Fixed MTP to work with TWRP

drivers/misc/vmw_balloon.c

@@ -0,0 +1,839 @@
+/*
+ * 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:	Xavier Deguillard <xdeguillard@vmware.com>
+ *			Philip Moltmann <moltmann@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("1.2.1.3-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 statistics */
+	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;
+
+/*
+ * 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 int 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 -1;
+
+	STATS_INC(b->stats.lock);
+
+	*hv_status = status = VMWARE_BALLOON_CMD(LOCK, pfn, dummy);
+	if (vmballoon_check_status(b, status))
+		return 0;
+
+	pr_debug("%s - ppn %lx, hv returns %ld\n", __func__, pfn, status);
+	STATS_INC(b->stats.lock_fail);
+	return 1;
+}
+
+/*
+ * 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;
+	int locked;
+	flags = can_sleep ? VMW_PAGE_ALLOC_CANSLEEP : VMW_PAGE_ALLOC_NOSLEEP;
+
+	do {
+		if (!can_sleep)
+			STATS_INC(b->stats.alloc);
+		else
+			STATS_INC(b->stats.sleep_alloc);
+
+		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 > 0) {
+			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 != 0);
+
+	/* 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);
+	}
+
+	/*
+	 * We are using a freezable workqueue so that balloon operations are
+	 * stopped while the system transitions to/from sleep/hibernation.
+	 */
+	queue_delayed_work(system_freezable_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;
+
+	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");
+		return -EIO;
+	}
+
+	if (!vmballoon_send_guest_id(&balloon)) {
+		pr_err("failed to send guest ID to the host\n");
+		return -EIO;
+	}
+
+	error = vmballoon_debugfs_init(&balloon);
+	if (error)
+		return error;
+
+	queue_delayed_work(system_freezable_wq, &balloon.dwork, 0);
+
+	return 0;
+}
+module_init(vmballoon_init);
+
+static void __exit vmballoon_exit(void)
+{
+	cancel_delayed_work_sync(&balloon.dwork);
+
+	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);