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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 | ||
31 | struct virtio_balloon | |
32 | { | |
33 | struct virtio_device *vdev; | |
34 | struct virtqueue *inflate_vq, *deflate_vq, *stats_vq; | |
35 | ||
36 | /* Where the ballooning thread waits for config to change. */ | |
37 | wait_queue_head_t config_change; | |
38 | ||
39 | /* The thread servicing the balloon. */ | |
40 | struct task_struct *thread; | |
41 | ||
42 | /* Waiting for host to ack the pages we released. */ | |
43 | struct completion acked; | |
44 | ||
45 | /* The pages we've told the Host we're not using. */ | |
46 | unsigned int num_pages; | |
47 | struct list_head pages; | |
48 | ||
49 | /* The array of pfns we tell the Host about. */ | |
50 | unsigned int num_pfns; | |
51 | u32 pfns[256]; | |
52 | ||
53 | /* Memory statistics */ | |
54 | int need_stats_update; | |
55 | struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; | |
56 | }; | |
57 | ||
58 | static struct virtio_device_id id_table[] = { | |
59 | { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, | |
60 | { 0 }, | |
61 | }; | |
62 | ||
63 | static u32 page_to_balloon_pfn(struct page *page) | |
64 | { | |
65 | unsigned long pfn = page_to_pfn(page); | |
66 | ||
67 | BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); | |
68 | /* Convert pfn from Linux page size to balloon page size. */ | |
69 | return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); | |
70 | } | |
71 | ||
72 | static void balloon_ack(struct virtqueue *vq) | |
73 | { | |
74 | struct virtio_balloon *vb; | |
75 | unsigned int len; | |
76 | ||
77 | vb = virtqueue_get_buf(vq, &len); | |
78 | if (vb) | |
79 | complete(&vb->acked); | |
80 | } | |
81 | ||
82 | static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) | |
83 | { | |
84 | struct scatterlist sg; | |
85 | ||
86 | sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); | |
87 | ||
88 | init_completion(&vb->acked); | |
89 | ||
90 | /* We should always be able to add one buffer to an empty queue. */ | |
91 | if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0) | |
92 | BUG(); | |
93 | virtqueue_kick(vq); | |
94 | ||
95 | /* When host has read buffer, this completes via balloon_ack */ | |
96 | wait_for_completion(&vb->acked); | |
97 | } | |
98 | ||
99 | static void fill_balloon(struct virtio_balloon *vb, size_t num) | |
100 | { | |
101 | /* We can only do one array worth at a time. */ | |
102 | num = min(num, ARRAY_SIZE(vb->pfns)); | |
103 | ||
104 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { | |
105 | struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY | | |
106 | __GFP_NOMEMALLOC | __GFP_NOWARN); | |
107 | if (!page) { | |
108 | if (printk_ratelimit()) | |
109 | dev_printk(KERN_INFO, &vb->vdev->dev, | |
110 | "Out of puff! Can't get %zu pages\n", | |
111 | num); | |
112 | /* Sleep for at least 1/5 of a second before retry. */ | |
113 | msleep(200); | |
114 | break; | |
115 | } | |
116 | vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); | |
117 | totalram_pages--; | |
118 | vb->num_pages++; | |
119 | list_add(&page->lru, &vb->pages); | |
120 | } | |
121 | ||
122 | /* Didn't get any? Oh well. */ | |
123 | if (vb->num_pfns == 0) | |
124 | return; | |
125 | ||
126 | tell_host(vb, vb->inflate_vq); | |
127 | } | |
128 | ||
129 | static void release_pages_by_pfn(const u32 pfns[], unsigned int num) | |
130 | { | |
131 | unsigned int i; | |
132 | ||
133 | for (i = 0; i < num; i++) { | |
134 | __free_page(pfn_to_page(pfns[i])); | |
135 | totalram_pages++; | |
136 | } | |
137 | } | |
138 | ||
139 | static void leak_balloon(struct virtio_balloon *vb, size_t num) | |
140 | { | |
141 | struct page *page; | |
142 | ||
143 | /* We can only do one array worth at a time. */ | |
144 | num = min(num, ARRAY_SIZE(vb->pfns)); | |
145 | ||
146 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { | |
147 | page = list_first_entry(&vb->pages, struct page, lru); | |
