731 lines
18 KiB
C
731 lines
18 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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#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
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#include <linux/cpu.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/cred.h>
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#include <linux/errno.h>
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#include <linux/mm.h>
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#include <linux/memblock.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 <linux/percpu-defs.h>
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#include <linux/slab.h>
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#include <linux/sysctl.h>
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#include <asm/page.h>
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#include <asm/tlb.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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#include <xen/mem-reservation.h>
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static int xen_hotplug_unpopulated;
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#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
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static struct ctl_table balloon_table[] = {
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{
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.procname = "hotplug_unpopulated",
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.data = &xen_hotplug_unpopulated,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = SYSCTL_ZERO,
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.extra2 = SYSCTL_ONE,
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},
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{ }
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};
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static struct ctl_table balloon_root[] = {
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{
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.procname = "balloon",
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.mode = 0555,
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.child = balloon_table,
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},
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{ }
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};
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static struct ctl_table xen_root[] = {
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{
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.procname = "xen",
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.mode = 0555,
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.child = balloon_root,
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},
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{ }
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};
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#endif
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/*
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* Use one extent per PAGE_SIZE to avoid to break down the page into
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* multiple frame.
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*/
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#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
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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_WAIT: wait to be rescheduled,
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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_WAIT,
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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 xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
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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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static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
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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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/* 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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__SetPageOffline(page);
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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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wake_up(&balloon_wq);
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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 require_lowmem)
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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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page = list_entry(ballooned_pages.next, struct page, lru);
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if (require_lowmem && PageHighMem(page))
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return NULL;
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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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else
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balloon_stats.balloon_low--;
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__ClearPageOffline(page);
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return page;
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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_WAIT)
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return BP_WAIT;
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if (state == BP_ECANCELED)
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return BP_ECANCELED;
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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 void release_memory_resource(struct resource *resource)
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{
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if (!resource)
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return;
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/*
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* No need to reset region to identity mapped since we now
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* know that no I/O can be in this region
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*/
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release_resource(resource);
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kfree(resource);
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}
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static struct resource *additional_memory_resource(phys_addr_t size)
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{
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struct resource *res;
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int ret;
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res = kzalloc(sizeof(*res), GFP_KERNEL);
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if (!res)
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return NULL;
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res->name = "System RAM";
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res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
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ret = allocate_resource(&iomem_resource, res,
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size, 0, -1,
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PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
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if (ret < 0) {
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pr_err("Cannot allocate new System RAM resource\n");
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kfree(res);
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return NULL;
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}
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return res;
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}
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static enum bp_state reserve_additional_memory(void)
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{
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long credit;
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struct resource *resource;
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int nid, rc;
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unsigned long balloon_hotplug;
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credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
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- balloon_stats.total_pages;
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/*
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* Already hotplugged enough pages? Wait for them to be
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* onlined.
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*/
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if (credit <= 0)
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return BP_WAIT;
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balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
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resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
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if (!resource)
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goto err;
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nid = memory_add_physaddr_to_nid(resource->start);
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#ifdef CONFIG_XEN_HAVE_PVMMU
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/*
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* We don't support PV MMU when Linux and Xen is using
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* different page granularity.
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*/
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BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
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/*
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* add_memory() will build page tables for the new memory so
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* the p2m must contain invalid entries so the correct
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* non-present PTEs will be written.
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*
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* If a failure occurs, the original (identity) p2m entries
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* are not restored since this region is now known not to
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* conflict with any devices.
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*/
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if (!xen_feature(XENFEAT_auto_translated_physmap)) {
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unsigned long pfn, i;
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pfn = PFN_DOWN(resource->start);
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for (i = 0; i < balloon_hotplug; i++) {
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if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
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pr_warn("set_phys_to_machine() failed, no memory added\n");
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goto err;
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}
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}
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}
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#endif
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/*
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* add_memory_resource() will call online_pages() which in its turn
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* will call xen_online_page() callback causing deadlock if we don't
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* release balloon_mutex here. Unlocking here is safe because the
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* callers drop the mutex before trying again.
