text: /*
   *    Copyright IBM Corp. 2007, 2011
   *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
   */
  
  #include <linux/sched.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/gfp.h>
  #include <linux/mm.h>
  #include <linux/swap.h>
  #include <linux/smp.h>
  #include <linux/highmem.h>
  #include <linux/pagemap.h>
  #include <linux/spinlock.h>
  #include <linux/module.h>
  #include <linux/quicklist.h>
  #include <linux/rcupdate.h>
  #include <linux/slab.h>
  
  #include <asm/pgtable.h>
  #include <asm/pgalloc.h>
  #include <asm/tlb.h>
  #include <asm/tlbflush.h>
  #include <asm/mmu_context.h>
  
  #ifndef CONFIG_64BIT
  #define ALLOC_ORDER	1
  #define FRAG_MASK	0x0f
  #else
  #define ALLOC_ORDER	2
  #define FRAG_MASK	0x03
  #endif
  
  
  unsigned long *crst_table_alloc(struct mm_struct *mm)
  {
  	struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
  
  	if (!page)
  		return NULL;
  	return (unsigned long *) page_to_phys(page);
  }
  
  void crst_table_free(struct mm_struct *mm, unsigned long *table)
  {
  	free_pages((unsigned long) table, ALLOC_ORDER);
  }
  
  #ifdef CONFIG_64BIT
  static void __crst_table_upgrade(void *arg)
  {
  	struct mm_struct *mm = arg;
  
  	if (current->active_mm == mm)
  		update_mm(mm, current);
  	__tlb_flush_local();
  }
  
  int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
  {
  	unsigned long *table, *pgd;
  	unsigned long entry;
  	int flush;
  
  	BUG_ON(limit > (1UL << 53));
  	flush = 0;
  repeat:
  	table = crst_table_alloc(mm);
  	if (!table)
  		return -ENOMEM;
  	spin_lock_bh(&mm->page_table_lock);
  	if (mm->context.asce_limit < limit) {
  		pgd = (unsigned long *) mm->pgd;
  		if (mm->context.asce_limit <= (1UL << 31)) {
  			entry = _REGION3_ENTRY_EMPTY;
  			mm->context.asce_limit = 1UL << 42;
  			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
  						_ASCE_USER_BITS |
  						_ASCE_TYPE_REGION3;
  		} else {
  			entry = _REGION2_ENTRY_EMPTY;
  			mm->context.asce_limit = 1UL << 53;
  			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
  						_ASCE_USER_BITS |
  						_ASCE_TYPE_REGION2;
  		}
  		crst_table_init(table, entry);
  		pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd);
  		mm->pgd = (pgd_t *) table;
  		mm->task_size = mm->context.asce_limit;
  		table = NULL;
  		flush = 1;
  	}
  	spin_unlock_bh(&mm->page_table_lock);
  	if (table)
  		crst_table_free(mm, table);
  	if (mm->context.asce_limit < limit)
  		goto repeat;
  	if (flush)
  		on_each_cpu(__crst_table_upgrade, mm, 0);
  	return 0;
  }
  
  void crst_table_downgrade(struct mm_struct *mm, unsigned long limit)
  {
  	pgd_t *pgd;
  
  	if (current->active_mm == mm)
  		__tlb_flush_mm(mm);
  	while (mm->context.asce_limit > limit) {
  		pgd = mm->pgd;
  		switch (pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) {
  		case _REGION_ENTRY_TYPE_R2:
  			mm->context.asce_limit = 1UL << 42;
  			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
  						_ASCE_USER_BITS |
  						_ASCE_TYPE_REGION3;
  			break;
  		case _REGION_ENTRY_TYPE_R3:
  			mm->context.asce_limit = 1UL << 31;
  			mm->context.asce_bits = _ASCE_TABLE_LENGTH |
  						_ASCE_USER_BITS |
  						_ASCE_TYPE_SEGMENT;
  			break;
  		default:
  			BUG();
  		}
  		mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
  		mm->task_size = mm->context.asce_limit;
  		crst_table_free(mm, (unsigned long *) pgd);
  	}
  	if (current->active_mm == mm)
  		update_mm(mm, current);
  }
  #endif
  
  #ifdef CONFIG_PGSTE
  
  /**
   * gmap_alloc - allocate a guest address space
   * @mm: pointer to the parent mm_struct
   *
   * Returns a guest address space structure.
   */
  struct gmap *gmap_alloc(struct mm_struct *mm)
  {
  	struct gmap *gmap;
  	struct page *page;
  	unsigned long *table;
  
  	gmap = kzalloc(sizeof(struct gmap), GFP_KERNEL);
  	if (!gmap)
  		goto out;
  	INIT_LIST_HEAD(&gmap->crst_list);
  	gmap->mm = mm;
  	page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
  	if (!page)
  		goto out_free;
  	list_add(&page->lru, &gmap->crst_list);
  	table = (unsigned long *) page_to_phys(page);
  	crst_table_init(table, _REGION1_ENTRY_EMPTY);
  	gmap->table = table;
  	gmap->asce = _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH |
  		     _ASCE_USER_BITS | __pa(table);
  	list_add(&gmap->list, &mm->context.gmap_list);
  	return gmap;
  
  out_free:
  	kfree(gmap);
  out:
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(gmap_alloc);
  
  static int gmap_unlink_segment(struct gmap *gmap, unsigned long *table)
  {
  	struct gmap_pgtable *mp;
  	struct gmap_rmap *rmap;
  	struct page *page;
  
  	if (*table & _SEGMENT_ENTRY_INVALID)
  		return 0;
  	page = pfn_to_page(*table >> PAGE_SHIFT);
  	mp = (struct gmap_pgtable *) page->index;
  	list_for_each_entry(rmap, &mp->mapper, list) {
  		if (rmap->entry != table)
  			continue;
  		list_del(&rmap->list);
  		kfree(rmap);
  		break;
  	}
  	*table = mp->vmaddr | _SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_PROTECT;
  	return 1;
  }
  
  static void gmap_flush_tlb(struct gmap *gmap)
  {
  	if (MACHINE_HAS_IDTE)
  		__tlb_flush_idte((unsigned long) gmap->table |
  				 _ASCE_TYPE_REGION1);
  	else
  		__tlb_flush_global();
  }
  
