/******************************************************************************
* Xen balloon driver - enables returning/claiming memory to/from Xen.
*
* Copyright (c) 2003, B Dragovic
* Copyright (c) 2003-2004, M Williamson, K Fraser
* Copyright (c) 2005 Dan M. Smith, IBM Corporation
* Copyright (c) 2010 Daniel Kiper
*
* Memory hotplug support was written by Daniel Kiper. Work on
* it was sponsored by Google under Google Summer of Code 2010
* program. Jeremy Fitzhardinge from Citrix was the mentor for
* this project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
#include <linux/cpu.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/errno.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/mm.h>
#include <linux/memblock.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/gfp.h>
#include <linux/notifier.h>
#include <linux/memory.h>
#include <linux/memory_hotplug.h>
#include <linux/percpu-defs.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/moduleparam.h>
#include <linux/jiffies.h>
#include <asm/page.h>
#include <asm/tlb.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/interface/memory.h>
#include <xen/balloon.h>
#include <xen/features.h>
#include <xen/page.h>
#include <xen/mem-reservation.h>
#undef MODULE_PARAM_PREFIX
#define MODULE_PARAM_PREFIX "xen."
static uint __read_mostly balloon_boot_timeout = 180;
module_param(balloon_boot_timeout, uint, 0444);
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
static int xen_hotplug_unpopulated;
static struct ctl_table balloon_table[] = {
{
.procname = "hotplug_unpopulated",
.data = &xen_hotplug_unpopulated,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
};
#else
#define xen_hotplug_unpopulated 0
#endif
/*
* Use one extent per PAGE_SIZE to avoid to break down the page into
* multiple frame.
*/
#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
/*
* balloon_thread() state:
*
* BP_DONE: done or nothing to do,
* BP_WAIT: wait to be rescheduled,
* BP_EAGAIN: error, go to sleep,
* BP_ECANCELED: error, balloon operation canceled.
*/
static enum bp_state {
BP_DONE,
BP_WAIT,
BP_EAGAIN,
BP_ECANCELED
} balloon_state = BP_DONE;
/* Main waiting point for xen-balloon thread. */
static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq);
static DEFINE_MUTEX(balloon_mutex);
struct balloon_stats balloon_stats;
EXPORT_SYMBOL_GPL(balloon_stats);
/* We increase/decrease in batches which fit in a page */
static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
/* List of ballooned pages, threaded through the mem_map array. */
static LIST_HEAD(ballooned_pages);
static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
/* When ballooning out (allocating memory to return to Xen) we don't really
want the kernel to try too hard since that can trigger the oom killer. */
#define GFP_BALLOON \
(GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
/* balloon_append: add the given page to the balloon. */
static void balloon_append(struct page *page)
{
if (!PageOffline(page))
__SetPageOffline(page);
/* Lowmem is re-populated first, so highmem pages go at list tail. */
if (PageHighMem(page)) {
list_add_tail(&page->lru, &ballooned_pages);
balloon_stats.balloon_high++;
} else {
list_add(&page->lru, &ballooned_pages);
balloon_stats.balloon_low++;
}
wake_up(&balloon_wq);
}
/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
static struct page *balloon_retrieve(bool require_lowmem)
{
struct page *page;
if (list_empty(&ballooned_pages))
return NULL;
page = list_entry(ballooned_pages.next, struct page, lru);
if (require_lowmem && PageHighMem(page))
return NULL;
list_del(&page->lru);
if (PageHighMem(page))
balloon_stats.balloon_high--;
else
balloon_stats.balloon_low--;
__ClearPageOffline(page);
return page;
}
static struct page *balloon_next_page(struct page *page)
{
struct list_head *next = page->lru.next;
if (next == &ballooned_pages)
return NULL;
return list_entry(next, struct page, lru);
}
static void update_schedule(void)
{
if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED)
return;
if (balloon_state == BP_DONE) {
balloon_stats.schedule_delay = 1;
balloon_stats.retry_count = 1;
return;
}
++balloon_stats.retry_count;
if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
balloon_stats.retry_count > balloon_stats.max_retry_count) {
balloon_stats.schedule_delay = 1;
balloon_stats.retry_count = 1;
balloon_state = BP_ECANCELED;
return;
}
balloon_stats.schedule_delay <<= 1;
if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
balloon_state = BP_EAGAIN;
}
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
static void release_memory_resource(struct resource *resource)
{
if (!resource)
return;
/*
* No need to reset region to identity mapped since we now
* know that no I/O can be in this region
*/
release_resource(resource);
kfree(resource);
}
static struct resource *additional_memory_resource(phys_addr_t size)
{
struct resource *res;
int ret;
res = kzalloc(sizeof(*res), GFP_KERNEL);
if (!res)
return NULL;
res->name = "System RAM";
res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
ret = allocate_resource(&iomem_resource, res,
size, 0, -1,
PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
if (ret < 0) {
pr_err("Cannot allocate new System RAM resource\n");
kfree(res);
return NULL;
}
return res;
}
static enum bp_state reserve_additional_memory(void)
{
long credit;
struct resource *resource;
int nid, rc;
unsigned long balloon_hotplug;
credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
- balloon_stats.total_pages;
/*
* Already hotplugged enough pages? Wait for them to be
* onlined.
