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 arch_tlb_gather_mmu(struct mmu_gather *tlb,
 116         struct mm_struct *mm, unsigned long start, unsigned long end);
 117 void tlb_flush_mmu(struct mmu_gather *tlb);
 118 void arch_tlb_finish_mmu(struct mmu_gather *tlb,
 119                          unsigned long start, unsigned long end, bool force);
 120 extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
 121                                    int page_size);
 122
 123 static inline void __tlb_adjust_range(struct mmu_gather *tlb,
 124                                       unsigned long address,
 125                                       unsigned int range_size)
 126 {
 127         tlb->start = min(tlb->start, address);
 128         tlb->end = max(tlb->end, address + range_size);
 129 }
 130
 131 static inline void __tlb_reset_range(struct mmu_gather *tlb)
 132 {
 133         if (tlb->fullmm) {
 134                 tlb->start = tlb->end = ~0;
 135         } else {
 136                 tlb->start = TASK_SIZE;
 137                 tlb->end = 0;
 138         }
 139 }
 140
 141 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 142                                         struct page *page, int page_size)
 143 {
 144         if (__tlb_remove_page_size(tlb, page, page_size))
 145                 tlb_flush_mmu(tlb);
 146 }
 147
 148 static inline bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 149 {
 150         return __tlb_remove_page_size(tlb, page, PAGE_SIZE);
 151 }
 152
 153 /* tlb_remove_page
 154  *      Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
 155  *      required.
 156  */
 157 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 158 {
 159         return tlb_remove_page_size(tlb, page, PAGE_SIZE);
 160 }
 161
 162 #ifndef tlb_remove_check_page_size_change
 163 #define tlb_remove_check_page_size_change tlb_remove_check_page_size_change
 164 static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 165                                                      unsigned int page_size)
 166 {
 167         /*
 168          * We don't care about page size change, just update
 169          * mmu_gather page size here so that debug checks
 170          * doesn't throw false warning.
 171          */
 172 #ifdef CONFIG_DEBUG_VM
 173         tlb->page_size = page_size;
 174 #endif
 175 }
 176 #endif
 177
 178 /*
 179  * In the case of tlb vma handling, we can optimise these away in the
 180  * case where we're doing a full MM flush.  When we're doing a munmap,
 181  * the vmas are adjusted to only cover the region to be torn down.
 182  */
 183 #ifndef tlb_start_vma
 184 #define tlb_start_vma(tlb, vma) do { } while (0)
 185 #endif
 186
 187 #define __tlb_end_vma(tlb, vma)                                 \
 188         do {                                                    \
 189                 if (!tlb->fullmm && tlb->end) {                 \
 190                         tlb_flush(tlb);                         \
 191                         __tlb_reset_range(tlb);                 \
 192                 }                                               \
 193         } while (0)
 194
 195 #ifndef tlb_end_vma
 196 #define tlb_end_vma     __tlb_end_vma
 197 #endif
 198
 199 #ifndef __tlb_remove_tlb_entry
 200 #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
 201 #endif
 202
 203 /**
 204  * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
 205  *
 206  * Record the fact that pte's were really unmapped by updating the range,
 207  * so we can later optimise away the tlb invalidate.   This helps when
 208  * userspace is unmapping already-unmapped pages, which happens quite a lot.
 209  */
 210 #define tlb_remove_tlb_entry(tlb, ptep, address)                \
 211         do {                                                    \
 212                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 213                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
 214         } while (0)
 215
 216 #define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)             \
 217         do {                                                         \
 218                 __tlb_adjust_range(tlb, address, huge_page_size(h)); \
 219                 __tlb_remove_tlb_entry(tlb, ptep, address);          \
 220         } while (0)
 221
 222 /**
 223  * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation
 224  * This is a nop so far, because only x86 needs it.
 225  */
 226 #ifndef __tlb_remove_pmd_tlb_entry
 227 #define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0)
 228 #endif
 229
 230 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)                    \
 231         do {                                                            \
 232                 __tlb_adjust_range(tlb, address, HPAGE_PMD_SIZE);       \
 233                 __tlb_remove_pmd_tlb_entry(tlb, pmdp, address);         \
 234         } while (0)
 235
 236 /**
 237  * tlb_remove_pud_tlb_entry - remember a pud mapping for later tlb
 238  * invalidation. This is a nop so far, because only x86 needs it.
 239  */
 240 #ifndef __tlb_remove_pud_tlb_entry
 241 #define __tlb_remove_pud_tlb_entry(tlb, pudp, address) do {} while (0)
 242 #endif
 243
 244 #define tlb_remove_pud_tlb_entry(tlb, pudp, address)                    \
 245         do {                                                            \
 246                 __tlb_adjust_range(tlb, address, HPAGE_PUD_SIZE);       \
 247                 __tlb_remove_pud_tlb_entry(tlb, pudp, address);         \
 248         } while (0)
 249
 250 /*
 251  * For things like page tables caches (ie caching addresses "inside" the
 252  * page tables, like x86 does), for legacy reasons, flushing an
 253  * individual page had better flush the page table caches behind it. This
 254  * is definitely how x86 works, for example. And if you have an
 255  * architected non-legacy page table cache (which I'm not aware of
 256  * anybody actually doing), you're going to have some architecturally
 257  * explicit flushing for that, likely *separate* from a regular TLB entry
 258  * flush, and thus you'd need more than just some range expansion..
 259  *
 260  * So if we ever find an architecture
 261  * that would want something that odd, I think it is up to that
 262  * architecture to do its own odd thing, not cause pain for others
 263  * http://lkml.kernel.org/r/CA+55aFzBggoXtNXQeng5d_mRoDnaMBE5Y+URs+PHR67nUpMtaw@mail.gmail.com
 264  *
 265  * For now w.r.t page table cache, mark the range_size as PAGE_SIZE
 266  */
 267
 268 #define pte_free_tlb(tlb, ptep, address)                        \
 269         do {                                                    \
 270                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 271                 __pte_free_tlb(tlb, ptep, address);             \
 272         } while (0)
 273
 274 #define pmd_free_tlb(tlb, pmdp, address)                        \
 275         do {                                                    \
 276                 __tlb_adjust_range(tlb, address, PAGE_SIZE);            \
 277                 __pmd_free_tlb(tlb, pmdp, address);             \
 278         } while (0)
 279
 280 #ifndef __ARCH_HAS_4LEVEL_HACK
 281 #define pud_free_tlb(tlb, pudp, address)                        \
 282         do {                                                    \
 283                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 284                 __pud_free_tlb(tlb, pudp, address);             \
 285         } while (0)
 286 #endif
 287
 288 #ifndef __ARCH_HAS_5LEVEL_HACK
 289 #define p4d_free_tlb(tlb, pudp, address)                        \
 290         do {                                                    \
 291                 __tlb_adjust_range(tlb, address, PAGE_SIZE);            \
 292                 __p4d_free_tlb(tlb, pudp, address);             \
 293         } while (0)
 294 #endif
 295
 296 #define tlb_migrate_finish(mm) do {} while (0)
 297
 298 #endif /* _ASM_GENERIC__TLB_H */