[mirror_ubuntu-zesty-kernel.git] / drivers / virtio / virtio_balloon.c

/*
 * Virtio balloon implementation, inspired by Dor Laor 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
 */

#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>
#include <linux/slab.h>
#include <linux/module.h>

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

	/* 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];

	/* Memory statistics */
	int need_stats_update;
	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
};

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 = virtqueue_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 (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
		BUG();
	virtqueue_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 |
					__GFP_NOMEMALLOC | __GFP_NOWARN);
		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--;
	}

	/*
	 * Note that if
	 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
	 * is true, we *have* to do it in this order
	 */
	tell_host(vb, vb->deflate_vq);
	release_pages_by_pfn(vb->pfns, vb->num_pfns);
}

static inline void update_stat(struct virtio_balloon *vb, int idx,
			       u16 tag, u64 val)
{
	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
	vb->stats[idx].tag = tag;
	vb->stats[idx].val = val;
}

#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)

static void update_balloon_stats(struct virtio_balloon *vb)
{
	unsigned long events[NR_VM_EVENT_ITEMS];
	struct sysinfo i;
	int idx = 0;

	all_vm_events(events);
	si_meminfo(&i);

	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
				pages_to_bytes(events[PSWPIN]));
	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
				pages_to_bytes(events[PSWPOUT]));
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
				pages_to_bytes(i.freeram));
	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
				pages_to_bytes(i.totalram));
}

/*
 * While most virtqueues communicate guest-initiated requests to the hypervisor,
 * the stats queue operates in reverse.  The driver initializes the virtqueue
 * with a single buffer.  From that point forward, all conversations consist of
 * a hypervisor request (a call to this function) which directs us to refill
 * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
 * we notify our kthread which does the actual work via stats_handle_request().
 */
static void stats_request(struct virtqueue *vq)
{
	struct virtio_balloon *vb;
	unsigned int len;

	vb = virtqueue_get_buf(vq, &len);
	if (!vb)
		return;
	vb->need_stats_update = 1;
	wake_up(&vb->config_change);
}

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

	vb->need_stats_update = 0;
	update_balloon_stats(vb);

	vq = vb->stats_vq;
	sg_init_one(&sg, vb->stats, sizeof(vb->stats));
	if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
		BUG();
	virtqueue_kick(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)
{
	__le32 v;
	s64 target;

	vb->vdev->config->get(vb->vdev,
			      offsetof(struct virtio_balloon_config, num_pages),
			      &v, sizeof(v));
	target = le32_to_cpu(v);
	return target - 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
					 || vb->need_stats_update
					 || kthread_should_stop()
					 || freezing(current));
		if (vb->need_stats_update)
			stats_handle_request(vb);
		if (diff > 0)
			fill_balloon(vb, diff);
		else if (diff < 0)
			leak_balloon(vb, -diff);
		update_balloon_size(vb);
	}
	return 0;
}

static int init_vqs(struct virtio_balloon *vb)
{
	struct virtqueue *vqs[3];
	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
	const char *names[] = { "inflate", "deflate", "stats" };
	int err, nvqs;

	/*
	 * We expect two virtqueues: inflate and deflate, and
	 * optionally stat.
	 */
	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
	err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
	if (err)
		return err;

	vb->inflate_vq = vqs[0];
	vb->deflate_vq = vqs[1];
	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
		struct scatterlist sg;
		vb->stats_vq = vqs[2];

		/*
		 * Prime this virtqueue with one buffer so the hypervisor can
		 * use it to signal us later.
		 */
		sg_init_one(&sg, vb->stats, sizeof vb->stats);
		if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL)
		    < 0)
			BUG();
		virtqueue_kick(vb->stats_vq);
	}
	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;
	vb->need_stats_update = 0;

	err = init_vqs(vb);
	if (err)
		goto out_free_vb;

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

	return 0;

out_del_vqs:
	vdev->config->del_vqs(vdev);
out_free_vb:
	kfree(vb);
out:
	return err;
}

static void __devexit 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);
}

#ifdef CONFIG_PM
static int virtballoon_freeze(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;

