Merge tag 'powerpc-6.10-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc...

[linux-block.git] / arch / s390 / mm / gmap.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  KVM guest address space mapping code
 *
 *    Copyright IBM Corp. 2007, 2020
 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 *               David Hildenbrand <david@redhat.com>
 *               Janosch Frank <frankja@linux.vnet.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/pagewalk.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/swapops.h>
#include <linux/ksm.h>
#include <linux/mman.h>
#include <linux/pgtable.h>
#include <asm/page-states.h>
#include <asm/pgalloc.h>
#include <asm/gmap.h>
#include <asm/page.h>
#include <asm/tlb.h>

#define GMAP_SHADOW_FAKE_TABLE 1ULL

static struct page *gmap_alloc_crst(void)
{
        struct page *page;

        page = alloc_pages(GFP_KERNEL_ACCOUNT, CRST_ALLOC_ORDER);
        if (!page)
                return NULL;
        __arch_set_page_dat(page_to_virt(page), 1UL << CRST_ALLOC_ORDER);
        return page;
}

/**
 * gmap_alloc - allocate and initialize a guest address space
 * @limit: maximum address of the gmap address space
 *
 * Returns a guest address space structure.
 */
static struct gmap *gmap_alloc(unsigned long limit)
{
        struct gmap *gmap;
        struct page *page;
        unsigned long *table;
        unsigned long etype, atype;

        if (limit < _REGION3_SIZE) {
                limit = _REGION3_SIZE - 1;
                atype = _ASCE_TYPE_SEGMENT;
                etype = _SEGMENT_ENTRY_EMPTY;
        } else if (limit < _REGION2_SIZE) {
                limit = _REGION2_SIZE - 1;
                atype = _ASCE_TYPE_REGION3;
                etype = _REGION3_ENTRY_EMPTY;
        } else if (limit < _REGION1_SIZE) {
                limit = _REGION1_SIZE - 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_ACCOUNT);
        if (!gmap)
                goto out;
        INIT_LIST_HEAD(&gmap->crst_list);
        INIT_LIST_HEAD(&gmap->children);
        INIT_LIST_HEAD(&gmap->pt_list);
        INIT_RADIX_TREE(&gmap->guest_to_host, GFP_KERNEL_ACCOUNT);
        INIT_RADIX_TREE(&gmap->host_to_guest, GFP_ATOMIC | __GFP_ACCOUNT);
        INIT_RADIX_TREE(&gmap->host_to_rmap, GFP_ATOMIC | __GFP_ACCOUNT);
        spin_lock_init(&gmap->guest_table_lock);
        spin_lock_init(&gmap->shadow_lock);
        refcount_set(&gmap->ref_count, 1);
        page = gmap_alloc_crst();
        if (!page)
                goto out_free;
        page->index = 0;
        list_add(&page->lru, &gmap->crst_list);
        table = page_to_virt(page);
        crst_table_init(table, etype);
        gmap->table = table;
        gmap->asce = atype | _ASCE_TABLE_LENGTH |
                _ASCE_USER_BITS | __pa(table);
        gmap->asce_end = limit;
        return gmap;

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

/**
 * gmap_create - create 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_create(struct mm_struct *mm, unsigned long limit)
{
        struct gmap *gmap;
        unsigned long gmap_asce;

        gmap = gmap_alloc(limit);
        if (!gmap)
                return NULL;
        gmap->mm = mm;
        spin_lock(&mm->context.lock);
        list_add_rcu(&gmap->list, &mm->context.gmap_list);
        if (list_is_singular(&mm->context.gmap_list))
                gmap_asce = gmap->asce;
        else
                gmap_asce = -1UL;
        WRITE_ONCE(mm->context.gmap_asce, gmap_asce);
        spin_unlock(&mm->context.lock);
        return gmap;
}
EXPORT_SYMBOL_GPL(gmap_create);

static void gmap_flush_tlb(struct gmap *gmap)
{
        if (MACHINE_HAS_IDTE)
                __tlb_flush_idte(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 __rcu **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);
}

static void gmap_rmap_radix_tree_free(struct radix_tree_root *root)
{
        struct gmap_rmap *rmap, *rnext, *head;
        struct radix_tree_iter iter;
        unsigned long indices[16];
        unsigned long index;
        void __rcu **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];
                        head = radix_tree_delete(root, index);
                        gmap_for_each_rmap_safe(rmap, rnext, head)
                                kfree(rmap);
                }
        } while (nr > 0);
}

/**
 * gmap_free - free a guest address space
 * @gmap: pointer to the guest address space structure
 *
 * No locks required. There are no references to this gmap anymore.
 */
static void gmap_free(struct gmap *gmap)
{
        struct page *page, *next;

        /* Flush tlb of all gmaps (if not already done for shadows) */
        if (!(gmap_is_shadow(gmap) && gmap->removed))
                gmap_flush_tlb(gmap);
        /* Free all segment & region tables. */
        list_for_each_entry_safe(page, next, &gmap->crst_list, lru)
                __free_pages(page, CRST_ALLOC_ORDER);
        gmap_radix_tree_free(&gmap->guest_to_host);
        gmap_radix_tree_free(&gmap->host_to_guest);

        /* Free additional data for a shadow gmap */
        if (gmap_is_shadow(gmap)) {
                struct ptdesc *ptdesc, *n;

                /* Free all page tables. */
                list_for_each_entry_safe(ptdesc, n, &gmap->pt_list, pt_list)
                        page_table_free_pgste(ptdesc);
                gmap_rmap_radix_tree_free(&gmap->host_to_rmap);
                /* Release reference to the parent */
                gmap_put(gmap->parent);
        }

        kfree(gmap);
}

/**
 * gmap_get - increase reference counter for guest address space
 * @gmap: pointer to the guest address space structure
 *
 * Returns the gmap pointer
 */
struct gmap *gmap_get(struct gmap *gmap)
{
        refcount_inc(&gmap->ref_count);
        return gmap;
}
EXPORT_SYMBOL_GPL(gmap_get);

/**
 * gmap_put - decrease reference counter for guest address space
 * @gmap: pointer to the guest address space structure
 *
 * If the reference counter reaches zero the guest address space is freed.
 */
void gmap_put(struct gmap *gmap)
{
        if (refcount_dec_and_test(&gmap->ref_count))
                gmap_free(gmap);
}
EXPORT_SYMBOL_GPL(gmap_put);

/**
 * gmap_remove - remove a guest address space but do not free it yet
 * @gmap: pointer to the guest address space structure
 */
void gmap_remove(struct gmap *gmap)
{
        struct gmap *sg, *next;
        unsigned long gmap_asce;

        /* Remove all shadow gmaps linked to this gmap */
        if (!list_empty(&gmap->children)) {
                spin_lock(&gmap->shadow_lock);
                list_for_each_entry_safe(sg, next, &gmap->children, list) {
                        list_del(&sg->list);
                        gmap_put(sg);
                }
                spin_unlock(&gmap->shadow_lock);
        }
        /* Remove gmap from the pre-mm list */
        spin_lock(&gmap->mm->context.lock);
        list_del_rcu(&gmap->list);
        if (list_empty(&gmap->mm->context.gmap_list))
                gmap_asce = 0;
        else if (list_is_singular(&gmap->mm->context.gmap_list))
                gmap_asce = list_first_entry(&gmap->mm->context.gmap_list,
                                             struct gmap, list)->asce;
        else
                gmap_asce = -1UL;
        WRITE_ONCE(gmap->mm->context.gmap_asce, gmap_asce);
        spin_unlock(&gmap->mm->context.lock);
        synchronize_rcu();
        /* Put reference */
        gmap_put(gmap);
}
EXPORT_SYMBOL_GPL(gmap_remove);

/**
 * 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_get_enabled - get a pointer to the currently enabled gmap
 *
 * Returns a pointer to the currently enabled gmap. 0 if none is enabled.
 */
struct gmap *gmap_get_enabled(void)
{
        return (struct gmap *) S390_lowcore.gmap;
}
EXPORT_SYMBOL_GPL(gmap_get_enabled);

/*
 * gmap_alloc_table is assumed to be called with mmap_lock 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 = gmap_alloc_crst();
        if (!page)
                return -ENOMEM;
        new = page_to_virt(page);
        crst_table_init(new, init);
        spin_lock(&gmap->guest_table_lock);
        if (*table & _REGION_ENTRY_INVALID) {
                list_add(&page->lru, &gmap->crst_list);
                *table = __pa(new) | _REGION_ENTRY_LENGTH |
                        (*table & _REGION_ENTRY_TYPE_MASK);
                page->index = gaddr;
                page = NULL;
        }
        spin_unlock(&gmap->guest_table_lock);
        if (page)
                __free_pages(page, CRST_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;

        offset = (unsigned long) entry / sizeof(unsigned long);
        offset = (offset & (PTRS_PER_PMD - 1)) * PMD_SIZE;
        page = pmd_pgtable_page((pmd_t *) entry);
        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;

        BUG_ON(gmap_is_shadow(gmap));
        spin_lock(&gmap->guest_table_lock);
        entry = radix_tree_delete(&gmap->host_to_guest, vmaddr >> PMD_SHIFT);
        if (entry) {
                flush = (*entry != _SEGMENT_ENTRY_EMPTY);
                *entry = _SEGMENT_ENTRY_EMPTY;
        }
        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;

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

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

/**
 * gmap_map_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;

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

        flush = 0;
        mmap_write_lock(gmap->mm);
        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;
        }
        mmap_write_unlock(gmap->mm);
        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_lock of the mm that belongs to the address space must be held
 * when this function gets called.
 *
 * Note: Can also be called for shadow gmaps.
 */
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);
        /* Note: guest_to_host is empty for a shadow gmap */
        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;

        mmap_read_lock(gmap->mm);
        rc = __gmap_translate(gmap, gaddr);
        mmap_read_unlock(gmap->mm);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_translate);

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

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

static void gmap_pmdp_xchg(struct gmap *gmap, pmd_t *old, pmd_t new,
                           unsigned long gaddr);

/**
 * __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_lock 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;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;
        u64 unprot;
        int rc;

        BUG_ON(gmap_is_shadow(gmap));
        /* Create higher level tables in the gmap page table */
        table = gmap->table;
        if ((gmap->asce & _ASCE_TYPE_MASK) >= _ASCE_TYPE_REGION1) {
                table += (gaddr & _REGION1_INDEX) >> _REGION1_SHIFT;
                if ((*table & _REGION_ENTRY_INVALID) &&
                    gmap_alloc_table(gmap, table, _REGION2_ENTRY_EMPTY,
                                     gaddr & _REGION1_MASK))
                        return -ENOMEM;
                table = __va(*table & _REGION_ENTRY_ORIGIN);
        }
        if ((gmap->asce & _ASCE_TYPE_MASK) >= _ASCE_TYPE_REGION2) {
                table += (gaddr & _REGION2_INDEX) >> _REGION2_SHIFT;
                if ((*table & _REGION_ENTRY_INVALID) &&
                    gmap_alloc_table(gmap, table, _REGION3_ENTRY_EMPTY,
                                     gaddr & _REGION2_MASK))
                        return -ENOMEM;
                table = __va(*table & _REGION_ENTRY_ORIGIN);
        }
        if ((gmap->asce & _ASCE_TYPE_MASK) >= _ASCE_TYPE_REGION3) {
                table += (gaddr & _REGION3_INDEX) >> _REGION3_SHIFT;
                if ((*table & _REGION_ENTRY_INVALID) &&
                    gmap_alloc_table(gmap, table, _SEGMENT_ENTRY_EMPTY,
                                     gaddr & _REGION3_MASK))
                        return -ENOMEM;
                table = __va(*table & _REGION_ENTRY_ORIGIN);
        }
        table += (gaddr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
        /* Walk the parent mm page table */
        mm = gmap->mm;
        pgd = pgd_offset(mm, vmaddr);
        VM_BUG_ON(pgd_none(*pgd));
        p4d = p4d_offset(pgd, vmaddr);
        VM_BUG_ON(p4d_none(*p4d));
        pud = pud_offset(p4d, vmaddr);
        VM_BUG_ON(pud_none(*pud));
        /* large puds cannot yet be handled */
        if (pud_leaf(*pud))
                return -EFAULT;
        pmd = pmd_offset(pud, vmaddr);
        VM_BUG_ON(pmd_none(*pmd));
        /* Are we allowed to use huge pages? */
        if (pmd_leaf(*pmd) && !gmap->mm->context.allow_gmap_hpage_1m)
                return -EFAULT;
        /* Link gmap segment table entry location to page table. */
        rc = radix_tree_preload(GFP_KERNEL_ACCOUNT);
        if (rc)
                return rc;
        ptl = pmd_lock(mm, pmd);
        spin_lock(&gmap->guest_table_lock);
        if (*table == _SEGMENT_ENTRY_EMPTY) {
                rc = radix_tree_insert(&gmap->host_to_guest,
                                       vmaddr >> PMD_SHIFT, table);
                if (!rc) {
                        if (pmd_leaf(*pmd)) {
                                *table = (pmd_val(*pmd) &
                                          _SEGMENT_ENTRY_HARDWARE_BITS_LARGE)
                                        | _SEGMENT_ENTRY_GMAP_UC;
                        } else
                                *table = pmd_val(*pmd) &
                                        _SEGMENT_ENTRY_HARDWARE_BITS;
                }
        } else if (*table & _SEGMENT_ENTRY_PROTECT &&
                   !(pmd_val(*pmd) & _SEGMENT_ENTRY_PROTECT)) {
                unprot = (u64)*table;
                unprot &= ~_SEGMENT_ENTRY_PROTECT;
                unprot |= _SEGMENT_ENTRY_GMAP_UC;
                gmap_pmdp_xchg(gmap, (pmd_t *)table, __pmd(unprot), gaddr);
        }
        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;
        bool unlocked;

