/******************************************************************************
   * grant_table.c
   *
   * Granting foreign access to our memory reservation.
   *
   * Copyright (c) 2005-2006, Christopher Clark
   * Copyright (c) 2004-2005, K A Fraser
   *
   * 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 pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

  #include <linux/sched.h>
  #include <linux/mm.h>

  #include <linux/slab.h>

  #include <linux/vmalloc.h>
  #include <linux/uaccess.h>

  #include <linux/io.h>

  #include <linux/delay.h>

  #include <linux/hardirq.h>

  #include <linux/workqueue.h>

  #include <linux/ratelimit.h>

  #include <xen/xen.h>

  #include <xen/interface/xen.h>
  #include <xen/page.h>
  #include <xen/grant_table.h>

  #include <xen/interface/memory.h>

  #include <xen/hvc-console.h>

  #include <xen/swiotlb-xen.h>

  #include <xen/balloon.h>

  #include <asm/xen/hypercall.h>

  #include <asm/xen/interface.h>

  
  #include <asm/pgtable.h>
  #include <asm/sync_bitops.h>

  /* External tools reserve first few grant table entries. */
  #define NR_RESERVED_ENTRIES 8
  #define GNTTAB_LIST_END 0xffffffff

  
  static grant_ref_t **gnttab_list;
  static unsigned int nr_grant_frames;

  static int gnttab_free_count;
  static grant_ref_t gnttab_free_head;
  static DEFINE_SPINLOCK(gnttab_list_lock);

  struct grant_frames xen_auto_xlat_grant_frames;

  static union {
  	struct grant_entry_v1 *v1;
  	void *addr;
  } gnttab_shared;
  
  /*This is a structure of function pointers for grant table*/
  struct gnttab_ops {
  	/*

  	 * Mapping a list of frames for storing grant entries. Frames parameter
  	 * is used to store grant table address when grant table being setup,
  	 * nr_gframes is the number of frames to map grant table. Returning
  	 * GNTST_okay means success and negative value means failure.

  	 */

  	int (*map_frames)(xen_pfn_t *frames, unsigned int nr_gframes);

  	/*
  	 * Release a list of frames which are mapped in map_frames for grant
  	 * entry status.
  	 */
  	void (*unmap_frames)(void);
  	/*

  	 * Introducing a valid entry into the grant table, granting the frame of
  	 * this grant entry to domain for accessing or transfering. Ref
  	 * parameter is reference of this introduced grant entry, domid is id of
  	 * granted domain, frame is the page frame to be granted, and flags is
  	 * status of the grant entry to be updated.

  	 */

  	void (*update_entry)(grant_ref_t ref, domid_t domid,
  			     unsigned long frame, unsigned flags);

  	/*

  	 * Stop granting a grant entry to domain for accessing. Ref parameter is
  	 * reference of a grant entry whose grant access will be stopped,
  	 * readonly is not in use in this function. If the grant entry is

  	 * currently mapped for reading or writing, just return failure(==0)
  	 * directly and don't tear down the grant access. Otherwise, stop grant
  	 * access for this entry and return success(==1).
  	 */

  	int (*end_foreign_access_ref)(grant_ref_t ref, int readonly);

  	/*

  	 * Stop granting a grant entry to domain for transfer. Ref parameter is
  	 * reference of a grant entry whose grant transfer will be stopped. If
  	 * tranfer has not started, just reclaim the grant entry and return
  	 * failure(==0). Otherwise, wait for the transfer to complete and then
  	 * return the frame.

  	 */

  	unsigned long (*end_foreign_transfer_ref)(grant_ref_t ref);

  	/*

  	 * Query the status of a grant entry. Ref parameter is reference of

  	 * queried grant entry, return value is the status of queried entry.
  	 * Detailed status(writing/reading) can be gotten from the return value
  	 * by bit operations.
  	 */

  	int (*query_foreign_access)(grant_ref_t ref);

  };

  struct unmap_refs_callback_data {
  	struct completion completion;
  	int result;
  };

  static const struct gnttab_ops *gnttab_interface;

  
  static int grant_table_version;

  static int grefs_per_grant_frame;

  
  static struct gnttab_free_callback *gnttab_free_callback_list;
  
  static int gnttab_expand(unsigned int req_entries);
  