	/*
	 * The kthread is already frozen by the PM core before this
	 * function is called.
	 */

	while (vb->num_pages)
		leak_balloon(vb, vb->num_pages);
	update_balloon_size(vb);

	/* Ensure we don't get any more requests from the host */
	vdev->config->reset(vdev);
	vdev->config->del_vqs(vdev);
	return 0;
}

static int restore_common(struct virtio_device *vdev)
{
	struct virtio_balloon *vb = vdev->priv;
	int ret;

	ret = init_vqs(vdev->priv);
	if (ret)
		return ret;

	fill_balloon(vb, towards_target(vb));
	update_balloon_size(vb);
	return 0;
}

static int virtballoon_restore(struct virtio_device *vdev)
{
	return restore_common(vdev);
}
#endif

static unsigned int features[] = {
	VIRTIO_BALLOON_F_MUST_TELL_HOST,
	VIRTIO_BALLOON_F_STATS_VQ,
};

static struct virtio_driver virtio_balloon_driver = {
	.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,
#ifdef CONFIG_PM
	.freeze	=	virtballoon_freeze,
	.restore =	virtballoon_restore,
#endif
};

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

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

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio balloon driver");
MODULE_LICENSE("GPL");
Commit	Line	Data
1e214a5c SL	1	/*
1e214a5c SL	2	* Virtio balloon implementation, inspired by Dor Laor and Marcelo
6b35e407 RR	3	* Tosatti's implementations.
	4	*
	5	* Copyright 2008 Rusty Russell IBM Corporation
	6	*
	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.
	11	*
	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.
	16	*
	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
	20	*/
1e214a5c	21
6b35e407 RR	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>
6659a0f0	27	#include <linux/delay.h>
5a0e3ad6	28	#include <linux/slab.h>
b5a2c4f1	29	#include <linux/module.h>
6b35e407 RR	30
	31	struct virtio_balloon
	32	{
	33	struct virtio_device *vdev;
9564e138	34	struct virtqueue inflate_vq, deflate_vq, *stats_vq;
6b35e407 RR	35
	36	/* Where the ballooning thread waits for config to change. */
	37	wait_queue_head_t config_change;
	38
	39	/* The thread servicing the balloon. */
	40	struct task_struct *thread;
	41
	42	/* Waiting for host to ack the pages we released. */
	43	struct completion acked;
	44
6b35e407 RR	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];
9564e138 AL	52
9564e138 AL	53	/* Memory statistics */
1f34c71a	54	int need_stats_update;
9564e138	55	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
6b35e407 RR	56	};
	57
	58	static struct virtio_device_id id_table[] = {
	59	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	60	{ 0 },
	61	};
	62
1b4aa2fa HB	63	static u32 page_to_balloon_pfn(struct page *page)
	64	{
	65	unsigned long pfn = page_to_pfn(page);
	66
	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);
	70	}
	71
6b35e407 RR	72	static void balloon_ack(struct virtqueue *vq)
	73	{
	74	struct virtio_balloon *vb;
	75	unsigned int len;
	76
946cfe0e	77	vb = virtqueue_get_buf(vq, &len);
6b35e407 RR	78	if (vb)
	79	complete(&vb->acked);
	80	}
	81
	82	static void tell_host(struct virtio_balloon vb, struct virtqueue vq)
	83	{
	84	struct scatterlist sg;
	85
	86	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
	87
	88	init_completion(&vb->acked);
	89
	90	/* We should always be able to add one buffer to an empty queue. */
f96fde41	91	if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
