/****************************************************************************** * 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/highmem.h> #include <linux/list.h> #include <linux/sysdev.h> #include <asm/xen/hypervisor.h> #include <asm/page.h> #include <asm/pgalloc.h> #include <asm/pgtable.h> #include <asm/uaccess.h> #include <asm/tlb.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; /* We may hit the hard limit in Xen. If we do then we remember it. */ unsigned long hard_limit; /* * 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)]; /* VM /proc information for memory */ extern unsigned long totalram_pages; #ifdef CONFIG_HIGHMEM extern unsigned long totalhigh_pages; #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 if (PageHighMem(page)) { void *v = kmap(page); clear_page(v); kunmap(v); } else { void *v = page_address(page); clear_page(v); } #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++; } } /* 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--; 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 = min(balloon_stats.target_pages, balloon_stats.hard_limit); 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 < nr_pages) { if (rc > 0) { int ret; /* We hit the Xen hard limit: reprobe. */ reservation.nr_extents = rc; ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); BUG_ON(ret != rc); } if (rc >= 0) balloon_stats.hard_limit = (balloon_stats.current_pages + rc - balloon_stats.driver_pages); goto out; } for (i = 0; i < nr_pages; 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 += nr_pages; totalram_pages = balloon_stats.current_pages; out: spin_unlock_irqrestore(&balloon_lock, flags); return 0; } 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); } /* 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; totalram_pages = balloon_stats.current_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.hard_limit = ~0UL; 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); totalram_pages = balloon_stats.current_pages; balloon_stats.target_pages = balloon_stats.current_pages; balloon_stats.balloon_low = 0; balloon_stats.balloon_high = 0; balloon_stats.driver_pages = 0UL; balloon_stats.hard_limit = ~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(hard_limit_kb, (balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n", (balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0); 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 = memparse(buf, &endchar); 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 struct sysdev_attribute *balloon_attrs[] = { &attr_target_kb, }; static struct attribute *balloon_info_attrs[] = { &attr_current_kb.attr, &attr_low_kb.attr, &attr_high_kb.attr, &attr_hard_limit_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");