  /**
   * gmap_free - free a guest address space
   * @gmap: pointer to the guest address space structure
   */
  void gmap_free(struct gmap *gmap)
  {
  	struct page *page, *next;
  	unsigned long *table;
  	int i;
  
  
  	/* Flush tlb. */
  	if (MACHINE_HAS_IDTE)
  		__tlb_flush_idte((unsigned long) gmap->table |
  				 _ASCE_TYPE_REGION1);
  	else
  		__tlb_flush_global();
  
  	/* Free all segment & region tables. */
  	down_read(&gmap->mm->mmap_sem);
  	spin_lock(&gmap->mm->page_table_lock);
  	list_for_each_entry_safe(page, next, &gmap->crst_list, lru) {
  		table = (unsigned long *) page_to_phys(page);
  		if ((*table & _REGION_ENTRY_TYPE_MASK) == 0)
  			/* Remove gmap rmap structures for segment table. */
  			for (i = 0; i < PTRS_PER_PMD; i++, table++)
  				gmap_unlink_segment(gmap, table);
  		__free_pages(page, ALLOC_ORDER);
  	}
  	spin_unlock(&gmap->mm->page_table_lock);
  	up_read(&gmap->mm->mmap_sem);
  	list_del(&gmap->list);
  	kfree(gmap);
  }
  EXPORT_SYMBOL_GPL(gmap_free);
  
  /**
   * gmap_enable - switch primary space to the guest address space
   * @gmap: pointer to the guest address space structure
   */
  void gmap_enable(struct gmap *gmap)
  {
  	S390_lowcore.gmap = (unsigned long) gmap;
  }
  EXPORT_SYMBOL_GPL(gmap_enable);
  
  /**
   * gmap_disable - switch back to the standard primary address space
   * @gmap: pointer to the guest address space structure
   */
  void gmap_disable(struct gmap *gmap)
  {
  	S390_lowcore.gmap = 0UL;
  }
  EXPORT_SYMBOL_GPL(gmap_disable);
  
  /*
   * gmap_alloc_table is assumed to be called with mmap_sem held
   */
  static int gmap_alloc_table(struct gmap *gmap,
  			    unsigned long *table, unsigned long init)
  	__releases(&gmap->mm->page_table_lock)
  	__acquires(&gmap->mm->page_table_lock)
  {
  	struct page *page;
  	unsigned long *new;
  
  	/* since we dont free the gmap table until gmap_free we can unlock */
  	spin_unlock(&gmap->mm->page_table_lock);
  	page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
  	spin_lock(&gmap->mm->page_table_lock);
  	if (!page)
  		return -ENOMEM;
  	new = (unsigned long *) page_to_phys(page);
  	crst_table_init(new, init);
  	if (*table & _REGION_ENTRY_INVALID) {
  		list_add(&page->lru, &gmap->crst_list);
  		*table = (unsigned long) new | _REGION_ENTRY_LENGTH |
  			(*table & _REGION_ENTRY_TYPE_MASK);
  	} else
  		__free_pages(page, ALLOC_ORDER);
  	return 0;
  }
  
  /**
   * gmap_unmap_segment - unmap segment from the guest address space
   * @gmap: pointer to the guest address space structure
   * @addr: 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 *table;
  	unsigned long off;
  	int flush;
  
  	if ((to | len) & (PMD_SIZE - 1))
  		return -EINVAL;
  	if (len == 0 || to + len < to)
  		return -EINVAL;
  
  	flush = 0;
  	down_read(&gmap->mm->mmap_sem);
  	spin_lock(&gmap->mm->page_table_lock);
  	for (off = 0; off < len; off += PMD_SIZE) {
  		/* Walk the guest addr space page table */
  		table = gmap->table + (((to + off) >> 53) & 0x7ff);
  		if (*table & _REGION_ENTRY_INVALID)
  			goto out;
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + (((to + off) >> 42) & 0x7ff);
  		if (*table & _REGION_ENTRY_INVALID)
  			goto out;
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + (((to + off) >> 31) & 0x7ff);
  		if (*table & _REGION_ENTRY_INVALID)
  			goto out;
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + (((to + off) >> 20) & 0x7ff);
  
  		/* Clear segment table entry in guest address space. */
  		flush |= gmap_unlink_segment(gmap, table);
  		*table = _SEGMENT_ENTRY_INVALID;
  	}
  out:
  	spin_unlock(&gmap->mm->page_table_lock);
  	up_read(&gmap->mm->mmap_sem);
  	if (flush)
  		gmap_flush_tlb(gmap);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(gmap_unmap_segment);
  
