diff options
Diffstat (limited to 'drivers/xen/balloon.c')
| -rw-r--r-- | drivers/xen/balloon.c | 712 |
1 files changed, 712 insertions, 0 deletions
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c new file mode 100644 index 000000000000..ab25ba6cbbb9 --- /dev/null +++ b/drivers/xen/balloon.c @@ -0,0 +1,712 @@ +/****************************************************************************** + * 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/balloon.h> +#include <xen/xenbus.h> +#include <xen/features.h> +#include <xen/page.h> + +#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10)) + +#define BALLOON_CLASS_NAME "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); + } + + reservation.extent_start = (unsigned long)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)); + } + + reservation.extent_start = (unsigned long)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. */ +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 (!is_running_on_xen()) + 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); + +static void balloon_update_driver_allowance(long delta) +{ + unsigned long flags; + + spin_lock_irqsave(&balloon_lock, flags); + balloon_stats.driver_pages += delta; + spin_unlock_irqrestore(&balloon_lock, flags); +} + +static int dealloc_pte_fn( + pte_t *pte, struct page *pmd_page, unsigned long addr, void *data) +{ + unsigned long mfn = pte_mfn(*pte); + int ret; + struct xen_memory_reservation reservation = { + .nr_extents = 1, + .extent_order = 0, + .domid = DOMID_SELF + }; + reservation.extent_start = (unsigned long)&mfn; + set_pte_at(&init_mm, addr, pte, __pte_ma(0ull)); + set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY); + ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); + BUG_ON(ret != 1); + return 0; +} + +static struct page **alloc_empty_pages_and_pagevec(int nr_pages) +{ + unsigned long vaddr, flags; + struct page *page, **pagevec; + int i, ret; + + pagevec = kmalloc(sizeof(page) * nr_pages, GFP_KERNEL); + if (pagevec == NULL) + return NULL; + + for (i = 0; i < nr_pages; i++) { + page = pagevec[i] = alloc_page(GFP_KERNEL); + if (page == NULL) + goto err; + + vaddr = (unsigned long)page_address(page); + + scrub_page(page); + + spin_lock_irqsave(&balloon_lock, flags); + + if (xen_feature(XENFEAT_auto_translated_physmap)) { + unsigned long gmfn = page_to_pfn(page); + struct xen_memory_reservation reservation = { + .nr_extents = 1, + .extent_order = 0, + .domid = DOMID_SELF + }; + reservation.extent_start = (unsigned long)&gmfn; + ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, + &reservation); + if (ret == 1) + ret = 0; /* success */ + } else { + ret = apply_to_page_range(&init_mm, vaddr, PAGE_SIZE, + dealloc_pte_fn, NULL); + } + + if (ret != 0) { + spin_unlock_irqrestore(&balloon_lock, flags); + __free_page(page); + goto err; + } + + totalram_pages = --balloon_stats.current_pages; + + spin_unlock_irqrestore(&balloon_lock, flags); + } + + out: + schedule_work(&balloon_worker); + flush_tlb_all(); + return pagevec; + + err: + spin_lock_irqsave(&balloon_lock, flags); + while (--i >= 0) + balloon_append(pagevec[i]); + spin_unlock_irqrestore(&balloon_lock, flags); + kfree(pagevec); + pagevec = NULL; + goto out; +} + +static void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages) +{ + unsigned long flags; + int i; + + if (pagevec == NULL) + return; + + spin_lock_irqsave(&balloon_lock, flags); + for (i = 0; i < nr_pages; i++) { + BUG_ON(page_count(pagevec[i]) != 1); + balloon_append(pagevec[i]); + } + spin_unlock_irqrestore(&balloon_lock, flags); + + kfree(pagevec); + + schedule_work(&balloon_worker); +} + +static void balloon_release_driver_page(struct page *page) +{ + unsigned long flags; + + spin_lock_irqsave(&balloon_lock, flags); + balloon_append(page); + balloon_stats.driver_pages--; + spin_unlock_irqrestore(&balloon_lock, flags); + + schedule_work(&balloon_worker); +} + + +#define BALLOON_SHOW(name, format, args...) \ + static ssize_t show_##name(struct sys_device *dev, \ + 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, char *buf) +{ + return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages)); +} + +static ssize_t store_target_kb(struct sys_device *dev, + const char *buf, + size_t count) +{ + char memstring[64], *endchar; + unsigned long long target_bytes; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (count <= 1) + return -EBADMSG; /* runt */ + if (count > sizeof(memstring)) + return -EFBIG; /* too long */ + strcpy(memstring, buf); + + target_bytes = memparse(memstring, &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; +} + +static void unregister_balloon(struct sys_device *sysdev) +{ + int i; + + sysfs_remove_group(&sysdev->kobj, &balloon_info_group); + for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) + sysdev_remove_file(sysdev, balloon_attrs[i]); + sysdev_unregister(sysdev); + sysdev_class_unregister(&balloon_sysdev_class); +} + +static void balloon_sysfs_exit(void) +{ + unregister_balloon(&balloon_sysdev); +} + +MODULE_LICENSE("GPL"); |