2 * Virtio balloon implementation, inspired by Dor Laor and Marcelo
3 * Tosatti's implementations.
5 * Copyright 2008 Rusty Russell IBM Corporation
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 #include <linux/virtio.h>
23 #include <linux/virtio_balloon.h>
24 #include <linux/swap.h>
25 #include <linux/kthread.h>
26 #include <linux/freezer.h>
27 #include <linux/delay.h>
28 #include <linux/slab.h>
29 #include <linux/module.h>
33 struct virtio_device *vdev;
34 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
36 /* Where the ballooning thread waits for config to change. */
37 wait_queue_head_t config_change;
39 /* The thread servicing the balloon. */
40 struct task_struct *thread;
42 /* Waiting for host to ack the pages we released. */
43 struct completion acked;
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 int need_stats_update;
55 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
58 static struct virtio_device_id id_table[] = {
59 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
63 static u32 page_to_balloon_pfn(struct page *page)
65 unsigned long pfn = page_to_pfn(page);
67 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
68 /* Convert pfn from Linux page size to balloon page size. */
69 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
72 static void balloon_ack(struct virtqueue *vq)
74 struct virtio_balloon *vb;
77 vb = virtqueue_get_buf(vq, &len);
82 static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
84 struct scatterlist sg;
86 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
88 init_completion(&vb->acked);
90 /* We should always be able to add one buffer to an empty queue. */
91 if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
95 /* When host has read buffer, this completes via balloon_ack */
96 wait_for_completion(&vb->acked);
99 static void fill_balloon(struct virtio_balloon *vb, size_t num)
101 /* We can only do one array worth at a time. */
102 num = min(num, ARRAY_SIZE(vb->pfns));
104 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
105 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
106 __GFP_NOMEMALLOC | __GFP_NOWARN);
108 if (printk_ratelimit())
109 dev_printk(KERN_INFO, &vb->vdev->dev,
110 "Out of puff! Can't get %zu pages\n",
112 /* Sleep for at least 1/5 of a second before retry. */
116 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
119 list_add(&page->lru, &vb->pages);
122 /* Didn't get any? Oh well. */
123 if (vb->num_pfns == 0)
126 tell_host(vb, vb->inflate_vq);
129 static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
133 for (i = 0; i < num; i++) {
134 __free_page(pfn_to_page(pfns[i]));
139 static void leak_balloon(struct virtio_balloon *vb, size_t num)
143 /* We can only do one array worth at a time. */
144 num = min(num, ARRAY_SIZE(vb->pfns));
146 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
147 page = list_first_entry(&vb->pages, struct page, lru);
148 list_del(&page->lru);
149 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
155 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
156 * is true, we *have* to do it in this order
158 tell_host(vb, vb->deflate_vq);
159 release_pages_by_pfn(vb->pfns, vb->num_pfns);
162 static inline void update_stat(struct virtio_balloon *vb, int idx,
165 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
166 vb->stats[idx].tag = tag;
167 vb->stats[idx].val = val;
170 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
172 static void update_balloon_stats(struct virtio_balloon *vb)
174 unsigned long events[NR_VM_EVENT_ITEMS];
178 all_vm_events(events);
181 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
182 pages_to_bytes(events[PSWPIN]));
183 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
184 pages_to_bytes(events[PSWPOUT]));
185 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
186 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
187 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
188 pages_to_bytes(i.freeram));
189 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
190 pages_to_bytes(i.totalram));
194 * While most virtqueues communicate guest-initiated requests to the hypervisor,
195 * the stats queue operates in reverse. The driver initializes the virtqueue
196 * with a single buffer. From that point forward, all conversations consist of
197 * a hypervisor request (a call to this function) which directs us to refill
198 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
199 * we notify our kthread which does the actual work via stats_handle_request().
