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730 lines
18 KiB
730 lines
18 KiB
/****************************************************************************** |
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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, MHP_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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|
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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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* 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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* 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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xenmem_reservation_va_mapping_reset(1, &page); |
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list_del(&page->lru); |
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balloon_append(page); |
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} |
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flush_tlb_all(); |
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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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balloon_stats.current_pages -= nr_pages; |
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|
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return state; |
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} |
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/* |
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* As this is a work item it is guaranteed to run as a single instance only. |
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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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|
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do { |
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mutex_lock(&balloon_mutex); |
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credit = current_credit(); |
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|
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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(); |
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} |
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|
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if (credit < 0) { |
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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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} |
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state = update_schedule(state); |
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|
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mutex_unlock(&balloon_mutex); |
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cond_resched(); |
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|
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} while (credit && state == BP_DONE); |
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|
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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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} |
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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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static int add_ballooned_pages(int nr_pages) |
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{ |
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enum bp_state st; |
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|
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if (xen_hotplug_unpopulated) { |
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st = reserve_additional_memory(); |
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if (st != BP_ECANCELED) { |
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int rc; |
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mutex_unlock(&balloon_mutex); |
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rc = wait_event_interruptible(balloon_wq, |
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!list_empty(&ballooned_pages)); |
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mutex_lock(&balloon_mutex); |
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return rc ? -ENOMEM : 0; |
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} |
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} |
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if (si_mem_available() < nr_pages) |
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return -ENOMEM; |
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st = decrease_reservation(nr_pages, GFP_USER); |
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if (st != BP_DONE) |
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return -ENOMEM; |
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return 0; |
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} |
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|
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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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* @return 0 on success, error otherwise |
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*/ |
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int alloc_xenballooned_pages(int nr_pages, struct page **pages) |
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{ |
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int pgno = 0; |
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struct page *page; |
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int ret; |
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mutex_lock(&balloon_mutex); |
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balloon_stats.target_unpopulated += nr_pages; |
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|
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while (pgno < nr_pages) { |
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page = balloon_retrieve(true); |
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if (page) { |
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pages[pgno++] = page; |
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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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if (!xen_feature(XENFEAT_auto_translated_physmap)) { |
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ret = xen_alloc_p2m_entry(page_to_pfn(page)); |
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if (ret < 0) |
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goto out_undo; |
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} |
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#endif |
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} 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);
|
|
|