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/*
* VMware Balloon driver.
*
* Copyright (C) 2000-2010, VMware, Inc. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; version 2 of the License and no later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Maintained by: Dmitry Torokhov <dtor@vmware.com>
*/
/*
* This is VMware physical memory management driver for Linux. The driver
* acts like a "balloon" that can be inflated to reclaim physical pages by
* reserving them in the guest and invalidating them in the monitor,
* freeing up the underlying machine pages so they can be allocated to
* other guests. The balloon can also be deflated to allow the guest to
* use more physical memory. Higher level policies can control the sizes
* of balloons in VMs in order to manage physical memory resources.
*/
//#define DEBUG
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/workqueue.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <asm/hypervisor.h>
MODULE_AUTHOR("VMware, Inc.");
MODULE_DESCRIPTION("VMware Memory Control (Balloon) Driver");
MODULE_VERSION("1.2.1.2-k");
MODULE_ALIAS("dmi:*:svnVMware*:*");
MODULE_ALIAS("vmware_vmmemctl");
MODULE_LICENSE("GPL");
/*
* Various constants controlling rate of inflaint/deflating balloon,
* measured in pages.
*/
/*
* Rate of allocating memory when there is no memory pressure
* (driver performs non-sleeping allocations).
*/
#define VMW_BALLOON_NOSLEEP_ALLOC_MAX 16384U
/*
* Rates of memory allocaton when guest experiences memory pressure
* (driver performs sleeping allocations).
*/
#define VMW_BALLOON_RATE_ALLOC_MIN 512U
#define VMW_BALLOON_RATE_ALLOC_MAX 2048U
#define VMW_BALLOON_RATE_ALLOC_INC 16U
/*
* Rates for releasing pages while deflating balloon.
*/
#define VMW_BALLOON_RATE_FREE_MIN 512U
#define VMW_BALLOON_RATE_FREE_MAX 16384U
#define VMW_BALLOON_RATE_FREE_INC 16U
/*
* When guest is under memory pressure, use a reduced page allocation
* rate for next several cycles.
*/
#define VMW_BALLOON_SLOW_CYCLES 4
/*
* Use __GFP_HIGHMEM to allow pages from HIGHMEM zone. We don't
* allow wait (__GFP_WAIT) for NOSLEEP page allocations. Use
* __GFP_NOWARN, to suppress page allocation failure warnings.
*/
#define VMW_PAGE_ALLOC_NOSLEEP (__GFP_HIGHMEM|__GFP_NOWARN)
/*
* Use GFP_HIGHUSER when executing in a separate kernel thread
* context and allocation can sleep. This is less stressful to
* the guest memory system, since it allows the thread to block
* while memory is reclaimed, and won't take pages from emergency
* low-memory pools.
*/
#define VMW_PAGE_ALLOC_CANSLEEP (GFP_HIGHUSER)
/* Maximum number of page allocations without yielding processor */
#define VMW_BALLOON_YIELD_THRESHOLD 1024
/* Maximum number of refused pages we accumulate during inflation cycle */
#define VMW_BALLOON_MAX_REFUSED 16
/*
* Hypervisor communication port definitions.
