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/mmu_notifier.h>
  19 #include <linux/swap.h>
  20 #include <asm/pgalloc.h>
  21 #include <asm/tlbflush.h>
  22
  23 #ifdef CONFIG_MMU
  24
  25 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
  26 /*
  27  * Semi RCU freeing of the page directories.
  28  *
  29  * This is needed by some architectures to implement software pagetable walkers.
  30  *
  31  * gup_fast() and other software pagetable walkers do a lockless page-table
  32  * walk and therefore needs some synchronization with the freeing of the page
  33  * directories. The chosen means to accomplish that is by disabling IRQs over
  34  * the walk.
  35  *
  36  * Architectures that use IPIs to flush TLBs will then automagically DTRT,
  37  * since we unlink the page, flush TLBs, free the page. Since the disabling of
  38  * IRQs delays the completion of the TLB flush we can never observe an already
  39  * freed page.
  40  *
  41  * Architectures that do not have this (PPC) need to delay the freeing by some
  42  * other means, this is that means.
  43  *
  44  * What we do is batch the freed directory pages (tables) and RCU free them.
  45  * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
  46  * holds off grace periods.
  47  *
  48  * However, in order to batch these pages we need to allocate storage, this
  49  * allocation is deep inside the MM code and can thus easily fail on memory
  50  * pressure. To guarantee progress we fall back to single table freeing, see
  51  * the implementation of tlb_remove_table_one().
  52  *
  53  */
  54 struct mmu_table_batch {
  55         struct rcu_head         rcu;
  56         unsigned int            nr;
  57         void                    *tables[0];
  58 };
  59
  60 #define MAX_TABLE_BATCH         \
  61         ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))
  62
  63 extern void tlb_table_flush(struct mmu_gather *tlb);
  64 extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
  65
  66 #endif
  67
  68 /*
  69  * If we can't allocate a page to make a big batch of page pointers
  70  * to work on, then just handle a few from the on-stack structure.
  71  */
  72 #define MMU_GATHER_BUNDLE       8
  73
  74 struct mmu_gather_batch {
  75         struct mmu_gather_batch *next;
  76         unsigned int            nr;
  77         unsigned int            max;
  78         struct page             *pages[0];
  79 };
  80
  81 #define MAX_GATHER_BATCH        \
  82         ((PAGE_SIZE - sizeof(struct mmu_gather_batch)) / sizeof(void *))
  83
  84 /*
  85  * Limit the maximum number of mmu_gather batches to reduce a risk of soft
  86  * lockups for non-preemptible kernels on huge machines when a lot of memory
  87  * is zapped during unmapping.
  88  * 10K pages freed at once should be safe even without a preemption point.
  89  */
  90 #define MAX_GATHER_BATCH_COUNT  (10000UL/MAX_GATHER_BATCH)
  91
  92 /* struct mmu_gather is an opaque type used by the mm code for passing around
  93  * any data needed by arch specific code for tlb_remove_page.
  94  */
  95 struct mmu_gather {
  96         struct mm_struct        *mm;
  97 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
  98         struct mmu_table_batch  *batch;
  99 #endif
 100         unsigned long           start;
 101         unsigned long           end;
 102         /*
 103          * we are in the middle of an operation to clear
 104          * a full mm and can make some optimizations
 105          */
 106         unsigned int            fullmm : 1;
 107
 108         /*
 109          * we have performed an operation which
 110          * requires a complete flush of the tlb
 111          */
 112         unsigned int            need_flush_all : 1;
 113
 114         /*
 115          * we have removed page directories
 116          */
 117         unsigned int            freed_tables : 1;
 118
 119         /*
 120          * at which levels have we cleared entries?
