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Diffstat (limited to 'drivers/xen/balloon.c')
| -rw-r--r-- | drivers/xen/balloon.c | 476 |
1 files changed, 476 insertions, 0 deletions
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c new file mode 100644 index 00000000..f54290ba --- /dev/null +++ b/drivers/xen/balloon.c @@ -0,0 +1,476 @@ +/****************************************************************************** + * 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"); |