/*
 *    Copyright IBM Corp. 2007, 2011
 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/quicklist.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/swapops.h>
#include <linux/ksm.h>
#include <linux/mman.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>

#ifndef CONFIG_64BIT
#define ALLOC_ORDER     1
#define FRAG_MASK       0x0f
#else
#define ALLOC_ORDER     2
#define FRAG_MASK       0x03
#endif


unsigned long *crst_table_alloc(struct mm_struct *mm)
{
        struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);

        if (!page)
                return NULL;
        return (unsigned long *) page_to_phys(page);
}

void crst_table_free(struct mm_struct *mm, unsigned long *table)
{
        free_pages((unsigned long) table, ALLOC_ORDER);
}

#ifdef CONFIG_64BIT
static void __crst_table_upgrade(void *arg)
{
        struct mm_struct *mm = arg;

        if (current->active_mm == mm) {
                clear_user_asce();
                set_user_asce(mm);
        }
        __tlb_flush_local();
}

int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
{
        unsigned long *table, *pgd;
        unsigned long entry;
        int flush;

        BUG_ON(limit > (1UL << 53));
        flush = 0;
repeat:
        table = crst_table_alloc(mm);
        if (!table)
                return -ENOMEM;
        spin_lock_bh(&mm->page_table_lock);
        if (mm->context.asce_limit < limit) {
                pgd = (unsigned long *) mm->pgd;
                if (mm->context.asce_limit <= (1UL << 31)) {
                        entry = _REGION3_ENTRY_EMPTY;
                        mm->context.asce_limit = 1UL << 42;
                        mm->context.asce_bits = _ASCE_TABLE_LENGTH |
                                                _ASCE_USER_BITS |
                                                _ASCE_TYPE_REGION3;
                } else {
                        entry = _REGION2_ENTRY_EMPTY;
                        mm->context.asce_limit = 1UL << 53;
                        mm->context.asce_bits = _ASCE_TABLE_LENGTH |
                                                _ASCE_USER_BITS |
                                                _ASCE_TYPE_REGION2;
                }
                crst_table_init(table, entry);
                pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd);
                mm->pgd = (pgd_t *) table;
                mm->task_size = mm->context.asce_limit;
                table = NULL;
                flush = 1;
        }
        spin_unlock_bh(&mm->page_table_lock);
        if (table)
                crst_table_free(mm, table);
        if (mm->context.asce_limit < limit)
                goto repeat;
        if (flush)
                on_each_cpu(__crst_table_upgrade, mm, 0);
        return 0;
}

void crst_table_downgrade(struct mm_struct *mm, unsigned long limit)
{
        pgd_t *pgd;

        if (current->active_mm == mm) {
                clear_user_asce();
                __tlb_flush_mm(mm);
        }
        while (mm->context.asce_limit > limit) {
                pgd = mm->pgd;
                switch (pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) {
                case _REGION_ENTRY_TYPE_R2:
                        mm->context.asce_limit = 1UL << 42;
                        mm->context.asce_bits = _ASCE_TABLE_LENGTH |
                                                _ASCE_USER_BITS |
                                                _ASCE_TYPE_REGION3;
                        break;
                case _REGION_ENTRY_TYPE_R3:
                        mm->context.asce_limit = 1UL << 31;
                        mm->context.asce_bits = _ASCE_TABLE_LENGTH |
                                                _ASCE_USER_BITS |
                                                _ASCE_TYPE_SEGMENT;
                        break;
                default:
                        BUG();
                }
                mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
                mm->task_size = mm->context.asce_limit;
                crst_table_free(mm, (unsigned long *) pgd);
        }
        if (current->active_mm == mm)
                set_user_asce(mm);
}
#endif

#ifdef CONFIG_PGSTE

/**
 * gmap_alloc - allocate a guest address space
 * @mm: pointer to the parent mm_struct
 * @limit: maximum size of the gmap address space
 *
 * Returns a guest address space structure.
 */
struct gmap *gmap_alloc(struct mm_struct *mm, unsigned long limit)
{
        struct gmap *gmap;
        struct page *page;
        unsigned long *table;
        unsigned long etype, atype;

        if (limit < (1UL << 31)) {
                limit = (1UL << 31) - 1;
                atype = _ASCE_TYPE_SEGMENT;
                etype = _SEGMENT_ENTRY_EMPTY;
        } else if (limit < (1UL << 42)) {
                limit = (1UL << 42) - 1;
                atype = _ASCE_TYPE_REGION3;
                etype = _REGION3_ENTRY_EMPTY;
        } else if (limit < (1UL << 53)) {
                limit = (1UL << 53) - 1;
                atype = _ASCE_TYPE_REGION2;
                etype = _REGION2_ENTRY_EMPTY;
        } else {
                limit = -1UL;
                atype = _ASCE_TYPE_REGION1;
                etype = _REGION1_ENTRY_EMPTY;
        }
        gmap = kzalloc(sizeof(struct gmap), GFP_KERNEL);
        if (!gmap)
                goto out;
        INIT_LIST_HEAD(&gmap->crst_list);
        INIT_RADIX_TREE(&gmap->guest_to_host, GFP_KERNEL);
        INIT_RADIX_TREE(&gmap->host_to_guest, GFP_ATOMIC);
        spin_lock_init(&gmap->guest_table_lock);
        gmap->mm = mm;
        page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
        if (!page)
                goto out_free;
        page->index = 0;
        list_add(&page->lru, &gmap->crst_list);
        table = (unsigned long *) page_to_phys(page);
        crst_table_init(table, etype);
        gmap->table = table;
        gmap->asce = atype | _ASCE_TABLE_LENGTH |
                _ASCE_USER_BITS | __pa(table);
        gmap->asce_end = limit;
        down_write(&mm->mmap_sem);
        list_add(&gmap->list, &mm->context.gmap_list);
        up_write(&mm->mmap_sem);
        return gmap;

out_free:
        kfree(gmap);
out:
        return NULL;
}
EXPORT_SYMBOL_GPL(gmap_alloc);

static void gmap_flush_tlb(struct gmap *gmap)
{
        if (MACHINE_HAS_IDTE)
                __tlb_flush_asce(gmap->mm, gmap->asce);
        else
                __tlb_flush_global();
}

static void gmap_radix_tree_free(struct radix_tree_root *root)
{
        struct radix_tree_iter iter;
        unsigned long indices[16];
        unsigned long index;
        void **slot;
        int i, nr;

