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1/* Virtio balloon implementation, inspired by Dor Loar and Marcelo
2 * Tosatti's implementations.
3 *
4 * Copyright 2008 Rusty Russell IBM Corporation
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20//#define DEBUG
21#include <linux/virtio.h>
22#include <linux/virtio_balloon.h>
23#include <linux/swap.h>
24#include <linux/kthread.h>
25#include <linux/freezer.h>
26#include <linux/delay.h>
27#include <linux/slab.h>
28
29struct virtio_balloon
30{
31 struct virtio_device *vdev;
32 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
33
34 /* Where the ballooning thread waits for config to change. */
35 wait_queue_head_t config_change;
36
37 /* The thread servicing the balloon. */
38 struct task_struct *thread;
39
40 /* Waiting for host to ack the pages we released. */
41 struct completion acked;
42
43 /* The pages we've told the Host we're not using. */
44 unsigned int num_pages;
45 struct list_head pages;
46
47 /* The array of pfns we tell the Host about. */
48 unsigned int num_pfns;
49 u32 pfns[256];
50
51 /* Memory statistics */
52 int need_stats_update;
53 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
54};
55
56static struct virtio_device_id id_table[] = {
57 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
58 { 0 },
59};
60
61static u32 page_to_balloon_pfn(struct page *page)
62{
63 unsigned long pfn = page_to_pfn(page);
64
65 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
66 /* Convert pfn from Linux page size to balloon page size. */
67 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
68}
69
70static void balloon_ack(struct virtqueue *vq)
71{
72 struct virtio_balloon *vb;
73 unsigned int len;
74
75 vb = virtqueue_get_buf(vq, &len);
76 if (vb)
77 complete(&vb->acked);
78}
79
80static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
81{
82 struct scatterlist sg;
83
84 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
85
86 init_completion(&vb->acked);
87
88 /* We should always be able to add one buffer to an empty queue. */
89 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0)
90 BUG();
91 virtqueue_kick(vq);
92
93 /* When host has read buffer, this completes via balloon_ack */
94 wait_for_completion(&vb->acked);
95}
96
97static void fill_balloon(struct virtio_balloon *vb, size_t num)
98{
99 /* We can only do one array worth at a time. */
100 num = min(num, ARRAY_SIZE(vb->pfns));
101
102 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
103 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
104 __GFP_NOMEMALLOC | __GFP_NOWARN);
105 if (!page) {
106 if (printk_ratelimit())
107 dev_printk(KERN_INFO, &vb->vdev->dev,
108 "Out of puff! Can't get %zu pages\n",
109 num);
110 /* Sleep for at least 1/5 of a second before retry. */
111 msleep(200);
112 break;
113 }
114 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
115 totalram_pages--;
116 vb->num_pages++;
117 list_add(&page->lru, &vb->pages);
118 }
119
120 /* Didn't get any? Oh well. */
121 if (vb->num_pfns == 0)
122 return;
123
124 tell_host(vb, vb->inflate_vq);
125}
126
127static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
128{
129 unsigned int i;
130
131 for (i = 0; i < num; i++) {
132 __free_page(pfn_to_page(pfns[i]));
133 totalram_pages++;
134 }
135}
136
137static void leak_balloon(struct virtio_balloon *vb, size_t num)
138{
139 struct page *page;
140
141 /* We can only do one array worth at a time. */
142 num = min(num, ARRAY_SIZE(vb->pfns));
143
144 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
145 page = list_first_entry(&vb->pages, struct page, lru);
146 list_del(&page->lru);
147 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
148 vb->num_pages--;
149 }
150
151
152 /*
153 * Note that if
154 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
155 * is true, we *have* to do it in this order
156 */
157 tell_host(vb, vb->deflate_vq);
158 release_pages_by_pfn(vb->pfns, vb->num_pfns);
159}
160
161static inline void update_stat(struct virtio_balloon *vb, int idx,
162 u16 tag, u64 val)
163{
164 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
165 vb->stats[idx].tag = tag;
166 vb->stats[idx].val = val;
167}
168
169#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
170
171static void update_balloon_stats(struct virtio_balloon *vb)
172{
173 unsigned long events[NR_VM_EVENT_ITEMS];
174 struct sysinfo i;
175 int idx = 0;
176
177 all_vm_events(events);
178 si_meminfo(&i);
179
180 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
181 pages_to_bytes(events[PSWPIN]));
182 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
183 pages_to_bytes(events[PSWPOUT]));
184 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
185 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
186 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
187 pages_to_bytes(i.freeram));
188 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
189 pages_to_bytes(i.totalram));
190}
191
192/*
193 * While most virtqueues communicate guest-initiated requests to the hypervisor,
194 * the stats queue operates in reverse. The driver initializes the virtqueue
195 * with a single buffer. From that point forward, all conversations consist of
196 * a hypervisor request (a call to this function) which directs us to refill
197 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
198 * we notify our kthread which does the actual work via stats_handle_request().
