include/xen/grant_table.h - linux - Git at Google

 /******************************************************************************
  * grant_table.h
  *
  * Two sets of functionality:
  * 1. Granting foreign access to our memory reservation.
  * 2. Accessing others' memory reservations via grant references.
  * (i.e., mechanisms for both sender and recipient of grant references)
  *
  * Copyright (c) 2004-2005, K A Fraser
  * Copyright (c) 2005, Christopher Clark
  *
  * 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.
  */

 #ifndef __ASM_GNTTAB_H__
 #define __ASM_GNTTAB_H__

 #include <asm/page.h>

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

 #include <asm/xen/hypervisor.h>

 #include <xen/features.h>
 #include <xen/page.h>
 #include <linux/mm_types.h>
 #include <linux/page-flags.h>
 #include <linux/kernel.h>

 /*
  * Technically there's no reliably invalid grant reference or grant handle,
  * so pick the value that is the most unlikely one to be observed valid.
  */
 #define INVALID_GRANT_REF          ((grant_ref_t)-1)
 #define INVALID_GRANT_HANDLE       ((grant_handle_t)-1)

 /* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */
 #define NR_GRANT_FRAMES 4

 struct gnttab_free_callback {
 	struct gnttab_free_callback *next;
 	void (*fn)(void *);
 	void *arg;
 	u16 count;
 };

 struct gntab_unmap_queue_data;

 typedef void (*gnttab_unmap_refs_done)(int result, struct gntab_unmap_queue_data *data);

 struct gntab_unmap_queue_data
 {
 	struct delayed_work	gnttab_work;
 	void *data;
 	gnttab_unmap_refs_done	done;
 	struct gnttab_unmap_grant_ref *unmap_ops;
 	struct gnttab_unmap_grant_ref *kunmap_ops;
 	struct page **pages;
 	unsigned int count;
 	unsigned int age;
 };

 int gnttab_init(void);
 int gnttab_suspend(void);
 int gnttab_resume(void);

 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 				int readonly);

 /*
  * End access through the given grant reference, iff the grant entry is no
  * longer in use.  Return 1 if the grant entry was freed, 0 if it is still in
  * use.
  */
 int gnttab_end_foreign_access_ref(grant_ref_t ref);

 /*
  * Eventually end access through the given grant reference, and once that
  * access has been ended, free the given page too.  Access will be ended
  * immediately iff the grant entry is not in use, otherwise it will happen
  * some time later.  page may be NULL, in which case no freeing will occur.
  * Note that the granted page might still be accessed (read or write) by the
  * other side after gnttab_end_foreign_access() returns, so even if page was
  * specified as NULL it is not allowed to just reuse the page for other
  * purposes immediately. gnttab_end_foreign_access() will take an additional
  * reference to the granted page in this case, which is dropped only after
  * the grant is no longer in use.
  * This requires that multi page allocations for areas subject to
  * gnttab_end_foreign_access() are done via alloc_pages_exact() (and freeing
  * via free_pages_exact()) in order to avoid high order pages.
  */
 void gnttab_end_foreign_access(grant_ref_t ref, struct page *page);

 /*
  * End access through the given grant reference, iff the grant entry is
  * no longer in use.  In case of success ending foreign access, the
  * grant reference is deallocated.
  * Return 1 if the grant entry was freed, 0 if it is still in use.
  */
 int gnttab_try_end_foreign_access(grant_ref_t ref);

 /*
  * operations on reserved batches of grant references
  */
 int gnttab_alloc_grant_references(u16 count, grant_ref_t *pprivate_head);

 int gnttab_alloc_grant_reference_seq(unsigned int count, grant_ref_t *first);

 void gnttab_free_grant_reference(grant_ref_t ref);

 void gnttab_free_grant_references(grant_ref_t head);

 void gnttab_free_grant_reference_seq(grant_ref_t head, unsigned int count);

 int gnttab_empty_grant_references(const grant_ref_t *pprivate_head);

 int gnttab_claim_grant_reference(grant_ref_t *pprivate_head);

 void gnttab_release_grant_reference(grant_ref_t *private_head,
 				    grant_ref_t release);

 void gnttab_request_free_callback(struct gnttab_free_callback *callback,
 				  void (*fn)(void *), void *arg, u16 count);
 void gnttab_cancel_free_callback(struct gnttab_free_callback *callback);