        /* A radix tree is freed by deleting all of its entries */
        index = 0;
        do {
                nr = 0;
                radix_tree_for_each_slot(slot, root, &iter, index) {
                        indices[nr] = iter.index;
                        if (++nr == 16)
                                break;
                }
                for (i = 0; i < nr; i++) {
                        index = indices[i];
                        radix_tree_delete(root, index);
                }
        } while (nr > 0);
}

/**
 * gmap_free - free a guest address space
 * @gmap: pointer to the guest address space structure
 */
void gmap_free(struct gmap *gmap)
{
        struct page *page, *next;

        /* Flush tlb. */
        if (MACHINE_HAS_IDTE)
                __tlb_flush_asce(gmap->mm, gmap->asce);
        else
                __tlb_flush_global();

        /* Free all segment & region tables. */
        list_for_each_entry_safe(page, next, &gmap->crst_list, lru)
                __free_pages(page, ALLOC_ORDER);
        gmap_radix_tree_free(&gmap->guest_to_host);
        gmap_radix_tree_free(&gmap->host_to_guest);
        down_write(&gmap->mm->mmap_sem);
        list_del(&gmap->list);
        up_write(&gmap->mm->mmap_sem);
        kfree(gmap);
}
EXPORT_SYMBOL_GPL(gmap_free);

/**
 * gmap_enable - switch primary space to the guest address space
 * @gmap: pointer to the guest address space structure
 */
void gmap_enable(struct gmap *gmap)
{
        S390_lowcore.gmap = (unsigned long) gmap;
}
EXPORT_SYMBOL_GPL(gmap_enable);

/**
 * gmap_disable - switch back to the standard primary address space
 * @gmap: pointer to the guest address space structure
 */
void gmap_disable(struct gmap *gmap)
{
        S390_lowcore.gmap = 0UL;
}
EXPORT_SYMBOL_GPL(gmap_disable);

/*
 * gmap_alloc_table is assumed to be called with mmap_sem held
 */
static int gmap_alloc_table(struct gmap *gmap, unsigned long *table,
                            unsigned long init, unsigned long gaddr)
{
        struct page *page;
        unsigned long *new;

        /* since we dont free the gmap table until gmap_free we can unlock */
        page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
        if (!page)
                return -ENOMEM;
        new = (unsigned long *) page_to_phys(page);
        crst_table_init(new, init);
        spin_lock(&gmap->mm->page_table_lock);
        if (*table & _REGION_ENTRY_INVALID) {
                list_add(&page->lru, &gmap->crst_list);
                *table = (unsigned long) new | _REGION_ENTRY_LENGTH |
                        (*table & _REGION_ENTRY_TYPE_MASK);
                page->index = gaddr;
                page = NULL;
        }
        spin_unlock(&gmap->mm->page_table_lock);
        if (page)
                __free_pages(page, ALLOC_ORDER);
        return 0;
}

/**
 * __gmap_segment_gaddr - find virtual address from segment pointer
 * @entry: pointer to a segment table entry in the guest address space
 *
 * Returns the virtual address in the guest address space for the segment
 */
static unsigned long __gmap_segment_gaddr(unsigned long *entry)
{
        struct page *page;
        unsigned long offset, mask;

        offset = (unsigned long) entry / sizeof(unsigned long);
        offset = (offset & (PTRS_PER_PMD - 1)) * PMD_SIZE;
        mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
        page = virt_to_page((void *)((unsigned long) entry & mask));
        return page->index + offset;
}

/**
 * __gmap_unlink_by_vmaddr - unlink a single segment via a host address
 * @gmap: pointer to the guest address space structure
 * @vmaddr: address in the host process address space
 *
 * Returns 1 if a TLB flush is required
 */
static int __gmap_unlink_by_vmaddr(struct gmap *gmap, unsigned long vmaddr)
{
        unsigned long *entry;
        int flush = 0;

        spin_lock(&gmap->guest_table_lock);
        entry = radix_tree_delete(&gmap->host_to_guest, vmaddr >> PMD_SHIFT);
        if (entry) {
                flush = (*entry != _SEGMENT_ENTRY_INVALID);
                *entry = _SEGMENT_ENTRY_INVALID;
        }
        spin_unlock(&gmap->guest_table_lock);
        return flush;
}

/**
 * __gmap_unmap_by_gaddr - unmap a single segment via a guest address
 * @gmap: pointer to the guest address space structure
 * @gaddr: address in the guest address space
 *
 * Returns 1 if a TLB flush is required
 */
static int __gmap_unmap_by_gaddr(struct gmap *gmap, unsigned long gaddr)
{
        unsigned long vmaddr;

        vmaddr = (unsigned long) radix_tree_delete(&gmap->guest_to_host,
                                                   gaddr >> PMD_SHIFT);
        return vmaddr ? __gmap_unlink_by_vmaddr(gmap, vmaddr) : 0;
}

/**
 * gmap_unmap_segment - unmap segment from the guest address space
 * @gmap: pointer to the guest address space structure
 * @to: address in the guest address space
 * @len: length of the memory area to unmap
 *
 * Returns 0 if the unmap succeeded, -EINVAL if not.
 */
int gmap_unmap_segment(struct gmap *gmap, unsigned long to, unsigned long len)
{
        unsigned long off;
        int flush;

        if ((to | len) & (PMD_SIZE - 1))
                return -EINVAL;
        if (len == 0 || to + len < to)
                return -EINVAL;

        flush = 0;
        down_write(&gmap->mm->mmap_sem);
        for (off = 0; off < len; off += PMD_SIZE)
                flush |= __gmap_unmap_by_gaddr(gmap, to + off);
        up_write(&gmap->mm->mmap_sem);
        if (flush)
                gmap_flush_tlb(gmap);
        return 0;
}
EXPORT_SYMBOL_GPL(gmap_unmap_segment);

