[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>

/*
 * Balloon device works in 4K page units.  So each page is pointed to by
 * multiple balloon pages.  All memory counters in this driver are in balloon
 * page units.
 */
#define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)

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;

	/* Number of balloon pages we've told the Host we're not using. */
	unsigned int num_pages;
	/*
	 * The pages we've told the Host we're not using.
	 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
	 * to num_pages above.
	 */
	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 * VIRTIO_BALLOON_PAGES_PER_PAGE;
}

static struct page *balloon_pfn_to_page(u32 pfn)
{
	BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
	return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
}

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 set_page_pfns(u32 pfns[], struct page *page)
{
	unsigned int i;

	/* Set balloon pfns pointing at this page.
	 * Note that the first pfn points at start of the page. */
	for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
		pfns[i] = page_to_balloon_pfn(page) + i;
}

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 += VIRTIO_BALLOON_PAGES_PER_PAGE) {
		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;
		}
		set_page_pfns(vb->pfns + vb->num_pfns, page);
		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
		totalram_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;

	/* Find pfns pointing at start of each page, get pages and free them. */
	for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
		__free_page(balloon_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 += VIRTIO_BALLOON_PAGES_PER_PAGE) {
		page = list_first_entry(&vb->pages, struct page, lru);
		list_del(&page->lru);
		set_page_pfns(vb->pfns + vb->num_pfns, page);
		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
	}