  /**
   * gmap_mmap_segment - map a segment to the guest address space
   * @gmap: pointer to the guest address space structure
   * @from: source address in the parent address space
   * @to: target address in the guest address space
   *
   * 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 *table;
  	unsigned long off;
  	int flush;
  
  	if ((from | to | len) & (PMD_SIZE - 1))
  		return -EINVAL;
  	if (len == 0 || from + len > TASK_MAX_SIZE ||
  	    from + len < from || to + len < to)
  		return -EINVAL;
  
  	flush = 0;
  	down_read(&gmap->mm->mmap_sem);
  	spin_lock(&gmap->mm->page_table_lock);
  	for (off = 0; off < len; off += PMD_SIZE) {
  		/* Walk the gmap address space page table */
  		table = gmap->table + (((to + off) >> 53) & 0x7ff);
  		if ((*table & _REGION_ENTRY_INVALID) &&
  		    gmap_alloc_table(gmap, table, _REGION2_ENTRY_EMPTY))
  			goto out_unmap;
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + (((to + off) >> 42) & 0x7ff);
  		if ((*table & _REGION_ENTRY_INVALID) &&
  		    gmap_alloc_table(gmap, table, _REGION3_ENTRY_EMPTY))
  			goto out_unmap;
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + (((to + off) >> 31) & 0x7ff);
  		if ((*table & _REGION_ENTRY_INVALID) &&
  		    gmap_alloc_table(gmap, table, _SEGMENT_ENTRY_EMPTY))
  			goto out_unmap;
  		table = (unsigned long *) (*table & _REGION_ENTRY_ORIGIN);
  		table = table + (((to + off) >> 20) & 0x7ff);
  
  		/* Store 'from' address in an invalid segment table entry. */
  		flush |= gmap_unlink_segment(gmap, table);
  		*table =  (from + off) | (_SEGMENT_ENTRY_INVALID |
  					  _SEGMENT_ENTRY_PROTECT);
  	}
  	spin_unlock(&gmap->mm->page_table_lock);
  	up_read(&gmap->mm->mmap_sem);
  	if (flush)
  		gmap_flush_tlb(gmap);
  	return 0;
  
  out_unmap:
  	spin_unlock(&gmap->mm->page_table_lock);
  	up_read(&gmap->mm->mmap_sem);
  	gmap_unmap_segment(gmap, to, len);
  	return -ENOMEM;
  }
  EXPORT_SYMBOL_GPL(gmap_map_segment);
  
  static unsigned long *gmap_table_walk(unsigned long address, struct gmap *gmap)
  {
  	unsigned long *table;
  
  	table = gmap->table + ((address >> 53) & 0x7ff);
  	if (unlikely(*table & _REGION_ENTRY_INVALID))
  		return ERR_PTR(-EFAULT);
  	table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  	table = table + ((address >> 42) & 0x7ff);
  	if (unlikely(*table & _REGION_ENTRY_INVALID))
  		return ERR_PTR(-EFAULT);
  	table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  	table = table + ((address >> 31) & 0x7ff);
  	if (unlikely(*table & _REGION_ENTRY_INVALID))
  		return ERR_PTR(-EFAULT);
  	table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  	table = table + ((address >> 20) & 0x7ff);
  	return table;
  }
  
  /**
   * __gmap_translate - translate a guest address to a user space address
   * @address: guest address
   * @gmap: pointer to guest mapping meta data structure
   *
   * Returns user space address which corresponds to the guest address or
   * -EFAULT if no such mapping exists.
   * This function does not establish potentially missing page table entries.
   * The mmap_sem of the mm that belongs to the address space must be held
   * when this function gets called.
   */
  unsigned long __gmap_translate(unsigned long address, struct gmap *gmap)
  {
  	unsigned long *segment_ptr, vmaddr, segment;
  	struct gmap_pgtable *mp;
  	struct page *page;
  
  	current->thread.gmap_addr = address;
  	segment_ptr = gmap_table_walk(address, gmap);
  	if (IS_ERR(segment_ptr))
  		return PTR_ERR(segment_ptr);
  	/* Convert the gmap address to an mm address. */
  	segment = *segment_ptr;
  	if (!(segment & _SEGMENT_ENTRY_INVALID)) {
  		page = pfn_to_page(segment >> PAGE_SHIFT);
  		mp = (struct gmap_pgtable *) page->index;
  		return mp->vmaddr | (address & ~PMD_MASK);
  	} else if (segment & _SEGMENT_ENTRY_PROTECT) {
  		vmaddr = segment & _SEGMENT_ENTRY_ORIGIN;
  		return vmaddr | (address & ~PMD_MASK);
  	}
  	return -EFAULT;
  }
  EXPORT_SYMBOL_GPL(__gmap_translate);
  
  /**
   * gmap_translate - translate a guest address to a user space address
   * @address: guest address
   * @gmap: pointer to guest mapping meta data structure
   *
   * 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(unsigned long address, struct gmap *gmap)
  {
  	unsigned long rc;
  
  	down_read(&gmap->mm->mmap_sem);
  	rc = __gmap_translate(address, gmap);
  	up_read(&gmap->mm->mmap_sem);
  	return rc;
  }
  EXPORT_SYMBOL_GPL(gmap_translate);
  
  static int gmap_connect_pgtable(unsigned long address, unsigned long segment,
  				unsigned long *segment_ptr, struct gmap *gmap)
  {
  	unsigned long vmaddr;
  	struct vm_area_struct *vma;
  	struct gmap_pgtable *mp;
  	struct gmap_rmap *rmap;
  	struct mm_struct *mm;
  	struct page *page;
  	pgd_t *pgd;
  	pud_t *pud;
  	pmd_t *pmd;
  
