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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/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
32/*
33 * Balloon device works in 4K page units. So each page is pointed to by
34 * multiple balloon pages. All memory counters in this driver are in balloon
35 * page units.
36 */
37#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
38#define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
39
40struct virtio_balloon
41{
42 struct virtio_device *vdev;
43 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
44
45 /* Where the ballooning thread waits for config to change. */
46 wait_queue_head_t config_change;
47
48 /* The thread servicing the balloon. */
49 struct task_struct *thread;
50
51 /* Waiting for host to ack the pages we released. */
52 wait_queue_head_t acked;
53
54 /* Number of balloon pages we've told the Host we're not using. */
55 unsigned int num_pages;
56 /*
57 * The pages we've told the Host we're not using are enqueued
58 * at vb_dev_info->pages list.
59 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
60 * to num_pages above.
61 */
62 struct balloon_dev_info *vb_dev_info;
63
64 /* Synchronize access/update to this struct virtio_balloon elements */
65 struct mutex balloon_lock;
66
67 /* The array of pfns we tell the Host about. */
68 unsigned int num_pfns;
69 u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
70
71 /* Memory statistics */
72 int need_stats_update;
73 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
74};
75
76static struct virtio_device_id id_table[] = {
77 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
78 { 0 },
79};
80
81static u32 page_to_balloon_pfn(struct page *page)
82{
83 unsigned long pfn = page_to_pfn(page);
84
85 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
86 /* Convert pfn from Linux page size to balloon page size. */
87 return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
88}
89
90static struct page *balloon_pfn_to_page(u32 pfn)
91{
92 BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
93 return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
94}
95
96static void balloon_ack(struct virtqueue *vq)
97{
98 struct virtio_balloon *vb = vq->vdev->priv;
99
100 wake_up(&vb->acked);
101}
102
103static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
104{
105 struct scatterlist sg;
106 unsigned int len;
107
108 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
109
110 /* We should always be able to add one buffer to an empty queue. */
111 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
112 virtqueue_kick(vq);
113
114 /* When host has read buffer, this completes via balloon_ack */
115 wait_event(vb->acked, virtqueue_get_buf(vq, &len));
116}
117
118static void set_page_pfns(u32 pfns[], struct page *page)
119{
120 unsigned int i;
121
122 /* Set balloon pfns pointing at this page.
123 * Note that the first pfn points at start of the page. */
124 for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
125 pfns[i] = page_to_balloon_pfn(page) + i;
126}
127
128static void fill_balloon(struct virtio_balloon *vb, size_t num)
129{
130 struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
131
132 /* We can only do one array worth at a time. */
133 num = min(num, ARRAY_SIZE(vb->pfns));
134
135 mutex_lock(&vb->balloon_lock);
136 for (vb->num_pfns = 0; vb->num_pfns < num;
137 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
138 struct page *page = balloon_page_enqueue(vb_dev_info);
139
140 if (!page) {
141 dev_info_ratelimited(&vb->vdev->dev,
142 "Out of puff! Can't get %u pages\n",
143 VIRTIO_BALLOON_PAGES_PER_PAGE);
144 /* Sleep for at least 1/5 of a second before retry. */
145 msleep(200);
146 break;
147 }
148 set_page_pfns(vb->pfns + vb->num_pfns, page);
149 vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
150 adjust_managed_page_count(page, -1);
151 }
152
153 /* Did we get any? */
154 if (vb->num_pfns != 0)
155 tell_host(vb, vb->inflate_vq);
156 mutex_unlock(&vb->balloon_lock);
157}
158
159static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
160{
161 unsigned int i;
162
163 /* Find pfns pointing at start of each page, get pages and free them. */
164 for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
165 struct page *page = balloon_pfn_to_page(pfns[i]);
166 balloon_page_free(page);
