Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[muen/linux.git] / drivers / virtio / virtio_balloon.c
1 /*
2  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
3  * Tosatti's implementations.
4  *
5  *  Copyright 2008 Rusty Russell IBM Corporation
6  *
7  *  This program is free software; you can redistribute it and/or modify
8  *  it under the terms of the GNU General Public License as published by
9  *  the Free Software Foundation; either version 2 of the License, or
10  *  (at your option) any later version.
11  *
12  *  This program is distributed in the hope that it will be useful,
13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  *  GNU General Public License for more details.
16  *
17  *  You should have received a copy of the GNU General Public License
18  *  along with this program; if not, write to the Free Software
19  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
20  */
21
22 #include <linux/virtio.h>
23 #include <linux/virtio_balloon.h>
24 #include <linux/swap.h>
25 #include <linux/workqueue.h>
26 #include <linux/delay.h>
27 #include <linux/slab.h>
28 #include <linux/module.h>
29 #include <linux/balloon_compaction.h>
30 #include <linux/wait.h>
31 #include <linux/mm.h>
32 #include <linux/mount.h>
33 #include <linux/magic.h>
34
35 /*
36  * Balloon device works in 4K page units.  So each page is pointed to by
37  * multiple balloon pages.  All memory counters in this driver are in balloon
38  * page units.
39  */
40 #define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
41 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
42 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
43
44 #define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
45                                              __GFP_NOMEMALLOC)
46 /* The order of free page blocks to report to host */
47 #define VIRTIO_BALLOON_FREE_PAGE_ORDER (MAX_ORDER - 1)
48 /* The size of a free page block in bytes */
49 #define VIRTIO_BALLOON_FREE_PAGE_SIZE \
50         (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT))
51
52 #ifdef CONFIG_BALLOON_COMPACTION
53 static struct vfsmount *balloon_mnt;
54 #endif
55
56 enum virtio_balloon_vq {
57         VIRTIO_BALLOON_VQ_INFLATE,
58         VIRTIO_BALLOON_VQ_DEFLATE,
59         VIRTIO_BALLOON_VQ_STATS,
60         VIRTIO_BALLOON_VQ_FREE_PAGE,
61         VIRTIO_BALLOON_VQ_MAX
62 };
63
64 struct virtio_balloon {
65         struct virtio_device *vdev;
66         struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
67
68         /* Balloon's own wq for cpu-intensive work items */
69         struct workqueue_struct *balloon_wq;
70         /* The free page reporting work item submitted to the balloon wq */
71         struct work_struct report_free_page_work;
72
73         /* The balloon servicing is delegated to a freezable workqueue. */
74         struct work_struct update_balloon_stats_work;
75         struct work_struct update_balloon_size_work;
76
77         /* Prevent updating balloon when it is being canceled. */
78         spinlock_t stop_update_lock;
79         bool stop_update;
80
81         /* The list of allocated free pages, waiting to be given back to mm */
82         struct list_head free_page_list;
83         spinlock_t free_page_list_lock;
84         /* The number of free page blocks on the above list */
85         unsigned long num_free_page_blocks;
86         /* The cmd id received from host */
87         u32 cmd_id_received;
88         /* The cmd id that is actively in use */
89         __virtio32 cmd_id_active;
90         /* Buffer to store the stop sign */
91         __virtio32 cmd_id_stop;
92
93         /* Waiting for host to ack the pages we released. */
94         wait_queue_head_t acked;
95
96         /* Number of balloon pages we've told the Host we're not using. */
97         unsigned int num_pages;
98         /*
99          * The pages we've told the Host we're not using are enqueued
100          * at vb_dev_info->pages list.
101          * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
102          * to num_pages above.