        mmap_read_lock(gmap->mm);

retry:
        unlocked = false;
        vmaddr = __gmap_translate(gmap, gaddr);
        if (IS_ERR_VALUE(vmaddr)) {
                rc = vmaddr;
                goto out_up;
        }
        if (fixup_user_fault(gmap->mm, vmaddr, fault_flags,
                             &unlocked)) {
                rc = -EFAULT;
                goto out_up;
        }
        /*
         * In the case that fixup_user_fault unlocked the mmap_lock during
         * faultin redo __gmap_translate to not race with a map/unmap_segment.
         */
        if (unlocked)
                goto retry;

        rc = __gmap_link(gmap, gaddr, vmaddr);
out_up:
        mmap_read_unlock(gmap->mm);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_fault);

/*
 * this function is assumed to be called with mmap_lock held
 */
void __gmap_zap(struct gmap *gmap, unsigned long gaddr)
{
        struct vm_area_struct *vma;
        unsigned long vmaddr;
        spinlock_t *ptl;
        pte_t *ptep;

        /* Find the vm address for the guest address */
        vmaddr = (unsigned long) radix_tree_lookup(&gmap->guest_to_host,
                                                   gaddr >> PMD_SHIFT);
        if (vmaddr) {
                vmaddr |= gaddr & ~PMD_MASK;

                vma = vma_lookup(gmap->mm, vmaddr);
                if (!vma || is_vm_hugetlb_page(vma))
                        return;

                /* Get pointer to the page table entry */
                ptep = get_locked_pte(gmap->mm, vmaddr, &ptl);
                if (likely(ptep)) {
                        ptep_zap_unused(gmap->mm, vmaddr, ptep, 0);
                        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;

        mmap_read_lock(gmap->mm);
        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);
                if (!vma)
                        continue;
                /*
                 * We do not discard pages that are backed by
                 * hugetlbfs, so we don't have to refault them.
                 */
                if (is_vm_hugetlb_page(vma))
                        continue;
                size = min(to - gaddr, PMD_SIZE - (gaddr & ~PMD_MASK));
                zap_page_range_single(vma, vmaddr, size, NULL);
        }
        mmap_read_unlock(gmap->mm);
}
EXPORT_SYMBOL_GPL(gmap_discard);

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

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

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

/**
 * gmap_call_notifier - call all registered invalidation callbacks
 * @gmap: pointer to guest mapping meta data structure
 * @start: start virtual address in the guest address space
 * @end: end virtual address in the guest address space
 */
static void gmap_call_notifier(struct gmap *gmap, unsigned long start,
                               unsigned long end)
{
        struct gmap_notifier *nb;

        list_for_each_entry(nb, &gmap_notifier_list, list)
                nb->notifier_call(gmap, start, end);
}

/**
 * gmap_table_walk - walk the gmap page tables
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @level: page table level to stop at
 *
 * Returns a table entry pointer for the given guest address and @level
 * @level=0 : returns a pointer to a page table table entry (or NULL)
 * @level=1 : returns a pointer to a segment table entry (or NULL)
 * @level=2 : returns a pointer to a region-3 table entry (or NULL)
 * @level=3 : returns a pointer to a region-2 table entry (or NULL)
 * @level=4 : returns a pointer to a region-1 table entry (or NULL)
 *
 * Returns NULL if the gmap page tables could not be walked to the
 * requested level.
 *
 * Note: Can also be called for shadow gmaps.
 */
static inline unsigned long *gmap_table_walk(struct gmap *gmap,
                                             unsigned long gaddr, int level)
{
        const int asce_type = gmap->asce & _ASCE_TYPE_MASK;
        unsigned long *table = gmap->table;

        if (gmap_is_shadow(gmap) && gmap->removed)
                return NULL;

        if (WARN_ON_ONCE(level > (asce_type >> 2) + 1))
                return NULL;

        if (asce_type != _ASCE_TYPE_REGION1 &&
            gaddr & (-1UL << (31 + (asce_type >> 2) * 11)))
                return NULL;

        switch (asce_type) {
        case _ASCE_TYPE_REGION1:
                table += (gaddr & _REGION1_INDEX) >> _REGION1_SHIFT;
                if (level == 4)
                        break;
                if (*table & _REGION_ENTRY_INVALID)
                        return NULL;
                table = __va(*table & _REGION_ENTRY_ORIGIN);
                fallthrough;
        case _ASCE_TYPE_REGION2:
                table += (gaddr & _REGION2_INDEX) >> _REGION2_SHIFT;
                if (level == 3)
                        break;
                if (*table & _REGION_ENTRY_INVALID)
                        return NULL;
                table = __va(*table & _REGION_ENTRY_ORIGIN);
                fallthrough;
        case _ASCE_TYPE_REGION3:
                table += (gaddr & _REGION3_INDEX) >> _REGION3_SHIFT;
                if (level == 2)
                        break;
                if (*table & _REGION_ENTRY_INVALID)
                        return NULL;
                table = __va(*table & _REGION_ENTRY_ORIGIN);
                fallthrough;
        case _ASCE_TYPE_SEGMENT:
                table += (gaddr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
                if (level == 1)
                        break;
                if (*table & _REGION_ENTRY_INVALID)
                        return NULL;
                table = __va(*table & _SEGMENT_ENTRY_ORIGIN);
                table += (gaddr & _PAGE_INDEX) >> _PAGE_SHIFT;
        }
        return table;
}

/**
 * gmap_pte_op_walk - walk the gmap page table, get the page table lock
 *                    and return the pte pointer
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @ptl: pointer to the spinlock pointer
 *
 * Returns a pointer to the locked pte for a guest address, or NULL
 */
static pte_t *gmap_pte_op_walk(struct gmap *gmap, unsigned long gaddr,
                               spinlock_t **ptl)
{
        unsigned long *table;

        BUG_ON(gmap_is_shadow(gmap));
        /* Walk the gmap page table, lock and get pte pointer */
        table = gmap_table_walk(gmap, gaddr, 1); /* get segment pointer */
        if (!table || *table & _SEGMENT_ENTRY_INVALID)
                return NULL;
        return pte_alloc_map_lock(gmap->mm, (pmd_t *) table, gaddr, ptl);
}

/**
 * gmap_pte_op_fixup - force a page in and connect the gmap page table
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @vmaddr: address in the host process address space
 * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
 *
 * Returns 0 if the caller can retry __gmap_translate (might fail again),
 * -ENOMEM if out of memory and -EFAULT if anything goes wrong while fixing
 * up or connecting the gmap page table.
 */
static int gmap_pte_op_fixup(struct gmap *gmap, unsigned long gaddr,
                             unsigned long vmaddr, int prot)
{
        struct mm_struct *mm = gmap->mm;
        unsigned int fault_flags;
        bool unlocked = false;

        BUG_ON(gmap_is_shadow(gmap));
        fault_flags = (prot == PROT_WRITE) ? FAULT_FLAG_WRITE : 0;
        if (fixup_user_fault(mm, vmaddr, fault_flags, &unlocked))
                return -EFAULT;
        if (unlocked)
                /* lost mmap_lock, caller has to retry __gmap_translate */
                return 0;
        /* Connect the page tables */
        return __gmap_link(gmap, gaddr, vmaddr);
}

/**
 * gmap_pte_op_end - release the page table lock
 * @ptep: pointer to the locked pte
 * @ptl: pointer to the page table spinlock
 */
static void gmap_pte_op_end(pte_t *ptep, spinlock_t *ptl)
{
        pte_unmap_unlock(ptep, ptl);
}

/**
 * gmap_pmd_op_walk - walk the gmap tables, get the guest table lock
 *                    and return the pmd pointer
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 *
 * Returns a pointer to the pmd for a guest address, or NULL
 */
static inline pmd_t *gmap_pmd_op_walk(struct gmap *gmap, unsigned long gaddr)
{
        pmd_t *pmdp;

        BUG_ON(gmap_is_shadow(gmap));
        pmdp = (pmd_t *) gmap_table_walk(gmap, gaddr, 1);
        if (!pmdp)
                return NULL;

        /* without huge pages, there is no need to take the table lock */
        if (!gmap->mm->context.allow_gmap_hpage_1m)
                return pmd_none(*pmdp) ? NULL : pmdp;

        spin_lock(&gmap->guest_table_lock);
        if (pmd_none(*pmdp)) {
                spin_unlock(&gmap->guest_table_lock);
                return NULL;
        }

        /* 4k page table entries are locked via the pte (pte_alloc_map_lock). */
        if (!pmd_leaf(*pmdp))
                spin_unlock(&gmap->guest_table_lock);
        return pmdp;
}

/**
 * gmap_pmd_op_end - release the guest_table_lock if needed
 * @gmap: pointer to the guest mapping meta data structure
 * @pmdp: pointer to the pmd
 */
static inline void gmap_pmd_op_end(struct gmap *gmap, pmd_t *pmdp)
{
        if (pmd_leaf(*pmdp))
                spin_unlock(&gmap->guest_table_lock);
}

/*
 * gmap_protect_pmd - remove access rights to memory and set pmd notification bits
 * @pmdp: pointer to the pmd to be protected
 * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
 * @bits: notification bits to set
 *
 * Returns:
 * 0 if successfully protected
 * -EAGAIN if a fixup is needed
 * -EINVAL if unsupported notifier bits have been specified
 *
 * Expected to be called with sg->mm->mmap_lock in read and
 * guest_table_lock held.
 */
static int gmap_protect_pmd(struct gmap *gmap, unsigned long gaddr,
                            pmd_t *pmdp, int prot, unsigned long bits)
{
        int pmd_i = pmd_val(*pmdp) & _SEGMENT_ENTRY_INVALID;
        int pmd_p = pmd_val(*pmdp) & _SEGMENT_ENTRY_PROTECT;
        pmd_t new = *pmdp;

        /* Fixup needed */
        if ((pmd_i && (prot != PROT_NONE)) || (pmd_p && (prot == PROT_WRITE)))
                return -EAGAIN;

        if (prot == PROT_NONE && !pmd_i) {
                new = set_pmd_bit(new, __pgprot(_SEGMENT_ENTRY_INVALID));
                gmap_pmdp_xchg(gmap, pmdp, new, gaddr);
        }

        if (prot == PROT_READ && !pmd_p) {
                new = clear_pmd_bit(new, __pgprot(_SEGMENT_ENTRY_INVALID));
                new = set_pmd_bit(new, __pgprot(_SEGMENT_ENTRY_PROTECT));
                gmap_pmdp_xchg(gmap, pmdp, new, gaddr);
        }

        if (bits & GMAP_NOTIFY_MPROT)
                set_pmd(pmdp, set_pmd_bit(*pmdp, __pgprot(_SEGMENT_ENTRY_GMAP_IN)));

