Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1236 insertions, 0 deletions

diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
new file mode 100644
index 000000000..2543ef1ec
--- /dev/null
+++ b/drivers/misc/vmw_balloon.c
@@ -0,0 +1,1236 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * VMware Balloon driver.
+ *
+ * Copyright (C) 2000-2018, VMware, Inc. All Rights Reserved.
+ *
+ * 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/vmalloc.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/workqueue.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/vmw_vmci_defs.h>
+#include <linux/vmw_vmci_api.h>
+#include <asm/hypervisor.h>
+
+MODULE_AUTHOR("VMware, Inc.");
+MODULE_DESCRIPTION("VMware Memory Control (Balloon) Driver");
+MODULE_VERSION("1.5.0.0-k");
+MODULE_ALIAS("dmi:*:svnVMware*:*");
+MODULE_ALIAS("vmware_vmmemctl");
+MODULE_LICENSE("GPL");
+
+/*
+ * Use __GFP_HIGHMEM to allow pages from HIGHMEM zone. We don't
+ * allow wait (__GFP_RECLAIM) 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 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_GUEST_ID		1	/* Linux */
+
+enum vmwballoon_capabilities {
+	/*
+	 * Bit 0 is reserved and not associated to any capability.
+	 */
+	VMW_BALLOON_BASIC_CMDS			= (1 << 1),
+	VMW_BALLOON_BATCHED_CMDS		= (1 << 2),
+	VMW_BALLOON_BATCHED_2M_CMDS		= (1 << 3),
+	VMW_BALLOON_SIGNALLED_WAKEUP_CMD	= (1 << 4),
+};
+
+#define VMW_BALLOON_CAPABILITIES	(VMW_BALLOON_BASIC_CMDS \
+					| VMW_BALLOON_BATCHED_CMDS \
+					| VMW_BALLOON_BATCHED_2M_CMDS \
+					| VMW_BALLOON_SIGNALLED_WAKEUP_CMD)
+
+#define VMW_BALLOON_2M_SHIFT		(9)
+#define VMW_BALLOON_NUM_PAGE_SIZES	(2)
+
+/*
+ * Backdoor commands availability:
+ *
+ * START, GET_TARGET and GUEST_ID are always available,
+ *
+ * VMW_BALLOON_BASIC_CMDS:
+ *	LOCK and UNLOCK commands,
+ * VMW_BALLOON_BATCHED_CMDS:
+ *	BATCHED_LOCK and BATCHED_UNLOCK commands.
+ * VMW BALLOON_BATCHED_2M_CMDS:
+ *	BATCHED_2M_LOCK and BATCHED_2M_UNLOCK commands,
+ * VMW VMW_BALLOON_SIGNALLED_WAKEUP_CMD:
+ *	VMW_BALLOON_CMD_VMCI_DOORBELL_SET command.
+ */
+#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
+#define VMW_BALLOON_CMD_BATCHED_LOCK		6
+#define VMW_BALLOON_CMD_BATCHED_UNLOCK		7
+#define VMW_BALLOON_CMD_BATCHED_2M_LOCK		8
+#define VMW_BALLOON_CMD_BATCHED_2M_UNLOCK	9
+#define VMW_BALLOON_CMD_VMCI_DOORBELL_SET	10
+
+
+/* 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 VMW_BALLOON_SUCCESS_WITH_CAPABILITIES	(0x03000000)
+
+/* Batch page description */
+
+/*
+ * Layout of a page in the batch page:
+ *
+ * +-------------+----------+--------+
+ * |             |          |        |
+ * | Page number | Reserved | Status |
+ * |             |          |        |
+ * +-------------+----------+--------+
+ * 64  PAGE_SHIFT          6         0
+ *
+ * The reserved field should be set to 0.
