[deliverable/linux.git] / drivers / virtio / virtio_balloon.c

/* Virtio balloon implementation, inspired by Dor Loar and Marcelo
 * Tosatti's implementations.
 *
 *  Copyright 2008 Rusty Russell IBM Corporation
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
//#define DEBUG
#include <linux/virtio.h>
#include <linux/virtio_balloon.h>
#include <linux/swap.h>
#include <linux/kthread.h>
#include <linux/freezer.h>

struct virtio_balloon
{
	struct virtio_device *vdev;
	struct virtqueue *inflate_vq, *deflate_vq;

	/* Where the ballooning thread waits for config to change. */
	wait_queue_head_t config_change;

	/* The thread servicing the balloon. */
	struct task_struct *thread;

	/* Waiting for host to ack the pages we released. */
	struct completion acked;

	/* Do we have to tell Host *before* we reuse pages? */
	bool tell_host_first;

	/* The pages we've told the Host we're not using. */
	unsigned int num_pages;
	struct list_head pages;

	/* The array of pfns we tell the Host about. */
	unsigned int num_pfns;
	u32 pfns[256];
};

static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	{ 0 },
};

static void balloon_ack(struct virtqueue *vq)
{
	struct virtio_balloon *vb;
	unsigned int len;

	vb = vq->vq_ops->get_buf(vq, &len);
	if (vb)
		complete(&vb->acked);
}

static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
{
	struct scatterlist sg;

	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);

	init_completion(&vb->acked);

	/* We should always be able to add one buffer to an empty queue. */
	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0)
		BUG();
	vq->vq_ops->kick(vq);

	/* When host has read buffer, this completes via balloon_ack */
	wait_for_completion(&vb->acked);
}

static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
	/* We can only do one array worth at a time. */
	num = min(num, ARRAY_SIZE(vb->pfns));

	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
		struct page *page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY);
		if (!page) {
			if (printk_ratelimit())
				dev_printk(KERN_INFO, &vb->vdev->dev,
					   "Out of puff! Can't get %zu pages\n",
					   num);
			/* Sleep for at least 1/5 of a second before retry. */
			msleep(200);
			break;
		}
		vb->pfns[vb->num_pfns] = page_to_pfn(page);
		totalram_pages--;
		vb->num_pages++;
		list_add(&page->lru, &vb->pages);
	}

	/* Didn't get any?  Oh well. */
	if (vb->num_pfns == 0)
		return;

	tell_host(vb, vb->inflate_vq);
}

static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
{
	unsigned int i;

	for (i = 0; i < num; i++) {
		__free_page(pfn_to_page(pfns[i]));
		totalram_pages++;
	}
}

static void leak_balloon(struct virtio_balloon *vb, size_t num)
{
	struct page *page;

	/* We can only do one array worth at a time. */
	num = min(num, ARRAY_SIZE(vb->pfns));

	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
		page = list_first_entry(&vb->pages, struct page, lru);
		list_del(&page->lru);
		vb->pfns[vb->num_pfns] = page_to_pfn(page);
		vb->num_pages--;
	}

	if (vb->tell_host_first) {
		tell_host(vb, vb->deflate_vq);
		release_pages_by_pfn(vb->pfns, vb->num_pfns);
	} else {
		release_pages_by_pfn(vb->pfns, vb->num_pfns);
		tell_host(vb, vb->deflate_vq);
	}
}

static void virtballoon_changed(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;

	wake_up(&vb->config_change);
}

static inline int towards_target(struct virtio_balloon *vb)
{
	u32 v;
	__virtio_config_val(vb->vdev,
			    offsetof(struct virtio_balloon_config, num_pages),
			    &v);
	return v - vb->num_pages;
}

static void update_balloon_size(struct virtio_balloon *vb)
{
	__le32 actual = cpu_to_le32(vb->num_pages);

	vb->vdev->config->set(vb->vdev,
			      offsetof(struct virtio_balloon_config, actual),
			      &actual, sizeof(actual));
}

static int balloon(void *_vballoon)
{
	struct virtio_balloon *vb = _vballoon;

	set_freezable();
	while (!kthread_should_stop()) {
		int diff;

		try_to_freeze();
		wait_event_interruptible(vb->config_change,
					 (diff = towards_target(vb)) != 0
					 || kthread_should_stop());
		if (diff > 0)
			fill_balloon(vb, diff);
		else if (diff < 0)
			leak_balloon(vb, -diff);
		update_balloon_size(vb);
	}
	return 0;
}

static int virtballoon_probe(struct virtio_device *vdev)
{
	struct virtio_balloon *vb;
	int err;

	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
	if (!vb) {
		err = -ENOMEM;
		goto out;
	}

	INIT_LIST_HEAD(&vb->pages);
	vb->num_pages = 0;
	init_waitqueue_head(&vb->config_change);
	vb->vdev = vdev;

