arch/s390/mm/pgtable.c - kernel/msm-4.19 - Gitiles

 /*
  *    Copyright IBM Corp. 2007,2009
  *    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 <asm/system.h>
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
 #include <asm/tlb.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>

 struct rcu_table_freelist {
 	struct rcu_head rcu;
 	struct mm_struct *mm;
 	unsigned int pgt_index;
 	unsigned int crst_index;
 	unsigned long *table[0];
 };

 #define RCU_FREELIST_SIZE \
 	((PAGE_SIZE - sizeof(struct rcu_table_freelist)) \
 	  / sizeof(unsigned long))

 static DEFINE_PER_CPU(struct rcu_table_freelist *, rcu_table_freelist);

 static void __page_table_free(struct mm_struct *mm, unsigned long *table);

 static struct rcu_table_freelist *rcu_table_freelist_get(struct mm_struct *mm)
 {
 	struct rcu_table_freelist **batchp = &__get_cpu_var(rcu_table_freelist);
 	struct rcu_table_freelist *batch = *batchp;

 	if (batch)
 		return batch;
 	batch = (struct rcu_table_freelist *) __get_free_page(GFP_ATOMIC);
 	if (batch) {
 		batch->mm = mm;
 		batch->pgt_index = 0;
 		batch->crst_index = RCU_FREELIST_SIZE;
 		*batchp = batch;
 	}
 	return batch;
 }

 static void rcu_table_freelist_callback(struct rcu_head *head)
 {
 	struct rcu_table_freelist *batch =
 		container_of(head, struct rcu_table_freelist, rcu);

 	while (batch->pgt_index > 0)
 		__page_table_free(batch->mm, batch->table[--batch->pgt_index]);
 	while (batch->crst_index < RCU_FREELIST_SIZE)
 		crst_table_free(batch->mm, batch->table[batch->crst_index++]);
 	free_page((unsigned long) batch);
 }

 void rcu_table_freelist_finish(void)
 {
 	struct rcu_table_freelist **batchp = &get_cpu_var(rcu_table_freelist);
 	struct rcu_table_freelist *batch = *batchp;

 	if (!batch)
 		goto out;
 	call_rcu(&batch->rcu, rcu_table_freelist_callback);
 	*batchp = NULL;
 out:
 	put_cpu_var(rcu_table_freelist);
 }

 static void smp_sync(void *arg)
 {
 }

 #ifndef CONFIG_64BIT
 #define ALLOC_ORDER	1
 #define TABLES_PER_PAGE	4
 #define FRAG_MASK	15UL
 #define SECOND_HALVES	10UL

 void clear_table_pgstes(unsigned long *table)
 {
 	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
 	memset(table + 256, 0, PAGE_SIZE/4);
 	clear_table(table + 512, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
 	memset(table + 768, 0, PAGE_SIZE/4);
 }

 #else
 #define ALLOC_ORDER	2
 #define TABLES_PER_PAGE	2
 #define FRAG_MASK	3UL
 #define SECOND_HALVES	2UL

 void clear_table_pgstes(unsigned long *table)
 {
 	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
 	memset(table + 256, 0, PAGE_SIZE/2);
 }

 #endif

 unsigned long VMALLOC_START = VMALLOC_END - VMALLOC_SIZE;
 EXPORT_SYMBOL(VMALLOC_START);

 static int __init parse_vmalloc(char *arg)
 {
 	if (!arg)
 		return -EINVAL;
 	VMALLOC_START = (VMALLOC_END - memparse(arg, &arg)) & PAGE_MASK;
 	return 0;
 }
 early_param("vmalloc", parse_vmalloc);

 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);
 }

 void crst_table_free_rcu(struct mm_struct *mm, unsigned long *table)
 {
 	struct rcu_table_freelist *batch;

 	preempt_disable();
 	if (atomic_read(&mm->mm_users) < 2 &&
 	    cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
 		crst_table_free(mm, table);
 		goto out;
 	}
 	batch = rcu_table_freelist_get(mm);
 	if (!batch) {
 		smp_call_function(smp_sync, NULL, 1);
 		crst_table_free(mm, table);
 		goto out;
 	}
 	batch->table[--batch->crst_index] = table;
 	if (batch->pgt_index >= batch->crst_index)
 		rcu_table_freelist_finish();
 out:
 	preempt_enable();
 }

 #ifdef CONFIG_64BIT
 int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
 {
 	unsigned long *table, *pgd;
 	unsigned long entry;