        /* Shadow GMAP protection needs split PMDs */
        if (bits & GMAP_NOTIFY_SHADOW)
                return -EINVAL;

        return 0;
}

/*
 * gmap_protect_pte - remove access rights to memory and set pgste bits
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @pmdp: pointer to the pmd associated with the pte
 * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
 * @bits: notification bits to set
 *
 * Returns 0 if successfully protected, -ENOMEM if out of memory and
 * -EAGAIN if a fixup is needed.
 *
 * Expected to be called with sg->mm->mmap_lock in read
 */
static int gmap_protect_pte(struct gmap *gmap, unsigned long gaddr,
                            pmd_t *pmdp, int prot, unsigned long bits)
{
        int rc;
        pte_t *ptep;
        spinlock_t *ptl;
        unsigned long pbits = 0;

        if (pmd_val(*pmdp) & _SEGMENT_ENTRY_INVALID)
                return -EAGAIN;

        ptep = pte_alloc_map_lock(gmap->mm, pmdp, gaddr, &ptl);
        if (!ptep)
                return -ENOMEM;

        pbits |= (bits & GMAP_NOTIFY_MPROT) ? PGSTE_IN_BIT : 0;
        pbits |= (bits & GMAP_NOTIFY_SHADOW) ? PGSTE_VSIE_BIT : 0;
        /* Protect and unlock. */
        rc = ptep_force_prot(gmap->mm, gaddr, ptep, prot, pbits);
        gmap_pte_op_end(ptep, ptl);
        return rc;
}

/*
 * gmap_protect_range - remove access rights to memory and set pgste bits
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @len: size of area
 * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
 * @bits: pgste notification bits to set
 *
 * Returns 0 if successfully protected, -ENOMEM if out of memory and
 * -EFAULT if gaddr is invalid (or mapping for shadows is missing).
 *
 * Called with sg->mm->mmap_lock in read.
 */
static int gmap_protect_range(struct gmap *gmap, unsigned long gaddr,
                              unsigned long len, int prot, unsigned long bits)
{
        unsigned long vmaddr, dist;
        pmd_t *pmdp;
        int rc;

        BUG_ON(gmap_is_shadow(gmap));
        while (len) {
                rc = -EAGAIN;
                pmdp = gmap_pmd_op_walk(gmap, gaddr);
                if (pmdp) {
                        if (!pmd_leaf(*pmdp)) {
                                rc = gmap_protect_pte(gmap, gaddr, pmdp, prot,
                                                      bits);
                                if (!rc) {
                                        len -= PAGE_SIZE;
                                        gaddr += PAGE_SIZE;
                                }
                        } else {
                                rc = gmap_protect_pmd(gmap, gaddr, pmdp, prot,
                                                      bits);
                                if (!rc) {
                                        dist = HPAGE_SIZE - (gaddr & ~HPAGE_MASK);
                                        len = len < dist ? 0 : len - dist;
                                        gaddr = (gaddr & HPAGE_MASK) + HPAGE_SIZE;
                                }
                        }
                        gmap_pmd_op_end(gmap, pmdp);
                }
                if (rc) {
                        if (rc == -EINVAL)
                                return rc;

                        /* -EAGAIN, fixup of userspace mm and gmap */
                        vmaddr = __gmap_translate(gmap, gaddr);
                        if (IS_ERR_VALUE(vmaddr))
                                return vmaddr;
                        rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr, prot);
                        if (rc)
                                return rc;
                }
        }
        return 0;
}

/**
 * gmap_mprotect_notify - change access rights for a range of ptes and
 *                        call the notifier if any pte changes again
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @len: size of area
 * @prot: indicates access rights: PROT_NONE, PROT_READ or PROT_WRITE
 *
 * Returns 0 if for each page in the given range a gmap mapping exists,
 * the new access rights could be set and the notifier could be armed.
 * 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_mprotect_notify(struct gmap *gmap, unsigned long gaddr,
                         unsigned long len, int prot)
{
        int rc;

        if ((gaddr & ~PAGE_MASK) || (len & ~PAGE_MASK) || gmap_is_shadow(gmap))
                return -EINVAL;
        if (!MACHINE_HAS_ESOP && prot == PROT_READ)
                return -EINVAL;
        mmap_read_lock(gmap->mm);
        rc = gmap_protect_range(gmap, gaddr, len, prot, GMAP_NOTIFY_MPROT);
        mmap_read_unlock(gmap->mm);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_mprotect_notify);

/**
 * gmap_read_table - get an unsigned long value from a guest page table using
 *                   absolute addressing, without marking the page referenced.
 * @gmap: pointer to guest mapping meta data structure
 * @gaddr: virtual address in the guest address space
 * @val: pointer to the unsigned long value to return
 *
 * Returns 0 if the value was read, -ENOMEM if out of memory and -EFAULT
 * if reading using the virtual address failed. -EINVAL if called on a gmap
 * shadow.
 *
 * Called with gmap->mm->mmap_lock in read.
 */
int gmap_read_table(struct gmap *gmap, unsigned long gaddr, unsigned long *val)
{
        unsigned long address, vmaddr;
        spinlock_t *ptl;
        pte_t *ptep, pte;
        int rc;

        if (gmap_is_shadow(gmap))
                return -EINVAL;

        while (1) {
                rc = -EAGAIN;
                ptep = gmap_pte_op_walk(gmap, gaddr, &ptl);
                if (ptep) {
                        pte = *ptep;
                        if (pte_present(pte) && (pte_val(pte) & _PAGE_READ)) {
                                address = pte_val(pte) & PAGE_MASK;
                                address += gaddr & ~PAGE_MASK;
                                *val = *(unsigned long *)__va(address);
                                set_pte(ptep, set_pte_bit(*ptep, __pgprot(_PAGE_YOUNG)));
                                /* Do *NOT* clear the _PAGE_INVALID bit! */
                                rc = 0;
                        }
                        gmap_pte_op_end(ptep, ptl);
                }
                if (!rc)
                        break;
                vmaddr = __gmap_translate(gmap, gaddr);
                if (IS_ERR_VALUE(vmaddr)) {
                        rc = vmaddr;
                        break;
                }
                rc = gmap_pte_op_fixup(gmap, gaddr, vmaddr, PROT_READ);
                if (rc)
                        break;
        }
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_read_table);

/**
 * gmap_insert_rmap - add a rmap to the host_to_rmap radix tree
 * @sg: pointer to the shadow guest address space structure
 * @vmaddr: vm address associated with the rmap
 * @rmap: pointer to the rmap structure
 *
 * Called with the sg->guest_table_lock
 */
static inline void gmap_insert_rmap(struct gmap *sg, unsigned long vmaddr,
                                    struct gmap_rmap *rmap)
{
        struct gmap_rmap *temp;
        void __rcu **slot;

        BUG_ON(!gmap_is_shadow(sg));
        slot = radix_tree_lookup_slot(&sg->host_to_rmap, vmaddr >> PAGE_SHIFT);
        if (slot) {
                rmap->next = radix_tree_deref_slot_protected(slot,
                                                        &sg->guest_table_lock);
                for (temp = rmap->next; temp; temp = temp->next) {
                        if (temp->raddr == rmap->raddr) {
                                kfree(rmap);
                                return;
                        }
                }
                radix_tree_replace_slot(&sg->host_to_rmap, slot, rmap);
        } else {
                rmap->next = NULL;
                radix_tree_insert(&sg->host_to_rmap, vmaddr >> PAGE_SHIFT,
                                  rmap);
        }
}

/**
 * gmap_protect_rmap - restrict access rights to memory (RO) and create an rmap
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow gmap
 * @paddr: address in the parent guest address space
 * @len: length of the memory area to protect
 *
 * Returns 0 if successfully protected and the rmap was created, -ENOMEM
 * if out of memory and -EFAULT if paddr is invalid.
 */
static int gmap_protect_rmap(struct gmap *sg, unsigned long raddr,
                             unsigned long paddr, unsigned long len)
{
        struct gmap *parent;
        struct gmap_rmap *rmap;
        unsigned long vmaddr;
        spinlock_t *ptl;
        pte_t *ptep;
        int rc;

        BUG_ON(!gmap_is_shadow(sg));
        parent = sg->parent;
        while (len) {
                vmaddr = __gmap_translate(parent, paddr);
                if (IS_ERR_VALUE(vmaddr))
                        return vmaddr;
                rmap = kzalloc(sizeof(*rmap), GFP_KERNEL_ACCOUNT);
                if (!rmap)
                        return -ENOMEM;
                rmap->raddr = raddr;
                rc = radix_tree_preload(GFP_KERNEL_ACCOUNT);
                if (rc) {
                        kfree(rmap);
                        return rc;
                }
                rc = -EAGAIN;
                ptep = gmap_pte_op_walk(parent, paddr, &ptl);
                if (ptep) {
                        spin_lock(&sg->guest_table_lock);
                        rc = ptep_force_prot(parent->mm, paddr, ptep, PROT_READ,
                                             PGSTE_VSIE_BIT);
                        if (!rc)
                                gmap_insert_rmap(sg, vmaddr, rmap);
                        spin_unlock(&sg->guest_table_lock);
                        gmap_pte_op_end(ptep, ptl);
                }
                radix_tree_preload_end();
                if (rc) {
                        kfree(rmap);
                        rc = gmap_pte_op_fixup(parent, paddr, vmaddr, PROT_READ);
                        if (rc)
                                return rc;
                        continue;
                }
                paddr += PAGE_SIZE;
                len -= PAGE_SIZE;
        }
        return 0;
}

#define _SHADOW_RMAP_MASK       0x7
#define _SHADOW_RMAP_REGION1    0x5
#define _SHADOW_RMAP_REGION2    0x4
#define _SHADOW_RMAP_REGION3    0x3
#define _SHADOW_RMAP_SEGMENT    0x2
#define _SHADOW_RMAP_PGTABLE    0x1

/**
 * gmap_idte_one - invalidate a single region or segment table entry
 * @asce: region or segment table *origin* + table-type bits
 * @vaddr: virtual address to identify the table entry to flush
 *
 * The invalid bit of a single region or segment table entry is set
 * and the associated TLB entries depending on the entry are flushed.
 * The table-type of the @asce identifies the portion of the @vaddr
 * that is used as the invalidation index.
 */
static inline void gmap_idte_one(unsigned long asce, unsigned long vaddr)
{
        asm volatile(
                "       idte    %0,0,%1"
                : : "a" (asce), "a" (vaddr) : "cc", "memory");
}

/**
 * gmap_unshadow_page - remove a page from a shadow page table
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 *
 * Called with the sg->guest_table_lock
 */
static void gmap_unshadow_page(struct gmap *sg, unsigned long raddr)
{
        unsigned long *table;

        BUG_ON(!gmap_is_shadow(sg));
        table = gmap_table_walk(sg, raddr, 0); /* get page table pointer */
        if (!table || *table & _PAGE_INVALID)
                return;
        gmap_call_notifier(sg, raddr, raddr + _PAGE_SIZE - 1);
        ptep_unshadow_pte(sg->mm, raddr, (pte_t *) table);
}

/**
 * __gmap_unshadow_pgt - remove all entries from a shadow page table
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 * @pgt: pointer to the start of a shadow page table
 *
 * Called with the sg->guest_table_lock
 */
static void __gmap_unshadow_pgt(struct gmap *sg, unsigned long raddr,
                                unsigned long *pgt)
{
        int i;

        BUG_ON(!gmap_is_shadow(sg));
        for (i = 0; i < _PAGE_ENTRIES; i++, raddr += _PAGE_SIZE)
                pgt[i] = _PAGE_INVALID;
}

/**
 * gmap_unshadow_pgt - remove a shadow page table from a segment entry
 * @sg: pointer to the shadow guest address space structure
 * @raddr: address in the shadow guest address space
 *
 * Called with the sg->guest_table_lock
 */
static void gmap_unshadow_pgt(struct gmap *sg, unsigned long raddr)
{
        unsigned long *ste;
        phys_addr_t sto, pgt;
        struct ptdesc *ptdesc;

        BUG_ON(!gmap_is_shadow(sg));
        ste = gmap_table_walk(sg, raddr, 1); /* get segment pointer */
        if (!ste || !(*ste & _SEGMENT_ENTRY_ORIGIN))
                return;
        gmap_call_notifier(sg, raddr, raddr + _SEGMENT_SIZE - 1);
        sto = __pa(ste - ((raddr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT));
        gmap_idte_one(sto | _ASCE_TYPE_SEGMENT, raddr);
        pgt = *ste & _SEGMENT_ENTRY_ORIGIN;
        *ste = _SEGMENT_ENTRY_EMPTY;
        __gmap_unshadow_pgt(sg, raddr, __va(pgt));
        /* Free page table */
        ptdesc = page_ptdesc(phys_to_page(pgt));
        list_del(&ptdesc->pt_list);
        page_table_free_pgste(ptdesc);
}

