) {
+		spin_lock_irq(host->host_lock);
+		if (!RING_FULL(&info->ring)) {
+			ring_req = scsifront_command2ring(info, sc, shadow);
+			if (ring_req)
+				break;
+		}
+		if (err) {
+			spin_unlock_irq(host->host_lock);
+			kfree(shadow);
+			return FAILED;
+		}
+		info->waiting_sync = 1;
+		spin_unlock_irq(host->host_lock);
+		err = wait_event_interruptible(info->wq_sync,
+					       !info->waiting_sync);
+		spin_lock_irq(host->host_lock);
+	}
+
+	ring_req->act = act;
+	ring_req->ref_rqid = s->rqid;
+
+	shadow->act = act;
+	shadow->rslt_reset = 0;
+	init_waitqueue_head(&shadow->wq_reset);
+
+	ring_req->nr_segments         = 0;
+
+	scsifront_do_request(info);
+
+	spin_unlock_irq(host->host_lock);
+	err = wait_event_interruptible(shadow->wq_reset, shadow->wait_reset);
+	spin_lock_irq(host->host_lock);
+
+	if (!err) {
+		err = shadow->rslt_reset;
+		scsifront_put_rqid(info, shadow->rqid);
+		kfree(shadow);
+	} else {
+		spin_lock(&info->shadow_lock);
+		shadow->rslt_reset = -1;
+		spin_unlock(&info->shadow_lock);
+		err = FAILED;
+	}
+
+	spin_unlock_irq(host->host_lock);
+	return err;
+}
+
+static int scsifront_eh_abort_handler(struct scsi_cmnd *sc)
+{
+	DPRINTK("%s\n", __func__);
+	return scsifront_action_handler(sc, VSCSIIF_ACT_SCSI_ABORT);
+}
+
+static int scsifront_dev_reset_handler(struct scsi_cmnd *sc)
+{
+	DPRINTK("%s\n", __func__);
+	return scsifront_action_handler(sc, VSCSIIF_ACT_SCSI_RESET);
+}
+
+static int scsifront_sdev_alloc(struct scsi_device *sdev)
+{
+	/* set hostdata to not NULL indicating new allocation */
+	sdev->hostdata = sdev;
+	return 0;
+}
+
+static struct scsi_host_template scsifront_sht = {
+	.module			= THIS_MODULE,
+	.name			= "Xen SCSI frontend driver",
+	.queuecommand		= scsifront_queuecommand,
+	.eh_abort_handler	= scsifront_eh_abort_handler,
+	.eh_device_reset_handler = scsifront_dev_reset_handler,
+	.slave_alloc		= scsifront_sdev_alloc,
+	.cmd_per_lun		= VSCSIIF_DEFAULT_CMD_PER_LUN,
+	.can_queue		= VSCSIIF_MAX_REQS,
+	.this_id		= -1,
+	.cmd_size		= sizeof(struct vscsifrnt_shadow),
+	.sg_tablesize		= VSCSIIF_SG_TABLESIZE,
+	.use_clustering		= DISABLE_CLUSTERING,
+	.proc_name		= "scsifront",
+};
+
+static void scsifront_free(struct vscsifrnt_info *info)
+{
+	if (info->host && info->host_active) {
+		/* Scsi_host not yet removed */
+		scsi_remove_host(info->host);
+		info->host_active = 0;
+	}
+
+	if (info->ring_ref != GRANT_INVALID_REF) {
+		gnttab_end_foreign_access(info->ring_ref, 0,
+					  (unsigned long)info->ring.sring);
+		info->ring_ref = GRANT_INVALID_REF;
+		info->ring.sring = NULL;
+	}
+
+	if (info->irq)
+		unbind_from_irqhandler(info->irq, info);
+	info->irq = 0;
+	info->evtchn = 0;
+
+	if (info->host)
+		scsi_host_put(info->host);
+}
+
+static int scsifront_alloc_ring(struct vscsifrnt_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	struct vscsiif_sring *sring;
+	int err = -ENOMEM;
+
+	info->ring_ref = GRANT_INVALID_REF;
+
+	/***** Frontend to Backend ring start *****/
+	sring = (struct vscsiif_sring *) __get_free_page(GFP_KERNEL);
+	if (!sring) {
+		xenbus_dev_fatal(dev, err,
+			"fail to allocate shared ring (Front to Back)");
+		return err;
+	}
+	SHARED_RING_INIT(sring);
+	FRONT_RING_INIT(&info->ring, sring, PAGE_SIZE);
+
+	err = xenbus_grant_ring(dev, virt_to_mfn(sring));
+	if (err < 0) {
+		free_page((unsigned long) sring);
+		info->ring.sring = NULL;
+		xenbus_dev_fatal(dev, err,
+			"fail to grant shared ring (Front to Back)");
+		goto free_sring;
+	}
+	info->ring_ref = err;
+
+	err = xenbus_alloc_evtchn(dev, &info->evtchn);
+	if (err)
+		goto free_sring;
+
+	err = bind_evtchn_to_irq(info->evtchn);
+	if (err <= 0) {
+		xenbus_dev_fatal(dev, err, "bind_evtchn_to_irq");
+		goto free_sring;
+	}
+
+	info->irq = err;
+
+	err = request_threaded_irq(info->irq, NULL, scsifront_irq_fn,
+				   IRQF_ONESHOT, "scsifront", info);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "request_threaded_irq");
+		goto free_sring;
+	}
+
+	return 0;
+
+/* free resource */
+free_sring:
+	scsifront_free(info);
+
+	return err;
+}
+
+static int scsifront_init_ring(struct vscsifrnt_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	struct xenbus_transaction xbt;
+	int err;
+
+	DPRINTK("%s\n", __func__);
+
+	err = scsifront_alloc_ring(info);
+	if (err)
+		return err;
+	DPRINTK("%u %u\n", info->ring_ref, info->evtchn);
+
+again:
+	err = xenbus_transaction_start(&xbt);
+	if (err)
+		xenbus_dev_fatal(dev, err, "starting transaction");
+
+	err = xenbus_printf(xbt, dev->nodename, "ring-ref", "%u",
+			    info->ring_ref);
+	if (err) {
+		xenbus_dev_fatal(dev, err, "%s", "writing ring-ref");
+		goto fail;
+	}
+
+	err = xenbus_printf(xbt, dev->nodename, "event-channel", "%u",
+			    info->evtchn);
+
+	if (err) {
+		xenbus_dev_fatal(dev, err, "%s", "writing event-channel");
+		goto fail;
+	}
+
+	err = xenbus_transaction_end(xbt, 0);
+	if (err) {
+		if (err == -EAGAIN)
+			goto again;
+		xenbus_dev_fatal(dev, err, "completing transaction");
+		goto free_sring;
+	}
+
+	return 0;
+
+fail:
+	xenbus_transaction_end(xbt, 1);
+free_sring:
+	/* free resource */
+	scsifront_free(info);
+
+	return err;
+}
+
+
+static int scsifront_probe(struct xenbus_device *dev,
+			   const struct xenbus_device_id *id)
+{
+	struct vscsifrnt_info *info;
+	struct Scsi_Host *host;
+	int err = -ENOMEM;
+	char name[DEFAULT_TASK_COMM_LEN];
+
+	host = scsi_host_alloc(&scsifront_sht, sizeof(*info));
+	if (!host) {
+		xenbus_dev_fatal(dev, err, "fail to allocate scsi host");
+		return err;
+	}
+	info = (struct vscsifrnt_info *)host->hostdata;
+
+	dev_set_drvdata(&dev->dev, info);
+	info->dev  = dev;
+
+	info->shadow_free = (1UL << VSCSIIF_MAX_REQS) - 1;
+
+	err = scsifront_init_ring(info);
+	if (err) {
+		scsi_host_put(host);
+		return err;
+	}
+
+	init_waitqueue_head(&info->wq_sync);
+	spin_lock_init(&info->shadow_lock);
+
+	snprintf(name, DEFAULT_TASK_COMM_LEN, "vscsiif.%d", host->host_no);
