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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
35 wait_queue_head_t config_change;
36
37
38 struct task_struct *thread;
39
40
41 struct completion acked;
42
43
44 unsigned int num_pages;
45 struct list_head pages;
46
47
48 unsigned int num_pfns;
49 u32 pfns[256];
50
51
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
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
89 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0)
90 BUG();
91 virtqueue_kick(vq);
92
93
94 wait_for_completion(&vb->acked);
95}
96
97static void fill_balloon(struct virtio_balloon *vb, size_t num)
98{
99
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
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
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
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
154
155
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
194
195
196
197
198
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
298
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
312
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
343 while (vb->num_pages)
344 leak_balloon(vb, vb->num_pages);
345
346
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");
384