Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1497 insertions, 0 deletions

diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
new file mode 100644
index 000000000..e434a583e
--- /dev/null
+++ b/drivers/xen/grant-table.c
@@ -0,0 +1,1497 @@
+/******************************************************************************
+ * 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/bootmem.h>
+#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 <linux/moduleparam.h>
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+#include <linux/dma-mapping.h>
+#endif
+
+#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>
+#ifdef CONFIG_X86
+#include <asm/xen/cpuid.h>
+#endif
+#include <xen/mem-reservation.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 unsigned int xen_gnttab_version;
+module_param_named(version, xen_gnttab_version, uint, 0);
+
+static union {
+	struct grant_entry_v1 *v1;
+	union grant_entry_v2 *v2;
+	void *addr;
+} gnttab_shared;
+
+/*This is a structure of function pointers for grant table*/
+struct gnttab_ops {
+	/*
+	 * Version of the grant interface.
+	 */
+	unsigned int version;
+	/*
+	 * Grant refs per grant frame.
+	 */
+	unsigned int grefs_per_grant_frame;
+	/*
+	 * 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);
+	/*
+	 * Read the frame number related to a given grant reference.
+	 */
+	unsigned long (*read_frame)(grant_ref_t ref);
+};
+
+struct unmap_refs_callback_data {
+	struct completion completion;
+	int result;
+};
+
+static const struct gnttab_ops *gnttab_interface;
+
+/* This reflects status of grant entries, so act as a global value. */
+static grant_status_t *grstatus;
+
+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))
+#define SPP (PAGE_SIZE / sizeof(grant_status_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 and gnttab_update_entry_v2.
+ * 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;
+}
+
+static void gnttab_update_entry_v2(grant_ref_t ref, domid_t domid,
+				   unsigned long frame, unsigned int flags)
+{
+	gnttab_shared.v2[ref].hdr.domid = domid;
+	gnttab_shared.v2[ref].full_page.frame = frame;
+	wmb();	/* Hypervisor concurrent accesses. */
+	gnttab_shared.v2[ref].hdr.flags = GTF_permit_access | 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_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 int gnttab_end_foreign_access_ref_v2(grant_ref_t ref, int readonly)
+{
+	gnttab_shared.v2[ref].hdr.flags = 0;
+	mb();	/* Concurrent access by hypervisor. */
+	if (grstatus[ref] & (GTF_reading|GTF_writing)) {
+		return 0;
+	} else {
+		/*
+		 * The read of grstatus needs to have acquire semantics.
+		 *  On x86, reads already have that, and we just need to
+		 * protect against compiler reorderings.
+		 * On other architectures we may need a full barrier.
+		 */
+#ifdef CONFIG_X86
+		barrier();
+#else
+		mb();
+#endif
+	}
+
+	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!\n", ref);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
+
+static unsigned long gnttab_read_frame_v1(grant_ref_t ref)
+{
+	return gnttab_shared.v1[ref].frame;
+}
+
+static unsigned long gnttab_read_frame_v2(grant_ref_t ref)
+{
+	return gnttab_shared.v2[ref].full_page.frame;
+}
+
+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(struct timer_list *);
+static DEFINE_TIMER(deferred_timer, gnttab_handle_deferred);
+
+static void gnttab_handle_deferred(struct timer_list *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);
+			pr_debug("freeing g.e. %#x (pfn %#lx)\n",
+				 entry->ref, page_to_pfn(entry->page));
+			put_page(entry->page);
+			kfree(entry);
+			entry = NULL;
+		} else {
+			if (!--entry->warn_delay)
+				pr_info("g.e. %#x still pending\n", 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;
+	gfp_t gfp = (in_atomic() || irqs_disabled()) ? GFP_ATOMIC : GFP_KERNEL;
+	const char *what = KERN_WARNING "leaking";
+
+	entry = kmalloc(sizeof(*entry), gfp);
+	if (!page) {
+		unsigned long gfn = gnttab_interface->read_frame(ref);
+
+		page = pfn_to_page(gfn_to_pfn(gfn));
+		get_page(page);
+	}
+
+	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)\n",
+	       what, ref, page ? page_to_pfn(page) : -1);
+}
+
+int gnttab_try_end_foreign_access(grant_ref_t ref)
+{
+	int ret = _gnttab_end_foreign_access_ref(ref, 0);
+
+	if (ret)
+		put_free_entry(ref);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_try_end_foreign_access);
+
+void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
+			       unsigned long page)
+{
+	if (gnttab_try_end_foreign_access(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;
+}
+
+static unsigned long gnttab_end_foreign_transfer_ref_v2(grant_ref_t ref)
+{
+	unsigned long frame;
+	u16           flags;
+	u16          *pflags;
+
+	pflags = &gnttab_shared.v2[ref].hdr.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.v2[ref].full_page.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 unsigned int gnttab_frames(unsigned int frames, unsigned int align)
+{
+	return (frames * gnttab_interface->grefs_per_grant_frame + align - 1) /
+	       align;
+}
+
+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;
+	unsigned int grefs_per_frame;
+
+	BUG_ON(gnttab_interface == NULL);