 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
 				     unsigned long frame, int readonly);

 /* Give access to the first 4K of the page */
 static inline void gnttab_page_grant_foreign_access_ref_one(
 	grant_ref_t ref, domid_t domid,
 	struct page *page, int readonly)
 {
 	gnttab_grant_foreign_access_ref(ref, domid, xen_page_to_gfn(page),
 					readonly);
 }

 static inline void
 gnttab_set_map_op(struct gnttab_map_grant_ref *map, phys_addr_t addr,
 		  uint32_t flags, grant_ref_t ref, domid_t domid)
 {
 	if (flags & GNTMAP_contains_pte)
 		map->host_addr = addr;
 	else if (xen_feature(XENFEAT_auto_translated_physmap))
 		map->host_addr = __pa(addr);
 	else
 		map->host_addr = addr;

 	map->flags = flags;
 	map->ref = ref;
 	map->dom = domid;
 	map->status = 1; /* arbitrary positive value */
 }

 static inline void
 gnttab_set_unmap_op(struct gnttab_unmap_grant_ref *unmap, phys_addr_t addr,
 		    uint32_t flags, grant_handle_t handle)
 {
 	if (flags & GNTMAP_contains_pte)
 		unmap->host_addr = addr;
 	else if (xen_feature(XENFEAT_auto_translated_physmap))
 		unmap->host_addr = __pa(addr);
 	else
 		unmap->host_addr = addr;

 	unmap->handle = handle;
 	unmap->dev_bus_addr = 0;
 }

 int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status);
 int arch_gnttab_map_shared(xen_pfn_t *frames, unsigned long nr_gframes,
 			   unsigned long max_nr_gframes,
 			   void **__shared);
 int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
 			   unsigned long max_nr_gframes,
 			   grant_status_t **__shared);
 void arch_gnttab_unmap(void *shared, unsigned long nr_gframes);

 struct grant_frames {
 	xen_pfn_t *pfn;
 	unsigned int count;
 	void *vaddr;
 };
 extern struct grant_frames xen_auto_xlat_grant_frames;
 unsigned int gnttab_max_grant_frames(void);
 int gnttab_setup_auto_xlat_frames(phys_addr_t addr);
 void gnttab_free_auto_xlat_frames(void);

 #define gnttab_map_vaddr(map) ((void *)(map.host_virt_addr))

 int gnttab_alloc_pages(int nr_pages, struct page **pages);
 void gnttab_free_pages(int nr_pages, struct page **pages);

 struct gnttab_page_cache {
 	spinlock_t		lock;
 #ifdef CONFIG_XEN_UNPOPULATED_ALLOC
 	struct page		*pages;
 #else
 	struct list_head	pages;
 #endif
 	unsigned int		num_pages;
 };

 void gnttab_page_cache_init(struct gnttab_page_cache *cache);
 int gnttab_page_cache_get(struct gnttab_page_cache *cache, struct page **page);
 void gnttab_page_cache_put(struct gnttab_page_cache *cache, struct page **page,
 			   unsigned int num);
 void gnttab_page_cache_shrink(struct gnttab_page_cache *cache,
 			      unsigned int num);

 #ifdef CONFIG_XEN_GRANT_DMA_ALLOC
 struct gnttab_dma_alloc_args {
 	/* Device for which DMA memory will be/was allocated. */
 	struct device *dev;
 	/* If set then DMA buffer is coherent and write-combine otherwise. */
 	bool coherent;

 	int nr_pages;
 	struct page **pages;
 	xen_pfn_t *frames;
 	void *vaddr;
 	dma_addr_t dev_bus_addr;
 };

 int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args);
 int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args);
 #endif

 int gnttab_pages_set_private(int nr_pages, struct page **pages);
 void gnttab_pages_clear_private(int nr_pages, struct page **pages);

 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 gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
 		      struct gnttab_unmap_grant_ref *kunmap_ops,
 		      struct page **pages, unsigned int count);
 void gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item);
 int gnttab_unmap_refs_sync(struct gntab_unmap_queue_data *item);


