source: src/linux/universal/linux-3.18/drivers/virtio/virtio_balloon.c @ 31885

Last change on this file since 31885 was 31885, checked in by brainslayer, 3 months ago

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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/kthread.h>
26#include <linux/freezer.h>
27#include <linux/delay.h>
28#include <linux/slab.h>
29#include <linux/module.h>
30#include <linux/balloon_compaction.h>
31#include <linux/wait.h>
32
33/*
34 * Balloon device works in 4K page units.  So each page is pointed to by
35 * multiple balloon pages.  All memory counters in this driver are in balloon
36 * page units.
37 */
38#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
39#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
40
41struct virtio_balloon
42{
43        struct virtio_device *vdev;
44        struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
45
46        /* Where the ballooning thread waits for config to change. */
47        wait_queue_head_t config_change;
48
49        /* The thread servicing the balloon. */
50        struct task_struct *thread;
51
52        /* Waiting for host to ack the pages we released. */
53        wait_queue_head_t acked;
54
55        /* Number of balloon pages we've told the Host we're not using. */
56        unsigned int num_pages;
57        /*
58         * The pages we've told the Host we're not using are enqueued
59         * at vb_dev_info->pages list.
60         * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
61         * to num_pages above.
62         */
63        struct balloon_dev_info vb_dev_info;
64
65        /* Synchronize access/update to this struct virtio_balloon elements */
66        struct mutex balloon_lock;
67
68        /* The array of pfns we tell the Host about. */
69        unsigned int num_pfns;
70        u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
71
72        /* Memory statistics */
73        int need_stats_update;
74        struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
75};
76
77static struct virtio_device_id id_table[] = {
78        { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
79        { 0 },
80};
81
82static u32 page_to_balloon_pfn(struct page *page)
83{
84        unsigned long pfn = page_to_pfn(page);
85
86        BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
87        /* Convert pfn from Linux page size to balloon page size. */
88        return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
89}
90
91static struct page *balloon_pfn_to_page(u32 pfn)
92{
93        BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
94        return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
95}
96
97static void balloon_ack(struct virtqueue *vq)
98{
99        struct virtio_balloon *vb = vq->vdev->priv;
100
101        wake_up(&vb->acked);
102}
103
104static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
105{
106        struct scatterlist sg;
107        unsigned int len;
108
109        sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
110
111        /* We should always be able to add one buffer to an empty queue. */
112        virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
113        virtqueue_kick(vq);
114
115        /* When host has read buffer, this completes via balloon_ack */
116        wait_event(vb->acked, virtqueue_get_buf(vq, &len));
117}
118
119static void set_page_pfns(u32 pfns[], struct page *page)
120{
121        unsigned int i;
122
123        /* Set balloon pfns pointing at this page.
124         * Note that the first pfn points at start of the page. */
125        for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
126                pfns[i] = page_to_balloon_pfn(page) + i;
127}
128
129static void fill_balloon(struct virtio_balloon *vb, size_t num)
130{
131        struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
132
133        /* We can only do one array worth at a time. */
134        num = min(num, ARRAY_SIZE(vb->pfns));
135
136        mutex_lock(&vb->balloon_lock);
137        for (vb->num_pfns = 0; vb->num_pfns < num;
138             vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
139                struct page *page = balloon_page_enqueue(vb_dev_info);
140
141                if (!page) {
142                        dev_info_ratelimited(&vb->vdev->dev,
143                                             "Out of puff! Can't get %u pages\n",
144                                             VIRTIO_BALLOON_PAGES_PER_PAGE);
145                        /* Sleep for at least 1/5 of a second before retry. */
146                        msleep(200);
147                        break;
148                }
149                set_page_pfns(vb->pfns + vb->num_pfns, page);
150                vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
151                adjust_managed_page_count(page, -1);
152        }
153
154        /* Did we get any? */
155        if (vb->num_pfns != 0)
156                tell_host(vb, vb->inflate_vq);
157        mutex_unlock(&vb->balloon_lock);
158}
159
160static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
161{
162        unsigned int i;
163
164        /* Find pfns pointing at start of each page, get pages and free them. */
165        for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
166                struct page *page = balloon_pfn_to_page(pfns[i]);
167                adjust_managed_page_count(page, 1);
168                put_page(page); /* balloon reference */
169        }
170}
171
172static void leak_balloon(struct virtio_balloon *vb, size_t num)
173{
174        struct page *page;