	/* We expect two virtqueues. */
	vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack);
	if (IS_ERR(vb->inflate_vq)) {
		err = PTR_ERR(vb->inflate_vq);
		goto out_free_vb;
	}

	vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack);
	if (IS_ERR(vb->deflate_vq)) {
		err = PTR_ERR(vb->deflate_vq);
		goto out_del_inflate_vq;
	}

	vb->thread = kthread_run(balloon, vb, "vballoon");
	if (IS_ERR(vb->thread)) {
		err = PTR_ERR(vb->thread);
		goto out_del_deflate_vq;
	}

	vb->tell_host_first
		= vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);

	return 0;

out_del_deflate_vq:
	vdev->config->del_vq(vb->deflate_vq);
out_del_inflate_vq:
	vdev->config->del_vq(vb->inflate_vq);
out_free_vb:
	kfree(vb);
out:
	return err;
}

static void virtballoon_remove(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;

	kthread_stop(vb->thread);

	/* There might be pages left in the balloon: free them. */
	while (vb->num_pages)
		leak_balloon(vb, vb->num_pages);

	/* Now we reset the device so we can clean up the queues. */
	vdev->config->reset(vdev);

	vdev->config->del_vq(vb->deflate_vq);
	vdev->config->del_vq(vb->inflate_vq);
	kfree(vb);
}

static struct virtio_driver virtio_balloon = {
	.driver.name =	KBUILD_MODNAME,
	.driver.owner =	THIS_MODULE,
	.id_table =	id_table,
	.probe =	virtballoon_probe,
	.remove =	__devexit_p(virtballoon_remove),
	.config_changed = virtballoon_changed,
};

static int __init init(void)
{
	return register_virtio_driver(&virtio_balloon);
}