 121          */
 122         unsigned int            cleared_ptes : 1;
 123         unsigned int            cleared_pmds : 1;
 124         unsigned int            cleared_puds : 1;
 125         unsigned int            cleared_p4ds : 1;
 126
 127         struct mmu_gather_batch *active;
 128         struct mmu_gather_batch local;
 129         struct page             *__pages[MMU_GATHER_BUNDLE];
 130         unsigned int            batch_count;
 131         int page_size;
 132 };
 133
 134 #define HAVE_GENERIC_MMU_GATHER
 135
 136 void arch_tlb_gather_mmu(struct mmu_gather *tlb,
 137         struct mm_struct *mm, unsigned long start, unsigned long end);
 138 void tlb_flush_mmu(struct mmu_gather *tlb);
 139 void arch_tlb_finish_mmu(struct mmu_gather *tlb,
 140                          unsigned long start, unsigned long end, bool force);
 141 void tlb_flush_mmu_free(struct mmu_gather *tlb);
 142 extern bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page,
 143                                    int page_size);
 144
 145 static inline void __tlb_adjust_range(struct mmu_gather *tlb,
 146                                       unsigned long address,
 147                                       unsigned int range_size)
 148 {
 149         tlb->start = min(tlb->start, address);
 150         tlb->end = max(tlb->end, address + range_size);
 151 }
 152
 153 static inline void __tlb_reset_range(struct mmu_gather *tlb)
 154 {
 155         if (tlb->fullmm) {
 156                 tlb->start = tlb->end = ~0;
 157         } else {
 158                 tlb->start = TASK_SIZE;
 159                 tlb->end = 0;
 160         }
 161         tlb->freed_tables = 0;
 162         tlb->cleared_ptes = 0;
 163         tlb->cleared_pmds = 0;
 164         tlb->cleared_puds = 0;
 165         tlb->cleared_p4ds = 0;
 166 }
 167
 168 static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
 169 {
 170         if (!tlb->end)
 171                 return;
 172
 173         tlb_flush(tlb);
 174         mmu_notifier_invalidate_range(tlb->mm, tlb->start, tlb->end);
 175         __tlb_reset_range(tlb);
 176 }
 177
 178 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 179                                         struct page *page, int page_size)
 180 {
 181         if (__tlb_remove_page_size(tlb, page, page_size))
 182                 tlb_flush_mmu(tlb);
 183 }
 184
 185 static inline bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 186 {
 187         return __tlb_remove_page_size(tlb, page, PAGE_SIZE);
 188 }
 189
 190 /* tlb_remove_page
 191  *      Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
 192  *      required.
 193  */
 194 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 195 {
 196         return tlb_remove_page_size(tlb, page, PAGE_SIZE);
 197 }
 198
 199 #ifndef tlb_remove_check_page_size_change
 200 #define tlb_remove_check_page_size_change tlb_remove_check_page_size_change
 201 static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
 202                                                      unsigned int page_size)
 203 {
 204         /*
 205          * We don't care about page size change, just update
 206          * mmu_gather page size here so that debug checks
 207          * doesn't throw false warning.
 208          */
 209 #ifdef CONFIG_DEBUG_VM
 210         tlb->page_size = page_size;
 211 #endif
 212 }
 213 #endif
 214
 215 static inline unsigned long tlb_get_unmap_shift(struct mmu_gather *tlb)
 216 {
 217         if (tlb->cleared_ptes)
 218                 return PAGE_SHIFT;
 219         if (tlb->cleared_pmds)
 220                 return PMD_SHIFT;
 221         if (tlb->cleared_puds)
 222                 return PUD_SHIFT;
 223         if (tlb->cleared_p4ds)
 224                 return P4D_SHIFT;
 225
 226         return PAGE_SHIFT;
 227 }
 228
 229 static inline unsigned long tlb_get_unmap_size(struct mmu_gather *tlb)
 230 {
 231         return 1UL << tlb_get_unmap_shift(tlb);
 232 }
 233
 234 /*
 235  * In the case of tlb vma handling, we can optimise these away in the
 236  * case where we're doing a full MM flush.  When we're doing a munmap,
 237  * the vmas are adjusted to only cover the region to be torn down.
 238  */
 239 #ifndef tlb_start_vma
 240 #define tlb_start_vma(tlb, vma) do { } while (0)
 241 #endif
 242
 243 #define __tlb_end_vma(tlb, vma)                                 \
 244         do {                                                    \
 245                 if (!tlb->fullmm)                               \
 246                         tlb_flush_mmu_tlbonly(tlb);             \
 247         } while (0)
 248
 249 #ifndef tlb_end_vma
 250 #define tlb_end_vma     __tlb_end_vma
 251 #endif
 252
 253 #ifndef __tlb_remove_tlb_entry
 254 #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0)
 255 #endif
 256
 257 /**
 258  * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
 259  *
 260  * Record the fact that pte's were really unmapped by updating the range,
 261  * so we can later optimise away the tlb invalidate.   This helps when
 262  * userspace is unmapping already-unmapped pages, which happens quite a lot.
