include/asm-generic/tlb.h

   1 /* include/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  * Copyright 2011 Red Hat, Inc., Peter Zijlstra
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License
  12  * as published by the Free Software Foundation; either version
  13  * 2 of the License, or (at your option) any later version.
  14  */
  15 #ifndef _ASM_GENERIC__TLB_H
  16 #define _ASM_GENERIC__TLB_H
  17
  18 #include <linux/swap.h>
  19 #include <asm/pgalloc.h>
  20 #include <asm/tlbflush.h>
  21
  22 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
  23 /*
  24  * Semi RCU freeing of the page directories.
  25  *
  26  * This is needed by some architectures to implement software pagetable walkers.
  27  *
  28  * gup_fast() and other software pagetable walkers do a lockless page-table
  29  * walk and therefore needs some synchronization with the freeing of the page
  30  * directories. The chosen means to accomplish that is by disabling IRQs over
  31  * the walk.
  32  *
  33  * Architectures that use IPIs to flush TLBs will then automagically DTRT,
  34  * since we unlink the page, flush TLBs, free the page. Since the disabling of
  35  * IRQs delays the completion of the TLB flush we can never observe an already
  36  * freed page.
  37  *
  38  * Architectures that do not have this (PPC) need to delay the freeing by some
  39  * other means, this is that means.
  40  *
  41  * What we do is batch the freed directory pages (tables) and RCU free them.
  42  * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
  43  * holds off grace periods.
  44  *
  45  * However, in order to batch these pages we need to allocate storage, this
  46  * allocation is deep inside the MM code and can thus easily fail on memory
  47  * pressure. To guarantee progress we fall back to single table freeing, see
  48  * the implementation of tlb_remove_table_one().
  49  *
  50  */
  51 struct mmu_table_batch {
  52         struct rcu_head         rcu;
  53         unsigned int            nr;
  54         void                    *tables[0];
  55 };
  56
  57 #define MAX_TABLE_BATCH         \
  58         ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
  59
  60 extern void tlb_table_flush(struct mmu_gather *tlb);
  61 extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
  62
  63 #endif
  64
  65 /*
  66  * If we can't allocate a page to make a big batch of page pointers
  67  * to work on, then just handle a few from the on-stack structure.
  68  */
  69 #define MMU_GATHER_BUNDLE       8
  70
  71 struct mmu_gather_batch {
  72         struct mmu_gather_batch *next;
  73         unsigned int            nr;
  74         unsigned int            max;
  75         struct page             *pages[0];
  76 };
  77
  78 #define MAX_GATHER_BATCH        \
  79         ((PAGE_SIZE - sizeof(struct mmu_gather_batch)) / sizeof(void *))
  80
  81 /*
  82  * Limit the maximum number of mmu_gather batches to reduce a risk of soft
  83  * lockups for non-preemptible kernels on huge machines when a lot of memory
  84  * is zapped during unmapping.
  85  * 10K pages freed at once should be safe even without a preemption point.
  86  */
  87 #define MAX_GATHER_BATCH_COUNT  (10000UL/MAX_GATHER_BATCH)
  88
  89 /* struct mmu_gather is an opaque type used by the mm code for passing around
  90  * any data needed by arch specific code for tlb_remove_page.
  91  */
  92 struct mmu_gather {
  93         struct mm_struct        *mm;
  94 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
  95         struct mmu_table_batch  *batch;
  96 #endif
  97         unsigned long           start;
  98         unsigned long           end;
  99         /* we are in the middle of an operation to clear
 100          * a full mm and can make some optimizations */
 101         unsigned int            fullmm : 1,
 102         /* we have performed an operation which
 103          * requires a complete flush of the tlb */
 104                                 need_flush_all : 1;
 105
 106         struct mmu_gather_batch *active;
 107         struct mmu_gather_batch local;
 108         struct page             *__pages[MMU_GATHER_BUNDLE];
 109         unsigned int            batch_count;
 110         /*
 111          * __tlb_adjust_range  will track the new addr here,
 112          * that that we can adjust the range after the flush
 113          */
 114         unsigned long addr;
 115 };
 116
 117 #define HAVE_GENERIC_MMU_GATHER
 118
 119 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end);
 120 void tlb_flush_mmu(struct mmu_gather *tlb);
 121 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,
 122                                                         unsigned long end);
 123 bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page);
 124
 125 static inline void __tlb_adjust_range(struct mmu_gather *tlb,
 126                                       unsigned long address)
 127 {
 128         tlb->start = min(tlb->start, address);
 129         tlb->end = max(tlb->end, address + PAGE_SIZE);
 130         /*
 131          * Track the last address with which we adjusted the range. This
 132          * will be used later to adjust again after a mmu_flush due to
 133          * failed __tlb_remove_page
 134          */
 135         tlb->addr = address;
 136 }
 137
 138 static inline void __tlb_reset_range(struct mmu_gather *tlb)
 139 {
 140         if (tlb->fullmm) {
 141                 tlb->start = tlb->end = ~0;
 142         } else {
 143                 tlb->start = TASK_SIZE;
 144                 tlb->end = 0;
 145         }
 146 }
 147
 148 /* tlb_remove_page
 149  *      Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
 150  *      required.
