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6b35e407 RR |
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> | |
6659a0f0 | 26 | #include <linux/delay.h> |
6b35e407 RR |
27 | |
28 | struct virtio_balloon | |
29 | { | |
30 | struct virtio_device *vdev; | |
31 | struct virtqueue *inflate_vq, *deflate_vq; | |
32 | ||
33 | /* Where the ballooning thread waits for config to change. */ | |
34 | wait_queue_head_t config_change; | |
35 | ||
36 | /* The thread servicing the balloon. */ | |
37 | struct task_struct *thread; | |
38 | ||
39 | /* Waiting for host to ack the pages we released. */ | |
40 | struct completion acked; | |
41 | ||
42 | /* Do we have to tell Host *before* we reuse pages? */ | |
43 | bool tell_host_first; | |
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 | ||
54 | static struct virtio_device_id id_table[] = { | |
55 | { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID }, | |
56 | { 0 }, | |
57 | }; | |
58 | ||
1b4aa2fa HB |
59 | static u32 page_to_balloon_pfn(struct page *page) |
60 | { | |
61 | unsigned long pfn = page_to_pfn(page); | |
62 | ||
63 | BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT); | |
64 | /* Convert pfn from Linux page size to balloon page size. */ | |
65 | return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT); | |
66 | } | |
67 | ||
6b35e407 RR |
68 | static void balloon_ack(struct virtqueue *vq) |
69 | { | |
70 | struct virtio_balloon *vb; | |
71 | unsigned int len; | |
72 | ||
73 | vb = vq->vq_ops->get_buf(vq, &len); | |
74 | if (vb) | |
75 | complete(&vb->acked); | |
76 | } | |
77 | ||
78 | static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) | |
79 | { | |
80 | struct scatterlist sg; | |
81 | ||
82 | sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); | |
83 | ||
84 | init_completion(&vb->acked); | |
85 | ||
86 | /* We should always be able to add one buffer to an empty queue. */ | |
87 | if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0) | |
88 | BUG(); | |
89 | vq->vq_ops->kick(vq); | |
90 | ||
91 | /* When host has read buffer, this completes via balloon_ack */ | |
92 | wait_for_completion(&vb->acked); | |
93 | } | |
94 | ||
95 | static void fill_balloon(struct virtio_balloon *vb, size_t num) | |
96 | { | |
97 | /* We can only do one array worth at a time. */ | |
98 | num = min(num, ARRAY_SIZE(vb->pfns)); | |
99 | ||
100 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { | |
101 | struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY); | |
102 | if (!page) { | |
103 | if (printk_ratelimit()) | |
104 | dev_printk(KERN_INFO, &vb->vdev->dev, | |
105 | "Out of puff! Can't get %zu pages\n", | |
106 | num); | |
107 | /* Sleep for at least 1/5 of a second before retry. */ | |
108 | msleep(200); | |
109 | break; | |
110 | } | |
1b4aa2fa | 111 | vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); |
6b35e407 RR |
112 | totalram_pages--; |
113 | vb->num_pages++; | |
114 | list_add(&page->lru, &vb->pages); | |
115 | } | |
116 | ||
117 | /* Didn't get any? Oh well. */ | |
118 | if (vb->num_pfns == 0) | |
119 | return; | |
120 | ||
121 | tell_host(vb, vb->inflate_vq); | |
122 | } | |
123 | ||
124 | static void release_pages_by_pfn(const u32 pfns[], unsigned int num) | |
125 | { | |
126 | unsigned int i; | |
127 | ||
128 | for (i = 0; i < num; i++) { | |
129 | __free_page(pfn_to_page(pfns[i])); | |
130 | totalram_pages++; | |
131 | } | |
132 | } | |
133 | ||
134 | static void leak_balloon(struct virtio_balloon *vb, size_t num) | |
135 | { | |
136 | struct page *page; | |
137 | ||
138 | /* We can only do one array worth at a time. */ | |
139 | num = min(num, ARRAY_SIZE(vb->pfns)); | |
140 | ||
141 | for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) { | |
142 | page = list_first_entry(&vb->pages, struct page, lru); | |
143 | list_del(&page->lru); | |
1b4aa2fa | 144 | vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page); |
6b35e407 RR |
145 | vb->num_pages--; |
146 | } | |
147 | ||
148 | if (vb->tell_host_first) { | |
149 | tell_host(vb, vb->deflate_vq); | |
150 | release_pages_by_pfn(vb->pfns, vb->num_pfns); | |
151 | } else { | |
152 | release_pages_by_pfn(vb->pfns, vb->num_pfns); | |
153 | tell_host(vb, vb->deflate_vq); | |
154 | } | |
155 | } | |
156 | ||
157 | static void virtballoon_changed(struct virtio_device *vdev) | |
158 | { | |
159 | struct virtio_balloon *vb = vdev->priv; | |
160 | ||
