path: root/arch/powerpc/include/asm/pgtable-ppc64.h

#ifndef _ASM_POWERPC_PGTABLE_PPC64_H_
#define _ASM_POWERPC_PGTABLE_PPC64_H_
/*
 * This file contains the functions and defines necessary to modify and use
 * the ppc64 hashed page table.
 */

#ifdef CONFIG_PPC_64K_PAGES
#include <asm/pgtable-ppc64-64k.h>
#else
#include <asm/pgtable-ppc64-4k.h>
#endif
#include <asm/barrier.h>

#define FIRST_USER_ADDRESS	0UL

/*
 * Size of EA range mapped by our pagetables.
 */
#define PGTABLE_EADDR_SIZE (PTE_INDEX_SIZE + PMD_INDEX_SIZE + \
                	    PUD_INDEX_SIZE + PGD_INDEX_SIZE + PAGE_SHIFT)
#define PGTABLE_RANGE (ASM_CONST(1) << PGTABLE_EADDR_SIZE)

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
#define PMD_CACHE_INDEX	(PMD_INDEX_SIZE + 1)
#else
#define PMD_CACHE_INDEX	PMD_INDEX_SIZE
#endif
/*
 * Define the address range of the kernel non-linear virtual area
 */

#ifdef CONFIG_PPC_BOOK3E
#define KERN_VIRT_START ASM_CONST(0x8000000000000000)
#else
#define KERN_VIRT_START ASM_CONST(0xD000000000000000)
#endif
#define KERN_VIRT_SIZE	ASM_CONST(0x0000100000000000)

/*
 * The vmalloc space starts at the beginning of that region, and
 * occupies half of it on hash CPUs and a quarter of it on Book3E
 * (we keep a quarter for the virtual memmap)
 */
#define VMALLOC_START	KERN_VIRT_START
#ifdef CONFIG_PPC_BOOK3E
#define VMALLOC_SIZE	(KERN_VIRT_SIZE >> 2)
#else
#define VMALLOC_SIZE	(KERN_VIRT_SIZE >> 1)
#endif
#define VMALLOC_END	(VMALLOC_START + VMALLOC_SIZE)

/*
 * The second half of the kernel virtual space is used for IO mappings,
 * it's itself carved into the PIO region (ISA and PHB IO space) and
 * the ioremap space
 *
 *  ISA_IO_BASE = KERN_IO_START, 64K reserved area
 *  PHB_IO_BASE = ISA_IO_BASE + 64K to ISA_IO_BASE + 2G, PHB IO spaces
 * IOREMAP_BASE = ISA_IO_BASE + 2G to VMALLOC_START + PGTABLE_RANGE
 */
#define KERN_IO_START	(KERN_VIRT_START + (KERN_VIRT_SIZE >> 1))
#define FULL_IO_SIZE	0x80000000ul
#define  ISA_IO_BASE	(KERN_IO_START)
#define  ISA_IO_END	(KERN_IO_START + 0x10000ul)
#define  PHB_IO_BASE	(ISA_IO_END)
#define  PHB_IO_END	(KERN_IO_START + FULL_IO_SIZE)
#define IOREMAP_BASE	(PHB_IO_END)
#define IOREMAP_END	(KERN_VIRT_START + KERN_VIRT_SIZE)


/*
 * Region IDs
 */
#define REGION_SHIFT		60UL
#define REGION_MASK		(0xfUL << REGION_SHIFT)
#define REGION_ID(ea)		(((unsigned long)(ea)) >> REGION_SHIFT)

#define VMALLOC_REGION_ID	(REGION_ID(VMALLOC_START))
#define KERNEL_REGION_ID	(REGION_ID(PAGE_OFFSET))
#define VMEMMAP_REGION_ID	(0xfUL)	/* Server only */
#define USER_REGION_ID		(0UL)

