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If highmem pages are requested from the balloon on a system without highmem, the implementation of alloc_xenballooned_pages will allocate all available memory trying to find highmem pages to return. Allow low memory to be returned when highmem pages are requested to avoid this loop. Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
628 lines
16 KiB
C
628 lines
16 KiB
C
/******************************************************************************
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* Xen balloon driver - enables returning/claiming memory to/from Xen.
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*
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* Copyright (c) 2003, B Dragovic
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* Copyright (c) 2003-2004, M Williamson, K Fraser
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* Copyright (c) 2005 Dan M. Smith, IBM Corporation
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* Copyright (c) 2010 Daniel Kiper
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*
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* Memory hotplug support was written by Daniel Kiper. Work on
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* it was sponsored by Google under Google Summer of Code 2010
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* program. Jeremy Fitzhardinge from Citrix was the mentor for
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* this project.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation; or, when distributed
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* separately from the Linux kernel or incorporated into other
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* software packages, subject to the following license:
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this source file (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use, copy, modify,
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* merge, publish, distribute, sublicense, and/or sell copies of the Software,
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* and to permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/errno.h>
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <linux/bootmem.h>
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#include <linux/pagemap.h>
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#include <linux/highmem.h>
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#include <linux/mutex.h>
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#include <linux/list.h>
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#include <linux/gfp.h>
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#include <linux/notifier.h>
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#include <linux/memory.h>
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#include <linux/memory_hotplug.h>
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#include <asm/page.h>
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#include <asm/pgalloc.h>
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#include <asm/pgtable.h>
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#include <asm/tlb.h>
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#include <asm/e820.h>
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#include <asm/xen/hypervisor.h>
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#include <asm/xen/hypercall.h>
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#include <xen/xen.h>
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#include <xen/interface/xen.h>
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#include <xen/interface/memory.h>
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#include <xen/balloon.h>
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#include <xen/features.h>
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#include <xen/page.h>
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/*
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* balloon_process() state:
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*
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* BP_DONE: done or nothing to do,
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* BP_EAGAIN: error, go to sleep,
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* BP_ECANCELED: error, balloon operation canceled.
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*/
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enum bp_state {
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BP_DONE,
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BP_EAGAIN,
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BP_ECANCELED
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};
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static DEFINE_MUTEX(balloon_mutex);
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struct balloon_stats balloon_stats;
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EXPORT_SYMBOL_GPL(balloon_stats);
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/* We increase/decrease in batches which fit in a page */
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static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
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#ifdef CONFIG_HIGHMEM
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#define inc_totalhigh_pages() (totalhigh_pages++)
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#define dec_totalhigh_pages() (totalhigh_pages--)
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#else
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#define inc_totalhigh_pages() do {} while (0)
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#define dec_totalhigh_pages() do {} while (0)
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#endif
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/* List of ballooned pages, threaded through the mem_map array. */
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static LIST_HEAD(ballooned_pages);
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/* Main work function, always executed in process context. */
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static void balloon_process(struct work_struct *work);
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static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
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/* When ballooning out (allocating memory to return to Xen) we don't really
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want the kernel to try too hard since that can trigger the oom killer. */
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#define GFP_BALLOON \
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(GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
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static void scrub_page(struct page *page)
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{
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#ifdef CONFIG_XEN_SCRUB_PAGES
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clear_highpage(page);
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#endif
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}
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/* balloon_append: add the given page to the balloon. */
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static void __balloon_append(struct page *page)
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{
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/* Lowmem is re-populated first, so highmem pages go at list tail. */
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if (PageHighMem(page)) {
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list_add_tail(&page->lru, &ballooned_pages);
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balloon_stats.balloon_high++;
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} else {
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list_add(&page->lru, &ballooned_pages);
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balloon_stats.balloon_low++;
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}
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}
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static void balloon_append(struct page *page)
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{
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__balloon_append(page);
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if (PageHighMem(page))
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dec_totalhigh_pages();
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totalram_pages--;
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}
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/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
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static struct page *balloon_retrieve(bool prefer_highmem)
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{
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struct page *page;
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if (list_empty(&ballooned_pages))
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return NULL;
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if (prefer_highmem)
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page = list_entry(ballooned_pages.prev, struct page, lru);
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else
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page = list_entry(ballooned_pages.next, struct page, lru);
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list_del(&page->lru);
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if (PageHighMem(page)) {
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balloon_stats.balloon_high--;
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inc_totalhigh_pages();
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} else
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balloon_stats.balloon_low--;
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totalram_pages++;
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return page;
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}
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static struct page *balloon_first_page(void)
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{
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if (list_empty(&ballooned_pages))
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return NULL;
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return list_entry(ballooned_pages.next, struct page, lru);
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}
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static struct page *balloon_next_page(struct page *page)
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{
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struct list_head *next = page->lru.next;
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if (next == &ballooned_pages)
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return NULL;
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return list_entry(next, struct page, lru);
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}
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static enum bp_state update_schedule(enum bp_state state)
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{
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if (state == BP_DONE) {
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balloon_stats.schedule_delay = 1;
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balloon_stats.retry_count = 1;
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return BP_DONE;
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}
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++balloon_stats.retry_count;
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if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
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balloon_stats.retry_count > balloon_stats.max_retry_count) {
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balloon_stats.schedule_delay = 1;
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balloon_stats.retry_count = 1;
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return BP_ECANCELED;
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}
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balloon_stats.schedule_delay <<= 1;
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if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
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balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
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return BP_EAGAIN;
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}
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#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
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static long current_credit(void)
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{
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return balloon_stats.target_pages - balloon_stats.current_pages -
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balloon_stats.hotplug_pages;
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}
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static bool balloon_is_inflated(void)
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{
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if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
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balloon_stats.balloon_hotplug)
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return true;
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else
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return false;
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}
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/*
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* reserve_additional_memory() adds memory region of size >= credit above
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* max_pfn. New region is section aligned and size is modified to be multiple
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* of section size. Those features allow optimal use of address space and
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* establish proper alignment when this function is called first time after
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* boot (last section not fully populated at boot time contains unused memory
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* pages with PG_reserved bit not set; online_pages_range() does not allow page
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* onlining in whole range if first onlined page does not have PG_reserved
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* bit set). Real size of added memory is established at page onlining stage.
