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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>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090027#include <linux/slab.h>
Rusty Russell6b35e402008-02-04 23:50:12 -050028
29struct virtio_balloon
30{
31 struct virtio_device *vdev;
Adam Litke9564e132009-11-30 10:14:15 -060032 struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
Rusty Russell6b35e402008-02-04 23:50:12 -050033
34 /* Where the ballooning thread waits for config to change. */
35 wait_queue_head_t config_change;
36
37 /* The thread servicing the balloon. */
38 struct task_struct *thread;
39
40 /* Waiting for host to ack the pages we released. */
41 struct completion acked;
42
Rusty Russell6b35e402008-02-04 23:50:12 -050043 /* The pages we've told the Host we're not using. */
44 unsigned int num_pages;
45 struct list_head pages;
46
47 /* The array of pfns we tell the Host about. */
48 unsigned int num_pfns;
49 u32 pfns[256];
Adam Litke9564e132009-11-30 10:14:15 -060050
51 /* Memory statistics */
Adam Litke1f34c712009-12-10 16:35:15 -060052 int need_stats_update;
Adam Litke9564e132009-11-30 10:14:15 -060053 struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
Rusty Russell6b35e402008-02-04 23:50:12 -050054};
55
56static struct virtio_device_id id_table[] = {
57 { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
58 { 0 },
59};
60
Hollis Blanchard1b4aa2f2008-11-13 15:48:33 -060061static u32 page_to_balloon_pfn(struct page *page)
62{
63 unsigned long pfn = page_to_pfn(page);
64
65 BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
66 /* Convert pfn from Linux page size to balloon page size. */
67 return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
68}
69
Rusty Russell6b35e402008-02-04 23:50:12 -050070static void balloon_ack(struct virtqueue *vq)
71{
72 struct virtio_balloon *vb;
73 unsigned int len;
74
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +030075 vb = virtqueue_get_buf(vq, &len);
Rusty Russell6b35e402008-02-04 23:50:12 -050076 if (vb)
77 complete(&vb->acked);
78}
79
80static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
81{
82 struct scatterlist sg;
83
84 sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
85
86 init_completion(&vb->acked);
87
88 /* We should always be able to add one buffer to an empty queue. */
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +030089 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0)
Rusty Russell6b35e402008-02-04 23:50:12 -050090 BUG();
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +030091 virtqueue_kick(vq);
Rusty Russell6b35e402008-02-04 23:50:12 -050092
93 /* When host has read buffer, this completes via balloon_ack */
94 wait_for_completion(&vb->acked);
95}
96
97static void fill_balloon(struct virtio_balloon *vb, size_t num)
98{
99 /* We can only do one array worth at a time. */
100 num = min(num, ARRAY_SIZE(vb->pfns));
101
102 for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
Balbir Singh61fb06c2010-04-22 12:22:34 +0930103 struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY |
104 __GFP_NOMEMALLOC | __GFP_NOWARN);
Rusty Russell6b35e402008-02-04 23:50:12 -0500105 if (!page) {
106 if (printk_ratelimit())
107 dev_printk(KERN_INFO, &vb->vdev->dev,
108 "Out of puff! Can't get %zu pages\n",
109 num);
110 /* Sleep for at least 1/5 of a second before retry. */
111 msleep(200);
112 break;
113 }
Hollis Blanchard1b4aa2f2008-11-13 15:48:33 -0600114 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
Rusty Russell6b35e402008-02-04 23:50:12 -0500115 totalram_pages--;
116 vb->num_pages++;
117 list_add(&page->lru, &vb->pages);
118 }
119
120 /* Didn't get any? Oh well. */
121 if (vb->num_pfns == 0)
122 return;
123
124 tell_host(vb, vb->inflate_vq);
125}
126
127static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
128{
129 unsigned int i;
130
131 for (i = 0; i < num; i++) {
132 __free_page(pfn_to_page(pfns[i]));
133 totalram_pages++;
134 }
135}
136
137static void leak_balloon(struct virtio_balloon *vb, size_t num)
138{
139 struct page *page;
140
141 /* We can only do one array worth at a time. */
142 num = min(num, ARRAY_SIZE(vb->pfns));
143
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);
Hollis Blanchard1b4aa2f2008-11-13 15:48:33 -0600147 vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
Rusty Russell6b35e402008-02-04 23:50:12 -0500148 vb->num_pages--;
149 }
150
Dave Hansenbf50e692011-04-07 10:43:25 -0700151
152 /*
153 * Note that if
154 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
155 * is true, we *have* to do it in this order
156 */
157 tell_host(vb, vb->deflate_vq);
158 release_pages_by_pfn(vb->pfns, vb->num_pfns);
Rusty Russell6b35e402008-02-04 23:50:12 -0500159}
160
Adam Litke9564e132009-11-30 10:14:15 -0600161static inline void update_stat(struct virtio_balloon *vb, int idx,
162 u16 tag, u64 val)
163{
164 BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
165 vb->stats[idx].tag = tag;
166 vb->stats[idx].val = val;
167}
168
169#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
170
171static void update_balloon_stats(struct virtio_balloon *vb)
172{
173 unsigned long events[NR_VM_EVENT_ITEMS];
174 struct sysinfo i;
175 int idx = 0;
176
177 all_vm_events(events);
178 si_meminfo(&i);
179
180 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
181 pages_to_bytes(events[PSWPIN]));
182 update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
183 pages_to_bytes(events[PSWPOUT]));
184 update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
185 update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
186 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
187 pages_to_bytes(i.freeram));
188 update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
189 pages_to_bytes(i.totalram));
190}
191
192/*
193 * While most virtqueues communicate guest-initiated requests to the hypervisor,
194 * the stats queue operates in reverse. The driver initializes the virtqueue
195 * with a single buffer. From that point forward, all conversations consist of
196 * a hypervisor request (a call to this function) which directs us to refill
Adam Litke1f34c712009-12-10 16:35:15 -0600197 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
198 * we notify our kthread which does the actual work via stats_handle_request().