/**
 * gmap_mmap_segment - map a segment to the guest address space
 * @gmap: pointer to the guest address space structure
 * @from: source address in the parent address space
 * @to: target address in the guest address space
 * @len: length of the memory area to map
 *
 * Returns 0 if the mmap succeeded, -EINVAL or -ENOMEM if not.
 */
int gmap_map_segment(struct gmap *gmap, unsigned long from,
                     unsigned long to, unsigned long len)
{
        unsigned long off;
        int flush;

        if ((from | to | len) & (PMD_SIZE - 1))
                return -EINVAL;
        if (len == 0 || from + len < from || to + len < to ||
            from + len > TASK_MAX_SIZE || to + len > gmap->asce_end)
                return -EINVAL;

        flush = 0;
        down_write(&gmap->mm->mmap_sem);
        for (off = 0; off < len; off += PMD_SIZE) {
                /* Remove old translation */
                flush |= __gmap_unmap_by_gaddr(gmap, to + off);
                /* Store new translation */
                if (radix_tree_insert(&gmap->guest_to_host,
                                      (to + off) >> PMD_SHIFT,
                                      (void *) from + off))
                        break;
        }
        up_write(&gmap->mm->mmap_sem);
        if (flush)
                gmap_flush_tlb(gmap);
        if (off >= len)
                return 0;
        gmap_unmap_segment(gmap, to, len);
        return -ENOMEM;
}
EXPORT_SYMBOL_GPL(gmap_map_segment);

/**
 * __gmap_translate - translate a guest address to a user space address
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: guest address
 *
 * Returns user space address which corresponds to the guest address or
 * -EFAULT if no such mapping exists.
 * This function does not establish potentially missing page table entries.
 * The mmap_sem of the mm that belongs to the address space must be held
 * when this function gets called.
 */
unsigned long __gmap_translate(struct gmap *gmap, unsigned long gaddr)
{
        unsigned long vmaddr;

        vmaddr = (unsigned long)
                radix_tree_lookup(&gmap->guest_to_host, gaddr >> PMD_SHIFT);
        return vmaddr ? (vmaddr | (gaddr & ~PMD_MASK)) : -EFAULT;
}
EXPORT_SYMBOL_GPL(__gmap_translate);

/**
 * gmap_translate - translate a guest address to a user space address
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: guest address
 *
 * Returns user space address which corresponds to the guest address or
 * -EFAULT if no such mapping exists.
 * This function does not establish potentially missing page table entries.
 */
unsigned long gmap_translate(struct gmap *gmap, unsigned long gaddr)
{
        unsigned long rc;

        down_read(&gmap->mm->mmap_sem);
        rc = __gmap_translate(gmap, gaddr);
        up_read(&gmap->mm->mmap_sem);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_translate);

/**
 * gmap_unlink - disconnect a page table from the gmap shadow tables
 * @gmap: pointer to guest mapping meta data structure
 * @table: pointer to the host page table
 * @vmaddr: vm address associated with the host page table
 */
static void gmap_unlink(struct mm_struct *mm, unsigned long *table,
                        unsigned long vmaddr)
{
        struct gmap *gmap;
        int flush;

        list_for_each_entry(gmap, &mm->context.gmap_list, list) {
                flush = __gmap_unlink_by_vmaddr(gmap, vmaddr);
                if (flush)
                        gmap_flush_tlb(gmap);
        }
}

/**
 * gmap_link - set up shadow page tables to connect a host to a guest address
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: guest address
 * @vmaddr: vm address
 *
 * Returns 0 on success, -ENOMEM for out of memory conditions, and -EFAULT
 * if the vm address is already mapped to a different guest segment.
 * The mmap_sem of the mm that belongs to the address space must be held
 * when this function gets called.
 */
int __gmap_link(struct gmap *gmap, unsigned long gaddr, unsigned long vmaddr)
{
        struct mm_struct *mm;
        unsigned long *table;
        spinlock_t *ptl;
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        int rc;

        /* Create higher level tables in the gmap page table */
        table = gmap->table;
        if ((gmap->asce & _ASCE_TYPE_MASK) >= _ASCE_TYPE_REGION1) {
                table += (gaddr >> 53) & 0x7ff;
                if ((*table & _REGION_ENTRY_INVALID) &&
                    gmap_alloc_table(gmap, table, _REGION2_ENTRY_EMPTY,
                                     gaddr & 0xffe0000000000000UL))
                        return -ENOMEM;
                table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
        }
        if ((gmap->asce & _ASCE_TYPE_MASK) >= _ASCE_TYPE_REGION2) {
                table += (gaddr >> 42) & 0x7ff;
                if ((*table & _REGION_ENTRY_INVALID) &&
                    gmap_alloc_table(gmap, table, _REGION3_ENTRY_EMPTY,
                                     gaddr & 0xfffffc0000000000UL))
                        return -ENOMEM;
                table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
        }
        if ((gmap->asce & _ASCE_TYPE_MASK) >= _ASCE_TYPE_REGION3) {
                table += (gaddr >> 31) & 0x7ff;
                if ((*table & _REGION_ENTRY_INVALID) &&
                    gmap_alloc_table(gmap, table, _SEGMENT_ENTRY_EMPTY,
                                     gaddr & 0xffffffff80000000UL))
                        return -ENOMEM;
                table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
        }
        table += (gaddr >> 20) & 0x7ff;
        /* Walk the parent mm page table */
        mm = gmap->mm;
        pgd = pgd_offset(mm, vmaddr);
        VM_BUG_ON(pgd_none(*pgd));
        pud = pud_offset(pgd, vmaddr);
        VM_BUG_ON(pud_none(*pud));
        pmd = pmd_offset(pud, vmaddr);
        VM_BUG_ON(pmd_none(*pmd));
        /* large pmds cannot yet be handled */
        if (pmd_large(*pmd))
                return -EFAULT;
        /* Link gmap segment table entry location to page table. */
        rc = radix_tree_preload(GFP_KERNEL);
        if (rc)
                return rc;
        ptl = pmd_lock(mm, pmd);
        spin_lock(&gmap->guest_table_lock);
        if (*table == _SEGMENT_ENTRY_INVALID) {
                rc = radix_tree_insert(&gmap->host_to_guest,
                                       vmaddr >> PMD_SHIFT, table);
                if (!rc)
                        *table = pmd_val(*pmd);
        } else
                rc = 0;
        spin_unlock(&gmap->guest_table_lock);
        spin_unlock(ptl);
        radix_tree_preload_end();
        return rc;
}