  #define RPP (PAGE_SIZE / sizeof(grant_ref_t))
  
  static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
  {
  	return &gnttab_list[(entry) / RPP][(entry) % RPP];
  }
  /* This can be used as an l-value */
  #define gnttab_entry(entry) (*__gnttab_entry(entry))
  
  static int get_free_entries(unsigned count)
  {
  	unsigned long flags;

  	int ref, rc = 0;

  	grant_ref_t head;
  
  	spin_lock_irqsave(&gnttab_list_lock, flags);
  
  	if ((gnttab_free_count < count) &&
  	    ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
  		spin_unlock_irqrestore(&gnttab_list_lock, flags);
  		return rc;
  	}
  
  	ref = head = gnttab_free_head;
  	gnttab_free_count -= count;
  	while (count-- > 1)
  		head = gnttab_entry(head);
  	gnttab_free_head = gnttab_entry(head);
  	gnttab_entry(head) = GNTTAB_LIST_END;
  
  	spin_unlock_irqrestore(&gnttab_list_lock, flags);
  
  	return ref;
  }
  
  static void do_free_callbacks(void)
  {
  	struct gnttab_free_callback *callback, *next;
  
  	callback = gnttab_free_callback_list;
  	gnttab_free_callback_list = NULL;
  
  	while (callback != NULL) {
  		next = callback->next;
  		if (gnttab_free_count >= callback->count) {
  			callback->next = NULL;
  			callback->fn(callback->arg);
  		} else {
  			callback->next = gnttab_free_callback_list;
  			gnttab_free_callback_list = callback;
  		}
  		callback = next;
  	}
  }
  
  static inline void check_free_callbacks(void)
  {
  	if (unlikely(gnttab_free_callback_list))
  		do_free_callbacks();
  }
  
  static void put_free_entry(grant_ref_t ref)
  {
  	unsigned long flags;
  	spin_lock_irqsave(&gnttab_list_lock, flags);
  	gnttab_entry(ref) = gnttab_free_head;
  	gnttab_free_head = ref;
  	gnttab_free_count++;
  	check_free_callbacks();
  	spin_unlock_irqrestore(&gnttab_list_lock, flags);
  }

  /*

   * Following applies to gnttab_update_entry_v1.

   * Introducing a valid entry into the grant table:
   *  1. Write ent->domid.
   *  2. Write ent->frame:
   *      GTF_permit_access:   Frame to which access is permitted.
   *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
   *                           frame, or zero if none.
   *  3. Write memory barrier (WMB).
   *  4. Write ent->flags, inc. valid type.
   */
  static void gnttab_update_entry_v1(grant_ref_t ref, domid_t domid,
  				   unsigned long frame, unsigned flags)

  {

  	gnttab_shared.v1[ref].domid = domid;
  	gnttab_shared.v1[ref].frame = frame;

  	wmb();

  	gnttab_shared.v1[ref].flags = flags;

  }
  
  /*
   * Public grant-issuing interface functions
   */
  void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
  				     unsigned long frame, int readonly)
  {

  	gnttab_interface->update_entry(ref, domid, frame,

  			   GTF_permit_access | (readonly ? GTF_readonly : 0));
  }
  EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);
  
  int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
  				int readonly)
  {
  	int ref;
  
  	ref = get_free_entries(1);
  	if (unlikely(ref < 0))
  		return -ENOSPC;
  
  	gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);
  
  	return ref;
  }
  EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);

  static int gnttab_query_foreign_access_v1(grant_ref_t ref)

  {

  	return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
  }

  int gnttab_query_foreign_access(grant_ref_t ref)
  {
  	return gnttab_interface->query_foreign_access(ref);

  }
  EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);

  static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref, int readonly)

  {
  	u16 flags, nflags;

  	u16 *pflags;

  	pflags = &gnttab_shared.v1[ref].flags;
  	nflags = *pflags;

  	do {
  		flags = nflags;

  		if (flags & (GTF_reading|GTF_writing))

  			return 0;

  	} while ((nflags = sync_cmpxchg(pflags, flags, 0)) != flags);

  
  	return 1;
  }

  static inline int _gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)

  {
  	return gnttab_interface->end_foreign_access_ref(ref, readonly);
  }

  
  int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
  {
  	if (_gnttab_end_foreign_access_ref(ref, readonly))
  		return 1;
  	pr_warn("WARNING: g.e. %#x still in use!
  ", ref);
  	return 0;
  }

  EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);

  struct deferred_entry {
  	struct list_head list;
  	grant_ref_t ref;
  	bool ro;
  	uint16_t warn_delay;
  	struct page *page;
  };
  static LIST_HEAD(deferred_list);
  static void gnttab_handle_deferred(unsigned long);
  static DEFINE_TIMER(deferred_timer, gnttab_handle_deferred, 0, 0);
  
  static void gnttab_handle_deferred(unsigned long unused)
  {
  	unsigned int nr = 10;
  	struct deferred_entry *first = NULL;
  	unsigned long flags;
  
  	spin_lock_irqsave(&gnttab_list_lock, flags);
  	while (nr--) {
  		struct deferred_entry *entry
  			= list_first_entry(&deferred_list,
  					   struct deferred_entry, list);
  
  		if (entry == first)
  			break;
  		list_del(&entry->list);
  		spin_unlock_irqrestore(&gnttab_list_lock, flags);
  		if (_gnttab_end_foreign_access_ref(entry->ref, entry->ro)) {
  			put_free_entry(entry->ref);
  			if (entry->page) {
  				pr_debug("freeing g.e. %#x (pfn %#lx)
  ",
  					 entry->ref, page_to_pfn(entry->page));

  				put_page(entry->page);

  			} else
  				pr_info("freeing g.e. %#x
  ", entry->ref);
  			kfree(entry);
  			entry = NULL;
  		} else {
  			if (!--entry->warn_delay)

  				pr_info("g.e. %#x still pending
  ", entry->ref);

  			if (!first)
  				first = entry;
  		}
  		spin_lock_irqsave(&gnttab_list_lock, flags);
  		if (entry)
  			list_add_tail(&entry->list, &deferred_list);
  		else if (list_empty(&deferred_list))
  			break;
  	}
  	if (!list_empty(&deferred_list) && !timer_pending(&deferred_timer)) {
  		deferred_timer.expires = jiffies + HZ;
  		add_timer(&deferred_timer);
  	}
  	spin_unlock_irqrestore(&gnttab_list_lock, flags);
  }
  
  static void gnttab_add_deferred(grant_ref_t ref, bool readonly,
  				struct page *page)
  {
  	struct deferred_entry *entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
  	const char *what = KERN_WARNING "leaking";
  
  	if (entry) {
  		unsigned long flags;
  
  		entry->ref = ref;
  		entry->ro = readonly;
  		entry->page = page;
  		entry->warn_delay = 60;
  		spin_lock_irqsave(&gnttab_list_lock, flags);
  		list_add_tail(&entry->list, &deferred_list);
  		if (!timer_pending(&deferred_timer)) {
  			deferred_timer.expires = jiffies + HZ;
  			add_timer(&deferred_timer);
  		}
  		spin_unlock_irqrestore(&gnttab_list_lock, flags);
  		what = KERN_DEBUG "deferring";
  	}
  	printk("%s g.e. %#x (pfn %#lx)
  ",
  	       what, ref, page ? page_to_pfn(page) : -1);
  }

  void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
  			       unsigned long page)
  {
  	if (gnttab_end_foreign_access_ref(ref, readonly)) {
  		put_free_entry(ref);
  		if (page != 0)

  			put_page(virt_to_page(page));

  	} else
  		gnttab_add_deferred(ref, readonly,
  				    page ? virt_to_page(page) : NULL);

  }
  EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
  
  int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)
  {
  	int ref;
  
  	ref = get_free_entries(1);
  	if (unlikely(ref < 0))
  		return -ENOSPC;
  	gnttab_grant_foreign_transfer_ref(ref, domid, pfn);
  
  	return ref;
  }
  EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);
  
  void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,
  				       unsigned long pfn)
  {

  	gnttab_interface->update_entry(ref, domid, pfn, GTF_accept_transfer);

  }
  EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);

  static unsigned long gnttab_end_foreign_transfer_ref_v1(grant_ref_t ref)

  {
  	unsigned long frame;
  	u16           flags;

  	u16          *pflags;
  
  	pflags = &gnttab_shared.v1[ref].flags;

  
  	/*
  	 * If a transfer is not even yet started, try to reclaim the grant
  	 * reference and return failure (== 0).
  	 */

  	while (!((flags = *pflags) & GTF_transfer_committed)) {
  		if (sync_cmpxchg(pflags, flags, 0) == flags)

  			return 0;
  		cpu_relax();
  	}
  
  	/* If a transfer is in progress then wait until it is completed. */
  	while (!(flags & GTF_transfer_completed)) {

  		flags = *pflags;

  		cpu_relax();
  	}
  
  	rmb();	/* Read the frame number /after/ reading completion status. */

  	frame = gnttab_shared.v1[ref].frame;

  	BUG_ON(frame == 0);
  
  	return frame;
  }

  
  unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
  {
  	return gnttab_interface->end_foreign_transfer_ref(ref);
  }

  EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);
  
  unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)
  {
  	unsigned long frame = gnttab_end_foreign_transfer_ref(ref);
  	put_free_entry(ref);
  	return frame;
  }
  EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);
  
  void gnttab_free_grant_reference(grant_ref_t ref)
  {
  	put_free_entry(ref);
  }
  EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);
  
  void gnttab_free_grant_references(grant_ref_t head)
  {
  	grant_ref_t ref;
  	unsigned long flags;
  	int count = 1;
  	if (head == GNTTAB_LIST_END)
  		return;
  	spin_lock_irqsave(&gnttab_list_lock, flags);
  	ref = head;
  	while (gnttab_entry(ref) != GNTTAB_LIST_END) {
  		ref = gnttab_entry(ref);
  		count++;
  	}
  	gnttab_entry(ref) = gnttab_free_head;
  	gnttab_free_head = head;
  	gnttab_free_count += count;
  	check_free_callbacks();
  	spin_unlock_irqrestore(&gnttab_list_lock, flags);
  }
  EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
  
  int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
  {
  	int h = get_free_entries(count);
  
  	if (h < 0)
  		return -ENOSPC;
  
  	*head = h;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);
  
  int gnttab_empty_grant_references(const grant_ref_t *private_head)
  {
  	return (*private_head == GNTTAB_LIST_END);
  }
  EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);
  
  int gnttab_claim_grant_reference(grant_ref_t *private_head)
  {
  	grant_ref_t g = *private_head;
  	if (unlikely(g == GNTTAB_LIST_END))
  		return -ENOSPC;
  	*private_head = gnttab_entry(g);
  	return g;
  }
  EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);
  
  void gnttab_release_grant_reference(grant_ref_t *private_head,
  				    grant_ref_t release)
  {
  	gnttab_entry(release) = *private_head;
  	*private_head = release;
  }
  EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);
  
  void gnttab_request_free_callback(struct gnttab_free_callback *callback,
  				  void (*fn)(void *), void *arg, u16 count)
  {
  	unsigned long flags;

  	struct gnttab_free_callback *cb;

  	spin_lock_irqsave(&gnttab_list_lock, flags);

  
  	/* Check if the callback is already on the list */
  	cb = gnttab_free_callback_list;
  	while (cb) {
  		if (cb == callback)
  			goto out;
  		cb = cb->next;
  	}

  	callback->fn = fn;
  	callback->arg = arg;
  	callback->count = count;
  	callback->next = gnttab_free_callback_list;
  	gnttab_free_callback_list = callback;
  	check_free_callbacks();
  out:
  	spin_unlock_irqrestore(&gnttab_list_lock, flags);
  }
  EXPORT_SYMBOL_GPL(gnttab_request_free_callback);
  
  void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
  {
  	struct gnttab_free_callback **pcb;
  	unsigned long flags;
  
  	spin_lock_irqsave(&gnttab_list_lock, flags);
  	for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
  		if (*pcb == callback) {
  			*pcb = callback->next;
  			break;
  		}
  	}
  	spin_unlock_irqrestore(&gnttab_list_lock, flags);
  }
  EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
  
  static int grow_gnttab_list(unsigned int more_frames)
  {
  	unsigned int new_nr_grant_frames, extra_entries, i;

  	unsigned int nr_glist_frames, new_nr_glist_frames;

  	BUG_ON(grefs_per_grant_frame == 0);

  	new_nr_grant_frames = nr_grant_frames + more_frames;

  	extra_entries       = more_frames * grefs_per_grant_frame;

  	nr_glist_frames = (nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;

  	new_nr_glist_frames =

  		(new_nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;

  	for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {

  		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
  		if (!gnttab_list[i])
  			goto grow_nomem;
  	}

  	for (i = grefs_per_grant_frame * nr_grant_frames;
  	     i < grefs_per_grant_frame * new_nr_grant_frames - 1; i++)

  		gnttab_entry(i) = i + 1;
  
  	gnttab_entry(i) = gnttab_free_head;

  	gnttab_free_head = grefs_per_grant_frame * nr_grant_frames;

  	gnttab_free_count += extra_entries;
  
  	nr_grant_frames = new_nr_grant_frames;
  
  	check_free_callbacks();
  
  	return 0;
  
  grow_nomem:

  	while (i-- > nr_glist_frames)

  		free_page((unsigned long) gnttab_list[i]);
  	return -ENOMEM;
  }
  
  static unsigned int __max_nr_grant_frames(void)
  {
  	struct gnttab_query_size query;
  	int rc;
  
  	query.dom = DOMID_SELF;
  
  	rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
  	if ((rc < 0) || (query.status != GNTST_okay))
  		return 4; /* Legacy max supported number of frames */
  
  	return query.max_nr_frames;
  }

  unsigned int gnttab_max_grant_frames(void)