+	grefs_per_frame = gnttab_interface->grefs_per_grant_frame;
+
+	new_nr_grant_frames = nr_grant_frames + more_frames;
+	extra_entries = more_frames * grefs_per_frame;
+
+	nr_glist_frames = gnttab_frames(nr_grant_frames, RPP);
+	new_nr_glist_frames = gnttab_frames(new_nr_grant_frames, 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_frame * nr_grant_frames;
+	     i < grefs_per_frame * new_nr_grant_frames - 1; i++)
+		gnttab_entry(i) = i + 1;
+
+	gnttab_entry(i) = gnttab_free_head;
+	gnttab_free_head = grefs_per_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)!\n",
+			&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);
+
+int gnttab_pages_set_private(int nr_pages, struct page **pages)
+{
+	int i;
+
+	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)
+			return -ENOMEM;
+
+		set_page_private(pages[i], (unsigned long)foreign);
+#endif
+		SetPagePrivate(pages[i]);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnttab_pages_set_private);
+
+/**
+ * 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 ret;
+
+	ret = alloc_xenballooned_pages(nr_pages, pages);
+	if (ret < 0)
+		return ret;
+
+	ret = gnttab_pages_set_private(nr_pages, pages);
+	if (ret < 0)
+		gnttab_free_pages(nr_pages, pages);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_alloc_pages);
+
+void gnttab_pages_clear_private(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]);
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(gnttab_pages_clear_private);
+
+/**
+ * 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)
+{
+	gnttab_pages_clear_private(nr_pages, pages);
+	free_xenballooned_pages(nr_pages, pages);
+}
+EXPORT_SYMBOL_GPL(gnttab_free_pages);
+
+#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
+/**
+ * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
+ * @args: arguments to the function
+ */
+int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
+{
+	unsigned long pfn, start_pfn;
+	size_t size;
+	int i, ret;
+
+	size = args->nr_pages << PAGE_SHIFT;
+	if (args->coherent)
+		args->vaddr = dma_alloc_coherent(args->dev, size,
+						 &args->dev_bus_addr,
+						 GFP_KERNEL | __GFP_NOWARN);
+	else
+		args->vaddr = dma_alloc_wc(args->dev, size,
+					   &args->dev_bus_addr,
+					   GFP_KERNEL | __GFP_NOWARN);
+	if (!args->vaddr) {
+		pr_debug("Failed to allocate DMA buffer of size %zu\n", size);
+		return -ENOMEM;
+	}
+
+	start_pfn = __phys_to_pfn(args->dev_bus_addr);
+	for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
+			pfn++, i++) {
+		struct page *page = pfn_to_page(pfn);
+
+		args->pages[i] = page;
+		args->frames[i] = xen_page_to_gfn(page);
+		xenmem_reservation_scrub_page(page);
+	}
+
+	xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);
+
+	ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
+	if (ret != args->nr_pages) {
+		pr_debug("Failed to decrease reservation for DMA buffer\n");
+		ret = -EFAULT;
+		goto fail;
+	}
+
+	ret = gnttab_pages_set_private(args->nr_pages, args->pages);
+	if (ret < 0)
+		goto fail;
+
+	return 0;
+
+fail:
+	gnttab_dma_free_pages(args);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);
+
+/**
+ * gnttab_dma_free_pages - free DMAable pages
+ * @args: arguments to the function
+ */
+int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
+{
+	size_t size;
+	int i, ret;
+
+	gnttab_pages_clear_private(args->nr_pages, args->pages);
+
+	for (i = 0; i < args->nr_pages; i++)
+		args->frames[i] = page_to_xen_pfn(args->pages[i]);
+
+	ret = xenmem_reservation_increase(args->nr_pages, args->frames);
+	if (ret != args->nr_pages) {
+		pr_debug("Failed to increase reservation for DMA buffer\n");
+		ret = -EFAULT;
+	} else {
+		ret = 0;
+	}
+
+	xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
+					     args->frames);
+
+	size = args->nr_pages << PAGE_SHIFT;
+	if (args->coherent)
+		dma_free_coherent(args->dev, size,
+				  args->vaddr, args->dev_bus_addr);
+	else
+		dma_free_wc(args->dev, size,
+			    args->vaddr, args->dev_bus_addr);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
+#endif
+
+/* 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\n", 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++) {
+		switch (map_ops[i].status) {
+		case 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;
+			break;
+		}
+
+		case GNTST_no_device_space:
+			pr_warn_ratelimited("maptrack limit reached, can't map all guest pages\n");
+			break;
+
+		case GNTST_eagain:
+			/* Retry eagain maps */
+			gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref,
+						map_ops + i,
+						&map_ops[i].status, __func__);
+			/* Test status in next loop iteration. */
+			i--;
+			break;
+
+		default:
+			break;
+		}
+	}
+
+	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 unsigned int nr_status_frames(unsigned int nr_grant_frames)
+{
+	BUG_ON(gnttab_interface == NULL);
+	return gnttab_frames(nr_grant_frames, SPP);
+}
+
+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_frames_v2(xen_pfn_t *frames, unsigned int nr_gframes)
+{
+	uint64_t *sframes;
+	unsigned int nr_sframes;
+	struct gnttab_get_status_frames getframes;
+	int rc;
+
+	nr_sframes = nr_status_frames(nr_gframes);
+
+	/* No need for kzalloc as it is initialized in following hypercall
+	 * GNTTABOP_get_status_frames.
