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ad9a8612 JF |
1 | /****************************************************************************** |
2 | * grant_table.c | |
3 | * | |
4 | * Granting foreign access to our memory reservation. | |
5 | * | |
6 | * Copyright (c) 2005-2006, Christopher Clark | |
7 | * Copyright (c) 2004-2005, K A Fraser | |
8 | * | |
9 | * This program is free software; you can redistribute it and/or | |
10 | * modify it under the terms of the GNU General Public License version 2 | |
11 | * as published by the Free Software Foundation; or, when distributed | |
12 | * separately from the Linux kernel or incorporated into other | |
13 | * software packages, subject to the following license: | |
14 | * | |
15 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
16 | * of this source file (the "Software"), to deal in the Software without | |
17 | * restriction, including without limitation the rights to use, copy, modify, | |
18 | * merge, publish, distribute, sublicense, and/or sell copies of the Software, | |
19 | * and to permit persons to whom the Software is furnished to do so, subject to | |
20 | * the following conditions: | |
21 | * | |
22 | * The above copyright notice and this permission notice shall be included in | |
23 | * all copies or substantial portions of the Software. | |
24 | * | |
25 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
26 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
27 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
28 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
29 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING | |
30 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS | |
31 | * IN THE SOFTWARE. | |
32 | */ | |
33 | ||
34 | #include <linux/module.h> | |
35 | #include <linux/sched.h> | |
36 | #include <linux/mm.h> | |
37 | #include <linux/vmalloc.h> | |
38 | #include <linux/uaccess.h> | |
39 | ||
40 | #include <xen/interface/xen.h> | |
41 | #include <xen/page.h> | |
42 | #include <xen/grant_table.h> | |
43 | ||
44 | #include <asm/pgtable.h> | |
45 | #include <asm/sync_bitops.h> | |
46 | ||
47 | ||
48 | /* External tools reserve first few grant table entries. */ | |
49 | #define NR_RESERVED_ENTRIES 8 | |
50 | #define GNTTAB_LIST_END 0xffffffff | |
51 | #define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry)) | |
52 | ||
53 | static grant_ref_t **gnttab_list; | |
54 | static unsigned int nr_grant_frames; | |
55 | static unsigned int boot_max_nr_grant_frames; | |
56 | static int gnttab_free_count; | |
57 | static grant_ref_t gnttab_free_head; | |
58 | static DEFINE_SPINLOCK(gnttab_list_lock); | |
59 | ||
60 | static struct grant_entry *shared; | |
61 | ||
62 | static struct gnttab_free_callback *gnttab_free_callback_list; | |
63 | ||
64 | static int gnttab_expand(unsigned int req_entries); | |
65 | ||
66 | #define RPP (PAGE_SIZE / sizeof(grant_ref_t)) | |
67 | ||
68 | static inline grant_ref_t *__gnttab_entry(grant_ref_t entry) | |
69 | { | |
70 | return &gnttab_list[(entry) / RPP][(entry) % RPP]; | |
71 | } | |
72 | /* This can be used as an l-value */ | |
73 | #define gnttab_entry(entry) (*__gnttab_entry(entry)) | |
74 | ||
75 | static int get_free_entries(unsigned count) | |
76 | { | |
77 | unsigned long flags; | |
78 | int ref, rc; | |
79 | grant_ref_t head; | |
80 | ||
81 | spin_lock_irqsave(&gnttab_list_lock, flags); | |
82 | ||
83 | if ((gnttab_free_count < count) && | |
84 | ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) { | |
85 | spin_unlock_irqrestore(&gnttab_list_lock, flags); | |
86 | return rc; | |
87 | } | |
88 | ||
89 | ref = head = gnttab_free_head; | |
90 | gnttab_free_count -= count; | |
91 | while (count-- > 1) | |
92 | head = gnttab_entry(head); | |
93 | gnttab_free_head = gnttab_entry(head); | |
94 | gnttab_entry(head) = GNTTAB_LIST_END; | |
95 | ||
