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>
32 * Balloon device works in 4K page units. So each page is pointed to by
33 * multiple balloon pages. All memory counters in this driver are in balloon
36 #define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
40 struct virtio_device
*vdev
;
41 struct virtqueue
*inflate_vq
, *deflate_vq
, *stats_vq
;
43 /* Where the ballooning thread waits for config to change. */
44 wait_queue_head_t config_change
;
46 /* The thread servicing the balloon. */
47 struct task_struct
*thread
;
49 /* Waiting for host to ack the pages we released. */
50 struct completion acked
;
52 /* Number of balloon pages we've told the Host we're not using. */
53 unsigned int num_pages
;
55 * The pages we've told the Host we're not using.
56 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
59 struct list_head pages
;
61 /* The array of pfns we tell the Host about. */
62 unsigned int num_pfns
;
65 /* Memory statistics */
66 int need_stats_update
;
67 struct virtio_balloon_stat stats
[VIRTIO_BALLOON_S_NR
];
70 static struct virtio_device_id id_table
[] = {
71 { VIRTIO_ID_BALLOON
, VIRTIO_DEV_ANY_ID
},
75 static u32
page_to_balloon_pfn(struct page
*page
)
77 unsigned long pfn
= page_to_pfn(page
);
79 BUILD_BUG_ON(PAGE_SHIFT
< VIRTIO_BALLOON_PFN_SHIFT
);
80 /* Convert pfn from Linux page size to balloon page size. */
81 return pfn
* VIRTIO_BALLOON_PAGES_PER_PAGE
;
84 static struct page
*balloon_pfn_to_page(u32 pfn
)
86 BUG_ON(pfn
% VIRTIO_BALLOON_PAGES_PER_PAGE
);
87 return pfn_to_page(pfn
/ VIRTIO_BALLOON_PAGES_PER_PAGE
);
90 static void balloon_ack(struct virtqueue
*vq
)
92 struct virtio_balloon
*vb
;
95 vb
= virtqueue_get_buf(vq
, &len
);
100 static void tell_host(struct virtio_balloon
*vb
, struct virtqueue
*vq
)
102 struct scatterlist sg
;
104 sg_init_one(&sg
, vb
->pfns
, sizeof(vb
->pfns
[0]) * vb
->num_pfns
);
106 init_completion(&vb
->acked
);
108 /* We should always be able to add one buffer to an empty queue. */
109 if (virtqueue_add_buf(vq
, &sg
, 1, 0, vb
, GFP_KERNEL
) < 0)
113 /* When host has read buffer, this completes via balloon_ack */
114 wait_for_completion(&vb
->acked
);
117 static void set_page_pfns(u32 pfns
[], struct page
*page
)
121 /* Set balloon pfns pointing at this page.
122 * Note that the first pfn points at start of the page. */
123 for (i
= 0; i
< VIRTIO_BALLOON_PAGES_PER_PAGE
; i
++)
124 pfns
[i
] = page_to_balloon_pfn(page
) + i
;
127 static void fill_balloon(struct virtio_balloon
*vb
, size_t num
)
129 /* We can only do one array worth at a time. */
130 num
= min(num
, ARRAY_SIZE(vb
->pfns
));
132 for (vb
->num_pfns
= 0; vb
->num_pfns
< num
;
133 vb
->num_pfns
+= VIRTIO_BALLOON_PAGES_PER_PAGE
) {
134 struct page
*page
= alloc_page(GFP_HIGHUSER
| __GFP_NORETRY
|
135 __GFP_NOMEMALLOC
| __GFP_NOWARN
);
137 if (printk_ratelimit())
138 dev_printk(KERN_INFO
, &vb
->vdev
->dev
,
139 "Out of puff! Can't get %zu pages\n",
141 /* Sleep for at least 1/5 of a second before retry. */
145 set_page_pfns(vb
->pfns
+ vb
->num_pfns
, page
);
146 vb
->num_pages
+= VIRTIO_BALLOON_PAGES_PER_PAGE
;
148 list_add(&page
->lru
, &vb
->pages
);
151 /* Didn't get any? Oh well. */
152 if (vb
->num_pfns
== 0)
155 tell_host(vb
, vb
->inflate_vq
);
158 static void release_pages_by_pfn(const u32 pfns
[], unsigned int num
)
162 /* Find pfns pointing at start of each page, get pages and free them. */
163 for (i
= 0; i
< num
; i
+= VIRTIO_BALLOON_PAGES_PER_PAGE
) {
164 __free_page(balloon_pfn_to_page(pfns
[i
]));
169 static void leak_balloon(struct virtio_balloon
*vb
, size_t num
)
173 /* We can only do one array worth at a time. */
174 num
= min(num
, ARRAY_SIZE(vb
->pfns
));
176 for (vb
->num_pfns
= 0; vb
->num_pfns
< num
;
177 vb
->num_pfns
+= VIRTIO_BALLOON_PAGES_PER_PAGE
) {
178 page
= list_first_entry(&vb
->pages
, struct page
, lru
);
179 list_del(&page
->lru
);
180 set_page_pfns(vb
->pfns
+ vb
->num_pfns
, page
);
181 vb
->num_pages
-= VIRTIO_BALLOON_PAGES_PER_PAGE