 /* Perform a batch of grant map/copy operations. Retry every batch slot
  * for which the hypervisor returns GNTST_eagain. This is typically due
  * to paged out target frames.
  *
  * Will retry for 1, 2, ... 255 ms, i.e. 256 times during 32 seconds.
  *
  * Return value in each iand every status field of the batch guaranteed
  * to not be GNTST_eagain.
  */
 void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count);
 void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count);


 struct xen_page_foreign {
 	domid_t domid;
 	grant_ref_t gref;
 };

 static inline struct xen_page_foreign *xen_page_foreign(struct page *page)
 {
 	if (!PageForeign(page))
 		return NULL;
 #if BITS_PER_LONG < 64
 	return (struct xen_page_foreign *)page->private;
 #else
 	BUILD_BUG_ON(sizeof(struct xen_page_foreign) > BITS_PER_LONG);
 	return (struct xen_page_foreign *)&page->private;
 #endif
 }

 /* Split Linux page in chunk of the size of the grant and call fn
  *
  * Parameters of fn:
  *	gfn: guest frame number
  *	offset: offset in the grant
  *	len: length of the data in the grant.
  *	data: internal information
  */
 typedef void (*xen_grant_fn_t)(unsigned long gfn, unsigned int offset,
 			       unsigned int len, void *data);

 void gnttab_foreach_grant_in_range(struct page *page,
 				   unsigned int offset,
 				   unsigned int len,
 				   xen_grant_fn_t fn,
 				   void *data);

 /* Helper to get to call fn only on the first "grant chunk" */
 static inline void gnttab_for_one_grant(struct page *page, unsigned int offset,
 					unsigned len, xen_grant_fn_t fn,
 					void *data)
 {
 	/* The first request is limited to the size of one grant */
 	len = min_t(unsigned int, XEN_PAGE_SIZE - (offset & ~XEN_PAGE_MASK),
 		    len);

 	gnttab_foreach_grant_in_range(page, offset, len, fn, data);
 }

 /* Get @nr_grefs grants from an array of page and call fn for each grant */
 void gnttab_foreach_grant(struct page **pages,
 			  unsigned int nr_grefs,
 			  xen_grant_fn_t fn,
 			  void *data);

 /* Get the number of grant in a specified region
  *
  * start: Offset from the beginning of the first page
  * len: total length of data (can cross multiple page)
  */
 static inline unsigned int gnttab_count_grant(unsigned int start,
 					      unsigned int len)
 {
 	return XEN_PFN_UP(xen_offset_in_page(start) + len);
 }

 #endif /* __ASM_GNTTAB_H__ */
	/******************************************************************************
	* grant_table.h
	*
	* Two sets of functionality:
	* 1. Granting foreign access to our memory reservation.
	* 2. Accessing others' memory reservations via grant references.
	* (i.e., mechanisms for both sender and recipient of grant references)
	*
	* Copyright (c) 2004-2005, K A Fraser
	* Copyright (c) 2005, Christopher Clark
	*
	* 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.
	*/

	#ifndef __ASM_GNTTAB_H__
	#define __ASM_GNTTAB_H__

	#include <asm/page.h>

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

	#include <asm/xen/hypervisor.h>

	#include <xen/features.h>
	#include <xen/page.h>
	#include <linux/mm_types.h>
	#include <linux/page-flags.h>
	#include <linux/kernel.h>

	/*
	* Technically there's no reliably invalid grant reference or grant handle,
	* so pick the value that is the most unlikely one to be observed valid.
	*/
	#define INVALID_GRANT_REF ((grant_ref_t)-1)
	#define INVALID_GRANT_HANDLE ((grant_handle_t)-1)

	/* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */
	#define NR_GRANT_FRAMES 4

	struct gnttab_free_callback {
	struct gnttab_free_callback *next;
	void (fn)(void );
	void *arg;
	u16 count;
	};

	struct gntab_unmap_queue_data;

	typedef void (gnttab_unmap_refs_done)(int result, struct gntab_unmap_queue_data data);

	struct gntab_unmap_queue_data
	{
	struct delayed_work gnttab_work;
	void *data;
	gnttab_unmap_refs_done done;
	struct gnttab_unmap_grant_ref *unmap_ops;
	struct gnttab_unmap_grant_ref *kunmap_ops;
	struct page **pages;
	unsigned int count;
	unsigned int age;
	};

	int gnttab_init(void);
	int gnttab_suspend(void);
	int gnttab_resume(void);

	int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
	int readonly);