199 */
200static void stats_request(struct virtqueue *vq)
201{
202 struct virtio_balloon *vb;
203 unsigned int len;
204
205 vb = virtqueue_get_buf(vq, &len);
206 if (!vb)
207 return;
208 vb->need_stats_update = 1;
209 wake_up(&vb->config_change);
210}
211
212static void stats_handle_request(struct virtio_balloon *vb)
213{
214 struct virtqueue *vq;
215 struct scatterlist sg;
216
217 vb->need_stats_update = 0;
218 update_balloon_stats(vb);
219
220 vq = vb->stats_vq;
221 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
222 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0)
223 BUG();
224 virtqueue_kick(vq);
225}
226
227static void virtballoon_changed(struct virtio_device *vdev)
228{
229 struct virtio_balloon *vb = vdev->priv;
230
231 wake_up(&vb->config_change);
232}
233
234static inline s64 towards_target(struct virtio_balloon *vb)
235{
236 u32 v;
237 vb->vdev->config->get(vb->vdev,
238 offsetof(struct virtio_balloon_config, num_pages),
239 &v, sizeof(v));
240 return (s64)v - vb->num_pages;
241}
242
243static void update_balloon_size(struct virtio_balloon *vb)
244{
245 __le32 actual = cpu_to_le32(vb->num_pages);
246
247 vb->vdev->config->set(vb->vdev,
248 offsetof(struct virtio_balloon_config, actual),
249 &actual, sizeof(actual));
250}
251
252static int balloon(void *_vballoon)
253{
254 struct virtio_balloon *vb = _vballoon;
255
256 set_freezable();
257 while (!kthread_should_stop()) {
258 s64 diff;
259
260 try_to_freeze();
261 wait_event_interruptible(vb->config_change,
262 (diff = towards_target(vb)) != 0
263 || vb->need_stats_update
264 || kthread_should_stop()
265 || freezing(current));
266 if (vb->need_stats_update)
267 stats_handle_request(vb);
268 if (diff > 0)
269 fill_balloon(vb, diff);
270 else if (diff < 0)
271 leak_balloon(vb, -diff);
272 update_balloon_size(vb);
273 }
274 return 0;
275}
276
277static int virtballoon_probe(struct virtio_device *vdev)
278{
279 struct virtio_balloon *vb;
280 struct virtqueue *vqs[3];
281 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
282 const char *names[] = { "inflate", "deflate", "stats" };
283 int err, nvqs;
284
285 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
286 if (!vb) {
287 err = -ENOMEM;
288 goto out;
289 }
290
291 INIT_LIST_HEAD(&vb->pages);
292 vb->num_pages = 0;
293 init_waitqueue_head(&vb->config_change);
294 vb->vdev = vdev;
295 vb->need_stats_update = 0;
296
297 /* We expect two virtqueues: inflate and deflate,
298 * and optionally stat. */
299 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
300 err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
301 if (err)
302 goto out_free_vb;
303
304 vb->inflate_vq = vqs[0];
305 vb->deflate_vq = vqs[1];
306 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
307 struct scatterlist sg;
308 vb->stats_vq = vqs[2];
309
310 /*
311 * Prime this virtqueue with one buffer so the hypervisor can
312 * use it to signal us later.
