1 /* Virtio balloon implementation, inspired by Dor Loar and Marcelo
2 * Tosatti's implementations.
4 * Copyright 2008 Rusty Russell IBM Corporation
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.
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.
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
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 #include <linux/delay.h>
30 struct virtio_device *vdev;
31 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
33 /* Where the ballooning thread waits for config to change. */
34 wait_queue_head_t config_change;
36 /* The thread servicing the balloon. */
37 struct task_struct *thread;
39 /* Waiting for host to ack the pages we released. */
40 struct completion acked;
42 /* Do we have to tell Host *before* we reuse pages? */
45 /* The pages we've told the Host we're not using. */
46 unsigned int num_pages;
47 struct list_head pages;
49 /* The array of pfns we tell the Host about. */
50 unsigned int num_pfns;
53 /* Memory statistics */
54 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
57 static struct virtio_device_id id_table[] = {
58 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
62 static u32 page_to_balloon_pfn(struct page *page)
64 unsigned long pfn = page_to_pfn(page);
66 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
67 /* Convert pfn from Linux page size to balloon page size. */
68 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
71 static void balloon_ack(struct virtqueue *vq)
73 struct virtio_balloon *vb;
76 vb = vq->vq_ops->get_buf(vq, &len);
81 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
83 struct scatterlist sg;
85 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
87 init_completion(&vb->acked);
89 /* We should always be able to add one buffer to an empty queue. */
90 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
94 /* When host has read buffer, this completes via balloon_ack */
95 wait_for_completion(&vb->acked);
98 static void fill_balloon(struct virtio_balloon *vb, size_t num)
100 /* We can only do one array worth at a time. */
101 num = min(num, ARRAY_SIZE(vb->pfns));
103 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
104 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY);
106 if (printk_ratelimit())
107 dev_printk(KERN_INFO, &vb->vdev->dev,
108 "Out of puff! Can't get %zu pages\n",
110 /* Sleep for at least 1/5 of a second before retry. */
114 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
117 list_add(&page->lru, &vb->pages);
120 /* Didn't get any? Oh well. */
121 if (vb->num_pfns == 0)
124 tell_host(vb, vb->inflate_vq);
127 static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
131 for (i = 0; i < num; i++) {
132 __free_page(pfn_to_page(pfns[i]));
137 static void leak_balloon(struct virtio_balloon *vb, size_t num)
141 /* We can only do one array worth at a time. */
142 num = min(num, ARRAY_SIZE(vb->pfns));
144 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
145 page = list_first_entry(&vb->pages, struct page, lru);
146 list_del(&page->lru);
147 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
151 if (vb->tell_host_first) {
152 tell_host(vb, vb->deflate_vq);
153 release_pages_by_pfn(vb->pfns, vb->num_pfns);
155 release_pages_by_pfn(vb->pfns, vb->num_pfns);
156 tell_host(vb, vb->deflate_vq);
160 static inline void update_stat(struct virtio_balloon *vb, int idx,
163 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
164 vb->stats[idx].tag = tag;
165 vb->stats[idx].val = val;
168 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
170 static void update_balloon_stats(struct virtio_balloon *vb)
172 unsigned long events[NR_VM_EVENT_ITEMS];
176 all_vm_events(events);
179 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
180 pages_to_bytes(events[PSWPIN]));
181 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
182 pages_to_bytes(events[PSWPOUT]));
183 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
184 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
185 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
186 pages_to_bytes(i.freeram));
187 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
188 pages_to_bytes(i.totalram));
192 * While most virtqueues communicate guest-initiated requests to the hypervisor,
193 * the stats queue operates in reverse. The driver initializes the virtqueue
194 * with a single buffer. From that point forward, all conversations consist of
195 * a hypervisor request (a call to this function) which directs us to refill
196 * the virtqueue with a fresh stats buffer.
