1 /******************************************************************************
4 * Xen balloon driver - enables returning/claiming memory to/from Xen.
6 * Copyright (c) 2003, B Dragovic
7 * Copyright (c) 2003-2004, M Williamson, K Fraser
8 * Copyright (c) 2005 Dan M. Smith, IBM Corporation
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:
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:
23 * The above copyright notice and this permission notice shall be included in
24 * all copies or substantial portions of the Software.
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
35 #include <linux/kernel.h>
36 #include <linux/module.h>
37 #include <linux/sched.h>
38 #include <linux/errno.h>
40 #include <linux/bootmem.h>
41 #include <linux/pagemap.h>
42 #include <linux/highmem.h>
43 #include <linux/mutex.h>
44 #include <linux/list.h>
45 #include <linux/sysdev.h>
46 #include <linux/gfp.h>
49 #include <asm/pgalloc.h>
50 #include <asm/pgtable.h>
51 #include <asm/uaccess.h>
54 #include <asm/xen/hypervisor.h>
55 #include <asm/xen/hypercall.h>
58 #include <xen/interface/xen.h>
59 #include <xen/interface/memory.h>
60 #include <xen/xenbus.h>
61 #include <xen/features.h>
64 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
66 #define BALLOON_CLASS_NAME "xen_memory"
68 struct balloon_stats {
69 /* We aim for 'current allocation' == 'target allocation'. */
70 unsigned long current_pages;
71 unsigned long target_pages;
73 * Drivers may alter the memory reservation independently, but they
74 * must inform the balloon driver so we avoid hitting the hard limit.
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;
82 static DEFINE_MUTEX(balloon_mutex);
84 static struct sys_device balloon_sysdev;
86 static int register_balloon(struct sys_device *sysdev);
88 static struct balloon_stats balloon_stats;
90 /* We increase/decrease in batches which fit in a page */
91 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
94 #define inc_totalhigh_pages() (totalhigh_pages++)
95 #define dec_totalhigh_pages() (totalhigh_pages--)
97 #define inc_totalhigh_pages() do {} while(0)
98 #define dec_totalhigh_pages() do {} while(0)
101 /* List of ballooned pages, threaded through the mem_map array. */
102 static LIST_HEAD(ballooned_pages);
104 /* Main work function, always executed in process context. */
105 static void balloon_process(struct work_struct *work);
106 static DECLARE_WORK(balloon_worker, balloon_process);
107 static struct timer_list balloon_timer;
109 /* When ballooning out (allocating memory to return to Xen) we don't really
110 want the kernel to try too hard since that can trigger the oom killer. */
111 #define GFP_BALLOON \
112 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
114 static void scrub_page(struct page *page)
116 #ifdef CONFIG_XEN_SCRUB_PAGES
117 clear_highpage(page);
121 /* balloon_append: add the given page to the balloon. */
122 static void __balloon_append(struct page *page)
124 /* Lowmem is re-populated first, so highmem pages go at list tail. */
125 if (PageHighMem(page)) {
126 list_add_tail(&page->lru, &ballooned_pages);
127 balloon_stats.balloon_high++;
128 dec_totalhigh_pages();
130 list_add(&page->lru, &ballooned_pages);
131 balloon_stats.balloon_low++;
135 static void balloon_append(struct page *page)
137 __balloon_append(page);
141 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
142 static struct page *balloon_retrieve(void)
146 if (list_empty(&ballooned_pages))
149 page = list_entry(ballooned_pages.next, struct page, lru);