313 */
314 sg_init_one(&sg, vb->stats, sizeof vb->stats);
315 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb) < 0)
316 BUG();
317 virtqueue_kick(vb->stats_vq);
318 }
319
320 vb->thread = kthread_run(balloon, vb, "vballoon");
321 if (IS_ERR(vb->thread)) {
322 err = PTR_ERR(vb->thread);
323 goto out_del_vqs;
324 }
325
326 return 0;
327
328out_del_vqs:
329 vdev->config->del_vqs(vdev);
330out_free_vb:
331 kfree(vb);
332out:
333 return err;
334}
335
336static void __devexit virtballoon_remove(struct virtio_device *vdev)
337{
338 struct virtio_balloon *vb = vdev->priv;
339
340 kthread_stop(vb->thread);
341
342 /* There might be pages left in the balloon: free them. */
343 while (vb->num_pages)
344 leak_balloon(vb, vb->num_pages);
345
346 /* Now we reset the device so we can clean up the queues. */
347 vdev->config->reset(vdev);
348
349 vdev->config->del_vqs(vdev);
350 kfree(vb);
351}
352
353static unsigned int features[] = {
354 VIRTIO_BALLOON_F_MUST_TELL_HOST,
355 VIRTIO_BALLOON_F_STATS_VQ,
356};
357
358static struct virtio_driver virtio_balloon_driver = {
359 .feature_table = features,
360 .feature_table_size = ARRAY_SIZE(features),
361 .driver.name = KBUILD_MODNAME,
362 .driver.owner = THIS_MODULE,
363 .id_table = id_table,
364 .probe = virtballoon_probe,
365 .remove = __devexit_p(virtballoon_remove),
366 .config_changed = virtballoon_changed,
367};
368
369static int __init init(void)
370{
371 return register_virtio_driver(&virtio_balloon_driver);
372}
373
374static void __exit fini(void)
375{
376 unregister_virtio_driver(&virtio_balloon_driver);
377}
378module_init(init);
379module_exit(fini);
380
381MODULE_DEVICE_TABLE(virtio, id_table);
382MODULE_DESCRIPTION("Virtio balloon driver");
383MODULE_LICENSE("GPL");
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/oom.h>
31#include <linux/wait.h>
32#include <linux/mm.h>
33
34/*
35 * Balloon device works in 4K page units. So each page is pointed to by
36 * multiple balloon pages. All memory counters in this driver are in balloon
37 * page units.
38 */
39#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
40#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
41#define OOM_VBALLOON_DEFAULT_PAGES 256
42#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
43
44static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
45module_param(oom_pages, int, S_IRUSR | S_IWUSR);
46MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
47
48struct virtio_balloon {
49 struct virtio_device *vdev;
50 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
51
52 /* The balloon servicing is delegated to a freezable workqueue. */
53 struct work_struct update_balloon_stats_work;
54 struct work_struct update_balloon_size_work;
55
56 /* Prevent updating balloon when it is being canceled. */
57 spinlock_t stop_update_lock;
58 bool stop_update;
59
60 /* Waiting for host to ack the pages we released. */
61 wait_queue_head_t acked;
62
63 /* Number of balloon pages we've told the Host we're not using. */
64 unsigned int num_pages;
65 /*
66 * The pages we've told the Host we're not using are enqueued
67 * at vb_dev_info->pages list.
68 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
69 * to num_pages above.
