trivial: fix typos/grammar errors in Kconfig texts
[linux-2.6.git] / drivers / xen / grant-table.c
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 #include <asm/xen/hypercall.h>
44
45 #include <asm/pgtable.h>
46 #include <asm/sync_bitops.h>
47
48
49 /* External tools reserve first few grant table entries. */
50 #define NR_RESERVED_ENTRIES 8
51 #define GNTTAB_LIST_END 0xffffffff
52 #define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry))
53
54 static grant_ref_t **gnttab_list;
55 static unsigned int nr_grant_frames;
56 static unsigned int boot_max_nr_grant_frames;
57 static int gnttab_free_count;
58 static grant_ref_t gnttab_free_head;
59 static DEFINE_SPINLOCK(gnttab_list_lock);
60
61 static struct grant_entry *shared;
62
63 static struct gnttab_free_callback *gnttab_free_callback_list;
64
65 static int gnttab_expand(unsigned int req_entries);
66
67 #define RPP (PAGE_SIZE / sizeof(grant_ref_t))
68
69 static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
70 {
71         return &gnttab_list[(entry) / RPP][(entry) % RPP];
72 }
73 /* This can be used as an l-value */
74 #define gnttab_entry(entry) (*__gnttab_entry(entry))
75
76 static int get_free_entries(unsigned count)
77 {
78         unsigned long flags;
79         int ref, rc;
80         grant_ref_t head;
81
82         spin_lock_irqsave(&gnttab_list_lock, flags);
83
84         if ((gnttab_free_count < count) &&
85             ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
86                 spin_unlock_irqrestore(&gnttab_list_lock, flags);
87                 return rc;
88         }
89
90         ref = head = gnttab_free_head;
91         gnttab_free_count -= count;
92         while (count-- > 1)
93                 head = gnttab_entry(head);
94         gnttab_free_head = gnttab_entry(head);
95         gnttab_entry(head) = GNTTAB_LIST_END;
96
97         spin_unlock_irqrestore(&gnttab_list_lock, flags);
98
99         return ref;
100 }
101
102 static void do_free_callbacks(void)
103 {
104         struct gnttab_free_callback *callback, *next;
105
106         callback = gnttab_free_callback_list;
107         gnttab_free_callback_list = NULL;
108
109         while (callback != NULL) {
110                 next = callback->next;
111                 if (gnttab_free_count >= callback->count) {
112                         callback->next = NULL;
113                         callback->fn(callback->arg);
114                 } else {
115                         callback->next = gnttab_free_callback_list;
116                         gnttab_free_callback_list = callback;
117                 }
118                 callback = next;
119         }
120 }
121
122 static inline void check_free_callbacks(void)
123 {
124         if (unlikely(gnttab_free_callback_list))
125                 do_free_callbacks();
126 }
127
128 static void put_free_entry(grant_ref_t ref)
129 {
130         unsigned long flags;
131         spin_lock_irqsave(&gnttab_list_lock, flags);
132         gnttab_entry(ref) = gnttab_free_head;
133         gnttab_free_head = ref;
134         gnttab_free_count++;
135         check_free_callbacks();
136         spin_unlock_irqrestore(&gnttab_list_lock, flags);
137 }
138
139 static void update_grant_entry(grant_ref_t ref, domid_t domid,
140                                unsigned long frame, unsigned flags)
141 {
142         /*
143          * Introducing a valid entry into the grant table:
144          *  1. Write ent->domid.
145          *  2. Write ent->frame:
146          *      GTF_permit_access:   Frame to which access is permitted.
147          *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
148          *                           frame, or zero if none.
149          *  3. Write memory barrier (WMB).
150          *  4. Write ent->flags, inc. valid type.
151          */
152         shared[ref].frame = frame;
153         shared[ref].domid = domid;
154         wmb();
155         shared[ref].flags = flags;
156 }
157
158 /*
159  * Public grant-issuing interface functions
160  */
161 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
162                                      unsigned long frame, int readonly)
163 {
164         update_grant_entry(ref, domid, frame,
165                            GTF_permit_access | (readonly ? GTF_readonly : 0));
166 }
167 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);
168
169 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
170                                 int readonly)
171 {
172         int ref;
173
174         ref = get_free_entries(1);
175         if (unlikely(ref < 0))
176                 return -ENOSPC;
177
178         gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);
179
180         return ref;
181 }
182 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
183
184 int gnttab_query_foreign_access(grant_ref_t ref)
185 {
186         u16 nflags;
187
188         nflags = shared[ref].flags;
189
190         return (nflags & (GTF_reading|GTF_writing));
191 }
192 EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
193
194 int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
195 {
196         u16 flags, nflags;
197
198         nflags = shared[ref].flags;
199         do {
200                 flags = nflags;
201                 if (flags & (GTF_reading|GTF_writing)) {
202                         printk(KERN_ALERT "WARNING: g.e. still in use!\n");
203                         return 0;
204                 }
205         } while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) != flags);
206
207         return 1;
208 }
209 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
210
211 void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
212                                unsigned long page)
213 {
214         if (gnttab_end_foreign_access_ref(ref, readonly)) {
215                 put_free_entry(ref);
216                 if (page != 0)
217                         free_page(page);
218         } else {
219                 /* XXX This needs to be fixed so that the ref and page are
220                    placed on a list to be freed up later. */
221                 printk(KERN_WARNING
222                        "WARNING: leaking g.e. and page still in use!\n");
223         }
224 }
225 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
226
227 int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)
228 {
229         int ref;
230
231         ref = get_free_entries(1);
232         if (unlikely(ref < 0))
233                 return -ENOSPC;
234         gnttab_grant_foreign_transfer_ref(ref, domid, pfn);
235
236         return ref;
237 }
238 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);
239
240 void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,
241                                        unsigned long pfn)
242 {
243         update_grant_entry(ref, domid, pfn, GTF_accept_transfer);
244 }
245 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);
246
247 unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
248 {
249         unsigned long frame;
250         u16           flags;
251
252         /*
253          * If a transfer is not even yet started, try to reclaim the grant
254          * reference and return failure (== 0).
