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1e133ab2 MS |
1 | /* |
2 | * Page table allocation functions | |
3 | * | |
4 | * Copyright IBM Corp. 2016 | |
5 | * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com> | |
6 | */ | |
7 | ||
8 | #include <linux/mm.h> | |
9 | #include <linux/sysctl.h> | |
10 | #include <asm/mmu_context.h> | |
11 | #include <asm/pgalloc.h> | |
12 | #include <asm/gmap.h> | |
13 | #include <asm/tlb.h> | |
14 | #include <asm/tlbflush.h> | |
15 | ||
16 | #ifdef CONFIG_PGSTE | |
17 | ||
18 | static int page_table_allocate_pgste_min = 0; | |
19 | static int page_table_allocate_pgste_max = 1; | |
20 | int page_table_allocate_pgste = 0; | |
21 | EXPORT_SYMBOL(page_table_allocate_pgste); | |
22 | ||
23 | static struct ctl_table page_table_sysctl[] = { | |
24 | { | |
25 | .procname = "allocate_pgste", | |
26 | .data = &page_table_allocate_pgste, | |
27 | .maxlen = sizeof(int), | |
28 | .mode = S_IRUGO | S_IWUSR, | |
29 | .proc_handler = proc_dointvec, | |
30 | .extra1 = &page_table_allocate_pgste_min, | |
31 | .extra2 = &page_table_allocate_pgste_max, | |
32 | }, | |
33 | { } | |
34 | }; | |
35 | ||
36 | static struct ctl_table page_table_sysctl_dir[] = { | |
37 | { | |
38 | .procname = "vm", | |
39 | .maxlen = 0, | |
40 | .mode = 0555, | |
41 | .child = page_table_sysctl, | |
42 | }, | |
43 | { } | |
44 | }; | |
45 | ||
46 | static int __init page_table_register_sysctl(void) | |
47 | { | |
48 | return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM; | |
49 | } | |
50 | __initcall(page_table_register_sysctl); | |
51 | ||
52 | #endif /* CONFIG_PGSTE */ | |
53 | ||
54 | unsigned long *crst_table_alloc(struct mm_struct *mm) | |
55 | { | |
56 | struct page *page = alloc_pages(GFP_KERNEL, 2); | |
57 | ||
58 | if (!page) | |
59 | return NULL; | |
60 | return (unsigned long *) page_to_phys(page); | |
61 | } | |
62 | ||
63 | void crst_table_free(struct mm_struct *mm, unsigned long *table) | |
64 | { | |
65 | free_pages((unsigned long) table, 2); | |
66 | } | |
67 | ||
68 | static void __crst_table_upgrade(void *arg) | |
69 | { | |
70 | struct mm_struct *mm = arg; | |
71 | ||
72 | if (current->active_mm == mm) { | |
73 | clear_user_asce(); | |
74 | set_user_asce(mm); | |
75 | } | |
76 | __tlb_flush_local(); | |
77 | } | |
78 | ||
79 | int crst_table_upgrade(struct mm_struct *mm, unsigned long limit) | |
80 | { | |
81 | unsigned long *table, *pgd; | |
82 | unsigned long entry; | |
83 | int flush; | |
84 | ||
85 | BUG_ON(limit > TASK_MAX_SIZE); | |
86 | flush = 0; | |
87 | repeat: | |
88 | table = crst_table_alloc(mm); | |
89 | if (!table) | |
90 | return -ENOMEM; | |
91 | spin_lock_bh(&mm->page_table_lock); | |
92 | if (mm->context.asce_limit < limit) { | |
93 | pgd = (unsigned long *) mm->pgd; | |
94 | if (mm->context.asce_limit <= (1UL << 31)) { | |
95 | entry = _REGION3_ENTRY_EMPTY; | |
96 | mm->context.asce_limit = 1UL << 42; | |
97 | mm->context.asce_bits = _ASCE_TABLE_LENGTH | | |
98 | _ASCE_USER_BITS | | |
99 | _ASCE_TYPE_REGION3; | |
100 | } else { | |
101 | entry = _REGION2_ENTRY_EMPTY; | |
102 | mm->context.asce_limit = 1UL << 53; | |
103 | mm->context.asce_bits = _ASCE_TABLE_LENGTH | | |
104 | _ASCE_USER_BITS | | |
105 | _ASCE_TYPE_REGION2; | |
106 | } | |
107 | crst_table_init(table, entry); | |
108 | pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd); | |
109 | mm->pgd = (pgd_t *) table; | |
110 | mm->task_size = mm->context.asce_limit; | |
111 | table = NULL; | |
112 | flush = 1; | |
113 | } | |
114 | spin_unlock_bh(&mm->page_table_lock); | |
115 | if (table) | |
116 | crst_table_free(mm, table); | |
117 | if (mm->context.asce_limit < limit) | |
118 | goto repeat; | |
119 | if (flush) | |
120 | on_each_cpu(__crst_table_upgrade, mm, 0); | |
121 | return 0; | |
122 | } | |
123 | ||
124 | void crst_table_downgrade(struct mm_struct *mm, unsigned long limit) | |
125 | { | |
126 | pgd_t *pgd; | |
127 | ||
128 | if (current->active_mm == mm) { | |
