00mm9 optimize ptep establish for pae.patch
Subsystems (2)
PATCH 6/9 00mm9 optimize ptep establish for pae.patch
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.
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include/asm-i386/pgtable-2level.h +1 -0
@@ -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)
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include/asm-i386/pgtable-3level.h +15 -0
@@ -57,6 +57,21 @@ static inline void set_pte(pte_t *ptep, ptep->pte_low = pte.pte_low; }#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) \
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include/asm-i386/pgtable.h +11 -0
@@ -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) \ ({ \
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