blob: 9dd5880428803d78a3ad349d43aae049dd4f4344 [file] [log] [blame]
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
Hollis Blanchard1b4aa2f2008-11-13 15:48:33 -060059static 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
Rusty Russell6b35e402008-02-04 23:50:12 -050068static 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
78static 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. */
Rusty Russell3c1b27d2009-09-23 22:26:31 -060087 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
Rusty Russell6b35e402008-02-04 23:50:12 -050088 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
95static 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 }
Hollis Blanchard1b4aa2f2008-11-13 15:48:33 -0600111 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
Rusty Russell6b35e402008-02-04 23:50:12 -0500112 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
124static 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
134static 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);
Hollis Blanchard1b4aa2f2008-11-13 15:48:33 -0600144 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
Rusty Russell6b35e402008-02-04 23:50:12 -0500145 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
157static void virtballoon_changed(struct virtio_device *vdev)
158{
159 struct virtio_balloon *vb = vdev->priv;
160
161 wake_up(&vb->config_change);
162}
163
Rusty Russellbdc16812008-03-17 22:58:15 -0500164static inline s64 towards_target(struct virtio_balloon *vb)
Rusty Russell6b35e402008-02-04 23:50:12 -0500165{
166 u32 v;
Rusty Russell72e61eb2008-05-02 21:50:49 -0500167 vb->vdev->config->get(vb->vdev,
168 offsetof(struct virtio_balloon_config, num_pages),
169 &v, sizeof(v));
Anthony Liguori532a6082008-08-18 17:15:31 -0500170 return (s64)v - vb->num_pages;
Rusty Russell6b35e402008-02-04 23:50:12 -0500171}
172
173static 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
182static int balloon(void *_vballoon)
183{
184 struct virtio_balloon *vb = _vballoon;
185
186 set_freezable();
187 while (!kthread_should_stop()) {
Rusty Russellbdc16812008-03-17 22:58:15 -0500188 s64 diff;
Rusty Russell6b35e402008-02-04 23:50:12 -0500189
190 try_to_freeze();
191 wait_event_interruptible(vb->config_change,
192 (diff = towards_target(vb)) != 0
Marcelo Tosatti84a139a2009-04-16 21:14:04 -0300193 || kthread_should_stop()
194 || freezing(current));
Rusty Russell6b35e402008-02-04 23:50:12 -0500195 if (diff > 0)
196 fill_balloon(vb, diff);
197 else if (diff < 0)
198 leak_balloon(vb, -diff);
199 update_balloon_size(vb);
200 }
201 return 0;
202}
203
204static int virtballoon_probe(struct virtio_device *vdev)
205{
206 struct virtio_balloon *vb;
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600207 struct virtqueue *vqs[2];
208 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack };
209 const char *names[] = { "inflate", "deflate" };
Rusty Russell6b35e402008-02-04 23:50:12 -0500210 int err;
211
212 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
213 if (!vb) {
214 err = -ENOMEM;
215 goto out;
216 }
217
218 INIT_LIST_HEAD(&vb->pages);
219 vb->num_pages = 0;
220 init_waitqueue_head(&vb->config_change);
221 vb->vdev = vdev;
222
223 /* We expect two virtqueues. */
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600224 err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
225 if (err)
Rusty Russell6b35e402008-02-04 23:50:12 -0500226 goto out_free_vb;
Rusty Russell6b35e402008-02-04 23:50:12 -0500227
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600228 vb->inflate_vq = vqs[0];
229 vb->deflate_vq = vqs[1];
Rusty Russell6b35e402008-02-04 23:50:12 -0500230
231 vb->thread = kthread_run(balloon, vb, "vballoon");
232 if (IS_ERR(vb->thread)) {
233 err = PTR_ERR(vb->thread);
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600234 goto out_del_vqs;
Rusty Russell6b35e402008-02-04 23:50:12 -0500235 }
236
237 vb->tell_host_first
Rusty Russellc45a6812008-05-02 21:50:50 -0500238 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
Rusty Russell6b35e402008-02-04 23:50:12 -0500239
240 return 0;
241
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600242out_del_vqs:
243 vdev->config->del_vqs(vdev);
Rusty Russell6b35e402008-02-04 23:50:12 -0500244out_free_vb:
245 kfree(vb);
246out:
247 return err;
248}
249
Uwe Kleine-König1e651752009-10-01 10:28:33 +0200250static void __devexit virtballoon_remove(struct virtio_device *vdev)
Rusty Russell6b35e402008-02-04 23:50:12 -0500251{
252 struct virtio_balloon *vb = vdev->priv;
253
254 kthread_stop(vb->thread);
255
256 /* There might be pages left in the balloon: free them. */
257 while (vb->num_pages)
258 leak_balloon(vb, vb->num_pages);
259
260 /* Now we reset the device so we can clean up the queues. */
261 vdev->config->reset(vdev);
262
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600263 vdev->config->del_vqs(vdev);
Rusty Russell6b35e402008-02-04 23:50:12 -0500264 kfree(vb);
265}
266
Rusty Russellc45a6812008-05-02 21:50:50 -0500267static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };
268
Rusty Russell6b35e402008-02-04 23:50:12 -0500269static struct virtio_driver virtio_balloon = {
Rusty Russellc45a6812008-05-02 21:50:50 -0500270 .feature_table = features,
271 .feature_table_size = ARRAY_SIZE(features),
Rusty Russell6b35e402008-02-04 23:50:12 -0500272 .driver.name = KBUILD_MODNAME,
273 .driver.owner = THIS_MODULE,
274 .id_table = id_table,
275 .probe = virtballoon_probe,
276 .remove = __devexit_p(virtballoon_remove),
277 .config_changed = virtballoon_changed,
278};
279
280static int __init init(void)
281{
282 return register_virtio_driver(&virtio_balloon);
283}
284
285static void __exit fini(void)
286{
287 unregister_virtio_driver(&virtio_balloon);
288}
289module_init(init);
290module_exit(fini);
291
292MODULE_DEVICE_TABLE(virtio, id_table);
293MODULE_DESCRIPTION("Virtio balloon driver");
294MODULE_LICENSE("GPL");