/*******************************************************************************
   * Vhost kernel TCM fabric driver for virtio SCSI initiators
   *

   * (C) Copyright 2010-2013 Datera, Inc.

   * (C) Copyright 2010-2012 IBM Corp.
   *
   * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
   *

   * Authors: Nicholas A. Bellinger <nab@daterainc.com>

   *          Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   ****************************************************************************/
  
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <generated/utsrelease.h>
  #include <linux/utsname.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/kthread.h>
  #include <linux/types.h>
  #include <linux/string.h>
  #include <linux/configfs.h>
  #include <linux/ctype.h>
  #include <linux/compat.h>
  #include <linux/eventfd.h>

  #include <linux/fs.h>

  #include <linux/vmalloc.h>

  #include <linux/miscdevice.h>
  #include <asm/unaligned.h>

  #include <scsi/scsi_common.h>
  #include <scsi/scsi_proto.h>

  #include <target/target_core_base.h>
  #include <target/target_core_fabric.h>

  #include <linux/vhost.h>

  #include <linux/virtio_scsi.h>

  #include <linux/llist.h>

  #include <linux/bitmap.h>

  #include "vhost.h"

  #define VHOST_SCSI_VERSION  "v0.1"
  #define VHOST_SCSI_NAMELEN 256
  #define VHOST_SCSI_MAX_CDB_SIZE 32
  #define VHOST_SCSI_DEFAULT_TAGS 256
  #define VHOST_SCSI_PREALLOC_SGLS 2048
  #define VHOST_SCSI_PREALLOC_UPAGES 2048

  #define VHOST_SCSI_PREALLOC_PROT_SGLS 2048

  
  struct vhost_scsi_inflight {
  	/* Wait for the flush operation to finish */
  	struct completion comp;
  	/* Refcount for the inflight reqs */
  	struct kref kref;
  };

  struct vhost_scsi_cmd {

  	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
  	int tvc_vq_desc;
  	/* virtio-scsi initiator task attribute */
  	int tvc_task_attr;

  	/* virtio-scsi response incoming iovecs */
  	int tvc_in_iovs;

  	/* virtio-scsi initiator data direction */
  	enum dma_data_direction tvc_data_direction;
  	/* Expected data transfer length from virtio-scsi header */
  	u32 tvc_exp_data_len;
  	/* The Tag from include/linux/virtio_scsi.h:struct virtio_scsi_cmd_req */
  	u64 tvc_tag;
  	/* The number of scatterlists associated with this cmd */
  	u32 tvc_sgl_count;

  	u32 tvc_prot_sgl_count;

  	/* Saved unpacked SCSI LUN for vhost_scsi_submission_work() */

  	u32 tvc_lun;
  	/* Pointer to the SGL formatted memory from virtio-scsi */
  	struct scatterlist *tvc_sgl;

  	struct scatterlist *tvc_prot_sgl;

  	struct page **tvc_upages;

  	/* Pointer to response header iovec */

  	struct iovec tvc_resp_iov;

  	/* Pointer to vhost_scsi for our device */
  	struct vhost_scsi *tvc_vhost;
  	/* Pointer to vhost_virtqueue for the cmd */
  	struct vhost_virtqueue *tvc_vq;
  	/* Pointer to vhost nexus memory */

  	struct vhost_scsi_nexus *tvc_nexus;

  	/* The TCM I/O descriptor that is accessed via container_of() */
  	struct se_cmd tvc_se_cmd;

  	/* work item used for cmwq dispatch to vhost_scsi_submission_work() */

  	struct work_struct work;
  	/* Copy of the incoming SCSI command descriptor block (CDB) */

  	unsigned char tvc_cdb[VHOST_SCSI_MAX_CDB_SIZE];

  	/* Sense buffer that will be mapped into outgoing status */
  	unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
  	/* Completed commands list, serviced from vhost worker thread */
  	struct llist_node tvc_completion_list;
  	/* Used to track inflight cmd */
  	struct vhost_scsi_inflight *inflight;
  };

  struct vhost_scsi_nexus {

  	/* Pointer to TCM session for I_T Nexus */
  	struct se_session *tvn_se_sess;
  };

  struct vhost_scsi_tpg {

  	/* Vhost port target portal group tag for TCM */
  	u16 tport_tpgt;
  	/* Used to track number of TPG Port/Lun Links wrt to explict I_T Nexus shutdown */
  	int tv_tpg_port_count;
  	/* Used for vhost_scsi device reference to tpg_nexus, protected by tv_tpg_mutex */
  	int tv_tpg_vhost_count;

  	/* Used for enabling T10-PI with legacy devices */
  	int tv_fabric_prot_type;

  	/* list for vhost_scsi_list */

  	struct list_head tv_tpg_list;
  	/* Used to protect access for tpg_nexus */
  	struct mutex tv_tpg_mutex;
  	/* Pointer to the TCM VHost I_T Nexus for this TPG endpoint */

  	struct vhost_scsi_nexus *tpg_nexus;
  	/* Pointer back to vhost_scsi_tport */
  	struct vhost_scsi_tport *tport;
  	/* Returned by vhost_scsi_make_tpg() */

  	struct se_portal_group se_tpg;
  	/* Pointer back to vhost_scsi, protected by tv_tpg_mutex */
  	struct vhost_scsi *vhost_scsi;
  };

  struct vhost_scsi_tport {

  	/* SCSI protocol the tport is providing */
  	u8 tport_proto_id;
  	/* Binary World Wide unique Port Name for Vhost Target port */
  	u64 tport_wwpn;
  	/* ASCII formatted WWPN for Vhost Target port */

  	char tport_name[VHOST_SCSI_NAMELEN];
  	/* Returned by vhost_scsi_make_tport() */

  	struct se_wwn tport_wwn;
  };

  struct vhost_scsi_evt {

  	/* event to be sent to guest */
  	struct virtio_scsi_event event;
  	/* event list, serviced from vhost worker thread */
  	struct llist_node list;
  };

  enum {
  	VHOST_SCSI_VQ_CTL = 0,
  	VHOST_SCSI_VQ_EVT = 1,
  	VHOST_SCSI_VQ_IO = 2,
  };

  /* Note: can't set VIRTIO_F_VERSION_1 yet, since that implies ANY_LAYOUT. */

  enum {

  	VHOST_SCSI_FEATURES = VHOST_FEATURES | (1ULL << VIRTIO_SCSI_F_HOTPLUG) |

  					       (1ULL << VIRTIO_SCSI_F_T10_PI)

  };

  #define VHOST_SCSI_MAX_TARGET	256
  #define VHOST_SCSI_MAX_VQ	128

  #define VHOST_SCSI_MAX_EVENT	128

  struct vhost_scsi_virtqueue {
  	struct vhost_virtqueue vq;

  	/*
  	 * Reference counting for inflight reqs, used for flush operation. At
  	 * each time, one reference tracks new commands submitted, while we
  	 * wait for another one to reach 0.
  	 */

  	struct vhost_scsi_inflight inflights[2];

  	/*
  	 * Indicate current inflight in use, protected by vq->mutex.
  	 * Writers must also take dev mutex and flush under it.
  	 */

  	int inflight_idx;

