[deliverable/linux.git] / drivers / xen / balloon.c

/******************************************************************************
 * balloon.c
 *
 * Xen balloon driver - enables returning/claiming memory to/from Xen.
 *
 * Copyright (c) 2003, B Dragovic
 * Copyright (c) 2003-2004, M Williamson, K Fraser
 * Copyright (c) 2005 Dan M. Smith, IBM Corporation
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/bootmem.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/sysdev.h>

#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/tlb.h>

#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>

#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/interface/memory.h>
#include <xen/xenbus.h>
#include <xen/features.h>
#include <xen/page.h>

#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))

#define BALLOON_CLASS_NAME "xen_memory"

struct balloon_stats {
	/* We aim for 'current allocation' == 'target allocation'. */
	unsigned long current_pages;
	unsigned long target_pages;
	/*
	 * Drivers may alter the memory reservation independently, but they
	 * must inform the balloon driver so we avoid hitting the hard limit.
	 */
	unsigned long driver_pages;
	/* Number of pages in high- and low-memory balloons. */
	unsigned long balloon_low;
	unsigned long balloon_high;
};

static DEFINE_MUTEX(balloon_mutex);

static struct sys_device balloon_sysdev;

static int register_balloon(struct sys_device *sysdev);

/*
 * Protects atomic reservation decrease/increase against concurrent increases.
 * Also protects non-atomic updates of current_pages and driver_pages, and
 * balloon lists.
 */
static DEFINE_SPINLOCK(balloon_lock);

static struct balloon_stats balloon_stats;

/* We increase/decrease in batches which fit in a page */
static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];

#ifdef CONFIG_HIGHMEM
#define inc_totalhigh_pages() (totalhigh_pages++)
#define dec_totalhigh_pages() (totalhigh_pages--)
#else
#define inc_totalhigh_pages() do {} while(0)
#define dec_totalhigh_pages() do {} while(0)
#endif

/* List of ballooned pages, threaded through the mem_map array. */
static LIST_HEAD(ballooned_pages);

/* Main work function, always executed in process context. */
static void balloon_process(struct work_struct *work);
static DECLARE_WORK(balloon_worker, balloon_process);
static struct timer_list balloon_timer;

/* When ballooning out (allocating memory to return to Xen) we don't really
   want the kernel to try too hard since that can trigger the oom killer. */
#define GFP_BALLOON \
	(GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)

static void scrub_page(struct page *page)
{
#ifdef CONFIG_XEN_SCRUB_PAGES
	clear_highpage(page);
#endif
}

/* balloon_append: add the given page to the balloon. */
static void balloon_append(struct page *page)
{
	/* Lowmem is re-populated first, so highmem pages go at list tail. */
	if (PageHighMem(page)) {
		list_add_tail(&page->lru, &ballooned_pages);
		balloon_stats.balloon_high++;
		dec_totalhigh_pages();
	} else {
		list_add(&page->lru, &ballooned_pages);
		balloon_stats.balloon_low++;
	}

	totalram_pages--;
}

/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
static struct page *balloon_retrieve(void)
{
	struct page *page;

	if (list_empty(&ballooned_pages))
		return NULL;

	page = list_entry(ballooned_pages.next, struct page, lru);
	list_del(&page->lru);

	if (PageHighMem(page)) {
		balloon_stats.balloon_high--;
		inc_totalhigh_pages();
	}
	else
		balloon_stats.balloon_low--;

	totalram_pages++;

	return page;
}

static struct page *balloon_first_page(void)
{
	if (list_empty(&ballooned_pages))
		return NULL;
	return list_entry(ballooned_pages.next, struct page, lru);
}

static struct page *balloon_next_page(struct page *page)
{
	struct list_head *next = page->lru.next;
	if (next == &ballooned_pages)
		return NULL;
	return list_entry(next, struct page, lru);
}

static void balloon_alarm(unsigned long unused)
{
	schedule_work(&balloon_worker);
}

static unsigned long current_target(void)
{
	unsigned long target = balloon_stats.target_pages;

	target = min(target,
		     balloon_stats.current_pages +
		     balloon_stats.balloon_low +
		     balloon_stats.balloon_high);

