include/asm-generic/tlb.h

   1 /* asm-generic/tlb.h
   2  *
   3  *      Generic TLB shootdown code
   4  *
   5  * Copyright 2001 Red Hat, Inc.
   6  * Based on code from mm/memory.c Copyright Linus Torvalds and others.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License
  10  * as published by the Free Software Foundation; either version
  11  * 2 of the License, or (at your option) any later version.
  12  */
  13 #ifndef _ASM_GENERIC__TLB_H
  14 #define _ASM_GENERIC__TLB_H
  15
  16 #include <linux/config.h>
  17 #include <linux/swap.h>
  18 #include <asm/pgalloc.h>
  19 #include <asm/tlbflush.h>
  20
  21 /*
  22  * For UP we don't need to worry about TLB flush
  23  * and page free order so much..
  24  */
  25 #ifdef CONFIG_SMP
  26   #define FREE_PTE_NR   506
  27   #define tlb_fast_mode(tlb) ((tlb)->nr == ~0U)
  28 #else
  29   #define FREE_PTE_NR   1
  30   #define tlb_fast_mode(tlb) 1
  31 #endif
  32
  33 /* struct mmu_gather is an opaque type used by the mm code for passing around
  34  * any data needed by arch specific code for tlb_remove_page.  This structure
  35  * can be per-CPU or per-MM as the page table lock is held for the duration of
  36  * TLB shootdown.
  37  */
  38 struct mmu_gather {
  39         struct mm_struct        *mm;
  40         unsigned int            nr;     /* set to ~0U means fast mode */
  41         unsigned int            need_flush;/* Really unmapped some ptes? */
  42         unsigned int            fullmm; /* non-zero means full mm flush */
  43         unsigned long           freed;
  44         struct page *           pages[FREE_PTE_NR];
  45 };
  46
  47 /* Users of the generic TLB shootdown code must declare this storage space. */
  48 DECLARE_PER_CPU(struct mmu_gather, mmu_gathers);
  49
  50 /* tlb_gather_mmu
  51  *      Return a pointer to an initialized struct mmu_gather.
  52  */
  53 static inline struct mmu_gather *
  54 tlb_gather_mmu(struct mm_struct *mm, unsigned int full_mm_flush)
  55 {
  56         struct mmu_gather *tlb = &per_cpu(mmu_gathers, smp_processor_id());
  57
  58         tlb->mm = mm;
  59
  60         /* Use fast mode if only one CPU is online */
  61         tlb->nr = num_online_cpus() > 1 ? 0U : ~0U;
  62
  63         tlb->fullmm = full_mm_flush;
  64         tlb->freed = 0;
  65
  66         return tlb;
  67 }
  68
  69 static inline void
  70 tlb_flush_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
  71 {
  72         if (!tlb->need_flush)
  73                 return;
  74         tlb->need_flush = 0;
  75         tlb_flush(tlb);
  76         if (!tlb_fast_mode(tlb)) {
  77                 free_pages_and_swap_cache(tlb->pages, tlb->nr);
  78                 tlb->nr = 0;
  79         }
  80 }
  81
  82 /* tlb_finish_mmu
  83  *      Called at the end of the shootdown operation to free up any resources
  84  *      that were required.  The page table lock is still held at this point.
  85  */
  86 static inline void
  87 tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
  88 {
  89         int freed = tlb->freed;
  90         struct mm_struct *mm = tlb->mm;
  91         int rss = mm->rss;
  92
  93         if (rss < freed)
  94                 freed = rss;
  95         mm->rss = rss - freed;
  96         tlb_flush_mmu(tlb, start, end);
  97
  98         /* keep the page table cache within bounds */
  99         check_pgt_cache();
 100 }
 101
 102 static inline unsigned int
 103 tlb_is_full_mm(struct mmu_gather *tlb)
 104 {
 105         return tlb->fullmm;
 106 }
 107
 108 /* tlb_remove_page
 109  *      Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
 110  *      handling the additional races in SMP caused by other CPUs caching valid
 111  *      mappings in their TLBs.
 112  */
 113 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 114 {
 115         tlb->need_flush = 1;
 116         if (tlb_fast_mode(tlb)) {
 117                 free_page_and_swap_cache(page);
 118                 return;
 119         }
 120         tlb->pages[tlb->nr++] = page;
 121         if (tlb->nr >= FREE_PTE_NR)
 122                 tlb_flush_mmu(tlb, 0, 0);
 123 }
 124
 125 /**
 126  * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
 127  *
 128  * Record the fact that pte's were really umapped in ->need_flush, so we can
 129  * later optimise away the tlb invalidate.   This helps when userspace is
 130  * unmapping already-unmapped pages, which happens quite a lot.
 131  */
 132 #define tlb_remove_tlb_entry(tlb, ptep, address)                \
 133         do {                                                    \
 134                 tlb->need_flush = 1;                            \
 135                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
 136         } while (0)
 137
 138 #define pte_free_tlb(tlb, ptep)                                 \
 139         do {                                                    \
 140                 tlb->need_flush = 1;                            \
 141                 __pte_free_tlb(tlb, ptep);                      \
 142         } while (0)
 143
 144 #define pmd_free_tlb(tlb, pmdp)                                 \
 145         do {                                                    \
 146                 tlb->need_flush = 1;                            \
 147                 __pmd_free_tlb(tlb, pmdp);                      \
 148         } while (0)
 149
 150 #define tlb_migrate_finish(mm) do {} while (0)
 151
 152 #endif /* _ASM_GENERIC__TLB_H */