summaryrefslogtreecommitdiff
path: root/mm/mmu_gather.c
blob: a28c74328085d6ca32325a9f216fc59a608da574 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
#include <linux/gfp.h>
#include <linux/highmem.h>
#include <linux/kernel.h>
#include <linux/mmdebug.h>
#include <linux/mm_types.h>
#include <linux/pagemap.h>
#include <linux/rcupdate.h>
#include <linux/smp.h>
#include <linux/swap.h>

#include <asm/pgalloc.h>
#include <asm/tlb.h>

#ifndef CONFIG_MMU_GATHER_NO_GATHER

static bool tlb_next_batch(struct mmu_gather *tlb)
{
	struct mmu_gather_batch *batch;

	batch = tlb->active;
	if (batch->next) {
		tlb->active = batch->next;
		return true;
	}

	if (tlb->batch_count == MAX_GATHER_BATCH_COUNT)
		return false;

	batch = (void *)__get_free_pages(GFP_NOWAIT | __GFP_NOWARN, 0);
	if (!batch)
		return false;

	tlb->batch_count++;
	batch->next = NULL;
	batch->nr   = 0;
	batch->max  = MAX_GATHER_BATCH;

	tlb->active->next = batch;
	tlb->active = batch;

	return true;
}

static void tlb_batch_pages_flush(struct mmu_gather *tlb)
{
	struct mmu_gather_batch *batch;

	for (batch = &tlb->local; batch && batch->nr; batch = batch->next) {
		free_pages_and_swap_cache(batch->pages, batch->nr);
		batch->nr = 0;
	}
	tlb->active = &tlb->local;
}

static void tlb_batch_list_free(struct mmu_gather *tlb)
{
	struct mmu_gather_batch *batch, *next;

	for (batch = tlb->local.next; batch; batch = next) {
		next = batch->next;
		free_pages((unsigned long)batch, 0);
	}
	tlb->local.next = NULL;
}

bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_size)
{
	struct mmu_gather_batch *batch;

	VM_BUG_ON(!tlb->end);

#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
	VM_WARN_ON(tlb->page_size != page_size);
#endif

	batch = tlb->active;
	/*
	 * Add the page and check if we are full. If so
	 * force a flush.
	 */
	batch->pages[batch->nr++] = page;
	if (batch->nr == batch->max) {
		if (!tlb_next_batch(tlb))
			return true;
		batch = tlb->active;
	}
	VM_BUG_ON_PAGE(batch->nr > batch->max, page);

	return false;
}

#endif /* MMU_GATHER_NO_GATHER */

#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE

/*
 * See the comment near struct mmu_table_batch.
 */

/*
 * If we want tlb_remove_table() to imply TLB invalidates.
 */
static inline void tlb_table_invalidate(struct mmu_gather *tlb)
{
	if (tlb_needs_table_invalidate()) {
		/*
		 * Invalidate page-table caches used by hardware walkers. Then
		 * we still need to RCU-sched wait while freeing the pages
		 * because software walkers can still be in-flight.
		 */
		tlb_flush_mmu_tlbonly(tlb);
	}
}

static void tlb_remove_table_smp_sync(void *arg)
{
	/* Simply deliver the interrupt */
}

static void tlb_remove_table_one(void *table)
{
	/*
	 * This isn't an RCU grace period and hence the page-tables cannot be
	 * assumed to be actually RCU-freed.
	 *
	 * It is however sufficient for software page-table walkers that rely on
	 * IRQ disabling. See the comment near struct mmu_table_batch.
	 */
	smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
	__tlb_remove_table(table);
}

static void tlb_remove_table_rcu(struct rcu_head *head)
{
	struct mmu_table_batch *batch;
	int i;

	batch = container_of(head, struct mmu_table_batch, rcu);

	for (i = 0; i < batch->nr; i++)
		__tlb_remove_table(batch->tables[i]);

	free_page((unsigned long)batch);
}

static void tlb_table_flush(struct mmu_gather *tlb)
{
	struct mmu_table_batch **batch = &tlb->batch;

	if (*batch) {
		tlb_table_invalidate(tlb);
		call_rcu(&(*batch)->rcu, tlb_remove_table_rcu);
		*batch = NULL;
	}
}

void tlb_remove_table(struct mmu_gather *tlb, void *table)
{
	struct mmu_table_batch **batch = &tlb->batch;

	if (*batch == NULL) {
		*batch = (struct mmu_table_batch *)__get_free_page(GFP_NOWAIT | __GFP_NOWARN);
		if (*batch == NULL) {
			tlb_table_invalidate(tlb);
			tlb_remove_table_one(table);
			return;
		}
		(*batch)->nr = 0;
	}