	return target;
}

static int increase_reservation(unsigned long nr_pages)
{
	unsigned long  pfn, i, flags;
	struct page   *page;
	long           rc;
	struct xen_memory_reservation reservation = {
		.address_bits = 0,
		.extent_order = 0,
		.domid        = DOMID_SELF
	};

	if (nr_pages > ARRAY_SIZE(frame_list))
		nr_pages = ARRAY_SIZE(frame_list);

	spin_lock_irqsave(&balloon_lock, flags);

	page = balloon_first_page();
	for (i = 0; i < nr_pages; i++) {
		BUG_ON(page == NULL);
		frame_list[i] = page_to_pfn(page);
		page = balloon_next_page(page);
	}

	set_xen_guest_handle(reservation.extent_start, frame_list);
	reservation.nr_extents = nr_pages;
	rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
	if (rc < 0)
		goto out;

	for (i = 0; i < rc; i++) {
		page = balloon_retrieve();
		BUG_ON(page == NULL);

		pfn = page_to_pfn(page);
		BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
		       phys_to_machine_mapping_valid(pfn));

		set_phys_to_machine(pfn, frame_list[i]);

		/* Link back into the page tables if not highmem. */
		if (pfn < max_low_pfn) {
			int ret;
			ret = HYPERVISOR_update_va_mapping(
				(unsigned long)__va(pfn << PAGE_SHIFT),
				mfn_pte(frame_list[i], PAGE_KERNEL),
				0);
			BUG_ON(ret);
		}

		/* Relinquish the page back to the allocator. */
		ClearPageReserved(page);
		init_page_count(page);
		__free_page(page);
	}

	balloon_stats.current_pages += rc;

 out:
	spin_unlock_irqrestore(&balloon_lock, flags);

	return rc < 0 ? rc : rc != nr_pages;
}

static int decrease_reservation(unsigned long nr_pages)
{
	unsigned long  pfn, i, flags;
	struct page   *page;
	int            need_sleep = 0;
	int ret;
	struct xen_memory_reservation reservation = {
		.address_bits = 0,
		.extent_order = 0,
		.domid        = DOMID_SELF
	};

	if (nr_pages > ARRAY_SIZE(frame_list))
		nr_pages = ARRAY_SIZE(frame_list);

	for (i = 0; i < nr_pages; i++) {
		if ((page = alloc_page(GFP_BALLOON)) == NULL) {
			nr_pages = i;
			need_sleep = 1;
			break;
		}

		pfn = page_to_pfn(page);
		frame_list[i] = pfn_to_mfn(pfn);

		scrub_page(page);

		if (!PageHighMem(page)) {
			ret = HYPERVISOR_update_va_mapping(
				(unsigned long)__va(pfn << PAGE_SHIFT),
				__pte_ma(0), 0);
			BUG_ON(ret);
                }

	}

	/* Ensure that ballooned highmem pages don't have kmaps. */
	kmap_flush_unused();
	flush_tlb_all();

	spin_lock_irqsave(&balloon_lock, flags);

	/* No more mappings: invalidate P2M and add to balloon. */
	for (i = 0; i < nr_pages; i++) {
		pfn = mfn_to_pfn(frame_list[i]);
		set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
		balloon_append(pfn_to_page(pfn));
	}

	set_xen_guest_handle(reservation.extent_start, frame_list);
	reservation.nr_extents   = nr_pages;
	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
	BUG_ON(ret != nr_pages);

	balloon_stats.current_pages -= nr_pages;

	spin_unlock_irqrestore(&balloon_lock, flags);

	return need_sleep;
}

/*
 * We avoid multiple worker processes conflicting via the balloon mutex.
 * We may of course race updates of the target counts (which are protected
 * by the balloon lock), or with changes to the Xen hard limit, but we will
 * recover from these in time.
 */
static void balloon_process(struct work_struct *work)
{
	int need_sleep = 0;
	long credit;

	mutex_lock(&balloon_mutex);

	do {
		credit = current_target() - balloon_stats.current_pages;
		if (credit > 0)
			need_sleep = (increase_reservation(credit) != 0);
		if (credit < 0)
			need_sleep = (decrease_reservation(-credit) != 0);