	/*
	* End access through the given grant reference, iff the grant entry is no
	* longer in use. Return 1 if the grant entry was freed, 0 if it is still in
	* use.
	*/
	int gnttab_end_foreign_access_ref(grant_ref_t ref);

	/*
	* Eventually end access through the given grant reference, and once that
	* access has been ended, free the given page too. Access will be ended
	* immediately iff the grant entry is not in use, otherwise it will happen
	* some time later. page may be NULL, in which case no freeing will occur.
	* Note that the granted page might still be accessed (read or write) by the
	* other side after gnttab_end_foreign_access() returns, so even if page was
	* specified as NULL it is not allowed to just reuse the page for other
	* purposes immediately. gnttab_end_foreign_access() will take an additional
	* reference to the granted page in this case, which is dropped only after
	* the grant is no longer in use.
	* This requires that multi page allocations for areas subject to
	* gnttab_end_foreign_access() are done via alloc_pages_exact() (and freeing
	* via free_pages_exact()) in order to avoid high order pages.
	*/
	void gnttab_end_foreign_access(grant_ref_t ref, struct page *page);

	/*
	* End access through the given grant reference, iff the grant entry is
	* no longer in use. In case of success ending foreign access, the
	* grant reference is deallocated.
	* Return 1 if the grant entry was freed, 0 if it is still in use.
	*/
	int gnttab_try_end_foreign_access(grant_ref_t ref);

	/*
	* operations on reserved batches of grant references
	*/
	int gnttab_alloc_grant_references(u16 count, grant_ref_t *pprivate_head);

	int gnttab_alloc_grant_reference_seq(unsigned int count, grant_ref_t *first);

	void gnttab_free_grant_reference(grant_ref_t ref);

	void gnttab_free_grant_references(grant_ref_t head);

	void gnttab_free_grant_reference_seq(grant_ref_t head, unsigned int count);

	int gnttab_empty_grant_references(const grant_ref_t *pprivate_head);

	int gnttab_claim_grant_reference(grant_ref_t *pprivate_head);

	void gnttab_release_grant_reference(grant_ref_t *private_head,
	grant_ref_t release);

	void gnttab_request_free_callback(struct gnttab_free_callback *callback,
	void (fn)(void ), void *arg, u16 count);
	void gnttab_cancel_free_callback(struct gnttab_free_callback *callback);

	void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
	unsigned long frame, int readonly);

	/* Give access to the first 4K of the page */
	static inline void gnttab_page_grant_foreign_access_ref_one(
	grant_ref_t ref, domid_t domid,
	struct page *page, int readonly)
	{
	gnttab_grant_foreign_access_ref(ref, domid, xen_page_to_gfn(page),
	readonly);
	}

	static inline void
	gnttab_set_map_op(struct gnttab_map_grant_ref *map, phys_addr_t addr,
	uint32_t flags, grant_ref_t ref, domid_t domid)
	{
	if (flags & GNTMAP_contains_pte)
	map->host_addr = addr;
	else if (xen_feature(XENFEAT_auto_translated_physmap))
	map->host_addr = __pa(addr);
	else
	map->host_addr = addr;

	map->flags = flags;
	map->ref = ref;
	map->dom = domid;
	map->status = 1; /* arbitrary positive value */
	}

	static inline void
	gnttab_set_unmap_op(struct gnttab_unmap_grant_ref *unmap, phys_addr_t addr,
	uint32_t flags, grant_handle_t handle)
	{
	if (flags & GNTMAP_contains_pte)
	unmap->host_addr = addr;
	else if (xen_feature(XENFEAT_auto_translated_physmap))
	unmap->host_addr = __pa(addr);
	else
	unmap->host_addr = addr;

	unmap->handle = handle;
	unmap->dev_bus_addr = 0;
	}

	int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status);
	int arch_gnttab_map_shared(xen_pfn_t *frames, unsigned long nr_gframes,
	unsigned long max_nr_gframes,
	void **__shared);
	int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
	unsigned long max_nr_gframes,
	grant_status_t **__shared);
	void arch_gnttab_unmap(void *shared, unsigned long nr_gframes);

	struct grant_frames {
	xen_pfn_t *pfn;
	unsigned int count;
	void *vaddr;
	};
	extern struct grant_frames xen_auto_xlat_grant_frames;
	unsigned int gnttab_max_grant_frames(void);
	int gnttab_setup_auto_xlat_frames(phys_addr_t addr);
	void gnttab_free_auto_xlat_frames(void);