198 static void stats_ack(struct virtqueue *vq)
200 struct virtio_balloon *vb;
202 struct scatterlist sg;
204 vb = vq->vq_ops->get_buf(vq, &len);
208 update_balloon_stats(vb);
210 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
211 if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
213 vq->vq_ops->kick(vq);
216 static void virtballoon_changed(struct virtio_device *vdev)
218 struct virtio_balloon *vb = vdev->priv;
220 wake_up(&vb->config_change);
223 static inline s64 towards_target(struct virtio_balloon *vb)
226 vb->vdev->config->get(vb->vdev,
227 offsetof(struct virtio_balloon_config, num_pages),
229 return (s64)v - vb->num_pages;
232 static void update_balloon_size(struct virtio_balloon *vb)
234 __le32 actual = cpu_to_le32(vb->num_pages);
236 vb->vdev->config->set(vb->vdev,
237 offsetof(struct virtio_balloon_config, actual),
238 &actual, sizeof(actual));
241 static int balloon(void *_vballoon)
243 struct virtio_balloon *vb = _vballoon;
246 while (!kthread_should_stop()) {
250 wait_event_interruptible(vb->config_change,
251 (diff = towards_target(vb)) != 0
252 || kthread_should_stop()
253 || freezing(current));
255 fill_balloon(vb, diff);
257 leak_balloon(vb, -diff);
258 update_balloon_size(vb);
263 static int virtballoon_probe(struct virtio_device *vdev)
265 struct virtio_balloon *vb;
266 struct virtqueue *vqs[3];
267 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_ack };
268 const char *names[] = { "inflate", "deflate", "stats" };
271 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
277 INIT_LIST_HEAD(&vb->pages);
279 init_waitqueue_head(&vb->config_change);
282 /* We expect two virtqueues: inflate and deflate,
283 * and optionally stat. */
284 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
285 err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
289 vb->inflate_vq = vqs[0];
290 vb->deflate_vq = vqs[1];
291 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
292 struct scatterlist sg;
293 vb->stats_vq = vqs[2];
296 * Prime this virtqueue with one buffer so the hypervisor can
297 * use it to signal us later.
299 sg_init_one(&sg, vb->stats, sizeof vb->stats);
300 if (vb->stats_vq->vq_ops->add_buf(vb->stats_vq,
303 vb->stats_vq->vq_ops->kick(vb->stats_vq);
306 vb->thread = kthread_run(balloon, vb, "vballoon");
307 if (IS_ERR(vb->thread)) {
308 err = PTR_ERR(vb->thread);
313 = virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
318 vdev->config->del_vqs(vdev);
325 static void __devexit virtballoon_remove(struct virtio_device *vdev)
327 struct virtio_balloon *vb = vdev->priv;
329 kthread_stop(vb->thread);
331 /* There might be pages left in the balloon: free them. */
332 while (vb->num_pages)
333 leak_balloon(vb, vb->num_pages);
335 /* Now we reset the device so we can clean up the queues. */
336 vdev->config->reset(vdev);
338 vdev->config->del_vqs(vdev);
342 static unsigned int features[] = {
343 VIRTIO_BALLOON_F_MUST_TELL_HOST,
344 VIRTIO_BALLOON_F_STATS_VQ,
347 static struct virtio_driver virtio_balloon_driver = {
348 .feature_table = features,
349 .feature_table_size = ARRAY_SIZE(features),
350 .driver.name = KBUILD_MODNAME,
351 .driver.owner = THIS_MODULE,
352 .id_table = id_table,
353 .probe = virtballoon_probe,
354 .remove = __devexit_p(virtballoon_remove),
355 .config_changed = virtballoon_changed,
358 static int __init init(void)
360 return register_virtio_driver(&virtio_balloon_driver);
363 static void __exit fini(void)
365 unregister_virtio_driver(&virtio_balloon_driver);
370 MODULE_DEVICE_TABLE(virtio, id_table);
371 MODULE_DESCRIPTION("Virtio balloon driver");
372 MODULE_LICENSE("GPL");