	/*
	 * 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	30
3ccc9372 MT	31	/*
	32	* Balloon device works in 4K page units. So each page is pointed to by
	33	* multiple balloon pages. All memory counters in this driver are in balloon
	34	* page units.
	35	*/
	36	#define VIRTIO_BALLOON_PAGES_PER_PAGE (PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
	37
6b35e407 RR	38	struct virtio_balloon
	39	{
	40	struct virtio_device *vdev;
9564e138	41	struct virtqueue inflate_vq, deflate_vq, *stats_vq;
6b35e407 RR	42
	43	/* Where the ballooning thread waits for config to change. */
	44	wait_queue_head_t config_change;
	45
	46	/* The thread servicing the balloon. */
	47	struct task_struct *thread;
	48
	49	/* Waiting for host to ack the pages we released. */
	50	struct completion acked;
	51
3ccc9372	52	/* Number of balloon pages we've told the Host we're not using. */
6b35e407	53	unsigned int num_pages;
3ccc9372 MT	54	/*
	55	* The pages we've told the Host we're not using.
	56	* Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
	57	* to num_pages above.
	58	*/
6b35e407 RR	59	struct list_head pages;
	60
	61	/* The array of pfns we tell the Host about. */
	62	unsigned int num_pfns;
	63	u32 pfns[256];
9564e138 AL	64
9564e138 AL	65	/* Memory statistics */
1f34c71a	66	int need_stats_update;
9564e138	67	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
6b35e407 RR	68	};
	69
	70	static struct virtio_device_id id_table[] = {
	71	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
	72	{ 0 },
	73	};
	74
1b4aa2fa HB	75	static u32 page_to_balloon_pfn(struct page *page)
	76	{
	77	unsigned long pfn = page_to_pfn(page);
	78
	79	BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
	80	/* Convert pfn from Linux page size to balloon page size. */
3ccc9372 MT	81	return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
	82	}
	83
	84	static struct page *balloon_pfn_to_page(u32 pfn)
	85	{
	86	BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
	87	return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
1b4aa2fa HB	88	}
1b4aa2fa HB	89
6b35e407 RR	90	static void balloon_ack(struct virtqueue *vq)
	91	{
	92	struct virtio_balloon *vb;
	93	unsigned int len;
	94
946cfe0e	95	vb = virtqueue_get_buf(vq, &len);
6b35e407 RR	96	if (vb)
	97	complete(&vb->acked);
	98	}
	99
	100	static void tell_host(struct virtio_balloon vb, struct virtqueue vq)
	101	{
	102	struct scatterlist sg;
	103
	104	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
	105
	106	init_completion(&vb->acked);
	107
	108	/* We should always be able to add one buffer to an empty queue. */
f96fde41	109	if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
6b35e407	110	BUG();
946cfe0e	111	virtqueue_kick(vq);
6b35e407 RR	112
	113	/* When host has read buffer, this completes via balloon_ack */
	114	wait_for_completion(&vb->acked);
	115	}
	116
3ccc9372 MT	117	static void set_page_pfns(u32 pfns[], struct page *page)
	118	{
	119	unsigned int i;
	120
	121	/* Set balloon pfns pointing at this page.
	122	* Note that the first pfn points at start of the page. */
	123	for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
	124	pfns[i] = page_to_balloon_pfn(page) + i;
	125	}
	126
6b35e407 RR	127	static void fill_balloon(struct virtio_balloon *vb, size_t num)
	128	{
	129	/* We can only do one array worth at a time. */
	130	num = min(num, ARRAY_SIZE(vb->pfns));
	131
3ccc9372 MT	132	for (vb->num_pfns = 0; vb->num_pfns < num;
3ccc9372 MT	133	vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
61fb06cc BS	134	struct page *page = alloc_page(GFP_HIGHUSER \| __GFP_NORETRY \|
61fb06cc BS	135	__GFP_NOMEMALLOC \| __GFP_NOWARN);
6b35e407 RR	136	if (!page) {
	137	if (printk_ratelimit())
	138	dev_printk(KERN_INFO, &vb->vdev->dev,
	139	"Out of puff! Can't get %zu pages\n",
	140	num);
	141	/* Sleep for at least 1/5 of a second before retry. */
	142	msleep(200);
	143	break;
	144	}
3ccc9372 MT	145	set_page_pfns(vb->pfns + vb->num_pfns, page);
3ccc9372 MT	146	vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
6b35e407	147	totalram_pages--;
6b35e407 RR	148	list_add(&page->lru, &vb->pages);
	149	}
	150
	151	/* Didn't get any? Oh well. */
	152	if (vb->num_pfns == 0)
	153	return;
	154
	155	tell_host(vb, vb->inflate_vq);
	156	}
	157
	158	static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
	159	{
	160	unsigned int i;
	161
3ccc9372 MT	162	/* Find pfns pointing at start of each page, get pages and free them. */
	163	for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
	164	__free_page(balloon_pfn_to_page(pfns[i]));
6b35e407 RR	165	totalram_pages++;
	166	}
	167	}
	168
	169	static void leak_balloon(struct virtio_balloon *vb, size_t num)
	170	{
	171	struct page *page;
	172
