[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>
#include <linux/slab.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;

	/* 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];

	/* 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 = 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 |
					__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--;
	}

	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 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 = vq->vq_ops->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 (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
		BUG();
	vq->vq_ops->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)
{
	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
					 || 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 virtballoon_probe(struct virtio_device *vdev)
{
	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;

	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;

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

	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 (vb->stats_vq->vq_ops->add_buf(vb->stats_vq,
						  &sg, 1, 0, vb) < 0)
			BUG();
		vb->stats_vq->vq_ops->kick(vb->stats_vq);
	}

	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 __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);
}

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,
};

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
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>
5a0e3ad6	27	#include <linux/slab.h>
6b35e407 RR	28
	29	struct virtio_balloon
	30	{
	31	struct virtio_device *vdev;
9564e138	32	struct virtqueue inflate_vq, deflate_vq, *stats_vq;
6b35e407 RR	33
	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
	43	/* Do we have to tell Host before we reuse pages? */
	44	bool tell_host_first;
	45
	46	/* The pages we've told the Host we're not using. */
	47	unsigned int num_pages;
	48	struct list_head pages;
	49
	50	/* The array of pfns we tell the Host about. */
	51	unsigned int num_pfns;
	52	u32 pfns[256];
9564e138 AL	53
9564e138 AL	54	/* Memory statistics */
1f34c71a	55	int need_stats_update;
9564e138	56	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
6b35e407 RR	57	};
	58
	59	static struct virtio_device_id id_table[] = {
	60	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	61	{ 0 },
	62	};
	63
1b4aa2fa HB	64	static u32 page_to_balloon_pfn(struct page *page)
	65	{
	66	unsigned long pfn = page_to_pfn(page);
	67
	68	BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
	69	/* Convert pfn from Linux page size to balloon page size. */
	70	return pfn >> (PAGE_SHIFT - VIRTIO_BALLOON_PFN_SHIFT);
	71	}
	72
6b35e407 RR	73	static void balloon_ack(struct virtqueue *vq)
	74	{
	75	struct virtio_balloon *vb;
	76	unsigned int len;
	77
	78	vb = vq->vq_ops->get_buf(vq, &len);
	79	if (vb)
	80	complete(&vb->acked);
	81	}
	82
	83	static void tell_host(struct virtio_balloon vb, struct virtqueue vq)
	84	{
	85	struct scatterlist sg;
	86
	87	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
	88
	89	init_completion(&vb->acked);
	90
	91	/* We should always be able to add one buffer to an empty queue. */
3c1b27d5	92	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
6b35e407 RR	93	BUG();
	94	vq->vq_ops->kick(vq);
	95
	96	/* When host has read buffer, this completes via balloon_ack */
	97	wait_for_completion(&vb->acked);
	98	}
	99
	100	static void fill_balloon(struct virtio_balloon *vb, size_t num)
	101	{
	102	/* We can only do one array worth at a time. */
	103	num = min(num, ARRAY_SIZE(vb->pfns));
	104
	105	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
61fb06cc BS	106	struct page *page = alloc_page(GFP_HIGHUSER \| __GFP_NORETRY \|
61fb06cc BS	107	__GFP_NOMEMALLOC \| __GFP_NOWARN);
6b35e407 RR	108	if (!page) {
	109	if (printk_ratelimit())
	110	dev_printk(KERN_INFO, &vb->vdev->dev,
	111	"Out of puff! Can't get %zu pages\n",
	112	num);
	113	/* Sleep for at least 1/5 of a second before retry. */
	114	msleep(200);
	115	break;
	116	}
1b4aa2fa	117	vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
6b35e407 RR	118	totalram_pages--;
	119	vb->num_pages++;