/*
 * Defines the address of the vmemap area, in its own region on
 * hash table CPUs and after the vmalloc space on Book3E
 */
#ifdef CONFIG_PPC_BOOK3E
#define VMEMMAP_BASE		VMALLOC_END
#define VMEMMAP_END		KERN_IO_START
#else
#define VMEMMAP_BASE		(VMEMMAP_REGION_ID << REGION_SHIFT)
#endif
#define vmemmap			((struct page *)VMEMMAP_BASE)


/*
 * Include the PTE bits definitions
 */
#ifdef CONFIG_PPC_BOOK3S
#include <asm/pte-hash64.h>
#else
#include <asm/pte-book3e.h>
#endif
#include <asm/pte-common.h>

#ifdef CONFIG_PPC_MM_SLICES
#define HAVE_ARCH_UNMAPPED_AREA
#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
#endif /* CONFIG_PPC_MM_SLICES */

#ifndef __ASSEMBLY__

/*
 * This is the default implementation of various PTE accessors, it's
 * used in all cases except Book3S with 64K pages where we have a
 * concept of sub-pages
 */
#ifndef __real_pte

#ifdef CONFIG_STRICT_MM_TYPECHECKS
#define __real_pte(e,p)		((real_pte_t){(e)})
#define __rpte_to_pte(r)	((r).pte)
#else
#define __real_pte(e,p)		(e)
#define __rpte_to_pte(r)	(__pte(r))
#endif
#define __rpte_to_hidx(r,index)	(pte_val(__rpte_to_pte(r)) >> 12)

#define pte_iterate_hashed_subpages(rpte, psize, va, index, shift)       \
	do {							         \
		index = 0;					         \
		shift = mmu_psize_defs[psize].shift;		         \

#define pte_iterate_hashed_end() } while(0)

#ifdef CONFIG_PPC_HAS_HASH_64K
#define pte_pagesize_index(mm, addr, pte)	get_slice_psize(mm, addr)
#else
#define pte_pagesize_index(mm, addr, pte)	MMU_PAGE_4K
#endif

#endif /* __real_pte */


/* pte_clear moved to later in this file */

#define PMD_BAD_BITS		(PTE_TABLE_SIZE-1)
#define PUD_BAD_BITS		(PMD_TABLE_SIZE-1)

#define pmd_set(pmdp, pmdval) 	(pmd_val(*(pmdp)) = (pmdval))
#define pmd_none(pmd)		(!pmd_val(pmd))
#define	pmd_bad(pmd)		(!is_kernel_addr(pmd_val(pmd)) \
				 || (pmd_val(pmd) & PMD_BAD_BITS))
#define	pmd_present(pmd)	(!pmd_none(pmd))
#define	pmd_clear(pmdp)		(pmd_val(*(pmdp)) = 0)
#define pmd_page_vaddr(pmd)	(pmd_val(pmd) & ~PMD_MASKED_BITS)
extern struct page *pmd_page(pmd_t pmd);

#define pud_set(pudp, pudval)	(pud_val(*(pudp)) = (pudval))
#define pud_none(pud)		(!pud_val(pud))
#define	pud_bad(pud)		(!is_kernel_addr(pud_val(pud)) \
				 || (pud_val(pud) & PUD_BAD_BITS))
#define pud_present(pud)	(pud_val(pud) != 0)
#define pud_clear(pudp)		(pud_val(*(pudp)) = 0)
#define pud_page_vaddr(pud)	(pud_val(pud) & ~PUD_MASKED_BITS)

extern struct page *pud_page(pud_t pud);

static inline pte_t pud_pte(pud_t pud)
{
	return __pte(pud_val(pud));
}

static inline pud_t pte_pud(pte_t pte)
{
	return __pud(pte_val(pte));
}
#define pud_write(pud)		pte_write(pud_pte(pud))
#define pgd_set(pgdp, pudp)	({pgd_val(*(pgdp)) = (unsigned long)(pudp);})
#define pgd_write(pgd)		pte_write(pgd_pte(pgd))