/**
 * __gmap_unshadow_sgt - remove all entries from a shadow segment table
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 * @sgt: pointer to the start of a shadow segment table
 *
 * Called with the sg->guest_table_lock
 */
static void __gmap_unshadow_sgt(struct gmap *sg, unsigned long raddr,
                                unsigned long *sgt)
{
        struct ptdesc *ptdesc;
        phys_addr_t pgt;
        int i;

        BUG_ON(!gmap_is_shadow(sg));
        for (i = 0; i < _CRST_ENTRIES; i++, raddr += _SEGMENT_SIZE) {
                if (!(sgt[i] & _SEGMENT_ENTRY_ORIGIN))
                        continue;
                pgt = sgt[i] & _REGION_ENTRY_ORIGIN;
                sgt[i] = _SEGMENT_ENTRY_EMPTY;
                __gmap_unshadow_pgt(sg, raddr, __va(pgt));
                /* Free page table */
                ptdesc = page_ptdesc(phys_to_page(pgt));
                list_del(&ptdesc->pt_list);
                page_table_free_pgste(ptdesc);
        }
}

/**
 * gmap_unshadow_sgt - remove a shadow segment table from a region-3 entry
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 *
 * Called with the shadow->guest_table_lock
 */
static void gmap_unshadow_sgt(struct gmap *sg, unsigned long raddr)
{
        unsigned long r3o, *r3e;
        phys_addr_t sgt;
        struct page *page;

        BUG_ON(!gmap_is_shadow(sg));
        r3e = gmap_table_walk(sg, raddr, 2); /* get region-3 pointer */
        if (!r3e || !(*r3e & _REGION_ENTRY_ORIGIN))
                return;
        gmap_call_notifier(sg, raddr, raddr + _REGION3_SIZE - 1);
        r3o = (unsigned long) (r3e - ((raddr & _REGION3_INDEX) >> _REGION3_SHIFT));
        gmap_idte_one(__pa(r3o) | _ASCE_TYPE_REGION3, raddr);
        sgt = *r3e & _REGION_ENTRY_ORIGIN;
        *r3e = _REGION3_ENTRY_EMPTY;
        __gmap_unshadow_sgt(sg, raddr, __va(sgt));
        /* Free segment table */
        page = phys_to_page(sgt);
        list_del(&page->lru);
        __free_pages(page, CRST_ALLOC_ORDER);
}

/**
 * __gmap_unshadow_r3t - remove all entries from a shadow region-3 table
 * @sg: pointer to the shadow guest address space structure
 * @raddr: address in the shadow guest address space
 * @r3t: pointer to the start of a shadow region-3 table
 *
 * Called with the sg->guest_table_lock
 */
static void __gmap_unshadow_r3t(struct gmap *sg, unsigned long raddr,
                                unsigned long *r3t)
{
        struct page *page;
        phys_addr_t sgt;
        int i;

        BUG_ON(!gmap_is_shadow(sg));
        for (i = 0; i < _CRST_ENTRIES; i++, raddr += _REGION3_SIZE) {
                if (!(r3t[i] & _REGION_ENTRY_ORIGIN))
                        continue;
                sgt = r3t[i] & _REGION_ENTRY_ORIGIN;
                r3t[i] = _REGION3_ENTRY_EMPTY;
                __gmap_unshadow_sgt(sg, raddr, __va(sgt));
                /* Free segment table */
                page = phys_to_page(sgt);
                list_del(&page->lru);
                __free_pages(page, CRST_ALLOC_ORDER);
        }
}

/**
 * gmap_unshadow_r3t - remove a shadow region-3 table from a region-2 entry
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 *
 * Called with the sg->guest_table_lock
 */
static void gmap_unshadow_r3t(struct gmap *sg, unsigned long raddr)
{
        unsigned long r2o, *r2e;
        phys_addr_t r3t;
        struct page *page;

        BUG_ON(!gmap_is_shadow(sg));
        r2e = gmap_table_walk(sg, raddr, 3); /* get region-2 pointer */
        if (!r2e || !(*r2e & _REGION_ENTRY_ORIGIN))
                return;
        gmap_call_notifier(sg, raddr, raddr + _REGION2_SIZE - 1);
        r2o = (unsigned long) (r2e - ((raddr & _REGION2_INDEX) >> _REGION2_SHIFT));
        gmap_idte_one(__pa(r2o) | _ASCE_TYPE_REGION2, raddr);
        r3t = *r2e & _REGION_ENTRY_ORIGIN;
        *r2e = _REGION2_ENTRY_EMPTY;
        __gmap_unshadow_r3t(sg, raddr, __va(r3t));
        /* Free region 3 table */
        page = phys_to_page(r3t);
        list_del(&page->lru);
        __free_pages(page, CRST_ALLOC_ORDER);
}

/**
 * __gmap_unshadow_r2t - remove all entries from a shadow region-2 table
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 * @r2t: pointer to the start of a shadow region-2 table
 *
 * Called with the sg->guest_table_lock
 */
static void __gmap_unshadow_r2t(struct gmap *sg, unsigned long raddr,
                                unsigned long *r2t)
{
        phys_addr_t r3t;
        struct page *page;
        int i;

        BUG_ON(!gmap_is_shadow(sg));
        for (i = 0; i < _CRST_ENTRIES; i++, raddr += _REGION2_SIZE) {
                if (!(r2t[i] & _REGION_ENTRY_ORIGIN))
                        continue;
                r3t = r2t[i] & _REGION_ENTRY_ORIGIN;
                r2t[i] = _REGION2_ENTRY_EMPTY;
                __gmap_unshadow_r3t(sg, raddr, __va(r3t));
                /* Free region 3 table */
                page = phys_to_page(r3t);
                list_del(&page->lru);
                __free_pages(page, CRST_ALLOC_ORDER);
        }
}

/**
 * gmap_unshadow_r2t - remove a shadow region-2 table from a region-1 entry
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 *
 * Called with the sg->guest_table_lock
 */
static void gmap_unshadow_r2t(struct gmap *sg, unsigned long raddr)
{
        unsigned long r1o, *r1e;
        struct page *page;
        phys_addr_t r2t;

        BUG_ON(!gmap_is_shadow(sg));
        r1e = gmap_table_walk(sg, raddr, 4); /* get region-1 pointer */
        if (!r1e || !(*r1e & _REGION_ENTRY_ORIGIN))
                return;
        gmap_call_notifier(sg, raddr, raddr + _REGION1_SIZE - 1);
        r1o = (unsigned long) (r1e - ((raddr & _REGION1_INDEX) >> _REGION1_SHIFT));
        gmap_idte_one(__pa(r1o) | _ASCE_TYPE_REGION1, raddr);
        r2t = *r1e & _REGION_ENTRY_ORIGIN;
        *r1e = _REGION1_ENTRY_EMPTY;
        __gmap_unshadow_r2t(sg, raddr, __va(r2t));
        /* Free region 2 table */
        page = phys_to_page(r2t);
        list_del(&page->lru);
        __free_pages(page, CRST_ALLOC_ORDER);
}

/**
 * __gmap_unshadow_r1t - remove all entries from a shadow region-1 table
 * @sg: pointer to the shadow guest address space structure
 * @raddr: rmap address in the shadow guest address space
 * @r1t: pointer to the start of a shadow region-1 table
 *
 * Called with the shadow->guest_table_lock
 */
static void __gmap_unshadow_r1t(struct gmap *sg, unsigned long raddr,
                                unsigned long *r1t)
{
        unsigned long asce;
        struct page *page;
        phys_addr_t r2t;
        int i;

        BUG_ON(!gmap_is_shadow(sg));
        asce = __pa(r1t) | _ASCE_TYPE_REGION1;
        for (i = 0; i < _CRST_ENTRIES; i++, raddr += _REGION1_SIZE) {
                if (!(r1t[i] & _REGION_ENTRY_ORIGIN))
                        continue;
                r2t = r1t[i] & _REGION_ENTRY_ORIGIN;
                __gmap_unshadow_r2t(sg, raddr, __va(r2t));
                /* Clear entry and flush translation r1t -> r2t */
                gmap_idte_one(asce, raddr);
                r1t[i] = _REGION1_ENTRY_EMPTY;
                /* Free region 2 table */
                page = phys_to_page(r2t);
                list_del(&page->lru);
                __free_pages(page, CRST_ALLOC_ORDER);
        }
}

/**
 * gmap_unshadow - remove a shadow page table completely
 * @sg: pointer to the shadow guest address space structure
 *
 * Called with sg->guest_table_lock
 */
static void gmap_unshadow(struct gmap *sg)
{
        unsigned long *table;

        BUG_ON(!gmap_is_shadow(sg));
        if (sg->removed)
                return;
        sg->removed = 1;
        gmap_call_notifier(sg, 0, -1UL);
        gmap_flush_tlb(sg);
        table = __va(sg->asce & _ASCE_ORIGIN);
        switch (sg->asce & _ASCE_TYPE_MASK) {
        case _ASCE_TYPE_REGION1:
                __gmap_unshadow_r1t(sg, 0, table);
                break;
        case _ASCE_TYPE_REGION2:
                __gmap_unshadow_r2t(sg, 0, table);
                break;
        case _ASCE_TYPE_REGION3:
                __gmap_unshadow_r3t(sg, 0, table);
                break;
        case _ASCE_TYPE_SEGMENT:
                __gmap_unshadow_sgt(sg, 0, table);
                break;
        }
}

/**
 * gmap_find_shadow - find a specific asce in the list of shadow tables
 * @parent: pointer to the parent gmap
 * @asce: ASCE for which the shadow table is created
 * @edat_level: edat level to be used for the shadow translation
 *
 * Returns the pointer to a gmap if a shadow table with the given asce is
 * already available, ERR_PTR(-EAGAIN) if another one is just being created,
 * otherwise NULL
 */
static struct gmap *gmap_find_shadow(struct gmap *parent, unsigned long asce,
                                     int edat_level)
{
        struct gmap *sg;

        list_for_each_entry(sg, &parent->children, list) {
                if (sg->orig_asce != asce || sg->edat_level != edat_level ||
                    sg->removed)
                        continue;
                if (!sg->initialized)
                        return ERR_PTR(-EAGAIN);
                refcount_inc(&sg->ref_count);
                return sg;
        }
        return NULL;
}

/**
 * gmap_shadow_valid - check if a shadow guest address space matches the
 *                     given properties and is still valid
 * @sg: pointer to the shadow guest address space structure
 * @asce: ASCE for which the shadow table is requested
 * @edat_level: edat level to be used for the shadow translation
 *
 * Returns 1 if the gmap shadow is still valid and matches the given
 * properties, the caller can continue using it. Returns 0 otherwise, the
 * caller has to request a new shadow gmap in this case.
 *
 */
int gmap_shadow_valid(struct gmap *sg, unsigned long asce, int edat_level)
{
        if (sg->removed)
                return 0;
        return sg->orig_asce == asce && sg->edat_level == edat_level;
}
EXPORT_SYMBOL_GPL(gmap_shadow_valid);

/**
 * gmap_shadow - create/find a shadow guest address space
 * @parent: pointer to the parent gmap
 * @asce: ASCE for which the shadow table is created
 * @edat_level: edat level to be used for the shadow translation
 *
 * The pages of the top level page table referred by the asce parameter
 * will be set to read-only and marked in the PGSTEs of the kvm process.
 * The shadow table will be removed automatically on any change to the
 * PTE mapping for the source table.
 *
 * Returns a guest address space structure, ERR_PTR(-ENOMEM) if out of memory,
 * ERR_PTR(-EAGAIN) if the caller has to retry and ERR_PTR(-EFAULT) if the
 * parent gmap table could not be protected.
 */
struct gmap *gmap_shadow(struct gmap *parent, unsigned long asce,
                         int edat_level)
{
        struct gmap *sg, *new;
        unsigned long limit;
        int rc;

