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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 | |
29 | struct 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 | /* Do we have to tell Host *before* we reuse pages? */ |
44 | bool tell_host_first; |
45 | |
46 | /* The pages we've told the Host we're not using. */ |
47 | unsigned int num_pages; |
48 | struct list_head pages; |
49 | |
50 | /* The array of pfns we tell the Host about. */ |
51 | unsigned int num_pfns; |
52 | u32 pfns[256]; |
53 | |
54 | /* Memory statistics */ |
55 | int need_stats_update; |
56 | struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR]; |
57 | }; |
58 | |
59 | static struct virtio_device_id id_table[] = { |
60 | { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, |
61 | { 0 }, |
62 | }; |
63 | |
64 | static u32 page_to_balloon_pfn(struct page *page) |
65 | { |
66 | unsigned long pfn = page_to_pfn(page); |
67 | |
68 | BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); |
69 | /* Convert pfn from Linux page size to balloon page size. */ |
70 | return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); |
71 | } |
72 | |
73 | static void balloon_ack(struct virtqueue *vq) |
74 | { |
75 | struct virtio_balloon *vb; |
76 | unsigned int len; |
77 | |
78 | vb = virtqueue_get_buf(vq, &len); |
79 | if (vb) |
80 | complete(&vb->acked); |
81 | } |
82 | |
83 | static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) |
84 | { |
85 | struct scatterlist sg; |
86 | |
87 | sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); |
88 | |
89 | init_completion(&vb->acked); |
90 | |
91 | /* We should always be able to add one buffer to an empty queue. */ |
92 | if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0) |
93 | BUG(); |
94 | virtqueue_kick(vq); |
95 | |
96 | /* When host has read buffer, this completes via balloon_ack */ |
97 | wait_for_completion(&vb->acked); |
98 | } |
99 | |
100 | static void fill_balloon(struct virtio_balloon *vb, size_t num) |
101 | { |
102 | /* We can only do one array worth at a time. */ |
103 | num = min(num, ARRAY_SIZE(vb->pfns)); |
104 | |
105 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { |
106 | struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY | |
107 | __GFP_NOMEMALLOC | __GFP_NOWARN); |
108 | if (!page) { |
109 | if (printk_ratelimit()) |
110 | dev_printk(KERN_INFO, &vb->vdev->dev, |
111 | "Out of puff! Can't get %zu pages\n", |
112 | num); |
113 | /* Sleep for at least 1/5 of a second before retry. */ |
114 | msleep(200); |
115 | break; |
116 | } |
117 | vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); |
118 | totalram_pages--; |
119 | vb->num_pages++; |
120 | list_add(&page->lru, &vb->pages); |
121 | } |
122 | |
123 | /* Didn't get any? Oh well. */ |
124 | if (vb->num_pfns == 0) |
125 | return; |
126 | |
127 | tell_host(vb, vb->inflate_vq); |
128 | } |
129 | |
130 | static void release_pages_by_pfn(const u32 pfns[], unsigned int num) |
131 | { |
132 | unsigned int i; |
133 | |
134 | for (i = 0; i < num; i++) { |
135 | __free_page(pfn_to_page(pfns[i])); |
136 | totalram_pages++; |
137 | } |
138 | } |
139 | |
140 | static void leak_balloon(struct virtio_balloon *vb, size_t num) |
141 | { |
142 | struct page *page; |
143 | |
144 | /* We can only do one array worth at a time. */ |
145 | num = min(num, ARRAY_SIZE(vb->pfns)); |
146 | |
147 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { |
148 | page = list_first_entry(&vb->pages, struct page, lru); |
149 | list_del(&page->lru); |
150 | vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); |
151 | vb->num_pages--; |
152 | } |
153 | |
154 | if (vb->tell_host_first) { |