*/
#define VMW_BALLOON_HV_PORT 0x5670
#define VMW_BALLOON_HV_MAGIC 0x456c6d6f
#define VMW_BALLOON_PROTOCOL_VERSION 2
#define VMW_BALLOON_GUEST_ID 1 /* Linux */
#define VMW_BALLOON_CMD_START 0
#define VMW_BALLOON_CMD_GET_TARGET 1
#define VMW_BALLOON_CMD_LOCK 2
#define VMW_BALLOON_CMD_UNLOCK 3
#define VMW_BALLOON_CMD_GUEST_ID 4
/* error codes */
#define VMW_BALLOON_SUCCESS 0
#define VMW_BALLOON_FAILURE -1
#define VMW_BALLOON_ERROR_CMD_INVALID 1
#define VMW_BALLOON_ERROR_PPN_INVALID 2
#define VMW_BALLOON_ERROR_PPN_LOCKED 3
#define VMW_BALLOON_ERROR_PPN_UNLOCKED 4
#define VMW_BALLOON_ERROR_PPN_PINNED 5
#define VMW_BALLOON_ERROR_PPN_NOTNEEDED 6
#define VMW_BALLOON_ERROR_RESET 7
#define VMW_BALLOON_ERROR_BUSY 8
#define VMWARE_BALLOON_CMD(cmd, data, result) \
({ \
unsigned long __stat, __dummy1, __dummy2; \
__asm__ __volatile__ ("inl (%%dx)" : \
"=a"(__stat), \
"=c"(__dummy1), \
"=d"(__dummy2), \
"=b"(result) : \
"0"(VMW_BALLOON_HV_MAGIC), \
"1"(VMW_BALLOON_CMD_##cmd), \
"2"(VMW_BALLOON_HV_PORT), \
"3"(data) : \
"memory"); \
result &= -1UL; \
__stat & -1UL; \
})
#ifdef CONFIG_DEBUG_FS
struct vmballoon_stats {
unsigned int timer;
/* allocation statustics */
unsigned int alloc;
unsigned int alloc_fail;
unsigned int sleep_alloc;
unsigned int sleep_alloc_fail;
unsigned int refused_alloc;
unsigned int refused_free;
unsigned int free;
/* monitor operations */
unsigned int lock;
unsigned int lock_fail;
unsigned int unlock;
unsigned int unlock_fail;
unsigned int target;
unsigned int target_fail;
unsigned int start;
unsigned int start_fail;
unsigned int guest_type;
unsigned int guest_type_fail;
};
#define STATS_INC(stat) (stat)++
#else
#define STATS_INC(stat)
#endif
struct vmballoon {
/* list of reserved physical pages */
struct list_head pages;
/* transient list of non-balloonable pages */
struct list_head refused_pages;
unsigned int n_refused_pages;
/* balloon size in pages */
unsigned int size;
unsigned int target;
/* reset flag */
bool reset_required;
/* adjustment rates (pages per second) */
unsigned int rate_alloc;
unsigned int rate_free;
/* slowdown page allocations for next few cycles */
unsigned int slow_allocation_cycles;
#ifdef CONFIG_DEBUG_FS
/* statistics */
struct vmballoon_stats stats;
/* debugfs file exporting statistics */
struct dentry *dbg_entry;
#endif
struct sysinfo sysinfo;
struct delayed_work dwork;
};
static struct vmballoon balloon;
static struct workqueue_struct *vmballoon_wq;
/*
* Send "start" command to the host, communicating supported version
* of the protocol.
*/
static bool vmballoon_send_start(struct vmballoon *b)
{
unsigned long status, dummy;
STATS_INC(b->stats.start);
status = VMWARE_BALLOON_CMD(START, VMW_BALLOON_PROTOCOL_VERSION, dummy);
if (status == VMW_BALLOON_SUCCESS)
return true;
pr_debug("%s - failed, hv returns %ld\n", __func__, status);
STATS_INC(b->stats.start_fail);
return false;
}
static bool vmballoon_check_status(struct vmballoon *b, unsigned long status)
{
switch (status) {
case VMW_BALLOON_SUCCESS:
return true;
case VMW_BALLOON_ERROR_RESET:
b->reset_required = true;
/* fall through */
default:
return false;
}
}
/*
* Communicate guest type to the host so that it can adjust ballooning
* algorithm to the one most appropriate for the guest. This command
* is normally issued after sending "start" command and is part of
* standard reset sequence.
*/
static bool vmballoon_send_guest_id(struct vmballoon *b)
{
unsigned long status, dummy;
status = VMWARE_BALLOON_CMD(GUEST_ID, VMW_BALLOON_GUEST_ID, dummy);
STATS_INC(b->stats.guest_type);
if (vmballoon_check_status(b, status))
return true;
pr_debug("%s - failed, hv returns %ld\n", __func__, status);
STATS_INC(b->stats.guest_type_fail);
return false;
}
/*
* Retrieve desired balloon size from the host.