#ifndef CONFIG_PREEMPT
		if (need_resched())
			schedule();
#endif
	} while ((credit != 0) && !need_sleep);

	/* Schedule more work if there is some still to be done. */
	if (current_target() != balloon_stats.current_pages)
		mod_timer(&balloon_timer, jiffies + HZ);

	mutex_unlock(&balloon_mutex);
}

/* Resets the Xen limit, sets new target, and kicks off processing. */
static void balloon_set_new_target(unsigned long target)
{
	/* No need for lock. Not read-modify-write updates. */
	balloon_stats.target_pages = target;
	schedule_work(&balloon_worker);
}

static struct xenbus_watch target_watch =
{
	.node = "memory/target"
};

/* React to a change in the target key */
static void watch_target(struct xenbus_watch *watch,
			 const char **vec, unsigned int len)
{
	unsigned long long new_target;
	int err;

	err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
	if (err != 1) {
		/* This is ok (for domain0 at least) - so just return */
		return;
	}

	/* The given memory/target value is in KiB, so it needs converting to
	 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
	 */
	balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
}

static int balloon_init_watcher(struct notifier_block *notifier,
				unsigned long event,
				void *data)
{
	int err;

	err = register_xenbus_watch(&target_watch);
	if (err)
		printk(KERN_ERR "Failed to set balloon watcher\n");

	return NOTIFY_DONE;
}

static struct notifier_block xenstore_notifier;

static int __init balloon_init(void)
{
	unsigned long pfn;
	struct page *page;

	if (!xen_pv_domain())
		return -ENODEV;

	pr_info("xen_balloon: Initialising balloon driver.\n");

	balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
	balloon_stats.target_pages  = balloon_stats.current_pages;
	balloon_stats.balloon_low   = 0;
	balloon_stats.balloon_high  = 0;
	balloon_stats.driver_pages  = 0UL;

	init_timer(&balloon_timer);
	balloon_timer.data = 0;
	balloon_timer.function = balloon_alarm;

	register_balloon(&balloon_sysdev);

	/* Initialise the balloon with excess memory space. */
	for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
		page = pfn_to_page(pfn);
		if (!PageReserved(page))
			balloon_append(page);
	}

	target_watch.callback = watch_target;
	xenstore_notifier.notifier_call = balloon_init_watcher;

	register_xenstore_notifier(&xenstore_notifier);

	return 0;
}

subsys_initcall(balloon_init);

static void balloon_exit(void)
{
    /* XXX - release balloon here */
    return;
}

module_exit(balloon_exit);

#define BALLOON_SHOW(name, format, args...)				\
	static ssize_t show_##name(struct sys_device *dev,		\
				   struct sysdev_attribute *attr,	\
				   char *buf)				\
	{								\
		return sprintf(buf, format, ##args);			\
	}								\
	static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)

BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));

static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
			      char *buf)
{
	return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
}

static ssize_t store_target_kb(struct sys_device *dev,
			       struct sysdev_attribute *attr,
			       const char *buf,
			       size_t count)
{
	char *endchar;
	unsigned long long target_bytes;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;

	balloon_set_new_target(target_bytes >> PAGE_SHIFT);

	return count;
}

static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
		   show_target_kb, store_target_kb);


static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
			      char *buf)
{
	return sprintf(buf, "%llu\n",
		       (unsigned long long)balloon_stats.target_pages
		       << PAGE_SHIFT);
}

static ssize_t store_target(struct sys_device *dev,
			    struct sysdev_attribute *attr,
			    const char *buf,
			    size_t count)
{
	char *endchar;
	unsigned long long target_bytes;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	target_bytes = memparse(buf, &endchar);

	balloon_set_new_target(target_bytes >> PAGE_SHIFT);

	return count;
}

static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
		   show_target, store_target);


static struct sysdev_attribute *balloon_attrs[] = {
	&attr_target_kb,
	&attr_target,
};

static struct attribute *balloon_info_attrs[] = {
	&attr_current_kb.attr,
	&attr_low_kb.attr,
	&attr_high_kb.attr,
	&attr_driver_kb.attr,
	NULL
};

static struct attribute_group balloon_info_group = {
	.name = "info",
	.attrs = balloon_info_attrs,
};