+ */
+#define VMW_BALLOON_BATCH_MAX_PAGES	(PAGE_SIZE / sizeof(u64))
+#define VMW_BALLOON_BATCH_STATUS_MASK	((1UL << 5) - 1)
+#define VMW_BALLOON_BATCH_PAGE_MASK	(~((1UL << PAGE_SHIFT) - 1))
+
+struct vmballoon_batch_page {
+	u64 pages[VMW_BALLOON_BATCH_MAX_PAGES];
+};
+
+static u64 vmballoon_batch_get_pa(struct vmballoon_batch_page *batch, int idx)
+{
+	return batch->pages[idx] & VMW_BALLOON_BATCH_PAGE_MASK;
+}
+
+static int vmballoon_batch_get_status(struct vmballoon_batch_page *batch,
+				int idx)
+{
+	return (int)(batch->pages[idx] & VMW_BALLOON_BATCH_STATUS_MASK);
+}
+
+static void vmballoon_batch_set_pa(struct vmballoon_batch_page *batch, int idx,
+				u64 pa)
+{
+	batch->pages[idx] = pa;
+}
+
+
+#define VMWARE_BALLOON_CMD(cmd, arg1, arg2, result)		\
+({								\
+	unsigned long __status, __dummy1, __dummy2, __dummy3;	\
+	__asm__ __volatile__ ("inl %%dx" :			\
+		"=a"(__status),					\
+		"=c"(__dummy1),					\
+		"=d"(__dummy2),					\
+		"=b"(result),					\
+		"=S" (__dummy3) :				\
+		"0"(VMW_BALLOON_HV_MAGIC),			\
+		"1"(VMW_BALLOON_CMD_##cmd),			\
+		"2"(VMW_BALLOON_HV_PORT),			\
+		"3"(arg1),					\
+		"4" (arg2) :					\
+		"memory");					\
+	if (VMW_BALLOON_CMD_##cmd == VMW_BALLOON_CMD_START)	\
+		result = __dummy1;				\
+	result &= -1UL;						\
+	__status & -1UL;					\
+})
+
+#ifdef CONFIG_DEBUG_FS
+struct vmballoon_stats {
+	unsigned int timer;
+	unsigned int doorbell;
+
+	/* allocation statistics */
+	unsigned int alloc[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int alloc_fail[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int sleep_alloc;
+	unsigned int sleep_alloc_fail;
+	unsigned int refused_alloc[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int refused_free[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int free[VMW_BALLOON_NUM_PAGE_SIZES];
+
+	/* monitor operations */
+	unsigned int lock[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int lock_fail[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int unlock[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int unlock_fail[VMW_BALLOON_NUM_PAGE_SIZES];
+	unsigned int target;
+	unsigned int target_fail;
+	unsigned int start;
+	unsigned int start_fail;
+	unsigned int guest_type;
+	unsigned int guest_type_fail;
+	unsigned int doorbell_set;
+	unsigned int doorbell_unset;
+};
+
+#define STATS_INC(stat) (stat)++
+#else
+#define STATS_INC(stat)
+#endif
+
+struct vmballoon;
+
+struct vmballoon_ops {
+	void (*add_page)(struct vmballoon *b, int idx, struct page *p);
+	int (*lock)(struct vmballoon *b, unsigned int num_pages,
+			bool is_2m_pages, unsigned int *target);
+	int (*unlock)(struct vmballoon *b, unsigned int num_pages,
+			bool is_2m_pages, unsigned int *target);
+};
+
+struct vmballoon_page_size {
+	/* 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;
+};
+
+struct vmballoon {
+	struct vmballoon_page_size page_sizes[VMW_BALLOON_NUM_PAGE_SIZES];
+
+	/* supported page sizes. 1 == 4k pages only, 2 == 4k and 2m pages */
+	unsigned supported_page_sizes;
+
+	/* balloon size in pages */
+	unsigned int size;
+	unsigned int target;
+
+	/* reset flag */
+	bool reset_required;
+
+	unsigned long capabilities;
+
+	struct vmballoon_batch_page *batch_page;
+	unsigned int batch_max_pages;
+	struct page *page;
+
+	const struct vmballoon_ops *ops;
+
+#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;
+
+	struct vmci_handle vmci_doorbell;
+};
+
+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 req_caps)
+{
+	unsigned long status, capabilities, dummy = 0;
+	bool success;
+
+	STATS_INC(b->stats.start);
+
+	status = VMWARE_BALLOON_CMD(START, req_caps, dummy, capabilities);
+
+	switch (status) {
+	case VMW_BALLOON_SUCCESS_WITH_CAPABILITIES:
+		b->capabilities = capabilities;
+		success = true;
+		break;
+	case VMW_BALLOON_SUCCESS:
+		b->capabilities = VMW_BALLOON_BASIC_CMDS;
+		success = true;
+		break;
+	default:
+		success = false;
+	}
+
+	/*
+	 * 2MB pages are only supported with batching. If batching is for some
+	 * reason disabled, do not use 2MB pages, since otherwise the legacy
+	 * mechanism is used with 2MB pages, causing a failure.
