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 long start; 90 unsigned long end; 91 unsigned int need_flush : 1, /* Did free PTEs */ 92 fast_mode : 1; /* No batching */ 93 94 unsigned int fullmm; 95 96 struct mmu_gather_batch *active; 97 struct mmu_gather_batch local; 98 struct page *__pages[MMU_GATHER_BUNDLE]; 99 }; 100 101 #define HAVE_GENERIC_MMU_GATHER 102 103 static inline int tlb_fast_mode(struct mmu_gather *tlb) 104 { 105 #ifdef CONFIG_SMP 106 return tlb->fast_mode; 107 #else 108 /* 109 * For UP we don't need to worry about TLB flush 110 * and page free order so much.. 111 */ 112 return 1; 113 #endif 114 } 115 116 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm); 117 void tlb_flush_mmu(struct mmu_gather *tlb); 118 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, 119 unsigned long end); 120 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page); 121 122 /* tlb_remove_page 123 * Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when 124 * required. 125 */ 126 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page) 127 { 128 if (!__tlb_remove_page(tlb, page)) 129 tlb_flush_mmu(tlb); 130 } 131 132 /** 133 * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation. 134 * 135 * Record the fact that pte's were really umapped in ->need_flush, so we can 136 * later optimise away the tlb invalidate. This helps when userspace is 137 * unmapping already-unmapped pages, which happens quite a lot. 138 */ 139 #define tlb_remove_tlb_entry(tlb, ptep, address) \ 140 do { \ 141 tlb->need_flush = 1; \ 142 __tlb_remove_tlb_entry(tlb, ptep, address); \ 143 } while (0) 144 145 /** 146 * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation 147 * This is a nop so far, because only x86 needs it. 148 */ 149 #ifndef __tlb_remove_pmd_tlb_entry 150 #define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0) 151 #endif 152 153 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address) \ 154 do { \ 155 tlb->need_flush = 1; \ 156 __tlb_remove_pmd_tlb_entry(tlb, pmdp, address); \ 157 } while (0) 158 159 #define pte_free_tlb(tlb, ptep, address) \ 160 do { \ 161 tlb->need_flush = 1; \ 162 __pte_free_tlb(tlb, ptep, address); \ 163 } while (0) 164 165 #ifndef __ARCH_HAS_4LEVEL_HACK 166 #define pud_free_tlb(tlb, pudp, address) \ 167 do { \ 168 tlb->need_flush = 1; \ 169 __pud_free_tlb(tlb, pudp, address); \ 170 } while (0) 171 #endif 172 173 #define pmd_free_tlb(tlb, pmdp, address) \ 174 do { \ 175 tlb->need_flush = 1; \ 176 __pmd_free_tlb(tlb, pmdp, address); \ 177 } while (0) 178 179 #define tlb_migrate_finish(mm) do {} while (0) 180 181 #endif /* _ASM_GENERIC__TLB_H */ 182