static struct sysdev_class balloon_sysdev_class = {
	.name = BALLOON_CLASS_NAME,
};

static int register_balloon(struct sys_device *sysdev)
{
	int i, error;

	error = sysdev_class_register(&balloon_sysdev_class);
	if (error)
		return error;

	sysdev->id = 0;
	sysdev->cls = &balloon_sysdev_class;

	error = sysdev_register(sysdev);
	if (error) {
		sysdev_class_unregister(&balloon_sysdev_class);
		return error;
	}

	for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
		error = sysdev_create_file(sysdev, balloon_attrs[i]);
		if (error)
			goto fail;
	}

	error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
	if (error)
		goto fail;

	return 0;

 fail:
	while (--i >= 0)
		sysdev_remove_file(sysdev, balloon_attrs[i]);
	sysdev_unregister(sysdev);
	sysdev_class_unregister(&balloon_sysdev_class);
	return error;
}

MODULE_LICENSE("GPL");
Commit	Line	Data
1775826c JF	1	/******************************************************************************
	2	* balloon.c
	3	*
	4	* Xen balloon driver - enables returning/claiming memory to/from Xen.
	5	*
	6	* Copyright (c) 2003, B Dragovic
	7	* Copyright (c) 2003-2004, M Williamson, K Fraser
	8	* Copyright (c) 2005 Dan M. Smith, IBM Corporation
	9	*
	10	* This program is free software; you can redistribute it and/or
	11	* modify it under the terms of the GNU General Public License version 2
	12	* as published by the Free Software Foundation; or, when distributed
	13	* separately from the Linux kernel or incorporated into other
	14	* software packages, subject to the following license:
	15	*
	16	* Permission is hereby granted, free of charge, to any person obtaining a copy
	17	* of this source file (the "Software"), to deal in the Software without
	18	* restriction, including without limitation the rights to use, copy, modify,
	19	* merge, publish, distribute, sublicense, and/or sell copies of the Software,
	20	* and to permit persons to whom the Software is furnished to do so, subject to
	21	* the following conditions:
	22	*
	23	* The above copyright notice and this permission notice shall be included in
	24	* all copies or substantial portions of the Software.
	25	*
	26	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	27	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	28	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	29	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	30	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
	31	* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
	32	* IN THE SOFTWARE.
	33	*/
	34
	35	#include <linux/kernel.h>
	36	#include <linux/module.h>
	37	#include <linux/sched.h>
	38	#include <linux/errno.h>
	39	#include <linux/mm.h>
	40	#include <linux/bootmem.h>
	41	#include <linux/pagemap.h>
	42	#include <linux/highmem.h>
	43	#include <linux/mutex.h>
1775826c JF	44	#include <linux/list.h>
	45	#include <linux/sysdev.h>
	46
1775826c JF	47	#include <asm/page.h>
	48	#include <asm/pgalloc.h>
	49	#include <asm/pgtable.h>
	50	#include <asm/uaccess.h>
	51	#include <asm/tlb.h>
	52
ecbf29cd JF	53	#include <asm/xen/hypervisor.h>
ecbf29cd JF	54	#include <asm/xen/hypercall.h>
1ccbf534 JF	55
1ccbf534 JF	56	#include <xen/xen.h>
ecbf29cd	57	#include <xen/interface/xen.h>
1775826c	58	#include <xen/interface/memory.h>
1775826c JF	59	#include <xen/xenbus.h>
	60	#include <xen/features.h>
	61	#include <xen/page.h>
	62
	63	#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
	64
167e6cf6	65	#define BALLOON_CLASS_NAME "xen_memory"
1775826c JF	66
	67	struct balloon_stats {
	68	/* We aim for 'current allocation' == 'target allocation'. */
	69	unsigned long current_pages;
	70	unsigned long target_pages;
1775826c JF	71	/*