*/
static bool vmballoon_send_get_target(struct vmballoon *b, u32 *new_target)
{
unsigned long status;
unsigned long target;
unsigned long limit;
u32 limit32;
/*
* si_meminfo() is cheap. Moreover, we want to provide dynamic
* max balloon size later. So let us call si_meminfo() every
* iteration.
*/
si_meminfo(&b->sysinfo);
limit = b->sysinfo.totalram;
/* Ensure limit fits in 32-bits */
limit32 = (u32)limit;
if (limit != limit32)
return false;
/* update stats */
STATS_INC(b->stats.target);
status = VMWARE_BALLOON_CMD(GET_TARGET, limit, target);
if (vmballoon_check_status(b, status)) {
*new_target = target;
return true;
}
pr_debug("%s - failed, hv returns %ld\n", __func__, status);
STATS_INC(b->stats.target_fail);
return false;
}
/*
* Notify the host about allocated page so that host can use it without
* fear that guest will need it. Host may reject some pages, we need to
* check the return value and maybe submit a different page.
*/
static bool vmballoon_send_lock_page(struct vmballoon *b, unsigned long pfn,
unsigned int *hv_status)
{
unsigned long status, dummy;
u32 pfn32;
pfn32 = (u32)pfn;
if (pfn32 != pfn)
return false;
STATS_INC(b->stats.lock);
*hv_status = status = VMWARE_BALLOON_CMD(LOCK, pfn, dummy);
if (vmballoon_check_status(b, status))
return true;
pr_debug("%s - ppn %lx, hv returns %ld\n", __func__, pfn, status);
STATS_INC(b->stats.lock_fail);
return false;
}
/*
* Notify the host that guest intends to release given page back into
* the pool of available (to the guest) pages.
*/
static bool vmballoon_send_unlock_page(struct vmballoon *b, unsigned long pfn)
{
unsigned long status, dummy;
u32 pfn32;
pfn32 = (u32)pfn;
if (pfn32 != pfn)
return false;
STATS_INC(b->stats.unlock);
status = VMWARE_BALLOON_CMD(UNLOCK, pfn, dummy);
if (vmballoon_check_status(b, status))
return true;
pr_debug("%s - ppn %lx, hv returns %ld\n", __func__, pfn, status);
STATS_INC(b->stats.unlock_fail);
return false;
}
/*
* Quickly release all pages allocated for the balloon. This function is
* called when host decides to "reset" balloon for one reason or another.
* Unlike normal "deflate" we do not (shall not) notify host of the pages
* being released.
*/
static void vmballoon_pop(struct vmballoon *b)
{
struct page *page, *next;
unsigned int count = 0;
list_for_each_entry_safe(page, next, &b->pages, lru) {
list_del(&page->lru);
__free_page(page);
STATS_INC(b->stats.free);
b->size--;
if (++count >= b->rate_free) {
count = 0;
cond_resched();
}
}
}
/*
* Perform standard reset sequence by popping the balloon (in case it
* is not empty) and then restarting protocol. This operation normally
* happens when host responds with VMW_BALLOON_ERROR_RESET to a command.
*/
static void vmballoon_reset(struct vmballoon *b)
{
/* free all pages, skipping monitor unlock */
vmballoon_pop(b);
if (vmballoon_send_start(b)) {
b->reset_required = false;
if (!vmballoon_send_guest_id(b))
pr_err("failed to send guest ID to the host\n");
}
}
/*
* Allocate (or reserve) a page for the balloon and notify the host. If host
* refuses the page put it on "refuse" list and allocate another one until host
* is satisfied. "Refused" pages are released at the end of inflation cycle
* (when we allocate b->rate_alloc pages).
