/******************************************************************************
* balloon.c
*
* 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
*
* 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.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/bootmem.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/sysdev.h>
#include <asm/xen/hypervisor.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/tlb.h>
#include <xen/interface/memory.h>
#include <xen/xenbus.h>
#include <xen/features.h>
#include <xen/page.h>
#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
#define BALLOON_CLASS_NAME "xen_memory"
struct balloon_stats {
/* We aim for 'current allocation' == 'target allocation'. */
unsigned long current_pages;
unsigned long target_pages;
/* We may hit the hard limit in Xen. If we do then we remember it. */
unsigned long hard_limit;
/*
* Drivers may alter the memory reservation independently, but they
* must inform the balloon driver so we avoid hitting the hard limit.
*/
unsigned long driver_pages;
/* Number of pages in high- and low-memory balloons. */
unsigned long balloon_low;
unsigned long balloon_high;
};
static DEFINE_MUTEX(balloon_mutex);
static struct sys_device balloon_sysdev;
static int register_balloon(struct sys_device *sysdev);
/*
* Protects atomic reservation decrease/increase against concurrent increases.
* Also protects non-atomic updates of current_pages and driver_pages, and
* balloon lists.
*/
static DEFINE_SPINLOCK(balloon_lock);
static struct balloon_stats balloon_stats;
/* We increase/decrease in batches which fit in a page */
static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
/* VM /proc information for memory */
extern unsigned long totalram_pages;
#ifdef CONFIG_HIGHMEM
extern unsigned long totalhigh_pages;
#define inc_totalhigh_pages() (totalhigh_pages++)
#define dec_totalhigh_pages() (totalhigh_pages--)
#else
#define inc_totalhigh_pages() do {} while(0)
#define dec_totalhigh_pages() do {} while(0)
#endif
/* List of ballooned pages, threaded through the mem_map array. */
static LIST_HEAD(ballooned_pages);
/* Main work function, always executed in process context. */
static void balloon_process(struct work_struct *work);
static DECLARE_WORK(balloon_worker, balloon_process);
static struct timer_list balloon_timer;
/* 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)
static void scrub_page(struct page *page)
{
#ifdef CONFIG_XEN_SCRUB_PAGES
if (PageHighMem(page)) {
void *v = kmap(page);
clear_page(v);
kunmap(v);
} else {
void *v = page_address(page);
clear_page(v);
}
#endif
}
/* balloon_append: add the given page to the balloon. */
static void balloon_append(struct page *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++;
dec_totalhigh_pages();
} else {
list_add(&page->lru, &ballooned_pages);
balloon_stats.balloon_low++;
}
}
/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
static struct page *balloon_retrieve(void)
{
struct page *page;
if (list_empty(&ballooned_pages))
return NULL;
page = list_entry(ballooned_pages.next, struct page, lru);
list_del(&page->lru);
if (PageHighMem(page)) {
balloon_stats.balloon_high--;
inc_totalhigh_pages();
}
else
balloon_stats.balloon_low--;
return page;
}
static struct page *balloon_first_page(void)
{
if (list_empty(&ballooned_pages))
return NULL;