  	mm = gmap->mm;
  	vmaddr = segment & _SEGMENT_ENTRY_ORIGIN;
  	vma = find_vma(mm, vmaddr);
  	if (!vma || vma->vm_start > vmaddr)
  		return -EFAULT;
  	/* Walk the parent mm page table */
  	pgd = pgd_offset(mm, vmaddr);
  	pud = pud_alloc(mm, pgd, vmaddr);
  	if (!pud)
  		return -ENOMEM;
  	pmd = pmd_alloc(mm, pud, vmaddr);
  	if (!pmd)
  		return -ENOMEM;
  	if (!pmd_present(*pmd) &&
  	    __pte_alloc(mm, vma, pmd, vmaddr))
  		return -ENOMEM;
  	/* pmd now points to a valid segment table entry. */
  	rmap = kmalloc(sizeof(*rmap), GFP_KERNEL|__GFP_REPEAT);
  	if (!rmap)
  		return -ENOMEM;
  	/* Link gmap segment table entry location to page table. */
  	page = pmd_page(*pmd);
  	mp = (struct gmap_pgtable *) page->index;
  	rmap->gmap = gmap;
  	rmap->entry = segment_ptr;
  	rmap->vmaddr = address & PMD_MASK;
  	spin_lock(&mm->page_table_lock);
  	if (*segment_ptr == segment) {
  		list_add(&rmap->list, &mp->mapper);
  		/* Set gmap segment table entry to page table. */
  		*segment_ptr = pmd_val(*pmd) & PAGE_MASK;
  		rmap = NULL;
  	}
  	spin_unlock(&mm->page_table_lock);
  	kfree(rmap);
  	return 0;
  }
  
  static void gmap_disconnect_pgtable(struct mm_struct *mm, unsigned long *table)
  {
  	struct gmap_rmap *rmap, *next;
  	struct gmap_pgtable *mp;
  	struct page *page;
  	int flush;
  
  	flush = 0;
  	spin_lock(&mm->page_table_lock);
  	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
  	mp = (struct gmap_pgtable *) page->index;
  	list_for_each_entry_safe(rmap, next, &mp->mapper, list) {
  		*rmap->entry = mp->vmaddr | (_SEGMENT_ENTRY_INVALID |
  					     _SEGMENT_ENTRY_PROTECT);
  		list_del(&rmap->list);
  		kfree(rmap);
  		flush = 1;
  	}
  	spin_unlock(&mm->page_table_lock);
  	if (flush)
  		__tlb_flush_global();
  }
  
  /*
   * this function is assumed to be called with mmap_sem held
   */
  unsigned long __gmap_fault(unsigned long address, struct gmap *gmap)
  {
  	unsigned long *segment_ptr, segment;
  	struct gmap_pgtable *mp;
  	struct page *page;
  	int rc;
  
  	current->thread.gmap_addr = address;
  	segment_ptr = gmap_table_walk(address, gmap);
  	if (IS_ERR(segment_ptr))
  		return -EFAULT;
  	/* Convert the gmap address to an mm address. */
  	while (1) {
  		segment = *segment_ptr;
  		if (!(segment & _SEGMENT_ENTRY_INVALID)) {
  			/* Page table is present */
  			page = pfn_to_page(segment >> PAGE_SHIFT);
  			mp = (struct gmap_pgtable *) page->index;
  			return mp->vmaddr | (address & ~PMD_MASK);
  		}
  		if (!(segment & _SEGMENT_ENTRY_PROTECT))
  			/* Nothing mapped in the gmap address space. */
  			break;
  		rc = gmap_connect_pgtable(address, segment, segment_ptr, gmap);
  		if (rc)
  			return rc;
  	}
  	return -EFAULT;
  }
  
  unsigned long gmap_fault(unsigned long address, struct gmap *gmap)
  {
  	unsigned long rc;
  
  	down_read(&gmap->mm->mmap_sem);
  	rc = __gmap_fault(address, gmap);
  	up_read(&gmap->mm->mmap_sem);
  
  	return rc;
  }
  EXPORT_SYMBOL_GPL(gmap_fault);
  
  void gmap_discard(unsigned long from, unsigned long to, struct gmap *gmap)
  {
  
  	unsigned long *table, address, size;
  	struct vm_area_struct *vma;
  	struct gmap_pgtable *mp;
  	struct page *page;
  
  	down_read(&gmap->mm->mmap_sem);
  	address = from;
  	while (address < to) {
  		/* Walk the gmap address space page table */
  		table = gmap->table + ((address >> 53) & 0x7ff);
  		if (unlikely(*table & _REGION_ENTRY_INVALID)) {
  			address = (address + PMD_SIZE) & PMD_MASK;
  			continue;
  		}
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + ((address >> 42) & 0x7ff);
  		if (unlikely(*table & _REGION_ENTRY_INVALID)) {
  			address = (address + PMD_SIZE) & PMD_MASK;
  			continue;
  		}
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + ((address >> 31) & 0x7ff);
  		if (unlikely(*table & _REGION_ENTRY_INVALID)) {
  			address = (address + PMD_SIZE) & PMD_MASK;
  			continue;
  		}
  		table = (unsigned long *)(*table & _REGION_ENTRY_ORIGIN);
  		table = table + ((address >> 20) & 0x7ff);
  		if (unlikely(*table & _SEGMENT_ENTRY_INVALID)) {
  			address = (address + PMD_SIZE) & PMD_MASK;
  			continue;
  		}
  		page = pfn_to_page(*table >> PAGE_SHIFT);
  		mp = (struct gmap_pgtable *) page->index;
  		vma = find_vma(gmap->mm, mp->vmaddr);
  		size = min(to - address, PMD_SIZE - (address & ~PMD_MASK));
  		zap_page_range(vma, mp->vmaddr | (address & ~PMD_MASK),
  			       size, NULL);
  		address = (address + PMD_SIZE) & PMD_MASK;
  	}
  	up_read(&gmap->mm->mmap_sem);
  }
  EXPORT_SYMBOL_GPL(gmap_discard);
  
  static LIST_HEAD(gmap_notifier_list);
  static DEFINE_SPINLOCK(gmap_notifier_lock);
  
