diff options
Diffstat (limited to 'drivers/xen/balloon.c')
| -rw-r--r-- | drivers/xen/balloon.c | 801 |
1 files changed, 801 insertions, 0 deletions
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c new file mode 100644 index 000000000..617a7f4f0 --- /dev/null +++ b/drivers/xen/balloon.c @@ -0,0 +1,801 @@ +/****************************************************************************** + * 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 + * Copyright (c) 2010 Daniel Kiper + * + * Memory hotplug support was written by Daniel Kiper. Work on + * it was sponsored by Google under Google Summer of Code 2010 + * program. Jeremy Fitzhardinge from Citrix was the mentor for + * this project. + * + * 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. + */ + +#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt + +#include <linux/cpu.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/cred.h> +#include <linux/errno.h> +#include <linux/freezer.h> +#include <linux/kthread.h> +#include <linux/mm.h> +#include <linux/memblock.h> +#include <linux/pagemap.h> +#include <linux/highmem.h> +#include <linux/mutex.h> +#include <linux/list.h> +#include <linux/gfp.h> +#include <linux/notifier.h> +#include <linux/memory.h> +#include <linux/memory_hotplug.h> +#include <linux/percpu-defs.h> +#include <linux/slab.h> +#include <linux/sysctl.h> +#include <linux/moduleparam.h> +#include <linux/jiffies.h> + +#include <asm/page.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/balloon.h> +#include <xen/features.h> +#include <xen/page.h> +#include <xen/mem-reservation.h> + +#undef MODULE_PARAM_PREFIX +#define MODULE_PARAM_PREFIX "xen." + +static uint __read_mostly balloon_boot_timeout = 180; +module_param(balloon_boot_timeout, uint, 0444); + +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG +static int xen_hotplug_unpopulated; + +static struct ctl_table balloon_table[] = { + { + .procname = "hotplug_unpopulated", + .data = &xen_hotplug_unpopulated, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + +static struct ctl_table balloon_root[] = { + { + .procname = "balloon", + .mode = 0555, + .child = balloon_table, + }, + { } +}; + +static struct ctl_table xen_root[] = { + { + .procname = "xen", + .mode = 0555, + .child = balloon_root, + }, + { } +}; + +#else +#define xen_hotplug_unpopulated 0 +#endif + +/* + * Use one extent per PAGE_SIZE to avoid to break down the page into + * multiple frame. + */ +#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1) + +/* + * balloon_thread() state: + * + * BP_DONE: done or nothing to do, + * BP_WAIT: wait to be rescheduled, + * BP_EAGAIN: error, go to sleep, + * BP_ECANCELED: error, balloon operation canceled. + */ + +static enum bp_state { + BP_DONE, + BP_WAIT, + BP_EAGAIN, + BP_ECANCELED +} balloon_state = BP_DONE; + +/* Main waiting point for xen-balloon thread. */ +static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq); + +static DEFINE_MUTEX(balloon_mutex); + +struct balloon_stats balloon_stats; +EXPORT_SYMBOL_GPL(balloon_stats); + +/* We increase/decrease in batches which fit in a page */ +static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)]; + + +/* List of ballooned pages, threaded through the mem_map array. */ +static LIST_HEAD(ballooned_pages); +static DECLARE_WAIT_QUEUE_HEAD(balloon_wq); + +/* 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) + +/* balloon_append: add the given page to the balloon. */ +static void balloon_append(struct page *page) +{ + __SetPageOffline(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++; + } else { + list_add(&page->lru, &ballooned_pages); + balloon_stats.balloon_low++; + } + wake_up(&balloon_wq); +} + +/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */ +static struct page *balloon_retrieve(bool require_lowmem) +{ + struct page *page; + + if (list_empty(&ballooned_pages)) + return NULL; + + page = list_entry(ballooned_pages.next, struct page, lru); + if (require_lowmem && PageHighMem(page)) + return NULL; + list_del(&page->lru); + + if (PageHighMem(page)) + balloon_stats.balloon_high--; + else + balloon_stats.balloon_low--; + + __ClearPageOffline(page); + return page; +} + +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 update_schedule(void) +{ + if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED) + return; + + if (balloon_state == BP_DONE) { + balloon_stats.schedule_delay = 1; + balloon_stats.retry_count = 1; + return; + } + + ++balloon_stats.retry_count; + + if (balloon_stats.max_retry_count != RETRY_UNLIMITED && + balloon_stats.retry_count > balloon_stats.max_retry_count) { + balloon_stats.schedule_delay = 1; + balloon_stats.retry_count = 1; + balloon_state = BP_ECANCELED; + return; + } + + balloon_stats.schedule_delay <<= 1; + + if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay) + balloon_stats.schedule_delay = balloon_stats.max_schedule_delay; + + balloon_state = BP_EAGAIN; +} + +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG +static void release_memory_resource(struct resource *resource) +{ + if (!resource) + return; + + /* + * No need to reset region to identity mapped since we now + * know that no I/O can be in this region + */ + release_resource(resource); + kfree(resource); +} + +static struct resource *additional_memory_resource(phys_addr_t size) +{ + struct resource *res; + int ret; + + res = kzalloc(sizeof(*res), GFP_KERNEL); + if (!res) + return NULL; + + res->name = "System RAM"; + res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY; + + ret = allocate_resource(&iomem_resource, res, + size, 0, -1, + PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL); + if (ret < 0) { + pr_err("Cannot allocate new System RAM resource\n"); + kfree(res); + return NULL; + } + + return res; +} + +static enum bp_state reserve_additional_memory(void) +{ + long credit; + struct resource *resource; + int nid, rc; + unsigned long balloon_hotplug; + + credit = balloon_stats.target_pages + balloon_stats.target_unpopulated + - balloon_stats.total_pages; + + /* + * Already hotplugged enough pages? Wait for them to be + * onlined. + */ + if (credit <= 0) + return BP_WAIT; + + balloon_hotplug = round_up(credit, PAGES_PER_SECTION); + + resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE); + if (!resource) + goto err; + + nid = memory_add_physaddr_to_nid(resource->start); + +#ifdef CONFIG_XEN_HAVE_PVMMU + /* + * We don't support PV MMU when Linux and Xen is using + * different page granularity. + */ + BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE); + + /* + * add_memory() will build page tables for the new memory so + * the p2m must contain invalid entries so the correct + * non-present PTEs will be written. + * + * If a failure occurs, the original (identity) p2m entries + * are not restored since this region is now known not to + * conflict with any devices. + */ + if (!xen_feature(XENFEAT_auto_translated_physmap)) { + unsigned long pfn, i; + + pfn = PFN_DOWN(resource->start); + for (i = 0; i < balloon_hotplug; i++) { + if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) { + pr_warn("set_phys_to_machine() failed, no memory added\n"); + goto err; + } + } + } +#endif + + /* + * add_memory_resource() will call online_pages() which in its turn + * will call xen_online_page() callback causing deadlock if we don't + * release balloon_mutex here. Unlocking here is safe because the + * callers drop the mutex before trying again. + */ + mutex_unlock(&balloon_mutex); + /* add_memory_resource() requires the device_hotplug lock */ + lock_device_hotplug(); + rc = add_memory_resource(nid, resource, MHP_MERGE_RESOURCE); + unlock_device_hotplug(); + mutex_lock(&balloon_mutex); + + if (rc) { + pr_warn("Cannot add additional memory (%i)\n", rc); + goto err; + } + + balloon_stats.total_pages += balloon_hotplug; + + return BP_WAIT; + err: + release_memory_resource(resource); + return BP_ECANCELED; +} + +static void xen_online_page(struct page *page, unsigned int order) +{ + unsigned long i, size = (1 << order); + unsigned long start_pfn = page_to_pfn(page); + struct page *p; + + pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn); + mutex_lock(&balloon_mutex); + for (i = 0; i < size; i++) { + p = pfn_to_page(start_pfn + i); + balloon_append(p); + } + mutex_unlock(&balloon_mutex); +} + +static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v) +{ + if (val == MEM_ONLINE) + wake_up(&balloon_thread_wq); + + return NOTIFY_OK; +} + +static struct notifier_block xen_memory_nb = { + .notifier_call = xen_memory_notifier, + .priority = 0 +}; +#else +static enum bp_state reserve_additional_memory(void) +{ + balloon_stats.target_pages = balloon_stats.current_pages + + balloon_stats.target_unpopulated; + return BP_ECANCELED; +} +#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */ + +static long current_credit(void) +{ + return balloon_stats.target_pages - balloon_stats.current_pages; +} + +static bool balloon_is_inflated(void) +{ + return balloon_stats.balloon_low || balloon_stats.balloon_high; +} + +static enum