OSCL-LXR linux-6.0.1/​drivers/​xen/​grant-table.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /******************************************************************************
  * 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/bitmap.h>
 #include <linux/memblock.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/sync_bitops.h>
 
 #define GNTTAB_LIST_END 0xffffffff
 
 static grant_ref_t **gnttab_list;
 static unsigned int nr_grant_frames;
 
 /*
  * Handling of free grants:
  *
  * Free grants are in a simple list anchored in gnttab_free_head. They are
  * linked by grant ref, the last element contains GNTTAB_LIST_END. The number
  * of free entries is stored in gnttab_free_count.
  * Additionally there is a bitmap of free entries anchored in
  * gnttab_free_bitmap. This is being used for simplifying allocation of
  * multiple consecutive grants, which is needed e.g. for support of virtio.
  * gnttab_last_free is used to add free entries of new frames at the end of
  * the free list.
  * gnttab_free_tail_ptr specifies the variable which references the start
  * of consecutive free grants ending with gnttab_last_free. This pointer is
  * updated in a rather defensive way, in order to avoid performance hits in
  * hot paths.
  * All those variables are protected by gnttab_list_lock.
  */
 static int gnttab_free_count;
 static unsigned int gnttab_size;
 static grant_ref_t gnttab_free_head = GNTTAB_LIST_END;
 static grant_ref_t gnttab_last_free = GNTTAB_LIST_END;
 static grant_ref_t *gnttab_free_tail_ptr;
 static unsigned long *gnttab_free_bitmap;
 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. 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.
      * 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);
     /*
      * 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--) {
         bitmap_clear(gnttab_free_bitmap, head, 1);
         if (gnttab_free_tail_ptr == __gnttab_entry(head))
             gnttab_free_tail_ptr = &gnttab_free_head;
         if (count)
             head = gnttab_entry(head);
     }
     gnttab_free_head = gnttab_entry(head);
     gnttab_entry(head) = GNTTAB_LIST_END;
 
     if (!gnttab_free_count) {
         gnttab_last_free = GNTTAB_LIST_END;
         gnttab_free_tail_ptr = NULL;
     }
 
     spin_unlock_irqrestore(&gnttab_list_lock, flags);
 
     return ref;
 }
 
 static int get_seq_entry_count(void)
 {
     if (gnttab_last_free == GNTTAB_LIST_END || !gnttab_free_tail_ptr ||
         *gnttab_free_tail_ptr == GNTTAB_LIST_END)
         return 0;
 
     return gnttab_last_free - *gnttab_free_tail_ptr + 1;
 }
 
 /* Rebuilds the free grant list and tries to find count consecutive entries. */
 static int get_free_seq(unsigned int count)
 {
     int ret = -ENOSPC;
     unsigned int from, to;
     grant_ref_t *last;
 
     gnttab_free_tail_ptr = &gnttab_free_head;
     last = &gnttab_free_head;
 
     for (from = find_first_bit(gnttab_free_bitmap, gnttab_size);
          from < gnttab_size;
          from = find_next_bit(gnttab_free_bitmap, gnttab_size, to + 1)) {
         to = find_next_zero_bit(gnttab_free_bitmap, gnttab_size,
                     from + 1);
         if (ret < 0 && to - from >= count) {
             ret = from;
             bitmap_clear(gnttab_free_bitmap, ret, count);
             from += count;
             gnttab_free_count -= count;
             if (from == to)
                 continue;
         }
 
         /*
          * Recreate the free list in order to have it properly sorted.
          * This is needed to make sure that the free tail has the maximum
          * possible size.
          */
         while (from < to) {
             *last = from;
             last = __gnttab_entry(from);
             gnttab_last_free = from;
             from++;
         }
         if (to < gnttab_size)
             gnttab_free_tail_ptr = __gnttab_entry(to - 1);
     }
 
     *last = GNTTAB_LIST_END;
     if (gnttab_last_free != gnttab_size - 1)
         gnttab_free_tail_ptr = NULL;
 
     return ret;
 }
 
 static int get_free_entries_seq(unsigned int count)
 {
     unsigned long flags;
     int ret = 0;
 
     spin_lock_irqsave(&gnttab_list_lock, flags);
 
     if (gnttab_free_count < count) {
         ret = gnttab_expand(count - gnttab_free_count);
         if (ret < 0)
             goto out;
     }
 
     if (get_seq_entry_count() < count) {
         ret = get_free_seq(count);
         if (ret >= 0)
             goto out;
         ret = gnttab_expand(count - get_seq_entry_count());
         if (ret < 0)
             goto out;
     }
 