70 */
71 struct balloon_dev_info vb_dev_info;
72
73 /* Synchronize access/update to this struct virtio_balloon elements */
74 struct mutex balloon_lock;
75
76 /* The array of pfns we tell the Host about. */
77 unsigned int num_pfns;
78 u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
79
80 /* Memory statistics */
81 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
82
83 /* To register callback in oom notifier call chain */
84 struct notifier_block nb;
85};
86
87static struct virtio_device_id id_table[] = {
88 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
89 { 0 },
90};
91
92static u32 page_to_balloon_pfn(struct page *page)
93{
94 unsigned long pfn = page_to_pfn(page);
95
96 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
97 /* Convert pfn from Linux page size to balloon page size. */
98 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
99}
100
101static struct page *balloon_pfn_to_page(u32 pfn)
102{
103 BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
104 return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
105}
106
107static void balloon_ack(struct virtqueue *vq)
108{
109 struct virtio_balloon *vb = vq->vdev->priv;
110
111 wake_up(&vb->acked);
112}
113
114static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
115{
116 struct scatterlist sg;
117 unsigned int len;
118
119 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
120
121 /* We should always be able to add one buffer to an empty queue. */
122 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
123 virtqueue_kick(vq);
124
125 /* When host has read buffer, this completes via balloon_ack */
126 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
127
128}
129
130static void set_page_pfns(u32 pfns[], struct page *page)
131{
132 unsigned int i;
133
134 /* Set balloon pfns pointing at this page.
135 * Note that the first pfn points at start of the page. */
136 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
137 pfns[i] = page_to_balloon_pfn(page) + i;
138}
139
140static unsigned fill_balloon(struct virtio_balloon *vb, size_t num)
141{
142 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
143 unsigned num_allocated_pages;
144
145 /* We can only do one array worth at a time. */
146 num = min(num, ARRAY_SIZE(vb->pfns));
147
148 mutex_lock(&vb->balloon_lock);
149 for (vb->num_pfns = 0; vb->num_pfns < num;
150 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
151 struct page *page = balloon_page_enqueue(vb_dev_info);
152
153 if (!page) {
154 dev_info_ratelimited(&vb->vdev->dev,
155 "Out of puff! Can't get %u pages\n",
156 VIRTIO_BALLOON_PAGES_PER_PAGE);
157 /* Sleep for at least 1/5 of a second before retry. */
158 msleep(200);
159 break;
160 }
161 set_page_pfns(vb->pfns + vb->num_pfns, page);
162 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
163 if (!virtio_has_feature(vb->vdev,
164 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
165 adjust_managed_page_count(page, -1);
166 }
167
168 num_allocated_pages = vb->num_pfns;
169 /* Did we get any? */
170 if (vb->num_pfns != 0)
171 tell_host(vb, vb->inflate_vq);
172 mutex_unlock(&vb->balloon_lock);
173
174 return num_allocated_pages;
175}
176
177static void release_pages_balloon(struct virtio_balloon *vb)
178{
179 unsigned int i;
180
181 /* Find pfns pointing at start of each page, get pages and free them. */
182 for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
183 struct page *page = balloon_pfn_to_page(vb->pfns[i]);
184 if (!virtio_has_feature(vb->vdev,
185 VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
186 adjust_managed_page_count(page, 1);
187 put_page(page); /* balloon reference */
188 }
189}
190
191static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
192{
193 unsigned num_freed_pages;
194 struct page *page;
195 struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
196
197 /* We can only do one array worth at a time. */
198 num = min(num, ARRAY_SIZE(vb->pfns));
199
200 mutex_lock(&vb->balloon_lock);
201 for (vb->num_pfns = 0; vb->num_pfns < num;
202 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
203 page = balloon_page_dequeue(vb_dev_info);
204 if (!page)
205 break;
206 set_page_pfns(vb->pfns + vb->num_pfns, page);
207 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
208 }
209
210 num_freed_pages = vb->num_pfns;
211 /*
212 * Note that if
213 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
214 * is true, we *have* to do it in this order
215 */
216 if (vb->num_pfns != 0)
217 tell_host(vb, vb->deflate_vq);
218 release_pages_balloon(vb);
219 mutex_unlock(&vb->balloon_lock);
220 return num_freed_pages;
221}
222
223static inline void update_stat(struct virtio_balloon *vb, int idx,
224 u16 tag, u64 val)
225{
226 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
227 vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
228 vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
229}
230
231#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
232
233static void update_balloon_stats(struct virtio_balloon *vb)
234{
235 unsigned long events[NR_VM_EVENT_ITEMS];
236 struct sysinfo i;
237 int idx = 0;
238 long available;
239
240 all_vm_events(events);
241 si_meminfo(&i);
242
243 available = si_mem_available();
244
245 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
246 pages_to_bytes(events[PSWPIN]));
247 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
248 pages_to_bytes(events[PSWPOUT]));
249 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
250 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
251 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
252 pages_to_bytes(i.freeram));
253 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
254 pages_to_bytes(i.totalram));
255 update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
256 pages_to_bytes(available));
257}
258
259/*
260 * While most virtqueues communicate guest-initiated requests to the hypervisor,
261 * the stats queue operates in reverse. The driver initializes the virtqueue
262 * with a single buffer. From that point forward, all conversations consist of
263 * a hypervisor request (a call to this function) which directs us to refill
264 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
265 * we delegate the job to a freezable workqueue that will do the actual work via
266 * stats_handle_request().