        BUG_ON(parent->mm->context.allow_gmap_hpage_1m);
        BUG_ON(gmap_is_shadow(parent));
        spin_lock(&parent->shadow_lock);
        sg = gmap_find_shadow(parent, asce, edat_level);
        spin_unlock(&parent->shadow_lock);
        if (sg)
                return sg;
        /* Create a new shadow gmap */
        limit = -1UL >> (33 - (((asce & _ASCE_TYPE_MASK) >> 2) * 11));
        if (asce & _ASCE_REAL_SPACE)
                limit = -1UL;
        new = gmap_alloc(limit);
        if (!new)
                return ERR_PTR(-ENOMEM);
        new->mm = parent->mm;
        new->parent = gmap_get(parent);
        new->private = parent->private;
        new->orig_asce = asce;
        new->edat_level = edat_level;
        new->initialized = false;
        spin_lock(&parent->shadow_lock);
        /* Recheck if another CPU created the same shadow */
        sg = gmap_find_shadow(parent, asce, edat_level);
        if (sg) {
                spin_unlock(&parent->shadow_lock);
                gmap_free(new);
                return sg;
        }
        if (asce & _ASCE_REAL_SPACE) {
                /* only allow one real-space gmap shadow */
                list_for_each_entry(sg, &parent->children, list) {
                        if (sg->orig_asce & _ASCE_REAL_SPACE) {
                                spin_lock(&sg->guest_table_lock);
                                gmap_unshadow(sg);
                                spin_unlock(&sg->guest_table_lock);
                                list_del(&sg->list);
                                gmap_put(sg);
                                break;
                        }
                }
        }
        refcount_set(&new->ref_count, 2);
        list_add(&new->list, &parent->children);
        if (asce & _ASCE_REAL_SPACE) {
                /* nothing to protect, return right away */
                new->initialized = true;
                spin_unlock(&parent->shadow_lock);
                return new;
        }
        spin_unlock(&parent->shadow_lock);
        /* protect after insertion, so it will get properly invalidated */
        mmap_read_lock(parent->mm);
        rc = gmap_protect_range(parent, asce & _ASCE_ORIGIN,
                                ((asce & _ASCE_TABLE_LENGTH) + 1) * PAGE_SIZE,
                                PROT_READ, GMAP_NOTIFY_SHADOW);
        mmap_read_unlock(parent->mm);
        spin_lock(&parent->shadow_lock);
        new->initialized = true;
        if (rc) {
                list_del(&new->list);
                gmap_free(new);
                new = ERR_PTR(rc);
        }
        spin_unlock(&parent->shadow_lock);
        return new;
}
EXPORT_SYMBOL_GPL(gmap_shadow);

/**
 * gmap_shadow_r2t - create an empty shadow region 2 table
 * @sg: pointer to the shadow guest address space structure
 * @saddr: faulting address in the shadow gmap
 * @r2t: parent gmap address of the region 2 table to get shadowed
 * @fake: r2t references contiguous guest memory block, not a r2t
 *
 * The r2t parameter specifies the address of the source table. The
 * four pages of the source table are made read-only in the parent gmap
 * address space. A write to the source table area @r2t will automatically
 * remove the shadow r2 table and all of its descendants.
 *
 * Returns 0 if successfully shadowed or already shadowed, -EAGAIN if the
 * shadow table structure is incomplete, -ENOMEM if out of memory and
 * -EFAULT if an address in the parent gmap could not be resolved.
 *
 * Called with sg->mm->mmap_lock in read.
 */
int gmap_shadow_r2t(struct gmap *sg, unsigned long saddr, unsigned long r2t,
                    int fake)
{
        unsigned long raddr, origin, offset, len;
        unsigned long *table;
        phys_addr_t s_r2t;
        struct page *page;
        int rc;

        BUG_ON(!gmap_is_shadow(sg));
        /* Allocate a shadow region second table */
        page = gmap_alloc_crst();
        if (!page)
                return -ENOMEM;
        page->index = r2t & _REGION_ENTRY_ORIGIN;
        if (fake)
                page->index |= GMAP_SHADOW_FAKE_TABLE;
        s_r2t = page_to_phys(page);
        /* Install shadow region second table */
        spin_lock(&sg->guest_table_lock);
        table = gmap_table_walk(sg, saddr, 4); /* get region-1 pointer */
        if (!table) {
                rc = -EAGAIN;           /* Race with unshadow */
                goto out_free;
        }
        if (!(*table & _REGION_ENTRY_INVALID)) {
                rc = 0;                 /* Already established */
                goto out_free;
        } else if (*table & _REGION_ENTRY_ORIGIN) {
                rc = -EAGAIN;           /* Race with shadow */
                goto out_free;
        }
        crst_table_init(__va(s_r2t), _REGION2_ENTRY_EMPTY);
        /* mark as invalid as long as the parent table is not protected */
        *table = s_r2t | _REGION_ENTRY_LENGTH |
                 _REGION_ENTRY_TYPE_R1 | _REGION_ENTRY_INVALID;
        if (sg->edat_level >= 1)
                *table |= (r2t & _REGION_ENTRY_PROTECT);
        list_add(&page->lru, &sg->crst_list);
        if (fake) {
                /* nothing to protect for fake tables */
                *table &= ~_REGION_ENTRY_INVALID;
                spin_unlock(&sg->guest_table_lock);
                return 0;
        }
        spin_unlock(&sg->guest_table_lock);
        /* Make r2t read-only in parent gmap page table */
        raddr = (saddr & _REGION1_MASK) | _SHADOW_RMAP_REGION1;
        origin = r2t & _REGION_ENTRY_ORIGIN;
        offset = ((r2t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
        len = ((r2t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
        rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
        spin_lock(&sg->guest_table_lock);
        if (!rc) {
                table = gmap_table_walk(sg, saddr, 4);
                if (!table || (*table & _REGION_ENTRY_ORIGIN) != s_r2t)
                        rc = -EAGAIN;           /* Race with unshadow */
                else
                        *table &= ~_REGION_ENTRY_INVALID;
        } else {
                gmap_unshadow_r2t(sg, raddr);
        }
        spin_unlock(&sg->guest_table_lock);
        return rc;
out_free:
        spin_unlock(&sg->guest_table_lock);
        __free_pages(page, CRST_ALLOC_ORDER);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_shadow_r2t);

/**
 * gmap_shadow_r3t - create a shadow region 3 table
 * @sg: pointer to the shadow guest address space structure
 * @saddr: faulting address in the shadow gmap
 * @r3t: parent gmap address of the region 3 table to get shadowed
 * @fake: r3t references contiguous guest memory block, not a r3t
 *
 * Returns 0 if successfully shadowed or already shadowed, -EAGAIN if the
 * shadow table structure is incomplete, -ENOMEM if out of memory and
 * -EFAULT if an address in the parent gmap could not be resolved.
 *
 * Called with sg->mm->mmap_lock in read.
 */
int gmap_shadow_r3t(struct gmap *sg, unsigned long saddr, unsigned long r3t,
                    int fake)
{
        unsigned long raddr, origin, offset, len;
        unsigned long *table;
        phys_addr_t s_r3t;
        struct page *page;
        int rc;

        BUG_ON(!gmap_is_shadow(sg));
        /* Allocate a shadow region second table */
        page = gmap_alloc_crst();
        if (!page)
                return -ENOMEM;
        page->index = r3t & _REGION_ENTRY_ORIGIN;
        if (fake)
                page->index |= GMAP_SHADOW_FAKE_TABLE;
        s_r3t = page_to_phys(page);
        /* Install shadow region second table */
        spin_lock(&sg->guest_table_lock);
        table = gmap_table_walk(sg, saddr, 3); /* get region-2 pointer */
        if (!table) {
                rc = -EAGAIN;           /* Race with unshadow */
                goto out_free;
        }
        if (!(*table & _REGION_ENTRY_INVALID)) {
                rc = 0;                 /* Already established */
                goto out_free;
        } else if (*table & _REGION_ENTRY_ORIGIN) {
                rc = -EAGAIN;           /* Race with shadow */
                goto out_free;
        }
        crst_table_init(__va(s_r3t), _REGION3_ENTRY_EMPTY);
        /* mark as invalid as long as the parent table is not protected */
        *table = s_r3t | _REGION_ENTRY_LENGTH |
                 _REGION_ENTRY_TYPE_R2 | _REGION_ENTRY_INVALID;
        if (sg->edat_level >= 1)
                *table |= (r3t & _REGION_ENTRY_PROTECT);
        list_add(&page->lru, &sg->crst_list);
        if (fake) {
                /* nothing to protect for fake tables */
                *table &= ~_REGION_ENTRY_INVALID;
                spin_unlock(&sg->guest_table_lock);
                return 0;
        }
        spin_unlock(&sg->guest_table_lock);
        /* Make r3t read-only in parent gmap page table */
        raddr = (saddr & _REGION2_MASK) | _SHADOW_RMAP_REGION2;
        origin = r3t & _REGION_ENTRY_ORIGIN;
        offset = ((r3t & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
        len = ((r3t & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
        rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
        spin_lock(&sg->guest_table_lock);
        if (!rc) {
                table = gmap_table_walk(sg, saddr, 3);
                if (!table || (*table & _REGION_ENTRY_ORIGIN) != s_r3t)
                        rc = -EAGAIN;           /* Race with unshadow */
                else
                        *table &= ~_REGION_ENTRY_INVALID;
        } else {
                gmap_unshadow_r3t(sg, raddr);
        }
        spin_unlock(&sg->guest_table_lock);
        return rc;
out_free:
        spin_unlock(&sg->guest_table_lock);
        __free_pages(page, CRST_ALLOC_ORDER);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_shadow_r3t);

/**
 * gmap_shadow_sgt - create a shadow segment table
 * @sg: pointer to the shadow guest address space structure
 * @saddr: faulting address in the shadow gmap
 * @sgt: parent gmap address of the segment table to get shadowed
 * @fake: sgt references contiguous guest memory block, not a sgt
 *
 * Returns: 0 if successfully shadowed or already shadowed, -EAGAIN if the
 * shadow table structure is incomplete, -ENOMEM if out of memory and
 * -EFAULT if an address in the parent gmap could not be resolved.
 *
 * Called with sg->mm->mmap_lock in read.
 */
int gmap_shadow_sgt(struct gmap *sg, unsigned long saddr, unsigned long sgt,
                    int fake)
{
        unsigned long raddr, origin, offset, len;
        unsigned long *table;
        phys_addr_t s_sgt;
        struct page *page;
        int rc;

        BUG_ON(!gmap_is_shadow(sg) || (sgt & _REGION3_ENTRY_LARGE));
        /* Allocate a shadow segment table */
        page = gmap_alloc_crst();
        if (!page)
                return -ENOMEM;
        page->index = sgt & _REGION_ENTRY_ORIGIN;
        if (fake)
                page->index |= GMAP_SHADOW_FAKE_TABLE;
        s_sgt = page_to_phys(page);
        /* Install shadow region second table */
        spin_lock(&sg->guest_table_lock);
        table = gmap_table_walk(sg, saddr, 2); /* get region-3 pointer */
        if (!table) {
                rc = -EAGAIN;           /* Race with unshadow */
                goto out_free;
        }
        if (!(*table & _REGION_ENTRY_INVALID)) {
                rc = 0;                 /* Already established */
                goto out_free;
        } else if (*table & _REGION_ENTRY_ORIGIN) {
                rc = -EAGAIN;           /* Race with shadow */
                goto out_free;
        }
        crst_table_init(__va(s_sgt), _SEGMENT_ENTRY_EMPTY);
        /* mark as invalid as long as the parent table is not protected */
        *table = s_sgt | _REGION_ENTRY_LENGTH |
                 _REGION_ENTRY_TYPE_R3 | _REGION_ENTRY_INVALID;
        if (sg->edat_level >= 1)
                *table |= sgt & _REGION_ENTRY_PROTECT;
        list_add(&page->lru, &sg->crst_list);
        if (fake) {
                /* nothing to protect for fake tables */
                *table &= ~_REGION_ENTRY_INVALID;
                spin_unlock(&sg->guest_table_lock);
                return 0;
        }
        spin_unlock(&sg->guest_table_lock);
        /* Make sgt read-only in parent gmap page table */
        raddr = (saddr & _REGION3_MASK) | _SHADOW_RMAP_REGION3;
        origin = sgt & _REGION_ENTRY_ORIGIN;
        offset = ((sgt & _REGION_ENTRY_OFFSET) >> 6) * PAGE_SIZE;
        len = ((sgt & _REGION_ENTRY_LENGTH) + 1) * PAGE_SIZE - offset;
        rc = gmap_protect_rmap(sg, raddr, origin + offset, len);
        spin_lock(&sg->guest_table_lock);
        if (!rc) {
                table = gmap_table_walk(sg, saddr, 2);
                if (!table || (*table & _REGION_ENTRY_ORIGIN) != s_sgt)
                        rc = -EAGAIN;           /* Race with unshadow */
                else
                        *table &= ~_REGION_ENTRY_INVALID;
        } else {
                gmap_unshadow_sgt(sg, raddr);
        }
        spin_unlock(&sg->guest_table_lock);
        return rc;
out_free:
        spin_unlock(&sg->guest_table_lock);
        __free_pages(page, CRST_ALLOC_ORDER);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_shadow_sgt);