+	 */
+	if ((b->capabilities & VMW_BALLOON_BATCHED_2M_CMDS) &&
+	    (b->capabilities & VMW_BALLOON_BATCHED_CMDS))
+		b->supported_page_sizes = 2;
+	else
+		b->supported_page_sizes = 1;
+
+	if (!success) {
+		pr_debug("%s - failed, hv returns %ld\n", __func__, status);
+		STATS_INC(b->stats.start_fail);
+	}
+	return success;
+}
+
+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 = 0;
+
+	status = VMWARE_BALLOON_CMD(GUEST_ID, VMW_BALLOON_GUEST_ID, dummy,
+				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;
+}
+
+static u16 vmballoon_page_size(bool is_2m_page)
+{
+	if (is_2m_page)
+		return 1 << VMW_BALLOON_2M_SHIFT;
+
+	return 1;
+}
+
+/*
+ * 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;
+	unsigned long dummy = 0;
+	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, dummy, 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 int *target)
+{
+	unsigned long status, dummy = 0;
+	u32 pfn32;
+
+	pfn32 = (u32)pfn;
+	if (pfn32 != pfn)
+		return -EINVAL;
+
+	STATS_INC(b->stats.lock[false]);
+
+	*hv_status = status = VMWARE_BALLOON_CMD(LOCK, pfn, dummy, *target);
+	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[false]);
+	return -EIO;
+}
+
+static int vmballoon_send_batched_lock(struct vmballoon *b,
+		unsigned int num_pages, bool is_2m_pages, unsigned int *target)
+{
+	unsigned long status;
+	unsigned long pfn = PHYS_PFN(virt_to_phys(b->batch_page));
+
+	STATS_INC(b->stats.lock[is_2m_pages]);
+
+	if (is_2m_pages)
+		status = VMWARE_BALLOON_CMD(BATCHED_2M_LOCK, pfn, num_pages,
+				*target);
+	else
+		status = VMWARE_BALLOON_CMD(BATCHED_LOCK, pfn, num_pages,
+				*target);
+
+	if (vmballoon_check_status(b, status))
+		return 0;
+
+	pr_debug("%s - batch ppn %lx, hv returns %ld\n", __func__, pfn, status);
+	STATS_INC(b->stats.lock_fail[is_2m_pages]);
+	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 int *target)
+{
+	unsigned long status, dummy = 0;
+	u32 pfn32;
+
+	pfn32 = (u32)pfn;
+	if (pfn32 != pfn)
+		return false;
+
+	STATS_INC(b->stats.unlock[false]);
+
+	status = VMWARE_BALLOON_CMD(UNLOCK, pfn, dummy, *target);
+	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[false]);
+	return false;
+}
+
+static bool vmballoon_send_batched_unlock(struct vmballoon *b,
+		unsigned int num_pages, bool is_2m_pages, unsigned int *target)
+{
+	unsigned long status;
+	unsigned long pfn = PHYS_PFN(virt_to_phys(b->batch_page));
+
+	STATS_INC(b->stats.unlock[is_2m_pages]);
+
+	if (is_2m_pages)
+		status = VMWARE_BALLOON_CMD(BATCHED_2M_UNLOCK, pfn, num_pages,
+				*target);
+	else
+		status = VMWARE_BALLOON_CMD(BATCHED_UNLOCK, pfn, num_pages,
+				*target);
+
+	if (vmballoon_check_status(b, status))
+		return true;
+
+	pr_debug("%s - batch ppn %lx, hv returns %ld\n", __func__, pfn, status);
+	STATS_INC(b->stats.unlock_fail[is_2m_pages]);
+	return false;
+}
+
+static struct page *vmballoon_alloc_page(gfp_t flags, bool is_2m_page)
+{
+	if (is_2m_page)
+		return alloc_pages(flags, VMW_BALLOON_2M_SHIFT);
+
+	return alloc_page(flags);
+}
+
+static void vmballoon_free_page(struct page *page, bool is_2m_page)
+{
+	if (is_2m_page)
+		__free_pages(page, VMW_BALLOON_2M_SHIFT);
+	else
+		__free_page(page);
+}
+
+/*
+ * 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 is_2m_pages;
+
+	for (is_2m_pages = 0; is_2m_pages < VMW_BALLOON_NUM_PAGE_SIZES;
+			is_2m_pages++) {
+		struct vmballoon_page_size *page_size =
+				&b->page_sizes[is_2m_pages];
+		u16 size_per_page = vmballoon_page_size(is_2m_pages);
+
+		list_for_each_entry_safe(page, next, &page_size->pages, lru) {
+			list_del(&page->lru);
+			vmballoon_free_page(page, is_2m_pages);
+			STATS_INC(b->stats.free[is_2m_pages]);
+			b->size -= size_per_page;
+			cond_resched();
+		}
+	}
+
+	/* Clearing the batch_page unconditionally has no adverse effect */
+	free_page((unsigned long)b->batch_page);
+	b->batch_page = NULL;
+}
+
+/*
+ * Notify the host of a ballooned page. If host rejects the page put it on the
+ * refuse list, those refused page are then released at the end of the
+ * inflation cycle.