bp_state increase_reservation(unsigned long nr_pages) +{ + int rc; + unsigned long i; + struct page *page; + + if (nr_pages > ARRAY_SIZE(frame_list)) + nr_pages = ARRAY_SIZE(frame_list); + + page = list_first_entry_or_null(&ballooned_pages, struct page, lru); + for (i = 0; i < nr_pages; i++) { + if (!page) { + nr_pages = i; + break; + } + + frame_list[i] = page_to_xen_pfn(page); + page = balloon_next_page(page); + } + + rc = xenmem_reservation_increase(nr_pages, frame_list); + if (rc <= 0) + return BP_EAGAIN; + + for (i = 0; i < rc; i++) { + page = balloon_retrieve(false); + BUG_ON(page == NULL); + + xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]); + + /* Relinquish the page back to the allocator. */ + free_reserved_page(page); + } + + balloon_stats.current_pages += rc; + + return BP_DONE; +} + +static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) +{ + enum bp_state state = BP_DONE; + unsigned long i; + struct page *page, *tmp; + int ret; + LIST_HEAD(pages); + + if (nr_pages > ARRAY_SIZE(frame_list)) + nr_pages = ARRAY_SIZE(frame_list); + + for (i = 0; i < nr_pages; i++) { + page = alloc_page(gfp); + if (page == NULL) { + nr_pages = i; + state = BP_EAGAIN; + break; + } + adjust_managed_page_count(page, -1); + xenmem_reservation_scrub_page(page); + list_add(&page->lru, &pages); + } + + /* + * Ensure that ballooned highmem pages don't have kmaps. + * + * Do this before changing the p2m as kmap_flush_unused() + * reads PTEs to obtain pages (and hence needs the original + * p2m entry). + */ + kmap_flush_unused(); + + /* + * Setup the frame, update direct mapping, invalidate P2M, + * and add to balloon. + */ + i = 0; + list_for_each_entry_safe(page, tmp, &pages, lru) { + frame_list[i++] = xen_page_to_gfn(page); + + xenmem_reservation_va_mapping_reset(1, &page); + + list_del(&page->lru); + + balloon_append(page); + } + + flush_tlb_all(); + + ret = xenmem_reservation_decrease(nr_pages, frame_list); + BUG_ON(ret != nr_pages); + + balloon_stats.current_pages -= nr_pages; + + return state; +} + +/* + * Stop waiting if either state is BP_DONE and ballooning action is + * needed, or if the credit has changed while state is not BP_DONE. + */ +static bool balloon_thread_cond(long credit) +{ + if (balloon_state == BP_DONE) + credit = 0; + + return current_credit() != credit || kthread_should_stop(); +} + +/* + * As this is a kthread it is guaranteed to run as a single instance only. + * 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 int balloon_thread(void *unused) +{ + long credit; + unsigned long timeout; + + set_freezable(); + for (;;) { + switch (balloon_state) { + case BP_DONE: + case BP_ECANCELED: + timeout = 3600 * HZ; + break; + case BP_EAGAIN: + timeout = balloon_stats.schedule_delay * HZ; + break; + case BP_WAIT: + timeout = HZ; + break; + } + + credit = current_credit(); + + wait_event_freezable_timeout(balloon_thread_wq, + balloon_thread_cond(credit), timeout); + + if (kthread_should_stop()) + return 0; + + mutex_lock(&balloon_mutex); + + credit = current_credit(); + + if (credit > 0) { + if (balloon_is_inflated()) + balloon_state = increase_reservation(credit); + else + balloon_state = reserve_additional_memory(); + } + + if (credit < 0) { + long n_pages; + + n_pages = min(-credit, si_mem_available()); + balloon_state = decrease_reservation(n_pages, + GFP_BALLOON); + if (balloon_state == BP_DONE && n_pages != -credit && + n_pages < totalreserve_pages) + balloon_state = BP_EAGAIN; + } + + update_schedule(); + + mutex_unlock(&balloon_mutex); + + cond_resched(); + } +} + +/* 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.target_pages = target; + wake_up(&balloon_thread_wq); +} +EXPORT_SYMBOL_GPL(balloon_set_new_target); + +static int add_ballooned_pages(unsigned int nr_pages) +{ + enum bp_state st; + + if (xen_hotplug_unpopulated) { + st = reserve_additional_memory(); + if (st != BP_ECANCELED) { + int rc; + + mutex_unlock(&balloon_mutex); + rc = wait_event_interruptible(balloon_wq, + !list_empty(&ballooned_pages)); + mutex_lock(&balloon_mutex); + return rc ? -ENOMEM : 0; + } + } + + if (si_mem_available() < nr_pages) + return -ENOMEM; + + st = decrease_reservation(nr_pages, GFP_USER); + if (st != BP_DONE) + return -ENOMEM; + + return 0; +} + +/** + * xen_alloc_ballooned_pages - get pages that have been ballooned out + * @nr_pages: Number of pages to get + * @pages: pages returned + * @return 0 on success, error otherwise + */ +int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages) +{ + unsigned