/**
 * gmap_fault - resolve a fault on a guest address
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: guest address
 * @fault_flags: flags to pass down to handle_mm_fault()
 *
 * Returns 0 on success, -ENOMEM for out of memory conditions, and -EFAULT
 * if the vm address is already mapped to a different guest segment.
 */
int gmap_fault(struct gmap *gmap, unsigned long gaddr,
               unsigned int fault_flags)
{
        unsigned long vmaddr;
        int rc;

        down_read(&gmap->mm->mmap_sem);
        vmaddr = __gmap_translate(gmap, gaddr);
        if (IS_ERR_VALUE(vmaddr)) {
                rc = vmaddr;
                goto out_up;
        }
        if (fixup_user_fault(current, gmap->mm, vmaddr, fault_flags)) {
                rc = -EFAULT;
                goto out_up;
        }
        rc = __gmap_link(gmap, gaddr, vmaddr);
out_up:
        up_read(&gmap->mm->mmap_sem);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_fault);

static void gmap_zap_swap_entry(swp_entry_t entry, struct mm_struct *mm)
{
        if (!non_swap_entry(entry))
                dec_mm_counter(mm, MM_SWAPENTS);
        else if (is_migration_entry(entry)) {
                struct page *page = migration_entry_to_page(entry);

                if (PageAnon(page))
                        dec_mm_counter(mm, MM_ANONPAGES);
                else
                        dec_mm_counter(mm, MM_FILEPAGES);
        }
        free_swap_and_cache(entry);
}

/*
 * this function is assumed to be called with mmap_sem held
 */
void __gmap_zap(struct gmap *gmap, unsigned long gaddr)
{
        unsigned long vmaddr, ptev, pgstev;
        pte_t *ptep, pte;
        spinlock_t *ptl;
        pgste_t pgste;

        /* Find the vm address for the guest address */
        vmaddr = (unsigned long) radix_tree_lookup(&gmap->guest_to_host,
                                                   gaddr >> PMD_SHIFT);
        if (!vmaddr)
                return;
        vmaddr |= gaddr & ~PMD_MASK;
        /* Get pointer to the page table entry */
        ptep = get_locked_pte(gmap->mm, vmaddr, &ptl);
        if (unlikely(!ptep))
                return;
        pte = *ptep;
        if (!pte_swap(pte))
                goto out_pte;
        /* Zap unused and logically-zero pages */
        pgste = pgste_get_lock(ptep);
        pgstev = pgste_val(pgste);
        ptev = pte_val(pte);
        if (((pgstev & _PGSTE_GPS_USAGE_MASK) == _PGSTE_GPS_USAGE_UNUSED) ||
            ((pgstev & _PGSTE_GPS_ZERO) && (ptev & _PAGE_INVALID))) {
                gmap_zap_swap_entry(pte_to_swp_entry(pte), gmap->mm);
                pte_clear(gmap->mm, vmaddr, ptep);
        }
        pgste_set_unlock(ptep, pgste);
out_pte:
        pte_unmap_unlock(ptep, ptl);
}
EXPORT_SYMBOL_GPL(__gmap_zap);

void gmap_discard(struct gmap *gmap, unsigned long from, unsigned long to)
{
        unsigned long gaddr, vmaddr, size;
        struct vm_area_struct *vma;

        down_read(&gmap->mm->mmap_sem);
        for (gaddr = from; gaddr < to;
             gaddr = (gaddr + PMD_SIZE) & PMD_MASK) {
                /* Find the vm address for the guest address */
                vmaddr = (unsigned long)
                        radix_tree_lookup(&gmap->guest_to_host,
                                          gaddr >> PMD_SHIFT);
                if (!vmaddr)
                        continue;
                vmaddr |= gaddr & ~PMD_MASK;
                /* Find vma in the parent mm */
                vma = find_vma(gmap->mm, vmaddr);
                size = min(to - gaddr, PMD_SIZE - (gaddr & ~PMD_MASK));
                zap_page_range(vma, vmaddr, size, NULL);
        }
        up_read(&gmap->mm->mmap_sem);
}
EXPORT_SYMBOL_GPL(gmap_discard);

static LIST_HEAD(gmap_notifier_list);
static DEFINE_SPINLOCK(gmap_notifier_lock);

/**
 * gmap_register_ipte_notifier - register a pte invalidation callback
 * @nb: pointer to the gmap notifier block
 */
void gmap_register_ipte_notifier(struct gmap_notifier *nb)
{
        spin_lock(&gmap_notifier_lock);
        list_add(&nb->list, &gmap_notifier_list);
        spin_unlock(&gmap_notifier_lock);
}
EXPORT_SYMBOL_GPL(gmap_register_ipte_notifier);

/**
 * gmap_unregister_ipte_notifier - remove a pte invalidation callback
 * @nb: pointer to the gmap notifier block
 */
void gmap_unregister_ipte_notifier(struct gmap_notifier *nb)
{
        spin_lock(&gmap_notifier_lock);
        list_del_init(&nb->list);
        spin_unlock(&gmap_notifier_lock);
}
EXPORT_SYMBOL_GPL(gmap_unregister_ipte_notifier);