167 adjust_managed_page_count(page, 1);
168 }
169}
170
171static void leak_balloon(struct virtio_balloon *vb, size_t num)
172{
173 struct page *page;
174 struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
175
176 /* We can only do one array worth at a time. */
177 num = min(num, ARRAY_SIZE(vb->pfns));
178
179 mutex_lock(&vb->balloon_lock);
180 for (vb->num_pfns = 0; vb->num_pfns < num;
181 vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
182 page = balloon_page_dequeue(vb_dev_info);
183 if (!page)
184 break;
185 set_page_pfns(vb->pfns + vb->num_pfns, page);
186 vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
187 }
188
189 /*
190 * Note that if
191 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
192 * is true, we *have* to do it in this order
193 */
194 if (vb->num_pfns != 0)
195 tell_host(vb, vb->deflate_vq);
196 mutex_unlock(&vb->balloon_lock);
197 release_pages_by_pfn(vb->pfns, vb->num_pfns);
198}
199
200static inline void update_stat(struct virtio_balloon *vb, int idx,
201 u16 tag, u64 val)
202{
203 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
204 vb->stats[idx].tag = tag;
205 vb->stats[idx].val = val;
206}
207
208#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
209
210static void update_balloon_stats(struct virtio_balloon *vb)
211{
212 unsigned long events[NR_VM_EVENT_ITEMS];
213 struct sysinfo i;
214 int idx = 0;
215
216 all_vm_events(events);
217 si_meminfo(&i);
218
219 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
220 pages_to_bytes(events[PSWPIN]));
221 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
222 pages_to_bytes(events[PSWPOUT]));
223 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
224 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
225 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
226 pages_to_bytes(i.freeram));
227 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
228 pages_to_bytes(i.totalram));
229}
230
231/*
232 * While most virtqueues communicate guest-initiated requests to the hypervisor,
233 * the stats queue operates in reverse. The driver initializes the virtqueue
234 * with a single buffer. From that point forward, all conversations consist of
235 * a hypervisor request (a call to this function) which directs us to refill
236 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
237 * we notify our kthread which does the actual work via stats_handle_request().
238 */
239static void stats_request(struct virtqueue *vq)
240{
241 struct virtio_balloon *vb = vq->vdev->priv;
242
243 vb->need_stats_update = 1;
244 wake_up(&vb->config_change);
245}
246
247static void stats_handle_request(struct virtio_balloon *vb)
248{
249 struct virtqueue *vq;
250 struct scatterlist sg;
251 unsigned int len;
252
253 vb->need_stats_update = 0;
254 update_balloon_stats(vb);
255
256 vq = vb->stats_vq;
257 if (!virtqueue_get_buf(vq, &len))
258 return;
259 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
260 virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
261 virtqueue_kick(vq);
262}
263
264static void virtballoon_changed(struct virtio_device *vdev)
265{
266 struct virtio_balloon *vb = vdev->priv;
267
268 wake_up(&vb->config_change);
269}
270
271static inline s64 towards_target(struct virtio_balloon *vb)
272{
273 __le32 v;
274 s64 target;
275
276 virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages, &v);
277
278 target = le32_to_cpu(v);
279 return target - vb->num_pages;
280}
281
282static void update_balloon_size(struct virtio_balloon *vb)
283{
284 __le32 actual = cpu_to_le32(vb->num_pages);
285
286 virtio_cwrite(vb->vdev, struct virtio_balloon_config, actual,
287 &actual);
288}
289
290static int balloon(void *_vballoon)
291{
292 struct virtio_balloon *vb = _vballoon;
293
294 set_freezable();
295 while (!kthread_should_stop()) {
296 s64 diff;
297
298 try_to_freeze();
299 wait_event_interruptible(vb->config_change,
300 (diff = towards_target(vb)) != 0
301 || vb->need_stats_update
302 || kthread_should_stop()
303 || freezing(current));
304 if (vb->need_stats_update)
305 stats_handle_request(vb);
306 if (diff > 0)
307 fill_balloon(vb, diff);
308 else if (diff < 0)
309 leak_balloon(vb, -diff);
310 update_balloon_size(vb);
311
312 /*
313 * For large balloon changes, we could spend a lot of time
314 * and always have work to do. Be nice if preempt disabled.
