[mirror_ubuntu-hirsute-kernel.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 <linux/gfp.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>
1775826c JF	45	#include <linux/sysdev.h>
5a0e3ad6	46	#include <linux/gfp.h>
1775826c	47
1775826c JF	48	#include <asm/page.h>
	49	#include <asm/pgalloc.h>
	50	#include <asm/pgtable.h>
	51	#include <asm/uaccess.h>
	52	#include <asm/tlb.h>
	53
ecbf29cd JF	54	#include <asm/xen/hypervisor.h>
ecbf29cd JF	55	#include <asm/xen/hypercall.h>
1ccbf534 JF	56
1ccbf534 JF	57	#include <xen/xen.h>
ecbf29cd	58	#include <xen/interface/xen.h>
1775826c	59	#include <xen/interface/memory.h>
1775826c JF	60	#include <xen/xenbus.h>
	61	#include <xen/features.h>
	62	#include <xen/page.h>
	63
	64	#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
	65
167e6cf6	66	#define BALLOON_CLASS_NAME "xen_memory"
1775826c JF	67
	68	struct balloon_stats {
	69	/* We aim for 'current allocation' == 'target allocation'. */
	70	unsigned long current_pages;
	71	unsigned long target_pages;
1775826c JF	72	/*
	73	* Drivers may alter the memory reservation independently, but they
	74	* must inform the balloon driver so we avoid hitting the hard limit.
	75	*/
	76	unsigned long driver_pages;
	77	/* Number of pages in high- and low-memory balloons. */
	78	unsigned long balloon_low;
	79	unsigned long balloon_high;
	80	};
	81
	82	static DEFINE_MUTEX(balloon_mutex);
	83
	84	static struct sys_device balloon_sysdev;
	85
	86	static int register_balloon(struct sys_device *sysdev);
	87
	88	/*
	89	* Protects atomic reservation decrease/increase against concurrent increases.
	90	* Also protects non-atomic updates of current_pages and driver_pages, and
	91	* balloon lists.
	92	*/
	93	static DEFINE_SPINLOCK(balloon_lock);
	94
	95	static struct balloon_stats balloon_stats;
	96
	97	/* We increase/decrease in batches which fit in a page */
	98	static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
	99
1775826c	100	#ifdef CONFIG_HIGHMEM
1775826c JF	101	#define inc_totalhigh_pages() (totalhigh_pages++)
	102	#define dec_totalhigh_pages() (totalhigh_pages--)
	103	#else
	104	#define inc_totalhigh_pages() do {} while(0)
	105	#define dec_totalhigh_pages() do {} while(0)
	106	#endif
	107
	108	/* List of ballooned pages, threaded through the mem_map array. */
	109	static LIST_HEAD(ballooned_pages);
	110
	111	/* Main work function, always executed in process context. */
	112	static void balloon_process(struct work_struct *work);
	113	static DECLARE_WORK(balloon_worker, balloon_process);
	114	static struct timer_list balloon_timer;
	115
	116	/* When ballooning out (allocating memory to return to Xen) we don't really
	117	want the kernel to try too hard since that can trigger the oom killer. */
	118	#define GFP_BALLOON \
	119	(GFP_HIGHUSER \| __GFP_NOWARN \| __GFP_NORETRY \| __GFP_NOMEMALLOC)
	120
	121	static void scrub_page(struct page *page)
	122	{
	123	#ifdef CONFIG_XEN_SCRUB_PAGES
26a3e991	124	clear_highpage(page);
1775826c JF	125	#endif
	126	}
	127
	128	/* balloon_append: add the given page to the balloon. */
	129	static void balloon_append(struct page *page)
	130	{
	131	/* Lowmem is re-populated first, so highmem pages go at list tail. */
	132	if (PageHighMem(page)) {
	133	list_add_tail(&page->lru, &ballooned_pages);
	134	balloon_stats.balloon_high++;
	135	dec_totalhigh_pages();
	136	} else {
	137	list_add(&page->lru, &ballooned_pages);
	138	balloon_stats.balloon_low++;
	139	}
3d65c948 GG	140
3d65c948 GG	141	totalram_pages--;
1775826c JF	142	}
	143
	144	/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
	145	static struct page *balloon_retrieve(void)
	146	{
	147	struct page *page;
	148
	149	if (list_empty(&ballooned_pages))
	150	return NULL;
	151
	152	page = list_entry(ballooned_pages.next, struct page, lru);
	153	list_del(&page->lru);
	154
	155	if (PageHighMem(page)) {
	156	balloon_stats.balloon_high--;
	157	inc_totalhigh_pages();
	158	}
	159	else
	160	balloon_stats.balloon_low--;
	161
3d65c948 GG	162	totalram_pages++;
3d65c948 GG	163
1775826c JF	164	return page;
	165	}
	166
	167	static struct page *balloon_first_page(void)
	168	{
	169	if (list_empty(&ballooned_pages))
	170	return NULL;
	171	return list_entry(ballooned_pages.next, struct page, lru);