/**
 * gmap_ipte_notify - mark a range of ptes for invalidation notification
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @len: size of area
 *
 * Returns 0 if for each page in the given range a gmap mapping exists and
 * the invalidation notification could be set. If the gmap mapping is missing
 * for one or more pages -EFAULT is returned. If no memory could be allocated
 * -ENOMEM is returned. This function establishes missing page table entries.
 */
int gmap_ipte_notify(struct gmap *gmap, unsigned long gaddr, unsigned long len)
{
        unsigned long addr;
        spinlock_t *ptl;
        pte_t *ptep, entry;
        pgste_t pgste;
        int rc = 0;

        if ((gaddr & ~PAGE_MASK) || (len & ~PAGE_MASK))
                return -EINVAL;
        down_read(&gmap->mm->mmap_sem);
        while (len) {
                /* Convert gmap address and connect the page tables */
                addr = __gmap_translate(gmap, gaddr);
                if (IS_ERR_VALUE(addr)) {
                        rc = addr;
                        break;
                }
                /* Get the page mapped */
                if (fixup_user_fault(current, gmap->mm, addr, FAULT_FLAG_WRITE)) {
                        rc = -EFAULT;
                        break;
                }
                rc = __gmap_link(gmap, gaddr, addr);
                if (rc)
                        break;
                /* Walk the process page table, lock and get pte pointer */
                ptep = get_locked_pte(gmap->mm, addr, &ptl);
                VM_BUG_ON(!ptep);
                /* Set notification bit in the pgste of the pte */
                entry = *ptep;
                if ((pte_val(entry) & (_PAGE_INVALID | _PAGE_PROTECT)) == 0) {
                        pgste = pgste_get_lock(ptep);
                        pgste_val(pgste) |= PGSTE_IN_BIT;
                        pgste_set_unlock(ptep, pgste);
                        gaddr += PAGE_SIZE;
                        len -= PAGE_SIZE;
                }
                pte_unmap_unlock(ptep, ptl);
        }
        up_read(&gmap->mm->mmap_sem);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_ipte_notify);

/**
 * gmap_do_ipte_notify - call all invalidation callbacks for a specific pte.
 * @mm: pointer to the process mm_struct
 * @addr: virtual address in the process address space
 * @pte: pointer to the page table entry
 *
 * This function is assumed to be called with the page table lock held
 * for the pte to notify.
 */
void gmap_do_ipte_notify(struct mm_struct *mm, unsigned long vmaddr, pte_t *pte)
{
        unsigned long offset, gaddr;
        unsigned long *table;
        struct gmap_notifier *nb;
        struct gmap *gmap;

        offset = ((unsigned long) pte) & (255 * sizeof(pte_t));
        offset = offset * (4096 / sizeof(pte_t));
        spin_lock(&gmap_notifier_lock);
        list_for_each_entry(gmap, &mm->context.gmap_list, list) {
                table = radix_tree_lookup(&gmap->host_to_guest,
                                          vmaddr >> PMD_SHIFT);
                if (!table)
                        continue;
                gaddr = __gmap_segment_gaddr(table) + offset;
                list_for_each_entry(nb, &gmap_notifier_list, list)
                        nb->notifier_call(gmap, gaddr);
        }
        spin_unlock(&gmap_notifier_lock);
}
EXPORT_SYMBOL_GPL(gmap_do_ipte_notify);

static inline int page_table_with_pgste(struct page *page)
{
        return atomic_read(&page->_mapcount) == 0;
}

static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm)
{
        struct page *page;
        unsigned long *table;

        page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
        if (!page)
                return NULL;
        if (!pgtable_page_ctor(page)) {
                __free_page(page);
                return NULL;
        }
        atomic_set(&page->_mapcount, 0);
        table = (unsigned long *) page_to_phys(page);
        clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
        clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
        return table;
}

static inline void page_table_free_pgste(unsigned long *table)
{
        struct page *page;

        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
        pgtable_page_dtor(page);
        atomic_set(&page->_mapcount, -1);
        __free_page(page);
}

int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
                          unsigned long key, bool nq)
{
        spinlock_t *ptl;
        pgste_t old, new;
        pte_t *ptep;

        down_read(&mm->mmap_sem);
retry:
        ptep = get_locked_pte(mm, addr, &ptl);
        if (unlikely(!ptep)) {
                up_read(&mm->mmap_sem);
                return -EFAULT;
        }
        if (!(pte_val(*ptep) & _PAGE_INVALID) &&
             (pte_val(*ptep) & _PAGE_PROTECT)) {
                pte_unmap_unlock(ptep, ptl);
                if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE)) {
                        up_read(&mm->mmap_sem);
                        return -EFAULT;
                }
                goto retry;
        }

        new = old = pgste_get_lock(ptep);
        pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |
                            PGSTE_ACC_BITS | PGSTE_FP_BIT);
        pgste_val(new) |= (key & (_PAGE_CHANGED | _PAGE_REFERENCED)) << 48;
        pgste_val(new) |= (key & (_PAGE_ACC_BITS | _PAGE_FP_BIT)) << 56;
        if (!(pte_val(*ptep) & _PAGE_INVALID)) {
                unsigned long address, bits, skey;

                address = pte_val(*ptep) & PAGE_MASK;
                skey = (unsigned long) page_get_storage_key(address);
                bits = skey & (_PAGE_CHANGED | _PAGE_REFERENCED);
                skey = key & (_PAGE_ACC_BITS | _PAGE_FP_BIT);
                /* Set storage key ACC and FP */
                page_set_storage_key(address, skey, !nq);
                /* Merge host changed & referenced into pgste  */
                pgste_val(new) |= bits << 52;
        }
        /* changing the guest storage key is considered a change of the page */
        if ((pgste_val(new) ^ pgste_val(old)) &
            (PGSTE_ACC_BITS | PGSTE_FP_BIT | PGSTE_GR_BIT | PGSTE_GC_BIT))
                pgste_val(new) |= PGSTE_UC_BIT;

        pgste_set_unlock(ptep, new);
        pte_unmap_unlock(ptep, ptl);
        up_read(&mm->mmap_sem);
        return 0;
}
EXPORT_SYMBOL(set_guest_storage_key);

unsigned long get_guest_storage_key(struct mm_struct *mm, unsigned long addr)
{
        spinlock_t *ptl;
        pgste_t pgste;
        pte_t *ptep;
        uint64_t physaddr;
        unsigned long key = 0;

        down_read(&mm->mmap_sem);
        ptep = get_locked_pte(mm, addr, &ptl);
        if (unlikely(!ptep)) {
                up_read(&mm->mmap_sem);
                return -EFAULT;
        }
        pgste = pgste_get_lock(ptep);

        if (pte_val(*ptep) & _PAGE_INVALID) {
                key |= (pgste_val(pgste) & PGSTE_ACC_BITS) >> 56;
                key |= (pgste_val(pgste) & PGSTE_FP_BIT) >> 56;
                key |= (pgste_val(pgste) & PGSTE_GR_BIT) >> 48;
                key |= (pgste_val(pgste) & PGSTE_GC_BIT) >> 48;
        } else {
                physaddr = pte_val(*ptep) & PAGE_MASK;
                key = page_get_storage_key(physaddr);