Adam Litke9564e132009-11-30 10:14:15 -0600199 */
Adam Litke1f34c712009-12-10 16:35:15 -0600200static void stats_request(struct virtqueue *vq)
Adam Litke9564e132009-11-30 10:14:15 -0600201{
202 struct virtio_balloon *vb;
203 unsigned int len;
Adam Litke9564e132009-11-30 10:14:15 -0600204
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +0300205 vb = virtqueue_get_buf(vq, &len);
Adam Litke9564e132009-11-30 10:14:15 -0600206 if (!vb)
207 return;
Adam Litke1f34c712009-12-10 16:35:15 -0600208 vb->need_stats_update = 1;
209 wake_up(&vb->config_change);
210}
Adam Litke9564e132009-11-30 10:14:15 -0600211
Adam Litke1f34c712009-12-10 16:35:15 -0600212static void stats_handle_request(struct virtio_balloon *vb)
213{
214 struct virtqueue *vq;
215 struct scatterlist sg;
216
217 vb->need_stats_update = 0;
Adam Litke9564e132009-11-30 10:14:15 -0600218 update_balloon_stats(vb);
219
Adam Litke1f34c712009-12-10 16:35:15 -0600220 vq = vb->stats_vq;
Adam Litke9564e132009-11-30 10:14:15 -0600221 sg_init_one(&sg, vb->stats, sizeof(vb->stats));
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +0300222 if (virtqueue_add_buf(vq, &sg, 1, 0, vb) < 0)
Adam Litke9564e132009-11-30 10:14:15 -0600223 BUG();
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +0300224 virtqueue_kick(vq);
Adam Litke9564e132009-11-30 10:14:15 -0600225}
226
Rusty Russell6b35e402008-02-04 23:50:12 -0500227static void virtballoon_changed(struct virtio_device *vdev)
228{
229 struct virtio_balloon *vb = vdev->priv;
230
231 wake_up(&vb->config_change);
232}
233
Rusty Russellbdc16812008-03-17 22:58:15 -0500234static inline s64 towards_target(struct virtio_balloon *vb)
Rusty Russell6b35e402008-02-04 23:50:12 -0500235{
236 u32 v;
Rusty Russell72e61eb2008-05-02 21:50:49 -0500237 vb->vdev->config->get(vb->vdev,
238 offsetof(struct virtio_balloon_config, num_pages),
239 &v, sizeof(v));
Anthony Liguori532a6082008-08-18 17:15:31 -0500240 return (s64)v - vb->num_pages;
Rusty Russell6b35e402008-02-04 23:50:12 -0500241}
242
243static void update_balloon_size(struct virtio_balloon *vb)
244{
245 __le32 actual = cpu_to_le32(vb->num_pages);
246
247 vb->vdev->config->set(vb->vdev,
248 offsetof(struct virtio_balloon_config, actual),
249 &actual, sizeof(actual));
250}
251
252static int balloon(void *_vballoon)
253{
254 struct virtio_balloon *vb = _vballoon;
255
256 set_freezable();
257 while (!kthread_should_stop()) {
Rusty Russellbdc16812008-03-17 22:58:15 -0500258 s64 diff;
Rusty Russell6b35e402008-02-04 23:50:12 -0500259
260 try_to_freeze();
261 wait_event_interruptible(vb->config_change,
262 (diff = towards_target(vb)) != 0
Adam Litke1f34c712009-12-10 16:35:15 -0600263 || vb->need_stats_update
Marcelo Tosatti84a139a2009-04-16 21:14:04 -0300264 || kthread_should_stop()
265 || freezing(current));
Adam Litke1f34c712009-12-10 16:35:15 -0600266 if (vb->need_stats_update)
267 stats_handle_request(vb);
Rusty Russell6b35e402008-02-04 23:50:12 -0500268 if (diff > 0)
269 fill_balloon(vb, diff);
270 else if (diff < 0)
271 leak_balloon(vb, -diff);
272 update_balloon_size(vb);
273 }
274 return 0;
275}
276
277static int virtballoon_probe(struct virtio_device *vdev)
278{
279 struct virtio_balloon *vb;
Adam Litke9564e132009-11-30 10:14:15 -0600280 struct virtqueue *vqs[3];
Adam Litke1f34c712009-12-10 16:35:15 -0600281 vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
Adam Litke9564e132009-11-30 10:14:15 -0600282 const char *names[] = { "inflate", "deflate", "stats" };
283 int err, nvqs;
Rusty Russell6b35e402008-02-04 23:50:12 -0500284
285 vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
286 if (!vb) {
287 err = -ENOMEM;
288 goto out;
289 }
290
291 INIT_LIST_HEAD(&vb->pages);
292 vb->num_pages = 0;
293 init_waitqueue_head(&vb->config_change);
294 vb->vdev = vdev;
Rusty Russell169c2462010-02-24 14:22:14 -0600295 vb->need_stats_update = 0;
Rusty Russell6b35e402008-02-04 23:50:12 -0500296
Adam Litke9564e132009-11-30 10:14:15 -0600297 /* We expect two virtqueues: inflate and deflate,
298 * and optionally stat. */
299 nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
300 err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600301 if (err)
Rusty Russell6b35e402008-02-04 23:50:12 -0500302 goto out_free_vb;
Rusty Russell6b35e402008-02-04 23:50:12 -0500303
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600304 vb->inflate_vq = vqs[0];
305 vb->deflate_vq = vqs[1];
Adam Litke9564e132009-11-30 10:14:15 -0600306 if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
307 struct scatterlist sg;
308 vb->stats_vq = vqs[2];
309
310 /*
311 * Prime this virtqueue with one buffer so the hypervisor can
312 * use it to signal us later.