 	BUG_ON(limit > (1UL << 53));
 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;
 	}
 	spin_unlock_bh(&mm->page_table_lock);
 	if (table)
 		crst_table_free(mm, table);
 	if (mm->context.asce_limit < limit)
 		goto repeat;
 	update_mm(mm, current);
 	return 0;
 }

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

 	if (mm->context.asce_limit <= limit)
 		return;
 	__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);
 	}
 	update_mm(mm, current);
 }
 #endif

 /*
  * page table entry allocation/free routines.
  */
 unsigned long *page_table_alloc(struct mm_struct *mm)
 {
 	struct page *page;
 	unsigned long *table;
 	unsigned long bits;

 	bits = (mm->context.has_pgste) ? 3UL : 1UL;
 	spin_lock_bh(&mm->context.list_lock);
 	page = NULL;
 	if (!list_empty(&mm->context.pgtable_list)) {
 		page = list_first_entry(&mm->context.pgtable_list,
 					struct page, lru);
 		if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
 			page = NULL;
 	}
 	if (!page) {
 		spin_unlock_bh(&mm->context.list_lock);
 		page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
 		if (!page)
 			return NULL;
 		pgtable_page_ctor(page);
 		page->flags &= ~FRAG_MASK;
 		table = (unsigned long *) page_to_phys(page);
 		if (mm->context.has_pgste)
 			clear_table_pgstes(table);
 		else
 			clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
 		spin_lock_bh(&mm->context.list_lock);
 		list_add(&page->lru, &mm->context.pgtable_list);
 	}
 	table = (unsigned long *) page_to_phys(page);
 	while (page->flags & bits) {
 		table += 256;
 		bits <<= 1;
 	}
 	page->flags |= bits;
 	if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
 		list_move_tail(&page->lru, &mm->context.pgtable_list);
 	spin_unlock_bh(&mm->context.list_lock);
 	return table;
 }

 static void __page_table_free(struct mm_struct *mm, unsigned long *table)
 {
 	struct page *page;
 	unsigned long bits;

 	bits = ((unsigned long) table) & 15;
 	table = (unsigned long *)(((unsigned long) table) ^ bits);
 	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 	page->flags ^= bits;
 	if (!(page->flags & FRAG_MASK)) {
 		pgtable_page_dtor(page);
 		__free_page(page);
 	}
 }

 void page_table_free(struct mm_struct *mm, unsigned long *table)
 {
 	struct page *page;
 	unsigned long bits;

 	bits = (mm->context.has_pgste) ? 3UL : 1UL;
 	bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
 	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 	spin_lock_bh(&mm->context.list_lock);
 	page->flags ^= bits;
 	if (page->flags & FRAG_MASK) {
 		/* Page now has some free pgtable fragments. */
 		if (!list_empty(&page->lru))
 			list_move(&page->lru, &mm->context.pgtable_list);
 		page = NULL;
 	} else
 		/* All fragments of the 4K page have been freed. */
 		list_del(&page->lru);
 	spin_unlock_bh(&mm->context.list_lock);
 	if (page) {
 		pgtable_page_dtor(page);
 		__free_page(page);
 	}
 }

 void page_table_free_rcu(struct mm_struct *mm, unsigned long *table)
 {
 	struct rcu_table_freelist *batch;
 	struct page *page;
 	unsigned long bits;

 	preempt_disable();
 	if (atomic_read(&mm->mm_users) < 2 &&
 	    cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
 		page_table_free(mm, table);
 		goto out;
 	}
 	batch = rcu_table_freelist_get(mm);
 	if (!batch) {
 		smp_call_function(smp_sync, NULL, 1);
 		page_table_free(mm, table);
 		goto out;
 	}
 	bits = (mm->context.has_pgste) ? 3UL : 1UL;
 	bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
 	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 	spin_lock_bh(&mm->context.list_lock);
 	/* Delayed freeing with rcu prevents reuse of pgtable fragments */
 	list_del_init(&page->lru);
 	spin_unlock_bh(&mm->context.list_lock);
 	table = (unsigned long *)(((unsigned long) table) | bits);
 	batch->table[batch->pgt_index++] = table;
 	if (batch->pgt_index >= batch->crst_index)
 		rcu_table_freelist_finish();
 out:
 	preempt_enable();
 }

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

 	/* Do we have switched amode? If no, we cannot do sie */
 	if (user_mode == HOME_SPACE_MODE)
 		return -EINVAL;