150 list_del(&page->lru);
152 if (PageHighMem(page)) {
153 balloon_stats.balloon_high--;
154 inc_totalhigh_pages();
157 balloon_stats.balloon_low--;
164 static struct page *balloon_first_page(void)
166 if (list_empty(&ballooned_pages))
168 return list_entry(ballooned_pages.next, struct page, lru);
171 static struct page *balloon_next_page(struct page *page)
173 struct list_head *next = page->lru.next;
174 if (next == &ballooned_pages)
176 return list_entry(next, struct page, lru);
179 static void balloon_alarm(unsigned long unused)
181 schedule_work(&balloon_worker);
184 static unsigned long current_target(void)
186 unsigned long target = balloon_stats.target_pages;
189 balloon_stats.current_pages +
190 balloon_stats.balloon_low +
191 balloon_stats.balloon_high);
196 static int increase_reservation(unsigned long nr_pages)
198 unsigned long pfn, i, flags;
201 struct xen_memory_reservation reservation = {
207 if (nr_pages > ARRAY_SIZE(frame_list))
208 nr_pages = ARRAY_SIZE(frame_list);
210 spin_lock_irqsave(&xen_reservation_lock, flags);
212 page = balloon_first_page();
213 for (i = 0; i < nr_pages; i++) {
214 BUG_ON(page == NULL);
215 frame_list[i] = page_to_pfn(page);
216 page = balloon_next_page(page);
219 set_xen_guest_handle(reservation.extent_start, frame_list);
220 reservation.nr_extents = nr_pages;
221 rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
225 for (i = 0; i < rc; i++) {
226 page = balloon_retrieve();
227 BUG_ON(page == NULL);
229 pfn = page_to_pfn(page);
230 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
231 phys_to_machine_mapping_valid(pfn));
233 set_phys_to_machine(pfn, frame_list[i]);
235 /* Link back into the page tables if not highmem. */
236 if (pfn < max_low_pfn) {
238 ret = HYPERVISOR_update_va_mapping(
239 (unsigned long)__va(pfn << PAGE_SHIFT),
240 mfn_pte(frame_list[i], PAGE_KERNEL),
245 /* Relinquish the page back to the allocator. */
246 ClearPageReserved(page);
247 init_page_count(page);
251 balloon_stats.current_pages += rc;
254 spin_unlock_irqrestore(&xen_reservation_lock, flags);
256 return rc < 0 ? rc : rc != nr_pages;
259 static int decrease_reservation(unsigned long nr_pages)
261 unsigned long pfn, i, flags;
265 struct xen_memory_reservation reservation = {
271 if (nr_pages > ARRAY_SIZE(frame_list))
272 nr_pages = ARRAY_SIZE(frame_list);
274 for (i = 0; i < nr_pages; i++) {
275 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
281 pfn = page_to_pfn(page);
282 frame_list[i] = pfn_to_mfn(pfn);
286 if (!PageHighMem(page)) {
287 ret = HYPERVISOR_update_va_mapping(
288 (unsigned long)__va(pfn << PAGE_SHIFT),
295 /* Ensure that ballooned highmem pages don't have kmaps. */
299 spin_lock_irqsave(&xen_reservation_lock, flags);
301 /* No more mappings: invalidate P2M and add to balloon. */
302 for (i = 0; i < nr_pages; i++) {
303 pfn = mfn_to_pfn(frame_list[i]);
304 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
305 balloon_append(pfn_to_page(pfn));
308 set_xen_guest_handle(reservation.extent_start, frame_list);
309 reservation.nr_extents = nr_pages;
310 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
311 BUG_ON(ret != nr_pages);
313 balloon_stats.current_pages -= nr_pages;
315 spin_unlock_irqrestore(&xen_reservation_lock, flags);
321 * We avoid multiple worker processes conflicting via the balloon mutex.
322 * We may of course race updates of the target counts (which are protected
323 * by the balloon lock), or with changes to the Xen hard limit, but we will
324 * recover from these in time.