  };

  struct vhost_scsi {

  	/* Protected by vhost_scsi->dev.mutex */

  	struct vhost_scsi_tpg **vs_tpg;

  	char vs_vhost_wwpn[TRANSPORT_IQN_LEN];

  	struct vhost_dev dev;

  	struct vhost_scsi_virtqueue vqs[VHOST_SCSI_MAX_VQ];

  
  	struct vhost_work vs_completion_work; /* cmd completion work item */

  	struct llist_head vs_completion_list; /* cmd completion queue */

  
  	struct vhost_work vs_event_work; /* evt injection work item */
  	struct llist_head vs_event_list; /* evt injection queue */
  
  	bool vs_events_missed; /* any missed events, protected by vq->mutex */
  	int vs_events_nr; /* num of pending events, protected by vq->mutex */

  };

  /*
   * Context for processing request and control queue operations.
   */
  struct vhost_scsi_ctx {
  	int head;
  	unsigned int out, in;
  	size_t req_size, rsp_size;
  	size_t out_size, in_size;
  	u8 *target, *lunp;
  	void *req;
  	struct iov_iter out_iter;
  };

  static struct workqueue_struct *vhost_scsi_workqueue;

  /* Global spinlock to protect vhost_scsi TPG list for vhost IOCTL access */
  static DEFINE_MUTEX(vhost_scsi_mutex);
  static LIST_HEAD(vhost_scsi_list);

  static void vhost_scsi_done_inflight(struct kref *kref)

  {
  	struct vhost_scsi_inflight *inflight;
  
  	inflight = container_of(kref, struct vhost_scsi_inflight, kref);
  	complete(&inflight->comp);
  }

  static void vhost_scsi_init_inflight(struct vhost_scsi *vs,

  				    struct vhost_scsi_inflight *old_inflight[])
  {
  	struct vhost_scsi_inflight *new_inflight;
  	struct vhost_virtqueue *vq;
  	int idx, i;
  
  	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
  		vq = &vs->vqs[i].vq;
  
  		mutex_lock(&vq->mutex);
  
  		/* store old infight */
  		idx = vs->vqs[i].inflight_idx;
  		if (old_inflight)
  			old_inflight[i] = &vs->vqs[i].inflights[idx];
  
  		/* setup new infight */
  		vs->vqs[i].inflight_idx = idx ^ 1;
  		new_inflight = &vs->vqs[i].inflights[idx ^ 1];
  		kref_init(&new_inflight->kref);
  		init_completion(&new_inflight->comp);
  
  		mutex_unlock(&vq->mutex);
  	}
  }
  
  static struct vhost_scsi_inflight *

  vhost_scsi_get_inflight(struct vhost_virtqueue *vq)

  {
  	struct vhost_scsi_inflight *inflight;
  	struct vhost_scsi_virtqueue *svq;
  
  	svq = container_of(vq, struct vhost_scsi_virtqueue, vq);
  	inflight = &svq->inflights[svq->inflight_idx];
  	kref_get(&inflight->kref);
  
  	return inflight;
  }

  static void vhost_scsi_put_inflight(struct vhost_scsi_inflight *inflight)

  {

  	kref_put(&inflight->kref, vhost_scsi_done_inflight);

  }

  static int vhost_scsi_check_true(struct se_portal_group *se_tpg)

  {
  	return 1;
  }

  static int vhost_scsi_check_false(struct se_portal_group *se_tpg)

  {
  	return 0;
  }

  static char *vhost_scsi_get_fabric_name(void)

  {
  	return "vhost";
  }

  static char *vhost_scsi_get_fabric_wwn(struct se_portal_group *se_tpg)

  {

  	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
  				struct vhost_scsi_tpg, se_tpg);
  	struct vhost_scsi_tport *tport = tpg->tport;

  
  	return &tport->tport_name[0];
  }

  static u16 vhost_scsi_get_tpgt(struct se_portal_group *se_tpg)

  {

  	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
  				struct vhost_scsi_tpg, se_tpg);

  	return tpg->tport_tpgt;
  }

  static int vhost_scsi_check_prot_fabric_only(struct se_portal_group *se_tpg)
  {
  	struct vhost_scsi_tpg *tpg = container_of(se_tpg,
  				struct vhost_scsi_tpg, se_tpg);
  
  	return tpg->tv_fabric_prot_type;
  }

  static u32 vhost_scsi_tpg_get_inst_index(struct se_portal_group *se_tpg)

  {
  	return 1;
  }

  static void vhost_scsi_release_cmd(struct se_cmd *se_cmd)

  {

  	struct vhost_scsi_cmd *tv_cmd = container_of(se_cmd,
  				struct vhost_scsi_cmd, tvc_se_cmd);

  	struct se_session *se_sess = tv_cmd->tvc_nexus->tvn_se_sess;

  	int i;

  
  	if (tv_cmd->tvc_sgl_count) {

  		for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
  			put_page(sg_page(&tv_cmd->tvc_sgl[i]));

  	}

  	if (tv_cmd->tvc_prot_sgl_count) {
  		for (i = 0; i < tv_cmd->tvc_prot_sgl_count; i++)
  			put_page(sg_page(&tv_cmd->tvc_prot_sgl[i]));
  	}

  	vhost_scsi_put_inflight(tv_cmd->inflight);

  	target_free_tag(se_sess, se_cmd);

  }

  static u32 vhost_scsi_sess_get_index(struct se_session *se_sess)

  {
  	return 0;
  }

  static int vhost_scsi_write_pending(struct se_cmd *se_cmd)

  {
  	/* Go ahead and process the write immediately */
  	target_execute_cmd(se_cmd);
  	return 0;
  }

  static int vhost_scsi_write_pending_status(struct se_cmd *se_cmd)

  {
  	return 0;
  }

  static void vhost_scsi_set_default_node_attrs(struct se_node_acl *nacl)

  {
  	return;
  }

  static int vhost_scsi_get_cmd_state(struct se_cmd *se_cmd)

  {
  	return 0;
  }

  static void vhost_scsi_complete_cmd(struct vhost_scsi_cmd *cmd)

  {

  	struct vhost_scsi *vs = cmd->tvc_vhost;

  	llist_add(&cmd->tvc_completion_list, &vs->vs_completion_list);

  
  	vhost_work_queue(&vs->dev, &vs->vs_completion_work);
  }

  static int vhost_scsi_queue_data_in(struct se_cmd *se_cmd)

  {

  	struct vhost_scsi_cmd *cmd = container_of(se_cmd,
  				struct vhost_scsi_cmd, tvc_se_cmd);

  	vhost_scsi_complete_cmd(cmd);

  	return 0;
  }

  static int vhost_scsi_queue_status(struct se_cmd *se_cmd)

  {

  	struct vhost_scsi_cmd *cmd = container_of(se_cmd,
  				struct vhost_scsi_cmd, tvc_se_cmd);

  	vhost_scsi_complete_cmd(cmd);

  	return 0;
  }

  static void vhost_scsi_queue_tm_rsp(struct se_cmd *se_cmd)

  {

  	return;

  }

  static void vhost_scsi_aborted_task(struct se_cmd *se_cmd)

  {
  	return;
  }

  static void vhost_scsi_free_evt(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)

  {
  	vs->vs_events_nr--;
  	kfree(evt);
  }

  static struct vhost_scsi_evt *
  vhost_scsi_allocate_evt(struct vhost_scsi *vs,

  		       u32 event, u32 reason)