  /**
   * gmap_register_ipte_notifier - register a pte invalidation callback
   * @nb: pointer to the gmap notifier block
   */
  void gmap_register_ipte_notifier(struct gmap_notifier *nb)
  {
  	spin_lock(&gmap_notifier_lock);
  	list_add(&nb->list, &gmap_notifier_list);
  	spin_unlock(&gmap_notifier_lock);
  }
  EXPORT_SYMBOL_GPL(gmap_register_ipte_notifier);
  
  /**
   * gmap_unregister_ipte_notifier - remove a pte invalidation callback
   * @nb: pointer to the gmap notifier block
   */
  void gmap_unregister_ipte_notifier(struct gmap_notifier *nb)
  {
  	spin_lock(&gmap_notifier_lock);
  	list_del_init(&nb->list);
  	spin_unlock(&gmap_notifier_lock);
  }
  EXPORT_SYMBOL_GPL(gmap_unregister_ipte_notifier);
  
  /**
   * gmap_ipte_notify - mark a range of ptes for invalidation notification
   * @gmap: pointer to guest mapping meta data structure
   * @address: virtual address in the guest address space
   * @len: size of area
   *
   * Returns 0 if for each page in the given range a gmap mapping exists and
   * the invalidation notification could be set. If the gmap mapping is missing
   * for one or more pages -EFAULT is returned. If no memory could be allocated
   * -ENOMEM is returned. This function establishes missing page table entries.
   */
  int gmap_ipte_notify(struct gmap *gmap, unsigned long start, unsigned long len)
  {
  	unsigned long addr;
  	spinlock_t *ptl;
  	pte_t *ptep, entry;
  	pgste_t pgste;
  	int rc = 0;
  
  	if ((start & ~PAGE_MASK) || (len & ~PAGE_MASK))
  		return -EINVAL;
  	down_read(&gmap->mm->mmap_sem);
  	while (len) {
  		/* Convert gmap address and connect the page tables */
  		addr = __gmap_fault(start, gmap);
  		if (IS_ERR_VALUE(addr)) {
  			rc = addr;
  			break;
  		}
  		/* Get the page mapped */
  		if (fixup_user_fault(current, gmap->mm, addr, FAULT_FLAG_WRITE)) {
  			rc = -EFAULT;
  			break;
  		}
  		/* Walk the process page table, lock and get pte pointer */
  		ptep = get_locked_pte(gmap->mm, addr, &ptl);
  		if (unlikely(!ptep))
  			continue;
  		/* Set notification bit in the pgste of the pte */
  		entry = *ptep;
  		if ((pte_val(entry) & (_PAGE_INVALID | _PAGE_PROTECT)) == 0) {
  			pgste = pgste_get_lock(ptep);
  			pgste_val(pgste) |= PGSTE_IN_BIT;
  			pgste_set_unlock(ptep, pgste);
  			start += PAGE_SIZE;
  			len -= PAGE_SIZE;
  		}
  		spin_unlock(ptl);
  	}
  	up_read(&gmap->mm->mmap_sem);
  	return rc;
  }
  EXPORT_SYMBOL_GPL(gmap_ipte_notify);
  
  /**
   * gmap_do_ipte_notify - call all invalidation callbacks for a specific pte.
   * @mm: pointer to the process mm_struct
   * @addr: virtual address in the process address space
   * @pte: pointer to the page table entry
   *
   * This function is assumed to be called with the page table lock held
   * for the pte to notify.
   */
  void gmap_do_ipte_notify(struct mm_struct *mm, unsigned long addr, pte_t *pte)
  {
  	unsigned long segment_offset;
  	struct gmap_notifier *nb;
  	struct gmap_pgtable *mp;
  	struct gmap_rmap *rmap;
  	struct page *page;
  
  	segment_offset = ((unsigned long) pte) & (255 * sizeof(pte_t));
  	segment_offset = segment_offset * (4096 / sizeof(pte_t));
  	page = pfn_to_page(__pa(pte) >> PAGE_SHIFT);
  	mp = (struct gmap_pgtable *) page->index;
  	spin_lock(&gmap_notifier_lock);
  	list_for_each_entry(rmap, &mp->mapper, list) {
  		list_for_each_entry(nb, &gmap_notifier_list, list)
  			nb->notifier_call(rmap->gmap,
  					  rmap->vmaddr + segment_offset);
  	}
  	spin_unlock(&gmap_notifier_lock);
  }
  
  static inline int page_table_with_pgste(struct page *page)
  {
  	return atomic_read(&page->_mapcount) == 0;
  }
  
  static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm,
  						    unsigned long vmaddr)
  {
  	struct page *page;
  	unsigned long *table;
  	struct gmap_pgtable *mp;
  
  	page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
  	if (!page)
  		return NULL;
  	mp = kmalloc(sizeof(*mp), GFP_KERNEL|__GFP_REPEAT);
  	if (!mp) {
  		__free_page(page);
  		return NULL;
  	}
  	if (!pgtable_page_ctor(page)) {
  		kfree(mp);
  		__free_page(page);
  		return NULL;
  	}
  	mp->vmaddr = vmaddr & PMD_MASK;
  	INIT_LIST_HEAD(&mp->mapper);
  	page->index = (unsigned long) mp;
  	atomic_set(&page->_mapcount, 0);
  	table = (unsigned long *) page_to_phys(page);
  	clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
  	clear_table(table + PTRS_PER_PTE, PGSTE_HR_BIT | PGSTE_HC_BIT,
  		    PAGE_SIZE/2);
  	return table;
  }
  
  static inline void page_table_free_pgste(unsigned long *table)
  {
  	struct page *page;
  	struct gmap_pgtable *mp;
  