  {
  	unsigned int xen_max = __max_nr_grant_frames();

  	static unsigned int boot_max_nr_grant_frames;
  
  	/* First time, initialize it properly. */
  	if (!boot_max_nr_grant_frames)
  		boot_max_nr_grant_frames = __max_nr_grant_frames();

  
  	if (xen_max > boot_max_nr_grant_frames)
  		return boot_max_nr_grant_frames;
  	return xen_max;
  }

  EXPORT_SYMBOL_GPL(gnttab_max_grant_frames);

  int gnttab_setup_auto_xlat_frames(phys_addr_t addr)

  {
  	xen_pfn_t *pfn;
  	unsigned int max_nr_gframes = __max_nr_grant_frames();
  	unsigned int i;
  	void *vaddr;
  
  	if (xen_auto_xlat_grant_frames.count)
  		return -EINVAL;

  	vaddr = xen_remap(addr, XEN_PAGE_SIZE * max_nr_gframes);

  	if (vaddr == NULL) {

  		pr_warn("Failed to ioremap gnttab share frames (addr=%pa)!
  ",
  			&addr);

  		return -ENOMEM;
  	}
  	pfn = kcalloc(max_nr_gframes, sizeof(pfn[0]), GFP_KERNEL);
  	if (!pfn) {
  		xen_unmap(vaddr);
  		return -ENOMEM;
  	}
  	for (i = 0; i < max_nr_gframes; i++)

  		pfn[i] = XEN_PFN_DOWN(addr) + i;

  
  	xen_auto_xlat_grant_frames.vaddr = vaddr;
  	xen_auto_xlat_grant_frames.pfn = pfn;
  	xen_auto_xlat_grant_frames.count = max_nr_gframes;
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(gnttab_setup_auto_xlat_frames);
  
  void gnttab_free_auto_xlat_frames(void)
  {
  	if (!xen_auto_xlat_grant_frames.count)
  		return;
  	kfree(xen_auto_xlat_grant_frames.pfn);
  	xen_unmap(xen_auto_xlat_grant_frames.vaddr);
  
  	xen_auto_xlat_grant_frames.pfn = NULL;
  	xen_auto_xlat_grant_frames.count = 0;
  	xen_auto_xlat_grant_frames.vaddr = NULL;
  }
  EXPORT_SYMBOL_GPL(gnttab_free_auto_xlat_frames);

  /**
   * gnttab_alloc_pages - alloc pages suitable for grant mapping into
   * @nr_pages: number of pages to alloc
   * @pages: returns the pages
   */
  int gnttab_alloc_pages(int nr_pages, struct page **pages)
  {

  	int i;

  	int ret;

  	ret = alloc_xenballooned_pages(nr_pages, pages);

  	if (ret < 0)
  		return ret;

  	for (i = 0; i < nr_pages; i++) {
  #if BITS_PER_LONG < 64
  		struct xen_page_foreign *foreign;
  
  		foreign = kzalloc(sizeof(*foreign), GFP_KERNEL);
  		if (!foreign) {
  			gnttab_free_pages(nr_pages, pages);
  			return -ENOMEM;
  		}
  		set_page_private(pages[i], (unsigned long)foreign);
  #endif
  		SetPagePrivate(pages[i]);
  	}

  	return 0;
  }
  EXPORT_SYMBOL(gnttab_alloc_pages);
  
  /**
   * gnttab_free_pages - free pages allocated by gnttab_alloc_pages()
   * @nr_pages; number of pages to free
   * @pages: the pages
   */
  void gnttab_free_pages(int nr_pages, struct page **pages)
  {

  	int i;
  
  	for (i = 0; i < nr_pages; i++) {
  		if (PagePrivate(pages[i])) {
  #if BITS_PER_LONG < 64
  			kfree((void *)page_private(pages[i]));
  #endif
  			ClearPagePrivate(pages[i]);
  		}
  	}

  	free_xenballooned_pages(nr_pages, pages);
  }
  EXPORT_SYMBOL(gnttab_free_pages);