	(*batch)->tables[(*batch)->nr++] = table;
	if ((*batch)->nr == MAX_TABLE_BATCH)
		tlb_table_flush(tlb);
}

#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */

static void tlb_flush_mmu_free(struct mmu_gather *tlb)
{
#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
	tlb_table_flush(tlb);
#endif
#ifndef CONFIG_MMU_GATHER_NO_GATHER
	tlb_batch_pages_flush(tlb);
#endif
}

void tlb_flush_mmu(struct mmu_gather *tlb)
{
	tlb_flush_mmu_tlbonly(tlb);
	tlb_flush_mmu_free(tlb);
}

/**
 * tlb_gather_mmu - initialize an mmu_gather structure for page-table tear-down
 * @tlb: the mmu_gather structure to initialize
 * @mm: the mm_struct of the target address space
 * @start: start of the region that will be removed from the page-table
 * @end: end of the region that will be removed from the page-table
 *
 * Called to initialize an (on-stack) mmu_gather structure for page-table
 * tear-down from @mm. The @start and @end are set to 0 and -1
 * respectively when @mm is without users and we're going to destroy
 * the full address space (exit/execve).
 */
void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
			unsigned long start, unsigned long end)
{
	tlb->mm = mm;

	/* Is it from 0 to ~0? */
	tlb->fullmm     = !(start | (end+1));

#ifndef CONFIG_MMU_GATHER_NO_GATHER
	tlb->need_flush_all = 0;
	tlb->local.next = NULL;
	tlb->local.nr   = 0;
	tlb->local.max  = ARRAY_SIZE(tlb->__pages);
	tlb->active     = &tlb->local;
	tlb->batch_count = 0;
#endif

#ifdef CONFIG_MMU_GATHER_RCU_TABLE_FREE
	tlb->batch = NULL;
#endif
#ifdef CONFIG_MMU_GATHER_PAGE_SIZE
	tlb->page_size = 0;
#endif

	__tlb_reset_range(tlb);
	inc_tlb_flush_pending(tlb->mm);
}

/**
 * tlb_finish_mmu - finish an mmu_gather structure
 * @tlb: the mmu_gather structure to finish
 * @start: start of the region that will be removed from the page-table
 * @end: end of the region that will be removed from the page-table
 *
 * Called at the end of the shootdown operation to free up any resources that
 * were required.
 */
void tlb_finish_mmu(struct mmu_gather *tlb,
		unsigned long start, unsigned long end)
{
	/*
	 * If there are parallel threads are doing PTE changes on same range
	 * under non-exclusive lock (e.g., mmap_sem read-side) but defer TLB
	 * flush by batching, one thread may end up seeing inconsistent PTEs
	 * and result in having stale TLB entries.  So flush TLB forcefully
	 * if we detect parallel PTE batching threads.
	 *
	 * However, some syscalls, e.g. munmap(), may free page tables, this
	 * needs force flush everything in the given range. Otherwise this
	 * may result in having stale TLB entries for some architectures,
	 * e.g. aarch64, that could specify flush what level TLB.
	 */
	if (mm_tlb_flush_nested(tlb->mm)) {
		/*
		 * The aarch64 yields better performance with fullmm by
		 * avoiding multiple CPUs spamming TLBI messages at the
		 * same time.
		 *
		 * On x86 non-fullmm doesn't yield significant difference
		 * against fullmm.
		 */
		tlb->fullmm = 1;
		__tlb_reset_range(tlb);
		tlb->freed_tables = 1;
	}

	tlb_flush_mmu(tlb);

#ifndef CONFIG_MMU_GATHER_NO_GATHER
	tlb_batch_list_free(tlb);
#endif
	dec_tlb_flush_pending(tlb->mm);
}