  	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
  	mp = (struct gmap_pgtable *) page->index;
  	BUG_ON(!list_empty(&mp->mapper));
  	pgtable_page_dtor(page);
  	atomic_set(&page->_mapcount, -1);
  	kfree(mp);
  	__free_page(page);
  }
  
  int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
  			  unsigned long key, bool nq)
  {
  	spinlock_t *ptl;
  	pgste_t old, new;
  	pte_t *ptep;
  
  	down_read(&mm->mmap_sem);
  	ptep = get_locked_pte(current->mm, addr, &ptl);
  	if (unlikely(!ptep)) {
  		up_read(&mm->mmap_sem);
  		return -EFAULT;
  	}
  
  	new = old = pgste_get_lock(ptep);
  	pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |
  			    PGSTE_ACC_BITS | PGSTE_FP_BIT);
  	pgste_val(new) |= (key & (_PAGE_CHANGED | _PAGE_REFERENCED)) << 48;
  	pgste_val(new) |= (key & (_PAGE_ACC_BITS | _PAGE_FP_BIT)) << 56;
  	if (!(pte_val(*ptep) & _PAGE_INVALID)) {
  		unsigned long address, bits, skey;
  
  		address = pte_val(*ptep) & PAGE_MASK;
  		skey = (unsigned long) page_get_storage_key(address);
  		bits = skey & (_PAGE_CHANGED | _PAGE_REFERENCED);
  		skey = key & (_PAGE_ACC_BITS | _PAGE_FP_BIT);
  		/* Set storage key ACC and FP */
  		page_set_storage_key(address, skey, !nq);
  		/* Merge host changed & referenced into pgste  */
  		pgste_val(new) |= bits << 52;
  	}
  	/* changing the guest storage key is considered a change of the page */
  	if ((pgste_val(new) ^ pgste_val(old)) &
  	    (PGSTE_ACC_BITS | PGSTE_FP_BIT | PGSTE_GR_BIT | PGSTE_GC_BIT))
  		pgste_val(new) |= PGSTE_HC_BIT;
  
  	pgste_set_unlock(ptep, new);
  	pte_unmap_unlock(*ptep, ptl);
  	up_read(&mm->mmap_sem);
  	return 0;
  }
  EXPORT_SYMBOL(set_guest_storage_key);
  
  #else /* CONFIG_PGSTE */
  
  static inline int page_table_with_pgste(struct page *page)
  {
  	return 0;
  }
  
  static inline unsigned long *page_table_alloc_pgste(struct mm_struct *mm,
  						    unsigned long vmaddr)
  {
  	return NULL;
  }
  
  static inline void page_table_free_pgste(unsigned long *table)
  {
  }
  
  static inline void gmap_disconnect_pgtable(struct mm_struct *mm,
  					   unsigned long *table)
  {
  }
  
  #endif /* CONFIG_PGSTE */
  
  static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
  {
  	unsigned int old, new;
  
  	do {
  		old = atomic_read(v);
  		new = old ^ bits;
  	} while (atomic_cmpxchg(v, old, new) != old);
  	return new;
  }
  
  /*
   * page table entry allocation/free routines.
   */
  unsigned long *page_table_alloc(struct mm_struct *mm, unsigned long vmaddr)
  {
  	unsigned long *uninitialized_var(table);
  	struct page *uninitialized_var(page);
  	unsigned int mask, bit;
  
  	if (mm_has_pgste(mm))
  		return page_table_alloc_pgste(mm, vmaddr);
  	/* Allocate fragments of a 4K page as 1K/2K page table */
  	spin_lock_bh(&mm->context.list_lock);
  	mask = FRAG_MASK;
  	if (!list_empty(&mm->context.pgtable_list)) {
  		page = list_first_entry(&mm->context.pgtable_list,
  					struct page, lru);
  		table = (unsigned long *) page_to_phys(page);
  		mask = atomic_read(&page->_mapcount);
  		mask = mask | (mask >> 4);
  	}
  	if ((mask & FRAG_MASK) == FRAG_MASK) {
  		spin_unlock_bh(&mm->context.list_lock);
  		page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
  		if (!page)
  			return NULL;
  		if (!pgtable_page_ctor(page)) {
  			__free_page(page);
  			return NULL;
  		}
  		atomic_set(&page->_mapcount, 1);
  		table = (unsigned long *) page_to_phys(page);
  		clear_table(table, _PAGE_INVALID, PAGE_SIZE);
  		spin_lock_bh(&mm->context.list_lock);
  		list_add(&page->lru, &mm->context.pgtable_list);
  	} else {
  		for (bit = 1; mask & bit; bit <<= 1)
  			table += PTRS_PER_PTE;
  		mask = atomic_xor_bits(&page->_mapcount, bit);
  		if ((mask & FRAG_MASK) == FRAG_MASK)
  			list_del(&page->lru);
  	}
  	spin_unlock_bh(&mm->context.list_lock);
  	return table;
  }
  
  void page_table_free(struct mm_struct *mm, unsigned long *table)
  {
  	struct page *page;
  	unsigned int bit, mask;
  