96 | spin_unlock_irqrestore(&gnttab_list_lock, flags); | |
97 | ||
98 | return ref; | |
99 | } | |
100 | ||
101 | static void do_free_callbacks(void) | |
102 | { | |
103 | struct gnttab_free_callback *callback, *next; | |
104 | ||
105 | callback = gnttab_free_callback_list; | |
106 | gnttab_free_callback_list = NULL; | |
107 | ||
108 | while (callback != NULL) { | |
109 | next = callback->next; | |
110 | if (gnttab_free_count >= callback->count) { | |
111 | callback->next = NULL; | |
112 | callback->fn(callback->arg); | |
113 | } else { | |
114 | callback->next = gnttab_free_callback_list; | |
115 | gnttab_free_callback_list = callback; | |
116 | } | |
117 | callback = next; | |
118 | } | |
119 | } | |
120 | ||
121 | static inline void check_free_callbacks(void) | |
122 | { | |
123 | if (unlikely(gnttab_free_callback_list)) | |
124 | do_free_callbacks(); | |
125 | } | |
126 | ||
127 | static void put_free_entry(grant_ref_t ref) | |
128 | { | |
129 | unsigned long flags; | |
130 | spin_lock_irqsave(&gnttab_list_lock, flags); | |
131 | gnttab_entry(ref) = gnttab_free_head; | |
132 | gnttab_free_head = ref; | |
133 | gnttab_free_count++; | |
134 | check_free_callbacks(); | |
135 | spin_unlock_irqrestore(&gnttab_list_lock, flags); | |
136 | } | |
137 | ||
138 | static void update_grant_entry(grant_ref_t ref, domid_t domid, | |
139 | unsigned long frame, unsigned flags) | |
140 | { | |
141 | /* | |
142 | * Introducing a valid entry into the grant table: | |
143 | * 1. Write ent->domid. | |
144 | * 2. Write ent->frame: | |
145 | * GTF_permit_access: Frame to which access is permitted. | |
146 | * GTF_accept_transfer: Pseudo-phys frame slot being filled by new | |
147 | * frame, or zero if none. | |
148 | * 3. Write memory barrier (WMB). | |
149 | * 4. Write ent->flags, inc. valid type. | |
150 | */ | |
151 | shared[ref].frame = frame; | |
152 | shared[ref].domid = domid; | |
153 | wmb(); | |
154 | shared[ref].flags = flags; | |
155 | } | |
156 | ||
157 | /* | |
158 | * Public grant-issuing interface functions | |
159 | */ | |
160 | void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid, | |
161 | unsigned long frame, int readonly) | |
162 | { | |
163 | update_grant_entry(ref, domid, frame, | |
164 | GTF_permit_access | (readonly ? GTF_readonly : 0)); | |
165 | } | |
166 | EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref); | |
167 | ||
168 | int gnttab_grant_foreign_access(domid_t domid, unsigned long frame, | |
169 | int readonly) | |
170 | { | |
171 | int ref; | |
172 | ||
173 | ref = get_free_entries(1); | |
174 | if (unlikely(ref < 0)) | |
175 | return -ENOSPC; | |
176 | ||
177 | gnttab_grant_foreign_access_ref(ref, domid, frame, readonly); | |
178 | ||
179 | return ref; | |
180 | } | |
181 | EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access); | |
182 | ||
183 | int gnttab_query_foreign_access(grant_ref_t ref) | |
184 | { | |
185 | u16 nflags; | |
186 | ||
187 | nflags = shared[ref].flags; | |
188 | ||
189 | return (nflags & (GTF_reading|GTF_writing)); | |
190 | } | |
191 | EXPORT_SYMBOL_GPL(gnttab_query_foreign_access); | |
192 | ||
193 | int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly) | |
194 | { | |
195 | u16 flags, nflags; | |
196 | ||
197 | nflags = shared[ref].flags; | |
198 | do { | |
199 | flags = nflags; | |
200 | if (flags & (GTF_reading|GTF_writing)) { | |
201 | printk(KERN_ALERT "WARNING: g.e. still in use!\n"); | |
202 | return 0; | |
203 | } | |
204 | } while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) != flags); | |
205 | ||
206 | return 1; | |
207 | } | |
208 | EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref); | |
209 | ||
210 | void gnttab_end_foreign_access(grant_ref_t ref, int readonly, | |
211 | unsigned long page) | |
212 | { | |
213 | if (gnttab_end_foreign_access_ref(ref, readonly)) { | |
214 | put_free_entry(ref); | |
215 | if (page != 0) | |
