![Rik van Riel](/assets/img/avatar_default.png)
The function ptep_set_access_flags is only ever used to upgrade access permissions to a page. That means the only negative side effect of not flushing remote TLBs is that other CPUs may incur spurious page faults, if they happen to access the same address, and still have a PTE with the old permissions cached in their TLB. Having another CPU maybe incur a spurious page fault is faster than always incurring the cost of a remote TLB flush, so replace the remote TLB flush with a purely local one. This should be safe on every architecture that correctly implements flush_tlb_fix_spurious_fault() to actually invalidate the local TLB entry that caused a page fault, as well as on architectures where the hardware invalidates TLB entries that cause page faults. In the unlikely event that you are hitting what appears to be an infinite loop of page faults, and 'git bisect' took you to this changeset, your architecture needs to implement flush_tlb_fix_spurious_fault to actually flush the TLB entry. Signed-off-by: Rik van Riel <riel@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Michel Lespinasse <walken@google.com> Cc: Ingo Molnar <mingo@kernel.org>
173 lines
4.6 KiB
C
173 lines
4.6 KiB
C
/*
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* mm/pgtable-generic.c
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*
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* Generic pgtable methods declared in asm-generic/pgtable.h
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*
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* Copyright (C) 2010 Linus Torvalds
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*/
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#include <linux/pagemap.h>
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#include <asm/tlb.h>
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#include <asm-generic/pgtable.h>
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#ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
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/*
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* Only sets the access flags (dirty, accessed), as well as write
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* permission. Furthermore, we know it always gets set to a "more
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* permissive" setting, which allows most architectures to optimize
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* this. We return whether the PTE actually changed, which in turn
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* instructs the caller to do things like update__mmu_cache. This
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* used to be done in the caller, but sparc needs minor faults to
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* force that call on sun4c so we changed this macro slightly
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*/
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int ptep_set_access_flags(struct vm_area_struct *vma,
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unsigned long address, pte_t *ptep,
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pte_t entry, int dirty)
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{
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int changed = !pte_same(*ptep, entry);
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if (changed) {
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set_pte_at(vma->vm_mm, address, ptep, entry);
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flush_tlb_fix_spurious_fault(vma, address);
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}
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return changed;
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}
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#endif
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#ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
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int pmdp_set_access_flags(struct vm_area_struct *vma,
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unsigned long address, pmd_t *pmdp,
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pmd_t entry, int dirty)
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{
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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int changed = !pmd_same(*pmdp, entry);
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VM_BUG_ON(address & ~HPAGE_PMD_MASK);
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if (changed) {
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set_pmd_at(vma->vm_mm, address, pmdp, entry);
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flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
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}
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return changed;
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#else /* CONFIG_TRANSPARENT_HUGEPAGE */
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BUG();
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return 0;
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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}
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#endif
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#ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
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int ptep_clear_flush_young(struct vm_area_struct *vma,
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unsigned long address, pte_t *ptep)
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{
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int young;
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young = ptep_test_and_clear_young(vma, address, ptep);
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if (young)
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flush_tlb_page(vma, address);
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return young;
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}
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#endif
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#ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
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int pmdp_clear_flush_young(struct vm_area_struct *vma,
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unsigned long address, pmd_t *pmdp)
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{
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int young;
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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VM_BUG_ON(address & ~HPAGE_PMD_MASK);
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#else
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BUG();
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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young = pmdp_test_and_clear_young(vma, address, pmdp);
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if (young)
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flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
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return young;
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}
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#endif
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#ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH
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pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,
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pte_t *ptep)
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{
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pte_t pte;
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pte = ptep_get_and_clear((vma)->vm_mm, address, ptep);
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flush_tlb_page(vma, address);
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return pte;
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}
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#endif
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#ifndef __HAVE_ARCH_PMDP_CLEAR_FLUSH
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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pmd_t pmdp_clear_flush(struct vm_area_struct *vma, unsigned long address,
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pmd_t *pmdp)
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{
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pmd_t pmd;
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VM_BUG_ON(address & ~HPAGE_PMD_MASK);
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pmd = pmdp_get_and_clear(vma->vm_mm, address, pmdp);
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flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
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return pmd;
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}
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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#endif
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#ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
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pmd_t *pmdp)
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{
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pmd_t pmd = pmd_mksplitting(*pmdp);
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VM_BUG_ON(address & ~HPAGE_PMD_MASK);
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set_pmd_at(vma->vm_mm, address, pmdp, pmd);
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/* tlb flush only to serialize against gup-fast */
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flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
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}
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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#endif
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#ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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void pgtable_trans_huge_deposit(struct mm_struct *mm, pgtable_t pgtable)
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{
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assert_spin_locked(&mm->page_table_lock);
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/* FIFO */
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if (!mm->pmd_huge_pte)
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INIT_LIST_HEAD(&pgtable->lru);
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else
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list_add(&pgtable->lru, &mm->pmd_huge_pte->lru);
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mm->pmd_huge_pte = pgtable;
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}
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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#endif
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#ifndef __HAVE_ARCH_PGTABLE_WITHDRAW
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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/* no "address" argument so destroys page coloring of some arch */
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pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm)
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{
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pgtable_t pgtable;
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assert_spin_locked(&mm->page_table_lock);
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/* FIFO */
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pgtable = mm->pmd_huge_pte;
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if (list_empty(&pgtable->lru))
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mm->pmd_huge_pte = NULL;
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else {
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mm->pmd_huge_pte = list_entry(pgtable->lru.next,
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struct page, lru);
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list_del(&pgtable->lru);
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}
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return pgtable;
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}
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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#endif
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#ifndef __HAVE_ARCH_PMDP_INVALIDATE
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
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pmd_t *pmdp)
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{
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set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(*pmdp));
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flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
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}
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#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
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#endif
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