	120	list_add(&page->lru, &vb->pages);
	121	}
	122
	123	/* Didn't get any? Oh well. */
	124	if (vb->num_pfns == 0)
	125	return;
	126
	127	tell_host(vb, vb->inflate_vq);
	128	}
	129
	130	static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
	131	{
	132	unsigned int i;
	133
	134	for (i = 0; i < num; i++) {
	135	__free_page(pfn_to_page(pfns[i]));
	136	totalram_pages++;
	137	}
	138	}
	139
	140	static void leak_balloon(struct virtio_balloon *vb, size_t num)
	141	{
	142	struct page *page;
	143
	144	/* We can only do one array worth at a time. */
	145	num = min(num, ARRAY_SIZE(vb->pfns));
	146
	147	for (vb->num_pfns = 0; vb->num_pfns < num; vb->num_pfns++) {
	148	page = list_first_entry(&vb->pages, struct page, lru);
	149	list_del(&page->lru);
1b4aa2fa	150	vb->pfns[vb->num_pfns] = page_to_balloon_pfn(page);
6b35e407 RR	151	vb->num_pages--;
	152	}
	153
	154	if (vb->tell_host_first) {
	155	tell_host(vb, vb->deflate_vq);
	156	release_pages_by_pfn(vb->pfns, vb->num_pfns);
	157	} else {
	158	release_pages_by_pfn(vb->pfns, vb->num_pfns);
	159	tell_host(vb, vb->deflate_vq);
	160	}
	161	}
	162
9564e138 AL	163	static inline void update_stat(struct virtio_balloon *vb, int idx,
	164	u16 tag, u64 val)
	165	{
	166	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
	167	vb->stats[idx].tag = tag;
	168	vb->stats[idx].val = val;
	169	}
	170
	171	#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
	172
	173	static void update_balloon_stats(struct virtio_balloon *vb)
	174	{
	175	unsigned long events[NR_VM_EVENT_ITEMS];
	176	struct sysinfo i;
	177	int idx = 0;
	178
	179	all_vm_events(events);
	180	si_meminfo(&i);
	181
	182	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
	183	pages_to_bytes(events[PSWPIN]));
	184	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
	185	pages_to_bytes(events[PSWPOUT]));
	186	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
	187	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
	188	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
	189	pages_to_bytes(i.freeram));
	190	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
	191	pages_to_bytes(i.totalram));
	192	}
	193
	194	/*
	195	* While most virtqueues communicate guest-initiated requests to the hypervisor,
	196	* the stats queue operates in reverse. The driver initializes the virtqueue
	197	* with a single buffer. From that point forward, all conversations consist of
	198	* a hypervisor request (a call to this function) which directs us to refill
1f34c71a AL	199	* the virtqueue with a fresh stats buffer. Since stats collection can sleep,
1f34c71a AL	200	* we notify our kthread which does the actual work via stats_handle_request().
9564e138	201	*/
1f34c71a	202	static void stats_request(struct virtqueue *vq)
9564e138 AL	203	{
	204	struct virtio_balloon *vb;
	205	unsigned int len;
9564e138 AL	206
	207	vb = vq->vq_ops->get_buf(vq, &len);
	208	if (!vb)
	209	return;
1f34c71a AL	210	vb->need_stats_update = 1;
	211	wake_up(&vb->config_change);
	212	}
	213
	214	static void stats_handle_request(struct virtio_balloon *vb)
	215	{
	216	struct virtqueue *vq;
	217	struct scatterlist sg;
9564e138	218
1f34c71a	219	vb->need_stats_update = 0;
9564e138 AL	220	update_balloon_stats(vb);
9564e138 AL	221
1f34c71a	222	vq = vb->stats_vq;
9564e138 AL	223	sg_init_one(&sg, vb->stats, sizeof(vb->stats));
	224	if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
	225	BUG();
	226	vq->vq_ops->kick(vq);
	227	}
	228
6b35e407 RR	229	static void virtballoon_changed(struct virtio_device *vdev)
	230	{
	231	struct virtio_balloon *vb = vdev->priv;
	232
	233	wake_up(&vb->config_change);
	234	}
	235
bdc1681c	236	static inline s64 towards_target(struct virtio_balloon *vb)
6b35e407 RR	237	{
6b35e407 RR	238	u32 v;
72e61eb4 RR	239	vb->vdev->config->get(vb->vdev,
	240	offsetof(struct virtio_balloon_config, num_pages),
	241	&v, sizeof(v));
532a6086	242	return (s64)v - vb->num_pages;
6b35e407 RR	243	}
	244
	245	static void update_balloon_size(struct virtio_balloon *vb)
	246	{
	247	__le32 actual = cpu_to_le32(vb->num_pages);
	248
	249	vb->vdev->config->set(vb->vdev,
	250	offsetof(struct virtio_balloon_config, actual),