+ */
+static int vmballoon_lock_page(struct vmballoon *b, unsigned int num_pages,
+				bool is_2m_pages, unsigned int *target)
+{
+	int locked, hv_status;
+	struct page *page = b->page;
+	struct vmballoon_page_size *page_size = &b->page_sizes[false];
+
+	/* is_2m_pages can never happen as 2m pages support implies batching */
+
+	locked = vmballoon_send_lock_page(b, page_to_pfn(page), &hv_status,
+								target);
+	if (locked) {
+		STATS_INC(b->stats.refused_alloc[false]);
+
+		if (locked == -EIO &&
+		    (hv_status == VMW_BALLOON_ERROR_RESET ||
+		     hv_status == VMW_BALLOON_ERROR_PPN_NOTNEEDED)) {
+			vmballoon_free_page(page, false);
+			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.
+		 */
+		if (page_size->n_refused_pages < VMW_BALLOON_MAX_REFUSED) {
+			page_size->n_refused_pages++;
+			list_add(&page->lru, &page_size->refused_pages);
+		} else {
+			vmballoon_free_page(page, false);
+		}
+		return locked;
+	}
+
+	/* track allocated page */
+	list_add(&page->lru, &page_size->pages);
+
+	/* update balloon size */
+	b->size++;
+
+	return 0;
+}
+
+static int vmballoon_lock_batched_page(struct vmballoon *b,
+		unsigned int num_pages, bool is_2m_pages, unsigned int *target)
+{
+	int locked, i;
+	u16 size_per_page = vmballoon_page_size(is_2m_pages);
+
+	locked = vmballoon_send_batched_lock(b, num_pages, is_2m_pages,
+			target);
+	if (locked > 0) {
+		for (i = 0; i < num_pages; i++) {
+			u64 pa = vmballoon_batch_get_pa(b->batch_page, i);
+			struct page *p = pfn_to_page(pa >> PAGE_SHIFT);
+
+			vmballoon_free_page(p, is_2m_pages);
+		}
+
+		return -EIO;
+	}
+
+	for (i = 0; i < num_pages; i++) {
+		u64 pa = vmballoon_batch_get_pa(b->batch_page, i);
+		struct page *p = pfn_to_page(pa >> PAGE_SHIFT);
+		struct vmballoon_page_size *page_size =
+				&b->page_sizes[is_2m_pages];
+
+		locked = vmballoon_batch_get_status(b->batch_page, i);
+
+		switch (locked) {
+		case VMW_BALLOON_SUCCESS:
+			list_add(&p->lru, &page_size->pages);
+			b->size += size_per_page;
+			break;
+		case VMW_BALLOON_ERROR_PPN_PINNED:
+		case VMW_BALLOON_ERROR_PPN_INVALID:
+			if (page_size->n_refused_pages
+					< VMW_BALLOON_MAX_REFUSED) {
+				list_add(&p->lru, &page_size->refused_pages);
+				page_size->n_refused_pages++;
+				break;
+			}
+			/* Fallthrough */
+		case VMW_BALLOON_ERROR_RESET:
+		case VMW_BALLOON_ERROR_PPN_NOTNEEDED:
+			vmballoon_free_page(p, is_2m_pages);
+			break;
+		default:
+			/* This should never happen */
+			WARN_ON_ONCE(true);
+		}
+	}
+
+	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_unlock_page(struct vmballoon *b, unsigned int num_pages,
+		bool is_2m_pages, unsigned int *target)
+{
+	struct page *page = b->page;
+	struct vmballoon_page_size *page_size = &b->page_sizes[false];
+
+	/* is_2m_pages can never happen as 2m pages support implies batching */
+
+	if (!vmballoon_send_unlock_page(b, page_to_pfn(page), target)) {
+		list_add(&page->lru, &page_size->pages);
+		return -EIO;
+	}
+
+	/* deallocate page */
+	vmballoon_free_page(page, false);
+	STATS_INC(b->stats.free[false]);
+
+	/* update balloon size */
+	b->size--;
+
+	return 0;
+}
+
+static int vmballoon_unlock_batched_page(struct vmballoon *b,
+				unsigned int num_pages, bool is_2m_pages,
+				unsigned int *target)
+{
+	int locked, i, ret = 0;
+	bool hv_success;
+	u16 size_per_page = vmballoon_page_size(is_2m_pages);
+
+	hv_success = vmballoon_send_batched_unlock(b, num_pages, is_2m_pages,
+			target);
+	if (!hv_success)
+		ret = -EIO;
+
+	for (i = 0; i < num_pages; i++) {
+		u64 pa = vmballoon_batch_get_pa(b->batch_page, i);
+		struct page *p = pfn_to_page(pa >> PAGE_SHIFT);
+		struct vmballoon_page_size *page_size =
+				&b->page_sizes[is_2m_pages];
+
+		locked = vmballoon_batch_get_status(b->batch_page, i);
+		if (!hv_success || locked != VMW_BALLOON_SUCCESS) {
+			/*
+			 * That page wasn't successfully unlocked by the
+			 * hypervisor, re-add it to the list of pages owned by
+			 * the balloon driver.