     ret = *gnttab_free_tail_ptr;
     *gnttab_free_tail_ptr = gnttab_entry(ret + count - 1);
     gnttab_free_count -= count;
     if (!gnttab_free_count)
         gnttab_free_tail_ptr = NULL;
     bitmap_clear(gnttab_free_bitmap, ret, count);
 
  out:
     spin_unlock_irqrestore(&gnttab_list_lock, flags);
 
     return ret;
 }
 
 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_locked(grant_ref_t ref)
 {
     if (unlikely(ref < GNTTAB_NR_RESERVED_ENTRIES))
         return;
 
     gnttab_entry(ref) = gnttab_free_head;
     gnttab_free_head = ref;
     if (!gnttab_free_count)
         gnttab_last_free = ref;
     if (gnttab_free_tail_ptr == &gnttab_free_head)
         gnttab_free_tail_ptr = __gnttab_entry(ref);
     gnttab_free_count++;
     bitmap_set(gnttab_free_bitmap, ref, 1);
 }
 
 static void put_free_entry(grant_ref_t ref)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&gnttab_list_lock, flags);
     put_free_entry_locked(ref);
     check_free_callbacks();
     spin_unlock_irqrestore(&gnttab_list_lock, flags);
 }
 
 static void gnttab_set_free(unsigned int start, unsigned int n)
 {
     unsigned int i;
 
     for (i = start; i < start + n - 1; i++)
         gnttab_entry(i) = i + 1;
 
     gnttab_entry(i) = GNTTAB_LIST_END;
     if (!gnttab_free_count) {
         gnttab_free_head = start;
         gnttab_free_tail_ptr = &gnttab_free_head;
     } else {
         gnttab_entry(gnttab_last_free) = start;
     }
     gnttab_free_count += n;
     gnttab_last_free = i;
 
     bitmap_set(gnttab_free_bitmap, start, n);
 }
 
 /*
  * 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: Frame to which access is permitted.
  *  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)
 {
     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)
 {
     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)
 {
     return gnttab_interface->end_foreign_access_ref(ref);
 }
 
 int gnttab_end_foreign_access_ref(grant_ref_t ref)
 {
     if (_gnttab_end_foreign_access_ref(ref))
         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;
     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)) {
             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, 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->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);
 
     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, struct page *page)
 {
     if (gnttab_try_end_foreign_access(ref)) {
         if (page)
             put_page(page);
     } else
         gnttab_add_deferred(ref, page);
 }
 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
 
 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;
 
     spin_lock_irqsave(&gnttab_list_lock, flags);
     while (head != GNTTAB_LIST_END) {
         ref = gnttab_entry(head);
         put_free_entry_locked(head);
         head = ref;
     }
     check_free_callbacks();
     spin_unlock_irqrestore(&gnttab_list_lock, flags);
 }
 EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
 
 void gnttab_free_grant_reference_seq(grant_ref_t head, unsigned int count)
 {
     unsigned long flags;
     unsigned int i;
 
     spin_lock_irqsave(&gnttab_list_lock, flags);
     for (i = count; i > 0; i--)
         put_free_entry_locked(head + i - 1);
     check_free_callbacks();
     spin_unlock_irqrestore(&gnttab_list_lock, flags);
 }
 EXPORT_SYMBOL_GPL(gnttab_free_grant_reference_seq);
 
 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_alloc_grant_reference_seq(unsigned int count, grant_ref_t *first)
 {
     int h;
 
     if (count == 1)
         h = get_free_entries(1);
     else
         h = get_free_entries_seq(count);
 
     if (h < 0)
         return -ENOSPC;
 
     *first = h;
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(gnttab_alloc_grant_reference_seq);
 
 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;
 
     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;
     }
 
     gnttab_set_free(gnttab_size, extra_entries);
 
     if (!gnttab_free_tail_ptr)
         gnttab_free_tail_ptr = __gnttab_entry(gnttab_size);
 
     nr_grant_frames = new_nr_grant_frames;
     gnttab_size += extra_entries;
 
     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 = memremap(addr, XEN_PAGE_SIZE * max_nr_gframes, MEMREMAP_WB);
     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) {
         memunmap(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);
     memunmap(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 = xen_alloc_unpopulated_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);
 