/**
 * gmap_shadow_pgt_lookup - find a shadow page table
 * @sg: pointer to the shadow guest address space structure
 * @saddr: the address in the shadow aguest address space
 * @pgt: parent gmap address of the page table to get shadowed
 * @dat_protection: if the pgtable is marked as protected by dat
 * @fake: pgt references contiguous guest memory block, not a pgtable
 *
 * Returns 0 if the shadow page table was found and -EAGAIN if the page
 * table was not found.
 *
 * Called with sg->mm->mmap_lock in read.
 */
int gmap_shadow_pgt_lookup(struct gmap *sg, unsigned long saddr,
                           unsigned long *pgt, int *dat_protection,
                           int *fake)
{
        unsigned long *table;
        struct page *page;
        int rc;

        BUG_ON(!gmap_is_shadow(sg));
        spin_lock(&sg->guest_table_lock);
        table = gmap_table_walk(sg, saddr, 1); /* get segment pointer */
        if (table && !(*table & _SEGMENT_ENTRY_INVALID)) {
                /* Shadow page tables are full pages (pte+pgste) */
                page = pfn_to_page(*table >> PAGE_SHIFT);
                *pgt = page->index & ~GMAP_SHADOW_FAKE_TABLE;
                *dat_protection = !!(*table & _SEGMENT_ENTRY_PROTECT);
                *fake = !!(page->index & GMAP_SHADOW_FAKE_TABLE);
                rc = 0;
        } else  {
                rc = -EAGAIN;
        }
        spin_unlock(&sg->guest_table_lock);
        return rc;

}
EXPORT_SYMBOL_GPL(gmap_shadow_pgt_lookup);

/**
 * gmap_shadow_pgt - instantiate a shadow page table
 * @sg: pointer to the shadow guest address space structure
 * @saddr: faulting address in the shadow gmap
 * @pgt: parent gmap address of the page table to get shadowed
 * @fake: pgt references contiguous guest memory block, not a pgtable
 *
 * Returns 0 if successfully shadowed or already shadowed, -EAGAIN if the
 * shadow table structure is incomplete, -ENOMEM if out of memory,
 * -EFAULT if an address in the parent gmap could not be resolved and
 *
 * Called with gmap->mm->mmap_lock in read
 */
int gmap_shadow_pgt(struct gmap *sg, unsigned long saddr, unsigned long pgt,
                    int fake)
{
        unsigned long raddr, origin;
        unsigned long *table;
        struct ptdesc *ptdesc;
        phys_addr_t s_pgt;
        int rc;

        BUG_ON(!gmap_is_shadow(sg) || (pgt & _SEGMENT_ENTRY_LARGE));
        /* Allocate a shadow page table */
        ptdesc = page_table_alloc_pgste(sg->mm);
        if (!ptdesc)
                return -ENOMEM;
        ptdesc->pt_index = pgt & _SEGMENT_ENTRY_ORIGIN;
        if (fake)
                ptdesc->pt_index |= GMAP_SHADOW_FAKE_TABLE;
        s_pgt = page_to_phys(ptdesc_page(ptdesc));
        /* Install shadow page table */
        spin_lock(&sg->guest_table_lock);
        table = gmap_table_walk(sg, saddr, 1); /* get segment pointer */
        if (!table) {
                rc = -EAGAIN;           /* Race with unshadow */
                goto out_free;
        }
        if (!(*table & _SEGMENT_ENTRY_INVALID)) {
                rc = 0;                 /* Already established */
                goto out_free;
        } else if (*table & _SEGMENT_ENTRY_ORIGIN) {
                rc = -EAGAIN;           /* Race with shadow */
                goto out_free;
        }
        /* mark as invalid as long as the parent table is not protected */
        *table = (unsigned long) s_pgt | _SEGMENT_ENTRY |
                 (pgt & _SEGMENT_ENTRY_PROTECT) | _SEGMENT_ENTRY_INVALID;
        list_add(&ptdesc->pt_list, &sg->pt_list);
        if (fake) {
                /* nothing to protect for fake tables */
                *table &= ~_SEGMENT_ENTRY_INVALID;
                spin_unlock(&sg->guest_table_lock);
                return 0;
        }
        spin_unlock(&sg->guest_table_lock);
        /* Make pgt read-only in parent gmap page table (not the pgste) */
        raddr = (saddr & _SEGMENT_MASK) | _SHADOW_RMAP_SEGMENT;
        origin = pgt & _SEGMENT_ENTRY_ORIGIN & PAGE_MASK;
        rc = gmap_protect_rmap(sg, raddr, origin, PAGE_SIZE);
        spin_lock(&sg->guest_table_lock);
        if (!rc) {
                table = gmap_table_walk(sg, saddr, 1);
                if (!table || (*table & _SEGMENT_ENTRY_ORIGIN) != s_pgt)
                        rc = -EAGAIN;           /* Race with unshadow */
                else
                        *table &= ~_SEGMENT_ENTRY_INVALID;
        } else {
                gmap_unshadow_pgt(sg, raddr);
        }
        spin_unlock(&sg->guest_table_lock);
        return rc;
out_free:
        spin_unlock(&sg->guest_table_lock);
        page_table_free_pgste(ptdesc);
        return rc;

}
EXPORT_SYMBOL_GPL(gmap_shadow_pgt);

/**
 * gmap_shadow_page - create a shadow page mapping
 * @sg: pointer to the shadow guest address space structure
 * @saddr: faulting address in the shadow gmap
 * @pte: pte in parent gmap address space to get shadowed
 *
 * Returns 0 if successfully shadowed or already shadowed, -EAGAIN if the
 * shadow table structure is incomplete, -ENOMEM if out of memory and
 * -EFAULT if an address in the parent gmap could not be resolved.
 *
 * Called with sg->mm->mmap_lock in read.
 */
int gmap_shadow_page(struct gmap *sg, unsigned long saddr, pte_t pte)
{
        struct gmap *parent;
        struct gmap_rmap *rmap;
        unsigned long vmaddr, paddr;
        spinlock_t *ptl;
        pte_t *sptep, *tptep;
        int prot;
        int rc;

        BUG_ON(!gmap_is_shadow(sg));
        parent = sg->parent;
        prot = (pte_val(pte) & _PAGE_PROTECT) ? PROT_READ : PROT_WRITE;

        rmap = kzalloc(sizeof(*rmap), GFP_KERNEL_ACCOUNT);
        if (!rmap)
                return -ENOMEM;
        rmap->raddr = (saddr & PAGE_MASK) | _SHADOW_RMAP_PGTABLE;

        while (1) {
                paddr = pte_val(pte) & PAGE_MASK;
                vmaddr = __gmap_translate(parent, paddr);
                if (IS_ERR_VALUE(vmaddr)) {
                        rc = vmaddr;
                        break;
                }
                rc = radix_tree_preload(GFP_KERNEL_ACCOUNT);
                if (rc)
                        break;
                rc = -EAGAIN;
                sptep = gmap_pte_op_walk(parent, paddr, &ptl);
                if (sptep) {
                        spin_lock(&sg->guest_table_lock);
                        /* Get page table pointer */
                        tptep = (pte_t *) gmap_table_walk(sg, saddr, 0);
                        if (!tptep) {
                                spin_unlock(&sg->guest_table_lock);
                                gmap_pte_op_end(sptep, ptl);
                                radix_tree_preload_end();
                                break;
                        }
                        rc = ptep_shadow_pte(sg->mm, saddr, sptep, tptep, pte);
                        if (rc > 0) {
                                /* Success and a new mapping */
                                gmap_insert_rmap(sg, vmaddr, rmap);
                                rmap = NULL;
                                rc = 0;
                        }
                        gmap_pte_op_end(sptep, ptl);
                        spin_unlock(&sg->guest_table_lock);
                }
                radix_tree_preload_end();
                if (!rc)
                        break;
                rc = gmap_pte_op_fixup(parent, paddr, vmaddr, prot);
                if (rc)
                        break;
        }
        kfree(rmap);
        return rc;
}
EXPORT_SYMBOL_GPL(gmap_shadow_page);

/*
 * gmap_shadow_notify - handle notifications for shadow gmap
 *
 * Called with sg->parent->shadow_lock.
 */
static void gmap_shadow_notify(struct gmap *sg, unsigned long vmaddr,
                               unsigned long gaddr)
{
        struct gmap_rmap *rmap, *rnext, *head;
        unsigned long start, end, bits, raddr;

        BUG_ON(!gmap_is_shadow(sg));

        spin_lock(&sg->guest_table_lock);
        if (sg->removed) {
                spin_unlock(&sg->guest_table_lock);
                return;
        }
        /* Check for top level table */
        start = sg->orig_asce & _ASCE_ORIGIN;
        end = start + ((sg->orig_asce & _ASCE_TABLE_LENGTH) + 1) * PAGE_SIZE;
        if (!(sg->orig_asce & _ASCE_REAL_SPACE) && gaddr >= start &&
            gaddr < end) {
                /* The complete shadow table has to go */
                gmap_unshadow(sg);
                spin_unlock(&sg->guest_table_lock);
                list_del(&sg->list);
                gmap_put(sg);
                return;
        }
        /* Remove the page table tree from on specific entry */
        head = radix_tree_delete(&sg->host_to_rmap, vmaddr >> PAGE_SHIFT);
        gmap_for_each_rmap_safe(rmap, rnext, head) {
                bits = rmap->raddr & _SHADOW_RMAP_MASK;
                raddr = rmap->raddr ^ bits;
                switch (bits) {
                case _SHADOW_RMAP_REGION1:
                        gmap_unshadow_r2t(sg, raddr);
                        break;
                case _SHADOW_RMAP_REGION2:
                        gmap_unshadow_r3t(sg, raddr);
                        break;
                case _SHADOW_RMAP_REGION3:
                        gmap_unshadow_sgt(sg, raddr);
                        break;
                case _SHADOW_RMAP_SEGMENT:
                        gmap_unshadow_pgt(sg, raddr);
                        break;
                case _SHADOW_RMAP_PGTABLE:
                        gmap_unshadow_page(sg, raddr);
                        break;
                }
                kfree(rmap);
        }
        spin_unlock(&sg->guest_table_lock);
}

/**
 * ptep_notify - call all invalidation callbacks for a specific pte.
 * @mm: pointer to the process mm_struct
 * @vmaddr: virtual address in the process address space
 * @pte: pointer to the page table entry
 * @bits: bits from the pgste that caused the notify call
 *
 * This function is assumed to be called with the page table lock held
 * for the pte to notify.
 */
void ptep_notify(struct mm_struct *mm, unsigned long vmaddr,
                 pte_t *pte, unsigned long bits)
{
        unsigned long offset, gaddr = 0;
        unsigned long *table;
        struct gmap *gmap, *sg, *next;

        offset = ((unsigned long) pte) & (255 * sizeof(pte_t));
        offset = offset * (PAGE_SIZE / sizeof(pte_t));
        rcu_read_lock();
        list_for_each_entry_rcu(gmap, &mm->context.gmap_list, list) {
                spin_lock(&gmap->guest_table_lock);
                table = radix_tree_lookup(&gmap->host_to_guest,
                                          vmaddr >> PMD_SHIFT);
                if (table)
                        gaddr = __gmap_segment_gaddr(table) + offset;
                spin_unlock(&gmap->guest_table_lock);
                if (!table)
                        continue;

                if (!list_empty(&gmap->children) && (bits & PGSTE_VSIE_BIT)) {
                        spin_lock(&gmap->shadow_lock);
                        list_for_each_entry_safe(sg, next,
                                                 &gmap->children, list)
                                gmap_shadow_notify(sg, vmaddr, gaddr);
                        spin_unlock(&gmap->shadow_lock);
                }
                if (bits & PGSTE_IN_BIT)
                        gmap_call_notifier(gmap, gaddr, gaddr + PAGE_SIZE - 1);
        }
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(ptep_notify);

static void pmdp_notify_gmap(struct gmap *gmap, pmd_t *pmdp,
                             unsigned long gaddr)
{
        set_pmd(pmdp, clear_pmd_bit(*pmdp, __pgprot(_SEGMENT_ENTRY_GMAP_IN)));
        gmap_call_notifier(gmap, gaddr, gaddr + HPAGE_SIZE - 1);
}