103          */
104         struct balloon_dev_info vb_dev_info;
105
106         /* Synchronize access/update to this struct virtio_balloon elements */
107         struct mutex balloon_lock;
108
109         /* The array of pfns we tell the Host about. */
110         unsigned int num_pfns;
111         __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
112
113         /* Memory statistics */
114         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
115
116         /* To register a shrinker to shrink memory upon memory pressure */
117         struct shrinker shrinker;
118 };
119
120 static struct virtio_device_id id_table[] = {
121         { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
122         { 0 },
123 };
124
125 static u32 page_to_balloon_pfn(struct page *page)
126 {
127         unsigned long pfn = page_to_pfn(page);
128
129         BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
130         /* Convert pfn from Linux page size to balloon page size. */
131         return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
132 }
133
134 static void balloon_ack(struct virtqueue *vq)
135 {
136         struct virtio_balloon *vb = vq->vdev->priv;
137
138         wake_up(&vb->acked);
139 }
140
141 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
142 {
143         struct scatterlist sg;
144         unsigned int len;
145
146         sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
147
148         /* We should always be able to add one buffer to an empty queue. */
149         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
150         virtqueue_kick(vq);
151
152         /* When host has read buffer, this completes via balloon_ack */
153         wait_event(vb->acked, virtqueue_get_buf(vq, &len));
154
155 }
156
157 static void set_page_pfns(struct virtio_balloon *vb,
158                           __virtio32 pfns[], struct page *page)
159 {
160         unsigned int i;
161
162         /*
163          * Set balloon pfns pointing at this page.
164          * Note that the first pfn points at start of the page.
165          */
166         for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
167                 pfns[i] = cpu_to_virtio32(vb->vdev,
168                                           page_to_balloon_pfn(page) + i);
169 }
170
171 static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
172 {
173         unsigned num_allocated_pages;
174         unsigned num_pfns;
175         struct page *page;
176         LIST_HEAD(pages);
177
178         /* We can only do one array worth at a time. */
179         num = min(num, ARRAY_SIZE(vb->pfns));
180
181         for (num_pfns = 0; num_pfns < num;
182              num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
183                 struct page *page = balloon_page_alloc();
184
185                 if (!page) {
186                         dev_info_ratelimited(&vb->vdev->dev,
187                                              "Out of puff! Can't get %u pages\n",
188                                              VIRTIO_BALLOON_PAGES_PER_PAGE);
189                         /* Sleep for at least 1/5 of a second before retry. */
190                         msleep(200);
191                         break;
192                 }
193
194                 balloon_page_push(&pages, page);
195         }
196
197         mutex_lock(&vb->balloon_lock);
198
199         vb->num_pfns = 0;
200
201         while ((page = balloon_page_pop(&pages))) {
202                 balloon_page_enqueue(&vb->vb_dev_info, page);
203
204                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
205                 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
206                 if (!virtio_has_feature(vb->vdev,
207                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
208                         adjust_managed_page_count(page, -1);
209                 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
210         }
211
212         num_allocated_pages = vb->num_pfns;
213         /* Did we get any? */
214         if (vb->num_pfns != 0)
215                 tell_host(vb, vb->inflate_vq);
216         mutex_unlock(&vb->balloon_lock);
217
218         return num_allocated_pages;
219 }
220
221 static void release_pages_balloon(struct virtio_balloon *vb,
222                                  struct list_head *pages)
223 {
224         struct page *page, *next;
225
226         list_for_each_entry_safe(page, next, pages, lru) {
227                 if (!virtio_has_feature(vb->vdev,
228                                         VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
229                         adjust_managed_page_count(page, 1);
230                 list_del(&page->lru);
231                 put_page(page); /* balloon reference */
232         }
233 }
234
235 static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
236 {
237         unsigned num_freed_pages;
238         struct page *page;
239         struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
240         LIST_HEAD(pages);
241
242         /* We can only do one array worth at a time. */
243         num = min(num, ARRAY_SIZE(vb->pfns));
244
245         mutex_lock(&vb->balloon_lock);
246         /* We can't release more pages than taken */
247         num = min(num, (size_t)vb->num_pages);
248         for (vb->num_pfns = 0; vb->num_pfns < num;
249              vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
250                 page = balloon_page_dequeue(vb_dev_info);
251                 if (!page)
252                         break;
253                 set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
254                 list_add(&page->lru, &pages);
255                 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
256         }
257
258         num_freed_pages = vb->num_pfns;
259         /*
260          * Note that if
261          * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
262          * is true, we *have* to do it in this order
263          */
264         if (vb->num_pfns != 0)
265                 tell_host(vb, vb->deflate_vq);
266         release_pages_balloon(vb, &pages);
267         mutex_unlock(&vb->balloon_lock);
268         return num_freed_pages;
269 }
270
271 static inline void update_stat(struct virtio_balloon *vb, int idx,