/*
 * Find an entry in a page-table-directory.  We combine the address region
 * (the high order N bits) and the pgd portion of the address.
 */
#define pgd_index(address) (((address) >> (PGDIR_SHIFT)) & (PTRS_PER_PGD - 1))

#define pgd_offset(mm, address)	 ((mm)->pgd + pgd_index(address))

#define pmd_offset(pudp,addr) \
  (((pmd_t *) pud_page_vaddr(*(pudp))) + (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1)))

#define pte_offset_kernel(dir,addr) \
  (((pte_t *) pmd_page_vaddr(*(dir))) + (((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)))

#define pte_offset_map(dir,addr)	pte_offset_kernel((dir), (addr))
#define pte_unmap(pte)			do { } while(0)

/* to find an entry in a kernel page-table-directory */
/* This now only contains the vmalloc pages */
#define pgd_offset_k(address) pgd_offset(&init_mm, address)
extern void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
			    pte_t *ptep, unsigned long pte, int huge);

/* Atomic PTE updates */
static inline unsigned long pte_update(struct mm_struct *mm,
				       unsigned long addr,
				       pte_t *ptep, unsigned long clr,
				       unsigned long set,
				       int huge)
{
#ifdef PTE_ATOMIC_UPDATES
	unsigned long old, tmp;

	__asm__ __volatile__(
	"1:	ldarx	%0,0,%3		# pte_update\n\
	andi.	%1,%0,%6\n\
	bne-	1b \n\
	andc	%1,%0,%4 \n\
	or	%1,%1,%7\n\
	stdcx.	%1,0,%3 \n\
	bne-	1b"
	: "=&r" (old), "=&r" (tmp), "=m" (*ptep)
	: "r" (ptep), "r" (clr), "m" (*ptep), "i" (_PAGE_BUSY), "r" (set)
	: "cc" );
#else
	unsigned long old = pte_val(*ptep);
	*ptep = __pte((old & ~clr) | set);
#endif
	/* huge pages use the old page table lock */
	if (!huge)
		assert_pte_locked(mm, addr);

#ifdef CONFIG_PPC_STD_MMU_64
	if (old & _PAGE_HASHPTE)
		hpte_need_flush(mm, addr, ptep, old, huge);
#endif

	return old;
}

static inline int __ptep_test_and_clear_young(struct mm_struct *mm,
					      unsigned long addr, pte_t *ptep)
{
	unsigned long old;

	if ((pte_val(*ptep) & (_PAGE_ACCESSED | _PAGE_HASHPTE)) == 0)
		return 0;
	old = pte_update(mm, addr, ptep, _PAGE_ACCESSED, 0, 0);
	return (old & _PAGE_ACCESSED) != 0;
}
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
#define ptep_test_and_clear_young(__vma, __addr, __ptep)		   \
({									   \
	int __r;							   \
	__r = __ptep_test_and_clear_young((__vma)->vm_mm, __addr, __ptep); \
	__r;								   \
})

#define __HAVE_ARCH_PTEP_SET_WRPROTECT
static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
				      pte_t *ptep)
{

	if ((pte_val(*ptep) & _PAGE_RW) == 0)
		return;

	pte_update(mm, addr, ptep, _PAGE_RW, 0, 0);
}

static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
					   unsigned long addr, pte_t *ptep)
{
	if ((pte_val(*ptep) & _PAGE_RW) == 0)
		return;

	pte_update(mm, addr, ptep, _PAGE_RW, 0, 1);
}

/*
 * We currently remove entries from the hashtable regardless of whether
 * the entry was young or dirty. The generic routines only flush if the
 * entry was young or dirty which is not good enough.
 *
 * We should be more intelligent about this but for the moment we override
 * these functions and force a tlb flush unconditionally
 */
#define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
#define ptep_clear_flush_young(__vma, __address, __ptep)		\
({									\
	int __young = __ptep_test_and_clear_young((__vma)->vm_mm, __address, \
						  __ptep);		\
	__young;							\
})