	172	}
	173
	174	static struct page balloon_next_page(struct page page)
	175	{
	176	struct list_head *next = page->lru.next;
	177	if (next == &ballooned_pages)
	178	return NULL;
	179	return list_entry(next, struct page, lru);
	180	}
	181
	182	static void balloon_alarm(unsigned long unused)
	183	{
	184	schedule_work(&balloon_worker);
	185	}
	186
	187	static unsigned long current_target(void)
	188	{
bc2c0303	189	unsigned long target = balloon_stats.target_pages;
1775826c JF	190
	191	target = min(target,
	192	balloon_stats.current_pages +
	193	balloon_stats.balloon_low +
	194	balloon_stats.balloon_high);
	195
	196	return target;
	197	}
	198
	199	static int increase_reservation(unsigned long nr_pages)
	200	{
	201	unsigned long pfn, i, flags;
	202	struct page *page;
	203	long rc;
	204	struct xen_memory_reservation reservation = {
	205	.address_bits = 0,
	206	.extent_order = 0,
	207	.domid = DOMID_SELF
	208	};
	209
	210	if (nr_pages > ARRAY_SIZE(frame_list))
	211	nr_pages = ARRAY_SIZE(frame_list);
	212
	213	spin_lock_irqsave(&balloon_lock, flags);
	214
	215	page = balloon_first_page();
	216	for (i = 0; i < nr_pages; i++) {
	217	BUG_ON(page == NULL);
a419aef8	218	frame_list[i] = page_to_pfn(page);
1775826c JF	219	page = balloon_next_page(page);
	220	}
	221
a90971eb	222	set_xen_guest_handle(reservation.extent_start, frame_list);
fde28e8f JF	223	reservation.nr_extents = nr_pages;
fde28e8f JF	224	rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
bc2c0303	225	if (rc < 0)
1775826c	226	goto out;
1775826c	227
bc2c0303	228	for (i = 0; i < rc; i++) {
1775826c JF	229	page = balloon_retrieve();
	230	BUG_ON(page == NULL);
	231
	232	pfn = page_to_pfn(page);
	233	BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
	234	phys_to_machine_mapping_valid(pfn));
	235
	236	set_phys_to_machine(pfn, frame_list[i]);
	237
	238	/* Link back into the page tables if not highmem. */
	239	if (pfn < max_low_pfn) {
	240	int ret;
	241	ret = HYPERVISOR_update_va_mapping(
	242	(unsigned long)__va(pfn << PAGE_SHIFT),
	243	mfn_pte(frame_list[i], PAGE_KERNEL),
	244	0);
	245	BUG_ON(ret);
	246	}
	247
	248	/* Relinquish the page back to the allocator. */
	249	ClearPageReserved(page);
	250	init_page_count(page);
	251	__free_page(page);
	252	}
	253
bc2c0303	254	balloon_stats.current_pages += rc;
1775826c JF	255
	256	out:
	257	spin_unlock_irqrestore(&balloon_lock, flags);
	258
bc2c0303	259	return rc < 0 ? rc : rc != nr_pages;
1775826c JF	260	}
	261
	262	static int decrease_reservation(unsigned long nr_pages)
	263	{
	264	unsigned long pfn, i, flags;
	265	struct page *page;
	266	int need_sleep = 0;
	267	int ret;
	268	struct xen_memory_reservation reservation = {
	269	.address_bits = 0,
	270	.extent_order = 0,
	271	.domid = DOMID_SELF
	272	};
	273
	274	if (nr_pages > ARRAY_SIZE(frame_list))
	275	nr_pages = ARRAY_SIZE(frame_list);
	276
	277	for (i = 0; i < nr_pages; i++) {
	278	if ((page = alloc_page(GFP_BALLOON)) == NULL) {
	279	nr_pages = i;
	280	need_sleep = 1;
	281	break;
	282	}
	283
	284	pfn = page_to_pfn(page);
	285	frame_list[i] = pfn_to_mfn(pfn);
	286
	287	scrub_page(page);
1058a75f	288
ff4ce8c3 IC	289	if (!PageHighMem(page)) {
	290	ret = HYPERVISOR_update_va_mapping(
	291	(unsigned long)__va(pfn << PAGE_SHIFT),
	292	__pte_ma(0), 0);
	293	BUG_ON(ret);
	294	}
	295
1775826c JF	296	}
	297
	298	/* Ensure that ballooned highmem pages don't have kmaps. */
	299	kmap_flush_unused();
	300	flush_tlb_all();
	301
	302	spin_lock_irqsave(&balloon_lock, flags);
	303
	304	/* No more mappings: invalidate P2M and add to balloon. */
	305	for (i = 0; i < nr_pages; i++) {
	306	pfn = mfn_to_pfn(frame_list[i]);
	307	set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
	308	balloon_append(pfn_to_page(pfn));
	309	}
	310
a90971eb	311	set_xen_guest_handle(reservation.extent_start, frame_list);
1775826c JF	312	reservation.nr_extents = nr_pages;
	313	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
	314	BUG_ON(ret != nr_pages);
	315
	316	balloon_stats.current_pages -= nr_pages;
1775826c JF	317
	318	spin_unlock_irqrestore(&balloon_lock, flags);
	319
	320	return need_sleep;
	321	}
	322
	323	/*
	324	* We avoid multiple worker processes conflicting via the balloon mutex.
