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Commit d6d861e3 authored by Zachary Amsden's avatar Zachary Amsden Committed by Linus Torvalds
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[PATCH] paravirt: optimize ptep establish for pae 



The ptep_establish macro is only used on user-level PTEs, for P->P mapping
changes.  Since these always happen under protection of the pagetable lock,
the strong synchronization of a 64-bit cmpxchg is not needed, in fact, not
even a lock prefix needs to be used.  We can simply instead clear the P-bit,
followed by a normal set.  The write ordering is still important to avoid the
possibility of the TLB snooping a partially written PTE and getting a bad
mapping installed.

Signed-off-by: default avatarZachary Amsden <zach@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 23002d88

include/asm-i386/pgtable-2level.h

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#define set_pte(pteptr, pteval) (*(pteptr) = pteval)

#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)

#define set_pte_atomic(pteptr, pteval) set_pte(pteptr,pteval)

#define set_pte_present(mm,addr,ptep,pteval) set_pte_at(mm,addr,ptep,pteval)

#define set_pmd(pmdptr, pmdval) (*(pmdptr) = (pmdval))



#define pte_clear(mm,addr,xp)	do { set_pte_at(mm, addr, xp, __pte(0)); } while (0)

include/asm-i386/pgtable-3level.h

+15 −0
Original line number Diff line number Diff line
@@ -58,6 +58,21 @@ static inline void set_pte(pte_t *ptep, pte_t pte) 
}

#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)



/*

 * Since this is only called on user PTEs, and the page fault handler

 * must handle the already racy situation of simultaneous page faults,

 * we are justified in merely clearing the PTE present bit, followed

 * by a set.  The ordering here is important.

 */

static inline void set_pte_present(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte)

{

	ptep->pte_low = 0;

	smp_wmb();

	ptep->pte_high = pte.pte_high;

	smp_wmb();

	ptep->pte_low = pte.pte_low;

}



#define __HAVE_ARCH_SET_PTE_ATOMIC

#define set_pte_atomic(pteptr,pteval) \

		set_64bit((unsigned long long *)(pteptr),pte_val(pteval))

include/asm-i386/pgtable.h

+11 −0
Original line number Diff line number Diff line
@@ -269,6 +269,17 @@ do { \ 
#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_DIRTY

#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG



/*

 * Rules for using ptep_establish: the pte MUST be a user pte, and

 * must be a present->present transition.

 */

#define __HAVE_ARCH_PTEP_ESTABLISH

#define ptep_establish(vma, address, ptep, pteval)			\

do {									\

	set_pte_present((vma)->vm_mm, address, ptep, pteval);		\

	flush_tlb_page(vma, address);					\

} while (0)



#define __HAVE_ARCH_PTEP_CLEAR_DIRTY_FLUSH

#define ptep_clear_flush_dirty(vma, address, ptep)			\

({									\