/**
 * gmap_pmdp_xchg - exchange a gmap pmd with another
 * @gmap: pointer to the guest address space structure
 * @pmdp: pointer to the pmd entry
 * @new: replacement entry
 * @gaddr: the affected guest address
 *
 * This function is assumed to be called with the guest_table_lock
 * held.
 */
static void gmap_pmdp_xchg(struct gmap *gmap, pmd_t *pmdp, pmd_t new,
                           unsigned long gaddr)
{
        gaddr &= HPAGE_MASK;
        pmdp_notify_gmap(gmap, pmdp, gaddr);
        new = clear_pmd_bit(new, __pgprot(_SEGMENT_ENTRY_GMAP_IN));
        if (MACHINE_HAS_TLB_GUEST)
                __pmdp_idte(gaddr, (pmd_t *)pmdp, IDTE_GUEST_ASCE, gmap->asce,
                            IDTE_GLOBAL);
        else if (MACHINE_HAS_IDTE)
                __pmdp_idte(gaddr, (pmd_t *)pmdp, 0, 0, IDTE_GLOBAL);
        else
                __pmdp_csp(pmdp);
        set_pmd(pmdp, new);
}

static void gmap_pmdp_clear(struct mm_struct *mm, unsigned long vmaddr,
                            int purge)
{
        pmd_t *pmdp;
        struct gmap *gmap;
        unsigned long gaddr;

        rcu_read_lock();
        list_for_each_entry_rcu(gmap, &mm->context.gmap_list, list) {
                spin_lock(&gmap->guest_table_lock);
                pmdp = (pmd_t *)radix_tree_delete(&gmap->host_to_guest,
                                                  vmaddr >> PMD_SHIFT);
                if (pmdp) {
                        gaddr = __gmap_segment_gaddr((unsigned long *)pmdp);
                        pmdp_notify_gmap(gmap, pmdp, gaddr);
                        WARN_ON(pmd_val(*pmdp) & ~(_SEGMENT_ENTRY_HARDWARE_BITS_LARGE |
                                                   _SEGMENT_ENTRY_GMAP_UC));
                        if (purge)
                                __pmdp_csp(pmdp);
                        set_pmd(pmdp, __pmd(_SEGMENT_ENTRY_EMPTY));
                }
                spin_unlock(&gmap->guest_table_lock);
        }
        rcu_read_unlock();
}

/**
 * gmap_pmdp_invalidate - invalidate all affected guest pmd entries without
 *                        flushing
 * @mm: pointer to the process mm_struct
 * @vmaddr: virtual address in the process address space
 */
void gmap_pmdp_invalidate(struct mm_struct *mm, unsigned long vmaddr)
{
        gmap_pmdp_clear(mm, vmaddr, 0);
}
EXPORT_SYMBOL_GPL(gmap_pmdp_invalidate);

/**
 * gmap_pmdp_csp - csp all affected guest pmd entries
 * @mm: pointer to the process mm_struct
 * @vmaddr: virtual address in the process address space
 */
void gmap_pmdp_csp(struct mm_struct *mm, unsigned long vmaddr)
{
        gmap_pmdp_clear(mm, vmaddr, 1);
}
EXPORT_SYMBOL_GPL(gmap_pmdp_csp);

/**
 * gmap_pmdp_idte_local - invalidate and clear a guest pmd entry
 * @mm: pointer to the process mm_struct
 * @vmaddr: virtual address in the process address space
 */
void gmap_pmdp_idte_local(struct mm_struct *mm, unsigned long vmaddr)
{
        unsigned long *entry, gaddr;
        struct gmap *gmap;
        pmd_t *pmdp;

        rcu_read_lock();
        list_for_each_entry_rcu(gmap, &mm->context.gmap_list, list) {
                spin_lock(&gmap->guest_table_lock);
                entry = radix_tree_delete(&gmap->host_to_guest,
                                          vmaddr >> PMD_SHIFT);
                if (entry) {
                        pmdp = (pmd_t *)entry;
                        gaddr = __gmap_segment_gaddr(entry);
                        pmdp_notify_gmap(gmap, pmdp, gaddr);
                        WARN_ON(*entry & ~(_SEGMENT_ENTRY_HARDWARE_BITS_LARGE |
                                           _SEGMENT_ENTRY_GMAP_UC));
                        if (MACHINE_HAS_TLB_GUEST)
                                __pmdp_idte(gaddr, pmdp, IDTE_GUEST_ASCE,
                                            gmap->asce, IDTE_LOCAL);
                        else if (MACHINE_HAS_IDTE)
                                __pmdp_idte(gaddr, pmdp, 0, 0, IDTE_LOCAL);
                        *entry = _SEGMENT_ENTRY_EMPTY;
                }
                spin_unlock(&gmap->guest_table_lock);
        }
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(gmap_pmdp_idte_local);

/**
 * gmap_pmdp_idte_global - invalidate and clear a guest pmd entry
 * @mm: pointer to the process mm_struct
 * @vmaddr: virtual address in the process address space
 */
void gmap_pmdp_idte_global(struct mm_struct *mm, unsigned long vmaddr)
{
        unsigned long *entry, gaddr;
        struct gmap *gmap;
        pmd_t *pmdp;

        rcu_read_lock();
        list_for_each_entry_rcu(gmap, &mm->context.gmap_list, list) {
                spin_lock(&gmap->guest_table_lock);
                entry = radix_tree_delete(&gmap->host_to_guest,
                                          vmaddr >> PMD_SHIFT);
                if (entry) {
                        pmdp = (pmd_t *)entry;
                        gaddr = __gmap_segment_gaddr(entry);
                        pmdp_notify_gmap(gmap, pmdp, gaddr);
                        WARN_ON(*entry & ~(_SEGMENT_ENTRY_HARDWARE_BITS_LARGE |
                                           _SEGMENT_ENTRY_GMAP_UC));
                        if (MACHINE_HAS_TLB_GUEST)
                                __pmdp_idte(gaddr, pmdp, IDTE_GUEST_ASCE,
                                            gmap->asce, IDTE_GLOBAL);
                        else if (MACHINE_HAS_IDTE)
                                __pmdp_idte(gaddr, pmdp, 0, 0, IDTE_GLOBAL);
                        else
                                __pmdp_csp(pmdp);
                        *entry = _SEGMENT_ENTRY_EMPTY;
                }
                spin_unlock(&gmap->guest_table_lock);
        }
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(gmap_pmdp_idte_global);

/**
 * gmap_test_and_clear_dirty_pmd - test and reset segment dirty status
 * @gmap: pointer to guest address space
 * @pmdp: pointer to the pmd to be tested
 * @gaddr: virtual address in the guest address space
 *
 * This function is assumed to be called with the guest_table_lock
 * held.
 */
static bool gmap_test_and_clear_dirty_pmd(struct gmap *gmap, pmd_t *pmdp,
                                          unsigned long gaddr)
{
        if (pmd_val(*pmdp) & _SEGMENT_ENTRY_INVALID)
                return false;

        /* Already protected memory, which did not change is clean */
        if (pmd_val(*pmdp) & _SEGMENT_ENTRY_PROTECT &&
            !(pmd_val(*pmdp) & _SEGMENT_ENTRY_GMAP_UC))
                return false;

        /* Clear UC indication and reset protection */
        set_pmd(pmdp, clear_pmd_bit(*pmdp, __pgprot(_SEGMENT_ENTRY_GMAP_UC)));
        gmap_protect_pmd(gmap, gaddr, pmdp, PROT_READ, 0);
        return true;
}

/**
 * gmap_sync_dirty_log_pmd - set bitmap based on dirty status of segment
 * @gmap: pointer to guest address space
 * @bitmap: dirty bitmap for this pmd
 * @gaddr: virtual address in the guest address space
 * @vmaddr: virtual address in the host address space
 *
 * This function is assumed to be called with the guest_table_lock
 * held.
 */
void gmap_sync_dirty_log_pmd(struct gmap *gmap, unsigned long bitmap[4],
                             unsigned long gaddr, unsigned long vmaddr)
{
        int i;
        pmd_t *pmdp;
        pte_t *ptep;
        spinlock_t *ptl;

        pmdp = gmap_pmd_op_walk(gmap, gaddr);
        if (!pmdp)
                return;

        if (pmd_leaf(*pmdp)) {
                if (gmap_test_and_clear_dirty_pmd(gmap, pmdp, gaddr))
                        bitmap_fill(bitmap, _PAGE_ENTRIES);
        } else {
                for (i = 0; i < _PAGE_ENTRIES; i++, vmaddr += PAGE_SIZE) {
                        ptep = pte_alloc_map_lock(gmap->mm, pmdp, vmaddr, &ptl);
                        if (!ptep)
                                continue;
                        if (ptep_test_and_clear_uc(gmap->mm, vmaddr, ptep))
                                set_bit(i, bitmap);
                        pte_unmap_unlock(ptep, ptl);
                }
        }
        gmap_pmd_op_end(gmap, pmdp);
}
EXPORT_SYMBOL_GPL(gmap_sync_dirty_log_pmd);

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static int thp_split_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
                                    unsigned long end, struct mm_walk *walk)
{
        struct vm_area_struct *vma = walk->vma;

        split_huge_pmd(vma, pmd, addr);
        return 0;
}

static const struct mm_walk_ops thp_split_walk_ops = {
        .pmd_entry      = thp_split_walk_pmd_entry,
        .walk_lock      = PGWALK_WRLOCK_VERIFY,
};

static inline void thp_split_mm(struct mm_struct *mm)
{
        struct vm_area_struct *vma;
        VMA_ITERATOR(vmi, mm, 0);

        for_each_vma(vmi, vma) {
                vm_flags_mod(vma, VM_NOHUGEPAGE, VM_HUGEPAGE);
                walk_page_vma(vma, &thp_split_walk_ops, NULL);
        }
        mm->def_flags |= VM_NOHUGEPAGE;
}
#else
static inline void thp_split_mm(struct mm_struct *mm)
{
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

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

        /* Do we have pgstes? if yes, we are done */
        if (mm_has_pgste(mm))
                return 0;
        /* Fail if the page tables are 2K */
        if (!mm_alloc_pgste(mm))
                return -EINVAL;
        mmap_write_lock(mm);
        mm->context.has_pgste = 1;
        /* split thp mappings and disable thp for future mappings */
        thp_split_mm(mm);
        mmap_write_unlock(mm);
        return 0;
}
EXPORT_SYMBOL_GPL(s390_enable_sie);

static int find_zeropage_pte_entry(pte_t *pte, unsigned long addr,
                                   unsigned long end, struct mm_walk *walk)
{
        unsigned long *found_addr = walk->private;

        /* Return 1 of the page is a zeropage. */
        if (is_zero_pfn(pte_pfn(*pte))) {
                /*
                 * Shared zeropage in e.g., a FS DAX mapping? We cannot do the
                 * right thing and likely don't care: FAULT_FLAG_UNSHARE
                 * currently only works in COW mappings, which is also where
                 * mm_forbids_zeropage() is checked.
                 */
                if (!is_cow_mapping(walk->vma->vm_flags))
                        return -EFAULT;

                *found_addr = addr;
                return 1;
        }
        return 0;
}

static const struct mm_walk_ops find_zeropage_ops = {
        .pte_entry      = find_zeropage_pte_entry,
        .walk_lock      = PGWALK_WRLOCK,
};