155 | tell_host(vb, vb->deflate_vq); |
156 | release_pages_by_pfn(vb->pfns, vb->num_pfns); |
157 | } else { |
158 | release_pages_by_pfn(vb->pfns, vb->num_pfns); |
159 | tell_host(vb, vb->deflate_vq); |
160 | } |
161 | } |
162 | |
163 | static inline void update_stat(struct virtio_balloon *vb, int idx, |
164 | u16 tag, u64 val) |
165 | { |
166 | BUG_ON(idx >= VIRTIO_BALLOON_S_NR); |
167 | vb->stats[idx].tag = tag; |
168 | vb->stats[idx].val = val; |
169 | } |
170 | |
171 | #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT) |
172 | |
173 | static void update_balloon_stats(struct virtio_balloon *vb) |
174 | { |
175 | unsigned long events[NR_VM_EVENT_ITEMS]; |
176 | struct sysinfo i; |
177 | int idx = 0; |
178 | |
179 | all_vm_events(events); |
180 | si_meminfo(&i); |
181 | |
182 | update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN, |
183 | pages_to_bytes(events[PSWPIN])); |
184 | update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT, |
185 | pages_to_bytes(events[PSWPOUT])); |
186 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]); |
187 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]); |
188 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE, |
189 | pages_to_bytes(i.freeram)); |
190 | update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT, |
191 | pages_to_bytes(i.totalram)); |
192 | } |
193 | |
194 | /* |
195 | * While most virtqueues communicate guest-initiated requests to the hypervisor, |
196 | * the stats queue operates in reverse. The driver initializes the virtqueue |
197 | * with a single buffer. From that point forward, all conversations consist of |
198 | * a hypervisor request (a call to this function) which directs us to refill |
199 | * the virtqueue with a fresh stats buffer. Since stats collection can sleep, |
200 | * we notify our kthread which does the actual work via stats_handle_request(). |
201 | */ |
202 | static void stats_request(struct virtqueue *vq) |
203 | { |
204 | struct virtio_balloon *vb; |
205 | unsigned int len; |
206 | |
207 | vb = virtqueue_get_buf(vq, &len); |
208 | if (!vb) |
209 | return; |
210 | vb->need_stats_update = 1; |
211 | wake_up(&vb->config_change); |
212 | } |
213 | |
214 | static void stats_handle_request(struct virtio_balloon *vb) |
215 | { |
216 | struct virtqueue *vq; |
217 | struct scatterlist sg; |
218 | |
219 | vb->need_stats_update = 0; |
220 | update_balloon_stats(vb); |
221 | |
222 | vq = vb->stats_vq; |
223 | sg_init_one(&sg, vb->stats, sizeof(vb->stats)); |
224 | if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0) |
225 | BUG(); |
226 | virtqueue_kick(vq); |
227 | } |
228 | |
229 | static void virtballoon_changed(struct virtio_device *vdev) |
230 | { |
231 | struct virtio_balloon *vb = vdev->priv; |
232 | |
233 | wake_up(&vb->config_change); |
234 | } |
235 | |
236 | static inline s64 towards_target(struct virtio_balloon *vb) |
237 | { |
238 | u32 v; |
239 | vb->vdev->config->get(vb->vdev, |
240 | offsetof(struct virtio_balloon_config, num_pages), |
241 | &v, sizeof(v)); |
242 | return (s64)v - vb->num_pages; |
243 | } |
244 | |
245 | static void update_balloon_size(struct virtio_balloon *vb) |
246 | { |
247 | __le32 actual = cpu_to_le32(vb->num_pages); |
248 | |
249 | vb->vdev->config->set(vb->vdev, |
250 | offsetof(struct virtio_balloon_config, actual), |
251 | &actual, sizeof(actual)); |
252 | } |
253 | |
254 | static int balloon(void *_vballoon) |
255 | { |
256 | struct virtio_balloon *vb = _vballoon; |
257 | |
258 | set_freezable(); |
259 | while (!kthread_should_stop()) { |
260 | s64 diff; |
261 | |
262 | try_to_freeze(); |
263 | wait_event_interruptible(vb->config_change, |