  	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
  	if (page_table_with_pgste(page)) {
  		gmap_disconnect_pgtable(mm, table);
  		return page_table_free_pgste(table);
  	}
  	/* Free 1K/2K page table fragment of a 4K page */
  	bit = 1 << ((__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)));
  	spin_lock_bh(&mm->context.list_lock);
  	if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
  		list_del(&page->lru);
  	mask = atomic_xor_bits(&page->_mapcount, bit);
  	if (mask & FRAG_MASK)
  		list_add(&page->lru, &mm->context.pgtable_list);
  	spin_unlock_bh(&mm->context.list_lock);
  	if (mask == 0) {
  		pgtable_page_dtor(page);
  		atomic_set(&page->_mapcount, -1);
  		__free_page(page);
  	}
  }
  
  static void __page_table_free_rcu(void *table, unsigned bit)
  {
  	struct page *page;
  
  	if (bit == FRAG_MASK)
  		return page_table_free_pgste(table);
  	/* Free 1K/2K page table fragment of a 4K page */
  	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
  	if (atomic_xor_bits(&page->_mapcount, bit) == 0) {
  		pgtable_page_dtor(page);
  		atomic_set(&page->_mapcount, -1);
  		__free_page(page);
  	}
  }
  
  void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table)
  {
  	struct mm_struct *mm;
  	struct page *page;
  	unsigned int bit, mask;
  
  	mm = tlb->mm;
  	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
  	if (page_table_with_pgste(page)) {
  		gmap_disconnect_pgtable(mm, table);
  		table = (unsigned long *) (__pa(table) | FRAG_MASK);
  		tlb_remove_table(tlb, table);
  		return;
  	}
  	bit = 1 << ((__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)));
  	spin_lock_bh(&mm->context.list_lock);
  	if ((atomic_read(&page->_mapcount) & FRAG_MASK) != FRAG_MASK)
  		list_del(&page->lru);
  	mask = atomic_xor_bits(&page->_mapcount, bit | (bit << 4));
  	if (mask & FRAG_MASK)
  		list_add_tail(&page->lru, &mm->context.pgtable_list);
  	spin_unlock_bh(&mm->context.list_lock);
  	table = (unsigned long *) (__pa(table) | (bit << 4));
  	tlb_remove_table(tlb, table);
  }
  
  static void __tlb_remove_table(void *_table)
  {
  	const unsigned long mask = (FRAG_MASK << 4) | FRAG_MASK;
  	void *table = (void *)((unsigned long) _table & ~mask);
  	unsigned type = (unsigned long) _table & mask;
  
  	if (type)
  		__page_table_free_rcu(table, type);
  	else
  		free_pages((unsigned long) table, ALLOC_ORDER);
  }
  
  static void tlb_remove_table_smp_sync(void *arg)
  {
  	/* Simply deliver the interrupt */
  }
  
  static void tlb_remove_table_one(void *table)
  {
  	/*
  	 * This isn't an RCU grace period and hence the page-tables cannot be
  	 * assumed to be actually RCU-freed.
  	 *
  	 * It is however sufficient for software page-table walkers that rely
  	 * on IRQ disabling. See the comment near struct mmu_table_batch.
  	 */
  	smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
  	__tlb_remove_table(table);
  }
  
  static void tlb_remove_table_rcu(struct rcu_head *head)
  {
  	struct mmu_table_batch *batch;
  	int i;
  
  	batch = container_of(head, struct mmu_table_batch, rcu);
  
  	for (i = 0; i < batch->nr; i++)
  		__tlb_remove_table(batch->tables[i]);
  
  	free_page((unsigned long)batch);
  }
  
  void tlb_table_flush(struct mmu_gather *tlb)
  {
  	struct mmu_table_batch **batch = &tlb->batch;
  
  	if (*batch) {
  		call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
  		*batch = NULL;
  	}
  }
  
  void tlb_remove_table(struct mmu_gather *tlb, void *table)
  {
  	struct mmu_table_batch **batch = &tlb->batch;
  
  	tlb->mm->context.flush_mm = 1;
  	if (*batch == NULL) {
  		*batch = (struct mmu_table_batch *)
  			__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
  		if (*batch == NULL) {
  			__tlb_flush_mm_lazy(tlb->mm);
  			tlb_remove_table_one(table);
  			return;
  		}
  		(*batch)->nr = 0;
  	}
  	(*batch)->tables[(*batch)->nr++] = table;
  	if ((*batch)->nr == MAX_TABLE_BATCH)
  		tlb_flush_mmu(tlb);
  }
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  static inline void thp_split_vma(struct vm_area_struct *vma)
  {
  	unsigned long addr;
  
  	for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE)
  		follow_page(vma, addr, FOLL_SPLIT);
  }
  
  static inline void thp_split_mm(struct mm_struct *mm)
  {
  	struct vm_area_struct *vma;
  
  	for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
  		thp_split_vma(vma);
  		vma->vm_flags &= ~VM_HUGEPAGE;
  		vma->vm_flags |= VM_NOHUGEPAGE;
  	}
  	mm->def_flags |= VM_NOHUGEPAGE;
  }
  #else
  static inline void thp_split_mm(struct mm_struct *mm)
  {
  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  
  static unsigned long page_table_realloc_pmd(struct mmu_gather *tlb,
  				struct mm_struct *mm, pud_t *pud,
  				unsigned long addr, unsigned long end)
  {
  	unsigned long next, *table, *new;
  	struct page *page;
  	pmd_t *pmd;
  
  	pmd = pmd_offset(pud, addr);
  	do {
  		next = pmd_addr_end(addr, end);
  again:
  		if (pmd_none_or_clear_bad(pmd))
  			continue;
  		table = (unsigned long *) pmd_deref(*pmd);
  		page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
  		if (page_table_with_pgste(page))
  			continue;
  		/* Allocate new page table with pgstes */
  		new = page_table_alloc_pgste(mm, addr);
  		if (!new)
  			return -ENOMEM;
  