267 */
268static void stats_request(struct virtqueue *vq)
269{
270 struct virtio_balloon *vb = vq->vdev->priv;
271
272 spin_lock(&vb->stop_update_lock);
273 if (!vb->stop_update)
274 queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
275 spin_unlock(&vb->stop_update_lock);
276}
277
278static void stats_handle_request(struct virtio_balloon *vb)
279{
280 struct virtqueue *vq;
281 struct scatterlist sg;
282 unsigned int len;
283
284 update_balloon_stats(vb);
285
286 vq = vb->stats_vq;
287 if (!virtqueue_get_buf(vq, &len))
288 return;
289 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
290 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
291 virtqueue_kick(vq);
292}
293
294static void virtballoon_changed(struct virtio_device *vdev)
295{
296 struct virtio_balloon *vb = vdev->priv;
297 unsigned long flags;
298
299 spin_lock_irqsave(&vb->stop_update_lock, flags);
300 if (!vb->stop_update)
301 queue_work(system_freezable_wq, &vb->update_balloon_size_work);
302 spin_unlock_irqrestore(&vb->stop_update_lock, flags);
303}
304
305static inline s64 towards_target(struct virtio_balloon *vb)
306{
307 s64 target;
308 u32 num_pages;
309
310 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
311 &num_pages);
312
313 /* Legacy balloon config space is LE, unlike all other devices. */
314 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
315 num_pages = le32_to_cpu((__force __le32)num_pages);
316
317 target = num_pages;
318 return target - vb->num_pages;
319}
320
321static void update_balloon_size(struct virtio_balloon *vb)
322{
323 u32 actual = vb->num_pages;
324
325 /* Legacy balloon config space is LE, unlike all other devices. */
326 if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
327 actual = (__force u32)cpu_to_le32(actual);
328
329 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
330 &actual);
331}
332
333/*
334 * virtballoon_oom_notify - release pages when system is under severe
335 * memory pressure (called from out_of_memory())
336 * @self : notifier block struct
337 * @dummy: not used
338 * @parm : returned - number of freed pages
339 *
340 * The balancing of memory by use of the virtio balloon should not cause
341 * the termination of processes while there are pages in the balloon.
342 * If virtio balloon manages to release some memory, it will make the
343 * system return and retry the allocation that forced the OOM killer
344 * to run.
345 */
346static int virtballoon_oom_notify(struct notifier_block *self,
347 unsigned long dummy, void *parm)
348{
349 struct virtio_balloon *vb;
350 unsigned long *freed;
351 unsigned num_freed_pages;
352
353 vb = container_of(self, struct virtio_balloon, nb);
354 if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
355 return NOTIFY_OK;
356
357 freed = parm;
358 num_freed_pages = leak_balloon(vb, oom_pages);
359 update_balloon_size(vb);
360 *freed += num_freed_pages;
361
362 return NOTIFY_OK;
363}
364
365static void update_balloon_stats_func(struct work_struct *work)
366{
367 struct virtio_balloon *vb;
368
369 vb = container_of(work, struct virtio_balloon,
370 update_balloon_stats_work);
371 stats_handle_request(vb);
372}
373
374static void update_balloon_size_func(struct work_struct *work)
375{
376 struct virtio_balloon *vb;
377 s64 diff;
378
379 vb = container_of(work, struct virtio_balloon,
380 update_balloon_size_work);
381 diff = towards_target(vb);
382
383 if (diff > 0)
384 diff -= fill_balloon(vb, diff);
385 else if (diff < 0)
386 diff += leak_balloon(vb, -diff);
387 update_balloon_size(vb);
388
389 if (diff)
390 queue_work(system_freezable_wq, work);
391}
392
393static int init_vqs(struct virtio_balloon *vb)
394{
395 struct virtqueue *vqs[3];
396 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
397 static const char * const names[] = { "inflate", "deflate", "stats" };
398 int err, nvqs;
399
400 /*
401 * We expect two virtqueues: inflate and deflate, and
402 * optionally stat.