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

 	/* lets check if we are allowed to replace the mm */
 	task_lock(tsk);
 	if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
 #ifdef CONFIG_AIO
 	    !hlist_empty(&tsk->mm->ioctx_list) ||
 #endif
 	    tsk->mm != tsk->active_mm) {
 		task_unlock(tsk);
 		return -EINVAL;
 	}
 	task_unlock(tsk);

 	/* we copy the mm and let dup_mm create the page tables with_pgstes */
 	tsk->mm->context.alloc_pgste = 1;
 	mm = dup_mm(tsk);
 	tsk->mm->context.alloc_pgste = 0;
 	if (!mm)
 		return -ENOMEM;

 	/* Now lets check again if something happened */
 	task_lock(tsk);
 	if (!tsk->mm || atomic_read(&tsk->mm->mm_users) > 1 ||
 #ifdef CONFIG_AIO
 	    !hlist_empty(&tsk->mm->ioctx_list) ||
 #endif
 	    tsk->mm != tsk->active_mm) {
 		mmput(mm);
 		task_unlock(tsk);
 		return -EINVAL;
 	}

 	/* ok, we are alone. No ptrace, no threads, etc. */
 	old_mm = tsk->mm;
 	tsk->mm = tsk->active_mm = mm;
 	preempt_disable();
 	update_mm(mm, tsk);
 	atomic_inc(&mm->context.attach_count);
 	atomic_dec(&old_mm->context.attach_count);
 	cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
 	preempt_enable();
 	task_unlock(tsk);
 	mmput(old_mm);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(s390_enable_sie);

 #if defined(CONFIG_DEBUG_PAGEALLOC) && defined(CONFIG_HIBERNATION)
 bool kernel_page_present(struct page *page)
 {
 	unsigned long addr;
 	int cc;

 	addr = page_to_phys(page);
 	asm volatile(
 		"	lra	%1,0(%1)\n"
 		"	ipm	%0\n"
 		"	srl	%0,28"
 		: "=d" (cc), "+a" (addr) : : "cc");
 	return cc == 0;
 }
 #endif /* CONFIG_HIBERNATION && CONFIG_DEBUG_PAGEALLOC */
	/*
	* Copyright IBM Corp. 2007,2009
	* 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 <asm/system.h>
	#include <asm/pgtable.h>
	#include <asm/pgalloc.h>
	#include <asm/tlb.h>
	#include <asm/tlbflush.h>
	#include <asm/mmu_context.h>

	struct rcu_table_freelist {
	struct rcu_head rcu;
	struct mm_struct *mm;
	unsigned int pgt_index;
	unsigned int crst_index;
	unsigned long *table[0];
	};

	#define RCU_FREELIST_SIZE \
	((PAGE_SIZE - sizeof(struct rcu_table_freelist)) \
	/ sizeof(unsigned long))

	static DEFINE_PER_CPU(struct rcu_table_freelist *, rcu_table_freelist);

	static void __page_table_free(struct mm_struct mm, unsigned long table);

	static struct rcu_table_freelist rcu_table_freelist_get(struct mm_struct mm)
	{
	struct rcu_table_freelist **batchp = &__get_cpu_var(rcu_table_freelist);
	struct rcu_table_freelist batch = batchp;

	if (batch)
	return batch;
	batch = (struct rcu_table_freelist *) __get_free_page(GFP_ATOMIC);
	if (batch) {
	batch->mm = mm;
	batch->pgt_index = 0;
	batch->crst_index = RCU_FREELIST_SIZE;
	*batchp = batch;
	}
	return batch;
	}

	static void rcu_table_freelist_callback(struct rcu_head *head)
	{
	struct rcu_table_freelist *batch =
	container_of(head, struct rcu_table_freelist, rcu);

	while (batch->pgt_index > 0)
	__page_table_free(batch->mm, batch->table[--batch->pgt_index]);
	while (batch->crst_index < RCU_FREELIST_SIZE)
	crst_table_free(batch->mm, batch->table[batch->crst_index++]);
	free_page((unsigned long) batch);
	}

	void rcu_table_freelist_finish(void)
	{
	struct rcu_table_freelist **batchp = &get_cpu_var(rcu_table_freelist);
	struct rcu_table_freelist batch = batchp;

	if (!batch)
	goto out;
	call_rcu(&batch->rcu, rcu_table_freelist_callback);
	*batchp = NULL;
	out:
	put_cpu_var(rcu_table_freelist);
	}

	static void smp_sync(void *arg)
	{
	}

	#ifndef CONFIG_64BIT
	#define ALLOC_ORDER 1
	#define TABLES_PER_PAGE 4
	#define FRAG_MASK 15UL
	#define SECOND_HALVES 10UL

	void clear_table_pgstes(unsigned long *table)
	{
	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
	memset(table + 256, 0, PAGE_SIZE/4);
	clear_table(table + 512, _PAGE_TYPE_EMPTY, PAGE_SIZE/4);
	memset(table + 768, 0, PAGE_SIZE/4);
	}