*/
if (credit <= 0)
return BP_WAIT;
balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
if (!resource)
goto err;
nid = memory_add_physaddr_to_nid(resource->start);
#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);
/*
* add_memory() will build page tables for the new memory so
* the p2m must contain invalid entries so the correct
* non-present PTEs will be written.
*
* If a failure occurs, the original (identity) p2m entries
* are not restored since this region is now known not to
* conflict with any devices.
*/
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long pfn, i;
pfn = PFN_DOWN(resource->start);
for (i = 0; i < balloon_hotplug; i++) {
if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
pr_warn("set_phys_to_machine() failed, no memory added\n");
goto err;
}
}
}
#endif
/*
* add_memory_resource() will call online_pages() which in its turn
* will call xen_online_page() callback causing deadlock if we don't
* release balloon_mutex here. Unlocking here is safe because the
* callers drop the mutex before trying again.
*/
mutex_unlock(&balloon_mutex);
/* add_memory_resource() requires the device_hotplug lock */
lock_device_hotplug();
rc = add_memory_resource(nid, resource, MHP_MERGE_RESOURCE);
unlock_device_hotplug();
mutex_lock(&balloon_mutex);
if (rc) {
pr_warn("Cannot add additional memory (%i)\n", rc);
goto err;
}
balloon_stats.total_pages += balloon_hotplug;
return BP_WAIT;
err:
release_memory_resource(resource);
return BP_ECANCELED;
}
static void xen_online_page(struct page *page, unsigned int order)
{
unsigned long i, size = (1 << order);
unsigned long start_pfn = page_to_pfn(page);
struct page *p;
pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
mutex_lock(&balloon_mutex);
for (i = 0; i < size; i++) {
p = pfn_to_page(start_pfn + i);
balloon_append(p);
}
mutex_unlock(&balloon_mutex);
}
static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
{
if (val == MEM_ONLINE)
wake_up(&balloon_thread_wq);
return NOTIFY_OK;
}
static struct notifier_block xen_memory_nb = {
.notifier_call = xen_memory_notifier,
.priority = 0
};
#else
static enum bp_state reserve_additional_memory(void)
{
balloon_stats.target_pages = balloon_stats.current_pages +
balloon_stats.target_unpopulated;
return BP_ECANCELED;
}
#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
static long current_credit(void)
{
return balloon_stats.target_pages - balloon_stats.current_pages;
}
static bool balloon_is_inflated(void)
{
return balloon_stats.balloon_low || balloon_stats.balloon_high;
}
static enum bp_state increase_reservation(unsigned long nr_pages)
{
int rc;
unsigned long i;
struct page *page;
if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list);
page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
for (i = 0; i < nr_pages; i++) {
if (!page) {
nr_pages = i;
break;
}
frame_list[i] = page_to_xen_pfn(page);
page = balloon_next_page(page);
}
rc = xenmem_reservation_increase(nr_pages, frame_list);
if (rc <= 0)
return BP_EAGAIN;
for (i = 0; i < rc; i++) {
page = balloon_retrieve(false);
BUG_ON(page == NULL);
xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
/*
* Relinquish the page back to the allocator. Note that
* some pages, including ones added via xen_online_page(), might
* not be marked reserved; free_reserved_page() will handle that.
*/
free_reserved_page(page);
}
balloon_stats.current_pages += rc;
return BP_DONE;
}
static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
{
enum bp_state state = BP_DONE;
unsigned long i;
struct page *page, *tmp;
int ret;
LIST_HEAD(pages);
if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list);
for (i = 0; i < nr_pages; i++) {
page = alloc_page(gfp);
if (page == NULL) {
nr_pages = i;
state = BP_EAGAIN;
break;
}
adjust_managed_page_count(page, -1);
xenmem_reservation_scrub_page(page);
list_add(&page->lru, &pages);
}
/*
* Ensure that ballooned highmem pages don't have kmaps.
*
* Do this before changing the p2m as kmap_flush_unused()
* reads PTEs to obtain pages (and hence needs the original
* p2m entry).