216 | free_page(page); | |
217 | } else { | |
218 | /* XXX This needs to be fixed so that the ref and page are | |
219 | placed on a list to be freed up later. */ | |
220 | printk(KERN_WARNING | |
221 | "WARNING: leaking g.e. and page still in use!\n"); | |
222 | } | |
223 | } | |
224 | EXPORT_SYMBOL_GPL(gnttab_end_foreign_access); | |
225 | ||
226 | int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn) | |
227 | { | |
228 | int ref; | |
229 | ||
230 | ref = get_free_entries(1); | |
231 | if (unlikely(ref < 0)) | |
232 | return -ENOSPC; | |
233 | gnttab_grant_foreign_transfer_ref(ref, domid, pfn); | |
234 | ||
235 | return ref; | |
236 | } | |
237 | EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer); | |
238 | ||
239 | void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid, | |
240 | unsigned long pfn) | |
241 | { | |
242 | update_grant_entry(ref, domid, pfn, GTF_accept_transfer); | |
243 | } | |
244 | EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref); | |
245 | ||
246 | unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref) | |
247 | { | |
248 | unsigned long frame; | |
249 | u16 flags; | |
250 | ||
251 | /* | |
252 | * If a transfer is not even yet started, try to reclaim the grant | |
253 | * reference and return failure (== 0). | |
254 | */ | |
255 | while (!((flags = shared[ref].flags) & GTF_transfer_committed)) { | |
256 | if (sync_cmpxchg(&shared[ref].flags, flags, 0) == flags) | |
257 | return 0; | |
258 | cpu_relax(); | |
259 | } | |
260 | ||
261 | /* If a transfer is in progress then wait until it is completed. */ | |
262 | while (!(flags & GTF_transfer_completed)) { | |
263 | flags = shared[ref].flags; | |
264 | cpu_relax(); | |
265 | } | |
266 | ||
267 | rmb(); /* Read the frame number /after/ reading completion status. */ | |
268 | frame = shared[ref].frame; | |
269 | BUG_ON(frame == 0); | |
270 | ||
271 | return frame; | |
272 | } | |
273 | EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref); | |
274 | ||
275 | unsigned long gnttab_end_foreign_transfer(grant_ref_t ref) | |
276 | { | |
277 | unsigned long frame = gnttab_end_foreign_transfer_ref(ref); | |
278 | put_free_entry(ref); | |
279 | return frame; | |
280 | } | |
281 | EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer); | |
282 | ||
283 | void gnttab_free_grant_reference(grant_ref_t ref) | |
284 | { | |
285 | put_free_entry(ref); | |
286 | } | |
287 | EXPORT_SYMBOL_GPL(gnttab_free_grant_reference); | |
288 | ||
289 | void gnttab_free_grant_references(grant_ref_t head) | |
290 | { | |
291 | grant_ref_t ref; | |
292 | unsigned long flags; | |
293 | int count = 1; | |
294 | if (head == GNTTAB_LIST_END) | |
295 | return; | |
296 | spin_lock_irqsave(&gnttab_list_lock, flags); | |
297 | ref = head; | |
298 | while (gnttab_entry(ref) != GNTTAB_LIST_END) { | |
299 | ref = gnttab_entry(ref); | |
300 | count++; | |
301 | } | |
302 | gnttab_entry(ref) = gnttab_free_head; | |
303 | gnttab_free_head = head; | |
304 | gnttab_free_count += count; | |
305 | check_free_callbacks(); | |
306 | spin_unlock_irqrestore(&gnttab_list_lock, flags); | |
307 | } | |
308 | EXPORT_SYMBOL_GPL(gnttab_free_grant_references); | |
309 | ||
310 | int gnttab_alloc_grant_references(u16 count, grant_ref_t *head) | |
311 | { | |
312 | int h = get_free_entries(count); | |
313 | ||
314 | if (h < 0) | |
315 | return -ENOSPC; | |
316 | ||
317 | *head = h; | |
318 | ||
319 | return 0; | |
320 | } | |
321 | EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references); | |
322 | ||
323 | int gnttab_empty_grant_references(const grant_ref_t *private_head) | |
324 | { | |
325 | return (*private_head == GNTTAB_LIST_END); | |
326 | } | |
327 | EXPORT_SYMBOL_GPL(gnttab_empty_grant_references); | |
328 | ||
329 | int gnttab_claim_grant_reference(grant_ref_t *private_head) | |
330 | { | |
331 | grant_ref_t g = *private_head; | |