*/
static int vmballoon_reserve_page(struct vmballoon *b, bool can_sleep)
{
struct page *page;
gfp_t flags;
unsigned int hv_status;
bool locked = false;
do {
if (!can_sleep)
STATS_INC(b->stats.alloc);
else
STATS_INC(b->stats.sleep_alloc);
flags = can_sleep ? VMW_PAGE_ALLOC_CANSLEEP : VMW_PAGE_ALLOC_NOSLEEP;
page = alloc_page(flags);
if (!page) {
if (!can_sleep)
STATS_INC(b->stats.alloc_fail);
else
STATS_INC(b->stats.sleep_alloc_fail);
return -ENOMEM;
}
/* inform monitor */
locked = vmballoon_send_lock_page(b, page_to_pfn(page), &hv_status);
if (!locked) {
STATS_INC(b->stats.refused_alloc);
if (hv_status == VMW_BALLOON_ERROR_RESET ||
hv_status == VMW_BALLOON_ERROR_PPN_NOTNEEDED) {
__free_page(page);
return -EIO;
}
/*
* Place page on the list of non-balloonable pages
* and retry allocation, unless we already accumulated
* too many of them, in which case take a breather.
*/
list_add(&page->lru, &b->refused_pages);
if (++b->n_refused_pages >= VMW_BALLOON_MAX_REFUSED)
return -EIO;
}
} while (!locked);
/* track allocated page */
list_add(&page->lru, &b->pages);
/* update balloon size */
b->size++;
return 0;
}
/*
* Release the page allocated for the balloon. Note that we first notify
* the host so it can make sure the page will be available for the guest
* to use, if needed.
*/
static int vmballoon_release_page(struct vmballoon *b, struct page *page)
{
if (!vmballoon_send_unlock_page(b, page_to_pfn(page)))
return -EIO;
list_del(&page->lru);
/* deallocate page */
__free_page(page);
STATS_INC(b->stats.free);
/* update balloon size */
b->size--;
return 0;
}
/*
* Release pages that were allocated while attempting to inflate the
* balloon but were refused by the host for one reason or another.
*/
static void vmballoon_release_refused_pages(struct vmballoon *b)
{
struct page *page, *next;
list_for_each_entry_safe(page, next, &b->refused_pages, lru) {
list_del(&page->lru);
__free_page(page);
STATS_INC(b->stats.refused_free);
}
b->n_refused_pages = 0;
}
/*
* Inflate the balloon towards its target size. Note that we try to limit
* the rate of allocation to make sure we are not choking the rest of the
* system.
*/
static void vmballoon_inflate(struct vmballoon *b)
{
unsigned int goal;
unsigned int rate;
unsigned int i;
unsigned int allocations = 0;
int error = 0;
bool alloc_can_sleep = false;
pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
/*
* First try NOSLEEP page allocations to inflate balloon.
*
* If we do not throttle nosleep allocations, we can drain all
* free pages in the guest quickly (if the balloon target is high).
* As a side-effect, draining free pages helps to inform (force)
* the guest to start swapping if balloon target is not met yet,
* which is a desired behavior. However, balloon driver can consume
* all available CPU cycles if too many pages are allocated in a
* second. Therefore, we throttle nosleep allocations even when
* the guest is not under memory pressure. OTOH, if we have already
* predicted that the guest is under memory pressure, then we
* slowdown page allocations considerably.
*/
goal = b->target - b->size;
/*
* Start with no sleep allocation rate which may be higher
* than sleeping allocation rate.
*/
rate = b->slow_allocation_cycles ?
b->rate_alloc : VMW_BALLOON_NOSLEEP_ALLOC_MAX;
pr_debug("%s - goal: %d, no-sleep rate: %d, sleep rate: %d\n",
__func__, goal, rate, b->rate_alloc);
for (i = 0; i < goal; i++) {
error = vmballoon_reserve_page(b, alloc_can_sleep);
if (error) {
if (error != -ENOMEM) {
/*
* Not a page allocation failure, stop this
* cycle. Maybe we'll get new target from
* the host soon.