272                                u16 tag, u64 val)
273 {
274         BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
275         vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
276         vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
277 }
278
279 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
280
281 static unsigned int update_balloon_stats(struct virtio_balloon *vb)
282 {
283         unsigned long events[NR_VM_EVENT_ITEMS];
284         struct sysinfo i;
285         unsigned int idx = 0;
286         long available;
287         unsigned long caches;
288
289         all_vm_events(events);
290         si_meminfo(&i);
291
292         available = si_mem_available();
293         caches = global_node_page_state(NR_FILE_PAGES);
294
295 #ifdef CONFIG_VM_EVENT_COUNTERS
296         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
297                                 pages_to_bytes(events[PSWPIN]));
298         update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
299                                 pages_to_bytes(events[PSWPOUT]));
300         update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
301         update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
302 #ifdef CONFIG_HUGETLB_PAGE
303         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
304                     events[HTLB_BUDDY_PGALLOC]);
305         update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
306                     events[HTLB_BUDDY_PGALLOC_FAIL]);
307 #endif
308 #endif
309         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
310                                 pages_to_bytes(i.freeram));
311         update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
312                                 pages_to_bytes(i.totalram));
313         update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
314                                 pages_to_bytes(available));
315         update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
316                                 pages_to_bytes(caches));
317
318         return idx;
319 }
320
321 /*
322  * While most virtqueues communicate guest-initiated requests to the hypervisor,
323  * the stats queue operates in reverse.  The driver initializes the virtqueue
324  * with a single buffer.  From that point forward, all conversations consist of
325  * a hypervisor request (a call to this function) which directs us to refill
326  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
327  * we delegate the job to a freezable workqueue that will do the actual work via
328  * stats_handle_request().
329  */
330 static void stats_request(struct virtqueue *vq)
331 {
332         struct virtio_balloon *vb = vq->vdev->priv;
333
334         spin_lock(&vb->stop_update_lock);
335         if (!vb->stop_update)
336                 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
337         spin_unlock(&vb->stop_update_lock);
338 }
339
340 static void stats_handle_request(struct virtio_balloon *vb)
341 {
342         struct virtqueue *vq;
343         struct scatterlist sg;
344         unsigned int len, num_stats;
345
346         num_stats = update_balloon_stats(vb);
347
348         vq = vb->stats_vq;
349         if (!virtqueue_get_buf(vq, &len))
350                 return;
351         sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
352         virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
353         virtqueue_kick(vq);
354 }
355
356 static inline s64 towards_target(struct virtio_balloon *vb)
357 {
358         s64 target;
359         u32 num_pages;
360
361         virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
362                      &num_pages);
363
364         /* Legacy balloon config space is LE, unlike all other devices. */
365         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
366                 num_pages = le32_to_cpu((__force __le32)num_pages);
367
368         target = num_pages;
369         return target - vb->num_pages;
370 }
371
372 /* Gives back @num_to_return blocks of free pages to mm. */
373 static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
374                                              unsigned long num_to_return)
375 {
376         struct page *page;
377         unsigned long num_returned;
378
379         spin_lock_irq(&vb->free_page_list_lock);
380         for (num_returned = 0; num_returned < num_to_return; num_returned++) {
381                 page = balloon_page_pop(&vb->free_page_list);
382                 if (!page)
383                         break;
384                 free_pages((unsigned long)page_address(page),
385                            VIRTIO_BALLOON_FREE_PAGE_ORDER);
386         }
387         vb->num_free_page_blocks -= num_returned;
388         spin_unlock_irq(&vb->free_page_list_lock);
389
390         return num_returned;
391 }
392
393 static void virtballoon_changed(struct virtio_device *vdev)
394 {
395         struct virtio_balloon *vb = vdev->priv;
396         unsigned long flags;
397         s64 diff = towards_target(vb);
398
399         if (diff) {
400                 spin_lock_irqsave(&vb->stop_update_lock, flags);
401                 if (!vb->stop_update)
402                         queue_work(system_freezable_wq,
403                                    &vb->update_balloon_size_work);
404                 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
405         }
406
407         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
408                 virtio_cread(vdev, struct virtio_balloon_config,
409                              free_page_report_cmd_id, &vb->cmd_id_received);
410                 if (vb->cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
411                         /* Pass ULONG_MAX to give back all the free pages */
412                         return_free_pages_to_mm(vb, ULONG_MAX);
413                 } else if (vb->cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
414                            vb->cmd_id_received !=
415                            virtio32_to_cpu(vdev, vb->cmd_id_active)) {
416                         spin_lock_irqsave(&vb->stop_update_lock, flags);
417                         if (!vb->stop_update) {
418                                 queue_work(vb->balloon_wq,