	325	* We may of course race updates of the target counts (which are protected
	326	* by the balloon lock), or with changes to the Xen hard limit, but we will
	327	* recover from these in time.
	328	*/
	329	static void balloon_process(struct work_struct *work)
	330	{
	331	int need_sleep = 0;
	332	long credit;
	333
	334	mutex_lock(&balloon_mutex);
	335
	336	do {
	337	credit = current_target() - balloon_stats.current_pages;
	338	if (credit > 0)
	339	need_sleep = (increase_reservation(credit) != 0);
	340	if (credit < 0)
	341	need_sleep = (decrease_reservation(-credit) != 0);
	342
	343	#ifndef CONFIG_PREEMPT
	344	if (need_resched())
	345	schedule();
	346	#endif
	347	} while ((credit != 0) && !need_sleep);
	348
	349	/* Schedule more work if there is some still to be done. */
	350	if (current_target() != balloon_stats.current_pages)
	351	mod_timer(&balloon_timer, jiffies + HZ);
	352
	353	mutex_unlock(&balloon_mutex);
	354	}
	355
	356	/* Resets the Xen limit, sets new target, and kicks off processing. */
955d6f17	357	static void balloon_set_new_target(unsigned long target)
1775826c JF	358	{
1775826c JF	359	/* No need for lock. Not read-modify-write updates. */
1775826c JF	360	balloon_stats.target_pages = target;
	361	schedule_work(&balloon_worker);
	362	}
	363
	364	static struct xenbus_watch target_watch =
	365	{
	366	.node = "memory/target"
	367	};
	368
	369	/* React to a change in the target key */
	370	static void watch_target(struct xenbus_watch *watch,
	371	const char **vec, unsigned int len)
	372	{
	373	unsigned long long new_target;
	374	int err;
	375
	376	err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
	377	if (err != 1) {
	378	/* This is ok (for domain0 at least) - so just return */
	379	return;
	380	}
	381
	382	/* The given memory/target value is in KiB, so it needs converting to
	383	* pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
	384	*/
	385	balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
	386	}
	387
	388	static int balloon_init_watcher(struct notifier_block *notifier,
	389	unsigned long event,
	390	void *data)
	391	{
	392	int err;
	393
	394	err = register_xenbus_watch(&target_watch);
	395	if (err)
	396	printk(KERN_ERR "Failed to set balloon watcher\n");
	397
	398	return NOTIFY_DONE;
	399	}
	400
	401	static struct notifier_block xenstore_notifier;
	402
	403	static int __init balloon_init(void)
	404	{
	405	unsigned long pfn;
	406	struct page *page;
	407
6e833587	408	if (!xen_pv_domain())
1775826c JF	409	return -ENODEV;
	410
	411	pr_info("xen_balloon: Initialising balloon driver.\n");
	412
	413	balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
1775826c JF	414	balloon_stats.target_pages = balloon_stats.current_pages;
	415	balloon_stats.balloon_low = 0;
	416	balloon_stats.balloon_high = 0;
	417	balloon_stats.driver_pages = 0UL;
1775826c JF	418
	419	init_timer(&balloon_timer);
	420	balloon_timer.data = 0;
	421	balloon_timer.function = balloon_alarm;
	422
	423	register_balloon(&balloon_sysdev);
	424
	425	/* Initialise the balloon with excess memory space. */
	426	for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
	427	page = pfn_to_page(pfn);
	428	if (!PageReserved(page))
	429	balloon_append(page);
	430	}
	431
	432	target_watch.callback = watch_target;
	433	xenstore_notifier.notifier_call = balloon_init_watcher;
	434
	435	register_xenstore_notifier(&xenstore_notifier);
	436
	437	return 0;
	438	}
	439
	440	subsys_initcall(balloon_init);
	441
	442	static void balloon_exit(void)
	443	{
	444	/* XXX - release balloon here */
	445	return;
	446	}
	447
	448	module_exit(balloon_exit);
	449
167e6cf6 JF	450	#define BALLOON_SHOW(name, format, args...) \
