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Uwe Zeisbergerf30c2262006-10-03 23:01:26 +02001/* include/asm-generic/tlb.h
Linus Torvalds1da177e2005-04-16 15:20:36 -07002 *
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 *
Peter Zijlstrad16dfc52011-05-24 17:11:45 -07008 * Copyright 2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
9 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 * 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070018#include <linux/swap.h>
Ingo Molnar62152d02008-01-31 22:05:48 +010019#include <asm/pgalloc.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020#include <asm/tlbflush.h>
21
Peter Zijlstra26723912011-05-24 17:12:00 -070022#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
Peter Zijlstrad16dfc52011-05-24 17:11:45 -070065/*
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
Peter Zijlstrae3032972011-05-24 17:12:01 -070071struct 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070081/* struct mmu_gather is an opaque type used by the mm code for passing around
Hugh Dickins15a23ff2005-10-29 18:16:01 -070082 * any data needed by arch specific code for tlb_remove_page.
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 */
84struct mmu_gather {
85 struct mm_struct *mm;
Peter Zijlstra26723912011-05-24 17:12:00 -070086#ifdef CONFIG_HAVE_RCU_TABLE_FREE
87 struct mmu_table_batch *batch;
88#endif
Peter Zijlstrae3032972011-05-24 17:12:01 -070089 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];
Linus Torvalds1da177e2005-04-16 15:20:36 -070097};
98
Peter Zijlstrae3032972011-05-24 17:12:01 -070099/*
100 * For UP we don't need to worry about TLB flush
101 * and page free order so much..
102 */
103#ifdef CONFIG_SMP
104 #define tlb_fast_mode(tlb) (tlb->fast_mode)
105#else
106 #define tlb_fast_mode(tlb) 1
107#endif
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700108
Peter Zijlstrae3032972011-05-24 17:12:01 -0700109static inline int tlb_next_batch(struct mmu_gather *tlb)
110{
111 struct mmu_gather_batch *batch;
112
113 batch = tlb->active;
114 if (batch->next) {
115 tlb->active = batch->next;
116 return 1;
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700117 }
Peter Zijlstrae3032972011-05-24 17:12:01 -0700118
119 batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
120 if (!batch)
121 return 0;
122
123 batch->next = NULL;
124 batch->nr = 0;
125 batch->max = MAX_GATHER_BATCH;
126
127 tlb->active->next = batch;
128 tlb->active = batch;
129
130 return 1;
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700131}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132
133/* tlb_gather_mmu
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700134 * Called to initialize an (on-stack) mmu_gather structure for page-table
135 * tear-down from @mm. The @fullmm argument is used when @mm is without
136 * users and we're going to destroy the full address space (exit/execve).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700137 */
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700138static inline void
139tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm, bool fullmm)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 tlb->mm = mm;
142
Peter Zijlstrae3032972011-05-24 17:12:01 -0700143 tlb->fullmm = fullmm;
144 tlb->need_flush = 0;
145 tlb->fast_mode = (num_possible_cpus() == 1);
146 tlb->local.next = NULL;
147 tlb->local.nr = 0;
148 tlb->local.max = ARRAY_SIZE(tlb->__pages);
149 tlb->active = &tlb->local;
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700150
Peter Zijlstra26723912011-05-24 17:12:00 -0700151#ifdef CONFIG_HAVE_RCU_TABLE_FREE
152 tlb->batch = NULL;
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700153#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154}
155
156static inline void
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700157tlb_flush_mmu(struct mmu_gather *tlb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158{
Peter Zijlstrae3032972011-05-24 17:12:01 -0700159 struct mmu_gather_batch *batch;
160
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 if (!tlb->need_flush)
162 return;
163 tlb->need_flush = 0;
164 tlb_flush(tlb);
Peter Zijlstra26723912011-05-24 17:12:00 -0700165#ifdef CONFIG_HAVE_RCU_TABLE_FREE
166 tlb_table_flush(tlb);
167#endif
Peter Zijlstrae3032972011-05-24 17:12:01 -0700168
169 if (tlb_fast_mode(tlb))
170 return;
171
172 for (batch = &tlb->local; batch; batch = batch->next) {
173 free_pages_and_swap_cache(batch->pages, batch->nr);
174 batch->nr = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 }
Peter Zijlstrae3032972011-05-24 17:12:01 -0700176 tlb->active = &tlb->local;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177}
178
179/* tlb_finish_mmu
180 * Called at the end of the shootdown operation to free up any resources
Hugh Dickins15a23ff2005-10-29 18:16:01 -0700181 * that were required.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182 */
183static inline void
184tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
185{
Peter Zijlstrae3032972011-05-24 17:12:01 -0700186 struct mmu_gather_batch *batch, *next;
187
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700188 tlb_flush_mmu(tlb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189
190 /* keep the page table cache within bounds */
191 check_pgt_cache();
Hugh Dickins15a23ff2005-10-29 18:16:01 -0700192
Peter Zijlstrae3032972011-05-24 17:12:01 -0700193 for (batch = tlb->local.next; batch; batch = next) {
194 next = batch->next;
195 free_pages((unsigned long)batch, 0);
196 }
197 tlb->local.next = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198}
199
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700200/* __tlb_remove_page
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 * Must perform the equivalent to __free_pte(pte_get_and_clear(ptep)), while
202 * handling the additional races in SMP caused by other CPUs caching valid
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700203 * mappings in their TLBs. Returns the number of free page slots left.
204 * When out of page slots we must call tlb_flush_mmu().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 */
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700206static inline int __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207{
Peter Zijlstrae3032972011-05-24 17:12:01 -0700208 struct mmu_gather_batch *batch;
209
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210 tlb->need_flush = 1;
Peter Zijlstrae3032972011-05-24 17:12:01 -0700211
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212 if (tlb_fast_mode(tlb)) {
213 free_page_and_swap_cache(page);
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700214 return 1; /* avoid calling tlb_flush_mmu() */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215 }
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700216
Peter Zijlstrae3032972011-05-24 17:12:01 -0700217 batch = tlb->active;
218 batch->pages[batch->nr++] = page;
219 VM_BUG_ON(batch->nr > batch->max);
220 if (batch->nr == batch->max) {
221 if (!tlb_next_batch(tlb))
222 return 0;
223 }
224
225 return batch->max - batch->nr;
Peter Zijlstrad16dfc52011-05-24 17:11:45 -0700226}
227
228/* tlb_remove_page
229 * Similar to __tlb_remove_page but will call tlb_flush_mmu() itself when
230 * required.
231 */
232static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
233{
234 if (!__tlb_remove_page(tlb, page))
235 tlb_flush_mmu(tlb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236}
237
238/**
239 * tlb_remove_tlb_entry - remember a pte unmapping for later tlb invalidation.
240 *
241 * Record the fact that pte's were really umapped in ->need_flush, so we can
242 * later optimise away the tlb invalidate. This helps when userspace is
243 * unmapping already-unmapped pages, which happens quite a lot.
244 */
245#define tlb_remove_tlb_entry(tlb, ptep, address) \
246 do { \
247 tlb->need_flush = 1; \
248 __tlb_remove_tlb_entry(tlb, ptep, address); \
249 } while (0)
250
Benjamin Herrenschmidt9e1b32c2009-07-22 15:44:28 +1000251#define pte_free_tlb(tlb, ptep, address) \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252 do { \
253 tlb->need_flush = 1; \
Benjamin Herrenschmidt9e1b32c2009-07-22 15:44:28 +1000254 __pte_free_tlb(tlb, ptep, address); \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255 } while (0)
256
257#ifndef __ARCH_HAS_4LEVEL_HACK
Benjamin Herrenschmidt9e1b32c2009-07-22 15:44:28 +1000258#define pud_free_tlb(tlb, pudp, address) \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259 do { \
260 tlb->need_flush = 1; \
Benjamin Herrenschmidt9e1b32c2009-07-22 15:44:28 +1000261 __pud_free_tlb(tlb, pudp, address); \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 } while (0)
263#endif
264
Benjamin Herrenschmidt9e1b32c2009-07-22 15:44:28 +1000265#define pmd_free_tlb(tlb, pmdp, address) \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 do { \
267 tlb->need_flush = 1; \
Benjamin Herrenschmidt9e1b32c2009-07-22 15:44:28 +1000268 __pmd_free_tlb(tlb, pmdp, address); \
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269 } while (0)
270
271#define tlb_migrate_finish(mm) do {} while (0)
272
273#endif /* _ASM_GENERIC__TLB_H */