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         int page_size;
 111 };
 112
 113 #define HAVE_GENERIC_MMU_GATHER
 114
 115 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end);
 116 void tlb_flush_mmu(struct mmu_gather *tlb);
 117 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,
 118                                                         unsigned long end);
 119 extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
 120                                    int page_size);
 121
 122 static inline void __tlb_adjust_range(struct mmu_gather *tlb,
 123                                       unsigned long address,
 124                                       unsigned int range_size)
 125 {
 126         tlb->start = min(tlb->start, address);
 127         tlb->end = max(tlb->end, address + range_size);
 128 }
 129
 130 static inline void __tlb_reset_range(struct mmu_gather *tlb)
 131 {
 132         if (tlb->fullmm) {
 133                 tlb->start = tlb->end = ~0;
 134         } else {
 135                 tlb->start = TASK_SIZE;
 136                 tlb->end = 0;
 137         }
 138 }
 139
 140 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 141                                         struct page *page, int page_size)
 142 {
 143         if (__tlb_remove_page_size(tlb, page, page_size))
 144                 tlb_flush_mmu(tlb);
 145 }
 146
 147 static inline bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 148 {
 149         return __tlb_remove_page_size(tlb, page, PAGE_SIZE);
 150 }
 151
 152 /* tlb_remove_page
 153  *      Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
 154  *      required.
 155  */
 156 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 157 {
 158         return tlb_remove_page_size(tlb, page, PAGE_SIZE);
 159 }
 160
 161 #ifndef tlb_remove_check_page_size_change
 162 #define tlb_remove_check_page_size_change tlb_remove_check_page_size_change
 163 static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 164                                                      unsigned int page_size)
 165 {
 166         /*
 167          * We don't care about page size change, just update
 168          * mmu_gather page size here so that debug checks
 169          * doesn't throw false warning.
 170          */
 171 #ifdef CONFIG_DEBUG_VM
 172         tlb->page_size = page_size;
 173 #endif
 174 }
 175 #endif
 176
 177 /*
 178  * In the case of tlb vma handling, we can optimise these away in the
 179  * case where we're doing a full MM flush.  When we're doing a munmap,
 180  * the vmas are adjusted to only cover the region to be torn down.
 181  */
 182 #ifndef tlb_start_vma
 183 #define tlb_start_vma(tlb, vma) do { } while (0)
 184 #endif
 185
 186 #define __tlb_end_vma(tlb, vma)                                 \
 187         do {                                                    \
 188                 if (!tlb->fullmm && tlb->end) {                 \
 189                         tlb_flush(tlb);                         \
 190                         __tlb_reset_range(tlb);                 \
 191                 }                                               \
 192         } while (0)
 193
 194 #ifndef tlb_end_vma
 195 #define tlb_end_vma     __tlb_end_vma
 196 #endif
 197
 198 #ifndef __tlb_remove_tlb_entry
 199 #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
 200 #endif
 201
 202 /**
 203  * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
 204  *
 205  * Record the fact that pte's were really unmapped by updating the range,
 206  * so we can later optimise away the tlb invalidate.   This helps when
 207  * userspace is unmapping already-unmapped pages, which happens quite a lot.
 208  */
 209 #define tlb_remove_tlb_entry(tlb, ptep, address)                \
 210         do {                                                    \
 211                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 212                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
 213         } while (0)
 214
 215 #define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)             \
 216         do {                                                         \
 217                 __tlb_adjust_range(tlb, address, huge_page_size(h)); \
 218                 __tlb_remove_tlb_entry(tlb, ptep, address);          \
 219         } while (0)
 220
 221 /**
 222  * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation
 223  * This is a nop so far, because only x86 needs it.
 224  */
 225 #ifndef __tlb_remove_pmd_tlb_entry
 226 #define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0)
 227 #endif
 228
 229 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)                    \
 230         do {                                                            \
 231                 __tlb_adjust_range(tlb, address, HPAGE_PMD_SIZE);       \
 232                 __tlb_remove_pmd_tlb_entry(tlb, pmdp, address);         \
 233         } while (0)
 234
 235 /*
 236  * For things like page tables caches (ie caching addresses "inside" the
 237  * page tables, like x86 does), for legacy reasons, flushing an
 238  * individual page had better flush the page table caches behind it. This
 239  * is definitely how x86 works, for example. And if you have an
 240  * architected non-legacy page table cache (which I'm not aware of
 241  * anybody actually doing), you're going to have some architecturally
 242  * explicit flushing for that, likely *separate* from a regular TLB entry
 243  * flush, and thus you'd need more than just some range expansion..
 244  *
 245  * So if we ever find an architecture
 246  * that would want something that odd, I think it is up to that
 247  * architecture to do its own odd thing, not cause pain for others
 248  * http://lkml.kernel.org/r/CA+55aFzBggoXtNXQeng5d_mRoDnaMBE5Y+URs+PHR67nUpMtaw@mail.gmail.com
 249  *
 250  * For now w.r.t page table cache, mark the range_size as PAGE_SIZE
 251  */
 252
 253 #define pte_free_tlb(tlb, ptep, address)                        \
 254         do {                                                    \
 255                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 256                 __pte_free_tlb(tlb, ptep, address);             \
 257         } while (0)
 258
 259 #ifndef __ARCH_HAS_4LEVEL_HACK
 260 #define pud_free_tlb(tlb, pudp, address)                        \
 261         do {                                                    \
 262                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 263                 __pud_free_tlb(tlb, pudp, address);             \
 264         } while (0)
 265 #endif
 266
 267 #define pmd_free_tlb(tlb, pmdp, address)                        \
 268         do {                                                    \
 269                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 270                 __pmd_free_tlb(tlb, pmdp, address);             \
 271         } while (0)
 272
 273 #define tlb_migrate_finish(mm) do {} while (0)
 274
 275 #endif /* _ASM_GENERIC__TLB_H */