  /* Handling of paged out grant targets (GNTST_eagain) */
  #define MAX_DELAY 256
  static inline void
  gnttab_retry_eagain_gop(unsigned int cmd, void *gop, int16_t *status,
  						const char *func)
  {
  	unsigned delay = 1;
  
  	do {
  		BUG_ON(HYPERVISOR_grant_table_op(cmd, gop, 1));
  		if (*status == GNTST_eagain)
  			msleep(delay++);
  	} while ((*status == GNTST_eagain) && (delay < MAX_DELAY));
  
  	if (delay >= MAX_DELAY) {

  		pr_err("%s: %s eagain grant
  ", func, current->comm);

  		*status = GNTST_bad_page;
  	}
  }
  
  void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count)
  {
  	struct gnttab_map_grant_ref *op;
  
  	if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, batch, count))
  		BUG();
  	for (op = batch; op < batch + count; op++)
  		if (op->status == GNTST_eagain)
  			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, op,
  						&op->status, __func__);
  }
  EXPORT_SYMBOL_GPL(gnttab_batch_map);
  
  void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count)
  {
  	struct gnttab_copy *op;
  
  	if (HYPERVISOR_grant_table_op(GNTTABOP_copy, batch, count))
  		BUG();
  	for (op = batch; op < batch + count; op++)
  		if (op->status == GNTST_eagain)
  			gnttab_retry_eagain_gop(GNTTABOP_copy, op,
  						&op->status, __func__);
  }
  EXPORT_SYMBOL_GPL(gnttab_batch_copy);

  void gnttab_foreach_grant_in_range(struct page *page,
  				   unsigned int offset,
  				   unsigned int len,
  				   xen_grant_fn_t fn,
  				   void *data)
  {
  	unsigned int goffset;
  	unsigned int glen;
  	unsigned long xen_pfn;
  
  	len = min_t(unsigned int, PAGE_SIZE - offset, len);
  	goffset = xen_offset_in_page(offset);
  
  	xen_pfn = page_to_xen_pfn(page) + XEN_PFN_DOWN(offset);
  
  	while (len) {
  		glen = min_t(unsigned int, XEN_PAGE_SIZE - goffset, len);
  		fn(pfn_to_gfn(xen_pfn), goffset, glen, data);
  
  		goffset = 0;
  		xen_pfn++;
  		len -= glen;
  	}
  }
  EXPORT_SYMBOL_GPL(gnttab_foreach_grant_in_range);

  void gnttab_foreach_grant(struct page **pages,
  			  unsigned int nr_grefs,
  			  xen_grant_fn_t fn,
  			  void *data)
  {
  	unsigned int goffset = 0;
  	unsigned long xen_pfn = 0;
  	unsigned int i;
  
  	for (i = 0; i < nr_grefs; i++) {
  		if ((i % XEN_PFN_PER_PAGE) == 0) {
  			xen_pfn = page_to_xen_pfn(pages[i / XEN_PFN_PER_PAGE]);
  			goffset = 0;
  		}
  
  		fn(pfn_to_gfn(xen_pfn), goffset, XEN_PAGE_SIZE, data);
  
  		goffset += XEN_PAGE_SIZE;
  		xen_pfn++;
  	}
  }

  int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,

  		    struct gnttab_map_grant_ref *kmap_ops,

  		    struct page **pages, unsigned int count)

  {
  	int i, ret;

  
  	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);

  	if (ret)
  		return ret;

  	for (i = 0; i < count; i++) {
  		/* Retry eagain maps */

  		if (map_ops[i].status == GNTST_eagain)
  			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
  						&map_ops[i].status, __func__);

  		if (map_ops[i].status == GNTST_okay) {
  			struct xen_page_foreign *foreign;
  
  			SetPageForeign(pages[i]);
  			foreign = xen_page_foreign(pages[i]);
  			foreign->domid = map_ops[i].dom;
  			foreign->gref = map_ops[i].ref;
  		}
  	}

  	return set_foreign_p2m_mapping(map_ops, kmap_ops, pages, count);

  }
  EXPORT_SYMBOL_GPL(gnttab_map_refs);

  int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,

  		      struct gnttab_unmap_grant_ref *kunmap_ops,

  		      struct page **pages, unsigned int count)

  {

  	unsigned int i;

  	int ret;

  
  	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);

  	if (ret)
  		return ret;

  	for (i = 0; i < count; i++)
  		ClearPageForeign(pages[i]);

  	return clear_foreign_p2m_mapping(unmap_ops, kunmap_ops, pages, count);

  }
  EXPORT_SYMBOL_GPL(gnttab_unmap_refs);

