[GitHub/mt8127/android_kernel_alcatel_ttab.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, *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 */
	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);
		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.
 */
static void stats_ack(struct virtqueue *vq)
{
	struct virtio_balloon *vb;
	unsigned int len;
	struct scatterlist sg;

	vb = vq->vq_ops->get_buf(vq, &len);
	if (!vb)
		return;

	update_balloon_stats(vb);

	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
					 || 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[3];
	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_ack };
	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;

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