	#define gnttab_map_vaddr(map) ((void *)(map.host_virt_addr))

	int gnttab_alloc_pages(int nr_pages, struct page **pages);
	void gnttab_free_pages(int nr_pages, struct page **pages);

	struct gnttab_page_cache {
	spinlock_t lock;
	#ifdef CONFIG_XEN_UNPOPULATED_ALLOC
	struct page *pages;
	#else
	struct list_head pages;
	#endif
	unsigned int num_pages;
	};

	void gnttab_page_cache_init(struct gnttab_page_cache *cache);
	int gnttab_page_cache_get(struct gnttab_page_cache cache, struct page *page);
	void gnttab_page_cache_put(struct gnttab_page_cache cache, struct page *page,
	unsigned int num);
	void gnttab_page_cache_shrink(struct gnttab_page_cache *cache,
	unsigned int num);

	#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
	struct gnttab_dma_alloc_args {
	/* Device for which DMA memory will be/was allocated. */
	struct device *dev;
	/* If set then DMA buffer is coherent and write-combine otherwise. */
	bool coherent;

	int nr_pages;
	struct page **pages;
	xen_pfn_t *frames;
	void *vaddr;
	dma_addr_t dev_bus_addr;
	};

	int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args);
	int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args);
	#endif

	int gnttab_pages_set_private(int nr_pages, struct page **pages);
	void gnttab_pages_clear_private(int nr_pages, struct page **pages);

	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 gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
	struct gnttab_unmap_grant_ref *kunmap_ops,
	struct page **pages, unsigned int count);
	void gnttab_unmap_refs_async(struct gntab_unmap_queue_data* item);
	int gnttab_unmap_refs_sync(struct gntab_unmap_queue_data *item);


	/* Perform a batch of grant map/copy operations. Retry every batch slot
	* for which the hypervisor returns GNTST_eagain. This is typically due
	* to paged out target frames.
	*
	* Will retry for 1, 2, ... 255 ms, i.e. 256 times during 32 seconds.
	*
	* Return value in each iand every status field of the batch guaranteed
	* to not be GNTST_eagain.
	*/
	void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count);
	void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count);


	struct xen_page_foreign {
	domid_t domid;
	grant_ref_t gref;
	};

	static inline struct xen_page_foreign xen_page_foreign(struct page page)
	{
	if (!PageForeign(page))
	return NULL;
	#if BITS_PER_LONG < 64
	return (struct xen_page_foreign *)page->private;
	#else
	BUILD_BUG_ON(sizeof(struct xen_page_foreign) > BITS_PER_LONG);
	return (struct xen_page_foreign *)&page->private;
	#endif
	}

	/* Split Linux page in chunk of the size of the grant and call fn
	*
	* Parameters of fn:
	* gfn: guest frame number
	* offset: offset in the grant
	* len: length of the data in the grant.
	* data: internal information
	*/
	typedef void (*xen_grant_fn_t)(unsigned long gfn, unsigned int offset,
	unsigned int len, void *data);

	void gnttab_foreach_grant_in_range(struct page *page,
	unsigned int offset,
	unsigned int len,
	xen_grant_fn_t fn,
	void *data);

	/* Helper to get to call fn only on the first "grant chunk" */
	static inline void gnttab_for_one_grant(struct page *page, unsigned int offset,
	unsigned len, xen_grant_fn_t fn,
	void *data)
	{
	/* The first request is limited to the size of one grant */
	len = min_t(unsigned int, XEN_PAGE_SIZE - (offset & ~XEN_PAGE_MASK),
	len);

	gnttab_foreach_grant_in_range(page, offset, len, fn, data);
	}

	/* Get @nr_grefs grants from an array of page and call fn for each grant */
	void gnttab_foreach_grant(struct page **pages,
	unsigned int nr_grefs,
	xen_grant_fn_t fn,
	void *data);

	/* Get the number of grant in a specified region
	*
	* start: Offset from the beginning of the first page
	* len: total length of data (can cross multiple page)
	*/
	static inline unsigned int gnttab_count_grant(unsigned int start,
	unsigned int len)
	{
	return XEN_PFN_UP(xen_offset_in_page(start) + len);
	}

	#endif /* __ASM_GNTTAB_H__ */