  #define GNTTAB_UNMAP_REFS_DELAY 5
  
  static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item);
  
  static void gnttab_unmap_work(struct work_struct *work)
  {
  	struct gntab_unmap_queue_data
  		*unmap_data = container_of(work, 
  					   struct gntab_unmap_queue_data,
  					   gnttab_work.work);
  	if (unmap_data->age != UINT_MAX)
  		unmap_data->age++;
  	__gnttab_unmap_refs_async(unmap_data);
  }
  
  static void __gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
  {
  	int ret;
  	int pc;
  
  	for (pc = 0; pc < item->count; pc++) {
  		if (page_count(item->pages[pc]) > 1) {
  			unsigned long delay = GNTTAB_UNMAP_REFS_DELAY * (item->age + 1);
  			schedule_delayed_work(&item->gnttab_work,
  					      msecs_to_jiffies(delay));
  			return;
  		}
  	}
  
  	ret = gnttab_unmap_refs(item->unmap_ops, item->kunmap_ops,
  				item->pages, item->count);
  	item->done(ret, item);
  }
  
  void gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item)
  {
  	INIT_DELAYED_WORK(&item->gnttab_work, gnttab_unmap_work);
  	item->age = 0;
  
  	__gnttab_unmap_refs_async(item);
  }
  EXPORT_SYMBOL_GPL(gnttab_unmap_refs_async);

  static void unmap_refs_callback(int result,
  		struct gntab_unmap_queue_data *data)
  {
  	struct unmap_refs_callback_data *d = data->data;
  
  	d->result = result;
  	complete(&d->completion);
  }
  
  int gnttab_unmap_refs_sync(struct gntab_unmap_queue_data *item)
  {
  	struct unmap_refs_callback_data data;
  
  	init_completion(&data.completion);
  	item->data = &data;
  	item->done = &unmap_refs_callback;
  	gnttab_unmap_refs_async(item);
  	wait_for_completion(&data.completion);
  
  	return data.result;
  }
  EXPORT_SYMBOL_GPL(gnttab_unmap_refs_sync);

  static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)

  {
  	int rc;
  
  	rc = arch_gnttab_map_shared(frames, nr_gframes,
  				    gnttab_max_grant_frames(),
  				    &gnttab_shared.addr);
  	BUG_ON(rc);
  
  	return 0;
  }
  
  static void gnttab_unmap_frames_v1(void)
  {

  	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
  }

  static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
  {
  	struct gnttab_setup_table setup;

  	xen_pfn_t *frames;

  	unsigned int nr_gframes = end_idx + 1;
  	int rc;

  	if (xen_feature(XENFEAT_auto_translated_physmap)) {

  		struct xen_add_to_physmap xatp;
  		unsigned int i = end_idx;
  		rc = 0;

  		BUG_ON(xen_auto_xlat_grant_frames.count < nr_gframes);

  		/*
  		 * Loop backwards, so that the first hypercall has the largest
  		 * index, ensuring that the table will grow only once.
  		 */
  		do {
  			xatp.domid = DOMID_SELF;
  			xatp.idx = i;
  			xatp.space = XENMAPSPACE_grant_table;

  			xatp.gpfn = xen_auto_xlat_grant_frames.pfn[i];

  			rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
  			if (rc != 0) {

  				pr_warn("grant table add_to_physmap failed, err=%d
  ",
  					rc);

  				break;
  			}
  		} while (i-- > start_idx);
  
  		return rc;
  	}

  	/* No need for kzalloc as it is initialized in following hypercall
  	 * GNTTABOP_setup_table.
  	 */

  	frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC);
  	if (!frames)
  		return -ENOMEM;
  
  	setup.dom        = DOMID_SELF;
  	setup.nr_frames  = nr_gframes;

  	set_xen_guest_handle(setup.frame_list, frames);

  
  	rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
  	if (rc == -ENOSYS) {
  		kfree(frames);
  		return -ENOSYS;
  	}
  
  	BUG_ON(rc || setup.status);

  	rc = gnttab_interface->map_frames(frames, nr_gframes);

  
  	kfree(frames);

  	return rc;
  }

  static const struct gnttab_ops gnttab_v1_ops = {

  	.map_frames			= gnttab_map_frames_v1,
  	.unmap_frames			= gnttab_unmap_frames_v1,
  	.update_entry			= gnttab_update_entry_v1,
  	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v1,
  	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v1,
  	.query_foreign_access		= gnttab_query_foreign_access_v1,
  };
  
  static void gnttab_request_version(void)
  {

  	/* Only version 1 is used, which will always be available. */
  	grant_table_version = 1;

  	grefs_per_grant_frame = XEN_PAGE_SIZE / sizeof(struct grant_entry_v1);

  	gnttab_interface = &gnttab_v1_ops;

  	pr_info("Grant tables using version %d layout
  ", grant_table_version);

