blob: 59268266b79a5b7c6b439c6e9b210bb25c4236a3 [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. */
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
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
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
203static 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
Rusty Russellc45a6812008-05-02 21:50:50 -0500239 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
Rusty Russell6b35e402008-02-04 23:50:12 -0500240
241 return 0;
242
243out_del_deflate_vq:
244 vdev->config->del_vq(vb->deflate_vq);
245out_del_inflate_vq:
246 vdev->config->del_vq(vb->inflate_vq);
247out_free_vb:
248 kfree(vb);
249out:
250 return err;
251}
252
253static 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
Rusty Russellc45a6812008-05-02 21:50:50 -0500271static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };
272
Rusty Russell6b35e402008-02-04 23:50:12 -0500273static struct virtio_driver virtio_balloon = {
Rusty Russellc45a6812008-05-02 21:50:50 -0500274 .feature_table = features,
275 .feature_table_size = ARRAY_SIZE(features),
Rusty Russell6b35e402008-02-04 23:50:12 -0500276 .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
284static int __init init(void)
285{
286 return register_virtio_driver(&virtio_balloon);
287}
288
289static void __exit fini(void)
290{
291 unregister_virtio_driver(&virtio_balloon);
292}
293module_init(init);
294module_exit(fini);
295
296MODULE_DEVICE_TABLE(virtio, id_table);
297MODULE_DESCRIPTION("Virtio balloon driver");
298MODULE_LICENSE("GPL");