+
+	host->max_id      = VSCSIIF_MAX_TARGET;
+	host->max_channel = 0;
+	host->max_lun     = VSCSIIF_MAX_LUN;
+	host->max_sectors = (host->sg_tablesize - 1) * PAGE_SIZE / 512;
+	host->max_cmd_len = VSCSIIF_MAX_COMMAND_SIZE;
+
+	err = scsi_add_host(host, &dev->dev);
+	if (err) {
+		dev_err(&dev->dev, "fail to add scsi host %d\n", err);
+		goto free_sring;
+	}
+	info->host = host;
+	info->host_active = 1;
+
+	xenbus_switch_state(dev, XenbusStateInitialised);
+
+	return 0;
+
+free_sring:
+	/* free resource */
+	scsifront_free(info);
+	scsi_host_put(host);
+	return err;
+}
+
+static int scsifront_remove(struct xenbus_device *dev)
+{
+	struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
+
+	DPRINTK("%s: %s removed\n", __func__, dev->nodename);
+
+	scsifront_free(info);
+
+	return 0;
+}
+
+static void scsifront_disconnect(struct vscsifrnt_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	struct Scsi_Host *host = info->host;
+
+	DPRINTK("%s: %s disconnect\n", __func__, dev->nodename);
+
+	/*
+	 * When this function is executed,  all devices of
+	 * Frontend have been deleted.
+	 * Therefore, it need not block I/O before remove_host.
+	 */
+
+	if (info->host_active)
+		scsi_remove_host(host);
+	info->host_active = 0;
+
+	xenbus_frontend_closed(dev);
+}
+
+static void scsifront_do_lun_hotplug(struct vscsifrnt_info *info, int op)
+{
+	struct xenbus_device *dev = info->dev;
+	int i, err = 0;
+	char str[64], state_str[64];
+	char **dir;
+	unsigned int dir_n = 0;
+	unsigned int device_state;
+	unsigned int hst, chn, tgt, lun;
+	struct scsi_device *sdev;
+
+	dir = xenbus_directory(XBT_NIL, dev->otherend, "vscsi-devs", &dir_n);
+	if (IS_ERR(dir))
+		return;
+
+	for (i = 0; i < dir_n; i++) {
+		/* read status */
+		snprintf(str, sizeof(str), "vscsi-devs/%s/state", dir[i]);
+		err = xenbus_scanf(XBT_NIL, dev->otherend, str, "%u",
+				   &device_state);
+		if (XENBUS_EXIST_ERR(err))
+			continue;
+
+		/* virtual SCSI device */
+		snprintf(str, sizeof(str), "vscsi-devs/%s/v-dev", dir[i]);
+		err = xenbus_scanf(XBT_NIL, dev->otherend, str,
+				   "%u:%u:%u:%u", &hst, &chn, &tgt, &lun);
+		if (XENBUS_EXIST_ERR(err))
+			continue;
+
+		/* front device state path */
+		snprintf(state_str, sizeof(state_str), "vscsi-devs/%s/state",
+			 dir[i]);
+
+		switch (op) {
+		case VSCSIFRONT_OP_ADD_LUN:
+			if (device_state == XenbusStateInitialised) {
+				sdev = __scsi_add_device(info->host, chn, tgt,
+							lun, NULL);
+				err = (IS_ERR(sdev) || !sdev->hostdata);
+				if (!IS_ERR(sdev)) {
+					sdev->hostdata = NULL;
+					scsi_device_put(sdev);
+				}
+
+				if (err) {
+					dev_err(&dev->dev,
+						"Device already in use.\n");
+					xenbus_printf(XBT_NIL, dev->nodename,
+						      state_str, "%d",
+						      XenbusStateClosed);
+				} else {
+					xenbus_printf(XBT_NIL, dev->nodename,
+						      state_str, "%d",
+						      XenbusStateConnected);
+				}
+			}
+			break;
+		case VSCSIFRONT_OP_DEL_LUN:
+			if (device_state == XenbusStateClosing) {
+				sdev = scsi_device_lookup(info->host, chn, tgt,
+							  lun);
+				if (sdev) {
+					scsi_remove_device(sdev);
+					scsi_device_put(sdev);
+					xenbus_printf(XBT_NIL, dev->nodename,
+						      state_str, "%d",
+						      XenbusStateClosed);
+				}
+			}
+			break;
+		default:
+			break;
+		}
+	}
+
+	kfree(dir);
+}
+
+static void scsifront_read_backend_params(struct xenbus_device *dev,
+					  struct vscsifrnt_info *info)
+{
+	unsigned int sg_grant;
+	int ret;
+	struct Scsi_Host *host = info->host;
+
+	ret = xenbus_scanf(XBT_NIL, dev->otherend, "feature-sg-grant", "%u",
+			   &sg_grant);
+	if (ret == 1 && sg_grant) {
+		sg_grant = min_t(unsigned int, sg_grant, SG_ALL);
+		host->sg_tablesize = min_t(unsigned int, sg_grant,
+			VSCSIIF_SG_TABLESIZE * PAGE_SIZE /
+			sizeof(struct scsiif_request_segment));
+		dev_info(&dev->dev, "using up to %d SG entries\n",
+			 host->sg_tablesize);
+		host->max_sectors = (host->sg_tablesize - 1) * PAGE_SIZE / 512;
+	}
+}
+
+static void scsifront_backend_changed(struct xenbus_device *dev,
+				      enum xenbus_state backend_state)
+{
+	struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
+
+	DPRINTK("%p %u %u\n", dev, dev->state, backend_state);
+
+	switch (backend_state) {
+	case XenbusStateUnknown:
+	case XenbusStateInitialising:
+	case XenbusStateInitWait:
+	case XenbusStateInitialised:
+		break;
+
+	case XenbusStateConnected:
+		scsifront_read_backend_params(dev, info);
+		if (xenbus_read_driver_state(dev->nodename) ==
+			XenbusStateInitialised) {
+			scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
+		}
+
+		if (dev->state != XenbusStateConnected)
+			xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+
+	case XenbusStateClosed:
+		if (dev->state == XenbusStateClosed)
+			break;
+		/* Missed the backend's Closing state -- fallthrough */
+	case XenbusStateClosing:
+		scsifront_disconnect(info);
+		break;
+
+	case XenbusStateReconfiguring:
+		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_DEL_LUN);
+		xenbus_switch_state(dev, XenbusStateReconfiguring);
+		break;
+
+	case XenbusStateReconfigured:
+		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
+		xenbus_switch_state(dev, XenbusStateConnected);
+		break;
+	}
+}
+
+static const struct xenbus_device_id scsifront_ids[] = {
+	{ "vscsi" },
+	{ "" }
+};
+
+static DEFINE_XENBUS_DRIVER(scsifront, ,
+	.probe			= scsifront_probe,
+	.remove			= scsifront_remove,
+	.otherend_changed	= scsifront_backend_changed,
+);
+
+static int __init scsifront_init(void)
+{
+	if (!xen_domain())
+		return -ENODEV;
+
+	return xenbus_register_frontend(&scsifront_driver);
+}
+module_init(scsifront_init);
+
+static void __exit scsifront_exit(void)
+{
+	xenbus_unregister_driver(&scsifront_driver);
+}
+module_exit(scsifront_exit);
+
+MODULE_DESCRIPTION("Xen SCSI frontend driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("xen:vscsi");
-- 
1.8.4.5