                /* Reflect guest's logical view, not physical */
                if (pgste_val(pgste) & PGSTE_GR_BIT)
                        key |= _PAGE_REFERENCED;
                if (pgste_val(pgste) & PGSTE_GC_BIT)
                        key |= _PAGE_CHANGED;
        }

        pgste_set_unlock(ptep, pgste);
        pte_unmap_unlock(ptep, ptl);
        up_read(&mm->mmap_sem);
        return key;
}
EXPORT_SYMBOL(get_guest_storage_key);

#else /* CONFIG_PGSTE */

static inline int page_table_with_pgste(struct page *page)
{
        return 0;
}

static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm)
{
        return NULL;
}

static inline void page_table_free_pgste(unsigned long *table)
{
}

static inline void gmap_unlink(struct mm_struct *mm, unsigned long *table,
                        unsigned long vmaddr)
{
}

#endif /* CONFIG_PGSTE */

static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
{
        unsigned int old, new;

        do {
                old = atomic_read(v);
                new = old ^ bits;
        } while (atomic_cmpxchg(v, old, new) != old);
        return new;
}

/*
 * page table entry allocation/free routines.
 */
unsigned long *page_table_alloc(struct mm_struct *mm)
{
        unsigned long *uninitialized_var(table);
        struct page *uninitialized_var(page);
        unsigned int mask, bit;

        if (mm_has_pgste(mm))
                return page_table_alloc_pgste(mm);
        /* Allocate fragments of a 4K page as 1K/2K page table */
        spin_lock_bh(&mm->context.list_lock);
        mask = FRAG_MASK;
        if (!list_empty(&mm->context.pgtable_list)) {
                page = list_first_entry(&mm->context.pgtable_list,
                                        struct page, lru);
                table = (unsigned long *) page_to_phys(page);
                mask = atomic_read(&page->_mapcount);
                mask = mask | (mask >> 4);
        }
        if ((mask & FRAG_MASK) == FRAG_MASK) {
                spin_unlock_bh(&mm->context.list_lock);
                page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
                if (!page)
                        return NULL;
                if (!pgtable_page_ctor(page)) {
                        __free_page(page);
                        return NULL;
                }
                atomic_set(&page->_mapcount, 1);
                table = (unsigned long *) page_to_phys(page);
                clear_table(table, _PAGE_INVALID, PAGE_SIZE);
                spin_lock_bh(&mm->context.list_lock);
                list_add(&page->lru, &mm->context.pgtable_list);
        } else {

                for (bit = 1; mask & bit; bit <<= 1)
                        table += PTRS_PER_PTE;
                mask = atomic_xor_bits(&page->_mapcount, bit);
                if ((mask & FRAG_MASK) == FRAG_MASK)
                        list_del(&page->lru);
        }
        spin_unlock_bh(&mm->context.list_lock);
        return table;
}

void page_table_free(struct mm_struct *mm, unsigned long *table)
{
        struct page *page;
        unsigned int bit, mask;

        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
        if (page_table_with_pgste(page))
                return page_table_free_pgste(table);
        /* Free 1K/2K page table fragment of a 4K page */
        bit = 1 << ((__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)));
        spin_lock_bh(&mm->context.list_lock);
        if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
                list_del(&page->lru);
        mask = atomic_xor_bits(&page->_mapcount, bit);
        if (mask & FRAG_MASK)
                list_add(&page->lru, &mm->context.pgtable_list);
        spin_unlock_bh(&mm->context.list_lock);
        if (mask == 0) {
                pgtable_page_dtor(page);
                atomic_set(&page->_mapcount, -1);
                __free_page(page);
        }
}

static void __page_table_free_rcu(void *table, unsigned bit)
{
        struct page *page;

        if (bit == FRAG_MASK)
                return page_table_free_pgste(table);
        /* Free 1K/2K page table fragment of a 4K page */
        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
        if (atomic_xor_bits(&page->_mapcount, bit) == 0) {
                pgtable_page_dtor(page);
                atomic_set(&page->_mapcount, -1);
                __free_page(page);
        }
}

void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
                         unsigned long vmaddr)
{
        struct mm_struct *mm;
        struct page *page;
        unsigned int bit, mask;

        mm = tlb->mm;
        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
        if (page_table_with_pgste(page)) {
                gmap_unlink(mm, table, vmaddr);
                table = (unsigned long *) (__pa(table) | FRAG_MASK);
                tlb_remove_table(tlb, table);
                return;
        }
        bit = 1 << ((__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)));
        spin_lock_bh(&mm->context.list_lock);
        if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
                list_del(&page->lru);
        mask = atomic_xor_bits(&page->_mapcount, bit | (bit << 4));
        if (mask & FRAG_MASK)
                list_add_tail(&page->lru, &mm->context.pgtable_list);
        spin_unlock_bh(&mm->context.list_lock);
        table = (unsigned long *) (__pa(table) | (bit << 4));
        tlb_remove_table(tlb, table);
}

static void __tlb_remove_table(void *_table)
{
        const unsigned long mask = (FRAG_MASK << 4) | FRAG_MASK;
        void *table = (void *)((unsigned long) _table & ~mask);
        unsigned type = (unsigned long) _table & mask;