332 | if (unlikely(g == GNTTAB_LIST_END)) | |
333 | return -ENOSPC; | |
334 | *private_head = gnttab_entry(g); | |
335 | return g; | |
336 | } | |
337 | EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference); | |
338 | ||
339 | void gnttab_release_grant_reference(grant_ref_t *private_head, | |
340 | grant_ref_t release) | |
341 | { | |
342 | gnttab_entry(release) = *private_head; | |
343 | *private_head = release; | |
344 | } | |
345 | EXPORT_SYMBOL_GPL(gnttab_release_grant_reference); | |
346 | ||
347 | void gnttab_request_free_callback(struct gnttab_free_callback *callback, | |
348 | void (*fn)(void *), void *arg, u16 count) | |
349 | { | |
350 | unsigned long flags; | |
351 | spin_lock_irqsave(&gnttab_list_lock, flags); | |
352 | if (callback->next) | |
353 | goto out; | |
354 | callback->fn = fn; | |
355 | callback->arg = arg; | |
356 | callback->count = count; | |
357 | callback->next = gnttab_free_callback_list; | |
358 | gnttab_free_callback_list = callback; | |
359 | check_free_callbacks(); | |
360 | out: | |
361 | spin_unlock_irqrestore(&gnttab_list_lock, flags); | |
362 | } | |
363 | EXPORT_SYMBOL_GPL(gnttab_request_free_callback); | |
364 | ||
365 | void gnttab_cancel_free_callback(struct gnttab_free_callback *callback) | |
366 | { | |
367 | struct gnttab_free_callback **pcb; | |
368 | unsigned long flags; | |
369 | ||
370 | spin_lock_irqsave(&gnttab_list_lock, flags); | |
371 | for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) { | |
372 | if (*pcb == callback) { | |
373 | *pcb = callback->next; | |
374 | break; | |
375 | } | |
376 | } | |
377 | spin_unlock_irqrestore(&gnttab_list_lock, flags); | |
378 | } | |
379 | EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback); | |
380 | ||
381 | static int grow_gnttab_list(unsigned int more_frames) | |
382 | { | |
383 | unsigned int new_nr_grant_frames, extra_entries, i; | |
bbc60c18 | 384 | unsigned int nr_glist_frames, new_nr_glist_frames; |
ad9a8612 JF |
385 | |
386 | new_nr_grant_frames = nr_grant_frames + more_frames; | |
387 | extra_entries = more_frames * GREFS_PER_GRANT_FRAME; | |
388 | ||
bbc60c18 MAEM |
389 | nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; |
390 | new_nr_glist_frames = | |
391 | (new_nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; | |
392 | for (i = nr_glist_frames; i < new_nr_glist_frames; i++) { | |
ad9a8612 JF |
393 | gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC); |
394 | if (!gnttab_list[i]) | |
395 | goto grow_nomem; | |
396 | } | |
397 | ||
398 | ||
399 | for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames; | |
400 | i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++) | |
401 | gnttab_entry(i) = i + 1; | |
402 | ||
403 | gnttab_entry(i) = gnttab_free_head; | |
404 | gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames; | |
405 | gnttab_free_count += extra_entries; | |
406 | ||
407 | nr_grant_frames = new_nr_grant_frames; | |
408 | ||
409 | check_free_callbacks(); | |
410 | ||
411 | return 0; | |
412 | ||
413 | grow_nomem: | |
bbc60c18 | 414 | for ( ; i >= nr_glist_frames; i--) |
ad9a8612 JF |
415 | free_page((unsigned long) gnttab_list[i]); |
416 | return -ENOMEM; | |
417 | } | |
418 | ||
419 | static unsigned int __max_nr_grant_frames(void) | |
420 | { | |
421 | struct gnttab_query_size query; | |
422 | int rc; | |
423 | ||
424 | query.dom = DOMID_SELF; | |
425 | ||
426 | rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1); | |
427 | if ((rc < 0) || (query.status != GNTST_okay)) | |
428 | return 4; /* Legacy max supported number of frames */ | |
429 | ||
430 | return query.max_nr_frames; | |
431 | } | |
432 | ||
433 | static inline unsigned int max_nr_grant_frames(void) | |
434 | { | |
435 | unsigned int xen_max = __max_nr_grant_frames(); | |
436 | ||
437 | if (xen_max > boot_max_nr_grant_frames) | |
438 | return boot_max_nr_grant_frames; | |
