arch/arm/include/asm/tlb.h

   1 /*
   2  *  arch/arm/include/asm/tlb.h
   3  *
   4  *  Copyright (C) 2002 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *  Experimentation shows that on a StrongARM, it appears to be faster
  11  *  to use the "invalidate whole tlb" rather than "invalidate single
  12  *  tlb" for this.
  13  *
  14  *  This appears true for both the process fork+exit case, as well as
  15  *  the munmap-large-area case.
  16  */
  17 #ifndef __ASMARM_TLB_H
  18 #define __ASMARM_TLB_H
  19
  20 #include <asm/cacheflush.h>
  21
  22 #ifndef CONFIG_MMU
  23
  24 #include <linux/pagemap.h>
  25
  26 #define tlb_flush(tlb)  ((void) tlb)
  27
  28 #include <asm-generic/tlb.h>
  29
  30 #else /* !CONFIG_MMU */
  31
  32 #include <linux/swap.h>
  33 #include <asm/pgalloc.h>
  34 #include <asm/tlbflush.h>
  35
  36 /*
  37  * We need to delay page freeing for SMP as other CPUs can access pages
  38  * which have been removed but not yet had their TLB entries invalidated.
  39  * Also, as ARMv7 speculative prefetch can drag new entries into the TLB,
  40  * we need to apply this same delaying tactic to ensure correct operation.
  41  */
  42 #if defined(CONFIG_SMP) || defined(CONFIG_CPU_32v7)
  43 #define tlb_fast_mode(tlb)      0
  44 #define FREE_PTE_NR             500
  45 #else
  46 #define tlb_fast_mode(tlb)      1
  47 #define FREE_PTE_NR             0
  48 #endif
  49
  50 /*
  51  * TLB handling.  This allows us to remove pages from the page
  52  * tables, and efficiently handle the TLB issues.
  53  */
  54 struct mmu_gather {
  55         struct mm_struct        *mm;
  56         unsigned int            fullmm;
  57         struct vm_area_struct   *vma;
  58         unsigned long           range_start;
  59         unsigned long           range_end;
  60         unsigned int            nr;
  61         struct page             *pages[FREE_PTE_NR];
  62 };
  63
  64 DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
  65
  66 /*
  67  * This is unnecessarily complex.  There's three ways the TLB shootdown
  68  * code is used:
  69  *  1. Unmapping a range of vmas.  See zap_page_range(), unmap_region().
  70  *     tlb->fullmm = 0, and tlb_start_vma/tlb_end_vma will be called.
  71  *     tlb->vma will be non-NULL.
  72  *  2. Unmapping all vmas.  See exit_mmap().
  73  *     tlb->fullmm = 1, and tlb_start_vma/tlb_end_vma will be called.
  74  *     tlb->vma will be non-NULL.  Additionally, page tables will be freed.
  75  *  3. Unmapping argument pages.  See shift_arg_pages().
  76  *     tlb->fullmm = 0, but tlb_start_vma/tlb_end_vma will not be called.
  77  *     tlb->vma will be NULL.
  78  */
  79 static inline void tlb_flush(struct mmu_gather *tlb)
  80 {
  81         if (tlb->fullmm || !tlb->vma)
  82                 flush_tlb_mm(tlb->mm);
  83         else if (tlb->range_end > 0) {
  84                 flush_tlb_range(tlb->vma, tlb->range_start, tlb->range_end);
  85                 tlb->range_start = TASK_SIZE;
  86                 tlb->range_end = 0;
  87         }
  88 }
  89
  90 static inline void tlb_add_flush(struct mmu_gather *tlb, unsigned long addr)
  91 {
  92         if (!tlb->fullmm) {
  93                 if (addr < tlb->range_start)
  94                         tlb->range_start = addr;
  95                 if (addr + PAGE_SIZE > tlb->range_end)
  96                         tlb->range_end = addr + PAGE_SIZE;
  97         }
  98 }
  99
 100 static inline void tlb_flush_mmu(struct mmu_gather *tlb)
 101 {
 102         tlb_flush(tlb);
 103         if (!tlb_fast_mode(tlb)) {
 104                 free_pages_and_swap_cache(tlb->pages, tlb->nr);
 105                 tlb->nr = 0;
 106         }
 107 }
 108
 109 static inline struct mmu_gather *
 110 tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
 111 {
 112         struct mmu_gather *tlb = &get_cpu_var(mmu_gathers);
 113
 114         tlb->mm = mm;
 115         tlb->fullmm = full_mm_flush;
 116         tlb->vma = NULL;
 117         tlb->nr = 0;
 118
 119         return tlb;
 120 }
 121
 122 static inline void
 123 tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
 124 {
 125         tlb_flush_mmu(tlb);
 126
 127         /* keep the page table cache within bounds */
 128         check_pgt_cache();
 129
 130         put_cpu_var(mmu_gathers);
 131 }
 132
 133 /*
 134  * Memorize the range for the TLB flush.
 135  */
 136 static inline void
 137 tlb_remove_tlb_entry(struct mmu_gather *tlb, pte_t *ptep, unsigned long addr)
 138 {
 139         tlb_add_flush(tlb, addr);
 140 }
 141
 142 /*
 143  * In the case of tlb vma handling, we can optimise these away in the
 144  * case where we're doing a full MM flush.  When we're doing a munmap,
 145  * the vmas are adjusted to only cover the region to be torn down.
 146  */
 147 static inline void
 148 tlb_start_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
 149 {
 150         if (!tlb->fullmm) {
 151                 flush_cache_range(vma, vma->vm_start, vma->vm_end);
 152                 tlb->vma = vma;
 153                 tlb->range_start = TASK_SIZE;
 154                 tlb->range_end = 0;
 155         }
 156 }
 157
 158 static inline void
 159 tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
 160 {
 161         if (!tlb->fullmm)
 162                 tlb_flush(tlb);
 163 }
 164
 165 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 166 {
 167         if (tlb_fast_mode(tlb)) {
 168                 free_page_and_swap_cache(page);
 169         } else {
 170                 tlb->pages[tlb->nr++] = page;
 171                 if (tlb->nr >= FREE_PTE_NR)
 172                         tlb_flush_mmu(tlb);
 173         }
 174 }
 175
 176 static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t pte,
 177         unsigned long addr)
 178 {
 179         pgtable_page_dtor(pte);
 180         tlb_add_flush(tlb, addr);
 181         tlb_remove_page(tlb, pte);
 182 }
 183
 184 #define pte_free_tlb(tlb, ptep, addr)   __pte_free_tlb(tlb, ptep, addr)
 185 #define pmd_free_tlb(tlb, pmdp, addr)   pmd_free((tlb)->mm, pmdp)
 186
 187 #define tlb_migrate_finish(mm)          do { } while (0)
 188
 189 #endif /* CONFIG_MMU */
 190 #endif