*/
kmap_flush_unused();
/*
* Setup the frame, update direct mapping, invalidate P2M,
* and add to balloon.
*/
i = 0;
list_for_each_entry_safe(page, tmp, &pages, lru) {
frame_list[i++] = xen_page_to_gfn(page);
xenmem_reservation_va_mapping_reset(1, &page);
list_del(&page->lru);
balloon_append(page);
}
flush_tlb_all();
ret = xenmem_reservation_decrease(nr_pages, frame_list);
BUG_ON(ret != nr_pages);
balloon_stats.current_pages -= nr_pages;
return state;
}
/*
* Stop waiting if either state is BP_DONE and ballooning action is
* needed, or if the credit has changed while state is not BP_DONE.
*/
static bool balloon_thread_cond(long credit)
{
if (balloon_state == BP_DONE)
credit = 0;
return current_credit() != credit || kthread_should_stop();
}
/*
* As this is a kthread it is guaranteed to run as a single instance only.
* We may of course race updates of the target counts (which are protected
* by the balloon lock), or with changes to the Xen hard limit, but we will
* recover from these in time.
*/
static int balloon_thread(void *unused)
{
long credit;
unsigned long timeout;
set_freezable();
for (;;) {
switch (balloon_state) {
case BP_DONE:
case BP_ECANCELED:
timeout = 3600 * HZ;
break;
case BP_EAGAIN:
timeout = balloon_stats.schedule_delay * HZ;
break;
case BP_WAIT:
timeout = HZ;
break;
}
credit = current_credit();
wait_event_freezable_timeout(balloon_thread_wq,
balloon_thread_cond(credit), timeout);
if (kthread_should_stop())
return 0;
mutex_lock(&balloon_mutex);
credit = current_credit();
if (credit > 0) {
if (balloon_is_inflated())
balloon_state = increase_reservation(credit);
else
balloon_state = reserve_additional_memory();
}
if (credit < 0) {
long n_pages;
n_pages = min(-credit, si_mem_available());
balloon_state = decrease_reservation(n_pages,
GFP_BALLOON);
if (balloon_state == BP_DONE && n_pages != -credit &&
n_pages < totalreserve_pages)
balloon_state = BP_EAGAIN;
}
update_schedule();
mutex_unlock(&balloon_mutex);
cond_resched();
}
}
/* 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;
wake_up(&balloon_thread_wq);
}
EXPORT_SYMBOL_GPL(balloon_set_new_target);
static int add_ballooned_pages(unsigned 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;
}
/**
* xen_alloc_ballooned_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 xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
{
unsigned 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);
xen_free_ballooned_pages(pgno, pages);
/*
* NB: xen_free_ballooned_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(xen_alloc_ballooned_pages);
/**
* xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
* @nr_pages: Number of pages
* @pages: pages to return
*/
void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
{
unsigned 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())
wake_up(&balloon_thread_wq);
mutex_unlock(&balloon_mutex);
}
EXPORT_SYMBOL(xen_free_ballooned_pages);
static void __init balloon_add_regions(void)
{
unsigned long start_pfn, pages;
unsigned long pfn, extra_pfn_end;
unsigned int i;
for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
pages = xen_extra_mem[i].n_pfns;
if (!pages)
continue;
start_pfn = xen_extra_mem[i].start_pfn;
/*
* 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++)
balloon_append(pfn_to_page(pfn));
balloon_stats.total_pages += extra_pfn_end - start_pfn;
}
}
static int __init balloon_init(void)
{
struct task_struct *task;
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_init("xen/balloon", balloon_table);
#endif
balloon_add_regions();
task = kthread_run(balloon_thread, NULL, "xen-balloon");
if (IS_ERR(task)) {
pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
return PTR_ERR(task);
}
/* Init the xen-balloon driver. */
xen_balloon_init();
return 0;
}
subsys_initcall(balloon_init);
static int __init balloon_wait_finish(void)
{
long credit, last_credit = 0;
unsigned long last_changed = 0;
if (!xen_domain())
return -ENODEV;
/* PV guests don't need to wait. */
if (xen_pv_domain() || !current_credit())
return 0;
pr_notice("Waiting for initial ballooning down having finished.\n");
while ((credit = current_credit()) < 0) {
if (credit != last_credit) {
last_changed = jiffies;
last_credit = credit;
}
if (balloon_state == BP_ECANCELED) {
pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
-credit);
if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout))
panic("Initial ballooning failed!\n");
}
schedule_timeout_interruptible(HZ / 10);
}
pr_notice("Initial ballooning down finished.\n");
return 0;
}
late_initcall_sync(balloon_wait_finish);
Codebase Browser
linux