419                                            &vb->report_free_page_work);
420                         }
421                         spin_unlock_irqrestore(&vb->stop_update_lock, flags);
422                 }
423         }
424 }
425
426 static void update_balloon_size(struct virtio_balloon *vb)
427 {
428         u32 actual = vb->num_pages;
429
430         /* Legacy balloon config space is LE, unlike all other devices. */
431         if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
432                 actual = (__force u32)cpu_to_le32(actual);
433
434         virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
435                       &actual);
436 }
437
438 static void update_balloon_stats_func(struct work_struct *work)
439 {
440         struct virtio_balloon *vb;
441
442         vb = container_of(work, struct virtio_balloon,
443                           update_balloon_stats_work);
444         stats_handle_request(vb);
445 }
446
447 static void update_balloon_size_func(struct work_struct *work)
448 {
449         struct virtio_balloon *vb;
450         s64 diff;
451
452         vb = container_of(work, struct virtio_balloon,
453                           update_balloon_size_work);
454         diff = towards_target(vb);
455
456         if (diff > 0)
457                 diff -= fill_balloon(vb, diff);
458         else if (diff < 0)
459                 diff += leak_balloon(vb, -diff);
460         update_balloon_size(vb);
461
462         if (diff)
463                 queue_work(system_freezable_wq, work);
464 }
465
466 static int init_vqs(struct virtio_balloon *vb)
467 {
468         struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
469         vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
470         const char *names[VIRTIO_BALLOON_VQ_MAX];
471         int err;
472
473         /*
474          * Inflateq and deflateq are used unconditionally. The names[]
475          * will be NULL if the related feature is not enabled, which will
476          * cause no allocation for the corresponding virtqueue in find_vqs.
477          */
478         callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
479         names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
480         callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
481         names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
482         names[VIRTIO_BALLOON_VQ_STATS] = NULL;
483         names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
484
485         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
486                 names[VIRTIO_BALLOON_VQ_STATS] = "stats";
487                 callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
488         }
489
490         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
491                 names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
492                 callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
493         }
494
495         err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
496                                          vqs, callbacks, names, NULL, NULL);
497         if (err)
498                 return err;
499
500         vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
501         vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
502         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
503                 struct scatterlist sg;
504                 unsigned int num_stats;
505                 vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
506
507                 /*
508                  * Prime this virtqueue with one buffer so the hypervisor can
509                  * use it to signal us later (it can't be broken yet!).
510                  */
511                 num_stats = update_balloon_stats(vb);
512
513                 sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
514                 err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
515                                            GFP_KERNEL);
516                 if (err) {
517                         dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
518                                  __func__);
519                         return err;
520                 }
521                 virtqueue_kick(vb->stats_vq);
522         }
523
524         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
525                 vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
526
527         return 0;
528 }
529
530 static int send_cmd_id_start(struct virtio_balloon *vb)
531 {
532         struct scatterlist sg;
533         struct virtqueue *vq = vb->free_page_vq;
534         int err, unused;
535
536         /* Detach all the used buffers from the vq */
537         while (virtqueue_get_buf(vq, &unused))
538                 ;
539
540         vb->cmd_id_active = cpu_to_virtio32(vb->vdev, vb->cmd_id_received);
541         sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
542         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
543         if (!err)
544                 virtqueue_kick(vq);
545         return err;
546 }
547
548 static int send_cmd_id_stop(struct virtio_balloon *vb)
549 {
550         struct scatterlist sg;
551         struct virtqueue *vq = vb->free_page_vq;
552         int err, unused;
553
554         /* Detach all the used buffers from the vq */
555         while (virtqueue_get_buf(vq, &unused))
556                 ;
557
558         sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
559         err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
560         if (!err)
561                 virtqueue_kick(vq);
562         return err;
563 }
564
565 static int get_free_page_and_send(struct virtio_balloon *vb)
566 {
567         struct virtqueue *vq = vb->free_page_vq;
568         struct page *page;
569         struct scatterlist sg;
570         int err, unused;
571         void *p;
572
573         /* Detach all the used buffers from the vq */
574         while (virtqueue_get_buf(vq, &unused))
575                 ;
576
577         page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
578                            VIRTIO_BALLOON_FREE_PAGE_ORDER);
579         /*
580          * When the allocation returns NULL, it indicates that we have got all
581          * the possible free pages, so return -EINTR to stop.