;
186 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
187 * is true, we *have* to do it in this order
189 tell_host(vb
, vb
->deflate_vq
);
190 release_pages_by_pfn(vb
->pfns
, vb
->num_pfns
);
193 static inline void update_stat(struct virtio_balloon
*vb
, int idx
,
196 BUG_ON(idx
>= VIRTIO_BALLOON_S_NR
);
197 vb
->stats
[idx
].tag
= tag
;
198 vb
->stats
[idx
].val
= val
;
201 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
203 static void update_balloon_stats(struct virtio_balloon
*vb
)
205 unsigned long events
[NR_VM_EVENT_ITEMS
];
209 all_vm_events(events
);
212 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_SWAP_IN
,
213 pages_to_bytes(events
[PSWPIN
]));
214 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_SWAP_OUT
,
215 pages_to_bytes(events
[PSWPOUT
]));
216 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MAJFLT
, events
[PGMAJFAULT
]);
217 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MINFLT
, events
[PGFAULT
]);
218 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MEMFREE
,
219 pages_to_bytes(i
.freeram
));
220 update_stat(vb
, idx
++, VIRTIO_BALLOON_S_MEMTOT
,
221 pages_to_bytes(i
.totalram
));
225 * While most virtqueues communicate guest-initiated requests to the hypervisor,
226 * the stats queue operates in reverse. The driver initializes the virtqueue
227 * with a single buffer. From that point forward, all conversations consist of
228 * a hypervisor request (a call to this function) which directs us to refill
229 * the virtqueue with a fresh stats buffer. Since stats collection can sleep,
230 * we notify our kthread which does the actual work via stats_handle_request().
232 static void stats_request(struct virtqueue
*vq
)
234 struct virtio_balloon
*vb
;
237 vb
= virtqueue_get_buf(vq
, &len
);
240 vb
->need_stats_update
= 1;
241 wake_up(&vb
->config_change
);
244 static void stats_handle_request(struct virtio_balloon
*vb
)
246 struct virtqueue
*vq
;
247 struct scatterlist sg
;
249 vb
->need_stats_update
= 0;
250 update_balloon_stats(vb
);
253 sg_init_one(&sg
, vb
->stats
, sizeof(vb
->stats
));
254 if (virtqueue_add_buf(vq
, &sg
, 1, 0, vb
, GFP_KERNEL
) < 0)
259 static void virtballoon_changed(struct virtio_device
*vdev
)
261 struct virtio_balloon
*vb
= vdev
->priv
;
263 wake_up(&vb
->config_change
);
266 static inline s64
towards_target(struct virtio_balloon
*vb
)
271 vb
->vdev
->config
->get(vb
->vdev
,
272 offsetof(struct virtio_balloon_config
, num_pages
),
274 target
= le32_to_cpu(v
);
275 return target
- vb
->num_pages
;
278 static void update_balloon_size(struct virtio_balloon
*vb
)
280 __le32 actual
= cpu_to_le32(vb
->num_pages
);
282 vb
->vdev
->config
->set(vb
->vdev
,
283 offsetof(struct virtio_balloon_config
, actual
),
284 &actual
, sizeof(actual
));
287 static int balloon(void *_vballoon
)
289 struct virtio_balloon
*vb
= _vballoon
;
292 while (!kthread_should_stop()) {
296 wait_event_interruptible(vb
->config_change
,
297 (diff
= towards_target(vb
)) != 0
298 || vb
->need_stats_update
299 || kthread_should_stop()
300 || freezing(current
));
301 if (vb
->need_stats_update
)
302 stats_handle_request(vb
);
304 fill_balloon(vb
, diff
);
306 leak_balloon(vb
, -diff
);
307 update_balloon_size(vb
);
312 static int init_vqs(struct virtio_balloon
*vb
)
314 struct virtqueue
*vqs
[3];
315 vq_callback_t
*callbacks
[] = { balloon_ack
, balloon_ack
, stats_request
};
316 const char *names
[] = { "inflate", "deflate", "stats" };
320 * We expect two virtqueues: inflate and deflate, and
323 nvqs
= virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_STATS_VQ
) ? 3 : 2;
324 err
= vb
->vdev
->config
->find_vqs(vb
->vdev
, nvqs
, vqs
, callbacks
, names
);
328 vb
->inflate_vq
= vqs
[0];
329 vb
->deflate_vq
= vqs
[1];
330 if (virtio_has_feature(vb
->vdev
, VIRTIO_BALLOON_F_STATS_VQ
)) {
331 struct scatterlist sg
;
332 vb
->stats_vq
= vqs
[2];
335 * Prime this virtqueue with one buffer so the hypervisor can
336 * use it to signal us later.