*/
break;
}
if (alloc_can_sleep) {
/*
* CANSLEEP page allocation failed, so guest
* is under severe memory pressure. Quickly
* decrease allocation rate.
*/
b->rate_alloc = max(b->rate_alloc / 2,
VMW_BALLOON_RATE_ALLOC_MIN);
break;
}
/*
* NOSLEEP page allocation failed, so the guest is
* under memory pressure. Let us slow down page
* allocations for next few cycles so that the guest
* gets out of memory pressure. Also, if we already
* allocated b->rate_alloc pages, let's pause,
* otherwise switch to sleeping allocations.
*/
b->slow_allocation_cycles = VMW_BALLOON_SLOW_CYCLES;
if (i >= b->rate_alloc)
break;
alloc_can_sleep = true;
/* Lower rate for sleeping allocations. */
rate = b->rate_alloc;
}
if (++allocations > VMW_BALLOON_YIELD_THRESHOLD) {
cond_resched();
allocations = 0;
}
if (i >= rate) {
/* We allocated enough pages, let's take a break. */
break;
}
}
/*
* We reached our goal without failures so try increasing
* allocation rate.
*/
if (error == 0 && i >= b->rate_alloc) {
unsigned int mult = i / b->rate_alloc;
b->rate_alloc =
min(b->rate_alloc + mult * VMW_BALLOON_RATE_ALLOC_INC,
VMW_BALLOON_RATE_ALLOC_MAX);
}
vmballoon_release_refused_pages(b);
}
/*
* Decrease the size of the balloon allowing guest to use more memory.
*/
static void vmballoon_deflate(struct vmballoon *b)
{
struct page *page, *next;
unsigned int i = 0;
unsigned int goal;
int error;
pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
/* limit deallocation rate */
goal = min(b->size - b->target, b->rate_free);
pr_debug("%s - goal: %d, rate: %d\n", __func__, goal, b->rate_free);
/* free pages to reach target */
list_for_each_entry_safe(page, next, &b->pages, lru) {
error = vmballoon_release_page(b, page);
if (error) {
/* quickly decrease rate in case of error */
b->rate_free = max(b->rate_free / 2,
VMW_BALLOON_RATE_FREE_MIN);
return;
}
if (++i >= goal)
break;
}
/* slowly increase rate if there were no errors */
b->rate_free = min(b->rate_free + VMW_BALLOON_RATE_FREE_INC,
VMW_BALLOON_RATE_FREE_MAX);
}
/*
* Balloon work function: reset protocol, if needed, get the new size and
* adjust balloon as needed. Repeat in 1 sec.
*/
static void vmballoon_work(struct work_struct *work)
{
struct delayed_work *dwork = to_delayed_work(work);
struct vmballoon *b = container_of(dwork, struct vmballoon, dwork);
unsigned int target;
STATS_INC(b->stats.timer);
if (b->reset_required)
vmballoon_reset(b);
if (b->slow_allocation_cycles > 0)
b->slow_allocation_cycles--;
if (vmballoon_send_get_target(b, &target)) {
/* update target, adjust size */
b->target = target;
if (b->size < target)
vmballoon_inflate(b);
else if (b->size > target)
vmballoon_deflate(b);
}
queue_delayed_work(vmballoon_wq, dwork, round_jiffies_relative(HZ));
}
/*
* DEBUGFS Interface
*/
#ifdef CONFIG_DEBUG_FS
static int vmballoon_debug_show(struct seq_file *f, void *offset)
{
struct vmballoon *b = f->private;
struct vmballoon_stats *stats = &b->stats;
/* format size info */
seq_printf(f,
"target: %8d pages\n"
"current: %8d pages\n",
b->target, b->size);
/* format rate info */
seq_printf(f,
"rateNoSleepAlloc: %8d pages/sec\n"
"rateSleepAlloc: %8d pages/sec\n"