  {

  	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;

  	struct vhost_scsi_evt *evt;

  
  	if (vs->vs_events_nr > VHOST_SCSI_MAX_EVENT) {
  		vs->vs_events_missed = true;
  		return NULL;
  	}
  
  	evt = kzalloc(sizeof(*evt), GFP_KERNEL);
  	if (!evt) {

  		vq_err(vq, "Failed to allocate vhost_scsi_evt
  ");

  		vs->vs_events_missed = true;
  		return NULL;
  	}

  	evt->event.event = cpu_to_vhost32(vq, event);
  	evt->event.reason = cpu_to_vhost32(vq, reason);

  	vs->vs_events_nr++;
  
  	return evt;
  }

  static void vhost_scsi_free_cmd(struct vhost_scsi_cmd *cmd)

  {

  	struct se_cmd *se_cmd = &cmd->tvc_se_cmd;

  
  	/* TODO locking against target/backend threads? */

  	transport_generic_free_cmd(se_cmd, 0);

  }

  static int vhost_scsi_check_stop_free(struct se_cmd *se_cmd)
  {

  	return target_put_sess_cmd(se_cmd);

  }

  static void

  vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)

  {

  	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;

  	struct virtio_scsi_event *event = &evt->event;
  	struct virtio_scsi_event __user *eventp;
  	unsigned out, in;
  	int head, ret;
  
  	if (!vq->private_data) {
  		vs->vs_events_missed = true;
  		return;
  	}
  
  again:
  	vhost_disable_notify(&vs->dev, vq);

  	head = vhost_get_vq_desc(vq, vq->iov,

  			ARRAY_SIZE(vq->iov), &out, &in,
  			NULL, NULL);
  	if (head < 0) {
  		vs->vs_events_missed = true;
  		return;
  	}
  	if (head == vq->num) {
  		if (vhost_enable_notify(&vs->dev, vq))
  			goto again;
  		vs->vs_events_missed = true;
  		return;
  	}
  
  	if ((vq->iov[out].iov_len != sizeof(struct virtio_scsi_event))) {
  		vq_err(vq, "Expecting virtio_scsi_event, got %zu bytes
  ",
  				vq->iov[out].iov_len);
  		vs->vs_events_missed = true;
  		return;
  	}
  
  	if (vs->vs_events_missed) {

  		event->event |= cpu_to_vhost32(vq, VIRTIO_SCSI_T_EVENTS_MISSED);

  		vs->vs_events_missed = false;
  	}
  
  	eventp = vq->iov[out].iov_base;
  	ret = __copy_to_user(eventp, event, sizeof(*event));
  	if (!ret)
  		vhost_add_used_and_signal(&vs->dev, vq, head, 0);
  	else

  		vq_err(vq, "Faulted on vhost_scsi_send_event
  ");

  }

  static void vhost_scsi_evt_work(struct vhost_work *work)

  {
  	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
  					vs_event_work);

  	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;

  	struct vhost_scsi_evt *evt, *t;

  	struct llist_node *llnode;
  
  	mutex_lock(&vq->mutex);
  	llnode = llist_del_all(&vs->vs_event_list);

  	llist_for_each_entry_safe(evt, t, llnode, list) {

  		vhost_scsi_do_evt_work(vs, evt);
  		vhost_scsi_free_evt(vs, evt);

  	}
  	mutex_unlock(&vq->mutex);
  }

  /* Fill in status and signal that we are done processing this command
   *
   * This is scheduled in the vhost work queue so we are called with the owner
   * process mm and can access the vring.
   */
  static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
  {
  	struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
  					vs_completion_work);

  	DECLARE_BITMAP(signal, VHOST_SCSI_MAX_VQ);

  	struct virtio_scsi_cmd_resp v_rsp;

  	struct vhost_scsi_cmd *cmd, *t;

  	struct llist_node *llnode;
  	struct se_cmd *se_cmd;

  	struct iov_iter iov_iter;

  	int ret, vq;

  	bitmap_zero(signal, VHOST_SCSI_MAX_VQ);

  	llnode = llist_del_all(&vs->vs_completion_list);

  	llist_for_each_entry_safe(cmd, t, llnode, tvc_completion_list) {

  		se_cmd = &cmd->tvc_se_cmd;

  
  		pr_debug("%s tv_cmd %p resid %u status %#02x
  ", __func__,

  			cmd, se_cmd->residual_count, se_cmd->scsi_status);

  
  		memset(&v_rsp, 0, sizeof(v_rsp));

  		v_rsp.resid = cpu_to_vhost32(cmd->tvc_vq, se_cmd->residual_count);

  		/* TODO is status_qualifier field needed? */
  		v_rsp.status = se_cmd->scsi_status;

  		v_rsp.sense_len = cpu_to_vhost32(cmd->tvc_vq,
  						 se_cmd->scsi_sense_length);

  		memcpy(v_rsp.sense, cmd->tvc_sense_buf,

  		       se_cmd->scsi_sense_length);

  		iov_iter_init(&iov_iter, READ, &cmd->tvc_resp_iov,

  			      cmd->tvc_in_iovs, sizeof(v_rsp));
  		ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
  		if (likely(ret == sizeof(v_rsp))) {

  			struct vhost_scsi_virtqueue *q;

  			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
  			q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);

  			vq = q - vs->vqs;

  			__set_bit(vq, signal);
  		} else

  			pr_err("Faulted on virtio_scsi_cmd_resp
  ");

  		vhost_scsi_free_cmd(cmd);

  	}

  	vq = -1;
  	while ((vq = find_next_bit(signal, VHOST_SCSI_MAX_VQ, vq + 1))
  		< VHOST_SCSI_MAX_VQ)

  		vhost_signal(&vs->dev, &vs->vqs[vq].vq);

  }

  static struct vhost_scsi_cmd *
  vhost_scsi_get_tag(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,

  		   unsigned char *cdb, u64 scsi_tag, u16 lun, u8 task_attr,
  		   u32 exp_data_len, int data_direction)

  {

  	struct vhost_scsi_cmd *cmd;
  	struct vhost_scsi_nexus *tv_nexus;

  	struct se_session *se_sess;

  	struct scatterlist *sg, *prot_sg;

  	struct page **pages;

  	int tag, cpu;

  	tv_nexus = tpg->tpg_nexus;

  	if (!tv_nexus) {

  		pr_err("Unable to locate active struct vhost_scsi_nexus
  ");

  		return ERR_PTR(-EIO);
  	}

  	se_sess = tv_nexus->tvn_se_sess;

  	tag = sbitmap_queue_get(&se_sess->sess_tag_pool, &cpu);

  	if (tag < 0) {

  		pr_err("Unable to obtain tag for vhost_scsi_cmd
  ");

  		return ERR_PTR(-ENOMEM);
  	}

  	cmd = &((struct vhost_scsi_cmd *)se_sess->sess_cmd_map)[tag];

  	sg = cmd->tvc_sgl;

  	prot_sg = cmd->tvc_prot_sgl;

  	pages = cmd->tvc_upages;

  	memset(cmd, 0, sizeof(*cmd));

  	cmd->tvc_sgl = sg;

  	cmd->tvc_prot_sgl = prot_sg;

  	cmd->tvc_upages = pages;

  	cmd->tvc_se_cmd.map_tag = tag;

  	cmd->tvc_se_cmd.map_cpu = cpu;

  	cmd->tvc_tag = scsi_tag;
  	cmd->tvc_lun = lun;
  	cmd->tvc_task_attr = task_attr;

  	cmd->tvc_exp_data_len = exp_data_len;
  	cmd->tvc_data_direction = data_direction;
  	cmd->tvc_nexus = tv_nexus;

  	cmd->inflight = vhost_scsi_get_inflight(vq);

  	memcpy(cmd->tvc_cdb, cdb, VHOST_SCSI_MAX_CDB_SIZE);

  	return cmd;