129 | clear_user_asce(); | |
130 | __tlb_flush_mm(mm); | |
131 | } | |
132 | while (mm->context.asce_limit > limit) { | |
133 | pgd = mm->pgd; | |
134 | switch (pgd_val(*pgd) & _REGION_ENTRY_TYPE_MASK) { | |
135 | case _REGION_ENTRY_TYPE_R2: | |
136 | mm->context.asce_limit = 1UL << 42; | |
137 | mm->context.asce_bits = _ASCE_TABLE_LENGTH | | |
138 | _ASCE_USER_BITS | | |
139 | _ASCE_TYPE_REGION3; | |
140 | break; | |
141 | case _REGION_ENTRY_TYPE_R3: | |
142 | mm->context.asce_limit = 1UL << 31; | |
143 | mm->context.asce_bits = _ASCE_TABLE_LENGTH | | |
144 | _ASCE_USER_BITS | | |
145 | _ASCE_TYPE_SEGMENT; | |
146 | break; | |
147 | default: | |
148 | BUG(); | |
149 | } | |
150 | mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN); | |
151 | mm->task_size = mm->context.asce_limit; | |
152 | crst_table_free(mm, (unsigned long *) pgd); | |
153 | } | |
154 | if (current->active_mm == mm) | |
155 | set_user_asce(mm); | |
156 | } | |
157 | ||
158 | static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits) | |
159 | { | |
160 | unsigned int old, new; | |
161 | ||
162 | do { | |
163 | old = atomic_read(v); | |
164 | new = old ^ bits; | |
165 | } while (atomic_cmpxchg(v, old, new) != old); | |
166 | return new; | |
167 | } | |
168 | ||
169 | /* | |
170 | * page table entry allocation/free routines. | |
171 | */ | |
172 | unsigned long *page_table_alloc(struct mm_struct *mm) | |
173 | { | |
174 | unsigned long *table; | |
175 | struct page *page; | |
176 | unsigned int mask, bit; | |
177 | ||
178 | /* Try to get a fragment of a 4K page as a 2K page table */ | |
179 | if (!mm_alloc_pgste(mm)) { | |
180 | table = NULL; | |
181 | spin_lock_bh(&mm->context.list_lock); | |
182 | if (!list_empty(&mm->context.pgtable_list)) { | |
183 | page = list_first_entry(&mm->context.pgtable_list, | |
184 | struct page, lru); | |
185 | mask = atomic_read(&page->_mapcount); | |
186 | mask = (mask | (mask >> 4)) & 3; | |
187 | if (mask != 3) { | |
188 | table = (unsigned long *) page_to_phys(page); | |
189 | bit = mask & 1; /* =1 -> second 2K */ | |
190 | if (bit) | |
191 | table += PTRS_PER_PTE; | |
192 | atomic_xor_bits(&page->_mapcount, 1U << bit); | |
193 | list_del(&page->lru); | |
194 | } | |
195 | } | |
196 | spin_unlock_bh(&mm->context.list_lock); | |
197 | if (table) | |
198 | return table; | |
199 | } | |
200 | /* Allocate a fresh page */ | |
201 | page = alloc_page(GFP_KERNEL|__GFP_REPEAT); | |
202 | if (!page) | |
203 | return NULL; | |
204 | if (!pgtable_page_ctor(page)) { | |
205 | __free_page(page); | |
206 | return NULL; | |
207 | } | |
208 | /* Initialize page table */ | |
209 | table = (unsigned long *) page_to_phys(page); | |
210 | if (mm_alloc_pgste(mm)) { | |
211 | /* Return 4K page table with PGSTEs */ | |
212 | atomic_set(&page->_mapcount, 3); | |
213 | clear_table(table, _PAGE_INVALID, PAGE_SIZE/2); | |
214 | clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2); | |
215 | } else { | |
216 | /* Return the first 2K fragment of the page */ | |
217 | atomic_set(&page->_mapcount, 1); | |
218 | clear_table(table, _PAGE_INVALID, PAGE_SIZE); | |
219 | spin_lock_bh(&mm->context.list_lock); | |
220 | list_add(&page->lru, &mm->context.pgtable_list); | |
221 | spin_unlock_bh(&mm->context.list_lock); | |
222 | } | |
223 | return table; | |
224 | } | |
225 | ||
226 | void page_table_free(struct mm_struct *mm, unsigned long *table) | |
227 | { | |
228 | struct page *page; | |
229 | unsigned int bit, mask; | |
230 | ||
231 | page = pfn_to_page(__pa(table) >> PAGE_SHIFT); | |
232 | if (!mm_alloc_pgste(mm)) { | |
233 | /* Free 2K page table fragment of a 4K page */ | |
234 | bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)); | |
235 | spin_lock_bh(&mm->context.list_lock); | |
236 | mask = atomic_xor_bits(&page->_mapcount, 1U << bit); | |
237 | if (mask & 3) | |
238 | list_add(&page->lru, &mm->context.pgtable_list); | |
239 | else | |
240 | list_del(&page->lru); | |
241 | spin_unlock_bh(&mm->context.list_lock); | |
