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![Julien Grall](/assets/img/avatar_default.png)
Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN is meant, I suspect this is because the first support for Xen was for PV. This resulted in some misimplementation of helpers on ARM and confused developers about the expected behavior. For instance, with pfn_to_mfn, we expect to get an MFN based on the name. Although, if we look at the implementation on x86, it's returning a GFN. For clarity and avoid new confusion, replace any reference to mfn with gfn in any helpers used by PV drivers. The x86 code will still keep some reference of pfn_to_mfn which may be used by all kind of guests No changes as been made in the hypercall field, even though they may be invalid, in order to keep the same as the defintion in xen repo. Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a name to close to the KVM function gfn_to_page. Take also the opportunity to simplify simple construction such as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up will come in follow-up patches. [1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cb Signed-off-by: Julien Grall <julien.grall@citrix.com> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Acked-by: Wei Liu <wei.liu2@citrix.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
650 lines
17 KiB
C
650 lines
17 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/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 <linux/percpu-defs.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/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 xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)];
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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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adjust_managed_page_count(page, -1);
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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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else
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balloon_stats.balloon_low--;
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adjust_managed_page_count(page, 1);
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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_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 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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#ifdef CONFIG_XEN_HAVE_PVMMU
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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(hotplug_start_paddr);
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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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return BP_ECANCELED;
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}
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}
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}
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#endif
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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_warn("Cannot add additional memory (%i)\n", rc);
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return BP_ECANCELED;
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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 = 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_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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#ifdef CONFIG_XEN_HAVE_PVMMU
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if (!xen_feature(XENFEAT_auto_translated_physmap)) {
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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 (!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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}
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#endif
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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 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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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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scrub_page(page);
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frame_list[i] = page_to_pfn(page);
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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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/* Update direct mapping, invalidate P2M, and add to balloon. */
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for (i = 0; i < nr_pages; i++) {
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pfn = frame_list[i];
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frame_list[i] = pfn_to_gfn(pfn);
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page = pfn_to_page(pfn);
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#ifdef CONFIG_XEN_HAVE_PVMMU
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if (!xen_feature(XENFEAT_auto_translated_physmap)) {
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if (!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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__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
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}
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#endif
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balloon_append(page);
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}
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flush_tlb_all();
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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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* 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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do {
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mutex_lock(&balloon_mutex);
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credit = current_credit();
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if (credit > 0) {
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if (balloon_is_inflated())
|
|
state = increase_reservation(credit);
|
|
else
|
|
state = reserve_additional_memory(credit);
|
|
}
|
|
|
|
if (credit < 0)
|
|
state = decrease_reservation(-credit, GFP_BALLOON);
|
|
|
|
state = update_schedule(state);
|
|
|
|
mutex_unlock(&balloon_mutex);
|
|
|
|
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);
|
|
|
|
/**
|
|
* alloc_xenballooned_pages - get pages that have been ballooned out
|
|
* @nr_pages: Number of pages to get
|
|
* @pages: pages returned
|
|
* @highmem: allow highmem pages
|
|
* @return 0 on success, error otherwise
|
|
*/
|
|
int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
|
|
{
|
|
int pgno = 0;
|
|
struct page *page;
|
|
mutex_lock(&balloon_mutex);
|
|
while (pgno < nr_pages) {
|
|
page = balloon_retrieve(highmem);
|
|
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("Initialising balloon driver\n");
|
|
|
|
balloon_stats.current_pages = xen_pv_domain()
|
|
? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
|
|
: get_num_physpages();
|
|
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].n_pfns)
|
|
balloon_add_region(xen_extra_mem[i].start_pfn,
|
|
xen_extra_mem[i].n_pfns);
|
|
|
|
return 0;
|
|
}
|
|
|
|
subsys_initcall(balloon_init);
|
|
|
|
MODULE_LICENSE("GPL");
|