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 */ 299