 263  */
 264 #define tlb_remove_tlb_entry(tlb, ptep, address)                \
 265         do {                                                    \
 266                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 267                 tlb->cleared_ptes = 1;                          \
 268                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
 269         } while (0)
 270
 271 #define tlb_remove_huge_tlb_entry(h, tlb, ptep, address)        \
 272         do {                                                    \
 273                 unsigned long _sz = huge_page_size(h);          \
 274                 __tlb_adjust_range(tlb, address, _sz);          \
 275                 if (_sz == PMD_SIZE)                            \
 276                         tlb->cleared_pmds = 1;                  \
 277                 else if (_sz == PUD_SIZE)                       \
 278                         tlb->cleared_puds = 1;                  \
 279                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
 280         } while (0)
 281
 282 /**
 283  * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation
 284  * This is a nop so far, because only x86 needs it.
 285  */
 286 #ifndef __tlb_remove_pmd_tlb_entry
 287 #define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0)
 288 #endif
 289
 290 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address)                    \
 291         do {                                                            \
 292                 __tlb_adjust_range(tlb, address, HPAGE_PMD_SIZE);       \
 293                 tlb->cleared_pmds = 1;                                  \
 294                 __tlb_remove_pmd_tlb_entry(tlb, pmdp, address);         \
 295         } while (0)
 296
 297 /**
 298  * tlb_remove_pud_tlb_entry - remember a pud mapping for later tlb
 299  * invalidation. This is a nop so far, because only x86 needs it.
 300  */
 301 #ifndef __tlb_remove_pud_tlb_entry
 302 #define __tlb_remove_pud_tlb_entry(tlb, pudp, address) do {} while (0)
 303 #endif
 304
 305 #define tlb_remove_pud_tlb_entry(tlb, pudp, address)                    \
 306         do {                                                            \
 307                 __tlb_adjust_range(tlb, address, HPAGE_PUD_SIZE);       \
 308                 tlb->cleared_puds = 1;                                  \
 309                 __tlb_remove_pud_tlb_entry(tlb, pudp, address);         \
 310         } while (0)
 311
 312 /*
 313  * For things like page tables caches (ie caching addresses "inside" the
 314  * page tables, like x86 does), for legacy reasons, flushing an
 315  * individual page had better flush the page table caches behind it. This
 316  * is definitely how x86 works, for example. And if you have an
 317  * architected non-legacy page table cache (which I'm not aware of
 318  * anybody actually doing), you're going to have some architecturally
 319  * explicit flushing for that, likely *separate* from a regular TLB entry
 320  * flush, and thus you'd need more than just some range expansion..
 321  *
 322  * So if we ever find an architecture
 323  * that would want something that odd, I think it is up to that
 324  * architecture to do its own odd thing, not cause pain for others
 325  * http://lkml.kernel.org/r/CA+55aFzBggoXtNXQeng5d_mRoDnaMBE5Y+URs+PHR67nUpMtaw@mail.gmail.com
 326  *
 327  * For now w.r.t page table cache, mark the range_size as PAGE_SIZE
 328  */
 329
 330 #ifndef pte_free_tlb
 331 #define pte_free_tlb(tlb, ptep, address)                        \
 332         do {                                                    \
 333                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 334                 tlb->freed_tables = 1;                          \
 335                 tlb->cleared_pmds = 1;                          \
 336                 __pte_free_tlb(tlb, ptep, address);             \
 337         } while (0)
 338 #endif
 339
 340 #ifndef pmd_free_tlb
 341 #define pmd_free_tlb(tlb, pmdp, address)                        \
 342         do {                                                    \
 343                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 344                 tlb->freed_tables = 1;                          \
 345                 tlb->cleared_puds = 1;                          \
 346                 __pmd_free_tlb(tlb, pmdp, address);             \
 347         } while (0)
 348 #endif
 349
 350 #ifndef __ARCH_HAS_4LEVEL_HACK
 351 #ifndef pud_free_tlb
 352 #define pud_free_tlb(tlb, pudp, address)                        \
 353         do {                                                    \
 354                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 355                 tlb->freed_tables = 1;                          \
 356                 tlb->cleared_p4ds = 1;                          \
 357                 __pud_free_tlb(tlb, pudp, address);             \
 358         } while (0)
 359 #endif
 360 #endif
 361
 362 #ifndef __ARCH_HAS_5LEVEL_HACK
 363 #ifndef p4d_free_tlb
 364 #define p4d_free_tlb(tlb, pudp, address)                        \
 365         do {                                                    \
 366                 __tlb_adjust_range(tlb, address, PAGE_SIZE);    \
 367                 tlb->freed_tables = 1;                          \
 368                 __p4d_free_tlb(tlb, pudp, address);             \
 369         } while (0)
 370 #endif
 371 #endif
 372
 373 #endif /* CONFIG_MMU */
 374
 375 #define tlb_migrate_finish(mm) do {} while (0)
 376
 377 #endif /* _ASM_GENERIC__TLB_H */