148 | list_del(&page->lru); | |
149 | vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); | |
150 | vb->num_pages--; | |
151 | } | |
152 | ||
153 | /* | |
154 | * Note that if | |
155 | * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); | |
156 | * is true, we *have* to do it in this order | |
157 | */ | |
158 | tell_host(vb, vb->deflate_vq); | |
159 | release_pages_by_pfn(vb->pfns, vb->num_pfns); | |
160 | } | |
161 | ||
162 | static inline void update_stat(struct virtio_balloon *vb, int idx, | |
163 | u16 tag, u64 val) | |
164 | { | |
165 | BUG_ON(idx >= VIRTIO_BALLOON_S_NR); | |
166 | vb->stats[idx].tag = tag; | |
167 | vb->stats[idx].val = val; | |
168 | } | |
169 | ||
170 | #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) | |
171 | ||
172 | static void update_balloon_stats(struct virtio_balloon *vb) | |
173 | { | |
174 | unsigned long events[NR_VM_EVENT_ITEMS]; | |
175 | struct sysinfo i; | |
176 | int idx = 0; | |
177 | ||
178 | all_vm_events(events); | |
179 | si_meminfo(&i); | |
180 | ||
181 | update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, | |
182 | pages_to_bytes(events[PSWPIN])); | |
183 | update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, | |
184 | pages_to_bytes(events[PSWPOUT])); | |
185 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); | |
186 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); | |
187 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, | |
188 | pages_to_bytes(i.freeram)); | |
189 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, | |
190 | pages_to_bytes(i.totalram)); | |
191 | } | |
192 | ||
193 | /* | |
194 | * While most virtqueues communicate guest-initiated requests to the hypervisor, | |
195 | * the stats queue operates in reverse. The driver initializes the virtqueue | |
196 | * with a single buffer. From that point forward, all conversations consist of | |
197 | * a hypervisor request (a call to this function) which directs us to refill | |
198 | * the virtqueue with a fresh stats buffer. Since stats collection can sleep, | |
199 | * we notify our kthread which does the actual work via stats_handle_request(). | |
200 | */ | |
201 | static void stats_request(struct virtqueue *vq) | |
202 | { | |
203 | struct virtio_balloon *vb; | |
204 | unsigned int len; | |
205 | ||
206 | vb = virtqueue_get_buf(vq, &len); | |
207 | if (!vb) | |
208 | return; | |
209 | vb->need_stats_update = 1; | |
210 | wake_up(&vb->config_change); | |
211 | } | |
212 | ||
213 | static void stats_handle_request(struct virtio_balloon *vb) | |
214 | { | |
215 | struct virtqueue *vq; | |
216 | struct scatterlist sg; | |
217 | ||
218 | vb->need_stats_update = 0; | |
219 | update_balloon_stats(vb); | |
220 | ||
221 | vq = vb->stats_vq; | |
222 | sg_init_one(&sg, vb->stats, sizeof(vb->stats)); | |
223 | if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0) | |
224 | BUG(); | |
225 | virtqueue_kick(vq); | |
226 | } | |
227 | ||
228 | static void virtballoon_changed(struct virtio_device *vdev) | |
229 | { | |
230 | struct virtio_balloon *vb = vdev->priv; | |
231 | ||
232 | wake_up(&vb->config_change); | |
233 | } | |
234 | ||
235 | static inline s64 towards_target(struct virtio_balloon *vb) | |
236 | { | |
237 | u32 v; | |
238 | vb->vdev->config->get(vb->vdev, | |
239 | offsetof(struct virtio_balloon_config, num_pages), | |
240 | &v, sizeof(v)); | |
241 | return (s64)v - vb->num_pages; | |
242 | } | |
243 | ||
244 | static void update_balloon_size(struct virtio_balloon *vb) | |
245 | { | |
246 | __le32 actual = cpu_to_le32(vb->num_pages); | |
247 | ||
248 | vb->vdev->config->set(vb->vdev, | |
249 | offsetof(struct virtio_balloon_config, actual), | |
250 | &actual, sizeof(actual)); | |
251 | } | |
252 | ||
253 | static int balloon(void *_vballoon) | |
254 | { | |
255 | struct virtio_balloon *vb = _vballoon; | |
256 | ||
257 | set_freezable(); | |
258 | while (!kthread_should_stop()) { | |
259 | s64 diff; | |
260 | ||
261 | try_to_freeze(); | |