582          */
583         if (!page)
584                 return -EINTR;
585
586         p = page_address(page);
587         sg_init_one(&sg, p, VIRTIO_BALLOON_FREE_PAGE_SIZE);
588         /* There is always 1 entry reserved for the cmd id to use. */
589         if (vq->num_free > 1) {
590                 err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
591                 if (unlikely(err)) {
592                         free_pages((unsigned long)p,
593                                    VIRTIO_BALLOON_FREE_PAGE_ORDER);
594                         return err;
595                 }
596                 virtqueue_kick(vq);
597                 spin_lock_irq(&vb->free_page_list_lock);
598                 balloon_page_push(&vb->free_page_list, page);
599                 vb->num_free_page_blocks++;
600                 spin_unlock_irq(&vb->free_page_list_lock);
601         } else {
602                 /*
603                  * The vq has no available entry to add this page block, so
604                  * just free it.
605                  */
606                 free_pages((unsigned long)p, VIRTIO_BALLOON_FREE_PAGE_ORDER);
607         }
608
609         return 0;
610 }
611
612 static int send_free_pages(struct virtio_balloon *vb)
613 {
614         int err;
615         u32 cmd_id_active;
616
617         while (1) {
618                 /*
619                  * If a stop id or a new cmd id was just received from host,
620                  * stop the reporting.
621                  */
622                 cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
623                 if (cmd_id_active != vb->cmd_id_received)
624                         break;
625
626                 /*
627                  * The free page blocks are allocated and sent to host one by
628                  * one.
629                  */
630                 err = get_free_page_and_send(vb);
631                 if (err == -EINTR)
632                         break;
633                 else if (unlikely(err))
634                         return err;
635         }
636
637         return 0;
638 }
639
640 static void report_free_page_func(struct work_struct *work)
641 {
642         int err;
643         struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
644                                                  report_free_page_work);
645         struct device *dev = &vb->vdev->dev;
646
647         /* Start by sending the received cmd id to host with an outbuf. */
648         err = send_cmd_id_start(vb);
649         if (unlikely(err))
650                 dev_err(dev, "Failed to send a start id, err = %d\n", err);
651
652         err = send_free_pages(vb);
653         if (unlikely(err))
654                 dev_err(dev, "Failed to send a free page, err = %d\n", err);
655
656         /* End by sending a stop id to host with an outbuf. */
657         err = send_cmd_id_stop(vb);
658         if (unlikely(err))
659                 dev_err(dev, "Failed to send a stop id, err = %d\n", err);
660 }
661
662 #ifdef CONFIG_BALLOON_COMPACTION
663 /*
664  * virtballoon_migratepage - perform the balloon page migration on behalf of
665  *                           a compation thread.     (called under page lock)
666  * @vb_dev_info: the balloon device
667  * @newpage: page that will replace the isolated page after migration finishes.
668  * @page   : the isolated (old) page that is about to be migrated to newpage.
669  * @mode   : compaction mode -- not used for balloon page migration.
670  *
671  * After a ballooned page gets isolated by compaction procedures, this is the
672  * function that performs the page migration on behalf of a compaction thread
673  * The page migration for virtio balloon is done in a simple swap fashion which
674  * follows these two macro steps:
675  *  1) insert newpage into vb->pages list and update the host about it;
676  *  2) update the host about the old page removed from vb->pages list;
677  *
678  * This function preforms the balloon page migration task.