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*/
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static enum bp_state reserve_additional_memory(long credit)
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{
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int nid, rc;
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u64 hotplug_start_paddr;
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unsigned long balloon_hotplug = credit;
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hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
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balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
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nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
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rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
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if (rc) {
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pr_info("xen_balloon: %s: add_memory() failed: %i\n", __func__, rc);
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return BP_EAGAIN;
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}
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balloon_hotplug -= credit;
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balloon_stats.hotplug_pages += credit;
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balloon_stats.balloon_hotplug = balloon_hotplug;
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return BP_DONE;
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}
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static void xen_online_page(struct page *page)
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{
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__online_page_set_limits(page);
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mutex_lock(&balloon_mutex);
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__balloon_append(page);
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if (balloon_stats.hotplug_pages)
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--balloon_stats.hotplug_pages;
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else
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--balloon_stats.balloon_hotplug;
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mutex_unlock(&balloon_mutex);
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}
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static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
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{
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if (val == MEM_ONLINE)
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schedule_delayed_work(&balloon_worker, 0);
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return NOTIFY_OK;
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}
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static struct notifier_block xen_memory_nb = {
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.notifier_call = xen_memory_notifier,
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.priority = 0
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};
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#else
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static long current_credit(void)
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{
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unsigned long target = balloon_stats.target_pages;
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target = min(target,
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balloon_stats.current_pages +
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balloon_stats.balloon_low +
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balloon_stats.balloon_high);
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return target - balloon_stats.current_pages;
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}
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static bool balloon_is_inflated(void)
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{
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if (balloon_stats.balloon_low || balloon_stats.balloon_high)
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return true;
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else
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return false;
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}
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static enum bp_state reserve_additional_memory(long credit)
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{
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balloon_stats.target_pages = balloon_stats.current_pages;
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return BP_DONE;
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}
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#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
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static enum bp_state increase_reservation(unsigned long nr_pages)
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{
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int rc;
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unsigned long pfn, i;
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struct page *page;
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struct xen_memory_reservation reservation = {
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.address_bits = 0,
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.extent_order = 0,
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.domid = DOMID_SELF
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};
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#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
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if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
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nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
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balloon_stats.hotplug_pages += nr_pages;
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balloon_stats.balloon_hotplug -= nr_pages;
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return BP_DONE;
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}
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#endif
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if (nr_pages > ARRAY_SIZE(frame_list))
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nr_pages = ARRAY_SIZE(frame_list);
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page = balloon_first_page();
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for (i = 0; i < nr_pages; i++) {
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if (!page) {
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nr_pages = i;
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break;
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}
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frame_list[i] = page_to_pfn(page);
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page = balloon_next_page(page);
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}
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set_xen_guest_handle(reservation.extent_start, frame_list);
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reservation.nr_extents = nr_pages;
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rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
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if (rc <= 0)
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return BP_EAGAIN;
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for (i = 0; i < rc; i++) {
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page = balloon_retrieve(false);
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BUG_ON(page == NULL);
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pfn = page_to_pfn(page);
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BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
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phys_to_machine_mapping_valid(pfn));
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set_phys_to_machine(pfn, frame_list[i]);
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/* Link back into the page tables if not highmem. */
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if (xen_pv_domain() && !PageHighMem(page)) {
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int ret;
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ret = HYPERVISOR_update_va_mapping(
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(unsigned long)__va(pfn << PAGE_SHIFT),
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mfn_pte(frame_list[i], PAGE_KERNEL),
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0);
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BUG_ON(ret);
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}
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/* Relinquish the page back to the allocator. */
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ClearPageReserved(page);
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init_page_count(page);
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__free_page(page);
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}
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balloon_stats.current_pages += rc;
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return BP_DONE;
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}
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static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
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{
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enum bp_state state = BP_DONE;