  }
  
  /*
   * Map a user memory range into a scatterlist
   *
   * Returns the number of scatterlist entries used or -errno on error.
   */

  static int

  vhost_scsi_map_to_sgl(struct vhost_scsi_cmd *cmd,

  		      struct iov_iter *iter,

  		      struct scatterlist *sgl,

  		      bool write)

  {

  	struct page **pages = cmd->tvc_upages;

  	struct scatterlist *sg = sgl;
  	ssize_t bytes;
  	size_t offset;
  	unsigned int npages = 0;

  	bytes = iov_iter_get_pages(iter, pages, LONG_MAX,
  				VHOST_SCSI_PREALLOC_UPAGES, &offset);

  	/* No pages were pinned */

  	if (bytes <= 0)
  		return bytes < 0 ? bytes : -EFAULT;

  	iov_iter_advance(iter, bytes);

  	while (bytes) {
  		unsigned n = min_t(unsigned, PAGE_SIZE - offset, bytes);
  		sg_set_page(sg++, pages[npages++], n, offset);
  		bytes -= n;
  		offset = 0;
  	}
  	return npages;

  }

  static int

  vhost_scsi_calc_sgls(struct iov_iter *iter, size_t bytes, int max_sgls)

  {

  	int sgl_count = 0;

  	if (!iter || !iter->iov) {
  		pr_err("%s: iter->iov is NULL, but expected bytes: %zu"
  		       " present
  ", __func__, bytes);
  		return -EINVAL;
  	}

  	sgl_count = iov_iter_npages(iter, 0xffff);
  	if (sgl_count > max_sgls) {
  		pr_err("%s: requested sgl_count: %d exceeds pre-allocated"
  		       " max_sgls: %d
  ", __func__, sgl_count, max_sgls);
  		return -EINVAL;

  	}

  	return sgl_count;
  }

  static int

  vhost_scsi_iov_to_sgl(struct vhost_scsi_cmd *cmd, bool write,
  		      struct iov_iter *iter,
  		      struct scatterlist *sg, int sg_count)

  {

  	struct scatterlist *p = sg;

  	int ret;

  	while (iov_iter_count(iter)) {
  		ret = vhost_scsi_map_to_sgl(cmd, iter, sg, write);

  		if (ret < 0) {

  			while (p < sg) {
  				struct page *page = sg_page(p++);

  				if (page)
  					put_page(page);
  			}

  			return ret;
  		}

  		sg += ret;

  	}
  	return 0;
  }

  static int

  vhost_scsi_mapal(struct vhost_scsi_cmd *cmd,

  		 size_t prot_bytes, struct iov_iter *prot_iter,
  		 size_t data_bytes, struct iov_iter *data_iter)
  {
  	int sgl_count, ret;
  	bool write = (cmd->tvc_data_direction == DMA_FROM_DEVICE);
  
  	if (prot_bytes) {
  		sgl_count = vhost_scsi_calc_sgls(prot_iter, prot_bytes,

  						 VHOST_SCSI_PREALLOC_PROT_SGLS);

  		if (sgl_count < 0)
  			return sgl_count;
  
  		sg_init_table(cmd->tvc_prot_sgl, sgl_count);
  		cmd->tvc_prot_sgl_count = sgl_count;
  		pr_debug("%s prot_sg %p prot_sgl_count %u
  ", __func__,
  			 cmd->tvc_prot_sgl, cmd->tvc_prot_sgl_count);
  
  		ret = vhost_scsi_iov_to_sgl(cmd, write, prot_iter,
  					    cmd->tvc_prot_sgl,
  					    cmd->tvc_prot_sgl_count);

  		if (ret < 0) {

  			cmd->tvc_prot_sgl_count = 0;
  			return ret;
  		}

  	}
  	sgl_count = vhost_scsi_calc_sgls(data_iter, data_bytes,

  					 VHOST_SCSI_PREALLOC_SGLS);

  	if (sgl_count < 0)
  		return sgl_count;
  
  	sg_init_table(cmd->tvc_sgl, sgl_count);
  	cmd->tvc_sgl_count = sgl_count;
  	pr_debug("%s data_sg %p data_sgl_count %u
  ", __func__,
  		  cmd->tvc_sgl, cmd->tvc_sgl_count);
  
  	ret = vhost_scsi_iov_to_sgl(cmd, write, data_iter,
  				    cmd->tvc_sgl, cmd->tvc_sgl_count);
  	if (ret < 0) {
  		cmd->tvc_sgl_count = 0;
  		return ret;

  	}
  	return 0;
  }

  static int vhost_scsi_to_tcm_attr(int attr)
  {
  	switch (attr) {
  	case VIRTIO_SCSI_S_SIMPLE:
  		return TCM_SIMPLE_TAG;
  	case VIRTIO_SCSI_S_ORDERED:
  		return TCM_ORDERED_TAG;
  	case VIRTIO_SCSI_S_HEAD:
  		return TCM_HEAD_TAG;
  	case VIRTIO_SCSI_S_ACA:
  		return TCM_ACA_TAG;
  	default:
  		break;
  	}
  	return TCM_SIMPLE_TAG;
  }

  static void vhost_scsi_submission_work(struct work_struct *work)

  {

  	struct vhost_scsi_cmd *cmd =
  		container_of(work, struct vhost_scsi_cmd, work);
  	struct vhost_scsi_nexus *tv_nexus;

  	struct se_cmd *se_cmd = &cmd->tvc_se_cmd;

  	struct scatterlist *sg_ptr, *sg_prot_ptr = NULL;
  	int rc;

  	/* FIXME: BIDI operation */

  	if (cmd->tvc_sgl_count) {
  		sg_ptr = cmd->tvc_sgl;

  
  		if (cmd->tvc_prot_sgl_count)
  			sg_prot_ptr = cmd->tvc_prot_sgl;
  		else
  			se_cmd->prot_pto = true;

  	} else {
  		sg_ptr = NULL;
  	}

  	tv_nexus = cmd->tvc_nexus;

  	se_cmd->tag = 0;

  	rc = target_submit_cmd_map_sgls(se_cmd, tv_nexus->tvn_se_sess,

  			cmd->tvc_cdb, &cmd->tvc_sense_buf[0],
  			cmd->tvc_lun, cmd->tvc_exp_data_len,

  			vhost_scsi_to_tcm_attr(cmd->tvc_task_attr),
  			cmd->tvc_data_direction, TARGET_SCF_ACK_KREF,
  			sg_ptr, cmd->tvc_sgl_count, NULL, 0, sg_prot_ptr,
  			cmd->tvc_prot_sgl_count);

  	if (rc < 0) {
  		transport_send_check_condition_and_sense(se_cmd,

  				TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE, 0);

  		transport_generic_free_cmd(se_cmd, 0);

  	}

  }

  static void
  vhost_scsi_send_bad_target(struct vhost_scsi *vs,
  			   struct vhost_virtqueue *vq,
  			   int head, unsigned out)

