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Rusty Russell6b35e402008-02-04 23:50:12 -05001/* 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>
Johann Felix Soden6659a0f2008-02-06 01:40:22 -080026#include <linux/delay.h>
Rusty Russell6b35e402008-02-04 23:50:12 -050027
28struct 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
54static struct virtio_device_id id_table[] = {
55 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
56 { 0 },
57};
58
59static 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
69static 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
86static 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
115static 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
125static 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
148static void virtballoon_changed(struct virtio_device *vdev)
149{
150 struct virtio_balloon *vb = vdev->priv;
151
152 wake_up(&vb->config_change);
153}
154
Rusty Russellbdc16812008-03-17 22:58:15 -0500155static inline s64 towards_target(struct virtio_balloon *vb)
Rusty Russell6b35e402008-02-04 23:50:12 -0500156{
157 u32 v;
Rusty Russell72e61eb2008-05-02 21:50:49 -0500158 vb->vdev->config->get(vb->vdev,
159 offsetof(struct virtio_balloon_config, num_pages),
160 &v, sizeof(v));
Rusty Russell6b35e402008-02-04 23:50:12 -0500161 return v - vb->num_pages;
162}
163
164static 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
173static int balloon(void *_vballoon)
174{
175 struct virtio_balloon *vb = _vballoon;
176
177 set_freezable();
178 while (!kthread_should_stop()) {
Rusty Russellbdc16812008-03-17 22:58:15 -0500179 s64 diff;
Rusty Russell6b35e402008-02-04 23:50:12 -0500180
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
194static 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
Rusty Russellc45a6812008-05-02 21:50:50 -0500230 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
Rusty Russell6b35e402008-02-04 23:50:12 -0500231
232 return 0;
233
234out_del_deflate_vq:
235 vdev->config->del_vq(vb->deflate_vq);
236out_del_inflate_vq:
237 vdev->config->del_vq(vb->inflate_vq);
238out_free_vb:
239 kfree(vb);
240out:
241 return err;
242}
243
244static 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
Rusty Russellc45a6812008-05-02 21:50:50 -0500262static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };
263
Rusty Russell6b35e402008-02-04 23:50:12 -0500264static struct virtio_driver virtio_balloon = {
Rusty Russellc45a6812008-05-02 21:50:50 -0500265 .feature_table = features,
266 .feature_table_size = ARRAY_SIZE(features),
Rusty Russell6b35e402008-02-04 23:50:12 -0500267 .driver.name = KBUILD_MODNAME,
268 .driver.owner = THIS_MODULE,
269 .id_table = id_table,
270 .probe = virtballoon_probe,
271 .remove = __devexit_p(virtballoon_remove),
272 .config_changed = virtballoon_changed,
273};
274
275static int __init init(void)
276{
277 return register_virtio_driver(&virtio_balloon);
278}
279
280static void __exit fini(void)
281{
282 unregister_virtio_driver(&virtio_balloon);
283}
284module_init(init);
285module_exit(fini);
286
287MODULE_DEVICE_TABLE(virtio, id_table);
288MODULE_DESCRIPTION("Virtio balloon driver");
289MODULE_LICENSE("GPL");