        if (type)
                __page_table_free_rcu(table, type);
        else
                free_pages((unsigned long) table, ALLOC_ORDER);
}

static void tlb_remove_table_smp_sync(void *arg)
{
        /* Simply deliver the interrupt */
}

static void tlb_remove_table_one(void *table)
{
        /*
         * This isn't an RCU grace period and hence the page-tables cannot be
         * assumed to be actually RCU-freed.
         *
         * It is however sufficient for software page-table walkers that rely
         * on IRQ disabling. See the comment near struct mmu_table_batch.
         */
        smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
        __tlb_remove_table(table);
}

static void tlb_remove_table_rcu(struct rcu_head *head)
{
        struct mmu_table_batch *batch;
        int i;

        batch = container_of(head, struct mmu_table_batch, rcu);

        for (i = 0; i < batch->nr; i++)
                __tlb_remove_table(batch->tables[i]);

        free_page((unsigned long)batch);
}

void tlb_table_flush(struct mmu_gather *tlb)
{
        struct mmu_table_batch **batch = &tlb->batch;

        if (*batch) {
                call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
                *batch = NULL;
        }
}

void tlb_remove_table(struct mmu_gather *tlb, void *table)
{
        struct mmu_table_batch **batch = &tlb->batch;

        tlb->mm->context.flush_mm = 1;
        if (*batch == NULL) {
                *batch = (struct mmu_table_batch *)
                        __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
                if (*batch == NULL) {
                        __tlb_flush_mm_lazy(tlb->mm);
                        tlb_remove_table_one(table);
                        return;
                }
                (*batch)->nr = 0;
        }
        (*batch)->tables[(*batch)->nr++] = table;
        if ((*batch)->nr == MAX_TABLE_BATCH)
                tlb_flush_mmu(tlb);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static inline void thp_split_vma(struct vm_area_struct *vma)
{
        unsigned long addr;

        for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE)
                follow_page(vma, addr, FOLL_SPLIT);
}

static inline void thp_split_mm(struct mm_struct *mm)
{
        struct vm_area_struct *vma;

        for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
                thp_split_vma(vma);
                vma->vm_flags &= ~VM_HUGEPAGE;
                vma->vm_flags |= VM_NOHUGEPAGE;
        }
        mm->def_flags |= VM_NOHUGEPAGE;
}
#else
static inline void thp_split_mm(struct mm_struct *mm)
{
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

static unsigned long page_table_realloc_pmd(struct mmu_gather *tlb,
                                struct mm_struct *mm, pud_t *pud,
                                unsigned long addr, unsigned long end)
{
        unsigned long next, *table, *new;
        struct page *page;
        spinlock_t *ptl;
        pmd_t *pmd;

        pmd = pmd_offset(pud, addr);
        do {
                next = pmd_addr_end(addr, end);
again:
                if (pmd_none_or_clear_bad(pmd))
                        continue;
                table = (unsigned long *) pmd_deref(*pmd);
                page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
                if (page_table_with_pgste(page))
                        continue;
                /* Allocate new page table with pgstes */
                new = page_table_alloc_pgste(mm);
                if (!new)
                        return -ENOMEM;

                ptl = pmd_lock(mm, pmd);
                if (likely((unsigned long *) pmd_deref(*pmd) == table)) {
                        /* Nuke pmd entry pointing to the "short" page table */
                        pmdp_flush_lazy(mm, addr, pmd);
                        pmd_clear(pmd);
                        /* Copy ptes from old table to new table */
                        memcpy(new, table, PAGE_SIZE/2);
                        clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
                        /* Establish new table */
                        pmd_populate(mm, pmd, (pte_t *) new);
                        /* Free old table with rcu, there might be a walker! */
                        page_table_free_rcu(tlb, table, addr);
                        new = NULL;
                }
                spin_unlock(ptl);
                if (new) {
                        page_table_free_pgste(new);
                        goto again;
                }
        } while (pmd++, addr = next, addr != end);

        return addr;
}

static unsigned long page_table_realloc_pud(struct mmu_gather *tlb,
                                   struct mm_struct *mm, pgd_t *pgd,
                                   unsigned long addr, unsigned long end)
{
        unsigned long next;
        pud_t *pud;

        pud = pud_offset(pgd, addr);
        do {
                next = pud_addr_end(addr, end);
                if (pud_none_or_clear_bad(pud))
                        continue;
                next = page_table_realloc_pmd(tlb, mm, pud, addr, next);
                if (unlikely(IS_ERR_VALUE(next)))
                        return next;
        } while (pud++, addr = next, addr != end);

        return addr;
}

static unsigned long page_table_realloc(struct mmu_gather *tlb, struct mm_struct *mm,
                                        unsigned long addr, unsigned long end)
{
        unsigned long next;
        pgd_t *pgd;

        pgd = pgd_offset(mm, addr);
        do {
                next = pgd_addr_end(addr, end);
                if (pgd_none_or_clear_bad(pgd))
                        continue;
                next = page_table_realloc_pud(tlb, mm, pgd, addr, next);
                if (unlikely(IS_ERR_VALUE(next)))
                        return next;
        } while (pgd++, addr = next, addr != end);

        return 0;
}

/*
 * switch on pgstes for its userspace process (for kvm)
 */
int s390_enable_sie(void)
{
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        struct mmu_gather tlb;

        /* Do we have pgstes? if yes, we are done */
        if (mm_has_pgste(tsk->mm))
                return 0;

        down_write(&mm->mmap_sem);
        /* split thp mappings and disable thp for future mappings */
        thp_split_mm(mm);
        /* Reallocate the page tables with pgstes */
        tlb_gather_mmu(&tlb, mm, 0, TASK_SIZE);
        if (!page_table_realloc(&tlb, mm, 0, TASK_SIZE))
                mm->context.has_pgste = 1;
        tlb_finish_mmu(&tlb, 0, TASK_SIZE);
        up_write(&mm->mmap_sem);
        return mm->context.has_pgste ? 0 : -ENOMEM;
}
EXPORT_SYMBOL_GPL(s390_enable_sie);