175        struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
176
177        /* We can only do one array worth at a time. */
178        num = min(num, ARRAY_SIZE(vb->pfns));
179
180        mutex_lock(&vb->balloon_lock);
181        /* We can't release more pages than taken */
182        num = min(num, (size_t)vb->num_pages);
183        for (vb->num_pfns = 0; vb->num_pfns < num;
184             vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
185                page = balloon_page_dequeue(vb_dev_info);
186                if (!page)
187                        break;
188                set_page_pfns(vb->pfns + vb->num_pfns, page);
189                vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
190        }
191
192        /*
193         * Note that if
194         * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
195         * is true, we *have* to do it in this order
196         */
197        if (vb->num_pfns != 0)
198                tell_host(vb, vb->deflate_vq);
199        mutex_unlock(&vb->balloon_lock);
200        release_pages_by_pfn(vb->pfns, vb->num_pfns);
201}
202
203static inline void update_stat(struct virtio_balloon *vb, int idx,
204                               u16 tag, u64 val)
205{
206        BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
207        vb->stats[idx].tag = tag;
208        vb->stats[idx].val = val;
209}
210
211#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
212
213static void update_balloon_stats(struct virtio_balloon *vb)
214{
215        unsigned long events[NR_VM_EVENT_ITEMS];
216        struct sysinfo i;
217        int idx = 0;
218
219        all_vm_events(events);
220        si_meminfo(&i);
221
222        update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
223                                pages_to_bytes(events[PSWPIN]));
224        update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
225                                pages_to_bytes(events[PSWPOUT]));
226        update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
227        update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
228        update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
229                                pages_to_bytes(i.freeram));
230        update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
231                                pages_to_bytes(i.totalram));
232}
233
234/*
235 * While most virtqueues communicate guest-initiated requests to the hypervisor,
236 * the stats queue operates in reverse.  The driver initializes the virtqueue
237 * with a single buffer.  From that point forward, all conversations consist of
238 * a hypervisor request (a call to this function) which directs us to refill
239 * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
240 * we notify our kthread which does the actual work via stats_handle_request().
241 */
242static void stats_request(struct virtqueue *vq)
243{
244        struct virtio_balloon *vb = vq->vdev->priv;
245
246        vb->need_stats_update = 1;
247        wake_up(&vb->config_change);
248}
249
250static void stats_handle_request(struct virtio_balloon *vb)
251{
252        struct virtqueue *vq;
253        struct scatterlist sg;
254        unsigned int len;
255
256        vb->need_stats_update = 0;
257        update_balloon_stats(vb);
258
259        vq = vb->stats_vq;
260        if (!virtqueue_get_buf(vq, &len))
261                return;
262        sg_init_one(&sg, vb->stats, sizeof(vb->stats));
263        virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
264        virtqueue_kick(vq);
265}
266
267static void virtballoon_changed(struct virtio_device *vdev)
268{
269        struct virtio_balloon *vb = vdev->priv;
270
271        wake_up(&vb->config_change);
272}
273
274static inline s64 towards_target(struct virtio_balloon *vb)
275{
276        __le32 v;
277        s64 target;
278
279        virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &v);
280
281        target = le32_to_cpu(v);
282        return target - vb->num_pages;
283}
284
285static void update_balloon_size(struct virtio_balloon *vb)
286{
287        __le32 actual = cpu_to_le32(vb->num_pages);
288
289        virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
290                      &actual);
291}
292
293static int balloon(void *_vballoon)
294{
295        struct virtio_balloon *vb = _vballoon;
296        DEFINE_WAIT_FUNC(wait, woken_wake_function);
297
298        set_freezable();
299        while (!kthread_should_stop()) {
300                s64 diff;
301
302                try_to_freeze();
303
304                add_wait_queue(&vb->config_change, &wait);
305                for (;;) {
306                        if ((diff = towards_target(vb)) != 0 ||
307                            vb->need_stats_update ||
308                            kthread_should_stop() ||
309                            freezing(current))
310                                break;
311                        wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
312                }
313                remove_wait_queue(&vb->config_change, &wait);
314
315                if (vb->need_stats_update)
316                        stats_handle_request(vb);
317                if (diff > 0)
318                        fill_balloon(vb, diff);
319                else if (diff < 0)
320                        leak_balloon(vb, -diff);
321                update_balloon_size(vb);
322
323                /*
324                 * For large balloon changes, we could spend a lot of time
325                 * and always have work to do.  Be nice if preempt disabled.