[PATCH V3 3/4] Introduce XEN scsiback module

[jgross]

From: Juergen Gross <jgross@suse.com>

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>
---
 drivers/xen/Kconfig        |    9 +
 drivers/xen/Makefile       |    1 +
 drivers/xen/xen-scsiback.c | 2282 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 2292 insertions(+)
 create mode 100644 drivers/xen/xen-scsiback.c

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 38fb36e..42fb963 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 45e00af..b42ee75 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_XEN_STUB)			+= xen-stub.o
 obj-$(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_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..4a0d6e3
--- /dev/null
+++ b/drivers/xen/xen-scsiback.c
@@ -0,0 +1,2282 @@
+/*
+ * 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/kthread.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 evtchn;
+	unsigned int irq;
+
+	struct vscsiif_back_ring  ring;
+
+	spinlock_t ring_lock;
+	atomic_t nr_unreplied_reqs;
+
+	spinlock_t v2p_lock;
+	struct list_head v2p_entry_lists;
+
+	struct task_struct *kthread;
+	wait_queue_head_t waiting_to_free;
+	wait_queue_head_t wq;
+	wait_queue_head_t shutdown_wq;
+	unsigned int waiting_reqs;
+};
+
+/* 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 vscsibk_emulate {
+	void (*pre_function)(struct vscsibk_pend *, void *);
+	void (*post_function)(struct vscsibk_pend *, void *);
+};
+
+struct scsiback_nexus {
+	/* Pointer to TCM session for I_T Nexus */
+	struct se_session *tvn_se_sess;
+};
+
+struct scsiback_nacl {
+	/* Binary World Wide unique Port Name for pvscsi Initiator port */
+	u64 iport_wwpn;
+	/* ASCII formatted WWPN for Sas Initiator port */
+	char iport_name[VSCSI_NAMELEN];
+	/* Returned by scsiback_make_nodeacl() */
+	struct se_node_acl se_node_acl;
+};
+
+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_get(_b) (atomic_inc(&(_b)->nr_unreplied_reqs))
+#define scsiback_put(_b)				\
+	do {						\
+		if (atomic_dec_and_test(&(_b)->nr_unreplied_reqs))	\
+			wake_up(&(_b)->waiting_to_free);\
+	} while (0)
+
+#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 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);
+
+	kmem_cache_free(scsiback_cachep, pending_req);
+}
+
+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);
+
+	transport_generic_free_cmd(&pending_req->se_cmd, 0);
+}
+
+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));
+	se_cmd->prot_pto = true;
+
+	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) {
+		pr_err("xen-pvscsi: %s: kmalloc() error\n", __func__);
+		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_notify_work(struct vscsibk_info *info)
+{
+	info->waiting_reqs = 1;
+	wake_up(&info->wq);
+}
+
+static irqreturn_t scsiback_intr(int irq, void *dev_id)
+{
+	scsiback_notify_work((struct vscsibk_info *)dev_id);
+	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) {
+		pr_err("xen-pvscsi: Already connected through?\n");
+		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_irqhandler(
+			info->domid, evtchn,
+			scsiback_intr, 0, "vscsiif-backend", info);
+
+	if (err < 0)
+		goto unmap_page;
+
+	info->irq = err;
+
+	return 0;
+
+unmap_page:
+	xenbus_unmap_ring_vfree(info->dev, area);
+
+	return err;
+}
+
+static void scsiback_disconnect(struct vscsibk_info *info)
+{
+	if (info->kthread) {
+		kthread_stop(info->kthread);
+		info->kthread = NULL;
+		wake_up(&info->shutdown_wq);
+	}
+
+	wait_event(info->waiting_to_free,
+		atomic_read(&info->nr_unreplied_reqs) == 0);
+
+	if (info->irq) {
+		unbind_from_irqhandler(info->irq, info);
+		info->irq = 0;
+	}
+
+	if (info->ring.sring) {
+		xenbus_unmap_ring_vfree(info->dev, info->ring.sring);
+		info->ring.sring = NULL;
+	}
+}
+
+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) {
+		pr_err("xen-pvscsi: %s: kmalloc() error\n", __func__);
+		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);
+}
+
+/*
+  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 = 0;
+	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);
+		return -EACCES;
+	}
+
+	while ((rc != rp)) {
+		if (RING_REQUEST_CONS_OVERFLOW(ring, rc))
+			break;
+		pending_req = kmem_cache_alloc(scsiback_cachep, GFP_KERNEL);
+		if (NULL == pending_req) {
+			more_to_do = 1;
+			break;
+		}
+
+		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);
+			more_to_do = 1;
+			break;
+		}
+
+		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);
+			} 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);
+			break;
+		}
+
+		/* Yield point for this unbounded loop. */
+		cond_resched();
+	}
+
+	if (RING_HAS_UNCONSUMED_REQUESTS(ring))
+		more_to_do = 1;
+
+	return more_to_do;
+}
+
+static int scsiback_do_cmd_fn(struct vscsibk_info *info)
+{
+	int more_to_do;
+
+	do {
+		more_to_do = _scsiback_do_cmd_fn(info);
+		if (more_to_do)
+			break;
+
+		RING_FINAL_CHECK_FOR_REQUESTS(&info->ring, more_to_do);
+	} while (more_to_do);
+
+	return more_to_do;
+}
+
+static int scsiback_schedule(void *data)
+{
+	struct vscsibk_info *info = (struct vscsibk_info *)data;
+
+	while (!kthread_should_stop()) {
+		wait_event_interruptible(info->wq,
+			info->waiting_reqs || kthread_should_stop());
+
+		info->waiting_reqs = 0;