315 */
316 cond_resched();
317 }
318 return 0;
319}
320
321static int init_vqs(struct virtio_balloon *vb)
322{
323 struct virtqueue *vqs[3];
324 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
325 const char *names[] = { "inflate", "deflate", "stats" };
326 int err, nvqs;
327
328 /*
329 * We expect two virtqueues: inflate and deflate, and
330 * optionally stat.
331 */
332 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
333 err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
334 if (err)
335 return err;
336
337 vb->inflate_vq = vqs[0];
338 vb->deflate_vq = vqs[1];
339 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
340 struct scatterlist sg;
341 vb->stats_vq = vqs[2];
342
343 /*
344 * Prime this virtqueue with one buffer so the hypervisor can
345 * use it to signal us later (it can't be broken yet!).
346 */
347 sg_init_one(&sg, vb->stats, sizeof vb->stats);
348 if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
349 < 0)
350 BUG();
351 virtqueue_kick(vb->stats_vq);
352 }
353 return 0;
354}
355
356static const struct address_space_operations virtio_balloon_aops;
357#ifdef CONFIG_BALLOON_COMPACTION
358/*
359 * virtballoon_migratepage - perform the balloon page migration on behalf of
360 * a compation thread. (called under page lock)
361 * @mapping: the page->mapping which will be assigned to the new migrated page.
362 * @newpage: page that will replace the isolated page after migration finishes.
363 * @page : the isolated (old) page that is about to be migrated to newpage.
364 * @mode : compaction mode -- not used for balloon page migration.
365 *
366 * After a ballooned page gets isolated by compaction procedures, this is the
367 * function that performs the page migration on behalf of a compaction thread
368 * The page migration for virtio balloon is done in a simple swap fashion which
369 * follows these two macro steps:
370 * 1) insert newpage into vb->pages list and update the host about it;
371 * 2) update the host about the old page removed from vb->pages list;
372 *
373 * This function preforms the balloon page migration task.
374 * Called through balloon_mapping->a_ops->migratepage
375 */
376static int virtballoon_migratepage(struct address_space *mapping,
377 struct page *newpage, struct page *page, enum migrate_mode mode)
378{
379 struct balloon_dev_info *vb_dev_info = balloon_page_device(page);
380 struct virtio_balloon *vb;
381 unsigned long flags;
382
383 BUG_ON(!vb_dev_info);
384
385 vb = vb_dev_info->balloon_device;
386
387 /*
388 * In order to avoid lock contention while migrating pages concurrently
389 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
390 * this turn, as it is easier to retry the page migration later.
391 * This also prevents fill_balloon() getting stuck into a mutex
392 * recursion in the case it ends up triggering memory compaction
393 * while it is attempting to inflate the ballon.
394 */
395 if (!mutex_trylock(&vb->balloon_lock))
396 return -EAGAIN;
397
398 /* balloon's page migration 1st step -- inflate "newpage" */
399 spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
400 balloon_page_insert(newpage, mapping, &vb_dev_info->pages);
401 vb_dev_info->isolated_pages--;
402 spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
403 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
404 set_page_pfns(vb->pfns, newpage);
405 tell_host(vb, vb->inflate_vq);
406
407 /*
408 * balloon's page migration 2nd step -- deflate "page"
409 *
410 * It's safe to delete page->lru here because this page is at
411 * an isolated migration list, and this step is expected to happen here
412 */
413 balloon_page_delete(page);
414 vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
415 set_page_pfns(vb->pfns, page);
416 tell_host(vb, vb->deflate_vq);
417
418 mutex_unlock(&vb->balloon_lock);
419
420 return MIGRATEPAGE_BALLOON_SUCCESS;
421}
422
423/* define the balloon_mapping->a_ops callback to allow balloon page migration */
424static const struct address_space_operations virtio_balloon_aops = {
425 .migratepage = virtballoon_migratepage,
426};
427#endif /* CONFIG_BALLOON_COMPACTION */
428
429static int virtballoon_probe(struct virtio_device *vdev)
430{
431 struct virtio_balloon *vb;
432 struct address_space *vb_mapping;
433 struct balloon_dev_info *vb_devinfo;
434 int err;
435
436 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
437 if (!vb) {
438 err = -ENOMEM;
439 goto out;
440 }
441
442 vb->num_pages = 0;
443 mutex_init(&vb->balloon_lock);
444 init_waitqueue_head(&vb->config_change);
445 init_waitqueue_head(&vb->acked);
446 vb->vdev = vdev;
447 vb->need_stats_update = 0;
448
449 vb_devinfo = balloon_devinfo_alloc(vb);
450 if (IS_ERR(vb_devinfo)) {
451 err = PTR_ERR(vb_devinfo);
452 goto out_free_vb;
453 }
454
455 vb_mapping = balloon_mapping_alloc(vb_devinfo,
456 (balloon_compaction_check()) ?