 151  */
 152 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 153 {
 154         if (__tlb_remove_page(tlb, page)) {
 155                 tlb_flush_mmu(tlb);
 156                 __tlb_adjust_range(tlb, tlb->addr);
 157                 __tlb_remove_page(tlb, page);
 158         }
 159 }
 160
 161 static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb, struct page *page)
 162 {
 163         /* active->nr should be zero when we call this */
 164         VM_BUG_ON_PAGE(tlb->active->nr, page);
 165         __tlb_adjust_range(tlb, tlb->addr);
 166         return __tlb_remove_page(tlb, page);
 167 }
 168
 169 /*
 170  * In the case of tlb vma handling, we can optimise these away in the
 171  * case where we're doing a full MM flush.  When we're doing a munmap,
 172  * the vmas are adjusted to only cover the region to be torn down.
 173  */
 174 #ifndef tlb_start_vma
 175 #define tlb_start_vma(tlb, vma) do { } while (0)
 176 #endif
 177
 178 #define __tlb_end_vma(tlb, vma)                                 \
 179         do {                                                    \
 180                 if (!tlb->fullmm && tlb->end) {                 \
 181                         tlb_flush(tlb);                         \
 182                         __tlb_reset_range(tlb);                 \
 183                 }                                               \
 184         } while (0)
 185
 186 #ifndef tlb_end_vma
 187 #define tlb_end_vma     __tlb_end_vma
 188 #endif
 189
 190 #ifndef __tlb_remove_tlb_entry
 191 #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
 192 #endif
 193
 194 /**
 195  * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
 196  *
 197  * Record the fact that pte's were really unmapped by updating the range,
 198  * so we can later optimise away the tlb invalidate.   This helps when
 199  * userspace is unmapping already-unmapped pages, which happens quite a lot.
 200  */
 201 #define tlb_remove_tlb_entry(tlb, ptep, address)                \
 202         do {                                                    \
 203                 __tlb_adjust_range(tlb, address);               \
 204                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
 205         } while (0)
 206
 207 /**
 208  * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation
 209  * This is a nop so far, because only x86 needs it.
 210  */
 211 #ifndef __tlb_remove_pmd_tlb_entry
 212 #define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0)
 213 #endif
 214
 215 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)            \
 216         do {                                                    \
 217                 __tlb_adjust_range(tlb, address);               \
 218                 __tlb_remove_pmd_tlb_entry(tlb, pmdp, address); \
 219         } while (0)
 220
 221 #define pte_free_tlb(tlb, ptep, address)                        \
 222         do {                                                    \
 223                 __tlb_adjust_range(tlb, address);               \
 224                 __pte_free_tlb(tlb, ptep, address);             \
 225         } while (0)
 226
 227 #ifndef __ARCH_HAS_4LEVEL_HACK
 228 #define pud_free_tlb(tlb, pudp, address)                        \
 229         do {                                                    \
 230                 __tlb_adjust_range(tlb, address);               \
 231                 __pud_free_tlb(tlb, pudp, address);             \
 232         } while (0)
 233 #endif
 234
 235 #define pmd_free_tlb(tlb, pmdp, address)                        \
 236         do {                                                    \
 237                 __tlb_adjust_range(tlb, address);               \
 238                 __pmd_free_tlb(tlb, pmdp, address);             \
 239         } while (0)
 240
 241 #define tlb_migrate_finish(mm) do {} while (0)
 242
 243 #endif /* _ASM_GENERIC__TLB_H */