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