  {
  	struct virtio_scsi_cmd_resp __user *resp;
  	struct virtio_scsi_cmd_resp rsp;
  	int ret;
  
  	memset(&rsp, 0, sizeof(rsp));
  	rsp.response = VIRTIO_SCSI_S_BAD_TARGET;
  	resp = vq->iov[out].iov_base;
  	ret = __copy_to_user(resp, &rsp, sizeof(rsp));
  	if (!ret)
  		vhost_add_used_and_signal(&vs->dev, vq, head, 0);
  	else
  		pr_err("Faulted on virtio_scsi_cmd_resp
  ");
  }

  static int
  vhost_scsi_get_desc(struct vhost_scsi *vs, struct vhost_virtqueue *vq,
  		    struct vhost_scsi_ctx *vc)
  {
  	int ret = -ENXIO;
  
  	vc->head = vhost_get_vq_desc(vq, vq->iov,
  				     ARRAY_SIZE(vq->iov), &vc->out, &vc->in,
  				     NULL, NULL);
  
  	pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u
  ",
  		 vc->head, vc->out, vc->in);
  
  	/* On error, stop handling until the next kick. */
  	if (unlikely(vc->head < 0))
  		goto done;
  
  	/* Nothing new?  Wait for eventfd to tell us they refilled. */
  	if (vc->head == vq->num) {
  		if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
  			vhost_disable_notify(&vs->dev, vq);
  			ret = -EAGAIN;
  		}
  		goto done;
  	}
  
  	/*
  	 * Get the size of request and response buffers.
  	 * FIXME: Not correct for BIDI operation
  	 */
  	vc->out_size = iov_length(vq->iov, vc->out);
  	vc->in_size = iov_length(&vq->iov[vc->out], vc->in);
  
  	/*
  	 * Copy over the virtio-scsi request header, which for a
  	 * ANY_LAYOUT enabled guest may span multiple iovecs, or a
  	 * single iovec may contain both the header + outgoing
  	 * WRITE payloads.
  	 *
  	 * copy_from_iter() will advance out_iter, so that it will
  	 * point at the start of the outgoing WRITE payload, if
  	 * DMA_TO_DEVICE is set.
  	 */
  	iov_iter_init(&vc->out_iter, WRITE, vq->iov, vc->out, vc->out_size);
  	ret = 0;
  
  done:
  	return ret;
  }
  
  static int
  vhost_scsi_chk_size(struct vhost_virtqueue *vq, struct vhost_scsi_ctx *vc)
  {
  	if (unlikely(vc->in_size < vc->rsp_size)) {
  		vq_err(vq,
  		       "Response buf too small, need min %zu bytes got %zu",
  		       vc->rsp_size, vc->in_size);
  		return -EINVAL;
  	} else if (unlikely(vc->out_size < vc->req_size)) {
  		vq_err(vq,
  		       "Request buf too small, need min %zu bytes got %zu",
  		       vc->req_size, vc->out_size);
  		return -EIO;
  	}
  
  	return 0;
  }
  
  static int
  vhost_scsi_get_req(struct vhost_virtqueue *vq, struct vhost_scsi_ctx *vc,
  		   struct vhost_scsi_tpg **tpgp)
  {
  	int ret = -EIO;
  
  	if (unlikely(!copy_from_iter_full(vc->req, vc->req_size,
  					  &vc->out_iter))) {
  		vq_err(vq, "Faulted on copy_from_iter
  ");
  	} else if (unlikely(*vc->lunp != 1)) {
  		/* virtio-scsi spec requires byte 0 of the lun to be 1 */
  		vq_err(vq, "Illegal virtio-scsi lun: %u
  ", *vc->lunp);
  	} else {
  		struct vhost_scsi_tpg **vs_tpg, *tpg;
  
  		vs_tpg = vq->private_data;	/* validated at handler entry */
  
  		tpg = READ_ONCE(vs_tpg[*vc->target]);
  		if (unlikely(!tpg)) {
  			vq_err(vq, "Target 0x%x does not exist
  ", *vc->target);
  		} else {
  			if (tpgp)
  				*tpgp = tpg;
  			ret = 0;
  		}
  	}
  
  	return ret;
  }

  static void
  vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)

  {

  	struct vhost_scsi_tpg **vs_tpg, *tpg;

  	struct virtio_scsi_cmd_req v_req;

  	struct virtio_scsi_cmd_req_pi v_req_pi;

  	struct vhost_scsi_ctx vc;

  	struct vhost_scsi_cmd *cmd;

  	struct iov_iter in_iter, prot_iter, data_iter;

  	u64 tag;

  	u32 exp_data_len, data_direction;

  	int ret, prot_bytes;

  	u16 lun;

  	u8 task_attr;

  	bool t10_pi = vhost_has_feature(vq, VIRTIO_SCSI_F_T10_PI);

  	void *cdb;

  	mutex_lock(&vq->mutex);

  	/*
  	 * We can handle the vq only after the endpoint is setup by calling the
  	 * VHOST_SCSI_SET_ENDPOINT ioctl.

  	 */

  	vs_tpg = vq->private_data;

  	if (!vs_tpg)

  		goto out;

  	memset(&vc, 0, sizeof(vc));
  	vc.rsp_size = sizeof(struct virtio_scsi_cmd_resp);

  	vhost_disable_notify(&vs->dev, vq);
  
  	for (;;) {

  		ret = vhost_scsi_get_desc(vs, vq, &vc);
  		if (ret)
  			goto err;

  		/*
  		 * Setup pointers and values based upon different virtio-scsi
  		 * request header if T10_PI is enabled in KVM guest.
  		 */
  		if (t10_pi) {

  			vc.req = &v_req_pi;
  			vc.req_size = sizeof(v_req_pi);
  			vc.lunp = &v_req_pi.lun[0];
  			vc.target = &v_req_pi.lun[1];

  		} else {

  			vc.req = &v_req;
  			vc.req_size = sizeof(v_req);
  			vc.lunp = &v_req.lun[0];
  			vc.target = &v_req.lun[1];

  		}

  		/*

  		 * Validate the size of request and response buffers.
  		 * Check for a sane response buffer so we can report
  		 * early errors back to the guest.

  		 */

  		ret = vhost_scsi_chk_size(vq, &vc);
  		if (ret)
  			goto err;

  		ret = vhost_scsi_get_req(vq, &vc, &tpg);
  		if (ret)
  			goto err;
  
  		ret = -EIO;	/* bad target on any error from here on */

  		/*

  		 * Determine data_direction by calculating the total outgoing
  		 * iovec sizes + incoming iovec sizes vs. virtio-scsi request +
  		 * response headers respectively.

  		 *

  		 * For DMA_TO_DEVICE this is out_iter, which is already pointing
  		 * to the right place.
  		 *
  		 * For DMA_FROM_DEVICE, the iovec will be just past the end
  		 * of the virtio-scsi response header in either the same
  		 * or immediately following iovec.

  		 *

  		 * Any associated T10_PI bytes for the outgoing / incoming
  		 * payloads are included in calculation of exp_data_len here.

  		 */

  		prot_bytes = 0;

  		if (vc.out_size > vc.req_size) {

  			data_direction = DMA_TO_DEVICE;

  			exp_data_len = vc.out_size - vc.req_size;
  			data_iter = vc.out_iter;
  		} else if (vc.in_size > vc.rsp_size) {

  			data_direction = DMA_FROM_DEVICE;

  			exp_data_len = vc.in_size - vc.rsp_size;

  			iov_iter_init(&in_iter, READ, &vq->iov[vc.out], vc.in,
  				      vc.rsp_size + exp_data_len);
  			iov_iter_advance(&in_iter, vc.rsp_size);

  			data_iter = in_iter;
  		} else {
  			data_direction = DMA_NONE;
  			exp_data_len = 0;
  		}
  		/*
  		 * If T10_PI header + payload is present, setup prot_iter values
  		 * and recalculate data_iter for vhost_scsi_mapal() mapping to
  		 * host scatterlists via get_user_pages_fast().

