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
page_to_balloon_pfn(struct page * page)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
balloon_ack(struct virtqueue * vq)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
tell_host(struct virtio_balloon * vb,struct virtqueue * vq)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
fill_balloon(struct virtio_balloon * vb,size_t num)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
release_pages_by_pfn(const u32 pfns[],unsigned int num)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
leak_balloon(struct virtio_balloon * vb,size_t num)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
update_stat(struct virtio_balloon * vb,int idx,u16 tag,u64 val)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
update_balloon_stats(struct virtio_balloon * vb)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 */
stats_request(struct virtqueue * vq)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
stats_handle_request(struct virtio_balloon * vb)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
virtballoon_changed(struct virtio_device * vdev)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
towards_target(struct virtio_balloon * vb)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
update_balloon_size(struct virtio_balloon * vb)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
balloon(void * _vballoon)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
virtballoon_probe(struct virtio_device * vdev)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
virtballoon_remove(struct virtio_device * vdev)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
init(void)374 static int __init init(void)
375 {
376 return register_virtio_driver(&virtio_balloon_driver);
377 }
378
fini(void)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