338 sg_init_one(&sg
, vb
->stats
, sizeof vb
->stats
);
339 if (virtqueue_add_buf(vb
->stats_vq
, &sg
, 1, 0, vb
, GFP_KERNEL
)
342 virtqueue_kick(vb
->stats_vq
);
347 static int virtballoon_probe(struct virtio_device
*vdev
)
349 struct virtio_balloon
*vb
;
352 vdev
->priv
= vb
= kmalloc(sizeof(*vb
), GFP_KERNEL
);
358 INIT_LIST_HEAD(&vb
->pages
);
360 init_waitqueue_head(&vb
->config_change
);
362 vb
->need_stats_update
= 0;
368 vb
->thread
= kthread_run(balloon
, vb
, "vballoon");
369 if (IS_ERR(vb
->thread
)) {
370 err
= PTR_ERR(vb
->thread
);
377 vdev
->config
->del_vqs(vdev
);
384 static void __devexit
virtballoon_remove(struct virtio_device
*vdev
)
386 struct virtio_balloon
*vb
= vdev
->priv
;
388 kthread_stop(vb
->thread
);
390 /* There might be pages left in the balloon: free them. */
391 while (vb
->num_pages
)
392 leak_balloon(vb
, vb
->num_pages
);
394 /* Now we reset the device so we can clean up the queues. */
395 vdev
->config
->reset(vdev
);
397 vdev
->config
->del_vqs(vdev
);
402 static int virtballoon_freeze(struct virtio_device
*vdev
)
404 struct virtio_balloon
*vb
= vdev
->priv
;
407 * The kthread is already frozen by the PM core before this
408 * function is called.
411 while (vb
->num_pages
)
412 leak_balloon(vb
, vb
->num_pages
);
413 update_balloon_size(vb
);
415 /* Ensure we don't get any more requests from the host */
416 vdev
->config
->reset(vdev
);
417 vdev
->config
->del_vqs(vdev
);
421 static int restore_common(struct virtio_device
*vdev
)
423 struct virtio_balloon
*vb
= vdev
->priv
;
426 ret
= init_vqs(vdev
->priv
);
430 fill_balloon(vb
, towards_target(vb
));
431 update_balloon_size(vb
);
435 static int virtballoon_restore(struct virtio_device
*vdev
)
437 return restore_common(vdev
);
441 static unsigned int features
[] = {
442 VIRTIO_BALLOON_F_MUST_TELL_HOST
,
443 VIRTIO_BALLOON_F_STATS_VQ
,
446 static struct virtio_driver virtio_balloon_driver
= {
447 .feature_table
= features
,
448 .feature_table_size
= ARRAY_SIZE(features
),
449 .driver
.name
= KBUILD_MODNAME
,
450 .driver
.owner
= THIS_MODULE
,
451 .id_table
= id_table
,
452 .probe
= virtballoon_probe
,
453 .remove
= __devexit_p(virtballoon_remove
),
454 .config_changed
= virtballoon_changed
,
456 .freeze
= virtballoon_freeze
,
457 .restore
= virtballoon_restore
,
461 static int __init
init(void)
463 return register_virtio_driver(&virtio_balloon_driver
);
466 static void __exit
fini(void)
468 unregister_virtio_driver(&virtio_balloon_driver
);
473 MODULE_DEVICE_TABLE(virtio
, id_table
);
474 MODULE_DESCRIPTION("Virtio balloon driver");
475 MODULE_LICENSE("GPL");