  		 */

  		if (t10_pi) {

  			if (v_req_pi.pi_bytesout) {
  				if (data_direction != DMA_TO_DEVICE) {

  					vq_err(vq, "Received non zero pi_bytesout,"
  						" but wrong data_direction
  ");

  					goto err;

  				}

  				prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesout);

  			} else if (v_req_pi.pi_bytesin) {
  				if (data_direction != DMA_FROM_DEVICE) {

  					vq_err(vq, "Received non zero pi_bytesin,"
  						" but wrong data_direction
  ");

  					goto err;

  				}

  				prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesin);

  			}

  			/*

  			 * Set prot_iter to data_iter and truncate it to
  			 * prot_bytes, and advance data_iter past any

  			 * preceeding prot_bytes that may be present.
  			 *
  			 * Also fix up the exp_data_len to reflect only the
  			 * actual data payload length.
  			 */

  			if (prot_bytes) {

  				exp_data_len -= prot_bytes;
  				prot_iter = data_iter;

  				iov_iter_truncate(&prot_iter, prot_bytes);

  				iov_iter_advance(&data_iter, prot_bytes);

  			}

  			tag = vhost64_to_cpu(vq, v_req_pi.tag);

  			task_attr = v_req_pi.task_attr;
  			cdb = &v_req_pi.cdb[0];
  			lun = ((v_req_pi.lun[2] << 8) | v_req_pi.lun[3]) & 0x3FFF;
  		} else {

  			tag = vhost64_to_cpu(vq, v_req.tag);

  			task_attr = v_req.task_attr;
  			cdb = &v_req.cdb[0];
  			lun = ((v_req.lun[2] << 8) | v_req.lun[3]) & 0x3FFF;
  		}

  		/*

  		 * Check that the received CDB size does not exceeded our
  		 * hardcoded max for vhost-scsi, then get a pre-allocated
  		 * cmd descriptor for the new virtio-scsi tag.

  		 *
  		 * TODO what if cdb was too small for varlen cdb header?
  		 */

  		if (unlikely(scsi_command_size(cdb) > VHOST_SCSI_MAX_CDB_SIZE)) {

  			vq_err(vq, "Received SCSI CDB with command_size: %d that"
  				" exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d
  ",

  				scsi_command_size(cdb), VHOST_SCSI_MAX_CDB_SIZE);

  				goto err;

  		}

  		cmd = vhost_scsi_get_tag(vq, tpg, cdb, tag, lun, task_attr,

  					 exp_data_len + prot_bytes,
  					 data_direction);

  		if (IS_ERR(cmd)) {

  			vq_err(vq, "vhost_scsi_get_tag failed %ld
  ",

  			       PTR_ERR(cmd));

  			goto err;

  		}

  		cmd->tvc_vhost = vs;
  		cmd->tvc_vq = vq;

  		cmd->tvc_resp_iov = vq->iov[vc.out];
  		cmd->tvc_in_iovs = vc.in;

  		pr_debug("vhost_scsi got command opcode: %#02x, lun: %d
  ",

  			 cmd->tvc_cdb[0], cmd->tvc_lun);
  		pr_debug("cmd: %p exp_data_len: %d, prot_bytes: %d data_direction:"
  			 " %d
  ", cmd, exp_data_len, prot_bytes, data_direction);

  
  		if (data_direction != DMA_NONE) {

  			if (unlikely(vhost_scsi_mapal(cmd, prot_bytes,
  						      &prot_iter, exp_data_len,
  						      &data_iter))) {

  				vq_err(vq, "Failed to map iov to sgl
  ");

  				vhost_scsi_release_cmd(&cmd->tvc_se_cmd);

  				goto err;

  			}
  		}

  		/*
  		 * Save the descriptor from vhost_get_vq_desc() to be used to
  		 * complete the virtio-scsi request in TCM callback context via

  		 * vhost_scsi_queue_data_in() and vhost_scsi_queue_status()

  		 */

  		cmd->tvc_vq_desc = vc.head;

  		/*

  		 * Dispatch cmd descriptor for cmwq execution in process
  		 * context provided by vhost_scsi_workqueue.  This also ensures
  		 * cmd is executed on the same kworker CPU as this vhost
  		 * thread to gain positive L2 cache locality effects.

  		 */

  		INIT_WORK(&cmd->work, vhost_scsi_submission_work);
  		queue_work(vhost_scsi_workqueue, &cmd->work);

  		ret = 0;
  err:
  		/*
  		 * ENXIO:  No more requests, or read error, wait for next kick
  		 * EINVAL: Invalid response buffer, drop the request
  		 * EIO:    Respond with bad target
  		 * EAGAIN: Pending request
  		 */
  		if (ret == -ENXIO)
  			break;
  		else if (ret == -EIO)
  			vhost_scsi_send_bad_target(vs, vq, vc.head, vc.out);

  	}

  out:

  	mutex_unlock(&vq->mutex);

  }

  static void

  vhost_scsi_send_tmf_reject(struct vhost_scsi *vs,
  			   struct vhost_virtqueue *vq,
  			   struct vhost_scsi_ctx *vc)

  {
  	struct virtio_scsi_ctrl_tmf_resp __user *resp;
  	struct virtio_scsi_ctrl_tmf_resp rsp;
  	int ret;
  
  	pr_debug("%s
  ", __func__);
  	memset(&rsp, 0, sizeof(rsp));
  	rsp.response = VIRTIO_SCSI_S_FUNCTION_REJECTED;

  	resp = vq->iov[vc->out].iov_base;

  	ret = __copy_to_user(resp, &rsp, sizeof(rsp));
  	if (!ret)

  		vhost_add_used_and_signal(&vs->dev, vq, vc->head, 0);

  	else
  		pr_err("Faulted on virtio_scsi_ctrl_tmf_resp
  ");
  }
  
  static void
  vhost_scsi_send_an_resp(struct vhost_scsi *vs,

  			struct vhost_virtqueue *vq,
  			struct vhost_scsi_ctx *vc)

  {
  	struct virtio_scsi_ctrl_an_resp __user *resp;
  	struct virtio_scsi_ctrl_an_resp rsp;
  	int ret;
  
  	pr_debug("%s
  ", __func__);
  	memset(&rsp, 0, sizeof(rsp));	/* event_actual = 0 */
  	rsp.response = VIRTIO_SCSI_S_OK;

  	resp = vq->iov[vc->out].iov_base;

  	ret = __copy_to_user(resp, &rsp, sizeof(rsp));
  	if (!ret)

  		vhost_add_used_and_signal(&vs->dev, vq, vc->head, 0);

  	else
  		pr_err("Faulted on virtio_scsi_ctrl_an_resp
  ");
  }
  
  static void
  vhost_scsi_ctl_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
  {
  	union {
  		__virtio32 type;
  		struct virtio_scsi_ctrl_an_req an;
  		struct virtio_scsi_ctrl_tmf_req tmf;
  	} v_req;

  	struct vhost_scsi_ctx vc;
  	size_t typ_size;
  	int ret;

  
  	mutex_lock(&vq->mutex);
  	/*
  	 * We can handle the vq only after the endpoint is setup by calling the
  	 * VHOST_SCSI_SET_ENDPOINT ioctl.
  	 */
  	if (!vq->private_data)
  		goto out;

  	memset(&vc, 0, sizeof(vc));

  	vhost_disable_notify(&vs->dev, vq);
  
  	for (;;) {

  		ret = vhost_scsi_get_desc(vs, vq, &vc);
  		if (ret)
  			goto err;

  
  		/*

  		 * Get the request type first in order to setup
  		 * other parameters dependent on the type.