"rateFree: %8d pages/sec\n",
VMW_BALLOON_NOSLEEP_ALLOC_MAX,
b->rate_alloc, b->rate_free);
seq_printf(f,
"\n"
"timer: %8u\n"
"start: %8u (%4u failed)\n"
"guestType: %8u (%4u failed)\n"
"lock: %8u (%4u failed)\n"
"unlock: %8u (%4u failed)\n"
"target: %8u (%4u failed)\n"
"primNoSleepAlloc: %8u (%4u failed)\n"
"primCanSleepAlloc: %8u (%4u failed)\n"
"primFree: %8u\n"
"errAlloc: %8u\n"
"errFree: %8u\n",
stats->timer,
stats->start, stats->start_fail,
stats->guest_type, stats->guest_type_fail,
stats->lock, stats->lock_fail,
stats->unlock, stats->unlock_fail,
stats->target, stats->target_fail,
stats->alloc, stats->alloc_fail,
stats->sleep_alloc, stats->sleep_alloc_fail,
stats->free,
stats->refused_alloc, stats->refused_free);
return 0;
}
static int vmballoon_debug_open(struct inode *inode, struct file *file)
{
return single_open(file, vmballoon_debug_show, inode->i_private);
}
static const struct file_operations vmballoon_debug_fops = {
.owner = THIS_MODULE,
.open = vmballoon_debug_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static int __init vmballoon_debugfs_init(struct vmballoon *b)
{
int error;
b->dbg_entry = debugfs_create_file("vmmemctl", S_IRUGO, NULL, b,
&vmballoon_debug_fops);
if (IS_ERR(b->dbg_entry)) {
error = PTR_ERR(b->dbg_entry);
pr_err("failed to create debugfs entry, error: %d\n", error);
return error;
}
return 0;
}
static void __exit vmballoon_debugfs_exit(struct vmballoon *b)
{
debugfs_remove(b->dbg_entry);
}
#else
static inline int vmballoon_debugfs_init(struct vmballoon *b)
{
return 0;
}
static inline void vmballoon_debugfs_exit(struct vmballoon *b)
{
}
#endif /* CONFIG_DEBUG_FS */
static int __init vmballoon_init(void)
{
int error;
/*
* Check if we are running on VMware's hypervisor and bail out
* if we are not.
*/
if (x86_hyper != &x86_hyper_vmware)
return -ENODEV;
vmballoon_wq = create_freezable_workqueue("vmmemctl");
if (!vmballoon_wq) {
pr_err("failed to create workqueue\n");
return -ENOMEM;
}
INIT_LIST_HEAD(&balloon.pages);
INIT_LIST_HEAD(&balloon.refused_pages);
/* initialize rates */
balloon.rate_alloc = VMW_BALLOON_RATE_ALLOC_MAX;
balloon.rate_free = VMW_BALLOON_RATE_FREE_MAX;
INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);
/*
* Start balloon.
*/
if (!vmballoon_send_start(&balloon)) {
pr_err("failed to send start command to the host\n");
error = -EIO;
goto fail;
}
if (!vmballoon_send_guest_id(&balloon)) {
pr_err("failed to send guest ID to the host\n");
error = -EIO;
goto fail;
}
error = vmballoon_debugfs_init(&balloon);
if (error)
goto fail;
queue_delayed_work(vmballoon_wq, &balloon.dwork, 0);
return 0;
fail:
destroy_workqueue(vmballoon_wq);
return error;
}
module_init(vmballoon_init);
static void __exit vmballoon_exit(void)
{
cancel_delayed_work_sync(&balloon.dwork);
destroy_workqueue(vmballoon_wq);
vmballoon_debugfs_exit(&balloon);
/*
* Deallocate all reserved memory, and reset connection with monitor.
* Reset connection before deallocating memory to avoid potential for
* additional spurious resets from guest touching deallocated pages.
*/
vmballoon_send_start(&balloon);
vmballoon_pop(&balloon);
}
module_exit(vmballoon_exit);