+			 */
+			list_add(&p->lru, &page_size->pages);
+		} else {
+			/* deallocate page */
+			vmballoon_free_page(p, is_2m_pages);
+			STATS_INC(b->stats.free[is_2m_pages]);
+
+			/* update balloon size */
+			b->size -= size_per_page;
+		}
+	}
+
+	return ret;
+}
+
+/*
+ * 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,
+		bool is_2m_pages)
+{
+	struct page *page, *next;
+	struct vmballoon_page_size *page_size =
+			&b->page_sizes[is_2m_pages];
+
+	list_for_each_entry_safe(page, next, &page_size->refused_pages, lru) {
+		list_del(&page->lru);
+		vmballoon_free_page(page, is_2m_pages);
+		STATS_INC(b->stats.refused_free[is_2m_pages]);
+	}
+
+	page_size->n_refused_pages = 0;
+}
+
+static void vmballoon_add_page(struct vmballoon *b, int idx, struct page *p)
+{
+	b->page = p;
+}
+
+static void vmballoon_add_batched_page(struct vmballoon *b, int idx,
+				struct page *p)
+{
+	vmballoon_batch_set_pa(b->batch_page, idx,
+			(u64)page_to_pfn(p) << PAGE_SHIFT);
+}
+
+/*
+ * 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 num_pages = 0;
+	int error = 0;
+	gfp_t flags = VMW_PAGE_ALLOC_NOSLEEP;
+	bool is_2m_pages;
+
+	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.
+	 */
+
+	/*
+	 * Start with no sleep allocation rate which may be higher
+	 * than sleeping allocation rate.
+	 */
+	is_2m_pages = b->supported_page_sizes == VMW_BALLOON_NUM_PAGE_SIZES;
+
+	pr_debug("%s - goal: %d",  __func__, b->target - b->size);
+
+	while (!b->reset_required &&
+		b->size + num_pages * vmballoon_page_size(is_2m_pages)
+		< b->target) {
+		struct page *page;
+
+		if (flags == VMW_PAGE_ALLOC_NOSLEEP)
+			STATS_INC(b->stats.alloc[is_2m_pages]);
+		else
+			STATS_INC(b->stats.sleep_alloc);
+
+		page = vmballoon_alloc_page(flags, is_2m_pages);
+		if (!page) {
+			STATS_INC(b->stats.alloc_fail[is_2m_pages]);
+
+			if (is_2m_pages) {
+				b->ops->lock(b, num_pages, true, &b->target);
+
+				/*
+				 * ignore errors from locking as we now switch
+				 * to 4k pages and we might get different
+				 * errors.
+				 */
+
+				num_pages = 0;
+				is_2m_pages = false;
+				continue;
+			}
+
+			if (flags == VMW_PAGE_ALLOC_CANSLEEP) {
+				/*
+				 * CANSLEEP page allocation failed, so guest
+				 * is under severe memory pressure. We just log
+				 * the event, but do not stop the inflation
+				 * due to its negative impact on performance.
+				 */
+				STATS_INC(b->stats.sleep_alloc_fail);
+				break;
+			}
+
+			/*
+			 * NOSLEEP page allocation failed, so the guest is
+			 * under memory pressure. Slowing down page alloctions
+			 * seems to be reasonable, but doing so might actually
+			 * cause the hypervisor to throttle us down, resulting
+			 * in degraded performance. We will count on the
+			 * scheduler and standard memory management mechanisms
+			 * for now.