161 | wake_up(&vb->config_change); | |
162 | } | |
163 | ||
bdc1681c | 164 | static inline s64 towards_target(struct virtio_balloon *vb) |
6b35e407 RR |
165 | { |
166 | u32 v; | |
72e61eb4 RR |
167 | vb->vdev->config->get(vb->vdev, |
168 | offsetof(struct virtio_balloon_config, num_pages), | |
169 | &v, sizeof(v)); | |
532a6086 | 170 | return (s64)v - vb->num_pages; |
6b35e407 RR |
171 | } |
172 | ||
173 | static void update_balloon_size(struct virtio_balloon *vb) | |
174 | { | |
175 | __le32 actual = cpu_to_le32(vb->num_pages); | |
176 | ||
177 | vb->vdev->config->set(vb->vdev, | |
178 | offsetof(struct virtio_balloon_config, actual), | |
179 | &actual, sizeof(actual)); | |
180 | } | |
181 | ||
182 | static int balloon(void *_vballoon) | |
183 | { | |
184 | struct virtio_balloon *vb = _vballoon; | |
185 | ||
186 | set_freezable(); | |
187 | while (!kthread_should_stop()) { | |
bdc1681c | 188 | s64 diff; |
6b35e407 RR |
189 | |
190 | try_to_freeze(); | |
191 | wait_event_interruptible(vb->config_change, | |
192 | (diff = towards_target(vb)) != 0 | |
193 | || kthread_should_stop()); | |
194 | if (diff > 0) | |
195 | fill_balloon(vb, diff); | |
196 | else if (diff < 0) | |
197 | leak_balloon(vb, -diff); | |
198 | update_balloon_size(vb); | |
199 | } | |
200 | return 0; | |
201 | } | |
202 | ||
203 | static int virtballoon_probe(struct virtio_device *vdev) | |
204 | { | |
205 | struct virtio_balloon *vb; | |
206 | int err; | |
207 | ||
208 | vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL); | |
209 | if (!vb) { | |
210 | err = -ENOMEM; | |
211 | goto out; | |
212 | } | |
213 | ||
214 | INIT_LIST_HEAD(&vb->pages); | |
215 | vb->num_pages = 0; | |
216 | init_waitqueue_head(&vb->config_change); | |
217 | vb->vdev = vdev; | |
218 | ||
219 | /* We expect two virtqueues. */ | |
220 | vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack); | |
221 | if (IS_ERR(vb->inflate_vq)) { | |
222 | err = PTR_ERR(vb->inflate_vq); | |
223 | goto out_free_vb; | |
224 | } | |
225 | ||
226 | vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack); | |
227 | if (IS_ERR(vb->deflate_vq)) { | |
228 | err = PTR_ERR(vb->deflate_vq); | |
229 | goto out_del_inflate_vq; | |
230 | } | |
231 | ||
232 | vb->thread = kthread_run(balloon, vb, "vballoon"); | |
233 | if (IS_ERR(vb->thread)) { | |
234 | err = PTR_ERR(vb->thread); | |
235 | goto out_del_deflate_vq; | |
236 | } | |
237 | ||
238 | vb->tell_host_first | |
c45a6816 | 239 | = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); |
6b35e407 RR |
240 | |
241 | return 0; | |
242 | ||
243 | out_del_deflate_vq: | |
244 | vdev->config->del_vq(vb->deflate_vq); | |
245 | out_del_inflate_vq: | |
246 | vdev->config->del_vq(vb->inflate_vq); | |
247 | out_free_vb: | |
248 | kfree(vb); | |
249 | out: | |
250 | return err; | |
251 | } | |
252 | ||
253 | static void virtballoon_remove(struct virtio_device *vdev) | |
254 | { | |
255 | struct virtio_balloon *vb = vdev->priv; | |
256 | ||
257 | kthread_stop(vb->thread); | |
258 | ||
259 | /* There might be pages left in the balloon: free them. */ | |
260 | while (vb->num_pages) | |
261 | leak_balloon(vb, vb->num_pages); | |
262 | ||
263 | /* Now we reset the device so we can clean up the queues. */ | |
264 | vdev->config->reset(vdev); | |
265 | ||
266 | vdev->config->del_vq(vb->deflate_vq); | |
267 | vdev->config->del_vq(vb->inflate_vq); | |
268 | kfree(vb); | |
269 | } | |
270 | ||
c45a6816 RR |
271 | static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST }; |
272 | ||
6b35e407 | 273 | static struct virtio_driver virtio_balloon = { |
c45a6816 RR |
274 | .feature_table = features, |
275 | .feature_table_size = ARRAY_SIZE(features), | |
6b35e407 RR |
276 | .driver.name = KBUILD_MODNAME, |
277 | .driver.owner = THIS_MODULE, | |
278 | .id_table = id_table, | |
279 | .probe = virtballoon_probe, | |
280 | .remove = __devexit_p(virtballoon_remove), | |
281 | .config_changed = virtballoon_changed, | |
282 | }; | |
283 | ||
284 | static int __init init(void) | |
285 | { | |
286 | return register_virtio_driver(&virtio_balloon); | |
287 | } | |
288 | ||
289 | static void __exit fini(void) | |
290 | { | |
291 | unregister_virtio_driver(&virtio_balloon); | |
292 | } | |
293 | module_init(init); | |
294 | module_exit(fini); | |
295 | ||
296 | MODULE_DEVICE_TABLE(virtio, id_table); | |
297 | MODULE_DESCRIPTION("Virtio balloon driver"); | |
298 | MODULE_LICENSE("GPL"); |