6b35e407	92	BUG();
946cfe0e	93	virtqueue_kick(vq);
6b35e407 RR	94
	95	/* When host has read buffer, this completes via balloon_ack */
	96	wait_for_completion(&vb->acked);
	97	}
	98
	99	static void fill_balloon(struct virtio_balloon *vb, size_t num)
	100	{
	101	/* We can only do one array worth at a time. */
	102	num = min(num, ARRAY_SIZE(vb->pfns));
	103
	104	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
61fb06cc BS	105	struct page *page = alloc_page(GFP_HIGHUSER \| __GFP_NORETRY \|
61fb06cc BS	106	__GFP_NOMEMALLOC \| __GFP_NOWARN);
6b35e407 RR	107	if (!page) {
	108	if (printk_ratelimit())
	109	dev_printk(KERN_INFO, &vb->vdev->dev,
	110	"Out of puff! Can't get %zu pages\n",
	111	num);
	112	/* Sleep for at least 1/5 of a second before retry. */
	113	msleep(200);
	114	break;
	115	}
1b4aa2fa	116	vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
6b35e407 RR	117	totalram_pages--;
	118	vb->num_pages++;
	119	list_add(&page->lru, &vb->pages);
	120	}
	121
	122	/* Didn't get any? Oh well. */
	123	if (vb->num_pfns == 0)
	124	return;
	125
	126	tell_host(vb, vb->inflate_vq);
	127	}
	128
	129	static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
	130	{
	131	unsigned int i;
	132
	133	for (i = 0; i < num; i++) {
	134	__free_page(pfn_to_page(pfns[i]));
	135	totalram_pages++;
	136	}
	137	}
	138
	139	static void leak_balloon(struct virtio_balloon *vb, size_t num)
	140	{
	141	struct page *page;
	142
	143	/* We can only do one array worth at a time. */
	144	num = min(num, ARRAY_SIZE(vb->pfns));
	145
	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);
1b4aa2fa	149	vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
6b35e407 RR	150	vb->num_pages--;
	151	}
	152
bf50e69f DH	153	/*
	154	* Note that if
	155	* virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
	156	* is true, we have to do it in this order
	157	*/
	158	tell_host(vb, vb->deflate_vq);
	159	release_pages_by_pfn(vb->pfns, vb->num_pfns);
6b35e407 RR	160	}
6b35e407 RR	161
9564e138 AL	162	static inline void update_stat(struct virtio_balloon *vb, int idx,
	163	u16 tag, u64 val)
	164	{
	165	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
	166	vb->stats[idx].tag = tag;
	167	vb->stats[idx].val = val;
	168	}
	169
	170	#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
	171
	172	static void update_balloon_stats(struct virtio_balloon *vb)
	173	{
	174	unsigned long events[NR_VM_EVENT_ITEMS];
	175	struct sysinfo i;
	176	int idx = 0;
	177
	178	all_vm_events(events);
	179	si_meminfo(&i);
	180
	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));
	191	}
	192
	193	/*
	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
1f34c71a AL	198	* the virtqueue with a fresh stats buffer. Since stats collection can sleep,
1f34c71a AL	199	* we notify our kthread which does the actual work via stats_handle_request().
9564e138	200	*/
1f34c71a	201	static void stats_request(struct virtqueue *vq)
9564e138 AL	202	{
	203	struct virtio_balloon *vb;
	204	unsigned int len;
9564e138	205
946cfe0e	206	vb = virtqueue_get_buf(vq, &len);
9564e138 AL	207	if (!vb)
9564e138 AL	208	return;
1f34c71a AL	209	vb->need_stats_update = 1;
	210	wake_up(&vb->config_change);
	211	}
	212
	213	static void stats_handle_request(struct virtio_balloon *vb)
	214	{
	215	struct virtqueue *vq;
	216	struct scatterlist sg;