int pgno = 0; + struct page *page; + int ret; + + mutex_lock(&balloon_mutex); + + balloon_stats.target_unpopulated += nr_pages; + + while (pgno < nr_pages) { + page = balloon_retrieve(true); + if (page) { + pages[pgno++] = page; +#ifdef CONFIG_XEN_HAVE_PVMMU + /* + * We don't support PV MMU when Linux and Xen is using + * different page granularity. + */ + BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE); + + if (!xen_feature(XENFEAT_auto_translated_physmap)) { + ret = xen_alloc_p2m_entry(page_to_pfn(page)); + if (ret < 0) + goto out_undo; + } +#endif + } else { + ret = add_ballooned_pages(nr_pages - pgno); + if (ret < 0) + goto out_undo; + } + } + mutex_unlock(&balloon_mutex); + return 0; + out_undo: + mutex_unlock(&balloon_mutex); + xen_free_ballooned_pages(pgno, pages); + /* + * NB: xen_free_ballooned_pages will only subtract pgno pages, but since + * target_unpopulated is incremented with nr_pages at the start we need + * to remove the remaining ones also, or accounting will be screwed. + */ + balloon_stats.target_unpopulated -= nr_pages - pgno; + return ret; +} +EXPORT_SYMBOL(xen_alloc_ballooned_pages); + +/** + * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages + * @nr_pages: Number of pages + * @pages: pages to return + */ +void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages) +{ + unsigned int i; + + mutex_lock(&balloon_mutex); + + for (i = 0; i < nr_pages; i++) { + if (pages[i]) + balloon_append(pages[i]); + } + + balloon_stats.target_unpopulated -= nr_pages; + + /* The balloon may be too large now. Shrink it if needed. */ + if (current_credit()) + wake_up(&balloon_thread_wq); + + mutex_unlock(&balloon_mutex); +} +EXPORT_SYMBOL(xen_free_ballooned_pages); + +static void __init balloon_add_regions(void) +{ +#if defined(CONFIG_XEN_PV) + unsigned long start_pfn, pages; + unsigned long pfn, extra_pfn_end; + unsigned int i; + + for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) { + pages = xen_extra_mem[i].n_pfns; + if (!pages) + continue; + + start_pfn = xen_extra_mem[i].start_pfn; + + /* + * If the amount of usable memory has been limited (e.g., with + * the 'mem' command line parameter), don't add pages beyond + * this limit. + */ + extra_pfn_end = min(max_pfn, start_pfn + pages); + + for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) + balloon_append(pfn_to_page(pfn)); + + balloon_stats.total_pages += extra_pfn_end - start_pfn; + } +#endif +} + +static int __init balloon_init(void) +{ + struct task_struct *task; + + if (!xen_domain()) + return -ENODEV; + + pr_info("Initialising balloon driver\n"); + +#ifdef CONFIG_XEN_PV + balloon_stats.current_pages = xen_pv_domain() + ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn) + : get_num_physpages(); +#else + balloon_stats.current_pages = get_num_physpages(); +#endif + balloon_stats.target_pages = balloon_stats.current_pages; + balloon_stats.balloon_low = 0; + balloon_stats.balloon_high = 0; + balloon_stats.total_pages = balloon_stats.current_pages; + + balloon_stats.schedule_delay = 1; + balloon_stats.max_schedule_delay = 32; + balloon_stats.retry_count = 1; + balloon_stats.max_retry_count = 4; + +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG + set_online_page_callback(&xen_online_page); + register_memory_notifier(&xen_memory_nb); + register_sysctl_table(xen_root); +#endif + + balloon_add_regions(); + + task = kthread_run(balloon_thread, NULL, "xen-balloon"); + if (IS_ERR(task)) { + pr_err("xen-balloon thread could not be started, ballooning will not work!\n"); + return PTR_ERR(task); + } + + /* Init the xen-balloon driver. */ + xen_balloon_init(); + + return 0; +} +subsys_initcall(balloon_init); + +static int __init balloon_wait_finish(void) +{ + long credit, last_credit = 0; + unsigned long last_changed = 0; + + if (!xen_domain()) + return -ENODEV; + + /* PV guests don't need to wait. */ + if (xen_pv_domain() || !current_credit()) + return 0; + + pr_notice("Waiting for initial ballooning down having finished.\n"); + + while ((credit = current_credit()) < 0) { + if (credit != last_credit) { + last_changed = jiffies; + last_credit = credit; + } + if (balloon_state == BP_ECANCELED) { + pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n", + -credit); + if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout)) + panic("Initial ballooning failed!\n"); + } + + schedule_timeout_interruptible(HZ / 10); + } + + pr_notice("Initial ballooning down finished.\n"); + + return 0; +} +late_initcall_sync(balloon_wait_finish); |