457 &virtio_balloon_aops : NULL);
458 if (IS_ERR(vb_mapping)) {
459 /*
460 * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP
461 * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off.
462 */
463 err = PTR_ERR(vb_mapping);
464 if (err != -EOPNOTSUPP)
465 goto out_free_vb_devinfo;
466 }
467
468 vb->vb_dev_info = vb_devinfo;
469
470 err = init_vqs(vb);
471 if (err)
472 goto out_free_vb_mapping;
473
474 vb->thread = kthread_run(balloon, vb, "vballoon");
475 if (IS_ERR(vb->thread)) {
476 err = PTR_ERR(vb->thread);
477 goto out_del_vqs;
478 }
479
480 return 0;
481
482out_del_vqs:
483 vdev->config->del_vqs(vdev);
484out_free_vb_mapping:
485 balloon_mapping_free(vb_mapping);
486out_free_vb_devinfo:
487 balloon_devinfo_free(vb_devinfo);
488out_free_vb:
489 kfree(vb);
490out:
491 return err;
492}
493
494static void remove_common(struct virtio_balloon *vb)
495{
496 /* There might be pages left in the balloon: free them. */
497 while (vb->num_pages)
498 leak_balloon(vb, vb->num_pages);
499 update_balloon_size(vb);
500
501 /* Now we reset the device so we can clean up the queues. */
502 vb->vdev->config->reset(vb->vdev);
503
504 vb->vdev->config->del_vqs(vb->vdev);
505}
506
507static void virtballoon_remove(struct virtio_device *vdev)
508{
509 struct virtio_balloon *vb = vdev->priv;
510
511 kthread_stop(vb->thread);
512 remove_common(vb);
513 balloon_mapping_free(vb->vb_dev_info->mapping);
514 balloon_devinfo_free(vb->vb_dev_info);
515 kfree(vb);
516}
517
518#ifdef CONFIG_PM_SLEEP
519static int virtballoon_freeze(struct virtio_device *vdev)
520{
521 struct virtio_balloon *vb = vdev->priv;
522
523 /*
524 * The kthread is already frozen by the PM core before this
525 * function is called.
526 */
527
528 remove_common(vb);
529 return 0;
530}
531
532static int virtballoon_restore(struct virtio_device *vdev)
533{
534 struct virtio_balloon *vb = vdev->priv;
535 int ret;
536
537 ret = init_vqs(vdev->priv);
538 if (ret)
539 return ret;
540
541 fill_balloon(vb, towards_target(vb));
542 update_balloon_size(vb);
543 return 0;
544}
545#endif
546
547static unsigned int features[] = {
548 VIRTIO_BALLOON_F_MUST_TELL_HOST,
549 VIRTIO_BALLOON_F_STATS_VQ,
550};
551
552static struct virtio_driver virtio_balloon_driver = {
553 .feature_table = features,
554 .feature_table_size = ARRAY_SIZE(features),
555 .driver.name = KBUILD_MODNAME,
556 .driver.owner = THIS_MODULE,
557 .id_table = id_table,
558 .probe = virtballoon_probe,
559 .remove = virtballoon_remove,
560 .config_changed = virtballoon_changed,
561#ifdef CONFIG_PM_SLEEP
562 .freeze = virtballoon_freeze,
563 .restore = virtballoon_restore,
564#endif
565};
566
567module_virtio_driver(virtio_balloon_driver);
568MODULE_DEVICE_TABLE(virtio, id_table);
569MODULE_DESCRIPTION("Virtio balloon driver");
570MODULE_LICENSE("GPL");