201 static void stats_request(struct virtqueue *vq)
203 struct virtio_balloon *vb;
206 vb = virtqueue_get_buf(vq, &len);
209 vb->need_stats_update = 1;
210 wake_up(&vb->config_change);
213 static void stats_handle_request(struct virtio_balloon *vb)
215 struct virtqueue *vq;
216 struct scatterlist sg;
218 vb->need_stats_update = 0;
219 update_balloon_stats(vb);
222 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
223 if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
228 static void virtballoon_changed(struct virtio_device *vdev)
230 struct virtio_balloon *vb = vdev->priv;
232 wake_up(&vb->config_change);
235 static inline s64 towards_target(struct virtio_balloon *vb)
238 vb->vdev->config->get(vb->vdev,
239 offsetof(struct virtio_balloon_config, num_pages),
241 return (s64)v - vb->num_pages;
244 static void update_balloon_size(struct virtio_balloon *vb)
246 __le32 actual = cpu_to_le32(vb->num_pages);
248 vb->vdev->config->set(vb->vdev,
249 offsetof(struct virtio_balloon_config, actual),
250 &actual, sizeof(actual));
253 static int balloon(void *_vballoon)
255 struct virtio_balloon *vb = _vballoon;
258 while (!kthread_should_stop()) {
262 wait_event_interruptible(vb->config_change,
263 (diff = towards_target(vb)) != 0
264 || vb->need_stats_update
265 || kthread_should_stop()
266 || freezing(current));
267 if (vb->need_stats_update)
268 stats_handle_request(vb);
270 fill_balloon(vb, diff);
272 leak_balloon(vb, -diff);
273 update_balloon_size(vb);
278 static int virtballoon_probe(struct virtio_device *vdev)
280 struct virtio_balloon *vb;
281 struct virtqueue *vqs[3];
282 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
283 const char *names[] = { "inflate", "deflate", "stats" };
286 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
292 INIT_LIST_HEAD(&vb->pages);
294 init_waitqueue_head(&vb->config_change);
296 vb->need_stats_update = 0;
298 /* We expect two virtqueues: inflate and deflate,
299 * and optionally stat. */
300 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
301 err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
305 vb->inflate_vq = vqs[0];
306 vb->deflate_vq = vqs[1];
307 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
308 struct scatterlist sg;
309 vb->stats_vq = vqs[2];
312 * Prime this virtqueue with one buffer so the hypervisor can
313 * use it to signal us later.
315 sg_init_one(&sg, vb->stats, sizeof vb->stats);
316 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL)
319 virtqueue_kick(vb->stats_vq);
322 vb->thread = kthread_run(balloon, vb, "vballoon");
323 if (IS_ERR(vb->thread)) {
324 err = PTR_ERR(vb->thread);
331 vdev->config->del_vqs(vdev);
338 static void __devexit virtballoon_remove(struct virtio_device *vdev)
340 struct virtio_balloon *vb = vdev->priv;
342 kthread_stop(vb->thread);
344 /* There might be pages left in the balloon: free them. */
345 while (vb->num_pages)
346 leak_balloon(vb, vb->num_pages);
348 /* Now we reset the device so we can clean up the queues. */
349 vdev->config->reset(vdev);
351 vdev->config->del_vqs(vdev);
355 static unsigned int features[] = {
356 VIRTIO_BALLOON_F_MUST_TELL_HOST,
357 VIRTIO_BALLOON_F_STATS_VQ,
360 static struct virtio_driver virtio_balloon_driver = {
361 .feature_table = features,
362 .feature_table_size = ARRAY_SIZE(features),
363 .driver.name = KBUILD_MODNAME,
364 .driver.owner = THIS_MODULE,
365 .id_table = id_table,
366 .probe = virtballoon_probe,
367 .remove = __devexit_p(virtballoon_remove),
368 .config_changed = virtballoon_changed,
371 static int __init init(void)
373 return register_virtio_driver(&virtio_balloon_driver);
376 static void __exit fini(void)
378 unregister_virtio_driver(&virtio_balloon_driver);
383 MODULE_DEVICE_TABLE(virtio, id_table);
384 MODULE_DESCRIPTION("Virtio balloon driver");
385 MODULE_LICENSE("GPL");