| /****************************************************************************** |
| * 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/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; |
| /* 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 |
| 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++; |
| } |
| } |
| |
| /* 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); |
| |
| 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; |
| 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"); |