| /****************************************************************************** |
| * 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/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 <asm/page.h> |
| #include <asm/pgalloc.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> |
| |
| static int xen_hotplug_unpopulated; |
| |
| #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG |
| |
| 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, |
| }, |
| { } |
| }; |
| |
| #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_process() 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. |
| */ |
| |
| enum bp_state { |
| BP_DONE, |
| BP_WAIT, |
| BP_EAGAIN, |
| BP_ECANCELED |
| }; |
| |
| |
| 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); |
| |
| /* Main work function, always executed in process context. */ |
| static void balloon_process(struct work_struct *work); |
| static DECLARE_DELAYED_WORK(balloon_worker, balloon_process); |
| |
| /* 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 enum bp_state update_schedule(enum bp_state state) |
| { |
| if (state == BP_WAIT) |
| return BP_WAIT; |
| |
| if (state == BP_ECANCELED) |
| return BP_ECANCELED; |
| |
| if (state == BP_DONE) { |
| balloon_stats.schedule_delay = 1; |
| balloon_stats.retry_count = 1; |
| return BP_DONE; |
| } |
| |
| ++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; |
| return BP_ECANCELED; |
| } |
| |
| balloon_stats.schedule_delay <<= 1; |
| |
| if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay) |
| balloon_stats.schedule_delay = balloon_stats.max_schedule_delay; |
| |
| return 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); |
| 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) |
| schedule_delayed_work(&balloon_worker, 0); |
| |
| 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; |
| } |
| |
| /* |
| * As this is a work item 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 void balloon_process(struct work_struct *work) |
| { |
| enum bp_state state = BP_DONE; |
| long credit; |
| |
| |
| do { |
| mutex_lock(&balloon_mutex); |
| |
| credit = current_credit(); |
| |
| if (credit > 0) { |
| if (balloon_is_inflated()) |
| state = increase_reservation(credit); |
| else |
| state = reserve_additional_memory(); |
| } |
| |
| if (credit < 0) { |
| long n_pages; |
| |
| n_pages = min(-credit, si_mem_available()); |
| state = decrease_reservation(n_pages, GFP_BALLOON); |
| if (state == BP_DONE && n_pages != -credit && |
| n_pages < totalreserve_pages) |
| state = BP_EAGAIN; |
| } |
| |
| state = update_schedule(state); |
| |
| mutex_unlock(&balloon_mutex); |
| |
| cond_resched(); |
| |
| } while (credit && state == BP_DONE); |
| |
| /* Schedule more work if there is some still to be done. */ |
| if (state == BP_EAGAIN) |
| schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ); |
| } |
| |
| /* 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; |
| schedule_delayed_work(&balloon_worker, 0); |
| } |
| EXPORT_SYMBOL_GPL(balloon_set_new_target); |
| |
| static int add_ballooned_pages(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; |
| } |
| |
| /** |
| * alloc_xenballooned_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 alloc_xenballooned_pages(int nr_pages, struct page **pages) |
| { |
| 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); |
| free_xenballooned_pages(pgno, pages); |
| /* |
| * NB: free_xenballooned_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(alloc_xenballooned_pages); |
| |
| /** |
| * free_xenballooned_pages - return pages retrieved with get_ballooned_pages |
| * @nr_pages: Number of pages |
| * @pages: pages to return |
| */ |
| void free_xenballooned_pages(int nr_pages, struct page **pages) |
| { |
| 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()) |
| schedule_delayed_work(&balloon_worker, 0); |
| |
| mutex_unlock(&balloon_mutex); |
| } |
| EXPORT_SYMBOL(free_xenballooned_pages); |
| |
| #ifdef CONFIG_XEN_PV |
| static void __init balloon_add_region(unsigned long start_pfn, |
| unsigned long pages) |
| { |
| unsigned long pfn, extra_pfn_end; |
| |
| /* |
| * 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++) { |
| /* totalram_pages and totalhigh_pages do not |
| include the boot-time balloon extension, so |
| don't subtract from it. */ |
| balloon_append(pfn_to_page(pfn)); |
| } |
| |
| balloon_stats.total_pages += extra_pfn_end - start_pfn; |
| } |
| #endif |
| |
| static int __init balloon_init(void) |
| { |
| 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 |
| |
| #ifdef CONFIG_XEN_PV |
| { |
| int i; |
| |
| /* |
| * Initialize the balloon with pages from the extra memory |
| * regions (see arch/x86/xen/setup.c). |
| */ |
| for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) |
| if (xen_extra_mem[i].n_pfns) |
| balloon_add_region(xen_extra_mem[i].start_pfn, |
| xen_extra_mem[i].n_pfns); |
| } |
| #endif |
| |
| /* Init the xen-balloon driver. */ |
| xen_balloon_init(); |
| |
| return 0; |
| } |
| subsys_initcall(balloon_init); |