+		smp_mb();	/* waiting_reqs used by other thread */
+
+		switch (scsiback_do_cmd_fn(info)) {
+		case 1:
+			info->waiting_reqs = 1;
+		case 0:
+			break;
+		case -EACCES:
+			wait_event_interruptible(info->shutdown_wq,
+						 kthread_should_stop());
+			break;
+		default:
+			BUG();
+		}
+	}
+
+	return 0;
+}
+
+static void __vscsiif_name(struct vscsibk_info *info, char *buf)
+{
+	struct xenbus_device *dev = info->dev;
+	unsigned int domid, id;
+
+	if (sscanf(dev->nodename, "backend/vscsi/%u/%u", &domid, &id) == 2)
+		snprintf(buf, TASK_COMM_LEN, "vscsi.%u.%u", info->domid, id);
+	else
+		snprintf(buf, TASK_COMM_LEN, "vscsi.%u..", info->domid);
+}
+
+static int scsiback_map(struct vscsibk_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	unsigned int ring_ref, evtchn;
+	int err;
+	char name[TASK_COMM_LEN];
+
+	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;
+	}
+
+	err = scsiback_init_sring(info, ring_ref, evtchn);
+	if (err)
+		return err;
+
+	__vscsiif_name(info, name);
+
+	info->kthread = kthread_run(scsiback_schedule, info, name);
+	if (IS_ERR(info->kthread)) {
+		err = PTR_ERR(info->kthread);
+		info->kthread = NULL;
+		xenbus_dev_error(info->dev, err, "start vscsiif");
+		return err;
+	}
+
+	return 0;
+}
+
+/*
+  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) {
+		pr_err("xen-pvscsi: %s: kmalloc() error\n", __func__);
+		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);
+	kfree(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);
+	int err;
+
+	switch (frontend_state) {
+	case XenbusStateInitialising:
+		break;
+	case XenbusStateInitialised:
+		err = scsiback_map(info);
+		if (err)
+			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:
+		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);
+
+	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);
+	atomic_set(&info->nr_unreplied_reqs, 0);
+	init_waitqueue_head(&info->wq);
+	init_waitqueue_head(&info->shutdown_wq);
+	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) {
+		pr_err("Unable to allocate struct scsiback_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)
+{
+	struct scsiback_nacl *nacl;
+
+	nacl = kzalloc(sizeof(struct scsiback_nacl), GFP_KERNEL);
+	if (!nacl) {
+		pr_err("Unable to allocate struct scsiback_nacl\n");
+		return NULL;
+	}
+
+	return &nacl->se_node_acl;
+}
+
+static void
+scsiback_release_fabric_acl(struct se_portal_group *se_tpg,
+			     struct se_node_acl *se_nacl)
+{
+	struct scsiback_nacl *nacl = container_of(se_nacl,
+			struct scsiback_nacl, se_node_acl);
+	kfree(nacl);
+}
+
+static u32 scsiback_tpg_get_inst_index(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static struct se_node_acl *
+scsiback_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 scsiback_nacl *nacl;
+	u64 wwpn = 0;
+	u32 nexus_depth;
+
+	se_nacl_new = scsiback_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)) {
+		scsiback_release_fabric_acl(se_tpg, se_nacl_new);
+		return se_nacl;
+	}
+	/*
+	 * Locate our struct scsiback_nacl and set the FC Nport WWPN
+	 */
+	nacl = container_of(se_nacl, struct scsiback_nacl, se_node_acl);
+	nacl->iport_wwpn = wwpn;
+
+	return se_nacl;
+}
+
+static void scsiback_drop_nodeacl(struct se_node_acl *se_acl)
+{
+	struct scsiback_nacl *nacl = container_of(se_acl,
+				struct scsiback_nacl, se_node_acl);
+	core_tpg_del_initiator_node_acl(se_acl->se_tpg, se_acl, 1);
+	kfree(nacl);
+}
+
+static int scsiback_check_stop_free(struct se_cmd *se_cmd)
+{
+	return target_put_sess_cmd(se_cmd->se_sess, se_cmd);
+}
+
+static void scsiback_release_cmd(struct se_cmd *se_cmd)
+{
+}
+
+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)
+{
+	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 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);
+		pr_err("Unable to allocate struct scsiback_nexus\n");
+		return -ENOMEM;
+	}
+	/*
+	 *  Initialize the struct se_session pointer
+	 */
+	tv_nexus->tvn_se_sess = transport_init_session(TARGET_PROT_DIN_PASS |
+						       TARGET_PROT_DOUT_PASS);
+	if (IS_ERR(tv_nexus->tvn_se_sess)) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		kfree(tv_nexus);
+		return -ENOMEM;
+	}
+	se_sess = tv_nexus->tvn_se_sess;
+	/*
+	 * 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(&scsiback_mutex);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count++;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	mutex_unlock(&scsiback_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(&scsiback_mutex);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	mutex_unlock(&scsiback_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) {
+		pr_err("Unable to allocate struct scsiback_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,
+	.fabric_make_nodeacl		= scsiback_make_nodeacl,
+	.fabric_drop_nodeacl		= scsiback_drop_nodeacl,
+};
+
+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)) {
+		pr_err("target_fabric_configfs_init() failed\n");
+		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) {
+		pr_err("xen-pvscsi: target_fabric_configfs_register() failed\n");
+		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) {
+		pr_err("xen-pvscsi: can't init scsi cache\n");
+		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");
-- 
1.8.4.5