679  * Called through balloon_mapping->a_ops->migratepage
680  */
681 static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
682                 struct page *newpage, struct page *page, enum migrate_mode mode)
683 {
684         struct virtio_balloon *vb = container_of(vb_dev_info,
685                         struct virtio_balloon, vb_dev_info);
686         unsigned long flags;
687
688         /*
689          * In order to avoid lock contention while migrating pages concurrently
690          * to leak_balloon() or fill_balloon() we just give up the balloon_lock
691          * this turn, as it is easier to retry the page migration later.
692          * This also prevents fill_balloon() getting stuck into a mutex
693          * recursion in the case it ends up triggering memory compaction
694          * while it is attempting to inflate the ballon.
695          */
696         if (!mutex_trylock(&vb->balloon_lock))
697                 return -EAGAIN;
698
699         get_page(newpage); /* balloon reference */
700
701         /* balloon's page migration 1st step  -- inflate "newpage" */
702         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
703         balloon_page_insert(vb_dev_info, newpage);
704         vb_dev_info->isolated_pages--;
705         __count_vm_event(BALLOON_MIGRATE);
706         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
707         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
708         set_page_pfns(vb, vb->pfns, newpage);
709         tell_host(vb, vb->inflate_vq);
710
711         /* balloon's page migration 2nd step -- deflate "page" */
712         spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
713         balloon_page_delete(page);
714         spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
715         vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
716         set_page_pfns(vb, vb->pfns, page);
717         tell_host(vb, vb->deflate_vq);
718
719         mutex_unlock(&vb->balloon_lock);
720
721         put_page(page); /* balloon reference */
722
723         return MIGRATEPAGE_SUCCESS;
724 }
725
726 static struct dentry *balloon_mount(struct file_system_type *fs_type,
727                 int flags, const char *dev_name, void *data)
728 {
729         static const struct dentry_operations ops = {
730                 .d_dname = simple_dname,
731         };
732
733         return mount_pseudo(fs_type, "balloon-kvm:", NULL, &ops,
734                                 BALLOON_KVM_MAGIC);
735 }
736
737 static struct file_system_type balloon_fs = {
738         .name           = "balloon-kvm",
739         .mount          = balloon_mount,
740         .kill_sb        = kill_anon_super,
741 };
742
743 #endif /* CONFIG_BALLOON_COMPACTION */
744
745 static unsigned long shrink_free_pages(struct virtio_balloon *vb,
746                                        unsigned long pages_to_free)
747 {
748         unsigned long blocks_to_free, blocks_freed;
749
750         pages_to_free = round_up(pages_to_free,
751                                  1 << VIRTIO_BALLOON_FREE_PAGE_ORDER);
752         blocks_to_free = pages_to_free >> VIRTIO_BALLOON_FREE_PAGE_ORDER;
753         blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
754
755         return blocks_freed << VIRTIO_BALLOON_FREE_PAGE_ORDER;
756 }
757
758 static unsigned long shrink_balloon_pages(struct virtio_balloon *vb,
759                                           unsigned long pages_to_free)
760 {
761         unsigned long pages_freed = 0;
762
763         /*
764          * One invocation of leak_balloon can deflate at most
765          * VIRTIO_BALLOON_ARRAY_PFNS_MAX balloon pages, so we call it
766          * multiple times to deflate pages till reaching pages_to_free.
