aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/virtio/virtio_balloon.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/virtio/virtio_balloon.c')
-rw-r--r--drivers/virtio/virtio_balloon.c284
1 files changed, 284 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
new file mode 100644
index 000000000000..622aece1acce
--- /dev/null
+++ b/drivers/virtio/virtio_balloon.c
@@ -0,0 +1,284 @@
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
27struct virtio_balloon
28{
29 struct virtio_device *vdev;
30 struct virtqueue *inflate_vq, *deflate_vq;
31
32 /* Where the ballooning thread waits for config to change. */
33 wait_queue_head_t config_change;
34
35 /* The thread servicing the balloon. */
36 struct task_struct *thread;
37
38 /* Waiting for host to ack the pages we released. */
39 struct completion acked;
40
41 /* Do we have to tell Host *before* we reuse pages? */
42 bool tell_host_first;
43
44 /* The pages we've told the Host we're not using. */
45 unsigned int num_pages;
46 struct list_head pages;
47
48 /* The array of pfns we tell the Host about. */
49 unsigned int num_pfns;
50 u32 pfns[256];
51};
52
53static struct virtio_device_id id_table[] = {
54 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
55 { 0 },
56};
57
58static void balloon_ack(struct virtqueue *vq)
59{
60 struct virtio_balloon *vb;
61 unsigned int len;
62
63 vb = vq->vq_ops->get_buf(vq, &len);
64 if (vb)
65 complete(&vb->acked);
66}
67
68static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
69{
70 struct scatterlist sg;
71
72 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
73
74 init_completion(&vb->acked);
75
76 /* We should always be able to add one buffer to an empty queue. */
77 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0)
78 BUG();
79 vq->vq_ops->kick(vq);
80
81 /* When host has read buffer, this completes via balloon_ack */
82 wait_for_completion(&vb->acked);
83}
84
85static void fill_balloon(struct virtio_balloon *vb, size_t num)
86{
87 /* We can only do one array worth at a time. */
88 num = min(num, ARRAY_SIZE(vb->pfns));
89
90 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
91 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY);
92 if (!page) {
93 if (printk_ratelimit())
94 dev_printk(KERN_INFO, &vb->vdev->dev,
95 "Out of puff! Can't get %zu pages\n",
96 num);
97 /* Sleep for at least 1/5 of a second before retry. */
98 msleep(200);
99 break;
100 }
101 vb->pfns[vb->num_pfns] = page_to_pfn(page);
102 totalram_pages--;
103 vb->num_pages++;
104 list_add(&page->lru, &vb->pages);
105 }
106
107 /* Didn't get any? Oh well. */
108 if (vb->num_pfns == 0)
109 return;
110
111 tell_host(vb, vb->inflate_vq);
112}
113
114static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
115{
116 unsigned int i;
117
118 for (i = 0; i < num; i++) {
119 __free_page(pfn_to_page(pfns[i]));
120 totalram_pages++;
121 }
122}
123
124static void leak_balloon(struct virtio_balloon *vb, size_t num)
125{
126 struct page *page;
127
128 /* We can only do one array worth at a time. */
129 num = min(num, ARRAY_SIZE(vb->pfns));
130
131 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
132 page = list_first_entry(&vb->pages, struct page, lru);
133 list_del(&page->lru);
134 vb->pfns[vb->num_pfns] = page_to_pfn(page);
135 vb->num_pages--;
136 }
137
138 if (vb->tell_host_first) {
139 tell_host(vb, vb->deflate_vq);
140 release_pages_by_pfn(vb->pfns, vb->num_pfns);
141 } else {