  		 */

  		vc.req = &v_req.type;

  		typ_size = sizeof(v_req.type);

  		if (unlikely(!copy_from_iter_full(vc.req, typ_size,
  						  &vc.out_iter))) {

  			vq_err(vq, "Faulted on copy_from_iter tmf type
  ");
  			/*

  			 * The size of the response buffer depends on the
  			 * request type and must be validated against it.

  			 * Since the request type is not known, don't send
  			 * a response.
  			 */
  			continue;
  		}
  
  		switch (v_req.type) {
  		case VIRTIO_SCSI_T_TMF:

  			vc.req = &v_req.tmf;
  			vc.req_size = sizeof(struct virtio_scsi_ctrl_tmf_req);
  			vc.rsp_size = sizeof(struct virtio_scsi_ctrl_tmf_resp);
  			vc.lunp = &v_req.tmf.lun[0];
  			vc.target = &v_req.tmf.lun[1];

  			break;
  		case VIRTIO_SCSI_T_AN_QUERY:
  		case VIRTIO_SCSI_T_AN_SUBSCRIBE:

  			vc.req = &v_req.an;
  			vc.req_size = sizeof(struct virtio_scsi_ctrl_an_req);
  			vc.rsp_size = sizeof(struct virtio_scsi_ctrl_an_resp);
  			vc.lunp = &v_req.an.lun[0];
  			vc.target = NULL;

  			break;
  		default:
  			vq_err(vq, "Unknown control request %d", v_req.type);
  			continue;
  		}
  
  		/*

  		 * Validate the size of request and response buffers.
  		 * Check for a sane response buffer so we can report
  		 * early errors back to the guest.

  		 */

  		ret = vhost_scsi_chk_size(vq, &vc);
  		if (ret)
  			goto err;

  		/*
  		 * Get the rest of the request now that its size is known.
  		 */
  		vc.req += typ_size;
  		vc.req_size -= typ_size;

  		ret = vhost_scsi_get_req(vq, &vc, NULL);
  		if (ret)
  			goto err;

  		if (v_req.type == VIRTIO_SCSI_T_TMF)

  			vhost_scsi_send_tmf_reject(vs, vq, &vc);

  		else
  			vhost_scsi_send_an_resp(vs, vq, &vc);
  err:
  		/*
  		 * ENXIO:  No more requests, or read error, wait for next kick
  		 * EINVAL: Invalid response buffer, drop the request
  		 * EIO:    Respond with bad target
  		 * EAGAIN: Pending request
  		 */
  		if (ret == -ENXIO)
  			break;
  		else if (ret == -EIO)
  			vhost_scsi_send_bad_target(vs, vq, vc.head, vc.out);

  	}
  out:
  	mutex_unlock(&vq->mutex);
  }

  static void vhost_scsi_ctl_handle_kick(struct vhost_work *work)
  {

  	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
  						poll.work);
  	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);

  	pr_debug("%s: The handling func for control queue.
  ", __func__);

  	vhost_scsi_ctl_handle_vq(vs, vq);

  }

  static void

  vhost_scsi_send_evt(struct vhost_scsi *vs,
  		   struct vhost_scsi_tpg *tpg,

  		   struct se_lun *lun,
  		   u32 event,
  		   u32 reason)

  {

  	struct vhost_scsi_evt *evt;

  	evt = vhost_scsi_allocate_evt(vs, event, reason);

  	if (!evt)
  		return;
  
  	if (tpg && lun) {
  		/* TODO: share lun setup code with virtio-scsi.ko */
  		/*
  		 * Note: evt->event is zeroed when we allocate it and
  		 * lun[4-7] need to be zero according to virtio-scsi spec.
  		 */
  		evt->event.lun[0] = 0x01;

  		evt->event.lun[1] = tpg->tport_tpgt;

  		if (lun->unpacked_lun >= 256)
  			evt->event.lun[2] = lun->unpacked_lun >> 8 | 0x40 ;
  		evt->event.lun[3] = lun->unpacked_lun & 0xFF;
  	}
  
  	llist_add(&evt->list, &vs->vs_event_list);
  	vhost_work_queue(&vs->dev, &vs->vs_event_work);
  }

  static void vhost_scsi_evt_handle_kick(struct vhost_work *work)
  {

  	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
  						poll.work);
  	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);
  
  	mutex_lock(&vq->mutex);
  	if (!vq->private_data)
  		goto out;
  
  	if (vs->vs_events_missed)

  		vhost_scsi_send_evt(vs, NULL, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);

  out:
  	mutex_unlock(&vq->mutex);

  }
  
  static void vhost_scsi_handle_kick(struct vhost_work *work)
  {
  	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
  						poll.work);
  	struct vhost_scsi *vs = container_of(vq->dev, struct vhost_scsi, dev);

  	vhost_scsi_handle_vq(vs, vq);

  }

  static void vhost_scsi_flush_vq(struct vhost_scsi *vs, int index)
  {

  	vhost_poll_flush(&vs->vqs[index].vq.poll);

  }

  /* Callers must hold dev mutex */

  static void vhost_scsi_flush(struct vhost_scsi *vs)
  {

  	struct vhost_scsi_inflight *old_inflight[VHOST_SCSI_MAX_VQ];

  	int i;

  	/* Init new inflight and remember the old inflight */

  	vhost_scsi_init_inflight(vs, old_inflight);

  
  	/*
  	 * The inflight->kref was initialized to 1. We decrement it here to
  	 * indicate the start of the flush operation so that it will reach 0
  	 * when all the reqs are finished.
  	 */
  	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)

  		kref_put(&old_inflight[i]->kref, vhost_scsi_done_inflight);

  
  	/* Flush both the vhost poll and vhost work */

  	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
  		vhost_scsi_flush_vq(vs, i);
  	vhost_work_flush(&vs->dev, &vs->vs_completion_work);

  	vhost_work_flush(&vs->dev, &vs->vs_event_work);

  
  	/* Wait for all reqs issued before the flush to be finished */
  	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++)
  		wait_for_completion(&old_inflight[i]->comp);

  }

  /*
   * Called from vhost_scsi_ioctl() context to walk the list of available

   * vhost_scsi_tpg with an active struct vhost_scsi_nexus

   *
   *  The lock nesting rule is:

   *    vhost_scsi_mutex -> vs->dev.mutex -> tpg->tv_tpg_mutex -> vq->mutex

   */

  static int
  vhost_scsi_set_endpoint(struct vhost_scsi *vs,
  			struct vhost_scsi_target *t)

  {

  	struct se_portal_group *se_tpg;

  	struct vhost_scsi_tport *tv_tport;
  	struct vhost_scsi_tpg *tpg;
  	struct vhost_scsi_tpg **vs_tpg;

  	struct vhost_virtqueue *vq;
  	int index, ret, i, len;

  	bool match = false;

  	mutex_lock(&vhost_scsi_mutex);

  	mutex_lock(&vs->dev.mutex);