  		spin_lock(&mm->page_table_lock);
  		if (likely((unsigned long *) pmd_deref(*pmd) == table)) {
  			/* Nuke pmd entry pointing to the "short" page table */
  			pmdp_flush_lazy(mm, addr, pmd);
  			pmd_clear(pmd);
  			/* Copy ptes from old table to new table */
  			memcpy(new, table, PAGE_SIZE/2);
  			clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
  			/* Establish new table */
  			pmd_populate(mm, pmd, (pte_t *) new);
  			/* Free old table with rcu, there might be a walker! */
  			page_table_free_rcu(tlb, table);
  			new = NULL;
  		}
  		spin_unlock(&mm->page_table_lock);
  		if (new) {
  			page_table_free_pgste(new);
  			goto again;
  		}
  	} while (pmd++, addr = next, addr != end);
  
  	return addr;
  }
  
  static unsigned long page_table_realloc_pud(struct mmu_gather *tlb,
  				   struct mm_struct *mm, pgd_t *pgd,
  				   unsigned long addr, unsigned long end)
  {
  	unsigned long next;
  	pud_t *pud;
  
  	pud = pud_offset(pgd, addr);
  	do {
  		next = pud_addr_end(addr, end);
  		if (pud_none_or_clear_bad(pud))
  			continue;
  		next = page_table_realloc_pmd(tlb, mm, pud, addr, next);
  		if (unlikely(IS_ERR_VALUE(next)))
  			return next;
  	} while (pud++, addr = next, addr != end);
  
  	return addr;
  }
  
  static unsigned long page_table_realloc(struct mmu_gather *tlb, struct mm_struct *mm,
  					unsigned long addr, unsigned long end)
  {
  	unsigned long next;
  	pgd_t *pgd;
  
  	pgd = pgd_offset(mm, addr);
  	do {
  		next = pgd_addr_end(addr, end);
  		if (pgd_none_or_clear_bad(pgd))
  			continue;
  		next = page_table_realloc_pud(tlb, mm, pgd, addr, next);
  		if (unlikely(IS_ERR_VALUE(next)))
  			return next;
  	} while (pgd++, addr = next, addr != end);
  
  	return 0;
  }
  
  /*
   * switch on pgstes for its userspace process (for kvm)
   */
  int s390_enable_sie(void)
  {
  	struct task_struct *tsk = current;
  	struct mm_struct *mm = tsk->mm;
  	struct mmu_gather tlb;
  
  	/* Do we have pgstes? if yes, we are done */
  	if (mm_has_pgste(tsk->mm))
  		return 0;
  
  	down_write(&mm->mmap_sem);
  	/* split thp mappings and disable thp for future mappings */
  	thp_split_mm(mm);
  	/* Reallocate the page tables with pgstes */
  	tlb_gather_mmu(&tlb, mm, 0, TASK_SIZE);
  	if (!page_table_realloc(&tlb, mm, 0, TASK_SIZE))
  		mm->context.has_pgste = 1;
  	tlb_finish_mmu(&tlb, 0, TASK_SIZE);
  	up_write(&mm->mmap_sem);
  	return mm->context.has_pgste ? 0 : -ENOMEM;
  }
  EXPORT_SYMBOL_GPL(s390_enable_sie);
  
  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
  int pmdp_clear_flush_young(struct vm_area_struct *vma, unsigned long address,
  			   pmd_t *pmdp)
  {
  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
  	/* No need to flush TLB
  	 * On s390 reference bits are in storage key and never in TLB */
  	return pmdp_test_and_clear_young(vma, address, pmdp);
  }
  
  int pmdp_set_access_flags(struct vm_area_struct *vma,
  			  unsigned long address, pmd_t *pmdp,
  			  pmd_t entry, int dirty)
  {
  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
  
  	if (pmd_same(*pmdp, entry))
  		return 0;
  	pmdp_invalidate(vma, address, pmdp);
  	set_pmd_at(vma->vm_mm, address, pmdp, entry);
  	return 1;
  }
  
  static void pmdp_splitting_flush_sync(void *arg)
  {
  	/* Simply deliver the interrupt */
  }
  
  void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
  			  pmd_t *pmdp)
  {
  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
  	if (!test_and_set_bit(_SEGMENT_ENTRY_SPLIT_BIT,
  			      (unsigned long *) pmdp)) {
  		/* need to serialize against gup-fast (IRQ disabled) */
  		smp_call_function(pmdp_splitting_flush_sync, NULL, 1);
  	}
  }
  
  void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
  				pgtable_t pgtable)
  {
  	struct list_head *lh = (struct list_head *) pgtable;
  
  	assert_spin_locked(&mm->page_table_lock);
  
  	/* FIFO */
  	if (!pmd_huge_pte(mm, pmdp))
  		INIT_LIST_HEAD(lh);
  	else
  		list_add(lh, (struct list_head *) pmd_huge_pte(mm, pmdp));
  	pmd_huge_pte(mm, pmdp) = pgtable;
  }
  
  pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
  {
  	struct list_head *lh;
  	pgtable_t pgtable;
  	pte_t *ptep;
  
  	assert_spin_locked(&mm->page_table_lock);
  
  	/* FIFO */
  	pgtable = pmd_huge_pte(mm, pmdp);
  	lh = (struct list_head *) pgtable;
  	if (list_empty(lh))
  		pmd_huge_pte(mm, pmdp) = NULL;
  	else {
  		pmd_huge_pte(mm, pmdp) = (pgtable_t) lh->next;
  		list_del(lh);
  	}
  	ptep = (pte_t *) pgtable;
  	pte_val(*ptep) = _PAGE_INVALID;
  	ptep++;
  	pte_val(*ptep) = _PAGE_INVALID;
  	return pgtable;
  }
  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
  