	251	&actual, sizeof(actual));
	252	}
	253
	254	static int balloon(void *_vballoon)
	255	{
	256	struct virtio_balloon *vb = _vballoon;
	257
	258	set_freezable();
	259	while (!kthread_should_stop()) {
bdc1681c	260	s64 diff;
6b35e407 RR	261
	262	try_to_freeze();
	263	wait_event_interruptible(vb->config_change,
	264	(diff = towards_target(vb)) != 0
1f34c71a	265	\|\| vb->need_stats_update
84a139a9 MT	266	\|\| kthread_should_stop()
84a139a9 MT	267	\|\| freezing(current));
1f34c71a AL	268	if (vb->need_stats_update)
1f34c71a AL	269	stats_handle_request(vb);
6b35e407 RR	270	if (diff > 0)
	271	fill_balloon(vb, diff);
	272	else if (diff < 0)
	273	leak_balloon(vb, -diff);
	274	update_balloon_size(vb);
	275	}
	276	return 0;
	277	}
	278
	279	static int virtballoon_probe(struct virtio_device *vdev)
	280	{
	281	struct virtio_balloon *vb;
9564e138	282	struct virtqueue *vqs[3];
1f34c71a	283	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
9564e138 AL	284	const char *names[] = { "inflate", "deflate", "stats" };
9564e138 AL	285	int err, nvqs;
6b35e407 RR	286
	287	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
	288	if (!vb) {
	289	err = -ENOMEM;
	290	goto out;
	291	}
	292
	293	INIT_LIST_HEAD(&vb->pages);
	294	vb->num_pages = 0;
	295	init_waitqueue_head(&vb->config_change);
	296	vb->vdev = vdev;
169c246a	297	vb->need_stats_update = 0;
6b35e407	298
9564e138 AL	299	/* We expect two virtqueues: inflate and deflate,
	300	* and optionally stat. */
	301	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
	302	err = vdev->config->find_vqs(vdev, nvqs, vqs, callbacks, names);
d2a7ddda	303	if (err)
6b35e407	304	goto out_free_vb;
6b35e407	305
d2a7ddda MT	306	vb->inflate_vq = vqs[0];
d2a7ddda MT	307	vb->deflate_vq = vqs[1];
9564e138 AL	308	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
	309	struct scatterlist sg;
	310	vb->stats_vq = vqs[2];
	311
	312	/*
	313	* Prime this virtqueue with one buffer so the hypervisor can
	314	* use it to signal us later.
	315	*/
	316	sg_init_one(&sg, vb->stats, sizeof vb->stats);
	317	if (vb->stats_vq->vq_ops->add_buf(vb->stats_vq,
	318	&sg, 1, 0, vb) < 0)
	319	BUG();
	320	vb->stats_vq->vq_ops->kick(vb->stats_vq);
	321	}
6b35e407 RR	322
	323	vb->thread = kthread_run(balloon, vb, "vballoon");
	324	if (IS_ERR(vb->thread)) {
	325	err = PTR_ERR(vb->thread);
d2a7ddda	326	goto out_del_vqs;
6b35e407 RR	327	}
	328
	329	vb->tell_host_first
c45a6816	330	= virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
6b35e407 RR	331
	332	return 0;
	333
d2a7ddda MT	334	out_del_vqs:
d2a7ddda MT	335	vdev->config->del_vqs(vdev);
6b35e407 RR	336	out_free_vb:
	337	kfree(vb);
	338	out:
	339	return err;
	340	}
	341
1e65175c	342	static void __devexit virtballoon_remove(struct virtio_device *vdev)
6b35e407 RR	343	{
	344	struct virtio_balloon *vb = vdev->priv;
	345
	346	kthread_stop(vb->thread);
	347
	348	/* There might be pages left in the balloon: free them. */
	349	while (vb->num_pages)
	350	leak_balloon(vb, vb->num_pages);
	351
	352	/* Now we reset the device so we can clean up the queues. */
	353	vdev->config->reset(vdev);
	354
d2a7ddda	355	vdev->config->del_vqs(vdev);
6b35e407 RR	356	kfree(vb);
	357	}
	358
9564e138 AL	359	static unsigned int features[] = {
	360	VIRTIO_BALLOON_F_MUST_TELL_HOST,
	361	VIRTIO_BALLOON_F_STATS_VQ,
	362	};
c45a6816	363
d817cd52	364	static struct virtio_driver virtio_balloon_driver = {
c45a6816 RR	365	.feature_table = features,
c45a6816 RR	366	.feature_table_size = ARRAY_SIZE(features),
6b35e407 RR	367	.driver.name = KBUILD_MODNAME,
	368	.driver.owner = THIS_MODULE,
	369	.id_table = id_table,
	370	.probe = virtballoon_probe,
	371	.remove = __devexit_p(virtballoon_remove),
	372	.config_changed = virtballoon_changed,
	373	};
	374
	375	static int __init init(void)
	376	{
d817cd52	377	return register_virtio_driver(&virtio_balloon_driver);
6b35e407 RR	378	}
	379
	380	static void __exit fini(void)
	381	{
d817cd52	382	unregister_virtio_driver(&virtio_balloon_driver);
6b35e407 RR	383	}
	384	module_init(init);
	385	module_exit(fini);
	386
	387	MODULE_DEVICE_TABLE(virtio, id_table);
	388	MODULE_DESCRIPTION("Virtio balloon driver");
	389	MODULE_LICENSE("GPL");