	72	* Drivers may alter the memory reservation independently, but they
	73	* must inform the balloon driver so we avoid hitting the hard limit.
	74	*/
	75	unsigned long driver_pages;
	76	/* Number of pages in high- and low-memory balloons. */
	77	unsigned long balloon_low;
	78	unsigned long balloon_high;
	79	};
	80
	81	static DEFINE_MUTEX(balloon_mutex);
	82
	83	static struct sys_device balloon_sysdev;
	84
	85	static int register_balloon(struct sys_device *sysdev);
	86
	87	/*
	88	* Protects atomic reservation decrease/increase against concurrent increases.
	89	* Also protects non-atomic updates of current_pages and driver_pages, and
	90	* balloon lists.
	91	*/
	92	static DEFINE_SPINLOCK(balloon_lock);
	93
	94	static struct balloon_stats balloon_stats;
	95
	96	/* We increase/decrease in batches which fit in a page */
	97	static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
	98
1775826c	99	#ifdef CONFIG_HIGHMEM
1775826c JF	100	#define inc_totalhigh_pages() (totalhigh_pages++)
	101	#define dec_totalhigh_pages() (totalhigh_pages--)
	102	#else
	103	#define inc_totalhigh_pages() do {} while(0)
	104	#define dec_totalhigh_pages() do {} while(0)
	105	#endif
	106
	107	/* List of ballooned pages, threaded through the mem_map array. */
	108	static LIST_HEAD(ballooned_pages);
	109
	110	/* Main work function, always executed in process context. */
	111	static void balloon_process(struct work_struct *work);
	112	static DECLARE_WORK(balloon_worker, balloon_process);
	113	static struct timer_list balloon_timer;
	114
	115	/* When ballooning out (allocating memory to return to Xen) we don't really
	116	want the kernel to try too hard since that can trigger the oom killer. */
	117	#define GFP_BALLOON \
	118	(GFP_HIGHUSER \| __GFP_NOWARN \| __GFP_NORETRY \| __GFP_NOMEMALLOC)
	119
	120	static void scrub_page(struct page *page)
	121	{
	122	#ifdef CONFIG_XEN_SCRUB_PAGES
26a3e991	123	clear_highpage(page);
1775826c JF	124	#endif
	125	}
	126
	127	/* balloon_append: add the given page to the balloon. */
	128	static void balloon_append(struct page *page)
	129	{
	130	/* Lowmem is re-populated first, so highmem pages go at list tail. */
	131	if (PageHighMem(page)) {
	132	list_add_tail(&page->lru, &ballooned_pages);
	133	balloon_stats.balloon_high++;
	134	dec_totalhigh_pages();
	135	} else {
	136	list_add(&page->lru, &ballooned_pages);
	137	balloon_stats.balloon_low++;
	138	}
3d65c948 GG	139
3d65c948 GG	140	totalram_pages--;
1775826c JF	141	}
	142
	143	/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
	144	static struct page *balloon_retrieve(void)
	145	{
	146	struct page *page;
	147
	148	if (list_empty(&ballooned_pages))
	149	return NULL;
	150
	151	page = list_entry(ballooned_pages.next, struct page, lru);
	152	list_del(&page->lru);
	153
	154	if (PageHighMem(page)) {
	155	balloon_stats.balloon_high--;
	156	inc_totalhigh_pages();
	157	}
	158	else
	159	balloon_stats.balloon_low--;
	160
3d65c948 GG	161	totalram_pages++;
3d65c948 GG	162
1775826c JF	163	return page;
	164	}
	165
	166	static struct page *balloon_first_page(void)
	167	{
	168	if (list_empty(&ballooned_pages))
	169	return NULL;
	170	return list_entry(ballooned_pages.next, struct page, lru);
	171	}
	172
	173	static struct page balloon_next_page(struct page page)
	174	{
	175	struct list_head *next = page->lru.next;
	176	if (next == &ballooned_pages)
	177	return NULL;
	178	return list_entry(next, struct page, lru);
	179	}
	180
	181	static void balloon_alarm(unsigned long unused)
	182	{
	183	schedule_work(&balloon_worker);
	184	}
	185
	186	static unsigned long current_target(void)
	187	{
bc2c0303	188	unsigned long target = balloon_stats.target_pages;
1775826c JF	189