326                 */
327                cond_resched();
328        }
329        return 0;
330}
331
332static int init_vqs(struct virtio_balloon *vb)
333{
334        struct virtqueue *vqs[3];
335        vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
336        const char *names[] = { "inflate", "deflate", "stats" };
337        int err, nvqs;
338
339        /*
340         * We expect two virtqueues: inflate and deflate, and
341         * optionally stat.
342         */
343        nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
344        err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
345        if (err)
346                return err;
347
348        vb->inflate_vq = vqs[0];
349        vb->deflate_vq = vqs[1];
350        if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
351                struct scatterlist sg;
352                vb->stats_vq = vqs[2];
353
354                /*
355                 * Prime this virtqueue with one buffer so the hypervisor can
356                 * use it to signal us later (it can't be broken yet!).
357                 */
358                update_balloon_stats(vb);
359
360                sg_init_one(&sg, vb->stats, sizeof vb->stats);
361                if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
362                    < 0)
363                        BUG();
364                virtqueue_kick(vb->stats_vq);
365        }
366        return 0;
367}
368
369#ifdef CONFIG_BALLOON_COMPACTION
370/*
371 * virtballoon_migratepage - perform the balloon page migration on behalf of
372 *                           a compation thread.     (called under page lock)
373 * @vb_dev_info: the balloon device
374 * @newpage: page that will replace the isolated page after migration finishes.
375 * @page   : the isolated (old) page that is about to be migrated to newpage.
376 * @mode   : compaction mode -- not used for balloon page migration.
377 *
378 * After a ballooned page gets isolated by compaction procedures, this is the
379 * function that performs the page migration on behalf of a compaction thread
380 * The page migration for virtio balloon is done in a simple swap fashion which
381 * follows these two macro steps:
382 *  1) insert newpage into vb->pages list and update the host about it;
383 *  2) update the host about the old page removed from vb->pages list;
384 *
385 * This function preforms the balloon page migration task.
386 * Called through balloon_mapping->a_ops->migratepage
387 */
388static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
389                struct page *newpage, struct page *page, enum migrate_mode mode)
390{
391        struct virtio_balloon *vb = container_of(vb_dev_info,
392                        struct virtio_balloon, vb_dev_info);
393        unsigned long flags;
394
395        /*
396         * In order to avoid lock contention while migrating pages concurrently
397         * to leak_balloon() or fill_balloon() we just give up the balloon_lock
398         * this turn, as it is easier to retry the page migration later.
399         * This also prevents fill_balloon() getting stuck into a mutex
400         * recursion in the case it ends up triggering memory compaction
401         * while it is attempting to inflate the ballon.