326 static void balloon_process(struct work_struct *work)
331 mutex_lock(&balloon_mutex);
334 credit = current_target() - balloon_stats.current_pages;
336 need_sleep = (increase_reservation(credit) != 0);
338 need_sleep = (decrease_reservation(-credit) != 0);
340 #ifndef CONFIG_PREEMPT
344 } while ((credit != 0) && !need_sleep);
346 /* Schedule more work if there is some still to be done. */
347 if (current_target() != balloon_stats.current_pages)
348 mod_timer(&balloon_timer, jiffies + HZ);
350 mutex_unlock(&balloon_mutex);
353 /* Resets the Xen limit, sets new target, and kicks off processing. */
354 static void balloon_set_new_target(unsigned long target)
356 /* No need for lock. Not read-modify-write updates. */
357 balloon_stats.target_pages = target;
358 schedule_work(&balloon_worker);
361 static struct xenbus_watch target_watch =
363 .node = "memory/target"
366 /* React to a change in the target key */
367 static void watch_target(struct xenbus_watch *watch,
368 const char **vec, unsigned int len)
370 unsigned long long new_target;
373 err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
375 /* This is ok (for domain0 at least) - so just return */
379 /* The given memory/target value is in KiB, so it needs converting to
380 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
382 balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
385 static int balloon_init_watcher(struct notifier_block *notifier,
391 err = register_xenbus_watch(&target_watch);
393 printk(KERN_ERR "Failed to set balloon watcher\n");
398 static struct notifier_block xenstore_notifier;
400 static int __init balloon_init(void)
405 if (!xen_pv_domain())
408 pr_info("xen_balloon: Initialising balloon driver.\n");
410 balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
411 balloon_stats.target_pages = balloon_stats.current_pages;
412 balloon_stats.balloon_low = 0;
413 balloon_stats.balloon_high = 0;
414 balloon_stats.driver_pages = 0UL;
416 init_timer(&balloon_timer);
417 balloon_timer.data = 0;
418 balloon_timer.function = balloon_alarm;
420 register_balloon(&balloon_sysdev);
422 /* Initialise the balloon with excess memory space. */
423 for (pfn = PFN_UP(xen_extra_mem_start);
424 pfn < PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size);
426 page = pfn_to_page(pfn);
427 /* totalram_pages doesn't include the boot-time
428 balloon extension, so don't subtract from it. */
429 __balloon_append(page);
432 target_watch.callback = watch_target;
433 xenstore_notifier.notifier_call = balloon_init_watcher;
435 register_xenstore_notifier(&xenstore_notifier);
440 subsys_initcall(balloon_init);
442 static void balloon_exit(void)
444 /* XXX - release balloon here */
448 module_exit(balloon_exit);
450 #define BALLOON_SHOW(name, format, args...) \
451 static ssize_t show_##name(struct sys_device *dev, \
452 struct sysdev_attribute *attr, \
455 return sprintf(buf, format, ##args); \
457 static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
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));
462 BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
464 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
467 return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
470 static ssize_t store_target_kb(struct sys_device *dev,
471 struct sysdev_attribute *attr,
476 unsigned long long target_bytes;
478 if (!capable(CAP_SYS_ADMIN))
481 target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
483 balloon_set_new_target(target_bytes >> PAGE_SHIFT);
488 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
489 show_target_kb, store_target_kb);
492 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
495 return sprintf(buf, "%llu\n",
496 (unsigned long long)balloon_stats.target_pages
500 static ssize_t store_target(struct sys_device *dev,
501 struct sysdev_attribute *attr,
506 unsigned long long target_bytes;
508 if (!capable(CAP_SYS_ADMIN))
511 target_bytes = memparse(buf, &endchar);
513 balloon_set_new_target(target_bytes >> PAGE_SHIFT);
518 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
519 show_target, store_target);
522 static struct sysdev_attribute *balloon_attrs[] = {
527 static struct attribute *balloon_info_attrs[] = {
528 &attr_current_kb.attr,
531 &attr_driver_kb.attr,
535 static struct attribute_group balloon_info_group = {
537 .attrs = balloon_info_attrs,
540 static struct sysdev_class balloon_sysdev_class = {
541 .name = BALLOON_CLASS_NAME,
544 static int register_balloon(struct sys_device *sysdev)
548 error = sysdev_class_register(&balloon_sysdev_class);
553 sysdev->cls = &balloon_sysdev_class;
555 error = sysdev_register(sysdev);
557 sysdev_class_unregister(&balloon_sysdev_class);
561 for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
562 error = sysdev_create_file(sysdev, balloon_attrs[i]);
567 error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
575 sysdev_remove_file(sysdev, balloon_attrs[i]);
576 sysdev_unregister(sysdev);
577 sysdev_class_unregister(&balloon_sysdev_class);
581 MODULE_LICENSE("GPL");