	#else
	#define ALLOC_ORDER 2
	#define TABLES_PER_PAGE 2
	#define FRAG_MASK 3UL
	#define SECOND_HALVES 2UL

	void clear_table_pgstes(unsigned long *table)
	{
	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE/2);
	memset(table + 256, 0, PAGE_SIZE/2);
	}

	#endif

	unsigned long VMALLOC_START = VMALLOC_END - VMALLOC_SIZE;
	EXPORT_SYMBOL(VMALLOC_START);

	static int __init parse_vmalloc(char *arg)
	{
	if (!arg)
	return -EINVAL;
	VMALLOC_START = (VMALLOC_END - memparse(arg, &arg)) & PAGE_MASK;
	return 0;
	}
	early_param("vmalloc", parse_vmalloc);

	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);
	}

	void crst_table_free_rcu(struct mm_struct mm, unsigned long table)
	{
	struct rcu_table_freelist *batch;

	preempt_disable();
	if (atomic_read(&mm->mm_users) < 2 &&
	cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
	crst_table_free(mm, table);
	goto out;
	}
	batch = rcu_table_freelist_get(mm);
	if (!batch) {
	smp_call_function(smp_sync, NULL, 1);
	crst_table_free(mm, table);
	goto out;
	}
	batch->table[--batch->crst_index] = table;
	if (batch->pgt_index >= batch->crst_index)
	rcu_table_freelist_finish();
	out:
	preempt_enable();
	}

	#ifdef CONFIG_64BIT
	int crst_table_upgrade(struct mm_struct *mm, unsigned long limit)
	{
	unsigned long table, pgd;
	unsigned long entry;

	BUG_ON(limit > (1UL << 53));
	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;
	}
	spin_unlock_bh(&mm->page_table_lock);
	if (table)
	crst_table_free(mm, table);
	if (mm->context.asce_limit < limit)
	goto repeat;
	update_mm(mm, current);
	return 0;
	}

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

	if (mm->context.asce_limit <= limit)
	return;
	__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);
	}
	update_mm(mm, current);
	}
	#endif

	/*
	* page table entry allocation/free routines.
	*/
	unsigned long page_table_alloc(struct mm_struct mm)
	{
	struct page *page;
	unsigned long *table;
	unsigned long bits;

	bits = (mm->context.has_pgste) ? 3UL : 1UL;
	spin_lock_bh(&mm->context.list_lock);
	page = NULL;
	if (!list_empty(&mm->context.pgtable_list)) {
	page = list_first_entry(&mm->context.pgtable_list,
	struct page, lru);
	if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
	page = NULL;
	}
	if (!page) {
	spin_unlock_bh(&mm->context.list_lock);
	page = alloc_page(GFP_KERNEL\|__GFP_REPEAT);
	if (!page)
	return NULL;
	pgtable_page_ctor(page);
	page->flags &= ~FRAG_MASK;
	table = (unsigned long *) page_to_phys(page);
	if (mm->context.has_pgste)
	clear_table_pgstes(table);
	else
	clear_table(table, _PAGE_TYPE_EMPTY, PAGE_SIZE);
	spin_lock_bh(&mm->context.list_lock);
	list_add(&page->lru, &mm->context.pgtable_list);
	}
	table = (unsigned long *) page_to_phys(page);
	while (page->flags & bits) {
	table += 256;
	bits <<= 1;
	}
	page->flags \|= bits;
	if ((page->flags & FRAG_MASK) == ((1UL << TABLES_PER_PAGE) - 1))
	list_move_tail(&page->lru, &mm->context.pgtable_list);
	spin_unlock_bh(&mm->context.list_lock);
	return table;
	}

	static void __page_table_free(struct mm_struct mm, unsigned long table)
	{
	struct page *page;
	unsigned long bits;