9564e138	217
1f34c71a	218	vb->need_stats_update = 0;
9564e138 AL	219	update_balloon_stats(vb);
9564e138 AL	220
1f34c71a	221	vq = vb->stats_vq;
9564e138	222	sg_init_one(&sg, vb->stats, sizeof(vb->stats));
f96fde41	223	if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
9564e138	224	BUG();
946cfe0e	225	virtqueue_kick(vq);
9564e138 AL	226	}
9564e138 AL	227
6b35e407 RR	228	static void virtballoon_changed(struct virtio_device *vdev)
	229	{
	230	struct virtio_balloon *vb = vdev->priv;
	231
	232	wake_up(&vb->config_change);
	233	}
	234
bdc1681c	235	static inline s64 towards_target(struct virtio_balloon *vb)
6b35e407	236	{
1a87228f DG	237	__le32 v;
	238	s64 target;
	239
72e61eb4 RR	240	vb->vdev->config->get(vb->vdev,
	241	offsetof(struct virtio_balloon_config, num_pages),
	242	&v, sizeof(v));
1a87228f DG	243	target = le32_to_cpu(v);
1a87228f DG	244	return target - vb->num_pages;
6b35e407 RR	245	}
	246
	247	static void update_balloon_size(struct virtio_balloon *vb)
	248	{
	249	__le32 actual = cpu_to_le32(vb->num_pages);
	250
	251	vb->vdev->config->set(vb->vdev,
	252	offsetof(struct virtio_balloon_config, actual),
	253	&actual, sizeof(actual));
	254	}
	255
	256	static int balloon(void *_vballoon)
	257	{
	258	struct virtio_balloon *vb = _vballoon;
	259
	260	set_freezable();
	261	while (!kthread_should_stop()) {
bdc1681c	262	s64 diff;
6b35e407 RR	263
	264	try_to_freeze();
	265	wait_event_interruptible(vb->config_change,
	266	(diff = towards_target(vb)) != 0
1f34c71a	267	\|\| vb->need_stats_update
84a139a9 MT	268	\|\| kthread_should_stop()
84a139a9 MT	269	\|\| freezing(current));
1f34c71a AL	270	if (vb->need_stats_update)
1f34c71a AL	271	stats_handle_request(vb);
6b35e407 RR	272	if (diff > 0)
	273	fill_balloon(vb, diff);
	274	else if (diff < 0)
	275	leak_balloon(vb, -diff);
	276	update_balloon_size(vb);
	277	}
	278	return 0;
	279	}
	280
be91c33d	281	static int init_vqs(struct virtio_balloon *vb)
6b35e407	282	{
9564e138	283	struct virtqueue *vqs[3];
1f34c71a	284	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
9564e138 AL	285	const char *names[] = { "inflate", "deflate", "stats" };
9564e138 AL	286	int err, nvqs;
6b35e407	287
be91c33d AS	288	/*
	289	* We expect two virtqueues: inflate and deflate, and
	290	* optionally stat.
	291	*/
9564e138	292	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
be91c33d	293	err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
d2a7ddda	294	if (err)
be91c33d	295	return err;
6b35e407	296
d2a7ddda MT	297	vb->inflate_vq = vqs[0];
d2a7ddda MT	298	vb->deflate_vq = vqs[1];
9564e138 AL	299	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
	300	struct scatterlist sg;
	301	vb->stats_vq = vqs[2];
	302
	303	/*
	304	* Prime this virtqueue with one buffer so the hypervisor can
	305	* use it to signal us later.
	306	*/
	307	sg_init_one(&sg, vb->stats, sizeof vb->stats);
f96fde41 RR	308	if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL)
f96fde41 RR	309	< 0)
9564e138	310	BUG();
946cfe0e	311	virtqueue_kick(vb->stats_vq);
9564e138	312	}
be91c33d AS	313	return 0;
	314	}
	315
	316	static int virtballoon_probe(struct virtio_device *vdev)
	317	{
	318	struct virtio_balloon *vb;
	319	int err;
	320
	321	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
	322	if (!vb) {
	323	err = -ENOMEM;
	324	goto out;
	325	}
	326