[PATCH V3 3/4] Introduce XEN scsiback module

[jgross]

From: Juergen Gross <jgross@suse.com>

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>
---
 drivers/xen/Kconfig        |    9 +
 drivers/xen/Makefile       |    1 +
 drivers/xen/xen-scsiback.c | 2282 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 2292 insertions(+)
 create mode 100644 drivers/xen/xen-scsiback.c

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 38fb36e..42fb963 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 45e00af..b42ee75 100644
--- a/drivers/xen/Makefile
+++ b/drivers/xen/Makefile
@@ -33,6 +33,7 @@ obj-$(CONFIG_XEN_STUB)			+= xen-stub.o
 obj-$(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_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..4a0d6e3
--- /dev/null
+++ b/drivers/xen/xen-scsiback.c
@@ -0,0 +1,2282 @@
+/*
+ * 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/kthread.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 evtchn;
+	unsigned int irq;
+
+	struct vscsiif_back_ring  ring;
+
+	spinlock_t ring_lock;
+	atomic_t nr_unreplied_reqs;
+
+	spinlock_t v2p_lock;
+	struct list_head v2p_entry_lists;
+
+	struct task_struct *kthread;
+	wait_queue_head_t waiting_to_free;
+	wait_queue_head_t wq;
+	wait_queue_head_t shutdown_wq;
+	unsigned int waiting_reqs;
+};
+
+/* 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 vscsibk_emulate {
+	void (*pre_function)(struct vscsibk_pend *, void *);
+	void (*post_function)(struct vscsibk_pend *, void *);
+};
+
+struct scsiback_nexus {
+	/* Pointer to TCM session for I_T Nexus */
+	struct se_session *tvn_se_sess;
+};
+
+struct scsiback_nacl {
+	/* Binary World Wide unique Port Name for pvscsi Initiator port */
+	u64 iport_wwpn;
+	/* ASCII formatted WWPN for Sas Initiator port */
+	char iport_name[VSCSI_NAMELEN];
+	/* Returned by scsiback_make_nodeacl() */
+	struct se_node_acl se_node_acl;
+};
+
+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_get(_b) (atomic_inc(&(_b)->nr_unreplied_reqs))
+#define scsiback_put(_b)				\
+	do {						\
+		if (atomic_dec_and_test(&(_b)->nr_unreplied_reqs))	\
+			wake_up(&(_b)->waiting_to_free);\
+	} while (0)
+
+#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 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);
+
+	kmem_cache_free(scsiback_cachep, pending_req);
+}
+
+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);
+
+	transport_generic_free_cmd(&pending_req->se_cmd, 0);
+}
+
+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));
+	se_cmd->prot_pto = true;
+
+	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) {
+		pr_err("xen-pvscsi: %s: kmalloc() error\n", __func__);
+		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_notify_work(struct vscsibk_info *info)
+{
+	info->waiting_reqs = 1;
+	wake_up(&info->wq);
+}
+
+static irqreturn_t scsiback_intr(int irq, void *dev_id)
+{
+	scsiback_notify_work((struct vscsibk_info *)dev_id);
+	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) {
+		pr_err("xen-pvscsi: Already connected through?\n");
+		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_irqhandler(
+			info->domid, evtchn,
+			scsiback_intr, 0, "vscsiif-backend", info);
+
+	if (err < 0)
+		goto unmap_page;
+
+	info->irq = err;
+
+	return 0;
+
+unmap_page:
+	xenbus_unmap_ring_vfree(info->dev, area);
+
+	return err;
+}
+
+static void scsiback_disconnect(struct vscsibk_info *info)
+{
+	if (info->kthread) {
+		kthread_stop(info->kthread);
+		info->kthread = NULL;
+		wake_up(&info->shutdown_wq);
+	}
+
+	wait_event(info->waiting_to_free,
+		atomic_read(&info->nr_unreplied_reqs) == 0);
+
+	if (info->irq) {
+		unbind_from_irqhandler(info->irq, info);
+		info->irq = 0;
+	}
+
+	if (info->ring.sring) {
+		xenbus_unmap_ring_vfree(info->dev, info->ring.sring);
+		info->ring.sring = NULL;
+	}
+}
+
+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) {
+		pr_err("xen-pvscsi: %s: kmalloc() error\n", __func__);
+		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);
+}
+
+/*
+  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 = 0;
+	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);
+		return -EACCES;
+	}
+
+	while ((rc != rp)) {
+		if (RING_REQUEST_CONS_OVERFLOW(ring, rc))
+			break;
+		pending_req = kmem_cache_alloc(scsiback_cachep, GFP_KERNEL);
+		if (NULL == pending_req) {
+			more_to_do = 1;
+			break;
+		}
+
+		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);
+			more_to_do = 1;
+			break;
+		}
+
+		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);
+			} 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);
+			break;
+		}
+
+		/* Yield point for this unbounded loop. */
+		cond_resched();
+	}
+
+	if (RING_HAS_UNCONSUMED_REQUESTS(ring))
+		more_to_do = 1;
+
+	return more_to_do;
+}
+
+static int scsiback_do_cmd_fn(struct vscsibk_info *info)
+{
+	int more_to_do;
+
+	do {
+		more_to_do = _scsiback_do_cmd_fn(info);
+		if (more_to_do)
+			break;
+
+		RING_FINAL_CHECK_FOR_REQUESTS(&info->ring, more_to_do);
+	} while (more_to_do);
+
+	return more_to_do;
+}
+
+static int scsiback_schedule(void *data)
+{
+	struct vscsibk_info *info = (struct vscsibk_info *)data;
+
+	while (!kthread_should_stop()) {
+		wait_event_interruptible(info->wq,
+			info->waiting_reqs || kthread_should_stop());
+
+		info->waiting_reqs = 0;