#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
				       unsigned long addr, pte_t *ptep)
{
	unsigned long old = pte_update(mm, addr, ptep, ~0UL, 0, 0);
	return __pte(old);
}

static inline void pte_clear(struct mm_struct *mm, unsigned long addr,
			     pte_t * ptep)
{
	pte_update(mm, addr, ptep, ~0UL, 0, 0);
}


/* Set the dirty and/or accessed bits atomically in a linux PTE, this
 * function doesn't need to flush the hash entry
 */
static inline void __ptep_set_access_flags(pte_t *ptep, pte_t entry)
{
	unsigned long bits = pte_val(entry) &
		(_PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_RW | _PAGE_EXEC);

#ifdef PTE_ATOMIC_UPDATES
	unsigned long old, tmp;

	__asm__ __volatile__(
	"1:	ldarx	%0,0,%4\n\
		andi.	%1,%0,%6\n\
		bne-	1b \n\
		or	%0,%3,%0\n\
		stdcx.	%0,0,%4\n\
		bne-	1b"
	:"=&r" (old), "=&r" (tmp), "=m" (*ptep)
	:"r" (bits), "r" (ptep), "m" (*ptep), "i" (_PAGE_BUSY)
	:"cc");
#else
	unsigned long old = pte_val(*ptep);
	*ptep = __pte(old | bits);
#endif
}

#define __HAVE_ARCH_PTE_SAME
#define pte_same(A,B)	(((pte_val(A) ^ pte_val(B)) & ~_PAGE_HPTEFLAGS) == 0)

#define pte_ERROR(e) \
	pr_err("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e))
#define pmd_ERROR(e) \
	pr_err("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pmd_val(e))
#define pgd_ERROR(e) \
	pr_err("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))

/* Encode and de-code a swap entry */
#define MAX_SWAPFILES_CHECK() do { \
	BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > SWP_TYPE_BITS); \
	/*							\
	 * Don't have overlapping bits with _PAGE_HPTEFLAGS	\
	 * We filter HPTEFLAGS on set_pte.			\
	 */							\
	BUILD_BUG_ON(_PAGE_HPTEFLAGS & (0x1f << _PAGE_BIT_SWAP_TYPE)); \
	} while (0)
/*
 * on pte we don't need handle RADIX_TREE_EXCEPTIONAL_SHIFT;
 */
#define SWP_TYPE_BITS 5
#define __swp_type(x)		(((x).val >> _PAGE_BIT_SWAP_TYPE) \
				& ((1UL << SWP_TYPE_BITS) - 1))
#define __swp_offset(x)		((x).val >> PTE_RPN_SHIFT)
#define __swp_entry(type, offset)	((swp_entry_t) { \
					((type) << _PAGE_BIT_SWAP_TYPE) \
					| ((offset) << PTE_RPN_SHIFT) })

#define __pte_to_swp_entry(pte)		((swp_entry_t) { pte_val((pte)) })
#define __swp_entry_to_pte(x)		__pte((x).val)

void pgtable_cache_add(unsigned shift, void (*ctor)(void *));
void pgtable_cache_init(void);
#endif /* __ASSEMBLY__ */

/*
 * THP pages can't be special. So use the _PAGE_SPECIAL
 */
#define _PAGE_SPLITTING _PAGE_SPECIAL

/*
 * We need to differentiate between explicit huge page and THP huge
 * page, since THP huge page also need to track real subpage details
 */
#define _PAGE_THP_HUGE  _PAGE_4K_PFN

/*
 * set of bits not changed in pmd_modify.
 */
#define _HPAGE_CHG_MASK (PTE_RPN_MASK | _PAGE_HPTEFLAGS |		\
			 _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_SPLITTING | \
			 _PAGE_THP_HUGE)