255          */
256         while (!((flags = shared[ref].flags) & GTF_transfer_committed)) {
257                 if (sync_cmpxchg(&shared[ref].flags, flags, 0) == flags)
258                         return 0;
259                 cpu_relax();
260         }
261
262         /* If a transfer is in progress then wait until it is completed. */
263         while (!(flags & GTF_transfer_completed)) {
264                 flags = shared[ref].flags;
265                 cpu_relax();
266         }
267
268         rmb();  /* Read the frame number /after/ reading completion status. */
269         frame = shared[ref].frame;
270         BUG_ON(frame == 0);
271
272         return frame;
273 }
274 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);
275
276 unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)
277 {
278         unsigned long frame = gnttab_end_foreign_transfer_ref(ref);
279         put_free_entry(ref);
280         return frame;
281 }
282 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);
283
284 void gnttab_free_grant_reference(grant_ref_t ref)
285 {
286         put_free_entry(ref);
287 }
288 EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);
289
290 void gnttab_free_grant_references(grant_ref_t head)
291 {
292         grant_ref_t ref;
293         unsigned long flags;
294         int count = 1;
295         if (head == GNTTAB_LIST_END)
296                 return;
297         spin_lock_irqsave(&gnttab_list_lock, flags);
298         ref = head;
299         while (gnttab_entry(ref) != GNTTAB_LIST_END) {
300                 ref = gnttab_entry(ref);
301                 count++;
302         }
303         gnttab_entry(ref) = gnttab_free_head;
304         gnttab_free_head = head;
305         gnttab_free_count += count;
306         check_free_callbacks();
307         spin_unlock_irqrestore(&gnttab_list_lock, flags);
308 }
309 EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
310
311 int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
312 {
313         int h = get_free_entries(count);
314
315         if (h < 0)
316                 return -ENOSPC;
317
318         *head = h;
319
320         return 0;
321 }
322 EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);
323
324 int gnttab_empty_grant_references(const grant_ref_t *private_head)
325 {
326         return (*private_head == GNTTAB_LIST_END);
327 }
328 EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);
329
330 int gnttab_claim_grant_reference(grant_ref_t *private_head)
331 {
332         grant_ref_t g = *private_head;
333         if (unlikely(g == GNTTAB_LIST_END))
334                 return -ENOSPC;
335         *private_head = gnttab_entry(g);
336         return g;
337 }
338 EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);
339
340 void gnttab_release_grant_reference(grant_ref_t *private_head,
341                                     grant_ref_t release)
342 {
343         gnttab_entry(release) = *private_head;
344         *private_head = release;
345 }
346 EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);
347
348 void gnttab_request_free_callback(struct gnttab_free_callback *callback,
349                                   void (*fn)(void *), void *arg, u16 count)
350 {
351         unsigned long flags;
352         spin_lock_irqsave(&gnttab_list_lock, flags);
353         if (callback->next)
354                 goto out;
355         callback->fn = fn;
356         callback->arg = arg;
357         callback->count = count;
358         callback->next = gnttab_free_callback_list;
359         gnttab_free_callback_list = callback;
360         check_free_callbacks();
361 out:
362         spin_unlock_irqrestore(&gnttab_list_lock, flags);
363 }
364 EXPORT_SYMBOL_GPL(gnttab_request_free_callback);
365
366 void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
367 {
368         struct gnttab_free_callback **pcb;
369         unsigned long flags;
370
371         spin_lock_irqsave(&gnttab_list_lock, flags);
372         for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
373                 if (*pcb == callback) {
374                         *pcb = callback->next;
375                         break;
376                 }
377         }
378         spin_unlock_irqrestore(&gnttab_list_lock, flags);
379 }
380 EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
381
382 static int grow_gnttab_list(unsigned int more_frames)
383 {
384         unsigned int new_nr_grant_frames, extra_entries, i;
385         unsigned int nr_glist_frames, new_nr_glist_frames;
386
387         new_nr_grant_frames = nr_grant_frames + more_frames;
388         extra_entries       = more_frames * GREFS_PER_GRANT_FRAME;
389
390         nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
391         new_nr_glist_frames =
392                 (new_nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
393         for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
394                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
395                 if (!gnttab_list[i])
396                         goto grow_nomem;