+		smp_mb();	/* waiting_reqs used by other thread */
+
+		switch (scsiback_do_cmd_fn(info)) {
+		case 1:
+			info->waiting_reqs = 1;
+		case 0:
+			break;
+		case -EACCES:
+			wait_event_interruptible(info->shutdown_wq,
+						 kthread_should_stop());
+			break;
+		default:
+			BUG();
+		}
+	}
+
+	return 0;
+}
+
+static void __vscsiif_name(struct vscsibk_info *info, char *buf)
+{
+	struct xenbus_device *dev = info->dev;
+	unsigned int domid, id;
+
+	if (sscanf(dev->nodename, "backend/vscsi/%u/%u", &domid, &id) == 2)
+		snprintf(buf, TASK_COMM_LEN, "vscsi.%u.%u", info->domid, id);
+	else
+		snprintf(buf, TASK_COMM_LEN, "vscsi.%u..", info->domid);
+}
+
+static int scsiback_map(struct vscsibk_info *info)
+{
+	struct xenbus_device *dev = info->dev;
+	unsigned int ring_ref, evtchn;
+	int err;
+	char name[TASK_COMM_LEN];
+
+	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;
+	}
+
+	err = scsiback_init_sring(info, ring_ref, evtchn);
+	if (err)
+		return err;
+
+	__vscsiif_name(info, name);
+
+	info->kthread = kthread_run(scsiback_schedule, info, name);
+	if (IS_ERR(info->kthread)) {
+		err = PTR_ERR(info->kthread);
+		info->kthread = NULL;
+		xenbus_dev_error(info->dev, err, "start vscsiif");
+		return err;
+	}
+
+	return 0;
+}
+
+/*
+  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) {
+		pr_err("xen-pvscsi: %s: kmalloc() error\n", __func__);
+		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);
+	kfree(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);
+	int err;
+
+	switch (frontend_state) {
+	case XenbusStateInitialising:
+		break;
+	case XenbusStateInitialised:
+		err = scsiback_map(info);
+		if (err)
+			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:
+		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);
+
+	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);
+	atomic_set(&info->nr_unreplied_reqs, 0);
+	init_waitqueue_head(&info->wq);
+	init_waitqueue_head(&info->shutdown_wq);
+	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) {
+		pr_err("Unable to allocate struct scsiback_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)
+{
+	struct scsiback_nacl *nacl;
+
+	nacl = kzalloc(sizeof(struct scsiback_nacl), GFP_KERNEL);
+	if (!nacl) {
+		pr_err("Unable to allocate struct scsiback_nacl\n");
+		return NULL;
+	}
+
+	return &nacl->se_node_acl;
+}
+
+static void
+scsiback_release_fabric_acl(struct se_portal_group *se_tpg,
+			     struct se_node_acl *se_nacl)
+{
+	struct scsiback_nacl *nacl = container_of(se_nacl,
+			struct scsiback_nacl, se_node_acl);
+	kfree(nacl);
+}
+
+static u32 scsiback_tpg_get_inst_index(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static struct se_node_acl *
+scsiback_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 scsiback_nacl *nacl;
+	u64 wwpn = 0;
+	u32 nexus_depth;
+
+	se_nacl_new = scsiback_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)) {
+		scsiback_release_fabric_acl(se_tpg, se_nacl_new);
+		return se_nacl;
+	}
+	/*
+	 * Locate our struct scsiback_nacl and set the FC Nport WWPN
+	 */
+	nacl = container_of(se_nacl, struct scsiback_nacl, se_node_acl);
+	nacl->iport_wwpn = wwpn;
+
+	return se_nacl;
+}
+
+static void scsiback_drop_nodeacl(struct se_node_acl *se_acl)
+{
+	struct scsiback_nacl *nacl = container_of(se_acl,
+				struct scsiback_nacl, se_node_acl);
+	core_tpg_del_initiator_node_acl(se_acl->se_tpg, se_acl, 1);
+	kfree(nacl);
+}
+
+static int scsiback_check_stop_free(struct se_cmd *se_cmd)
+{
+	return target_put_sess_cmd(se_cmd->se_sess, se_cmd);
+}
+
+static void scsiback_release_cmd(struct se_cmd *se_cmd)
+{
+}
+
+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)
+{
+	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 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);
+		pr_err("Unable to allocate struct scsiback_nexus\n");
+		return -ENOMEM;
+	}
+	/*
+	 *  Initialize the struct se_session pointer
+	 */
+	tv_nexus->tvn_se_sess = transport_init_session(TARGET_PROT_DIN_PASS |
+						       TARGET_PROT_DOUT_PASS);
+	if (IS_ERR(tv_nexus->tvn_se_sess)) {
+		mutex_unlock(&tpg->tv_tpg_mutex);
+		kfree(tv_nexus);
+		return -ENOMEM;
+	}
+	se_sess = tv_nexus->tvn_se_sess;
+	/*
+	 * 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(&scsiback_mutex);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count++;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	mutex_unlock(&scsiback_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(&scsiback_mutex);
+
+	mutex_lock(&tpg->tv_tpg_mutex);
+	tpg->tv_tpg_port_count--;
+	mutex_unlock(&tpg->tv_tpg_mutex);
+
+	mutex_unlock(&scsiback_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) {
+		pr_err("Unable to allocate struct scsiback_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,
+	.fabric_make_nodeacl		= scsiback_make_nodeacl,
+	.fabric_drop_nodeacl		= scsiback_drop_nodeacl,
+};
+
+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)) {
+		pr_err("target_fabric_configfs_init() failed\n");
+		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) {
+		pr_err("xen-pvscsi: target_fabric_configfs_register() failed\n");
+		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) {
+		pr_err("xen-pvscsi: can't init scsi cache\n");
+		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");
-- 
1.8.4.5