return list_entry(ballooned_pages.next, struct page, lru);
}
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 balloon_alarm(unsigned long unused)
{
schedule_work(&balloon_worker);
}
static unsigned long current_target(void)
{
unsigned long target = min(balloon_stats.target_pages, balloon_stats.hard_limit);
target = min(target,
balloon_stats.current_pages +
balloon_stats.balloon_low +
balloon_stats.balloon_high);
return target;
}
static int increase_reservation(unsigned long nr_pages)
{
unsigned long pfn, i, flags;
struct page *page;
long rc;
struct xen_memory_reservation reservation = {
.address_bits = 0,
.extent_order = 0,
.domid = DOMID_SELF
};
if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list);
spin_lock_irqsave(&balloon_lock, flags);
page = balloon_first_page();
for (i = 0; i < nr_pages; i++) {
BUG_ON(page == NULL);
frame_list[i] = page_to_pfn(page);;
page = balloon_next_page(page);
}
set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages;
rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
if (rc < nr_pages) {
if (rc > 0) {
int ret;
/* We hit the Xen hard limit: reprobe. */
reservation.nr_extents = rc;
ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
&reservation);
BUG_ON(ret != rc);
}
if (rc >= 0)
balloon_stats.hard_limit = (balloon_stats.current_pages + rc -
balloon_stats.driver_pages);
goto out;
}
for (i = 0; i < nr_pages; i++) {
page = balloon_retrieve();
BUG_ON(page == NULL);
pfn = page_to_pfn(page);
BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
phys_to_machine_mapping_valid(pfn));
set_phys_to_machine(pfn, frame_list[i]);
/* Link back into the page tables if not highmem. */
if (pfn < max_low_pfn) {
int ret;
ret = HYPERVISOR_update_va_mapping(
(unsigned long)__va(pfn << PAGE_SHIFT),
mfn_pte(frame_list[i], PAGE_KERNEL),
0);
BUG_ON(ret);
}
/* Relinquish the page back to the allocator. */
ClearPageReserved(page);
init_page_count(page);
__free_page(page);
}
balloon_stats.current_pages += nr_pages;
totalram_pages = balloon_stats.current_pages;
out:
spin_unlock_irqrestore(&balloon_lock, flags);
return 0;
}
static int decrease_reservation(unsigned long nr_pages)
{
unsigned long pfn, i, flags;
struct page *page;
int need_sleep = 0;
int ret;
struct xen_memory_reservation reservation = {
.address_bits = 0,
.extent_order = 0,
.domid = DOMID_SELF
};
if (nr_pages > ARRAY_SIZE(frame_list))
nr_pages = ARRAY_SIZE(frame_list);
for (i = 0; i < nr_pages; i++) {
if ((page = alloc_page(GFP_BALLOON)) == NULL) {
nr_pages = i;
need_sleep = 1;
break;
}
pfn = page_to_pfn(page);
frame_list[i] = pfn_to_mfn(pfn);
scrub_page(page);
}
/* Ensure that ballooned highmem pages don't have kmaps. */
kmap_flush_unused();
flush_tlb_all();
spin_lock_irqsave(&balloon_lock, flags);
/* No more mappings: invalidate P2M and add to balloon. */
for (i = 0; i < nr_pages; i++) {
pfn = mfn_to_pfn(frame_list[i]);
set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
balloon_append(pfn_to_page(pfn));
}
set_xen_guest_handle(reservation.extent_start, frame_list);
reservation.nr_extents = nr_pages;
ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
BUG_ON(ret != nr_pages);
balloon_stats.current_pages -= nr_pages;
totalram_pages = balloon_stats.current_pages;
spin_unlock_irqrestore(&balloon_lock, flags);
return need_sleep;
}
/*
* We avoid multiple worker processes conflicting via the balloon mutex.