402         */
403        if (!mutex_trylock(&vb->balloon_lock))
404                return -EAGAIN;
405
406        get_page(newpage); /* balloon reference */
407
408        /* balloon's page migration 1st step  -- inflate "newpage" */
409        spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
410        balloon_page_insert(vb_dev_info, newpage);
411        vb_dev_info->isolated_pages--;
412        __count_vm_event(BALLOON_MIGRATE);
413        spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
414        vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
415        set_page_pfns(vb->pfns, newpage);
416        tell_host(vb, vb->inflate_vq);
417
418        /* balloon's page migration 2nd step -- deflate "page" */
419        balloon_page_delete(page);
420        vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
421        set_page_pfns(vb->pfns, page);
422        tell_host(vb, vb->deflate_vq);
423
424        mutex_unlock(&vb->balloon_lock);
425
426        put_page(page); /* balloon reference */
427
428        return MIGRATEPAGE_SUCCESS;
429}
430#endif /* CONFIG_BALLOON_COMPACTION */
431
432static int virtballoon_probe(struct virtio_device *vdev)
433{
434        struct virtio_balloon *vb;
435        int err;
436
437        vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
438        if (!vb) {
439                err = -ENOMEM;
440                goto out;
441        }
442
443        vb->num_pages = 0;
444        mutex_init(&vb->balloon_lock);
445        init_waitqueue_head(&vb->config_change);
446        init_waitqueue_head(&vb->acked);
447        vb->vdev = vdev;
448        vb->need_stats_update = 0;
449
450        balloon_devinfo_init(&vb->vb_dev_info);
451#ifdef CONFIG_BALLOON_COMPACTION
452        vb->vb_dev_info.migratepage = virtballoon_migratepage;
453#endif
454
455        err = init_vqs(vb);
456        if (err)
457                goto out_free_vb;
458
459        virtio_device_ready(vdev);
460
461        vb->thread = kthread_run(balloon, vb, "vballoon");
462        if (IS_ERR(vb->thread)) {
463                err = PTR_ERR(vb->thread);
464                goto out_del_vqs;
465        }
466
467        return 0;
468
469out_del_vqs:
470        vdev->config->del_vqs(vdev);
471out_free_vb:
472        kfree(vb);
473out:
474        return err;
475}
476
477static void remove_common(struct virtio_balloon *vb)
478{
479        /* There might be pages left in the balloon: free them. */
480        while (vb->num_pages)
481                leak_balloon(vb, vb->num_pages);
482        update_balloon_size(vb);
483
484        /* Now we reset the device so we can clean up the queues. */
485        vb->vdev->config->reset(vb->vdev);
486
487        vb->vdev->config->del_vqs(vb->vdev);
488}
489
490static void virtballoon_remove(struct virtio_device *vdev)
491{
492        struct virtio_balloon *vb = vdev->priv;
493
494        kthread_stop(vb->thread);
495        remove_common(vb);
496        kfree(vb);
497}
498
499#ifdef CONFIG_PM_SLEEP
500static int virtballoon_freeze(struct virtio_device *vdev)
501{
502        struct virtio_balloon *vb = vdev->priv;
503
504        /*
505         * The kthread is already frozen by the PM core before this
506         * function is called.
507         */
508
509        remove_common(vb);
510        return 0;
511}
512
513static int virtballoon_restore(struct virtio_device *vdev)
514{
515        struct virtio_balloon *vb = vdev->priv;
516        int ret;
517
518        ret = init_vqs(vdev->priv);
519        if (ret)
520                return ret;
521
522        virtio_device_ready(vdev);
523
524        fill_balloon(vb, towards_target(vb));
525        update_balloon_size(vb);
526        return 0;
527}
528#endif
529
530static unsigned int features[] = {
531        VIRTIO_BALLOON_F_MUST_TELL_HOST,
532        VIRTIO_BALLOON_F_STATS_VQ,
533};
534
535static struct virtio_driver virtio_balloon_driver = {
536        .feature_table = features,
537        .feature_table_size = ARRAY_SIZE(features),
538        .driver.name =  KBUILD_MODNAME,
539        .driver.owner = THIS_MODULE,
540        .id_table =     id_table,
541        .probe =        virtballoon_probe,
542        .remove =       virtballoon_remove,
543        .config_changed = virtballoon_changed,
544#ifdef CONFIG_PM_SLEEP
545        .freeze =       virtballoon_freeze,
546        .restore =      virtballoon_restore,
547#endif
548};
549
550module_virtio_driver(virtio_balloon_driver);
551MODULE_DEVICE_TABLE(virtio, id_table);
552MODULE_DESCRIPTION("Virtio balloon driver");
553MODULE_LICENSE("GPL");
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