	bits = ((unsigned long) table) & 15;
	table = (unsigned long *)(((unsigned long) table) ^ bits);
	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
	page->flags ^= bits;
	if (!(page->flags & FRAG_MASK)) {
	pgtable_page_dtor(page);
	__free_page(page);
	}
	}

	void page_table_free(struct mm_struct mm, unsigned long table)
	{
	struct page *page;
	unsigned long bits;

	bits = (mm->context.has_pgste) ? 3UL : 1UL;
	bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
	spin_lock_bh(&mm->context.list_lock);
	page->flags ^= bits;
	if (page->flags & FRAG_MASK) {
	/* Page now has some free pgtable fragments. */
	if (!list_empty(&page->lru))
	list_move(&page->lru, &mm->context.pgtable_list);
	page = NULL;
	} else
	/* All fragments of the 4K page have been freed. */
	list_del(&page->lru);
	spin_unlock_bh(&mm->context.list_lock);
	if (page) {
	pgtable_page_dtor(page);
	__free_page(page);
	}
	}

	void page_table_free_rcu(struct mm_struct mm, unsigned long table)
	{
	struct rcu_table_freelist *batch;
	struct page *page;
	unsigned long bits;

	preempt_disable();
	if (atomic_read(&mm->mm_users) < 2 &&
	cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
	page_table_free(mm, table);
	goto out;
	}
	batch = rcu_table_freelist_get(mm);
	if (!batch) {
	smp_call_function(smp_sync, NULL, 1);
	page_table_free(mm, table);
	goto out;
	}
	bits = (mm->context.has_pgste) ? 3UL : 1UL;
	bits <<= (__pa(table) & (PAGE_SIZE - 1)) / 256 / sizeof(unsigned long);
	page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
	spin_lock_bh(&mm->context.list_lock);
	/* Delayed freeing with rcu prevents reuse of pgtable fragments */
	list_del_init(&page->lru);
	spin_unlock_bh(&mm->context.list_lock);
	table = (unsigned long *)(((unsigned long) table) \| bits);
	batch->table[batch->pgt_index++] = table;
	if (batch->pgt_index >= batch->crst_index)
	rcu_table_freelist_finish();
	out:
	preempt_enable();
	}

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

	/* Do we have switched amode? If no, we cannot do sie */
	if (user_mode == HOME_SPACE_MODE)
	return -EINVAL;

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

	/* lets check if we are allowed to replace the mm */
	task_lock(tsk);
	if (!tsk->mm \|\| atomic_read(&tsk->mm->mm_users) > 1 \|\|
	#ifdef CONFIG_AIO
	!hlist_empty(&tsk->mm->ioctx_list) \|\|
	#endif
	tsk->mm != tsk->active_mm) {
	task_unlock(tsk);
	return -EINVAL;
	}
	task_unlock(tsk);

	/* we copy the mm and let dup_mm create the page tables with_pgstes */
	tsk->mm->context.alloc_pgste = 1;
	mm = dup_mm(tsk);
	tsk->mm->context.alloc_pgste = 0;
	if (!mm)
	return -ENOMEM;

	/* Now lets check again if something happened */
	task_lock(tsk);
	if (!tsk->mm \|\| atomic_read(&tsk->mm->mm_users) > 1 \|\|
	#ifdef CONFIG_AIO
	!hlist_empty(&tsk->mm->ioctx_list) \|\|
	#endif
	tsk->mm != tsk->active_mm) {
	mmput(mm);
	task_unlock(tsk);
	return -EINVAL;
	}

	/* ok, we are alone. No ptrace, no threads, etc. */
	old_mm = tsk->mm;
	tsk->mm = tsk->active_mm = mm;
	preempt_disable();
	update_mm(mm, tsk);
	atomic_inc(&mm->context.attach_count);
	atomic_dec(&old_mm->context.attach_count);
	cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
	preempt_enable();
	task_unlock(tsk);
	mmput(old_mm);
	return 0;
	}
	EXPORT_SYMBOL_GPL(s390_enable_sie);

	#if defined(CONFIG_DEBUG_PAGEALLOC) && defined(CONFIG_HIBERNATION)
	bool kernel_page_present(struct page *page)
	{
	unsigned long addr;
	int cc;

	addr = page_to_phys(page);
	asm volatile(
	" lra %1,0(%1)\n"
	" ipm %0\n"
	" srl %0,28"
	: "=d" (cc), "+a" (addr) : : "cc");
	return cc == 0;
	}
	#endif /* CONFIG_HIBERNATION && CONFIG_DEBUG_PAGEALLOC */