242 | if (mask != 0) | |
243 | return; | |
244 | } | |
245 | ||
246 | pgtable_page_dtor(page); | |
247 | atomic_set(&page->_mapcount, -1); | |
248 | __free_page(page); | |
249 | } | |
250 | ||
251 | void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table, | |
252 | unsigned long vmaddr) | |
253 | { | |
254 | struct mm_struct *mm; | |
255 | struct page *page; | |
256 | unsigned int bit, mask; | |
257 | ||
258 | mm = tlb->mm; | |
259 | page = pfn_to_page(__pa(table) >> PAGE_SHIFT); | |
260 | if (mm_alloc_pgste(mm)) { | |
261 | gmap_unlink(mm, table, vmaddr); | |
262 | table = (unsigned long *) (__pa(table) | 3); | |
263 | tlb_remove_table(tlb, table); | |
264 | return; | |
265 | } | |
266 | bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)); | |
267 | spin_lock_bh(&mm->context.list_lock); | |
268 | mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit); | |
269 | if (mask & 3) | |
270 | list_add_tail(&page->lru, &mm->context.pgtable_list); | |
271 | else | |
272 | list_del(&page->lru); | |
273 | spin_unlock_bh(&mm->context.list_lock); | |
274 | table = (unsigned long *) (__pa(table) | (1U << bit)); | |
275 | tlb_remove_table(tlb, table); | |
276 | } | |
277 | ||
278 | static void __tlb_remove_table(void *_table) | |
279 | { | |
280 | unsigned int mask = (unsigned long) _table & 3; | |
281 | void *table = (void *)((unsigned long) _table ^ mask); | |
282 | struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT); | |
283 | ||
284 | switch (mask) { | |
285 | case 0: /* pmd or pud */ | |
286 | free_pages((unsigned long) table, 2); | |
287 | break; | |
288 | case 1: /* lower 2K of a 4K page table */ | |
289 | case 2: /* higher 2K of a 4K page table */ | |
290 | if (atomic_xor_bits(&page->_mapcount, mask << 4) != 0) | |
291 | break; | |
292 | /* fallthrough */ | |
293 | case 3: /* 4K page table with pgstes */ | |
294 | pgtable_page_dtor(page); | |
295 | atomic_set(&page->_mapcount, -1); | |
296 | __free_page(page); | |
297 | break; | |
298 | } | |
299 | } | |
300 | ||
301 | static void tlb_remove_table_smp_sync(void *arg) | |
302 | { | |
303 | /* Simply deliver the interrupt */ | |
304 | } | |
305 | ||
306 | static void tlb_remove_table_one(void *table) | |
307 | { | |
308 | /* | |
309 | * This isn't an RCU grace period and hence the page-tables cannot be | |
310 | * assumed to be actually RCU-freed. | |
311 | * | |
312 | * It is however sufficient for software page-table walkers that rely | |
313 | * on IRQ disabling. See the comment near struct mmu_table_batch. | |
314 | */ | |
315 | smp_call_function(tlb_remove_table_smp_sync, NULL, 1); | |
316 | __tlb_remove_table(table); | |
317 | } | |
318 | ||
319 | static void tlb_remove_table_rcu(struct rcu_head *head) | |
320 | { | |
321 | struct mmu_table_batch *batch; | |
322 | int i; | |
323 | ||
324 | batch = container_of(head, struct mmu_table_batch, rcu); | |
325 | ||
326 | for (i = 0; i < batch->nr; i++) | |
327 | __tlb_remove_table(batch->tables[i]); | |
328 | ||
329 | free_page((unsigned long)batch); | |
330 | } | |
331 | ||
332 | void tlb_table_flush(struct mmu_gather *tlb) | |
333 | { | |
334 | struct mmu_table_batch **batch = &tlb->batch; | |
335 | ||
336 | if (*batch) { | |
337 | call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu); | |
338 | *batch = NULL; | |
339 | } | |
340 | } | |
341 | ||
342 | void tlb_remove_table(struct mmu_gather *tlb, void *table) | |
343 | { | |
344 | struct mmu_table_batch **batch = &tlb->batch; | |
345 | ||
346 | tlb->mm->context.flush_mm = 1; | |
347 | if (*batch == NULL) { | |
348 | *batch = (struct mmu_table_batch *) | |
349 | __get_free_page(GFP_NOWAIT | __GFP_NOWARN); | |
350 | if (*batch == NULL) { | |
351 | __tlb_flush_mm_lazy(tlb->mm); | |
352 | tlb_remove_table_one(table); | |
353 | return; | |
354 | } | |
355 | (*batch)->nr = 0; | |
356 | } | |
357 | (*batch)->tables[(*batch)->nr++] = table; | |
358 | if ((*batch)->nr == MAX_TABLE_BATCH) | |
359 | tlb_flush_mmu(tlb); | |
360 | } |