403 */
404 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
405 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
406 if (err)
407 return err;
408
409 vb->inflate_vq = vqs[0];
410 vb->deflate_vq = vqs[1];
411 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
412 struct scatterlist sg;
413 vb->stats_vq = vqs[2];
414
415 /*
416 * Prime this virtqueue with one buffer so the hypervisor can
417 * use it to signal us later (it can't be broken yet!).
418 */
419 sg_init_one(&sg, vb->stats, sizeof vb->stats);
420 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
421 < 0)
422 BUG();
423 virtqueue_kick(vb->stats_vq);
424 }
425 return 0;
426}
427
428#ifdef CONFIG_BALLOON_COMPACTION
429/*
430 * virtballoon_migratepage - perform the balloon page migration on behalf of
431 * a compation thread. (called under page lock)
432 * @vb_dev_info: the balloon device
433 * @newpage: page that will replace the isolated page after migration finishes.
434 * @page : the isolated (old) page that is about to be migrated to newpage.
435 * @mode : compaction mode -- not used for balloon page migration.
436 *
437 * After a ballooned page gets isolated by compaction procedures, this is the
438 * function that performs the page migration on behalf of a compaction thread
439 * The page migration for virtio balloon is done in a simple swap fashion which
440 * follows these two macro steps:
441 * 1) insert newpage into vb->pages list and update the host about it;
442 * 2) update the host about the old page removed from vb->pages list;
443 *
444 * This function preforms the balloon page migration task.
445 * Called through balloon_mapping->a_ops->migratepage
446 */
447static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
448 struct page *newpage, struct page *page, enum migrate_mode mode)
449{
450 struct virtio_balloon *vb = container_of(vb_dev_info,
451 struct virtio_balloon, vb_dev_info);
452 unsigned long flags;
453
454 /*
455 * In order to avoid lock contention while migrating pages concurrently
456 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
457 * this turn, as it is easier to retry the page migration later.
458 * This also prevents fill_balloon() getting stuck into a mutex
459 * recursion in the case it ends up triggering memory compaction
460 * while it is attempting to inflate the ballon.