	327	INIT_LIST_HEAD(&vb->pages);
	328	vb->num_pages = 0;
	329	init_waitqueue_head(&vb->config_change);
	330	vb->vdev = vdev;
	331	vb->need_stats_update = 0;
	332
	333	err = init_vqs(vb);
	334	if (err)
	335	goto out_free_vb;
6b35e407 RR	336
	337	vb->thread = kthread_run(balloon, vb, "vballoon");
	338	if (IS_ERR(vb->thread)) {
	339	err = PTR_ERR(vb->thread);
d2a7ddda	340	goto out_del_vqs;
6b35e407 RR	341	}
6b35e407 RR	342
6b35e407 RR	343	return 0;
6b35e407 RR	344
d2a7ddda MT	345	out_del_vqs:
d2a7ddda MT	346	vdev->config->del_vqs(vdev);
6b35e407 RR	347	out_free_vb:
	348	kfree(vb);
	349	out:
	350	return err;
	351	}
	352
1e65175c	353	static void __devexit virtballoon_remove(struct virtio_device *vdev)
6b35e407 RR	354	{
	355	struct virtio_balloon *vb = vdev->priv;
	356
	357	kthread_stop(vb->thread);
	358
	359	/* There might be pages left in the balloon: free them. */
	360	while (vb->num_pages)
	361	leak_balloon(vb, vb->num_pages);
	362
	363	/* Now we reset the device so we can clean up the queues. */
	364	vdev->config->reset(vdev);
	365
d2a7ddda	366	vdev->config->del_vqs(vdev);
6b35e407 RR	367	kfree(vb);
	368	}
	369
e562966d AS	370	#ifdef CONFIG_PM
	371	static int virtballoon_freeze(struct virtio_device *vdev)
	372	{
4eb05d56 AS	373	struct virtio_balloon *vb = vdev->priv;
4eb05d56 AS	374
e562966d AS	375	/*
	376	* The kthread is already frozen by the PM core before this
	377	* function is called.
	378	*/
	379
4eb05d56 AS	380	while (vb->num_pages)
	381	leak_balloon(vb, vb->num_pages);
	382	update_balloon_size(vb);
	383
e562966d AS	384	/* Ensure we don't get any more requests from the host */
	385	vdev->config->reset(vdev);
	386	vdev->config->del_vqs(vdev);
	387	return 0;
	388	}
	389
4eb05d56 AS	390	static int restore_common(struct virtio_device *vdev)
	391	{
	392	struct virtio_balloon *vb = vdev->priv;
	393	int ret;
	394
	395	ret = init_vqs(vdev->priv);
	396	if (ret)
	397	return ret;
	398
	399	fill_balloon(vb, towards_target(vb));
	400	update_balloon_size(vb);
	401	return 0;
	402	}
	403
e562966d AS	404	static int virtballoon_restore(struct virtio_device *vdev)
e562966d AS	405	{
4eb05d56	406	return restore_common(vdev);
e562966d AS	407	}
	408	#endif
	409
9564e138 AL	410	static unsigned int features[] = {
	411	VIRTIO_BALLOON_F_MUST_TELL_HOST,
	412	VIRTIO_BALLOON_F_STATS_VQ,
	413	};
c45a6816	414
d817cd52	415	static struct virtio_driver virtio_balloon_driver = {
c45a6816 RR	416	.feature_table = features,
c45a6816 RR	417	.feature_table_size = ARRAY_SIZE(features),
6b35e407 RR	418	.driver.name = KBUILD_MODNAME,
	419	.driver.owner = THIS_MODULE,
	420	.id_table = id_table,
	421	.probe = virtballoon_probe,
	422	.remove = __devexit_p(virtballoon_remove),
	423	.config_changed = virtballoon_changed,
e562966d AS	424	#ifdef CONFIG_PM
	425	.freeze = virtballoon_freeze,
	426	.restore = virtballoon_restore,
e562966d	427	#endif
6b35e407 RR	428	};
	429
	430	static int __init init(void)
	431	{
d817cd52	432	return register_virtio_driver(&virtio_balloon_driver);
6b35e407 RR	433	}
	434
	435	static void __exit fini(void)
	436	{
d817cd52	437	unregister_virtio_driver(&virtio_balloon_driver);
6b35e407 RR	438	}
	439	module_init(init);
	440	module_exit(fini);
	441
	442	MODULE_DEVICE_TABLE(virtio, id_table);
	443	MODULE_DESCRIPTION("Virtio balloon driver");
	444	MODULE_LICENSE("GPL");