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 }; 111 112 #define HAVE_GENERIC_MMU_GATHER 113 114 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end); 115 void tlb_flush_mmu(struct mmu_gather *tlb); 116 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, 117 unsigned long end); 118 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page); 119 120 /* tlb_remove_page 121 * Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when 122 * required. 123 */ 124 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page) 125 { 126 if (!__tlb_remove_page(tlb, page)) 127 tlb_flush_mmu(tlb); 128 } 129 130 static inline void __tlb_adjust_range(struct mmu_gather *tlb, 131 unsigned long address) 132 { 133 tlb->start = min(tlb->start, address); 134 tlb->end = max(tlb->end, address + PAGE_SIZE); 135 } 136 137 static inline void __tlb_reset_range(struct mmu_gather *tlb) 138 { 139 if (tlb->fullmm) { 140 tlb->start = tlb->end = ~0; 141 } else { 142 tlb->start = TASK_SIZE; 143 tlb->end = 0; 144 } 145 } 146 147 /* 148 * In the case of tlb vma handling, we can optimise these away in the 149 * case where we're doing a full MM flush. When we're doing a munmap, 150 * the vmas are adjusted to only cover the region to be torn down. 151 */ 152 #ifndef tlb_start_vma 153 #define tlb_start_vma(tlb, vma) do { } while (0) 154 #endif 155 156 #define __tlb_end_vma(tlb, vma) \ 157 do { \ 158 if (!tlb->fullmm && tlb->end) { \ 159 tlb_flush(tlb); \ 160 __tlb_reset_range(tlb); \ 161 } \ 162 } while (0) 163 164 #ifndef tlb_end_vma 165 #define tlb_end_vma __tlb_end_vma 166 #endif 167 168 #ifndef __tlb_remove_tlb_entry 169 #define __tlb_remove_tlb_entry(tlb, ptep, address) do { } while (0) 170 #endif 171 172 /** 173 * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation. 174 * 175 * Record the fact that pte's were really unmapped by updating the range, 176 * so we can later optimise away the tlb invalidate. This helps when 177 * userspace is unmapping already-unmapped pages, which happens quite a lot. 178 */ 179 #define tlb_remove_tlb_entry(tlb, ptep, address) \ 180 do { \ 181 __tlb_adjust_range(tlb, address); \ 182 __tlb_remove_tlb_entry(tlb, ptep, address); \ 183 } while (0) 184 185 /** 186 * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation 187 * This is a nop so far, because only x86 needs it. 188 */ 189 #ifndef __tlb_remove_pmd_tlb_entry 190 #define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0) 191 #endif 192 193 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address) \ 194 do { \ 195 __tlb_adjust_range(tlb, address); \ 196 __tlb_remove_pmd_tlb_entry(tlb, pmdp, address); \ 197 } while (0) 198 199 #define pte_free_tlb(tlb, ptep, address) \ 200 do { \ 201 __tlb_adjust_range(tlb, address); \ 202 __pte_free_tlb(tlb, ptep, address); \ 203 } while (0) 204 205 #ifndef __ARCH_HAS_4LEVEL_HACK 206 #define pud_free_tlb(tlb, pudp, address) \ 207 do { \ 208 __tlb_adjust_range(tlb, address); \ 209 __pud_free_tlb(tlb, pudp, address); \ 210 } while (0) 211 #endif 212 213 #define pmd_free_tlb(tlb, pmdp, address) \ 214 do { \ 215 __tlb_adjust_range(tlb, address); \ 216 __pmd_free_tlb(tlb, pmdp, address); \ 217 } while (0) 218 219 #define tlb_migrate_finish(mm) do {} while (0) 220 221 #endif /* _ASM_GENERIC__TLB_H */ 222