461 */
462 if (!mutex_trylock(&vb->balloon_lock))
463 return -EAGAIN;
464
465 get_page(newpage); /* balloon reference */
466
467 /* balloon's page migration 1st step -- inflate "newpage" */
468 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
469 balloon_page_insert(vb_dev_info, newpage);
470 vb_dev_info->isolated_pages--;
471 __count_vm_event(BALLOON_MIGRATE);
472 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
473 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
474 set_page_pfns(vb->pfns, newpage);
475 tell_host(vb, vb->inflate_vq);
476
477 /* balloon's page migration 2nd step -- deflate "page" */
478 balloon_page_delete(page);
479 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
480 set_page_pfns(vb->pfns, page);
481 tell_host(vb, vb->deflate_vq);
482
483 mutex_unlock(&vb->balloon_lock);
484
485 put_page(page); /* balloon reference */
486
487 return MIGRATEPAGE_SUCCESS;
488}
489#endif /* CONFIG_BALLOON_COMPACTION */
490
491static int virtballoon_probe(struct virtio_device *vdev)
492{
493 struct virtio_balloon *vb;
494 int err;
495
496 if (!vdev->config->get) {
497 dev_err(&vdev->dev, "%s failure: config access disabled\n",
498 __func__);
499 return -EINVAL;
500 }
501
502 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
503 if (!vb) {
504 err = -ENOMEM;
505 goto out;
506 }
507
508 INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
509 INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
510 spin_lock_init(&vb->stop_update_lock);
511 vb->stop_update = false;
512 vb->num_pages = 0;
513 mutex_init(&vb->balloon_lock);
514 init_waitqueue_head(&vb->acked);
515 vb->vdev = vdev;
516
517 balloon_devinfo_init(&vb->vb_dev_info);
518#ifdef CONFIG_BALLOON_COMPACTION
519 vb->vb_dev_info.migratepage = virtballoon_migratepage;
520#endif
521
522 err = init_vqs(vb);
523 if (err)
524 goto out_free_vb;
525
526 vb->nb.notifier_call = virtballoon_oom_notify;
527 vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
528 err = register_oom_notifier(&vb->nb);
529 if (err < 0)
530 goto out_oom_notify;
531
532 virtio_device_ready(vdev);
533
534 return 0;
535
536out_oom_notify:
537 vdev->config->del_vqs(vdev);
538out_free_vb:
539 kfree(vb);
540out:
541 return err;
542}
543
544static void remove_common(struct virtio_balloon *vb)
545{
546 /* There might be pages left in the balloon: free them. */
547 while (vb->num_pages)
548 leak_balloon(vb, vb->num_pages);
549 update_balloon_size(vb);
550
551 /* Now we reset the device so we can clean up the queues. */
552 vb->vdev->config->reset(vb->vdev);
553
554 vb->vdev->config->del_vqs(vb->vdev);
555}
556
557static void virtballoon_remove(struct virtio_device *vdev)
558{
559 struct virtio_balloon *vb = vdev->priv;
560
561 unregister_oom_notifier(&vb->nb);
562
563 spin_lock_irq(&vb->stop_update_lock);
564 vb->stop_update = true;
565 spin_unlock_irq(&vb->stop_update_lock);
566 cancel_work_sync(&vb->update_balloon_size_work);
567 cancel_work_sync(&vb->update_balloon_stats_work);
568
569 remove_common(vb);
570 kfree(vb);
571}
572
573#ifdef CONFIG_PM_SLEEP
574static int virtballoon_freeze(struct virtio_device *vdev)
575{
576 struct virtio_balloon *vb = vdev->priv;
577
578 /*
579 * The workqueue is already frozen by the PM core before this
580 * function is called.
581 */
582 remove_common(vb);
583 return 0;
584}
585
586static int virtballoon_restore(struct virtio_device *vdev)
587{
588 struct virtio_balloon *vb = vdev->priv;
589 int ret;
590
591 ret = init_vqs(vdev->priv);
592 if (ret)
593 return ret;
594
595 virtio_device_ready(vdev);
596
597 if (towards_target(vb))
598 virtballoon_changed(vdev);
599 update_balloon_size(vb);
600 return 0;
601}
602#endif
603
604static unsigned int features[] = {
605 VIRTIO_BALLOON_F_MUST_TELL_HOST,
606 VIRTIO_BALLOON_F_STATS_VQ,
607 VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
608};
609
610static struct virtio_driver virtio_balloon_driver = {
611 .feature_table = features,
612 .feature_table_size = ARRAY_SIZE(features),
613 .driver.name = KBUILD_MODNAME,
614 .driver.owner = THIS_MODULE,
615 .id_table = id_table,
616 .probe = virtballoon_probe,
617 .remove = virtballoon_remove,
618 .config_changed = virtballoon_changed,
619#ifdef CONFIG_PM_SLEEP
620 .freeze = virtballoon_freeze,
621 .restore = virtballoon_restore,
622#endif
623};
624
625module_virtio_driver(virtio_balloon_driver);
626MODULE_DEVICE_TABLE(virtio, id_table);
627MODULE_DESCRIPTION("Virtio balloon driver");
628MODULE_LICENSE("GPL");