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unsigned long pfn, i;
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struct page *page;
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int ret;
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struct xen_memory_reservation reservation = {
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.address_bits = 0,
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.extent_order = 0,
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.domid = DOMID_SELF
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};
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#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
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if (balloon_stats.hotplug_pages) {
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nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
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balloon_stats.hotplug_pages -= nr_pages;
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balloon_stats.balloon_hotplug += nr_pages;
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return BP_DONE;
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}
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#endif
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if (nr_pages > ARRAY_SIZE(frame_list))
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nr_pages = ARRAY_SIZE(frame_list);
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for (i = 0; i < nr_pages; i++) {
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if ((page = alloc_page(gfp)) == NULL) {
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nr_pages = i;
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state = BP_EAGAIN;
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break;
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}
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pfn = page_to_pfn(page);
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frame_list[i] = pfn_to_mfn(pfn);
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scrub_page(page);
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if (xen_pv_domain() && !PageHighMem(page)) {
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ret = HYPERVISOR_update_va_mapping(
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(unsigned long)__va(pfn << PAGE_SHIFT),
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__pte_ma(0), 0);
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BUG_ON(ret);
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}
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}
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/* Ensure that ballooned highmem pages don't have kmaps. */
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kmap_flush_unused();
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flush_tlb_all();
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/* No more mappings: invalidate P2M and add to balloon. */
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for (i = 0; i < nr_pages; i++) {
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pfn = mfn_to_pfn(frame_list[i]);
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__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
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balloon_append(pfn_to_page(pfn));
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}
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set_xen_guest_handle(reservation.extent_start, frame_list);
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reservation.nr_extents = nr_pages;
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ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
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BUG_ON(ret != nr_pages);
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balloon_stats.current_pages -= nr_pages;
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return state;
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}
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/*
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* We avoid multiple worker processes conflicting via the balloon mutex.
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* We may of course race updates of the target counts (which are protected
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* by the balloon lock), or with changes to the Xen hard limit, but we will
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* recover from these in time.
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*/
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static void balloon_process(struct work_struct *work)
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{
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enum bp_state state = BP_DONE;
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long credit;
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mutex_lock(&balloon_mutex);
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do {
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credit = current_credit();
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if (credit > 0) {
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if (balloon_is_inflated())
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state = increase_reservation(credit);
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else
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state = reserve_additional_memory(credit);
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}
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if (credit < 0)
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state = decrease_reservation(-credit, GFP_BALLOON);
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state = update_schedule(state);
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#ifndef CONFIG_PREEMPT
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if (need_resched())
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schedule();
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#endif
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} while (credit && state == BP_DONE);
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/* Schedule more work if there is some still to be done. */
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if (state == BP_EAGAIN)
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schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
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mutex_unlock(&balloon_mutex);
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}
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/* Resets the Xen limit, sets new target, and kicks off processing. */
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void balloon_set_new_target(unsigned long target)
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{
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/* No need for lock. Not read-modify-write updates. */
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balloon_stats.target_pages = target;
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schedule_delayed_work(&balloon_worker, 0);
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}
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EXPORT_SYMBOL_GPL(balloon_set_new_target);
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/**
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* alloc_xenballooned_pages - get pages that have been ballooned out
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* @nr_pages: Number of pages to get
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* @pages: pages returned
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* @highmem: allow highmem pages
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* @return 0 on success, error otherwise
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*/
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int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
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{
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int pgno = 0;
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struct page *page;
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mutex_lock(&balloon_mutex);
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while (pgno < nr_pages) {
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page = balloon_retrieve(highmem);
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if (page && (highmem || !PageHighMem(page))) {
|
|
pages[pgno++] = page;
|
|
} else {
|
|
enum bp_state st;
|
|
if (page)
|
|
balloon_append(page);
|
|
st = decrease_reservation(nr_pages - pgno,
|
|
highmem ? GFP_HIGHUSER : GFP_USER);
|
|
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 void __init balloon_add_region(unsigned long start_pfn,
|
|
unsigned long pages)
|
|
{
|
|
unsigned long pfn, extra_pfn_end;
|
|
struct page *page;
|
|
|
|
/*
|
|
* 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++) {
|
|
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);
|
|
}
|
|
}
|
|
|
|
static int __init balloon_init(void)
|
|
{
|
|
int i;
|
|
|
|
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 - xen_released_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;
|
|
|
|
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
|
|
balloon_stats.hotplug_pages = 0;
|
|
balloon_stats.balloon_hotplug = 0;
|
|
|
|
set_online_page_callback(&xen_online_page);
|
|
register_memory_notifier(&xen_memory_nb);
|
|
#endif
|
|
|
|
/*
|
|
* 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].size)
|
|
balloon_add_region(PFN_UP(xen_extra_mem[i].start),
|
|
PFN_DOWN(xen_extra_mem[i].size));
|
|
|
|
return 0;
|
|
}
|
|
|
|
subsys_initcall(balloon_init);
|
|
|
|
MODULE_LICENSE("GPL");
|