	173	/* We can only do one array worth at a time. */
	174	num = min(num, ARRAY_SIZE(vb->pfns));
	175
3ccc9372 MT	176	for (vb->num_pfns = 0; vb->num_pfns < num;
3ccc9372 MT	177	vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
6b35e407 RR	178	page = list_first_entry(&vb->pages, struct page, lru);
6b35e407 RR	179	list_del(&page->lru);
3ccc9372 MT	180	set_page_pfns(vb->pfns + vb->num_pfns, page);
3ccc9372 MT	181	vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
6b35e407 RR	182	}
6b35e407 RR	183
bf50e69f DH	184	/*
	185	* Note that if
	186	* virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
	187	* is true, we have to do it in this order
	188	*/
	189	tell_host(vb, vb->deflate_vq);
	190	release_pages_by_pfn(vb->pfns, vb->num_pfns);
6b35e407 RR	191	}
6b35e407 RR	192
9564e138 AL	193	static inline void update_stat(struct virtio_balloon *vb, int idx,
	194	u16 tag, u64 val)
	195	{
	196	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
	197	vb->stats[idx].tag = tag;
	198	vb->stats[idx].val = val;
	199	}
	200
	201	#define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
	202
	203	static void update_balloon_stats(struct virtio_balloon *vb)
	204	{
	205	unsigned long events[NR_VM_EVENT_ITEMS];
	206	struct sysinfo i;
	207	int idx = 0;
	208
	209	all_vm_events(events);
	210	si_meminfo(&i);
	211
	212	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
	213	pages_to_bytes(events[PSWPIN]));
	214	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
	215	pages_to_bytes(events[PSWPOUT]));
	216	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
	217	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
	218	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
	219	pages_to_bytes(i.freeram));
	220	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
	221	pages_to_bytes(i.totalram));
	222	}
	223
	224	/*
	225	* While most virtqueues communicate guest-initiated requests to the hypervisor,
	226	* the stats queue operates in reverse. The driver initializes the virtqueue
	227	* with a single buffer. From that point forward, all conversations consist of
	228	* a hypervisor request (a call to this function) which directs us to refill
1f34c71a AL	229	* the virtqueue with a fresh stats buffer. Since stats collection can sleep,
1f34c71a AL	230	* we notify our kthread which does the actual work via stats_handle_request().
9564e138	231	*/
1f34c71a	232	static void stats_request(struct virtqueue *vq)
9564e138 AL	233	{
	234	struct virtio_balloon *vb;
	235	unsigned int len;
9564e138	236
946cfe0e	237	vb = virtqueue_get_buf(vq, &len);
9564e138 AL	238	if (!vb)
9564e138 AL	239	return;
1f34c71a AL	240	vb->need_stats_update = 1;
	241	wake_up(&vb->config_change);
	242	}
	243
	244	static void stats_handle_request(struct virtio_balloon *vb)
	245	{
	246	struct virtqueue *vq;
	247	struct scatterlist sg;
9564e138	248
1f34c71a	249	vb->need_stats_update = 0;
9564e138 AL	250	update_balloon_stats(vb);
9564e138 AL	251
1f34c71a	252	vq = vb->stats_vq;
9564e138	253	sg_init_one(&sg, vb->stats, sizeof(vb->stats));
f96fde41	254	if (virtqueue_add_buf(vq, &sg, 1, 0, vb, GFP_KERNEL) < 0)
9564e138	255	BUG();
946cfe0e	256	virtqueue_kick(vq);
9564e138 AL	257	}
9564e138 AL	258
6b35e407 RR	259	static void virtballoon_changed(struct virtio_device *vdev)
	260	{
	261	struct virtio_balloon *vb = vdev->priv;
	262
	263	wake_up(&vb->config_change);
	264	}
	265
bdc1681c	266	static inline s64 towards_target(struct virtio_balloon *vb)
6b35e407	267	{
1a87228f DG	268	__le32 v;
	269	s64 target;
	270
72e61eb4 RR	271	vb->vdev->config->get(vb->vdev,
	272	offsetof(struct virtio_balloon_config, num_pages),
	273	&v, sizeof(v));
1a87228f DG	274	target = le32_to_cpu(v);
1a87228f DG	275	return target - vb->num_pages;
6b35e407 RR	276	}
	277
	278	static void update_balloon_size(struct virtio_balloon *vb)
	279	{
	280	__le32 actual = cpu_to_le32(vb->num_pages);
	281
	282	vb->vdev->config->set(vb->vdev,
	283	offsetof(struct virtio_balloon_config, actual),
	284	&actual, sizeof(actual));
	285	}
	286
	287	static int balloon(void *_vballoon)
	288	{
	289	struct virtio_balloon *vb = _vballoon;
	290
	291	set_freezable();
	292	while (!kthread_should_stop()) {
bdc1681c	293	s64 diff;
6b35e407 RR	294
	295	try_to_freeze();
	296	wait_event_interruptible(vb->config_change,
	297	(diff = towards_target(vb)) != 0
1f34c71a	298	\|\| vb->need_stats_update
84a139a9 MT	299	\|\| kthread_should_stop()
84a139a9 MT	300	\|\| freezing(current));
1f34c71a AL	301	if (vb->need_stats_update)
1f34c71a AL	302	stats_handle_request(vb);
6b35e407 RR	303	if (diff > 0)
	304	fill_balloon(vb, diff);
	305	else if (diff < 0)
	306	leak_balloon(vb, -diff);
	307	update_balloon_size(vb);
	308	}
	309	return 0;
	310	}
	311
be91c33d	312	static int init_vqs(struct virtio_balloon *vb)