#ifndef __ASSEMBLY__
/*
 * The linux hugepage PMD now include the pmd entries followed by the address
 * to the stashed pgtable_t. The stashed pgtable_t contains the hpte bits.
 * [ 1 bit secondary | 3 bit hidx | 1 bit valid | 000]. We use one byte per
 * each HPTE entry. With 16MB hugepage and 64K HPTE we need 256 entries and
 * with 4K HPTE we need 4096 entries. Both will fit in a 4K pgtable_t.
 *
 * The last three bits are intentionally left to zero. This memory location
 * are also used as normal page PTE pointers. So if we have any pointers
 * left around while we collapse a hugepage, we need to make sure
 * _PAGE_PRESENT bit of that is zero when we look at them
 */
static inline unsigned int hpte_valid(unsigned char *hpte_slot_array, int index)
{
	return (hpte_slot_array[index] >> 3) & 0x1;
}

static inline unsigned int hpte_hash_index(unsigned char *hpte_slot_array,
					   int index)
{
	return hpte_slot_array[index] >> 4;
}

static inline void mark_hpte_slot_valid(unsigned char *hpte_slot_array,
					unsigned int index, unsigned int hidx)
{
	hpte_slot_array[index] = hidx << 4 | 0x1 << 3;
}

struct page *realmode_pfn_to_page(unsigned long pfn);

static inline char *get_hpte_slot_array(pmd_t *pmdp)
{
	/*
	 * The hpte hindex is stored in the pgtable whose address is in the
	 * second half of the PMD
	 *
	 * Order this load with the test for pmd_trans_huge in the caller
	 */
	smp_rmb();
	return *(char **)(pmdp + PTRS_PER_PMD);


}

extern void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
				   pmd_t *pmdp, unsigned long old_pmd);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot);
extern pmd_t mk_pmd(struct page *page, pgprot_t pgprot);
extern pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot);
extern void set_pmd_at(struct mm_struct *mm, unsigned long addr,
		       pmd_t *pmdp, pmd_t pmd);
extern void update_mmu_cache_pmd(struct vm_area_struct *vma, unsigned long addr,
				 pmd_t *pmd);
/*
 *
 * For core kernel code by design pmd_trans_huge is never run on any hugetlbfs
 * page. The hugetlbfs page table walking and mangling paths are totally
 * separated form the core VM paths and they're differentiated by
 *  VM_HUGETLB being set on vm_flags well before any pmd_trans_huge could run.
 *
 * pmd_trans_huge() is defined as false at build time if
 * CONFIG_TRANSPARENT_HUGEPAGE=n to optimize away code blocks at build
 * time in such case.
 *
 * For ppc64 we need to differntiate from explicit hugepages from THP, because
 * for THP we also track the subpage details at the pmd level. We don't do
 * that for explicit huge pages.
 *
 */
static inline int pmd_trans_huge(pmd_t pmd)
{
	/*
	 * leaf pte for huge page, bottom two bits != 00
	 */
	return (pmd_val(pmd) & 0x3) && (pmd_val(pmd) & _PAGE_THP_HUGE);
}

static inline int pmd_trans_splitting(pmd_t pmd)
{
	if (pmd_trans_huge(pmd))
		return pmd_val(pmd) & _PAGE_SPLITTING;
	return 0;
}

extern int has_transparent_hugepage(void);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

static inline int pmd_large(pmd_t pmd)
{
	/*
	 * leaf pte for huge page, bottom two bits != 00
	 */
	return ((pmd_val(pmd) & 0x3) != 0x0);
}

static inline pte_t pmd_pte(pmd_t pmd)
{
	return __pte(pmd_val(pmd));
}

static inline pmd_t pte_pmd(pte_t pte)
{
	return __pmd(pte_val(pte));
}

static inline pte_t *pmdp_ptep(pmd_t *pmd)
{
	return (pte_t *)pmd;
}

#define pmd_pfn(pmd)		pte_pfn(pmd_pte(pmd))
#define pmd_dirty(pmd)		pte_dirty(pmd_pte(pmd))
#define pmd_young(pmd)		pte_young(pmd_pte(pmd))
#define pmd_mkold(pmd)		pte_pmd(pte_mkold(pmd_pte(pmd)))
#define pmd_wrprotect(pmd)	pte_pmd(pte_wrprotect(pmd_pte(pmd)))
#define pmd_mkdirty(pmd)	pte_pmd(pte_mkdirty(pmd_pte(pmd)))
#define pmd_mkyoung(pmd)	pte_pmd(pte_mkyoung(pmd_pte(pmd)))
#define pmd_mkwrite(pmd)	pte_pmd(pte_mkwrite(pmd_pte(pmd)))

