[linux-2.6-block.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>
#include <linux/delay.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 u32 page_to_balloon_pfn(struct page *page)
{
	unsigned long pfn = page_to_pfn(page);

	BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
	/* Convert pfn from Linux page size to balloon page size. */
	return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
}

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_balloon_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_balloon_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 s64 towards_target(struct virtio_balloon *vb)
{
	u32 v;
	vb->vdev->config->get(vb->vdev,
			      offsetof(struct virtio_balloon_config, num_pages),
			      &v, sizeof(v));
	return (s64)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()) {
		s64 diff;

		try_to_freeze();
		wait_event_interruptible(vb->config_change,
					 (diff = towards_target(vb)) != 0
					 || kthread_should_stop()
					 || freezing(current));
		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;
	struct virtqueue *vqs[2];
	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack };
	const char *names[] = { "inflate", "deflate" };
	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. */
	err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
	if (err)
		goto out_free_vb;

	vb->inflate_vq = vqs[0];
	vb->deflate_vq = vqs[1];

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

	vb->tell_host_first
		= virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);

	return 0;

out_del_vqs:
	vdev->config->del_vqs(vdev);
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_vqs(vdev);
	kfree(vb);
}

static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };

static struct virtio_driver virtio_balloon = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.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>
6659a0f0	26	#include <linux/delay.h>
6b35e407 RR	27
	28	struct virtio_balloon
	29	{
	30	struct virtio_device *vdev;
	31	struct virtqueue inflate_vq, deflate_vq;
	32
	33	/* Where the ballooning thread waits for config to change. */
	34	wait_queue_head_t config_change;
	35
	36	/* The thread servicing the balloon. */
	37	struct task_struct *thread;
	38
	39	/* Waiting for host to ack the pages we released. */
	40	struct completion acked;
	41
	42	/* Do we have to tell Host before we reuse pages? */
	43	bool tell_host_first;
	44
	45	/* The pages we've told the Host we're not using. */
	46	unsigned int num_pages;
	47	struct list_head pages;
	48
	49	/* The array of pfns we tell the Host about. */
	50	unsigned int num_pfns;
	51	u32 pfns[256];
	52	};
	53
	54	static struct virtio_device_id id_table[] = {
	55	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	56	{ 0 },
	57	};
	58
1b4aa2fa HB	59	static u32 page_to_balloon_pfn(struct page *page)
	60	{
	61	unsigned long pfn = page_to_pfn(page);
	62
	63	BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
	64	/* Convert pfn from Linux page size to balloon page size. */
	65	return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
	66	}
	67
6b35e407 RR	68	static void balloon_ack(struct virtqueue *vq)
	69	{
	70	struct virtio_balloon *vb;
	71	unsigned int len;
	72
	73	vb = vq->vq_ops->get_buf(vq, &len);
	74	if (vb)
	75	complete(&vb->acked);
	76	}
	77
	78	static void tell_host(struct virtio_balloon vb, struct virtqueue vq)
	79	{
	80	struct scatterlist sg;
	81
	82	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
	83
	84	init_completion(&vb->acked);
	85
	86	/* We should always be able to add one buffer to an empty queue. */
	87	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) != 0)
	88	BUG();
	89	vq->vq_ops->kick(vq);
	90
	91	/* When host has read buffer, this completes via balloon_ack */
	92	wait_for_completion(&vb->acked);
	93	}
	94
	95	static void fill_balloon(struct virtio_balloon *vb, size_t num)
	96	{
	97	/* We can only do one array worth at a time. */
	98	num = min(num, ARRAY_SIZE(vb->pfns));
	99
	100	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
	101	struct page *page = alloc_page(GFP_HIGHUSER \| __GFP_NORETRY);
	102	if (!page) {
	103	if (printk_ratelimit())
	104	dev_printk(KERN_INFO, &vb->vdev->dev,
	105	"Out of puff! Can't get %zu pages\n",
	106	num);
	107	/* Sleep for at least 1/5 of a second before retry. */
	108	msleep(200);
	109	break;
	110	}
1b4aa2fa	111	vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
6b35e407 RR	112	totalram_pages--;
	113	vb->num_pages++;
	114	list_add(&page->lru, &vb->pages);
	115	}
	116
	117	/* Didn't get any? Oh well. */
	118	if (vb->num_pfns == 0)
	119	return;
	120
	121	tell_host(vb, vb->inflate_vq);
	122	}
	123
	124	static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
	125	{
	126	unsigned int i;
	127