+	 */
+	sframes = kmalloc_array(nr_sframes, sizeof(uint64_t), GFP_ATOMIC);
+	if (!sframes)
+		return -ENOMEM;
+
+	getframes.dom        = DOMID_SELF;
+	getframes.nr_frames  = nr_sframes;
+	set_xen_guest_handle(getframes.frame_list, sframes);
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
+				       &getframes, 1);
+	if (rc == -ENOSYS) {
+		kfree(sframes);
+		return -ENOSYS;
+	}
+
+	BUG_ON(rc || getframes.status);
+
+	rc = arch_gnttab_map_status(sframes, nr_sframes,
+				    nr_status_frames(gnttab_max_grant_frames()),
+				    &grstatus);
+	BUG_ON(rc);
+	kfree(sframes);
+
+	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_v2(void)
+{
+	arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
+	arch_gnttab_unmap(grstatus, nr_status_frames(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\n",
+					rc);
+				break;
+			}
+		} while (i-- > start_idx);
+
+		return rc;
+	}
+
+	/* No need for kzalloc as it is initialized in following hypercall
+	 * GNTTABOP_setup_table.
+	 */
+	frames = kmalloc_array(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 = {
+	.version			= 1,
+	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
+					  sizeof(struct grant_entry_v1),
+	.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,
+	.read_frame			= gnttab_read_frame_v1,
+};
+
+static const struct gnttab_ops gnttab_v2_ops = {
+	.version			= 2,
+	.grefs_per_grant_frame		= XEN_PAGE_SIZE /
+					  sizeof(union grant_entry_v2),
+	.map_frames			= gnttab_map_frames_v2,
+	.unmap_frames			= gnttab_unmap_frames_v2,
+	.update_entry			= gnttab_update_entry_v2,
+	.end_foreign_access_ref		= gnttab_end_foreign_access_ref_v2,
+	.end_foreign_transfer_ref	= gnttab_end_foreign_transfer_ref_v2,
+	.read_frame			= gnttab_read_frame_v2,
+};
+
+static bool gnttab_need_v2(void)
+{
+#ifdef CONFIG_X86
+	uint32_t base, width;
+
+	if (xen_pv_domain()) {
+		base = xen_cpuid_base();
+		if (cpuid_eax(base) < 5)
+			return false;	/* Information not available, use V1. */
+		width = cpuid_ebx(base + 5) &
+			XEN_CPUID_MACHINE_ADDRESS_WIDTH_MASK;
+		return width > 32 + PAGE_SHIFT;
+	}
+#endif
+	return !!(max_possible_pfn >> 32);
+}
+
+static void gnttab_request_version(void)
+{
+	long rc;
+	struct gnttab_set_version gsv;
+
+	if (gnttab_need_v2())
+		gsv.version = 2;
+	else
+		gsv.version = 1;
+
+	/* Boot parameter overrides automatic selection. */
+	if (xen_gnttab_version >= 1 && xen_gnttab_version <= 2)
+		gsv.version = xen_gnttab_version;
+
+	rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
+	if (rc == 0 && gsv.version == 2)
+		gnttab_interface = &gnttab_v2_ops;
+	else
+		gnttab_interface = &gnttab_v1_ops;
+	pr_info("Grant tables using version %d layout\n",
+		gnttab_interface->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!\n",
+				(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(gnttab_interface == NULL);
+	cur = nr_grant_frames;
+	extra = ((req_entries + gnttab_interface->grefs_per_grant_frame - 1) /
+		 gnttab_interface->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\n",
+				    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(gnttab_interface == NULL);
+	max_nr_glist_frames = (max_nr_grant_frames *
+			       gnttab_interface->grefs_per_grant_frame / RPP);
+
+	gnttab_list = kmalloc_array(max_nr_glist_frames,
+				    sizeof(grant_ref_t *),
+				    GFP_KERNEL);
+	if (gnttab_list == NULL)
+		return -ENOMEM;
+
+	nr_glist_frames = gnttab_frames(nr_grant_frames, 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,
+			       nr_status_frames(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 *
+			gnttab_interface->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\n");
+	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);