| /****************************************************************************** |
| * 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++; |
| dec_totalhigh_pages(); |
| } else { |
| list_add(&page->lru, &ballooned_pages); |
| balloon_stats.balloon_low++; |
| } |
| } |
| |
| static void balloon_append(struct page *page) |
| { |
| __balloon_append(page); |
| 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 unsigned long current_target(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; |
| } |
| |
| 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_hvm_domain() && 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 += 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_hvm_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_target() - balloon_stats.current_pages; |
| |
| 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_target() != balloon_stats.current_pages) |
| schedule_delayed_work(&balloon_worker, 0); |
| |
| mutex_unlock(&balloon_mutex); |
| } |
| EXPORT_SYMBOL(free_xenballooned_pages); |
| |
| static int __init balloon_init(void) |
| { |
| unsigned long pfn, nr_pages, extra_pfn_end; |
| struct page *page; |
| |
| if (!xen_domain()) |
| return -ENODEV; |
| |
| pr_info("xen/balloon: Initialising balloon driver.\n"); |
| |
| if (xen_pv_domain()) |
| nr_pages = xen_start_info->nr_pages; |
| else |
| nr_pages = max_pfn; |
| balloon_stats.current_pages = min(nr_pages, 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 doesn't include the boot-time |
| balloon extension, so don't subtract from it. */ |
| __balloon_append(page); |
| } |
| |
| return 0; |
| } |
| |
| subsys_initcall(balloon_init); |
| |
| MODULE_LICENSE("GPL"); |