313 */
314 sg_init_one(&sg, vb->stats, sizeof vb->stats);
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +0300315 if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb) < 0)
Adam Litke9564e132009-11-30 10:14:15 -0600316 BUG();
Michael S. Tsirkin946cfe02010-04-12 16:18:28 +0300317 virtqueue_kick(vb->stats_vq);
Adam Litke9564e132009-11-30 10:14:15 -0600318 }
Rusty Russell6b35e402008-02-04 23:50:12 -0500319
320 vb->thread = kthread_run(balloon, vb, "vballoon");
321 if (IS_ERR(vb->thread)) {
322 err = PTR_ERR(vb->thread);
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600323 goto out_del_vqs;
Rusty Russell6b35e402008-02-04 23:50:12 -0500324 }
325
Rusty Russell6b35e402008-02-04 23:50:12 -0500326 return 0;
327
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600328out_del_vqs:
329 vdev->config->del_vqs(vdev);
Rusty Russell6b35e402008-02-04 23:50:12 -0500330out_free_vb:
331 kfree(vb);
332out:
333 return err;
334}
335
Uwe Kleine-König1e651752009-10-01 10:28:33 +0200336static void __devexit virtballoon_remove(struct virtio_device *vdev)
Rusty Russell6b35e402008-02-04 23:50:12 -0500337{
338 struct virtio_balloon *vb = vdev->priv;
339
340 kthread_stop(vb->thread);
341
342 /* There might be pages left in the balloon: free them. */
343 while (vb->num_pages)
344 leak_balloon(vb, vb->num_pages);
345
346 /* Now we reset the device so we can clean up the queues. */
347 vdev->config->reset(vdev);
348
Michael S. Tsirkind2a7ddd2009-06-12 22:16:36 -0600349 vdev->config->del_vqs(vdev);
Rusty Russell6b35e402008-02-04 23:50:12 -0500350 kfree(vb);
351}
352
Adam Litke9564e132009-11-30 10:14:15 -0600353static unsigned int features[] = {
354 VIRTIO_BALLOON_F_MUST_TELL_HOST,
355 VIRTIO_BALLOON_F_STATS_VQ,
356};
Rusty Russellc45a6812008-05-02 21:50:50 -0500357
Jeff Mahoneyd817cd52010-01-15 17:01:26 -0800358static struct virtio_driver virtio_balloon_driver = {
Rusty Russellc45a6812008-05-02 21:50:50 -0500359 .feature_table = features,
360 .feature_table_size = ARRAY_SIZE(features),
Rusty Russell6b35e402008-02-04 23:50:12 -0500361 .driver.name = KBUILD_MODNAME,
362 .driver.owner = THIS_MODULE,
363 .id_table = id_table,
364 .probe = virtballoon_probe,
365 .remove = __devexit_p(virtballoon_remove),
366 .config_changed = virtballoon_changed,
367};
368
369static int __init init(void)
370{
Jeff Mahoneyd817cd52010-01-15 17:01:26 -0800371 return register_virtio_driver(&virtio_balloon_driver);
Rusty Russell6b35e402008-02-04 23:50:12 -0500372}
373
374static void __exit fini(void)
375{
Jeff Mahoneyd817cd52010-01-15 17:01:26 -0800376 unregister_virtio_driver(&virtio_balloon_driver);
Rusty Russell6b35e402008-02-04 23:50:12 -0500377}
378module_init(init);
379module_exit(fini);
380
381MODULE_DEVICE_TABLE(virtio, id_table);
382MODULE_DESCRIPTION("Virtio balloon driver");
383MODULE_LICENSE("GPL");