142 release_pages_by_pfn(vb->pfns, vb->num_pfns);
143 tell_host(vb, vb->deflate_vq);
144 }
145}
146
147static void virtballoon_changed(struct virtio_device *vdev)
148{
149 struct virtio_balloon *vb = vdev->priv;
150
151 wake_up(&vb->config_change);
152}
153
154static inline int towards_target(struct virtio_balloon *vb)
155{
156 u32 v;
157 __virtio_config_val(vb->vdev,
158 offsetof(struct virtio_balloon_config, num_pages),
159 &v);
160 return v - vb->num_pages;
161}
162
163static void update_balloon_size(struct virtio_balloon *vb)
164{
165 __le32 actual = cpu_to_le32(vb->num_pages);
166
167 vb->vdev->config->set(vb->vdev,
168 offsetof(struct virtio_balloon_config, actual),
169 &actual, sizeof(actual));
170}
171
172static int balloon(void *_vballoon)
173{
174 struct virtio_balloon *vb = _vballoon;
175
176 set_freezable();
177 while (!kthread_should_stop()) {
178 int diff;
179
180 try_to_freeze();
181 wait_event_interruptible(vb->config_change,
182 (diff = towards_target(vb)) != 0
183 || kthread_should_stop());
184 if (diff > 0)
185 fill_balloon(vb, diff);
186 else if (diff < 0)
187 leak_balloon(vb, -diff);
188 update_balloon_size(vb);
189 }
190 return 0;
191}
192
193static int virtballoon_probe(struct virtio_device *vdev)
194{
195 struct virtio_balloon *vb;
196 int err;
197
198 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
199 if (!vb) {
200 err = -ENOMEM;
201 goto out;
202 }
203
204 INIT_LIST_HEAD(&vb->pages);
205 vb->num_pages = 0;
206 init_waitqueue_head(&vb->config_change);
207 vb->vdev = vdev;
208
209 /* We expect two virtqueues. */
210 vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack);
211 if (IS_ERR(vb->inflate_vq)) {
212 err = PTR_ERR(vb->inflate_vq);
213 goto out_free_vb;
214 }
215
216 vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack);
217 if (IS_ERR(vb->deflate_vq)) {
218 err = PTR_ERR(vb->deflate_vq);
219 goto out_del_inflate_vq;
220 }
221
222 vb->thread = kthread_run(balloon, vb, "vballoon");
223 if (IS_ERR(vb->thread)) {
224 err = PTR_ERR(vb->thread);
225 goto out_del_deflate_vq;
226 }
227
228 vb->tell_host_first
229 = vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
230
231 return 0;
232
233out_del_deflate_vq:
234 vdev->config->del_vq(vb->deflate_vq);
235out_del_inflate_vq:
236 vdev->config->del_vq(vb->inflate_vq);
237out_free_vb:
238 kfree(vb);
239out:
240 return err;
241}
242
243static void virtballoon_remove(struct virtio_device *vdev)
244{
245 struct virtio_balloon *vb = vdev->priv;
246
247 kthread_stop(vb->thread);
248
249 /* There might be pages left in the balloon: free them. */
250 while (vb->num_pages)
251 leak_balloon(vb, vb->num_pages);
252
253 /* Now we reset the device so we can clean up the queues. */
254 vdev->config->reset(vdev);
255
256 vdev->config->del_vq(vb->deflate_vq);
257 vdev->config->del_vq(vb->inflate_vq);
258 kfree(vb);
259}
260
261static struct virtio_driver virtio_balloon = {
262 .driver.name = KBUILD_MODNAME,
263 .driver.owner = THIS_MODULE,
264 .id_table = id_table,
265 .probe = virtballoon_probe,
266 .remove = __devexit_p(virtballoon_remove),
267 .config_changed = virtballoon_changed,
268};
269
270static int __init init(void)
271{
272 return register_virtio_driver(&virtio_balloon);
273}
274
275static void __exit fini(void)
276{
277 unregister_virtio_driver(&virtio_balloon);
278}
279module_init(init);
280module_exit(fini);
281
282MODULE_DEVICE_TABLE(virtio, id_table);
283MODULE_DESCRIPTION("Virtio balloon driver");
284MODULE_LICENSE("GPL");