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Commit 86fa949b authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

x86/mm: provide pmdp_establish() helper 

We need an atomic way to setup pmd page table entry, avoiding races with
CPU setting dirty/accessed bits.  This is required to implement
pmdp_invalidate() that doesn't lose these bits.

On PAE we can avoid expensive cmpxchg8b for cases when new page table
entry is not present.  If it's present, fallback to cpmxchg loop.

[akpm@linux-foundation.org: add missing `do' to do-while loop]
Link: http://lkml.kernel.org/r/20171213105756.69879-10-kirill.shutemov@linux.intel.com


Signed-off-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a8e654f0

arch/x86/include/asm/pgtable-3level.h

+36 −1
Original line number Diff line number Diff line
@@ -158,7 +158,6 @@ static inline pte_t native_ptep_get_and_clear(pte_t *ptep) 
#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)

#endif



#ifdef CONFIG_SMP

union split_pmd {

	struct {

		u32 pmd_low;
@@ -166,6 +165,8 @@ union split_pmd { 
	};

	pmd_t pmd;

};



#ifdef CONFIG_SMP

static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)

{

	union split_pmd res, *orig = (union split_pmd *)pmdp;
@@ -181,6 +182,40 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp) 
#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)

#endif



#ifndef pmdp_establish

#define pmdp_establish pmdp_establish

static inline pmd_t pmdp_establish(struct vm_area_struct *vma,

		unsigned long address, pmd_t *pmdp, pmd_t pmd)

{

	pmd_t old;



	/*

	 * If pmd has present bit cleared we can get away without expensive

	 * cmpxchg64: we can update pmdp half-by-half without racing with

	 * anybody.

	 */

	if (!(pmd_val(pmd) & _PAGE_PRESENT)) {

		union split_pmd old, new, *ptr;



		ptr = (union split_pmd *)pmdp;



		new.pmd = pmd;



		/* xchg acts as a barrier before setting of the high bits */

		old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);

		old.pmd_high = ptr->pmd_high;

		ptr->pmd_high = new.pmd_high;

		return old.pmd;

	}



	do {

		old = *pmdp;

	} while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);



	return old;

}

#endif



#ifdef CONFIG_SMP

union split_pud {

	struct {

arch/x86/include/asm/pgtable.h

+15 −0
Original line number Diff line number Diff line
@@ -1109,6 +1109,21 @@ static inline int pud_write(pud_t pud) 
	return pud_flags(pud) & _PAGE_RW;

}



#ifndef pmdp_establish

#define pmdp_establish pmdp_establish

static inline pmd_t pmdp_establish(struct vm_area_struct *vma,

		unsigned long address, pmd_t *pmdp, pmd_t pmd)

{

	if (IS_ENABLED(CONFIG_SMP)) {

		return xchg(pmdp, pmd);

	} else {

		pmd_t old = *pmdp;

		*pmdp = pmd;

		return old;

	}

}

#endif



/*

 * clone_pgd_range(pgd_t *dst, pgd_t *src, int count);

 *