767          */
768         while (vb->num_pages && pages_to_free) {
769                 pages_freed += leak_balloon(vb, pages_to_free) /
770                                         VIRTIO_BALLOON_PAGES_PER_PAGE;
771                 pages_to_free -= pages_freed;
772         }
773         update_balloon_size(vb);
774
775         return pages_freed;
776 }
777
778 static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
779                                                   struct shrink_control *sc)
780 {
781         unsigned long pages_to_free, pages_freed = 0;
782         struct virtio_balloon *vb = container_of(shrinker,
783                                         struct virtio_balloon, shrinker);
784
785         pages_to_free = sc->nr_to_scan * VIRTIO_BALLOON_PAGES_PER_PAGE;
786
787         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
788                 pages_freed = shrink_free_pages(vb, pages_to_free);
789
790         if (pages_freed >= pages_to_free)
791                 return pages_freed;
792
793         pages_freed += shrink_balloon_pages(vb, pages_to_free - pages_freed);
794
795         return pages_freed;
796 }
797
798 static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
799                                                    struct shrink_control *sc)
800 {
801         struct virtio_balloon *vb = container_of(shrinker,
802                                         struct virtio_balloon, shrinker);
803         unsigned long count;
804
805         count = vb->num_pages / VIRTIO_BALLOON_PAGES_PER_PAGE;
806         count += vb->num_free_page_blocks >> VIRTIO_BALLOON_FREE_PAGE_ORDER;
807
808         return count;
809 }
810
811 static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
812 {
813         unregister_shrinker(&vb->shrinker);
814 }
815
816 static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
817 {
818         vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
819         vb->shrinker.count_objects = virtio_balloon_shrinker_count;
820         vb->shrinker.seeks = DEFAULT_SEEKS;
821
822         return register_shrinker(&vb->shrinker);
823 }
824
825 static int virtballoon_probe(struct virtio_device *vdev)
826 {
827         struct virtio_balloon *vb;
828         __u32 poison_val;
829         int err;
830
831         if (!vdev->config->get) {
832                 dev_err(&vdev->dev, "%s failure: config access disabled\n",
833                         __func__);
834                 return -EINVAL;
835         }
836
837         vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
838         if (!vb) {
839                 err = -ENOMEM;
840                 goto out;
841         }
842
843         INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
844         INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
845         spin_lock_init(&vb->stop_update_lock);
846         mutex_init(&vb->balloon_lock);
847         init_waitqueue_head(&vb->acked);
848         vb->vdev = vdev;
849
850         balloon_devinfo_init(&vb->vb_dev_info);
851
852         err = init_vqs(vb);
853         if (err)
854                 goto out_free_vb;
855
856 #ifdef CONFIG_BALLOON_COMPACTION
857         balloon_mnt = kern_mount(&balloon_fs);
858         if (IS_ERR(balloon_mnt)) {
859                 err = PTR_ERR(balloon_mnt);
860                 goto out_del_vqs;
861         }
862
863         vb->vb_dev_info.migratepage = virtballoon_migratepage;
864         vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
865         if (IS_ERR(vb->vb_dev_info.inode)) {
866                 err = PTR_ERR(vb->vb_dev_info.inode);
867                 kern_unmount(balloon_mnt);
868                 goto out_del_vqs;
869         }
870         vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
871 #endif
872         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
873                 /*
874                  * There is always one entry reserved for cmd id, so the ring
875                  * size needs to be at least two to report free page hints.
876                  */
877                 if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
878                         err = -ENOSPC;
879                         goto out_del_vqs;
880                 }
881                 vb->balloon_wq = alloc_workqueue("balloon-wq",
882                                         WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
883                 if (!vb->balloon_wq) {
884                         err = -ENOMEM;
885                         goto out_del_vqs;
886                 }
887                 INIT_WORK(&vb->report_free_page_work, report_free_page_func);
888                 vb->cmd_id_received = VIRTIO_BALLOON_CMD_ID_STOP;
889                 vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
890                                                   VIRTIO_BALLOON_CMD_ID_STOP);
891                 vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
892                                                   VIRTIO_BALLOON_CMD_ID_STOP);
893                 vb->num_free_page_blocks = 0;
894                 spin_lock_init(&vb->free_page_list_lock);
895                 INIT_LIST_HEAD(&vb->free_page_list);
896                 if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
897                         memset(&poison_val, PAGE_POISON, sizeof(poison_val));
898                         virtio_cwrite(vb->vdev, struct virtio_balloon_config,
899                                       poison_val, &poison_val);
900                 }
901         }
902         /*
903          * We continue to use VIRTIO_BALLOON_F_DEFLATE_ON_OOM to decide if a
904          * shrinker needs to be registered to relieve memory pressure.