264 | (diff = towards_target(vb)) != 0 |
265 | || vb->need_stats_update |
266 | || kthread_should_stop() |
267 | || freezing(current)); |
268 | if (vb->need_stats_update) |
269 | stats_handle_request(vb); |
270 | if (diff > 0) |
271 | fill_balloon(vb, diff); |
272 | else if (diff < 0) |
273 | leak_balloon(vb, -diff); |
274 | update_balloon_size(vb); |
275 | } |
276 | return 0; |
277 | } |
278 | |
279 | static int virtballoon_probe(struct virtio_device *vdev) |
280 | { |
281 | struct virtio_balloon *vb; |
282 | struct virtqueue *vqs[3]; |
283 | vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request }; |
284 | const char *names[] = { "inflate", "deflate", "stats" }; |
285 | int err, nvqs; |
286 | |
287 | vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); |
288 | if (!vb) { |
289 | err = -ENOMEM; |
290 | goto out; |
291 | } |
292 | |
293 | INIT_LIST_HEAD(&vb->pages); |
294 | vb->num_pages = 0; |
295 | init_waitqueue_head(&vb->config_change); |
296 | vb->vdev = vdev; |
297 | vb->need_stats_update = 0; |
298 | |
299 | /* We expect two virtqueues: inflate and deflate, |
300 | * and optionally stat. */ |
301 | nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2; |
302 | err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names); |
303 | if (err) |
304 | goto out_free_vb; |
305 | |
306 | vb->inflate_vq = vqs[0]; |
307 | vb->deflate_vq = vqs[1]; |
308 | if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { |
309 | struct scatterlist sg; |
310 | vb->stats_vq = vqs[2]; |
311 | |
312 | /* |
313 | * Prime this virtqueue with one buffer so the hypervisor can |
314 | * use it to signal us later. |
315 | */ |
316 | sg_init_one(&sg, vb->stats, sizeof vb->stats); |
317 | if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb) < 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 | vb->tell_host_first |
329 | = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); |
330 | |
331 | return 0; |
332 | |
333 | out_del_vqs: |
334 | vdev->config->del_vqs(vdev); |
335 | out_free_vb: |
336 | kfree(vb); |
337 | out: |
338 | return err; |
339 | } |
340 | |
341 | static void __devexit virtballoon_remove(struct virtio_device *vdev) |
342 | { |
343 | struct virtio_balloon *vb = vdev->priv; |
344 | |
345 | kthread_stop(vb->thread); |
346 | |
347 | /* There might be pages left in the balloon: free them. */ |
348 | while (vb->num_pages) |
349 | leak_balloon(vb, vb->num_pages); |
350 | |
351 | /* Now we reset the device so we can clean up the queues. */ |
352 | vdev->config->reset(vdev); |
353 | |
354 | vdev->config->del_vqs(vdev); |
355 | kfree(vb); |
356 | } |
357 | |
358 | static unsigned int features[] = { |
359 | VIRTIO_BALLOON_F_MUST_TELL_HOST, |
360 | VIRTIO_BALLOON_F_STATS_VQ, |
361 | }; |
362 | |
363 | static struct virtio_driver virtio_balloon_driver = { |
364 | .feature_table = features, |
365 | .feature_table_size = ARRAY_SIZE(features), |
366 | .driver.name = KBUILD_MODNAME, |
367 | .driver.owner = THIS_MODULE, |
368 | .id_table = id_table, |
369 | .probe = virtballoon_probe, |
370 | .remove = __devexit_p(virtballoon_remove), |
371 | .config_changed = virtballoon_changed, |
372 | }; |
373 | |
374 | static int __init init(void) |
375 | { |
376 | return register_virtio_driver(&virtio_balloon_driver); |
377 | } |
378 | |
379 | static void __exit fini(void) |
380 | { |
381 | unregister_virtio_driver(&virtio_balloon_driver); |
382 | } |
383 | module_init(init); |
384 | module_exit(fini); |
385 | |
386 | MODULE_DEVICE_TABLE(virtio, id_table); |
387 | MODULE_DESCRIPTION("Virtio balloon driver"); |
388 | MODULE_LICENSE("GPL"); |
389 |
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