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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 */
51struct 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
60extern void tlb_table_flush(struct mmu_gather *tlb);
61extern 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
71struct 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 */
84struct 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
101static 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
114void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm);
115void tlb_flush_mmu(struct mmu_gather *tlb);
116void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end);
117int __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 */
123static 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 */
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 */
51struct 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
60extern void tlb_table_flush(struct mmu_gather *tlb);
61extern 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
71struct 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 */
92struct 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
114void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, unsigned long start, unsigned long end);
115void tlb_flush_mmu(struct mmu_gather *tlb);
116void tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start,
117 unsigned long end);
118int __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 */
124static 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
130static 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
137static 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 */