  	/* Verify that ring has been setup correctly. */
  	for (index = 0; index < vs->dev.nvqs; ++index) {
  		/* Verify that ring has been setup correctly. */

  		if (!vhost_vq_access_ok(&vs->vqs[index].vq)) {

  			ret = -EFAULT;
  			goto out;

  		}
  	}

  	len = sizeof(vs_tpg[0]) * VHOST_SCSI_MAX_TARGET;
  	vs_tpg = kzalloc(len, GFP_KERNEL);
  	if (!vs_tpg) {

  		ret = -ENOMEM;
  		goto out;

  	}
  	if (vs->vs_tpg)
  		memcpy(vs_tpg, vs->vs_tpg, len);

  	list_for_each_entry(tpg, &vhost_scsi_list, tv_tpg_list) {

  		mutex_lock(&tpg->tv_tpg_mutex);
  		if (!tpg->tpg_nexus) {
  			mutex_unlock(&tpg->tv_tpg_mutex);

  			continue;
  		}

  		if (tpg->tv_tpg_vhost_count != 0) {
  			mutex_unlock(&tpg->tv_tpg_mutex);

  			continue;
  		}

  		tv_tport = tpg->tport;

  		if (!strcmp(tv_tport->tport_name, t->vhost_wwpn)) {

  			if (vs->vs_tpg && vs->vs_tpg[tpg->tport_tpgt]) {

  				kfree(vs_tpg);

  				mutex_unlock(&tpg->tv_tpg_mutex);

  				ret = -EEXIST;
  				goto out;

  			}

  			/*
  			 * In order to ensure individual vhost-scsi configfs
  			 * groups cannot be removed while in use by vhost ioctl,
  			 * go ahead and take an explicit se_tpg->tpg_group.cg_item
  			 * dependency now.
  			 */
  			se_tpg = &tpg->se_tpg;

  			ret = target_depend_item(&se_tpg->tpg_group.cg_item);

  			if (ret) {
  				pr_warn("configfs_depend_item() failed: %d
  ", ret);
  				kfree(vs_tpg);
  				mutex_unlock(&tpg->tv_tpg_mutex);
  				goto out;
  			}

  			tpg->tv_tpg_vhost_count++;
  			tpg->vhost_scsi = vs;
  			vs_tpg[tpg->tport_tpgt] = tpg;

  			smp_mb__after_atomic();

  			match = true;

  		}

  		mutex_unlock(&tpg->tv_tpg_mutex);

  	}

  
  	if (match) {
  		memcpy(vs->vs_vhost_wwpn, t->vhost_wwpn,
  		       sizeof(vs->vs_vhost_wwpn));

  		for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {

  			vq = &vs->vqs[i].vq;

  			mutex_lock(&vq->mutex);

  			vq->private_data = vs_tpg;

  			vhost_vq_init_access(vq);

  			mutex_unlock(&vq->mutex);
  		}

  		ret = 0;
  	} else {
  		ret = -EEXIST;
  	}

  	/*
  	 * Act as synchronize_rcu to make sure access to
  	 * old vs->vs_tpg is finished.
  	 */
  	vhost_scsi_flush(vs);
  	kfree(vs->vs_tpg);
  	vs->vs_tpg = vs_tpg;

  out:

  	mutex_unlock(&vs->dev.mutex);

  	mutex_unlock(&vhost_scsi_mutex);

  	return ret;

  }

  static int
  vhost_scsi_clear_endpoint(struct vhost_scsi *vs,
  			  struct vhost_scsi_target *t)

  {

  	struct se_portal_group *se_tpg;

  	struct vhost_scsi_tport *tv_tport;
  	struct vhost_scsi_tpg *tpg;

  	struct vhost_virtqueue *vq;
  	bool match = false;

  	int index, ret, i;
  	u8 target;

  	mutex_lock(&vhost_scsi_mutex);

  	mutex_lock(&vs->dev.mutex);
  	/* Verify that ring has been setup correctly. */
  	for (index = 0; index < vs->dev.nvqs; ++index) {

  		if (!vhost_vq_access_ok(&vs->vqs[index].vq)) {

  			ret = -EFAULT;

  			goto err_dev;

  		}
  	}

  
  	if (!vs->vs_tpg) {

  		ret = 0;
  		goto err_dev;

  	}

  	for (i = 0; i < VHOST_SCSI_MAX_TARGET; i++) {
  		target = i;

  		tpg = vs->vs_tpg[target];
  		if (!tpg)

  			continue;

  		mutex_lock(&tpg->tv_tpg_mutex);
  		tv_tport = tpg->tport;

  		if (!tv_tport) {
  			ret = -ENODEV;

  			goto err_tpg;

  		}
  
  		if (strcmp(tv_tport->tport_name, t->vhost_wwpn)) {

  			pr_warn("tv_tport->tport_name: %s, tpg->tport_tpgt: %hu"

  				" does not match t->vhost_wwpn: %s, t->vhost_tpgt: %hu
  ",

  				tv_tport->tport_name, tpg->tport_tpgt,

  				t->vhost_wwpn, t->vhost_tpgt);
  			ret = -EINVAL;

  			goto err_tpg;

  		}

  		tpg->tv_tpg_vhost_count--;
  		tpg->vhost_scsi = NULL;

  		vs->vs_tpg[target] = NULL;

  		match = true;

  		mutex_unlock(&tpg->tv_tpg_mutex);

  		/*
  		 * Release se_tpg->tpg_group.cg_item configfs dependency now
  		 * to allow vhost-scsi WWPN se_tpg->tpg_group shutdown to occur.
  		 */
  		se_tpg = &tpg->se_tpg;

  		target_undepend_item(&se_tpg->tpg_group.cg_item);

  	}

  	if (match) {
  		for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {

  			vq = &vs->vqs[i].vq;

  			mutex_lock(&vq->mutex);

  			vq->private_data = NULL;

  			mutex_unlock(&vq->mutex);
  		}
  	}
  	/*
  	 * Act as synchronize_rcu to make sure access to
  	 * old vs->vs_tpg is finished.
  	 */
  	vhost_scsi_flush(vs);
  	kfree(vs->vs_tpg);
  	vs->vs_tpg = NULL;

  	WARN_ON(vs->vs_events_nr);

  	mutex_unlock(&vs->dev.mutex);

  	mutex_unlock(&vhost_scsi_mutex);

  	return 0;

  err_tpg:

  	mutex_unlock(&tpg->tv_tpg_mutex);

  err_dev:

  	mutex_unlock(&vs->dev.mutex);

  	mutex_unlock(&vhost_scsi_mutex);

  	return ret;

  }

  static int vhost_scsi_set_features(struct vhost_scsi *vs, u64 features)
  {

  	struct vhost_virtqueue *vq;
  	int i;

  	if (features & ~VHOST_SCSI_FEATURES)
  		return -EOPNOTSUPP;
  
  	mutex_lock(&vs->dev.mutex);
  	if ((features & (1 << VHOST_F_LOG_ALL)) &&
  	    !vhost_log_access_ok(&vs->dev)) {
  		mutex_unlock(&vs->dev.mutex);
  		return -EFAULT;
  	}

  
  	for (i = 0; i < VHOST_SCSI_MAX_VQ; i++) {
  		vq = &vs->vqs[i].vq;
  		mutex_lock(&vq->mutex);
  		vq->acked_features = features;
  		mutex_unlock(&vq->mutex);
  	}

  	mutex_unlock(&vs->dev.mutex);
  	return 0;
  }