* 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 void balloon_process(struct work_struct *work)
{
int need_sleep = 0;
long credit;
mutex_lock(&balloon_mutex);
do {
credit = current_target() - balloon_stats.current_pages;
if (credit > 0)
need_sleep = (increase_reservation(credit) != 0);
if (credit < 0)
need_sleep = (decrease_reservation(-credit) != 0);
#ifndef CONFIG_PREEMPT
if (need_resched())
schedule();
#endif
} while ((credit != 0) && !need_sleep);
/* Schedule more work if there is some still to be done. */
if (current_target() != balloon_stats.current_pages)
mod_timer(&balloon_timer, jiffies + HZ);
mutex_unlock(&balloon_mutex);
}
/* Resets the Xen limit, sets new target, and kicks off processing. */
static void balloon_set_new_target(unsigned long target)
{
/* No need for lock. Not read-modify-write updates. */
balloon_stats.hard_limit = ~0UL;
balloon_stats.target_pages = target;
schedule_work(&balloon_worker);
}
static struct xenbus_watch target_watch =
{
.node = "memory/target"
};
/* React to a change in the target key */
static void watch_target(struct xenbus_watch *watch,
const char **vec, unsigned int len)
{
unsigned long long new_target;
int err;
err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
if (err != 1) {
/* This is ok (for domain0 at least) - so just return */
return;
}
/* The given memory/target value is in KiB, so it needs converting to
* pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
*/
balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
}
static int balloon_init_watcher(struct notifier_block *notifier,
unsigned long event,
void *data)
{
int err;
err = register_xenbus_watch(&target_watch);
if (err)
printk(KERN_ERR "Failed to set balloon watcher\n");
return NOTIFY_DONE;
}
static struct notifier_block xenstore_notifier;
static int __init balloon_init(void)
{
unsigned long pfn;
struct page *page;
if (!xen_pv_domain())
return -ENODEV;
pr_info("xen_balloon: Initialising balloon driver.\n");
balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
totalram_pages = balloon_stats.current_pages;
balloon_stats.target_pages = balloon_stats.current_pages;
balloon_stats.balloon_low = 0;
balloon_stats.balloon_high = 0;
balloon_stats.driver_pages = 0UL;
balloon_stats.hard_limit = ~0UL;
init_timer(&balloon_timer);
balloon_timer.data = 0;
balloon_timer.function = balloon_alarm;
register_balloon(&balloon_sysdev);
/* Initialise the balloon with excess memory space. */
for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
page = pfn_to_page(pfn);
if (!PageReserved(page))
balloon_append(page);
}
target_watch.callback = watch_target;
xenstore_notifier.notifier_call = balloon_init_watcher;
register_xenstore_notifier(&xenstore_notifier);
return 0;
}
subsys_initcall(balloon_init);
static void balloon_exit(void)
{
/* XXX - release balloon here */
return;
}
module_exit(balloon_exit);
#define BALLOON_SHOW(name, format, args...) \
static ssize_t show_##name(struct sys_device *dev, \
struct sysdev_attribute *attr, \
char *buf) \
{ \
return sprintf(buf, format, ##args); \
} \
static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
BALLOON_SHOW(hard_limit_kb,
(balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n",
(balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0);
BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
char *buf)
{
return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
}
static ssize_t store_target_kb(struct sys_device *dev,
struct sysdev_attribute *attr,
const char *buf,
size_t count)
{
char *endchar;
unsigned long long target_bytes;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
target_bytes = memparse(buf, &endchar);
balloon_set_new_target(target_bytes >> PAGE_SHIFT);
return count;
}
static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
show_target_kb, store_target_kb);
static struct sysdev_attribute *balloon_attrs[] = {
&attr_target_kb,
};
static struct attribute *balloon_info_attrs[] = {
&attr_current_kb.attr,
&attr_low_kb.attr,
&attr_high_kb.attr,
&attr_hard_limit_kb.attr,
&attr_driver_kb.attr,
NULL
};
static struct attribute_group balloon_info_group = {
.name = "info",
.attrs = balloon_info_attrs,
};
static struct sysdev_class balloon_sysdev_class = {
.name = BALLOON_CLASS_NAME,
};
static int register_balloon(struct sys_device *sysdev)
{
int i, error;
error = sysdev_class_register(&balloon_sysdev_class);
if (error)
return error;
sysdev->id = 0;
sysdev->cls = &balloon_sysdev_class;
error = sysdev_register(sysdev);
if (error) {
sysdev_class_unregister(&balloon_sysdev_class);
return error;
}
for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
error = sysdev_create_file(sysdev, balloon_attrs[i]);
if (error)
goto fail;
}
error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
if (error)
goto fail;
return 0;
fail:
while (--i >= 0)
sysdev_remove_file(sysdev, balloon_attrs[i]);
sysdev_unregister(sysdev);
sysdev_class_unregister(&balloon_sysdev_class);
return error;
}
MODULE_LICENSE("GPL");