905          */
906         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
907                 err = virtio_balloon_register_shrinker(vb);
908                 if (err)
909                         goto out_del_balloon_wq;
910         }
911         virtio_device_ready(vdev);
912
913         if (towards_target(vb))
914                 virtballoon_changed(vdev);
915         return 0;
916
917 out_del_balloon_wq:
918         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
919                 destroy_workqueue(vb->balloon_wq);
920 out_del_vqs:
921         vdev->config->del_vqs(vdev);
922 out_free_vb:
923         kfree(vb);
924 out:
925         return err;
926 }
927
928 static void remove_common(struct virtio_balloon *vb)
929 {
930         /* There might be pages left in the balloon: free them. */
931         while (vb->num_pages)
932                 leak_balloon(vb, vb->num_pages);
933         update_balloon_size(vb);
934
935         /* Now we reset the device so we can clean up the queues. */
936         vb->vdev->config->reset(vb->vdev);
937
938         vb->vdev->config->del_vqs(vb->vdev);
939 }
940
941 static void virtballoon_remove(struct virtio_device *vdev)
942 {
943         struct virtio_balloon *vb = vdev->priv;
944
945         if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
946                 virtio_balloon_unregister_shrinker(vb);
947         spin_lock_irq(&vb->stop_update_lock);
948         vb->stop_update = true;
949         spin_unlock_irq(&vb->stop_update_lock);
950         cancel_work_sync(&vb->update_balloon_size_work);
951         cancel_work_sync(&vb->update_balloon_stats_work);
952
953         if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
954                 cancel_work_sync(&vb->report_free_page_work);
955                 destroy_workqueue(vb->balloon_wq);
956         }
957
958         remove_common(vb);
959 #ifdef CONFIG_BALLOON_COMPACTION
960         if (vb->vb_dev_info.inode)
961                 iput(vb->vb_dev_info.inode);
962
963         kern_unmount(balloon_mnt);
964 #endif
965         kfree(vb);
966 }
967
968 #ifdef CONFIG_PM_SLEEP
969 static int virtballoon_freeze(struct virtio_device *vdev)
970 {
971         struct virtio_balloon *vb = vdev->priv;
972
973         /*
974          * The workqueue is already frozen by the PM core before this
975          * function is called.
976          */
977         remove_common(vb);
978         return 0;
979 }
980
981 static int virtballoon_restore(struct virtio_device *vdev)
982 {
983         struct virtio_balloon *vb = vdev->priv;
984         int ret;
985
986         ret = init_vqs(vdev->priv);
987         if (ret)
988                 return ret;
989
990         virtio_device_ready(vdev);
991
992         if (towards_target(vb))
993                 virtballoon_changed(vdev);
994         update_balloon_size(vb);
995         return 0;
996 }
997 #endif
998
999 static int virtballoon_validate(struct virtio_device *vdev)
1000 {
1001         if (!page_poisoning_enabled())
1002                 __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
1003
1004         __virtio_clear_bit(vdev, VIRTIO_F_IOMMU_PLATFORM);
1005         return 0;
1006 }
1007
1008 static unsigned int features[] = {
1009         VIRTIO_BALLOON_F_MUST_TELL_HOST,
1010         VIRTIO_BALLOON_F_STATS_VQ,
1011         VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
1012         VIRTIO_BALLOON_F_FREE_PAGE_HINT,
1013         VIRTIO_BALLOON_F_PAGE_POISON,
1014 };
1015
1016 static struct virtio_driver virtio_balloon_driver = {
1017         .feature_table = features,
1018         .feature_table_size = ARRAY_SIZE(features),
1019         .driver.name =  KBUILD_MODNAME,
1020         .driver.owner = THIS_MODULE,
1021         .id_table =     id_table,
1022         .validate =     virtballoon_validate,
1023         .probe =        virtballoon_probe,
1024         .remove =       virtballoon_remove,
1025         .config_changed = virtballoon_changed,
1026 #ifdef CONFIG_PM_SLEEP
1027         .freeze =       virtballoon_freeze,
1028         .restore =      virtballoon_restore,
1029 #endif
1030 };
1031
1032 module_virtio_driver(virtio_balloon_driver);
1033 MODULE_DEVICE_TABLE(virtio, id_table);
1034 MODULE_DESCRIPTION("Virtio balloon driver");
1035 MODULE_LICENSE("GPL");