/*
 * Enable storage key handling from now on and initialize the storage
 * keys with the default key.
 */
static int __s390_enable_skey(pte_t *pte, unsigned long addr,
                              unsigned long next, struct mm_walk *walk)
{
        unsigned long ptev;
        pgste_t pgste;

        pgste = pgste_get_lock(pte);
        /*
         * Remove all zero page mappings,
         * after establishing a policy to forbid zero page mappings
         * following faults for that page will get fresh anonymous pages
         */
        if (is_zero_pfn(pte_pfn(*pte))) {
                ptep_flush_direct(walk->mm, addr, pte);
                pte_val(*pte) = _PAGE_INVALID;
        }
        /* Clear storage key */
        pgste_val(pgste) &= ~(PGSTE_ACC_BITS | PGSTE_FP_BIT |
                              PGSTE_GR_BIT | PGSTE_GC_BIT);
        ptev = pte_val(*pte);
        if (!(ptev & _PAGE_INVALID) && (ptev & _PAGE_WRITE))
                page_set_storage_key(ptev & PAGE_MASK, PAGE_DEFAULT_KEY, 1);
        pgste_set_unlock(pte, pgste);
        return 0;
}

int s390_enable_skey(void)
{
        struct mm_walk walk = { .pte_entry = __s390_enable_skey };
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        int rc = 0;

        down_write(&mm->mmap_sem);
        if (mm_use_skey(mm))
                goto out_up;

        mm->context.use_skey = 1;
        for (vma = mm->mmap; vma; vma = vma->vm_next) {
                if (ksm_madvise(vma, vma->vm_start, vma->vm_end,
                                MADV_UNMERGEABLE, &vma->vm_flags)) {
                        mm->context.use_skey = 0;
                        rc = -ENOMEM;
                        goto out_up;
                }
        }
        mm->def_flags &= ~VM_MERGEABLE;

        walk.mm = mm;
        walk_page_range(0, TASK_SIZE, &walk);

out_up:
        up_write(&mm->mmap_sem);
        return rc;
}
EXPORT_SYMBOL_GPL(s390_enable_skey);

/*
 * Reset CMMA state, make all pages stable again.
 */
static int __s390_reset_cmma(pte_t *pte, unsigned long addr,
                             unsigned long next, struct mm_walk *walk)
{
        pgste_t pgste;

        pgste = pgste_get_lock(pte);
        pgste_val(pgste) &= ~_PGSTE_GPS_USAGE_MASK;
        pgste_set_unlock(pte, pgste);
        return 0;
}

void s390_reset_cmma(struct mm_struct *mm)
{
        struct mm_walk walk = { .pte_entry = __s390_reset_cmma };

        down_write(&mm->mmap_sem);
        walk.mm = mm;
        walk_page_range(0, TASK_SIZE, &walk);
        up_write(&mm->mmap_sem);
}
EXPORT_SYMBOL_GPL(s390_reset_cmma);

/*
 * Test and reset if a guest page is dirty
 */
bool gmap_test_and_clear_dirty(unsigned long address, struct gmap *gmap)
{
        pte_t *pte;
        spinlock_t *ptl;
        bool dirty = false;

        pte = get_locked_pte(gmap->mm, address, &ptl);
        if (unlikely(!pte))
                return false;

        if (ptep_test_and_clear_user_dirty(gmap->mm, address, pte))
                dirty = true;

        spin_unlock(ptl);
        return dirty;
}
EXPORT_SYMBOL_GPL(gmap_test_and_clear_dirty);

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
int pmdp_clear_flush_young(struct vm_area_struct *vma, unsigned long address,
                           pmd_t *pmdp)
{
        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
        /* No need to flush TLB
         * On s390 reference bits are in storage key and never in TLB */
        return pmdp_test_and_clear_young(vma, address, pmdp);
}

int pmdp_set_access_flags(struct vm_area_struct *vma,
                          unsigned long address, pmd_t *pmdp,
                          pmd_t entry, int dirty)
{
        VM_BUG_ON(address & ~HPAGE_PMD_MASK);

        entry = pmd_mkyoung(entry);
        if (dirty)
                entry = pmd_mkdirty(entry);
        if (pmd_same(*pmdp, entry))
                return 0;
        pmdp_invalidate(vma, address, pmdp);
        set_pmd_at(vma->vm_mm, address, pmdp, entry);
        return 1;
}

static void pmdp_splitting_flush_sync(void *arg)
{
        /* Simply deliver the interrupt */
}

void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
                          pmd_t *pmdp)
{
        VM_BUG_ON(address & ~HPAGE_PMD_MASK);
        if (!test_and_set_bit(_SEGMENT_ENTRY_SPLIT_BIT,
                              (unsigned long *) pmdp)) {
                /* need to serialize against gup-fast (IRQ disabled) */
                smp_call_function(pmdp_splitting_flush_sync, NULL, 1);
        }
}

void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
                                pgtable_t pgtable)
{
        struct list_head *lh = (struct list_head *) pgtable;

        assert_spin_locked(pmd_lockptr(mm, pmdp));

        /* FIFO */
        if (!pmd_huge_pte(mm, pmdp))
                INIT_LIST_HEAD(lh);
        else
                list_add(lh, (struct list_head *) pmd_huge_pte(mm, pmdp));
        pmd_huge_pte(mm, pmdp) = pgtable;
}

pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
{
        struct list_head *lh;
        pgtable_t pgtable;
        pte_t *ptep;

        assert_spin_locked(pmd_lockptr(mm, pmdp));

        /* FIFO */
        pgtable = pmd_huge_pte(mm, pmdp);
        lh = (struct list_head *) pgtable;
        if (list_empty(lh))
                pmd_huge_pte(mm, pmdp) = NULL;
        else {
                pmd_huge_pte(mm, pmdp) = (pgtable_t) lh->next;
                list_del(lh);
        }
        ptep = (pte_t *) pgtable;
        pte_val(*ptep) = _PAGE_INVALID;
        ptep++;
        pte_val(*ptep) = _PAGE_INVALID;
        return pgtable;
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */