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1#include <linux/gfp.h>
2#include <linux/highmem.h>
3#include <linux/kernel.h>
4#include <linux/mmdebug.h>
5#include <linux/mm_types.h>
6#include <linux/pagemap.h>
7#include <linux/rcupdate.h>
8#include <linux/smp.h>
9#include <linux/swap.h>
10
11#include <asm/pgalloc.h>
12#include <asm/tlb.h>
13
14#ifndef CONFIG_MMU_GATHER_NO_GATHER
15
16static bool tlb_next_batch(struct mmu_gather *tlb)
17{
18 struct mmu_gather_batch *batch;
19
20 batch = tlb->active;
21 if (batch->next) {
22 tlb->active = batch->next;
23 return true;
24 }
25
26 if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
27 return false;
28
29 batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
30 if (!batch)
31 return false;
32
33 tlb->batch_count++;
34 batch->next = NULL;
35 batch->nr = 0;
36 batch->max = MAX_GATHER_BATCH;
37
38 tlb->active->next = batch;
39 tlb->active = batch;
40
41 return true;
42}
43
44static void tlb_batch_pages_flush(struct mmu_gather *tlb)
45{
46 struct mmu_gather_batch *batch;
47
48 for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
49 free_pages_and_swap_cache(batch->pages, batch->nr);
50 batch->nr = 0;
51 }
52 tlb->active = &tlb->local;
53}
54
55static void tlb_batch_list_free(struct mmu_gather *tlb)
56{
57 struct mmu_gather_batch *batch, *next;
58
59 for (batch = tlb->local.next; batch; batch = next) {
60 next = batch->next;
61 free_pages((unsigned long)batch, 0);
62 }
63 tlb->local.next = NULL;
64}
65
66bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_size)
67{
68 struct mmu_gather_batch *batch;
69
70 VM_BUG_ON(!tlb->end);
71
72#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
73 VM_WARN_ON(tlb->page_size != page_size);
74#endif
75
76 batch = tlb->active;
77 /*
78 * Add the page and check if we are full. If so
79 * force a flush.
80 */
81 batch->pages[batch->nr++] = page;
82 if (batch->nr == batch->max) {
83 if (!tlb_next_batch(tlb))
84 return true;
85 batch = tlb->active;
86 }
87 VM_BUG_ON_PAGE(batch->nr > batch->max, page);
88
89 return false;
90}
91
92#endif /* MMU_GATHER_NO_GATHER */
93
94#ifdef CONFIG_MMU_GATHER_TABLE_FREE
95
96static void __tlb_remove_table_free(struct mmu_table_batch *batch)
97{
98 int i;
99
100 for (i = 0; i < batch->nr; i++)
101 __tlb_remove_table(batch->tables[i]);
102
103 free_page((unsigned long)batch);
104}
105
106#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
107
108/*
109 * Semi RCU freeing of the page directories.
110 *
111 * This is needed by some architectures to implement software pagetable walkers.
112 *
113 * gup_fast() and other software pagetable walkers do a lockless page-table
114 * walk and therefore needs some synchronization with the freeing of the page
115 * directories. The chosen means to accomplish that is by disabling IRQs over
116 * the walk.
117 *
118 * Architectures that use IPIs to flush TLBs will then automagically DTRT,
119 * since we unlink the page, flush TLBs, free the page. Since the disabling of
120 * IRQs delays the completion of the TLB flush we can never observe an already
121 * freed page.
122 *
123 * Architectures that do not have this (PPC) need to delay the freeing by some
124 * other means, this is that means.
125 *
126 * What we do is batch the freed directory pages (tables) and RCU free them.
127 * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
128 * holds off grace periods.
129 *
130 * However, in order to batch these pages we need to allocate storage, this
131 * allocation is deep inside the MM code and can thus easily fail on memory
132 * pressure. To guarantee progress we fall back to single table freeing, see
133 * the implementation of tlb_remove_table_one().
134 *
135 */
136
137static void tlb_remove_table_smp_sync(void *arg)
138{
139 /* Simply deliver the interrupt */
140}
141
142static void tlb_remove_table_sync_one(void)
143{
144 /*
145 * This isn't an RCU grace period and hence the page-tables cannot be
146 * assumed to be actually RCU-freed.
147 *
148 * It is however sufficient for software page-table walkers that rely on
149 * IRQ disabling.
150 */
151 smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
152}
153
154static void tlb_remove_table_rcu(struct rcu_head *head)
155{
156 __tlb_remove_table_free(container_of(head, struct mmu_table_batch, rcu));
157}
158
159static void tlb_remove_table_free(struct mmu_table_batch *batch)
160{
161 call_rcu(&batch->rcu, tlb_remove_table_rcu);
162}
163
164#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
165
166static void tlb_remove_table_sync_one(void) { }
167
168static void tlb_remove_table_free(struct mmu_table_batch *batch)
169{
170 __tlb_remove_table_free(batch);
171}
172
173#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */
174
175/*
176 * If we want tlb_remove_table() to imply TLB invalidates.
177 */
178static inline void tlb_table_invalidate(struct mmu_gather *tlb)
179{
180 if (tlb_needs_table_invalidate()) {
181 /*
182 * Invalidate page-table caches used by hardware walkers. Then
183 * we still need to RCU-sched wait while freeing the pages
184 * because software walkers can still be in-flight.
185 */
186 tlb_flush_mmu_tlbonly(tlb);
187 }
188}
189
190static void tlb_remove_table_one(void *table)
191{
192 tlb_remove_table_sync_one();
193 __tlb_remove_table(table);
194}
195
196static void tlb_table_flush(struct mmu_gather *tlb)
197{
198 struct mmu_table_batch **batch = &tlb->batch;
199
200 if (*batch) {
201 tlb_table_invalidate(tlb);
202 tlb_remove_table_free(*batch);
203 *batch = NULL;
204 }
205}
206
207void tlb_remove_table(struct mmu_gather *tlb, void *table)
208{
209 struct mmu_table_batch **batch = &tlb->batch;
210
211 if (*batch == NULL) {
212 *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
213 if (*batch == NULL) {
214 tlb_table_invalidate(tlb);
215 tlb_remove_table_one(table);
216 return;
217 }
218 (*batch)->nr = 0;
219 }
220
221 (*batch)->tables[(*batch)->nr++] = table;
222 if ((*batch)->nr == MAX_TABLE_BATCH)
223 tlb_table_flush(tlb);
224}
225
226static inline void tlb_table_init(struct mmu_gather *tlb)
227{
228 tlb->batch = NULL;
229}
230
231#else /* !CONFIG_MMU_GATHER_TABLE_FREE */
232
233static inline void tlb_table_flush(struct mmu_gather *tlb) { }
234static inline void tlb_table_init(struct mmu_gather *tlb) { }
235
236#endif /* CONFIG_MMU_GATHER_TABLE_FREE */
237
238static void tlb_flush_mmu_free(struct mmu_gather *tlb)
239{
240 tlb_table_flush(tlb);
241#ifndef CONFIG_MMU_GATHER_NO_GATHER
242 tlb_batch_pages_flush(tlb);
243#endif
244}
245
246void tlb_flush_mmu(struct mmu_gather *tlb)
247{
248 tlb_flush_mmu_tlbonly(tlb);
249 tlb_flush_mmu_free(tlb);
250}
251
252/**
253 * tlb_gather_mmu - initialize an mmu_gather structure for page-table tear-down
254 * @tlb: the mmu_gather structure to initialize
255 * @mm: the mm_struct of the target address space
256 * @start: start of the region that will be removed from the page-table
257 * @end: end of the region that will be removed from the page-table
258 *
259 * Called to initialize an (on-stack) mmu_gather structure for page-table
260 * tear-down from @mm. The @start and @end are set to 0 and -1
261 * respectively when @mm is without users and we're going to destroy
262 * the full address space (exit/execve).
263 */
264void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
265 unsigned long start, unsigned long end)
266{
267 tlb->mm = mm;
268
269 /* Is it from 0 to ~0? */
270 tlb->fullmm = !(start | (end+1));
271
272#ifndef CONFIG_MMU_GATHER_NO_GATHER
273 tlb->need_flush_all = 0;
274 tlb->local.next = NULL;
275 tlb->local.nr = 0;
276 tlb->local.max = ARRAY_SIZE(tlb->__pages);
277 tlb->active = &tlb->local;
278 tlb->batch_count = 0;
279#endif
280
281 tlb_table_init(tlb);
282#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
283 tlb->page_size = 0;
284#endif
285
286 __tlb_reset_range(tlb);
287 inc_tlb_flush_pending(tlb->mm);
288}
289
290/**
291 * tlb_finish_mmu - finish an mmu_gather structure
292 * @tlb: the mmu_gather structure to finish
293 * @start: start of the region that will be removed from the page-table
294 * @end: end of the region that will be removed from the page-table
295 *
296 * Called at the end of the shootdown operation to free up any resources that
297 * were required.
298 */
299void tlb_finish_mmu(struct mmu_gather *tlb,
300 unsigned long start, unsigned long end)
301{
302 /*
303 * If there are parallel threads are doing PTE changes on same range
304 * under non-exclusive lock (e.g., mmap_lock read-side) but defer TLB
305 * flush by batching, one thread may end up seeing inconsistent PTEs
306 * and result in having stale TLB entries. So flush TLB forcefully
307 * if we detect parallel PTE batching threads.
308 *
309 * However, some syscalls, e.g. munmap(), may free page tables, this
310 * needs force flush everything in the given range. Otherwise this
311 * may result in having stale TLB entries for some architectures,
312 * e.g. aarch64, that could specify flush what level TLB.
313 */
314 if (mm_tlb_flush_nested(tlb->mm)) {
315 /*
316 * The aarch64 yields better performance with fullmm by
317 * avoiding multiple CPUs spamming TLBI messages at the
318 * same time.
319 *
320 * On x86 non-fullmm doesn't yield significant difference
321 * against fullmm.
322 */
323 tlb->fullmm = 1;
324 __tlb_reset_range(tlb);
325 tlb->freed_tables = 1;
326 }
327
328 tlb_flush_mmu(tlb);
329
330#ifndef CONFIG_MMU_GATHER_NO_GATHER
331 tlb_batch_list_free(tlb);
332#endif
333 dec_tlb_flush_pending(tlb->mm);
334}
1#include <linux/gfp.h>
2#include <linux/highmem.h>
3#include <linux/kernel.h>
4#include <linux/mmdebug.h>
5#include <linux/mm_types.h>
6#include <linux/mm_inline.h>
7#include <linux/pagemap.h>
8#include <linux/rcupdate.h>
9#include <linux/smp.h>
10#include <linux/swap.h>
11#include <linux/rmap.h>
12
13#include <asm/pgalloc.h>
14#include <asm/tlb.h>
15
16#ifndef CONFIG_MMU_GATHER_NO_GATHER
17
18static bool tlb_next_batch(struct mmu_gather *tlb)
19{
20 struct mmu_gather_batch *batch;
21
22 /* Limit batching if we have delayed rmaps pending */
23 if (tlb->delayed_rmap && tlb->active != &tlb->local)
24 return false;
25
26 batch = tlb->active;
27 if (batch->next) {
28 tlb->active = batch->next;
29 return true;
30 }
31
32 if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
33 return false;
34
35 batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
36 if (!batch)
37 return false;
38
39 tlb->batch_count++;
40 batch->next = NULL;
41 batch->nr = 0;
42 batch->max = MAX_GATHER_BATCH;
43
44 tlb->active->next = batch;
45 tlb->active = batch;
46
47 return true;
48}
49
50#ifdef CONFIG_SMP
51static void tlb_flush_rmap_batch(struct mmu_gather_batch *batch, struct vm_area_struct *vma)
52{
53 for (int i = 0; i < batch->nr; i++) {
54 struct encoded_page *enc = batch->encoded_pages[i];
55
56 if (encoded_page_flags(enc)) {
57 struct page *page = encoded_page_ptr(enc);
58 page_remove_rmap(page, vma, false);
59 }
60 }
61}
62
63/**
64 * tlb_flush_rmaps - do pending rmap removals after we have flushed the TLB
65 * @tlb: the current mmu_gather
66 *
67 * Note that because of how tlb_next_batch() above works, we will
68 * never start multiple new batches with pending delayed rmaps, so
69 * we only need to walk through the current active batch and the
70 * original local one.
71 */
72void tlb_flush_rmaps(struct mmu_gather *tlb, struct vm_area_struct *vma)
73{
74 if (!tlb->delayed_rmap)
75 return;
76
77 tlb_flush_rmap_batch(&tlb->local, vma);
78 if (tlb->active != &tlb->local)
79 tlb_flush_rmap_batch(tlb->active, vma);
80 tlb->delayed_rmap = 0;
81}
82#endif
83
84static void tlb_batch_pages_flush(struct mmu_gather *tlb)
85{
86 struct mmu_gather_batch *batch;
87
88 for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
89 struct encoded_page **pages = batch->encoded_pages;
90
91 do {
92 /*
93 * limit free batch count when PAGE_SIZE > 4K
94 */
95 unsigned int nr = min(512U, batch->nr);
96
97 free_pages_and_swap_cache(pages, nr);
98 pages += nr;
99 batch->nr -= nr;
100
101 cond_resched();
102 } while (batch->nr);
103 }
104 tlb->active = &tlb->local;
105}
106
107static void tlb_batch_list_free(struct mmu_gather *tlb)
108{
109 struct mmu_gather_batch *batch, *next;
110
111 for (batch = tlb->local.next; batch; batch = next) {
112 next = batch->next;
113 free_pages((unsigned long)batch, 0);
114 }
115 tlb->local.next = NULL;
116}
117
118bool __tlb_remove_page_size(struct mmu_gather *tlb, struct encoded_page *page, int page_size)
119{
120 struct mmu_gather_batch *batch;
121
122 VM_BUG_ON(!tlb->end);
123
124#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
125 VM_WARN_ON(tlb->page_size != page_size);
126#endif
127
128 batch = tlb->active;
129 /*
130 * Add the page and check if we are full. If so
131 * force a flush.
132 */
133 batch->encoded_pages[batch->nr++] = page;
134 if (batch->nr == batch->max) {
135 if (!tlb_next_batch(tlb))
136 return true;
137 batch = tlb->active;
138 }
139 VM_BUG_ON_PAGE(batch->nr > batch->max, encoded_page_ptr(page));
140
141 return false;
142}
143
144#endif /* MMU_GATHER_NO_GATHER */
145
146#ifdef CONFIG_MMU_GATHER_TABLE_FREE
147
148static void __tlb_remove_table_free(struct mmu_table_batch *batch)
149{
150 int i;
151
152 for (i = 0; i < batch->nr; i++)
153 __tlb_remove_table(batch->tables[i]);
154
155 free_page((unsigned long)batch);
156}
157
158#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
159
160/*
161 * Semi RCU freeing of the page directories.
162 *
163 * This is needed by some architectures to implement software pagetable walkers.
164 *
165 * gup_fast() and other software pagetable walkers do a lockless page-table
166 * walk and therefore needs some synchronization with the freeing of the page
167 * directories. The chosen means to accomplish that is by disabling IRQs over
168 * the walk.
169 *
170 * Architectures that use IPIs to flush TLBs will then automagically DTRT,
171 * since we unlink the page, flush TLBs, free the page. Since the disabling of
172 * IRQs delays the completion of the TLB flush we can never observe an already
173 * freed page.
174 *
175 * Architectures that do not have this (PPC) need to delay the freeing by some
176 * other means, this is that means.
177 *
178 * What we do is batch the freed directory pages (tables) and RCU free them.
179 * We use the sched RCU variant, as that guarantees that IRQ/preempt disabling
180 * holds off grace periods.
181 *
182 * However, in order to batch these pages we need to allocate storage, this
183 * allocation is deep inside the MM code and can thus easily fail on memory
184 * pressure. To guarantee progress we fall back to single table freeing, see
185 * the implementation of tlb_remove_table_one().
186 *
187 */
188
189static void tlb_remove_table_smp_sync(void *arg)
190{
191 /* Simply deliver the interrupt */
192}
193
194void tlb_remove_table_sync_one(void)
195{
196 /*
197 * This isn't an RCU grace period and hence the page-tables cannot be
198 * assumed to be actually RCU-freed.
199 *
200 * It is however sufficient for software page-table walkers that rely on
201 * IRQ disabling.
202 */
203 smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
204}
205
206static void tlb_remove_table_rcu(struct rcu_head *head)
207{
208 __tlb_remove_table_free(container_of(head, struct mmu_table_batch, rcu));
209}
210
211static void tlb_remove_table_free(struct mmu_table_batch *batch)
212{
213 call_rcu(&batch->rcu, tlb_remove_table_rcu);
214}
215
216#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
217
218static void tlb_remove_table_free(struct mmu_table_batch *batch)
219{
220 __tlb_remove_table_free(batch);
221}
222
223#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */
224
225/*
226 * If we want tlb_remove_table() to imply TLB invalidates.
227 */
228static inline void tlb_table_invalidate(struct mmu_gather *tlb)
229{
230 if (tlb_needs_table_invalidate()) {
231 /*
232 * Invalidate page-table caches used by hardware walkers. Then
233 * we still need to RCU-sched wait while freeing the pages
234 * because software walkers can still be in-flight.
235 */
236 tlb_flush_mmu_tlbonly(tlb);
237 }
238}
239
240static void tlb_remove_table_one(void *table)
241{
242 tlb_remove_table_sync_one();
243 __tlb_remove_table(table);
244}
245
246static void tlb_table_flush(struct mmu_gather *tlb)
247{
248 struct mmu_table_batch **batch = &tlb->batch;
249
250 if (*batch) {
251 tlb_table_invalidate(tlb);
252 tlb_remove_table_free(*batch);
253 *batch = NULL;
254 }
255}
256
257void tlb_remove_table(struct mmu_gather *tlb, void *table)
258{
259 struct mmu_table_batch **batch = &tlb->batch;
260
261 if (*batch == NULL) {
262 *batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
263 if (*batch == NULL) {
264 tlb_table_invalidate(tlb);
265 tlb_remove_table_one(table);
266 return;
267 }
268 (*batch)->nr = 0;
269 }
270
271 (*batch)->tables[(*batch)->nr++] = table;
272 if ((*batch)->nr == MAX_TABLE_BATCH)
273 tlb_table_flush(tlb);
274}
275
276static inline void tlb_table_init(struct mmu_gather *tlb)
277{
278 tlb->batch = NULL;
279}
280
281#else /* !CONFIG_MMU_GATHER_TABLE_FREE */
282
283static inline void tlb_table_flush(struct mmu_gather *tlb) { }
284static inline void tlb_table_init(struct mmu_gather *tlb) { }
285
286#endif /* CONFIG_MMU_GATHER_TABLE_FREE */
287
288static void tlb_flush_mmu_free(struct mmu_gather *tlb)
289{
290 tlb_table_flush(tlb);
291#ifndef CONFIG_MMU_GATHER_NO_GATHER
292 tlb_batch_pages_flush(tlb);
293#endif
294}
295
296void tlb_flush_mmu(struct mmu_gather *tlb)
297{
298 tlb_flush_mmu_tlbonly(tlb);
299 tlb_flush_mmu_free(tlb);
300}
301
302static void __tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
303 bool fullmm)
304{
305 tlb->mm = mm;
306 tlb->fullmm = fullmm;
307
308#ifndef CONFIG_MMU_GATHER_NO_GATHER
309 tlb->need_flush_all = 0;
310 tlb->local.next = NULL;
311 tlb->local.nr = 0;
312 tlb->local.max = ARRAY_SIZE(tlb->__pages);
313 tlb->active = &tlb->local;
314 tlb->batch_count = 0;
315#endif
316 tlb->delayed_rmap = 0;
317
318 tlb_table_init(tlb);
319#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
320 tlb->page_size = 0;
321#endif
322
323 __tlb_reset_range(tlb);
324 inc_tlb_flush_pending(tlb->mm);
325}
326
327/**
328 * tlb_gather_mmu - initialize an mmu_gather structure for page-table tear-down
329 * @tlb: the mmu_gather structure to initialize
330 * @mm: the mm_struct of the target address space
331 *
332 * Called to initialize an (on-stack) mmu_gather structure for page-table
333 * tear-down from @mm.
334 */
335void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm)
336{
337 __tlb_gather_mmu(tlb, mm, false);
338}
339
340/**
341 * tlb_gather_mmu_fullmm - initialize an mmu_gather structure for page-table tear-down
342 * @tlb: the mmu_gather structure to initialize
343 * @mm: the mm_struct of the target address space
344 *
345 * In this case, @mm is without users and we're going to destroy the
346 * full address space (exit/execve).
347 *
348 * Called to initialize an (on-stack) mmu_gather structure for page-table
349 * tear-down from @mm.
350 */
351void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm)
352{
353 __tlb_gather_mmu(tlb, mm, true);
354}
355
356/**
357 * tlb_finish_mmu - finish an mmu_gather structure
358 * @tlb: the mmu_gather structure to finish
359 *
360 * Called at the end of the shootdown operation to free up any resources that
361 * were required.
362 */
363void tlb_finish_mmu(struct mmu_gather *tlb)
364{
365 /*
366 * If there are parallel threads are doing PTE changes on same range
367 * under non-exclusive lock (e.g., mmap_lock read-side) but defer TLB
368 * flush by batching, one thread may end up seeing inconsistent PTEs
369 * and result in having stale TLB entries. So flush TLB forcefully
370 * if we detect parallel PTE batching threads.
371 *
372 * However, some syscalls, e.g. munmap(), may free page tables, this
373 * needs force flush everything in the given range. Otherwise this
374 * may result in having stale TLB entries for some architectures,
375 * e.g. aarch64, that could specify flush what level TLB.
376 */
377 if (mm_tlb_flush_nested(tlb->mm)) {
378 /*
379 * The aarch64 yields better performance with fullmm by
380 * avoiding multiple CPUs spamming TLBI messages at the
381 * same time.
382 *
383 * On x86 non-fullmm doesn't yield significant difference
384 * against fullmm.
385 */
386 tlb->fullmm = 1;
387 __tlb_reset_range(tlb);
388 tlb->freed_tables = 1;
389 }
390
391 tlb_flush_mmu(tlb);
392
393#ifndef CONFIG_MMU_GATHER_NO_GATHER
394 tlb_batch_list_free(tlb);
395#endif
396 dec_tlb_flush_pending(tlb->mm);
397}