#define __HAVE_ARCH_PMD_WRITE
#define pmd_write(pmd)		pte_write(pmd_pte(pmd))

static inline pmd_t pmd_mkhuge(pmd_t pmd)
{
	/* Do nothing, mk_pmd() does this part.  */
	return pmd;
}

static inline pmd_t pmd_mknotpresent(pmd_t pmd)
{
	pmd_val(pmd) &= ~_PAGE_PRESENT;
	return pmd;
}

static inline pmd_t pmd_mksplitting(pmd_t pmd)
{
	pmd_val(pmd) |= _PAGE_SPLITTING;
	return pmd;
}

#define __HAVE_ARCH_PMD_SAME
static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
{
	return (((pmd_val(pmd_a) ^ pmd_val(pmd_b)) & ~_PAGE_HPTEFLAGS) == 0);
}

#define __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
extern int pmdp_set_access_flags(struct vm_area_struct *vma,
				 unsigned long address, pmd_t *pmdp,
				 pmd_t entry, int dirty);

extern unsigned long pmd_hugepage_update(struct mm_struct *mm,
					 unsigned long addr,
					 pmd_t *pmdp,
					 unsigned long clr,
					 unsigned long set);

static inline int __pmdp_test_and_clear_young(struct mm_struct *mm,
					      unsigned long addr, pmd_t *pmdp)
{
	unsigned long old;

	if ((pmd_val(*pmdp) & (_PAGE_ACCESSED | _PAGE_HASHPTE)) == 0)
		return 0;
	old = pmd_hugepage_update(mm, addr, pmdp, _PAGE_ACCESSED, 0);
	return ((old & _PAGE_ACCESSED) != 0);
}

#define __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
extern int pmdp_test_and_clear_young(struct vm_area_struct *vma,
				     unsigned long address, pmd_t *pmdp);
#define __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
				  unsigned long address, pmd_t *pmdp);

#define __HAVE_ARCH_PMDP_GET_AND_CLEAR
extern pmd_t pmdp_get_and_clear(struct mm_struct *mm,
				unsigned long addr, pmd_t *pmdp);

#define __HAVE_ARCH_PMDP_CLEAR_FLUSH
extern pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
			      pmd_t *pmdp);

#define __HAVE_ARCH_PMDP_SET_WRPROTECT
static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
				      pmd_t *pmdp)
{

	if ((pmd_val(*pmdp) & _PAGE_RW) == 0)
		return;

	pmd_hugepage_update(mm, addr, pmdp, _PAGE_RW, 0);
}

#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
extern void pmdp_splitting_flush(struct vm_area_struct *vma,
				 unsigned long address, pmd_t *pmdp);

#define __HAVE_ARCH_PGTABLE_DEPOSIT
extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
				       pgtable_t pgtable);
#define __HAVE_ARCH_PGTABLE_WITHDRAW
extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);

#define __HAVE_ARCH_PMDP_INVALIDATE
extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
			    pmd_t *pmdp);

#define pmd_move_must_withdraw pmd_move_must_withdraw
struct spinlock;
static inline int pmd_move_must_withdraw(struct spinlock *new_pmd_ptl,
					 struct spinlock *old_pmd_ptl)
{
	/*
	 * Archs like ppc64 use pgtable to store per pmd
	 * specific information. So when we switch the pmd,
	 * we should also withdraw and deposit the pgtable
	 */
	return true;
}
#endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_PGTABLE_PPC64_H_ */