[PATCH V3 4/4] add xen pvscsi maintainer

[jgross]

From: Juergen Gross <jgross@suse.com>

Add myself as maintainer for the Xen pvSCSI stuff.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 MAINTAINERS | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index c2066f4..d020bfd 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10046,6 +10046,14 @@ S:	Supported
 F:	arch/x86/pci/*xen*
 F:	drivers/pci/*xen*
 
+XEN PVSCSI DRIVERS
+M:	Juergen Gross <jgross@suse.com>
+L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
+S:	Supported
+F:	drivers/scsi/xen-scsifront.c
+F:	drivers/xen/xen-scsiback.c
+F:	include/xen/interface/io/vscsiif.h
+
 XEN SWIOTLB SUBSYSTEM
 M:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
 L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
-- 
1.8.4.5

[PATCH V3 4/4] add xen pvscsi maintainer

[jgross]

From: Juergen Gross <jgross@suse.com>

Add myself as maintainer for the Xen pvSCSI stuff.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 MAINTAINERS | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index c2066f4..d020bfd 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10046,6 +10046,14 @@ S:	Supported
 F:	arch/x86/pci/*xen*
 F:	drivers/pci/*xen*
 
+XEN PVSCSI DRIVERS
+M:	Juergen Gross <jgross@suse.com>
+L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
+S:	Supported
+F:	drivers/scsi/xen-scsifront.c
+F:	drivers/xen/xen-scsiback.c
+F:	include/xen/interface/io/vscsiif.h
+
 XEN SWIOTLB SUBSYSTEM
 M:	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
 L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
-- 
1.8.4.5

Re: [Xen-devel] [PATCH V3 1/4] Add XEN pvSCSI protocol description

[Jan Beulich]

>>> On 04.08.14 at 10:27, <JGross@suse.com> wrote:
> +/* Requests from the frontend to the backend */
> +
> +/*
> + * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
> + * The target is specified via channel, id and lun.
> + */
> +#define VSCSIIF_ACT_SCSI_CDB		1
> +
> +/*
> + * Request abort of a running operation for the specified target given by
> + * channel, id, lun and the operation's rqid in ref_rqid.
> + */
> +#define VSCSIIF_ACT_SCSI_ABORT		2
> +
> +/*
> + * Request a device reset of the specified target (channel and id).
> + */
> +#define VSCSIIF_ACT_SCSI_RESET		3

While I realize you don't want to support it, leaving out
VSCSIIF_ACT_SCSI_SG_PRESET altogether from this header may
lead people to the false impression that its number is available for
other use. I would generally recommend the Linux headers to not
deviate from the master ones more than absolutely necessary,
keeping what isn't needed/wanted by Linux at least in commented
out form.

Jan

Re: [PATCH V3 1/4] Add XEN pvSCSI protocol description

[Jan Beulich]

>>> On 04.08.14 at 10:27, <JGross@suse.com> wrote:
> +/* Requests from the frontend to the backend */
> +
> +/*
> + * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
> + * The target is specified via channel, id and lun.
> + */
> +#define VSCSIIF_ACT_SCSI_CDB		1
> +
> +/*
> + * Request abort of a running operation for the specified target given by
> + * channel, id, lun and the operation's rqid in ref_rqid.
> + */
> +#define VSCSIIF_ACT_SCSI_ABORT		2
> +
> +/*
> + * Request a device reset of the specified target (channel and id).
> + */
> +#define VSCSIIF_ACT_SCSI_RESET		3

While I realize you don't want to support it, leaving out
VSCSIIF_ACT_SCSI_SG_PRESET altogether from this header may
lead people to the false impression that its number is available for
other use. I would generally recommend the Linux headers to not
deviate from the master ones more than absolutely necessary,
keeping what isn't needed/wanted by Linux at least in commented
out form.

Jan

Re: [Xen-devel] [PATCH V3 1/4] Add XEN pvSCSI protocol description

[Juergen Gross]

On 08/04/2014 12:10 PM, Jan Beulich wrote:
>>>> On 04.08.14 at 10:27, <JGross@suse.com> wrote:
>> +/* Requests from the frontend to the backend */
>> +
>> +/*
>> + * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
>> + * The target is specified via channel, id and lun.
>> + */
>> +#define VSCSIIF_ACT_SCSI_CDB		1
>> +
>> +/*
>> + * Request abort of a running operation for the specified target given by
>> + * channel, id, lun and the operation's rqid in ref_rqid.
>> + */
>> +#define VSCSIIF_ACT_SCSI_ABORT		2
>> +
>> +/*
>> + * Request a device reset of the specified target (channel and id).
>> + */
>> +#define VSCSIIF_ACT_SCSI_RESET		3
>
> While I realize you don't want to support it, leaving out
> VSCSIIF_ACT_SCSI_SG_PRESET altogether from this header may
> lead people to the false impression that its number is available for
> other use. I would generally recommend the Linux headers to not
> deviate from the master ones more than absolutely necessary,
> keeping what isn't needed/wanted by Linux at least in commented
> out form.