	190	target = min(target,
	191	balloon_stats.current_pages +
	192	balloon_stats.balloon_low +
	193	balloon_stats.balloon_high);
	194
	195	return target;
	196	}
	197
	198	static int increase_reservation(unsigned long nr_pages)
	199	{
	200	unsigned long pfn, i, flags;
	201	struct page *page;
	202	long rc;
	203	struct xen_memory_reservation reservation = {
	204	.address_bits = 0,
	205	.extent_order = 0,
	206	.domid = DOMID_SELF
	207	};
	208
	209	if (nr_pages > ARRAY_SIZE(frame_list))
	210	nr_pages = ARRAY_SIZE(frame_list);
	211
	212	spin_lock_irqsave(&balloon_lock, flags);
	213
	214	page = balloon_first_page();
	215	for (i = 0; i < nr_pages; i++) {
	216	BUG_ON(page == NULL);
a419aef8	217	frame_list[i] = page_to_pfn(page);
1775826c JF	218	page = balloon_next_page(page);
	219	}
	220
a90971eb	221	set_xen_guest_handle(reservation.extent_start, frame_list);
fde28e8f JF	222	reservation.nr_extents = nr_pages;
fde28e8f JF	223	rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
bc2c0303	224	if (rc < 0)
1775826c	225	goto out;
1775826c	226
bc2c0303	227	for (i = 0; i < rc; i++) {
1775826c JF	228	page = balloon_retrieve();
	229	BUG_ON(page == NULL);
	230
	231	pfn = page_to_pfn(page);
	232	BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
	233	phys_to_machine_mapping_valid(pfn));
	234
	235	set_phys_to_machine(pfn, frame_list[i]);
	236
	237	/* Link back into the page tables if not highmem. */
	238	if (pfn < max_low_pfn) {
	239	int ret;
	240	ret = HYPERVISOR_update_va_mapping(
	241	(unsigned long)__va(pfn << PAGE_SHIFT),
	242	mfn_pte(frame_list[i], PAGE_KERNEL),
	243	0);
	244	BUG_ON(ret);
	245	}
	246
	247	/* Relinquish the page back to the allocator. */
	248	ClearPageReserved(page);
	249	init_page_count(page);
	250	__free_page(page);
	251	}
	252
bc2c0303	253	balloon_stats.current_pages += rc;
1775826c JF	254
	255	out:
	256	spin_unlock_irqrestore(&balloon_lock, flags);
	257
bc2c0303	258	return rc < 0 ? rc : rc != nr_pages;
1775826c JF	259	}
	260
	261	static int decrease_reservation(unsigned long nr_pages)
	262	{
	263	unsigned long pfn, i, flags;
	264	struct page *page;
	265	int need_sleep = 0;
	266	int ret;
	267	struct xen_memory_reservation reservation = {
	268	.address_bits = 0,
	269	.extent_order = 0,
	270	.domid = DOMID_SELF
	271	};
	272
	273	if (nr_pages > ARRAY_SIZE(frame_list))
	274	nr_pages = ARRAY_SIZE(frame_list);
	275
	276	for (i = 0; i < nr_pages; i++) {
	277	if ((page = alloc_page(GFP_BALLOON)) == NULL) {
	278	nr_pages = i;
	279	need_sleep = 1;
	280	break;
	281	}
	282
	283	pfn = page_to_pfn(page);
	284	frame_list[i] = pfn_to_mfn(pfn);
	285
	286	scrub_page(page);
1058a75f	287
ff4ce8c3 IC	288	if (!PageHighMem(page)) {
	289	ret = HYPERVISOR_update_va_mapping(
	290	(unsigned long)__va(pfn << PAGE_SHIFT),
	291	__pte_ma(0), 0);
	292	BUG_ON(ret);
	293	}
	294
1775826c JF	295	}
	296
	297	/* Ensure that ballooned highmem pages don't have kmaps. */
	298	kmap_flush_unused();
	299	flush_tlb_all();
	300
	301	spin_lock_irqsave(&balloon_lock, flags);
	302
	303	/* No more mappings: invalidate P2M and add to balloon. */
	304	for (i = 0; i < nr_pages; i++) {
	305	pfn = mfn_to_pfn(frame_list[i]);
	306	set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
	307	balloon_append(pfn_to_page(pfn));
	308	}
	309
a90971eb	310	set_xen_guest_handle(reservation.extent_start, frame_list);
1775826c JF	311	reservation.nr_extents = nr_pages;
	312	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
	313	BUG_ON(ret != nr_pages);
	314
	315	balloon_stats.current_pages -= nr_pages;
1775826c JF	316
	317	spin_unlock_irqrestore(&balloon_lock, flags);
	318
	319	return need_sleep;
	320	}
	321
	322	/*
