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