6b35e407	313	{
9564e138	314	struct virtqueue *vqs[3];
1f34c71a	315	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
9564e138 AL	316	const char *names[] = { "inflate", "deflate", "stats" };
9564e138 AL	317	int err, nvqs;
6b35e407	318
be91c33d AS	319	/*
	320	* We expect two virtqueues: inflate and deflate, and
	321	* optionally stat.
	322	*/
9564e138	323	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
be91c33d	324	err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
d2a7ddda	325	if (err)
be91c33d	326	return err;
6b35e407	327
d2a7ddda MT	328	vb->inflate_vq = vqs[0];
d2a7ddda MT	329	vb->deflate_vq = vqs[1];
9564e138 AL	330	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
	331	struct scatterlist sg;
	332	vb->stats_vq = vqs[2];
	333
	334	/*
	335	* Prime this virtqueue with one buffer so the hypervisor can
	336	* use it to signal us later.
	337	*/
	338	sg_init_one(&sg, vb->stats, sizeof vb->stats);
f96fde41 RR	339	if (virtqueue_add_buf(vb->stats_vq, &sg, 1, 0, vb, GFP_KERNEL)
f96fde41 RR	340	< 0)
9564e138	341	BUG();
946cfe0e	342	virtqueue_kick(vb->stats_vq);
9564e138	343	}
be91c33d AS	344	return 0;
	345	}
	346
	347	static int virtballoon_probe(struct virtio_device *vdev)
	348	{
	349	struct virtio_balloon *vb;
	350	int err;
	351
	352	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
	353	if (!vb) {
	354	err = -ENOMEM;
	355	goto out;
	356	}
	357
	358	INIT_LIST_HEAD(&vb->pages);
	359	vb->num_pages = 0;
	360	init_waitqueue_head(&vb->config_change);
	361	vb->vdev = vdev;
	362	vb->need_stats_update = 0;
	363
	364	err = init_vqs(vb);
	365	if (err)
	366	goto out_free_vb;
6b35e407 RR	367
	368	vb->thread = kthread_run(balloon, vb, "vballoon");
	369	if (IS_ERR(vb->thread)) {
	370	err = PTR_ERR(vb->thread);
d2a7ddda	371	goto out_del_vqs;
6b35e407 RR	372	}
6b35e407 RR	373
6b35e407 RR	374	return 0;
6b35e407 RR	375
d2a7ddda MT	376	out_del_vqs:
d2a7ddda MT	377	vdev->config->del_vqs(vdev);
6b35e407 RR	378	out_free_vb:
	379	kfree(vb);
	380	out:
	381	return err;
	382	}
	383
1e65175c	384	static void __devexit virtballoon_remove(struct virtio_device *vdev)
6b35e407 RR	385	{
	386	struct virtio_balloon *vb = vdev->priv;
	387
	388	kthread_stop(vb->thread);
	389
	390	/* There might be pages left in the balloon: free them. */
	391	while (vb->num_pages)
	392	leak_balloon(vb, vb->num_pages);
	393
	394	/* Now we reset the device so we can clean up the queues. */
	395	vdev->config->reset(vdev);
	396
d2a7ddda	397	vdev->config->del_vqs(vdev);
6b35e407 RR	398	kfree(vb);
	399	}
	400
e562966d AS	401	#ifdef CONFIG_PM
	402	static int virtballoon_freeze(struct virtio_device *vdev)
	403	{
4eb05d56 AS	404	struct virtio_balloon *vb = vdev->priv;
4eb05d56 AS	405
e562966d AS	406	/*
	407	* The kthread is already frozen by the PM core before this
	408	* function is called.
	409	*/
	410
4eb05d56 AS	411	while (vb->num_pages)
	412	leak_balloon(vb, vb->num_pages);
	413	update_balloon_size(vb);
	414
e562966d AS	415	/* Ensure we don't get any more requests from the host */
	416	vdev->config->reset(vdev);
	417	vdev->config->del_vqs(vdev);
	418	return 0;
	419	}
	420
4eb05d56 AS	421	static int restore_common(struct virtio_device *vdev)
	422	{
	423	struct virtio_balloon *vb = vdev->priv;
	424	int ret;
	425
	426	ret = init_vqs(vdev->priv);
	427	if (ret)
	428	return ret;
	429
	430	fill_balloon(vb, towards_target(vb));
	431	update_balloon_size(vb);
	432	return 0;
	433	}
	434
e562966d AS	435	static int virtballoon_restore(struct virtio_device *vdev)
e562966d AS	436	{
4eb05d56	437	return restore_common(vdev);
e562966d AS	438	}
	439	#endif
	440
9564e138 AL	441	static unsigned int features[] = {
	442	VIRTIO_BALLOON_F_MUST_TELL_HOST,
	443	VIRTIO_BALLOON_F_STATS_VQ,
	444	};
c45a6816	445
d817cd52	446	static struct virtio_driver virtio_balloon_driver = {
c45a6816 RR	447	.feature_table = features,
c45a6816 RR	448	.feature_table_size = ARRAY_SIZE(features),
6b35e407 RR	449	.driver.name = KBUILD_MODNAME,
	450	.driver.owner = THIS_MODULE,
	451	.id_table = id_table,
	452	.probe = virtballoon_probe,
	453	.remove = __devexit_p(virtballoon_remove),
	454	.config_changed = virtballoon_changed,
e562966d AS	455	#ifdef CONFIG_PM
	456	.freeze = virtballoon_freeze,
	457	.restore = virtballoon_restore,
e562966d	458	#endif
6b35e407 RR	459	};
	460
	461	static int __init init(void)
	462	{
d817cd52	463	return register_virtio_driver(&virtio_balloon_driver);
6b35e407 RR	464	}
	465
	466	static void __exit fini(void)
	467	{
d817cd52	468	unregister_virtio_driver(&virtio_balloon_driver);
6b35e407 RR	469	}
	470	module_init(init);
	471	module_exit(fini);
	472
	473	MODULE_DEVICE_TABLE(virtio, id_table);
	474	MODULE_DESCRIPTION("Virtio balloon driver");
	475	MODULE_LICENSE("GPL");