	323	* We avoid multiple worker processes conflicting via the balloon mutex.
	324	* We may of course race updates of the target counts (which are protected
	325	* by the balloon lock), or with changes to the Xen hard limit, but we will
	326	* recover from these in time.
	327	*/
	328	static void balloon_process(struct work_struct *work)
	329	{
	330	int need_sleep = 0;
	331	long credit;
	332
	333	mutex_lock(&balloon_mutex);
	334
	335	do {
	336	credit = current_target() - balloon_stats.current_pages;
	337	if (credit > 0)
	338	need_sleep = (increase_reservation(credit) != 0);
	339	if (credit < 0)
	340	need_sleep = (decrease_reservation(-credit) != 0);
	341
	342	#ifndef CONFIG_PREEMPT
	343	if (need_resched())
	344	schedule();
	345	#endif
	346	} while ((credit != 0) && !need_sleep);
	347
	348	/* Schedule more work if there is some still to be done. */
	349	if (current_target() != balloon_stats.current_pages)
	350	mod_timer(&balloon_timer, jiffies + HZ);
	351
	352	mutex_unlock(&balloon_mutex);
	353	}
	354
	355	/* Resets the Xen limit, sets new target, and kicks off processing. */
955d6f17	356	static void balloon_set_new_target(unsigned long target)
1775826c JF	357	{
1775826c JF	358	/* No need for lock. Not read-modify-write updates. */
1775826c JF	359	balloon_stats.target_pages = target;
	360	schedule_work(&balloon_worker);
	361	}
	362
	363	static struct xenbus_watch target_watch =
	364	{
	365	.node = "memory/target"
	366	};
	367
	368	/* React to a change in the target key */
	369	static void watch_target(struct xenbus_watch *watch,
	370	const char **vec, unsigned int len)
	371	{
	372	unsigned long long new_target;
	373	int err;
	374
	375	err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
	376	if (err != 1) {
	377	/* This is ok (for domain0 at least) - so just return */
	378	return;
	379	}
	380
	381	/* The given memory/target value is in KiB, so it needs converting to
	382	* pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
	383	*/
	384	balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
	385	}
	386
	387	static int balloon_init_watcher(struct notifier_block *notifier,
	388	unsigned long event,
	389	void *data)
	390	{
	391	int err;
	392
	393	err = register_xenbus_watch(&target_watch);
	394	if (err)
	395	printk(KERN_ERR "Failed to set balloon watcher\n");
	396
	397	return NOTIFY_DONE;
	398	}
	399
	400	static struct notifier_block xenstore_notifier;
	401
	402	static int __init balloon_init(void)
	403	{
	404	unsigned long pfn;
	405	struct page *page;
	406
6e833587	407	if (!xen_pv_domain())
1775826c JF	408	return -ENODEV;
	409
	410	pr_info("xen_balloon: Initialising balloon driver.\n");
	411
	412	balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
1775826c JF	413	balloon_stats.target_pages = balloon_stats.current_pages;
	414	balloon_stats.balloon_low = 0;
	415	balloon_stats.balloon_high = 0;
	416	balloon_stats.driver_pages = 0UL;
1775826c JF	417
	418	init_timer(&balloon_timer);
	419	balloon_timer.data = 0;
	420	balloon_timer.function = balloon_alarm;
	421
	422	register_balloon(&balloon_sysdev);
	423
	424	/* Initialise the balloon with excess memory space. */
	425	for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
	426	page = pfn_to_page(pfn);
	427	if (!PageReserved(page))
	428	balloon_append(page);
	429	}
	430
	431	target_watch.callback = watch_target;
	432	xenstore_notifier.notifier_call = balloon_init_watcher;
	433
	434	register_xenstore_notifier(&xenstore_notifier);
	435
	436	return 0;
	437	}
	438
	439	subsys_initcall(balloon_init);
	440
	441	static void balloon_exit(void)
	442	{
	443	/* XXX - release balloon here */
	444	return;
	445	}
	446
	447	module_exit(balloon_exit);
	448