439 | return xen_max; | |
440 | } | |
441 | ||
ad9a8612 JF |
442 | static int gnttab_map(unsigned int start_idx, unsigned int end_idx) |
443 | { | |
444 | struct gnttab_setup_table setup; | |
445 | unsigned long *frames; | |
446 | unsigned int nr_gframes = end_idx + 1; | |
447 | int rc; | |
448 | ||
449 | frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC); | |
450 | if (!frames) | |
451 | return -ENOMEM; | |
452 | ||
453 | setup.dom = DOMID_SELF; | |
454 | setup.nr_frames = nr_gframes; | |
87e27cf6 | 455 | set_xen_guest_handle(setup.frame_list, frames); |
ad9a8612 JF |
456 | |
457 | rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1); | |
458 | if (rc == -ENOSYS) { | |
459 | kfree(frames); | |
460 | return -ENOSYS; | |
461 | } | |
462 | ||
463 | BUG_ON(rc || setup.status); | |
464 | ||
8d3d2106 IY |
465 | rc = arch_gnttab_map_shared(frames, nr_gframes, max_nr_grant_frames(), |
466 | &shared); | |
ad9a8612 | 467 | BUG_ON(rc); |
ad9a8612 JF |
468 | |
469 | kfree(frames); | |
470 | ||
471 | return 0; | |
472 | } | |
473 | ||
0e91398f | 474 | int gnttab_resume(void) |
ad9a8612 JF |
475 | { |
476 | if (max_nr_grant_frames() < nr_grant_frames) | |
477 | return -ENOSYS; | |
478 | return gnttab_map(0, nr_grant_frames - 1); | |
479 | } | |
480 | ||
0e91398f | 481 | int gnttab_suspend(void) |
ad9a8612 | 482 | { |
8d3d2106 | 483 | arch_gnttab_unmap_shared(shared, nr_grant_frames); |
ad9a8612 JF |
484 | return 0; |
485 | } | |
486 | ||
487 | static int gnttab_expand(unsigned int req_entries) | |
488 | { | |
489 | int rc; | |
490 | unsigned int cur, extra; | |
491 | ||
492 | cur = nr_grant_frames; | |
493 | extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) / | |
494 | GREFS_PER_GRANT_FRAME); | |
495 | if (cur + extra > max_nr_grant_frames()) | |
496 | return -ENOSPC; | |
497 | ||
498 | rc = gnttab_map(cur, cur + extra - 1); | |
499 | if (rc == 0) | |
500 | rc = grow_gnttab_list(extra); | |
501 | ||
502 | return rc; | |
503 | } | |
504 | ||
505 | static int __devinit gnttab_init(void) | |
506 | { | |
507 | int i; | |
bbc60c18 | 508 | unsigned int max_nr_glist_frames, nr_glist_frames; |
ad9a8612 JF |
509 | unsigned int nr_init_grefs; |
510 | ||
6e833587 | 511 | if (!xen_domain()) |
ad9a8612 JF |
512 | return -ENODEV; |
513 | ||
514 | nr_grant_frames = 1; | |
515 | boot_max_nr_grant_frames = __max_nr_grant_frames(); | |
516 | ||
517 | /* Determine the maximum number of frames required for the | |
518 | * grant reference free list on the current hypervisor. | |
519 | */ | |
520 | max_nr_glist_frames = (boot_max_nr_grant_frames * | |
bbc60c18 | 521 | GREFS_PER_GRANT_FRAME / RPP); |
ad9a8612 JF |
522 | |
523 | gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *), | |
524 | GFP_KERNEL); | |
525 | if (gnttab_list == NULL) | |
526 | return -ENOMEM; | |
527 | ||
bbc60c18 MAEM |
528 | nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP; |
529 | for (i = 0; i < nr_glist_frames; i++) { | |
ad9a8612 JF |
530 | gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL); |
531 | if (gnttab_list[i] == NULL) | |
532 | goto ini_nomem; | |
533 | } | |
534 | ||
535 | if (gnttab_resume() < 0) | |
536 | return -ENODEV; | |
537 | ||
538 | nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME; | |
539 | ||
540 | for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++) | |
541 | gnttab_entry(i) = i + 1; | |
542 | ||
543 | gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END; | |
544 | gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES; | |
545 | gnttab_free_head = NR_RESERVED_ENTRIES; | |
546 | ||
547 | printk("Grant table initialized\n"); | |
548 | return 0; | |
549 | ||
550 | ini_nomem: | |
551 | for (i--; i >= 0; i--) | |
552 | free_page((unsigned long)gnttab_list[i]); | |
553 | kfree(gnttab_list); | |
554 | return -ENOMEM; | |
555 | } | |
556 | ||
557 | core_initcall(gnttab_init); |