/****************************************************************************** * 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/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/gfp.h> #include <asm/page.h> #include <asm/pgalloc.h> #include <asm/pgtable.h> #include <asm/tlb.h> #include <asm/e820.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> /* * balloon_process() state: * * BP_DONE: done or nothing to do, * BP_EAGAIN: error, go to sleep, * BP_ECANCELED: error, balloon operation canceled. */ enum bp_state { BP_DONE, 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 unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)]; #ifdef CONFIG_HIGHMEM #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_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) 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++; } else { list_add(&page->lru, &ballooned_pages); balloon_stats.balloon_low++; } } static void balloon_append(struct page *page) { __balloon_append(page); if (PageHighMem(page)) dec_totalhigh_pages(); totalram_pages--; } /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */ static struct page *balloon_retrieve(bool prefer_highmem) { struct page *page; if (list_empty(&ballooned_pages)) return NULL; if (prefer_highmem) page = list_entry(ballooned_pages.prev, struct page, lru); else 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--; totalram_pages++; 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 enum bp_state update_schedule(enum bp_state state) { 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; } static long current_credit(void) { unsigned long target = balloon_stats.target_pages; target = min(target, balloon_stats.current_pages + balloon_stats.balloon_low + balloon_stats.balloon_high); return target - balloon_stats.current_pages; } static enum bp_state increase_reservation(unsigned long nr_pages) { int rc; unsigned long pfn, i; struct page *page; 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); page = balloon_first_page(); for (i = 0; i < nr_pages; i++) { if (!page) { nr_pages = i; break; } 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 <= 0) return BP_EAGAIN; for (i = 0; i < rc; i++) { page = balloon_retrieve(false); 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 (xen_pv_domain() && !PageHighMem(page)) { 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 += 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 pfn, i; struct page *page; 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)) == NULL) { nr_pages = i; state = BP_EAGAIN; break; } pfn = page_to_pfn(page); frame_list[i] = pfn_to_mfn(pfn); scrub_page(page); if (xen_pv_domain() && !PageHighMem(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(); /* 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; return state; } /* * 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) { enum bp_state state = BP_DONE; long credit; mutex_lock(&balloon_mutex); do { credit = current_credit(); if (credit > 0) state = increase_reservation(credit); if (credit < 0) state = decrease_reservation(-credit, GFP_BALLOON); state = update_schedule(state); #ifndef CONFIG_PREEMPT if (need_resched()) schedule(); #endif } 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); 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.target_pages = target; schedule_delayed_work(&balloon_worker, 0); } EXPORT_SYMBOL_GPL(balloon_set_new_target); /** * 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; mutex_lock(&balloon_mutex); while (pgno < nr_pages) { page = balloon_retrieve(true); if (page) { pages[pgno++] = page; } else { enum bp_state st; st = decrease_reservation(nr_pages - pgno, GFP_HIGHUSER); if (st != BP_DONE) goto out_undo; } } mutex_unlock(&balloon_mutex); return 0; out_undo: while (pgno) balloon_append(pages[--pgno]); /* Free the memory back to the kernel soon */ schedule_delayed_work(&balloon_worker, 0); mutex_unlock(&balloon_mutex); return -ENOMEM; } 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]); } /* 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); static int __init balloon_init(void) { unsigned long pfn, extra_pfn_end; struct page *page; if (!xen_domain()) return -ENODEV; pr_info("xen/balloon: Initialising balloon driver.\n"); balloon_stats.current_pages = xen_pv_domain() ? min(xen_start_info->nr_pages, max_pfn) : max_pfn; balloon_stats.target_pages = balloon_stats.current_pages; balloon_stats.balloon_low = 0; balloon_stats.balloon_high = 0; balloon_stats.schedule_delay = 1; balloon_stats.max_schedule_delay = 32; balloon_stats.retry_count = 1; balloon_stats.max_retry_count = RETRY_UNLIMITED; /* * Initialise the balloon with excess memory space. We need * to make sure we don't add memory which doesn't exist or * logically exist. The E820 map can be trimmed to be smaller * than the amount of physical memory due to the mem= command * line parameter. And if this is a 32-bit non-HIGHMEM kernel * on a system with memory which requires highmem to access, * don't try to use it. */ extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()), (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size)); for (pfn = PFN_UP(xen_extra_mem_start); pfn < extra_pfn_end; pfn++) { page = pfn_to_page(pfn); /* totalram_pages and totalhigh_pages do not include the boot-time balloon extension, so don't subtract from it. */ __balloon_append(page); } return 0; } subsys_initcall(balloon_init); MODULE_LICENSE("GPL");