167e6cf6 JF	449	#define BALLOON_SHOW(name, format, args...) \
	450	static ssize_t show_##name(struct sys_device *dev, \
	451	struct sysdev_attribute *attr, \
	452	char *buf) \
	453	{ \
	454	return sprintf(buf, format, ##args); \
	455	} \
1775826c JF	456	static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
	457
	458	BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
	459	BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
	460	BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
1775826c JF	461	BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
1775826c JF	462
167e6cf6 JF	463	static ssize_t show_target_kb(struct sys_device dev, struct sysdev_attribute attr,
167e6cf6 JF	464	char *buf)
1775826c JF	465	{
	466	return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
	467	}
	468
	469	static ssize_t store_target_kb(struct sys_device *dev,
4a0b2b4d	470	struct sysdev_attribute *attr,
1775826c JF	471	const char *buf,
	472	size_t count)
	473	{
167e6cf6	474	char *endchar;
1775826c JF	475	unsigned long long target_bytes;
	476
	477	if (!capable(CAP_SYS_ADMIN))
	478	return -EPERM;
	479
618b2c8d	480	target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
1775826c	481
1775826c JF	482	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
	483
	484	return count;
	485	}
	486
	487	static SYSDEV_ATTR(target_kb, S_IRUGO \| S_IWUSR,
	488	show_target_kb, store_target_kb);
	489
618b2c8d JF	490
	491	static ssize_t show_target(struct sys_device dev, struct sysdev_attribute attr,
	492	char *buf)
	493	{
	494	return sprintf(buf, "%llu\n",
0692698c JB	495	(unsigned long long)balloon_stats.target_pages
0692698c JB	496	<< PAGE_SHIFT);
618b2c8d JF	497	}
	498
	499	static ssize_t store_target(struct sys_device *dev,
	500	struct sysdev_attribute *attr,
	501	const char *buf,
	502	size_t count)
	503	{
	504	char *endchar;
	505	unsigned long long target_bytes;
	506
	507	if (!capable(CAP_SYS_ADMIN))
	508	return -EPERM;
	509
	510	target_bytes = memparse(buf, &endchar);
	511
	512	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
	513
	514	return count;
	515	}
	516
	517	static SYSDEV_ATTR(target, S_IRUGO \| S_IWUSR,
	518	show_target, store_target);
	519
	520
1775826c JF	521	static struct sysdev_attribute *balloon_attrs[] = {
1775826c JF	522	&attr_target_kb,
618b2c8d	523	&attr_target,
1775826c JF	524	};
	525
	526	static struct attribute *balloon_info_attrs[] = {
	527	&attr_current_kb.attr,
	528	&attr_low_kb.attr,
	529	&attr_high_kb.attr,
1775826c JF	530	&attr_driver_kb.attr,
	531	NULL
	532	};
	533
	534	static struct attribute_group balloon_info_group = {
	535	.name = "info",
	536	.attrs = balloon_info_attrs,
	537	};
	538
	539	static struct sysdev_class balloon_sysdev_class = {
	540	.name = BALLOON_CLASS_NAME,
	541	};
	542
	543	static int register_balloon(struct sys_device *sysdev)
	544	{
	545	int i, error;
	546
	547	error = sysdev_class_register(&balloon_sysdev_class);
	548	if (error)
	549	return error;
	550
	551	sysdev->id = 0;
	552	sysdev->cls = &balloon_sysdev_class;
	553
	554	error = sysdev_register(sysdev);
	555	if (error) {
	556	sysdev_class_unregister(&balloon_sysdev_class);
	557	return error;
	558	}
	559
	560	for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
	561	error = sysdev_create_file(sysdev, balloon_attrs[i]);
	562	if (error)
	563	goto fail;
	564	}
	565
	566	error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
	567	if (error)
	568	goto fail;
	569
	570	return 0;
	571
	572	fail:
	573	while (--i >= 0)
	574	sysdev_remove_file(sysdev, balloon_attrs[i]);
	575	sysdev_unregister(sysdev);
	576	sysdev_class_unregister(&balloon_sysdev_class);
	577	return error;
	578	}
	579
1775826c	580	MODULE_LICENSE("GPL");