  }

  static int gnttab_setup(void)

  {

  	unsigned int max_nr_gframes;
  
  	max_nr_gframes = gnttab_max_grant_frames();
  	if (max_nr_gframes < nr_grant_frames)

  		return -ENOSYS;

  	if (xen_feature(XENFEAT_auto_translated_physmap) && gnttab_shared.addr == NULL) {

  		gnttab_shared.addr = xen_auto_xlat_grant_frames.vaddr;

  		if (gnttab_shared.addr == NULL) {

  			pr_warn("gnttab share frames (addr=0x%08lx) is not mapped!
  ",
  				(unsigned long)xen_auto_xlat_grant_frames.vaddr);

  			return -ENOMEM;
  		}
  	}

  	return gnttab_map(0, nr_grant_frames - 1);

  }

  int gnttab_resume(void)
  {
  	gnttab_request_version();
  	return gnttab_setup();
  }

  int gnttab_suspend(void)

  {

  	if (!xen_feature(XENFEAT_auto_translated_physmap))
  		gnttab_interface->unmap_frames();

  	return 0;
  }
  
  static int gnttab_expand(unsigned int req_entries)
  {
  	int rc;
  	unsigned int cur, extra;

  	BUG_ON(grefs_per_grant_frame == 0);

  	cur = nr_grant_frames;

  	extra = ((req_entries + (grefs_per_grant_frame-1)) /
  		 grefs_per_grant_frame);

  	if (cur + extra > gnttab_max_grant_frames()) {
  		pr_warn_ratelimited("xen/grant-table: max_grant_frames reached"
  				    " cur=%u extra=%u limit=%u"
  				    " gnttab_free_count=%u req_entries=%u
  ",
  				    cur, extra, gnttab_max_grant_frames(),
  				    gnttab_free_count, req_entries);

  		return -ENOSPC;

  	}

  
  	rc = gnttab_map(cur, cur + extra - 1);
  	if (rc == 0)
  		rc = grow_gnttab_list(extra);
  
  	return rc;
  }

  int gnttab_init(void)

  {
  	int i;

  	unsigned long max_nr_grant_frames;

  	unsigned int max_nr_glist_frames, nr_glist_frames;

  	unsigned int nr_init_grefs;

  	int ret;

  	gnttab_request_version();

  	max_nr_grant_frames = gnttab_max_grant_frames();

  	nr_grant_frames = 1;

  
  	/* Determine the maximum number of frames required for the
  	 * grant reference free list on the current hypervisor.
  	 */

  	BUG_ON(grefs_per_grant_frame == 0);

  	max_nr_glist_frames = (max_nr_grant_frames *

  			       grefs_per_grant_frame / RPP);

  
  	gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
  			      GFP_KERNEL);
  	if (gnttab_list == NULL)
  		return -ENOMEM;

  	nr_glist_frames = (nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;

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

  		gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);

  		if (gnttab_list[i] == NULL) {
  			ret = -ENOMEM;

  			goto ini_nomem;

  		}

  	}

  	ret = arch_gnttab_init(max_nr_grant_frames);

  	if (ret < 0)
  		goto ini_nomem;

  	if (gnttab_setup() < 0) {

  		ret = -ENODEV;
  		goto ini_nomem;
  	}

  	nr_init_grefs = nr_grant_frames * grefs_per_grant_frame;

  
  	for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
  		gnttab_entry(i) = i + 1;
  
  	gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
  	gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
  	gnttab_free_head  = NR_RESERVED_ENTRIES;
  
  	printk("Grant table initialized
  ");
  	return 0;
  
   ini_nomem:
  	for (i--; i >= 0; i--)
  		free_page((unsigned long)gnttab_list[i]);
  	kfree(gnttab_list);

  	return ret;

  }

  EXPORT_SYMBOL_GPL(gnttab_init);

  static int __gnttab_init(void)

  {

  	if (!xen_domain())
  		return -ENODEV;

  	/* Delay grant-table initialization in the PV on HVM case */

  	if (xen_hvm_domain() && !xen_pvh_domain())

  		return 0;

  	return gnttab_init();
  }

  /* Starts after core_initcall so that xen_pvh_gnttab_setup can be called
   * beforehand to initialize xen_auto_xlat_grant_frames. */
  core_initcall_sync(__gnttab_init);