397         }
398
399
400         for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames;
401              i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)
402                 gnttab_entry(i) = i + 1;
403
404         gnttab_entry(i) = gnttab_free_head;
405         gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames;
406         gnttab_free_count += extra_entries;
407
408         nr_grant_frames = new_nr_grant_frames;
409
410         check_free_callbacks();
411
412         return 0;
413
414 grow_nomem:
415         for ( ; i >= nr_glist_frames; i--)
416                 free_page((unsigned long) gnttab_list[i]);
417         return -ENOMEM;
418 }
419
420 static unsigned int __max_nr_grant_frames(void)
421 {
422         struct gnttab_query_size query;
423         int rc;
424
425         query.dom = DOMID_SELF;
426
427         rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
428         if ((rc < 0) || (query.status != GNTST_okay))
429                 return 4; /* Legacy max supported number of frames */
430
431         return query.max_nr_frames;
432 }
433
434 static inline unsigned int max_nr_grant_frames(void)
435 {
436         unsigned int xen_max = __max_nr_grant_frames();
437
438         if (xen_max > boot_max_nr_grant_frames)
439                 return boot_max_nr_grant_frames;
440         return xen_max;
441 }
442
443 static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
444 {
445         struct gnttab_setup_table setup;
446         unsigned long *frames;
447         unsigned int nr_gframes = end_idx + 1;
448         int rc;
449
450         frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC);
451         if (!frames)
452                 return -ENOMEM;
453
454         setup.dom        = DOMID_SELF;
455         setup.nr_frames  = nr_gframes;
456         set_xen_guest_handle(setup.frame_list, frames);
457
458         rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
459         if (rc == -ENOSYS) {
460                 kfree(frames);
461                 return -ENOSYS;
462         }
463
464         BUG_ON(rc || setup.status);
465
466         rc = arch_gnttab_map_shared(frames, nr_gframes, max_nr_grant_frames(),
467                                     &shared);
468         BUG_ON(rc);
469
470         kfree(frames);
471
472         return 0;
473 }
474
475 int gnttab_resume(void)
476 {
477         if (max_nr_grant_frames() < nr_grant_frames)
478                 return -ENOSYS;
479         return gnttab_map(0, nr_grant_frames - 1);
480 }
481
482 int gnttab_suspend(void)
483 {
484         arch_gnttab_unmap_shared(shared, nr_grant_frames);
485         return 0;
486 }
487
488 static int gnttab_expand(unsigned int req_entries)
489 {
490         int rc;
491         unsigned int cur, extra;
492
493         cur = nr_grant_frames;
494         extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) /
495                  GREFS_PER_GRANT_FRAME);
496         if (cur + extra > max_nr_grant_frames())
497                 return -ENOSPC;
498
499         rc = gnttab_map(cur, cur + extra - 1);
500         if (rc == 0)
501                 rc = grow_gnttab_list(extra);
502
503         return rc;
504 }
505
506 static int __devinit gnttab_init(void)
507 {
508         int i;
509         unsigned int max_nr_glist_frames, nr_glist_frames;
510         unsigned int nr_init_grefs;
511
512         if (!xen_domain())
513                 return -ENODEV;
514
515         nr_grant_frames = 1;
516         boot_max_nr_grant_frames = __max_nr_grant_frames();
517
518         /* Determine the maximum number of frames required for the
519          * grant reference free list on the current hypervisor.
520          */
521         max_nr_glist_frames = (boot_max_nr_grant_frames *
522                                GREFS_PER_GRANT_FRAME / RPP);
523
524         gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
525                               GFP_KERNEL);
526         if (gnttab_list == NULL)
527                 return -ENOMEM;
528
529         nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
530         for (i = 0; i < nr_glist_frames; i++) {
531                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
532                 if (gnttab_list[i] == NULL)
533                         goto ini_nomem;
534         }
535
536         if (gnttab_resume() < 0)
537                 return -ENODEV;
538
539         nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME;
540
541         for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
542                 gnttab_entry(i) = i + 1;
543
544         gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
545         gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
546         gnttab_free_head  = NR_RESERVED_ENTRIES;
547
548         printk("Grant table initialized\n");
549         return 0;
550
551  ini_nomem:
552         for (i--; i >= 0; i--)
553                 free_page((unsigned long)gnttab_list[i]);
554         kfree(gnttab_list);
555         return -ENOMEM;
556 }
557
558 core_initcall(gnttab_init);