262 | wait_event_interruptible(vb->config_change, | |
263 | (diff = towards_target(vb)) != 0 | |
264 | || vb->need_stats_update | |
265 | || kthread_should_stop() | |
266 | || freezing(current)); | |
267 | if (vb->need_stats_update) | |
268 | stats_handle_request(vb); | |
269 | if (diff > 0) | |
270 | fill_balloon(vb, diff); | |
271 | else if (diff < 0) | |
272 | leak_balloon(vb, -diff); | |
273 | update_balloon_size(vb); | |
274 | } | |
275 | return 0; | |
276 | } | |
277 | ||
278 | static int virtballoon_probe(struct virtio_device *vdev) | |
279 | { | |
280 | struct virtio_balloon *vb; | |
281 | struct virtqueue *vqs[3]; | |
282 | vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; | |
283 | const char *names[] = { "inflate", "deflate", "stats" }; | |
284 | int err, nvqs; | |
285 | ||
286 | vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); | |
287 | if (!vb) { | |
288 | err = -ENOMEM; | |
289 | goto out; | |
290 | } | |
291 | ||
292 | INIT_LIST_HEAD(&vb->pages); | |
293 | vb->num_pages = 0; | |
294 | init_waitqueue_head(&vb->config_change); | |
295 | vb->vdev = vdev; | |
296 | vb->need_stats_update = 0; | |
297 | ||
298 | /* We expect two virtqueues: inflate and deflate, | |
299 | * and optionally stat. */ | |
300 | nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; | |
301 | err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names); | |
302 | if (err) | |
303 | goto out_free_vb; | |
304 | ||
305 | vb->inflate_vq = vqs[0]; | |
306 | vb->deflate_vq = vqs[1]; | |
307 | if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { | |
308 | struct scatterlist sg; | |
309 | vb->stats_vq = vqs[2]; | |
310 | ||
311 | /* | |
312 | * Prime this virtqueue with one buffer so the hypervisor can | |
313 | * use it to signal us later. | |
314 | */ | |
315 | sg_init_one(&sg, vb->stats, sizeof vb->stats); | |
316 | if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL) | |
317 | < 0) | |
318 | BUG(); | |
319 | virtqueue_kick(vb->stats_vq); | |
320 | } | |
321 | ||
322 | vb->thread = kthread_run(balloon, vb, "vballoon"); | |
323 | if (IS_ERR(vb->thread)) { | |
324 | err = PTR_ERR(vb->thread); | |
325 | goto out_del_vqs; | |
326 | } | |
327 | ||
328 | return 0; | |
329 | ||
330 | out_del_vqs: | |
331 | vdev->config->del_vqs(vdev); | |
332 | out_free_vb: | |
333 | kfree(vb); | |
334 | out: | |
335 | return err; | |
336 | } | |
337 | ||
338 | static void __devexit virtballoon_remove(struct virtio_device *vdev) | |
339 | { | |
340 | struct virtio_balloon *vb = vdev->priv; | |
341 | ||
342 | kthread_stop(vb->thread); | |
343 | ||
344 | /* There might be pages left in the balloon: free them. */ | |
345 | while (vb->num_pages) | |
346 | leak_balloon(vb, vb->num_pages); | |
347 | ||
348 | /* Now we reset the device so we can clean up the queues. */ | |
349 | vdev->config->reset(vdev); | |
350 | ||
351 | vdev->config->del_vqs(vdev); | |
352 | kfree(vb); | |
353 | } | |
354 | ||
355 | static unsigned int features[] = { | |
356 | VIRTIO_BALLOON_F_MUST_TELL_HOST, | |
357 | VIRTIO_BALLOON_F_STATS_VQ, | |
358 | }; | |
359 | ||
360 | static struct virtio_driver virtio_balloon_driver = { | |
361 | .feature_table = features, | |
362 | .feature_table_size = ARRAY_SIZE(features), | |
363 | .driver.name = KBUILD_MODNAME, | |
364 | .driver.owner = THIS_MODULE, | |
365 | .id_table = id_table, | |
366 | .probe = virtballoon_probe, | |
367 | .remove = __devexit_p(virtballoon_remove), | |
368 | .config_changed = virtballoon_changed, | |
369 | }; | |
370 | ||
371 | static int __init init(void) | |
372 | { | |
373 | return register_virtio_driver(&virtio_balloon_driver); | |
374 | } | |
375 | ||
376 | static void __exit fini(void) | |
377 | { | |
378 | unregister_virtio_driver(&virtio_balloon_driver); | |
379 | } | |
380 | module_init(init); | |
381 | module_exit(fini); | |
382 | ||
383 | MODULE_DEVICE_TABLE(virtio, id_table); | |
384 | MODULE_DESCRIPTION("Virtio balloon driver"); | |
385 | MODULE_LICENSE("GPL"); |