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 /* 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 unsigned int need_flush : 1, /* Did free PTEs */ 100 /* we are in the middle of an operation to clear 101 * a full mm and can make some optimizations */ 102 fullmm : 1, 103 /* we have performed an operation which 104 * requires a complete flush of the tlb */ 105 need_flush_all : 1; 106 107 struct mmu_gather_batch *active; 108 struct mmu_gather_batch local; 109 struct page *__pages[MMU_GATHER_BUNDLE]; 110 unsigned int batch_count; 111 }; 112 113 #define HAVE_GENERIC_MMU_GATHER 114 115 void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end); 116 void tlb_flush_mmu(struct mmu_gather *tlb); 117 void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, 118 unsigned long end); 119 int __tlb_remove_page(struct mmu_gather *tlb, struct page *page); 120 121 /* tlb_remove_page 122 * Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when 123 * required. 124 */ 125 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page) 126 { 127 if (!__tlb_remove_page(tlb, page)) 128 tlb_flush_mmu(tlb); 129 } 130 131 /** 132 * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation. 133 * 134 * Record the fact that pte's were really umapped in ->need_flush, so we can 135 * later optimise away the tlb invalidate. This helps when userspace is 136 * unmapping already-unmapped pages, which happens quite a lot. 137 */ 138 #define tlb_remove_tlb_entry(tlb, ptep, address) \ 139 do { \ 140 tlb->need_flush = 1; \ 141 __tlb_remove_tlb_entry(tlb, ptep, address); \ 142 } while (0) 143 144 /** 145 * tlb_remove_pmd_tlb_entry - remember a pmd mapping for later tlb invalidation 146 * This is a nop so far, because only x86 needs it. 147 */ 148 #ifndef __tlb_remove_pmd_tlb_entry 149 #define __tlb_remove_pmd_tlb_entry(tlb, pmdp, address) do {} while (0) 150 #endif 151 152 #define tlb_remove_pmd_tlb_entry(tlb, pmdp, address) \ 153 do { \ 154 tlb->need_flush = 1; \ 155 __tlb_remove_pmd_tlb_entry(tlb, pmdp, address); \ 156 } while (0) 157 158 #define pte_free_tlb(tlb, ptep, address) \ 159 do { \ 160 tlb->need_flush = 1; \ 161 __pte_free_tlb(tlb, ptep, address); \ 162 } while (0) 163 164 #ifndef __ARCH_HAS_4LEVEL_HACK 165 #define pud_free_tlb(tlb, pudp, address) \ 166 do { \ 167 tlb->need_flush = 1; \ 168 __pud_free_tlb(tlb, pudp, address); \ 169 } while (0) 170 #endif 171 172 #define pmd_free_tlb(tlb, pmdp, address) \ 173 do { \ 174 tlb->need_flush = 1; \ 175 __pmd_free_tlb(tlb, pmdp, address); \ 176 } while (0) 177 178 #define tlb_migrate_finish(mm) do {} while (0) 179 180 #endif /* _ASM_GENERIC__TLB_H */ 181