/*
 * Unshare all shared zeropages, replacing them by anonymous pages. Note that
 * we cannot simply zap all shared zeropages, because this could later
 * trigger unexpected userfaultfd missing events.
 *
 * This must be called after mm->context.allow_cow_sharing was
 * set to 0, to avoid future mappings of shared zeropages.
 *
 * mm contracts with s390, that even if mm were to remove a page table,
 * and racing with walk_page_range_vma() calling pte_offset_map_lock()
 * would fail, it will never insert a page table containing empty zero
 * pages once mm_forbids_zeropage(mm) i.e.
 * mm->context.allow_cow_sharing is set to 0.
 */
static int __s390_unshare_zeropages(struct mm_struct *mm)
{
        struct vm_area_struct *vma;
        VMA_ITERATOR(vmi, mm, 0);
        unsigned long addr;
        vm_fault_t fault;
        int rc;

        for_each_vma(vmi, vma) {
                /*
                 * We could only look at COW mappings, but it's more future
                 * proof to catch unexpected zeropages in other mappings and
                 * fail.
                 */
                if ((vma->vm_flags & VM_PFNMAP) || is_vm_hugetlb_page(vma))
                        continue;
                addr = vma->vm_start;

retry:
                rc = walk_page_range_vma(vma, addr, vma->vm_end,
                                         &find_zeropage_ops, &addr);
                if (rc < 0)
                        return rc;
                else if (!rc)
                        continue;

                /* addr was updated by find_zeropage_pte_entry() */
                fault = handle_mm_fault(vma, addr,
                                        FAULT_FLAG_UNSHARE | FAULT_FLAG_REMOTE,
                                        NULL);
                if (fault & VM_FAULT_OOM)
                        return -ENOMEM;
                /*
                 * See break_ksm(): even after handle_mm_fault() returned 0, we
                 * must start the lookup from the current address, because
                 * handle_mm_fault() may back out if there's any difficulty.
                 *
                 * VM_FAULT_SIGBUS and VM_FAULT_SIGSEGV are unexpected but
                 * maybe they could trigger in the future on concurrent
                 * truncation. In that case, the shared zeropage would be gone
                 * and we can simply retry and make progress.
                 */
                cond_resched();
                goto retry;
        }

        return 0;
}

static int __s390_disable_cow_sharing(struct mm_struct *mm)
{
        int rc;

        if (!mm->context.allow_cow_sharing)
                return 0;

        mm->context.allow_cow_sharing = 0;

        /* Replace all shared zeropages by anonymous pages. */
        rc = __s390_unshare_zeropages(mm);
        /*
         * Make sure to disable KSM (if enabled for the whole process or
         * individual VMAs). Note that nothing currently hinders user space
         * from re-enabling it.
         */
        if (!rc)
                rc = ksm_disable(mm);
        if (rc)
                mm->context.allow_cow_sharing = 1;
        return rc;
}

/*
 * Disable most COW-sharing of memory pages for the whole process:
 * (1) Disable KSM and unmerge/unshare any KSM pages.
 * (2) Disallow shared zeropages and unshare any zerpages that are mapped.
 *
 * Not that we currently don't bother with COW-shared pages that are shared
 * with parent/child processes due to fork().
 */
int s390_disable_cow_sharing(void)
{
        int rc;

        mmap_write_lock(current->mm);
        rc = __s390_disable_cow_sharing(current->mm);
        mmap_write_unlock(current->mm);
        return rc;
}
EXPORT_SYMBOL_GPL(s390_disable_cow_sharing);

/*
 * Enable storage key handling from now on and initialize the storage
 * keys with the default key.
 */
static int __s390_enable_skey_pte(pte_t *pte, unsigned long addr,
                                  unsigned long next, struct mm_walk *walk)
{
        /* Clear storage key */
        ptep_zap_key(walk->mm, addr, pte);
        return 0;
}

/*
 * Give a chance to schedule after setting a key to 256 pages.
 * We only hold the mm lock, which is a rwsem and the kvm srcu.
 * Both can sleep.
 */
static int __s390_enable_skey_pmd(pmd_t *pmd, unsigned long addr,
                                  unsigned long next, struct mm_walk *walk)
{
        cond_resched();
        return 0;
}

static int __s390_enable_skey_hugetlb(pte_t *pte, unsigned long addr,
                                      unsigned long hmask, unsigned long next,
                                      struct mm_walk *walk)
{
        pmd_t *pmd = (pmd_t *)pte;
        unsigned long start, end;
        struct page *page = pmd_page(*pmd);

        /*
         * The write check makes sure we do not set a key on shared
         * memory. This is needed as the walker does not differentiate
         * between actual guest memory and the process executable or
         * shared libraries.
         */
        if (pmd_val(*pmd) & _SEGMENT_ENTRY_INVALID ||
            !(pmd_val(*pmd) & _SEGMENT_ENTRY_WRITE))
                return 0;

        start = pmd_val(*pmd) & HPAGE_MASK;
        end = start + HPAGE_SIZE;
        __storage_key_init_range(start, end);
        set_bit(PG_arch_1, &page->flags);
        cond_resched();
        return 0;
}

static const struct mm_walk_ops enable_skey_walk_ops = {
        .hugetlb_entry          = __s390_enable_skey_hugetlb,
        .pte_entry              = __s390_enable_skey_pte,
        .pmd_entry              = __s390_enable_skey_pmd,
        .walk_lock              = PGWALK_WRLOCK,
};

int s390_enable_skey(void)
{
        struct mm_struct *mm = current->mm;
        int rc = 0;

        mmap_write_lock(mm);
        if (mm_uses_skeys(mm))
                goto out_up;

        mm->context.uses_skeys = 1;
        rc = __s390_disable_cow_sharing(mm);
        if (rc) {
                mm->context.uses_skeys = 0;
                goto out_up;
        }
        walk_page_range(mm, 0, TASK_SIZE, &enable_skey_walk_ops, NULL);

out_up:
        mmap_write_unlock(mm);
        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)
{
        ptep_zap_unused(walk->mm, addr, pte, 1);
        return 0;
}

static const struct mm_walk_ops reset_cmma_walk_ops = {
        .pte_entry              = __s390_reset_cmma,
        .walk_lock              = PGWALK_WRLOCK,
};

void s390_reset_cmma(struct mm_struct *mm)
{
        mmap_write_lock(mm);
        walk_page_range(mm, 0, TASK_SIZE, &reset_cmma_walk_ops, NULL);
        mmap_write_unlock(mm);
}
EXPORT_SYMBOL_GPL(s390_reset_cmma);

#define GATHER_GET_PAGES 32

struct reset_walk_state {
        unsigned long next;
        unsigned long count;
        unsigned long pfns[GATHER_GET_PAGES];
};

static int s390_gather_pages(pte_t *ptep, unsigned long addr,
                             unsigned long next, struct mm_walk *walk)
{
        struct reset_walk_state *p = walk->private;
        pte_t pte = READ_ONCE(*ptep);

        if (pte_present(pte)) {
                /* we have a reference from the mapping, take an extra one */
                get_page(phys_to_page(pte_val(pte)));
                p->pfns[p->count] = phys_to_pfn(pte_val(pte));
                p->next = next;
                p->count++;
        }
        return p->count >= GATHER_GET_PAGES;
}

static const struct mm_walk_ops gather_pages_ops = {
        .pte_entry = s390_gather_pages,
        .walk_lock = PGWALK_RDLOCK,
};

/*
 * Call the Destroy secure page UVC on each page in the given array of PFNs.
 * Each page needs to have an extra reference, which will be released here.
 */
void s390_uv_destroy_pfns(unsigned long count, unsigned long *pfns)
{
        unsigned long i;

        for (i = 0; i < count; i++) {
                /* we always have an extra reference */
                uv_destroy_owned_page(pfn_to_phys(pfns[i]));
                /* get rid of the extra reference */
                put_page(pfn_to_page(pfns[i]));
                cond_resched();
        }
}
EXPORT_SYMBOL_GPL(s390_uv_destroy_pfns);

/**
 * __s390_uv_destroy_range - Call the destroy secure page UVC on each page
 * in the given range of the given address space.
 * @mm: the mm to operate on
 * @start: the start of the range
 * @end: the end of the range
 * @interruptible: if not 0, stop when a fatal signal is received
 *
 * Walk the given range of the given address space and call the destroy
 * secure page UVC on each page. Optionally exit early if a fatal signal is
 * pending.
 *
 * Return: 0 on success, -EINTR if the function stopped before completing
 */
int __s390_uv_destroy_range(struct mm_struct *mm, unsigned long start,
                            unsigned long end, bool interruptible)
{
        struct reset_walk_state state = { .next = start };
        int r = 1;

        while (r > 0) {
                state.count = 0;
                mmap_read_lock(mm);
                r = walk_page_range(mm, state.next, end, &gather_pages_ops, &state);
                mmap_read_unlock(mm);
                cond_resched();
                s390_uv_destroy_pfns(state.count, state.pfns);
                if (interruptible && fatal_signal_pending(current))
                        return -EINTR;
        }
        return 0;
}
EXPORT_SYMBOL_GPL(__s390_uv_destroy_range);

/**
 * s390_unlist_old_asce - Remove the topmost level of page tables from the
 * list of page tables of the gmap.
 * @gmap: the gmap whose table is to be removed
 *
 * On s390x, KVM keeps a list of all pages containing the page tables of the
 * gmap (the CRST list). This list is used at tear down time to free all
 * pages that are now not needed anymore.
 *
 * This function removes the topmost page of the tree (the one pointed to by
 * the ASCE) from the CRST list.
 *
 * This means that it will not be freed when the VM is torn down, and needs
 * to be handled separately by the caller, unless a leak is actually
 * intended. Notice that this function will only remove the page from the
 * list, the page will still be used as a top level page table (and ASCE).
 */
void s390_unlist_old_asce(struct gmap *gmap)
{
        struct page *old;

        old = virt_to_page(gmap->table);
        spin_lock(&gmap->guest_table_lock);
        list_del(&old->lru);
        /*
         * Sometimes the topmost page might need to be "removed" multiple
         * times, for example if the VM is rebooted into secure mode several
         * times concurrently, or if s390_replace_asce fails after calling
         * s390_remove_old_asce and is attempted again later. In that case
         * the old asce has been removed from the list, and therefore it
         * will not be freed when the VM terminates, but the ASCE is still
         * in use and still pointed to.
         * A subsequent call to replace_asce will follow the pointer and try
         * to remove the same page from the list again.
         * Therefore it's necessary that the page of the ASCE has valid
         * pointers, so list_del can work (and do nothing) without
         * dereferencing stale or invalid pointers.
         */
        INIT_LIST_HEAD(&old->lru);
        spin_unlock(&gmap->guest_table_lock);
}
EXPORT_SYMBOL_GPL(s390_unlist_old_asce);

/**
 * s390_replace_asce - Try to replace the current ASCE of a gmap with a copy
 * @gmap: the gmap whose ASCE needs to be replaced
 *
 * If the ASCE is a SEGMENT type then this function will return -EINVAL,
 * otherwise the pointers in the host_to_guest radix tree will keep pointing
 * to the wrong pages, causing use-after-free and memory corruption.
 * If the allocation of the new top level page table fails, the ASCE is not
 * replaced.
 * In any case, the old ASCE is always removed from the gmap CRST list.
 * Therefore the caller has to make sure to save a pointer to it
 * beforehand, unless a leak is actually intended.
 */
int s390_replace_asce(struct gmap *gmap)
{
        unsigned long asce;
        struct page *page;
        void *table;

        s390_unlist_old_asce(gmap);

        /* Replacing segment type ASCEs would cause serious issues */
        if ((gmap->asce & _ASCE_TYPE_MASK) == _ASCE_TYPE_SEGMENT)
                return -EINVAL;

        page = gmap_alloc_crst();
        if (!page)
                return -ENOMEM;
        page->index = 0;
        table = page_to_virt(page);
        memcpy(table, gmap->table, 1UL << (CRST_ALLOC_ORDER + PAGE_SHIFT));

        /*
         * The caller has to deal with the old ASCE, but here we make sure
         * the new one is properly added to the CRST list, so that
         * it will be freed when the VM is torn down.
         */
        spin_lock(&gmap->guest_table_lock);
        list_add(&page->lru, &gmap->crst_list);
        spin_unlock(&gmap->guest_table_lock);

        /* Set new table origin while preserving existing ASCE control bits */
        asce = (gmap->asce & ~_ASCE_ORIGIN) | __pa(table);
        WRITE_ONCE(gmap->asce, asce);
        WRITE_ONCE(gmap->mm->context.gmap_asce, asce);
        WRITE_ONCE(gmap->table, table);

        return 0;
}
EXPORT_SYMBOL_GPL(s390_replace_asce);