	451	static ssize_t show_##name(struct sys_device *dev, \
	452	struct sysdev_attribute *attr, \
	453	char *buf) \
	454	{ \
	455	return sprintf(buf, format, ##args); \
	456	} \
1775826c JF	457	static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
	458
	459	BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
	460	BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
	461	BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
1775826c JF	462	BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
1775826c JF	463
167e6cf6 JF	464	static ssize_t show_target_kb(struct sys_device dev, struct sysdev_attribute attr,
167e6cf6 JF	465	char *buf)
1775826c JF	466	{
	467	return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
	468	}
	469
	470	static ssize_t store_target_kb(struct sys_device *dev,
4a0b2b4d	471	struct sysdev_attribute *attr,
1775826c JF	472	const char *buf,
	473	size_t count)
	474	{
167e6cf6	475	char *endchar;
1775826c JF	476	unsigned long long target_bytes;
	477
	478	if (!capable(CAP_SYS_ADMIN))
	479	return -EPERM;
	480
618b2c8d	481	target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
1775826c	482
1775826c JF	483	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
	484
	485	return count;
	486	}
	487
	488	static SYSDEV_ATTR(target_kb, S_IRUGO \| S_IWUSR,
	489	show_target_kb, store_target_kb);
	490
618b2c8d JF	491
	492	static ssize_t show_target(struct sys_device dev, struct sysdev_attribute attr,
	493	char *buf)
	494	{
	495	return sprintf(buf, "%llu\n",
0692698c JB	496	(unsigned long long)balloon_stats.target_pages
0692698c JB	497	<< PAGE_SHIFT);
618b2c8d JF	498	}
	499
	500	static ssize_t store_target(struct sys_device *dev,
	501	struct sysdev_attribute *attr,
	502	const char *buf,
	503	size_t count)
	504	{
	505	char *endchar;
	506	unsigned long long target_bytes;
	507
	508	if (!capable(CAP_SYS_ADMIN))
	509	return -EPERM;
	510
	511	target_bytes = memparse(buf, &endchar);
	512
	513	balloon_set_new_target(target_bytes >> PAGE_SHIFT);
	514
	515	return count;
	516	}
	517
	518	static SYSDEV_ATTR(target, S_IRUGO \| S_IWUSR,
	519	show_target, store_target);
	520
	521
1775826c JF	522	static struct sysdev_attribute *balloon_attrs[] = {
1775826c JF	523	&attr_target_kb,
618b2c8d	524	&attr_target,
1775826c JF	525	};
	526
	527	static struct attribute *balloon_info_attrs[] = {
	528	&attr_current_kb.attr,
	529	&attr_low_kb.attr,
	530	&attr_high_kb.attr,
1775826c JF	531	&attr_driver_kb.attr,
	532	NULL
	533	};
	534
	535	static struct attribute_group balloon_info_group = {
	536	.name = "info",
	537	.attrs = balloon_info_attrs,
	538	};
	539
	540	static struct sysdev_class balloon_sysdev_class = {
	541	.name = BALLOON_CLASS_NAME,
	542	};
	543
	544	static int register_balloon(struct sys_device *sysdev)
	545	{
	546	int i, error;
	547
	548	error = sysdev_class_register(&balloon_sysdev_class);
	549	if (error)
	550	return error;
	551
	552	sysdev->id = 0;
	553	sysdev->cls = &balloon_sysdev_class;
	554
	555	error = sysdev_register(sysdev);
	556	if (error) {
	557	sysdev_class_unregister(&balloon_sysdev_class);
	558	return error;
	559	}
	560
	561	for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
	562	error = sysdev_create_file(sysdev, balloon_attrs[i]);
	563	if (error)
	564	goto fail;
	565	}
	566
	567	error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
	568	if (error)
	569	goto fail;
	570
	571	return 0;
	572
	573	fail:
	574	while (--i >= 0)
	575	sysdev_remove_file(sysdev, balloon_attrs[i]);
	576	sysdev_unregister(sysdev);
	577	sysdev_class_unregister(&balloon_sysdev_class);
	578	return error;
	579	}
	580
1775826c	581	MODULE_LICENSE("GPL");