Okay. I'll re-add the #define


Juergen

Re: [PATCH V3 1/4] Add XEN pvSCSI protocol description

[Juergen Gross]

On 08/04/2014 12:10 PM, Jan Beulich wrote:
>>>> On 04.08.14 at 10:27, <JGross@suse.com> wrote:
>> +/* Requests from the frontend to the backend */
>> +
>> +/*
>> + * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
>> + * The target is specified via channel, id and lun.
>> + */
>> +#define VSCSIIF_ACT_SCSI_CDB		1
>> +
>> +/*
>> + * Request abort of a running operation for the specified target given by
>> + * channel, id, lun and the operation's rqid in ref_rqid.
>> + */
>> +#define VSCSIIF_ACT_SCSI_ABORT		2
>> +
>> +/*
>> + * Request a device reset of the specified target (channel and id).
>> + */
>> +#define VSCSIIF_ACT_SCSI_RESET		3
>
> While I realize you don't want to support it, leaving out
> VSCSIIF_ACT_SCSI_SG_PRESET altogether from this header may
> lead people to the false impression that its number is available for
> other use. I would generally recommend the Linux headers to not
> deviate from the master ones more than absolutely necessary,
> keeping what isn't needed/wanted by Linux at least in commented
> out form.

Okay. I'll re-add the #define


Juergen

Re: [PATCH V3 2/4] Introduce xen-scsifront module

[David Vrabel]

On 04/08/14 09:27, jgross@suse.com wrote:
> 
> +
> +static void scsifront_backend_changed(struct xenbus_device *dev,
> +				      enum xenbus_state backend_state)
> +{
> +	struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
> +
> +	DPRINTK("%p %u %u\n", dev, dev->state, backend_state);
> +
> +	switch (backend_state) {
> +	case XenbusStateUnknown:
> +	case XenbusStateInitialising:
> +	case XenbusStateInitWait:
> +	case XenbusStateInitialised:
> +		break;
> +
> +	case XenbusStateConnected:
> +		scsifront_read_backend_params(dev, info);
> +		if (xenbus_read_driver_state(dev->nodename) ==
> +			XenbusStateInitialised) {
> +			scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
> +		}
> +
> +		if (dev->state != XenbusStateConnected)
> +			xenbus_switch_state(dev, XenbusStateConnected);
> +		break;
> +
> +	case XenbusStateClosed:
> +		if (dev->state == XenbusStateClosed)
> +			break;
> +		/* Missed the backend's Closing state -- fallthrough */
> +	case XenbusStateClosing:
> +		scsifront_disconnect(info);
> +		break;
> +
> +	case XenbusStateReconfiguring:
> +		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_DEL_LUN);
> +		xenbus_switch_state(dev, XenbusStateReconfiguring);
> +		break;
> +
> +	case XenbusStateReconfigured:
> +		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
> +		xenbus_switch_state(dev, XenbusStateConnected);
> +		break;
> +	}
> +}

I would like to see this state machine in common code but I'm not going
to insist on it since this is a existing driver.

Xen related parts:

Acked-by: David Vrabel <david.vrabel@citrix.com>

David

Re: [PATCH V3 2/4] Introduce xen-scsifront module

[David Vrabel]

On 04/08/14 09:27, jgross@suse.com wrote:
> 
> +
> +static void scsifront_backend_changed(struct xenbus_device *dev,
> +				      enum xenbus_state backend_state)
> +{
> +	struct vscsifrnt_info *info = dev_get_drvdata(&dev->dev);
> +
> +	DPRINTK("%p %u %u\n", dev, dev->state, backend_state);
> +
> +	switch (backend_state) {
> +	case XenbusStateUnknown:
> +	case XenbusStateInitialising:
> +	case XenbusStateInitWait:
> +	case XenbusStateInitialised:
> +		break;
> +
> +	case XenbusStateConnected:
> +		scsifront_read_backend_params(dev, info);
> +		if (xenbus_read_driver_state(dev->nodename) ==
> +			XenbusStateInitialised) {
> +			scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
> +		}
> +
> +		if (dev->state != XenbusStateConnected)
> +			xenbus_switch_state(dev, XenbusStateConnected);
> +		break;
> +
> +	case XenbusStateClosed:
> +		if (dev->state == XenbusStateClosed)
> +			break;
> +		/* Missed the backend's Closing state -- fallthrough */
> +	case XenbusStateClosing:
> +		scsifront_disconnect(info);
> +		break;
> +
> +	case XenbusStateReconfiguring:
> +		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_DEL_LUN);
> +		xenbus_switch_state(dev, XenbusStateReconfiguring);
> +		break;
> +
> +	case XenbusStateReconfigured:
> +		scsifront_do_lun_hotplug(info, VSCSIFRONT_OP_ADD_LUN);
> +		xenbus_switch_state(dev, XenbusStateConnected);
> +		break;
> +	}
> +}

I would like to see this state machine in common code but I'm not going
to insist on it since this is a existing driver.

Xen related parts:

Acked-by: David Vrabel <david.vrabel@citrix.com>

David

Re: [PATCH V3 3/4] Introduce XEN scsiback module

[David Vrabel]

On 04/08/14 09:27, jgross@suse.com wrote:
> From: Juergen Gross <jgross@suse.com>
> 
> 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.

Xen related parts

Acked-by: David Vrabel <david.vrabel@citrix.com>

David

Re: [PATCH V3 3/4] Introduce XEN scsiback module

[David Vrabel]

On 04/08/14 09:27, jgross@suse.com wrote:
> From: Juergen Gross <jgross@suse.com>
> 
> 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.

Xen related parts

Acked-by: David Vrabel <david.vrabel@citrix.com>

David