	128	for (i = 0; i < num; i++) {
	129	__free_page(pfn_to_page(pfns[i]));
	130	totalram_pages++;
	131	}
	132	}
	133
	134	static void leak_balloon(struct virtio_balloon *vb, size_t num)
	135	{
	136	struct page *page;
	137
	138	/* We can only do one array worth at a time. */
	139	num = min(num, ARRAY_SIZE(vb->pfns));
	140
	141	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
	142	page = list_first_entry(&vb->pages, struct page, lru);
	143	list_del(&page->lru);
1b4aa2fa	144	vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
6b35e407 RR	145	vb->num_pages--;
	146	}
	147
	148	if (vb->tell_host_first) {
	149	tell_host(vb, vb->deflate_vq);
	150	release_pages_by_pfn(vb->pfns, vb->num_pfns);
	151	} else {
	152	release_pages_by_pfn(vb->pfns, vb->num_pfns);
	153	tell_host(vb, vb->deflate_vq);
	154	}
	155	}
	156
	157	static void virtballoon_changed(struct virtio_device *vdev)
	158	{
	159	struct virtio_balloon *vb = vdev->priv;
	160
	161	wake_up(&vb->config_change);
	162	}
	163
bdc1681c	164	static inline s64 towards_target(struct virtio_balloon *vb)
6b35e407 RR	165	{
6b35e407 RR	166	u32 v;
72e61eb4 RR	167	vb->vdev->config->get(vb->vdev,
	168	offsetof(struct virtio_balloon_config, num_pages),
	169	&v, sizeof(v));
532a6086	170	return (s64)v - vb->num_pages;
6b35e407 RR	171	}
	172
	173	static void update_balloon_size(struct virtio_balloon *vb)
	174	{
	175	__le32 actual = cpu_to_le32(vb->num_pages);
	176
	177	vb->vdev->config->set(vb->vdev,
	178	offsetof(struct virtio_balloon_config, actual),
	179	&actual, sizeof(actual));
	180	}
	181
	182	static int balloon(void *_vballoon)
	183	{
	184	struct virtio_balloon *vb = _vballoon;
	185
	186	set_freezable();
	187	while (!kthread_should_stop()) {
bdc1681c	188	s64 diff;
6b35e407 RR	189
	190	try_to_freeze();
	191	wait_event_interruptible(vb->config_change,
	192	(diff = towards_target(vb)) != 0
84a139a9 MT	193	\|\| kthread_should_stop()
84a139a9 MT	194	\|\| freezing(current));
6b35e407 RR	195	if (diff > 0)
	196	fill_balloon(vb, diff);
	197	else if (diff < 0)
	198	leak_balloon(vb, -diff);
	199	update_balloon_size(vb);
	200	}
	201	return 0;
	202	}
	203
	204	static int virtballoon_probe(struct virtio_device *vdev)
	205	{
	206	struct virtio_balloon *vb;
d2a7ddda MT	207	struct virtqueue *vqs[2];
	208	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack };
	209	const char *names[] = { "inflate", "deflate" };
6b35e407 RR	210	int err;
	211
	212	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
	213	if (!vb) {
	214	err = -ENOMEM;
	215	goto out;
	216	}
	217
	218	INIT_LIST_HEAD(&vb->pages);
	219	vb->num_pages = 0;
	220	init_waitqueue_head(&vb->config_change);
	221	vb->vdev = vdev;
	222
	223	/* We expect two virtqueues. */
d2a7ddda MT	224	err = vdev->config->find_vqs(vdev, 2, vqs, callbacks, names);
d2a7ddda MT	225	if (err)
6b35e407	226	goto out_free_vb;
6b35e407	227
d2a7ddda MT	228	vb->inflate_vq = vqs[0];
d2a7ddda MT	229	vb->deflate_vq = vqs[1];
6b35e407 RR	230
	231	vb->thread = kthread_run(balloon, vb, "vballoon");
	232	if (IS_ERR(vb->thread)) {
	233	err = PTR_ERR(vb->thread);
d2a7ddda	234	goto out_del_vqs;
6b35e407 RR	235	}
	236
	237	vb->tell_host_first
c45a6816	238	= virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
6b35e407 RR	239
	240	return 0;
	241
d2a7ddda MT	242	out_del_vqs:
d2a7ddda MT	243	vdev->config->del_vqs(vdev);
6b35e407 RR	244	out_free_vb:
	245	kfree(vb);
	246	out:
	247	return err;
	248	}
	249
	250	static void virtballoon_remove(struct virtio_device *vdev)
	251	{
	252	struct virtio_balloon *vb = vdev->priv;
	253
	254	kthread_stop(vb->thread);
	255
	256	/* There might be pages left in the balloon: free them. */
	257	while (vb->num_pages)
	258	leak_balloon(vb, vb->num_pages);
	259
	260	/* Now we reset the device so we can clean up the queues. */
	261	vdev->config->reset(vdev);
	262
d2a7ddda	263	vdev->config->del_vqs(vdev);
6b35e407 RR	264	kfree(vb);
	265	}
	266
c45a6816 RR	267	static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST };
c45a6816 RR	268
6b35e407	269	static struct virtio_driver virtio_balloon = {
c45a6816 RR	270	.feature_table = features,
c45a6816 RR	271	.feature_table_size = ARRAY_SIZE(features),
6b35e407 RR	272	.driver.name = KBUILD_MODNAME,
	273	.driver.owner = THIS_MODULE,
	274	.id_table = id_table,
	275	.probe = virtballoon_probe,
	276	.remove = __devexit_p(virtballoon_remove),
	277	.config_changed = virtballoon_changed,
	278	};
	279
	280	static int __init init(void)
	281	{
	282	return register_virtio_driver(&virtio_balloon);
	283	}
	284
	285	static void __exit fini(void)
	286	{
	287	unregister_virtio_driver(&virtio_balloon);
	288	}
	289	module_init(init);
	290	module_exit(fini);
	291
	292	MODULE_DEVICE_TABLE(virtio, id_table);
	293	MODULE_DESCRIPTION("Virtio balloon driver");
	294	MODULE_LICENSE("GPL");