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*/
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mutex_unlock(&balloon_mutex);
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/* add_memory_resource() requires the device_hotplug lock */
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lock_device_hotplug();
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rc = add_memory_resource(nid, resource, MEMHP_MERGE_RESOURCE);
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unlock_device_hotplug();
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mutex_lock(&balloon_mutex);
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if (rc) {
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pr_warn("Cannot add additional memory (%i)\n", rc);
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goto err;
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}
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balloon_stats.total_pages += balloon_hotplug;
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return BP_WAIT;
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err:
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release_memory_resource(resource);
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return BP_ECANCELED;
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}
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static void xen_online_page(struct page *page, unsigned int order)
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{
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unsigned long i, size = (1 << order);
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unsigned long start_pfn = page_to_pfn(page);
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struct page *p;
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pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
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mutex_lock(&balloon_mutex);
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for (i = 0; i < size; i++) {
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p = pfn_to_page(start_pfn + i);
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balloon_append(p);
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}
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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 enum bp_state reserve_additional_memory(void)
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{
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balloon_stats.target_pages = balloon_stats.current_pages +
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balloon_stats.target_unpopulated;
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return BP_ECANCELED;
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}
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#endif /* 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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}
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static bool balloon_is_inflated(void)
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{
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return balloon_stats.balloon_low || balloon_stats.balloon_high;
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}
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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 i;
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struct page *page;
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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 = list_first_entry_or_null(&ballooned_pages, struct page, lru);
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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_xen_pfn(page);
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page = balloon_next_page(page);
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}
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rc = xenmem_reservation_increase(nr_pages, frame_list);
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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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xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
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/* Relinquish the page back to the allocator. */
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free_reserved_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 i;
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struct page *page, *tmp;
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int ret;
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LIST_HEAD(pages);
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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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page = alloc_page(gfp);
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if (page == 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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adjust_managed_page_count(page, -1);
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xenmem_reservation_scrub_page(page);
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list_add(&page->lru, &pages);
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}
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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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*
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* Do this before changing the p2m as kmap_flush_unused()
|
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* reads PTEs to obtain pages (and hence needs the original
|
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* p2m entry).
|
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*/
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kmap_flush_unused();
|
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|
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/*
|
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* Setup the frame, update direct mapping, invalidate P2M,
|
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* and add to balloon.
|
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*/
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i = 0;
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list_for_each_entry_safe(page, tmp, &pages, lru) {
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frame_list[i++] = xen_page_to_gfn(page);
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|
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xenmem_reservation_va_mapping_reset(1, &page);
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|
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list_del(&page->lru);
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|
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balloon_append(page);
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}
|
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|
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flush_tlb_all();
|
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|
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ret = xenmem_reservation_decrease(nr_pages, frame_list);
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BUG_ON(ret != nr_pages);
|
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|
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balloon_stats.current_pages -= nr_pages;
|
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|
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return state;
|
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}
|
|
|
|
/*
|
|
* 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
|
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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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|
|
|
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do {
|
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mutex_lock(&balloon_mutex);
|
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|
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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();
|
|
}
|
|
|
|
if (credit < 0) {
|
|
long n_pages;
|
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|
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n_pages = min(-credit, si_mem_available());
|
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state = decrease_reservation(n_pages, GFP_BALLOON);
|
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if (state == BP_DONE && n_pages != -credit &&
|
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n_pages < totalreserve_pages)
|
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state = BP_EAGAIN;
|
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}
|
|
|
|
state = update_schedule(state);
|
|
|
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mutex_unlock(&balloon_mutex);
|
|
|
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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);
|
|
|
|
#if defined(CONFIG_XEN_PV) && !defined(CONFIG_XEN_UNPOPULATED_ALLOC)
|
|
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
|
|
|
|
#if defined(CONFIG_XEN_PV) && !defined(CONFIG_XEN_UNPOPULATED_ALLOC)
|
|
{
|
|
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);
|