 #ifdef CONFIG_XEN_UNPOPULATED_ALLOC
 static inline void cache_init(struct gnttab_page_cache *cache)
 {
     cache->pages = NULL;
 }
 
 static inline bool cache_empty(struct gnttab_page_cache *cache)
 {
     return !cache->pages;
 }
 
 static inline struct page *cache_deq(struct gnttab_page_cache *cache)
 {
     struct page *page;
 
     page = cache->pages;
     cache->pages = page->zone_device_data;
 
     return page;
 }
 
 static inline void cache_enq(struct gnttab_page_cache *cache, struct page *page)
 {
     page->zone_device_data = cache->pages;
     cache->pages = page;
 }
 #else
 static inline void cache_init(struct gnttab_page_cache *cache)
 {
     INIT_LIST_HEAD(&cache->pages);
 }
 
 static inline bool cache_empty(struct gnttab_page_cache *cache)
 {
     return list_empty(&cache->pages);
 }
 
 static inline struct page *cache_deq(struct gnttab_page_cache *cache)
 {
     struct page *page;
 
     page = list_first_entry(&cache->pages, struct page, lru);
     list_del(&page->lru);
 
     return page;
 }
 
 static inline void cache_enq(struct gnttab_page_cache *cache, struct page *page)
 {
     list_add(&page->lru, &cache->pages);
 }
 #endif
 
 void gnttab_page_cache_init(struct gnttab_page_cache *cache)
 {
     spin_lock_init(&cache->lock);
     cache_init(cache);
     cache->num_pages = 0;
 }
 EXPORT_SYMBOL_GPL(gnttab_page_cache_init);
 
 int gnttab_page_cache_get(struct gnttab_page_cache *cache, struct page **page)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&cache->lock, flags);
 
     if (cache_empty(cache)) {
         spin_unlock_irqrestore(&cache->lock, flags);
         return gnttab_alloc_pages(1, page);
     }
 
     page[0] = cache_deq(cache);
     cache->num_pages--;
 
     spin_unlock_irqrestore(&cache->lock, flags);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(gnttab_page_cache_get);
 
 void gnttab_page_cache_put(struct gnttab_page_cache *cache, struct page **page,
                unsigned int num)
 {
     unsigned long flags;
     unsigned int i;
 
     spin_lock_irqsave(&cache->lock, flags);
 
     for (i = 0; i < num; i++)
         cache_enq(cache, page[i]);
     cache->num_pages += num;
 
     spin_unlock_irqrestore(&cache->lock, flags);
 }
 EXPORT_SYMBOL_GPL(gnttab_page_cache_put);
 
 void gnttab_page_cache_shrink(struct gnttab_page_cache *cache, unsigned int num)
 {
     struct page *page[10];
     unsigned int i = 0;
     unsigned long flags;
 
     spin_lock_irqsave(&cache->lock, flags);
 
     while (cache->num_pages > num) {
         page[i] = cache_deq(cache);
         cache->num_pages--;
         if (++i == ARRAY_SIZE(page)) {
             spin_unlock_irqrestore(&cache->lock, flags);
             gnttab_free_pages(i, page);
             i = 0;
             spin_lock_irqsave(&cache->lock, flags);
         }
     }
 
     spin_unlock_irqrestore(&cache->lock, flags);
 
     if (i != 0)
         gnttab_free_pages(i, page);
 }
 EXPORT_SYMBOL_GPL(gnttab_page_cache_shrink);
 
 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);
     xen_free_unpopulated_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;
 
     if (args->nr_pages < 0 || args->nr_pages > (INT_MAX >> PAGE_SHIFT))
         return -ENOMEM;
 
     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)
 {
     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,
     .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,
     .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 is not mapped!\n");
             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;
 
     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, max_nr_grefs;
     unsigned int max_nr_glist_frames, nr_glist_frames;
     int ret;
 
     gnttab_request_version();
     max_nr_grant_frames = gnttab_max_grant_frames();
     max_nr_grefs = max_nr_grant_frames *
             gnttab_interface->grefs_per_grant_frame;
     nr_grant_frames = 1;
 
     /* Determine the maximum number of frames required for the
      * grant reference free list on the current hypervisor.
      */
     max_nr_glist_frames = max_nr_grefs / 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;
         }
     }
 
     gnttab_free_bitmap = bitmap_zalloc(max_nr_grefs, GFP_KERNEL);
     if (!gnttab_free_bitmap) {
         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;
     }
 
     gnttab_size = nr_grant_frames * gnttab_interface->grefs_per_grant_frame;
 
     gnttab_set_free(GNTTAB_NR_RESERVED_ENTRIES,
             gnttab_size - GNTTAB_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);
     bitmap_free(gnttab_free_bitmap);
     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);

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