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 <pzijlstr@redhat.com>
   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 /* struct mmu_gather is an opaque type used by the mm code for passing around
  82  * any data needed by arch specific code for tlb_remove_page.
  83  */
  84 struct mmu_gather {
  85         struct mm_struct        *mm;
  86 #ifdef CONFIG_HAVE_RCU_TABLE_FREE
  87         struct mmu_table_batch  *batch;
  88 #endif
  89         unsigned int            need_flush : 1, /* Did free PTEs */
  90                                 fast_mode  : 1; /* No batching   */
  91
  92         unsigned int            fullmm;
  93
  94         struct mmu_gather_batch *active;
  95         struct mmu_gather_batch local;
  96         struct page             *__pages[MMU_GATHER_BUNDLE];
  97 };
  98
  99 #define HAVE_GENERIC_MMU_GATHER
 100
 101 static inline int tlb_fast_mode(struct mmu_gather *tlb)
 102 {
 103 #ifdef CONFIG_SMP
 104         return tlb->fast_mode;
 105 #else
 106         /*
 107          * For UP we don't need to worry about TLB flush
 108          * and page free order so much..
 109          */
 110         return 1;
 111 #endif
 112 }
 113
 114 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
 115 void tlb_flush_mmu(struct mmu_gather *tlb);
 116 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end);
 117 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page);
 118
 119 /* tlb_remove_page
 120  *      Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
 121  *      required.
 122  */
 123 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 124 {
 125         if (!__tlb_remove_page(tlb, page))
 126                 tlb_flush_mmu(tlb);
 127 }
 128
 129 /**
 130  * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
 131  *
 132  * Record the fact that pte's were really umapped in ->need_flush, so we can
 133  * later optimise away the tlb invalidate.   This helps when userspace is
 134  * unmapping already-unmapped pages, which happens quite a lot.
 135  */
 136 #define tlb_remove_tlb_entry(tlb, ptep, address)                \
 137         do {                                                    \
 138                 tlb->need_flush = 1;                            \
 139                 __tlb_remove_tlb_entry(tlb, ptep, address);     \
 140         } while (0)
 141
 142 #define pte_free_tlb(tlb, ptep, address)                        \
 143         do {                                                    \
 144                 tlb->need_flush = 1;                            \
 145                 __pte_free_tlb(tlb, ptep, address);             \
 146         } while (0)
 147
 148 #ifndef __ARCH_HAS_4LEVEL_HACK
 149 #define pud_free_tlb(tlb, pudp, address)                        \
 150         do {                                                    \
 151                 tlb->need_flush = 1;                            \
 152                 __pud_free_tlb(tlb, pudp, address);             \
 153         } while (0)
 154 #endif
 155
 156 #define pmd_free_tlb(tlb, pmdp, address)                        \
 157         do {                                                    \
 158                 tlb->need_flush = 1;                            \
 159                 __pmd_free_tlb(tlb, pmdp, address);             \
 160         } while (0)
 161
 162 #define tlb_migrate_finish(mm) do {} while (0)
 163
 164 #endif /* _ASM_GENERIC__TLB_H */