static void __exit fini(void)
{
	unregister_virtio_driver(&virtio_balloon);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio balloon driver");
MODULE_LICENSE("GPL");
Commit	Line	Data
6b35e407 RR	1	/* 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>
	26
	27	struct virtio_balloon
	28	{
	29	struct virtio_device *vdev;
	30	struct virtqueue inflate_vq, deflate_vq;
	31
	32	/* Where the ballooning thread waits for config to change. */
	33	wait_queue_head_t config_change;
	34
	35	/* The thread servicing the balloon. */
	36	struct task_struct *thread;
	37
	38	/* Waiting for host to ack the pages we released. */
	39	struct completion acked;
	40
	41	/* Do we have to tell Host before we reuse pages? */
	42	bool tell_host_first;
	43
	44	/* The pages we've told the Host we're not using. */
	45	unsigned int num_pages;
	46	struct list_head pages;
	47
	48	/* The array of pfns we tell the Host about. */
	49	unsigned int num_pfns;
	50	u32 pfns[256];
	51	};
	52
	53	static struct virtio_device_id id_table[] = {
	54	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	55	{ 0 },
	56	};
	57
	58	static void balloon_ack(struct virtqueue *vq)
	59	{
	60	struct virtio_balloon *vb;
	61	unsigned int len;
	62
	63	vb = vq->vq_ops->get_buf(vq, &len);
	64	if (vb)
65	complete(&vb->acked);
66	}
67
68	static void tell_host(struct virtio_balloon vb, struct virtqueue vq)
69	{
70	struct scatterlist sg;
71
72	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
73
74	init_completion(&vb->acked);
75
76	/* We should always be able to add one buffer to an empty queue. */
77	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0)
78	BUG();
79	vq->vq_ops->kick(vq);
80
81	/* When host has read buffer, this completes via balloon_ack */
82	wait_for_completion(&vb->acked);
83	}
84
85	static void fill_balloon(struct virtio_balloon *vb, size_t num)
86	{
87	/* We can only do one array worth at a time. */
88	num = min(num, ARRAY_SIZE(vb->pfns));
89
90	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
91	struct page *page = alloc_page(GFP_HIGHUSER \| __GFP_NORETRY);
92	if (!page) {
93	if (printk_ratelimit())
94	dev_printk(KERN_INFO, &vb->vdev->dev,
95	"Out of puff! Can't get %zu pages\n",
96	num);
97	/* Sleep for at least 1/5 of a second before retry. */
98	msleep(200);
99	break;
100	}
101	vb->pfns[vb->num_pfns] = page_to_pfn(page);
102	totalram_pages--;
103	vb->num_pages++;
104	list_add(&page->lru, &vb->pages);
105	}
106
107	/* Didn't get any? Oh well. */
108	if (vb->num_pfns == 0)
109	return;
110
111	tell_host(vb, vb->inflate_vq);
112	}
113
114	static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
115	{
116	unsigned int i;
117
118	for (i = 0; i < num; i++) {
119	__free_page(pfn_to_page(pfns[i]));
120	totalram_pages++;
121	}
122	}
123
124	static void leak_balloon(struct virtio_balloon *vb, size_t num)
125	{
126	struct page *page;
127
128	/* We can only do one array worth at a time. */
129	num = min(num, ARRAY_SIZE(vb->pfns));
130
131	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
132	page = list_first_entry(&vb->pages, struct page, lru);
133	list_del(&page->lru);
134	vb->pfns[vb->num_pfns] = page_to_pfn(page);
135	vb->num_pages--;
136	}
137
138	if (vb->tell_host_first) {
139	tell_host(vb, vb->deflate_vq);
140	release_pages_by_pfn(vb->pfns, vb->num_pfns);
141	} else {
142	release_pages_by_pfn(vb->pfns, vb->num_pfns);
143	tell_host(vb, vb->deflate_vq);
144	}
145	}
146
147	static void virtballoon_changed(struct virtio_device *vdev)
148	{
149	struct virtio_balloon *vb = vdev->priv;
150
151	wake_up(&vb->config_change);
152	}
153
154	static inline int towards_target(struct virtio_balloon *vb)
155	{
156	u32 v;
157	__virtio_config_val(vb->vdev,
158	offsetof(struct virtio_balloon_config, num_pages),
159	&v);
160	return v - vb->num_pages;
161	}
162
163	static void update_balloon_size(struct virtio_balloon *vb)
164	{
165	__le32 actual = cpu_to_le32(vb->num_pages);
166
167	vb->vdev->config->set(vb->vdev,
168	offsetof(struct virtio_balloon_config, actual),
169	&actual, sizeof(actual));
170	}
171
172	static int balloon(void *_vballoon)
173	{
174	struct virtio_balloon *vb = _vballoon;
175
176	set_freezable();
177	while (!kthread_should_stop()) {
178	int diff;
179
180	try_to_freeze();
181	wait_event_interruptible(vb->config_change,
182	(diff = towards_target(vb)) != 0
183	\|\| kthread_should_stop());
184	if (diff > 0)
185	fill_balloon(vb, diff);
186	else if (diff < 0)
187	leak_balloon(vb, -diff);
188	update_balloon_size(vb);
189	}
190	return 0;
191	}
192
193	static int virtballoon_probe(struct virtio_device *vdev)
194	{
195	struct virtio_balloon *vb;
196	int err;
197
198	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
199	if (!vb) {
200	err = -ENOMEM;
201	goto out;
202	}
203
204	INIT_LIST_HEAD(&vb->pages);
205	vb->num_pages = 0;
206	init_waitqueue_head(&vb->config_change);
207	vb->vdev = vdev;
208
209	/* We expect two virtqueues. */
210	vb->inflate_vq = vdev->config->find_vq(vdev, 0, balloon_ack);
211	if (IS_ERR(vb->inflate_vq)) {
212	err = PTR_ERR(vb->inflate_vq);
213	goto out_free_vb;
214	}
215
216	vb->deflate_vq = vdev->config->find_vq(vdev, 1, balloon_ack);
217	if (IS_ERR(vb->deflate_vq)) {
218	err = PTR_ERR(vb->deflate_vq);
219	goto out_del_inflate_vq;
220	}
221
222	vb->thread = kthread_run(balloon, vb, "vballoon");
223	if (IS_ERR(vb->thread)) {
224	err = PTR_ERR(vb->thread);
225	goto out_del_deflate_vq;
226	}
227
228	vb->tell_host_first
229	= vdev->config->feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
230
231	return 0;
232
233	out_del_deflate_vq:
234	vdev->config->del_vq(vb->deflate_vq);
235	out_del_inflate_vq:
236	vdev->config->del_vq(vb->inflate_vq);
237	out_free_vb:
238	kfree(vb);
239	out:
240	return err;
241	}
242
243	static void virtballoon_remove(struct virtio_device *vdev)
244	{
245	struct virtio_balloon *vb = vdev->priv;
246
247	kthread_stop(vb->thread);
248
249	/* There might be pages left in the balloon: free them. */
250	while (vb->num_pages)
251	leak_balloon(vb, vb->num_pages);
252
253	/* Now we reset the device so we can clean up the queues. */
254	vdev->config->reset(vdev);
255
256	vdev->config->del_vq(vb->deflate_vq);
257	vdev->config->del_vq(vb->inflate_vq);
258	kfree(vb);
259	}
260
261	static struct virtio_driver virtio_balloon = {
262	.driver.name = KBUILD_MODNAME,
263	.driver.owner = THIS_MODULE,
264	.id_table = id_table,
265	.probe = virtballoon_probe,
266	.remove = __devexit_p(virtballoon_remove),
267	.config_changed = virtballoon_changed,
268	};
269
270	static int __init init(void)
271	{
272	return register_virtio_driver(&virtio_balloon);
273	}
274
275	static void __exit fini(void)
276	{
277	unregister_virtio_driver(&virtio_balloon);
278	}
279	module_init(init);
280	module_exit(fini);
281
282	MODULE_DEVICE_TABLE(virtio, id_table);
283	MODULE_DESCRIPTION("Virtio balloon driver");
284	MODULE_LICENSE("GPL");