+			 */
+			flags = VMW_PAGE_ALLOC_CANSLEEP;
+			continue;
+		}
+
+		b->ops->add_page(b, num_pages++, page);
+		if (num_pages == b->batch_max_pages) {
+			error = b->ops->lock(b, num_pages, is_2m_pages,
+					&b->target);
+			num_pages = 0;
+			if (error)
+				break;
+		}
+
+		cond_resched();
+	}
+
+	if (num_pages > 0)
+		b->ops->lock(b, num_pages, is_2m_pages, &b->target);
+
+	vmballoon_release_refused_pages(b, true);
+	vmballoon_release_refused_pages(b, false);
+}
+
+/*
+ * Decrease the size of the balloon allowing guest to use more memory.
+ */
+static void vmballoon_deflate(struct vmballoon *b)
+{
+	unsigned is_2m_pages;
+
+	pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
+
+	/* free pages to reach target */
+	for (is_2m_pages = 0; is_2m_pages < b->supported_page_sizes;
+			is_2m_pages++) {
+		struct page *page, *next;
+		unsigned int num_pages = 0;
+		struct vmballoon_page_size *page_size =
+				&b->page_sizes[is_2m_pages];
+
+		list_for_each_entry_safe(page, next, &page_size->pages, lru) {
+			if (b->reset_required ||
+				(b->target > 0 &&
+					b->size - num_pages
+					* vmballoon_page_size(is_2m_pages)
+				< b->target + vmballoon_page_size(true)))
+				break;
+
+			list_del(&page->lru);
+			b->ops->add_page(b, num_pages++, page);
+
+			if (num_pages == b->batch_max_pages) {
+				int error;
+
+				error = b->ops->unlock(b, num_pages,
+						is_2m_pages, &b->target);
+				num_pages = 0;
+				if (error)
+					return;
+			}
+
+			cond_resched();
+		}
+
+		if (num_pages > 0)
+			b->ops->unlock(b, num_pages, is_2m_pages, &b->target);
+	}
+}
+
+static const struct vmballoon_ops vmballoon_basic_ops = {
+	.add_page = vmballoon_add_page,
+	.lock = vmballoon_lock_page,
+	.unlock = vmballoon_unlock_page
+};
+
+static const struct vmballoon_ops vmballoon_batched_ops = {
+	.add_page = vmballoon_add_batched_page,
+	.lock = vmballoon_lock_batched_page,
+	.unlock = vmballoon_unlock_batched_page
+};
+
+static bool vmballoon_init_batching(struct vmballoon *b)
+{
+	struct page *page;
+
+	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	if (!page)
+		return false;
+
+	b->batch_page = page_address(page);
+	return true;
+}
+
+/*
+ * Receive notification and resize balloon
+ */
+static void vmballoon_doorbell(void *client_data)
+{
+	struct vmballoon *b = client_data;
+
+	STATS_INC(b->stats.doorbell);
+
+	mod_delayed_work(system_freezable_wq, &b->dwork, 0);
+}
+
+/*
+ * Clean up vmci doorbell
+ */
+static void vmballoon_vmci_cleanup(struct vmballoon *b)
+{
+	int error;
+
+	VMWARE_BALLOON_CMD(VMCI_DOORBELL_SET, VMCI_INVALID_ID,
+			VMCI_INVALID_ID, error);
+	STATS_INC(b->stats.doorbell_unset);
+
+	if (!vmci_handle_is_invalid(b->vmci_doorbell)) {
+		vmci_doorbell_destroy(b->vmci_doorbell);
+		b->vmci_doorbell = VMCI_INVALID_HANDLE;
+	}
+}
+
+/*
+ * Initialize vmci doorbell, to get notified as soon as balloon changes
+ */
+static int vmballoon_vmci_init(struct vmballoon *b)
+{
+	unsigned long error, dummy;
+
+	if ((b->capabilities & VMW_BALLOON_SIGNALLED_WAKEUP_CMD) == 0)
+		return 0;
+
+	error = vmci_doorbell_create(&b->vmci_doorbell, VMCI_FLAG_DELAYED_CB,
+				     VMCI_PRIVILEGE_FLAG_RESTRICTED,
+				     vmballoon_doorbell, b);
+
+	if (error != VMCI_SUCCESS)
+		goto fail;
+
+	error = VMWARE_BALLOON_CMD(VMCI_DOORBELL_SET, b->vmci_doorbell.context,
+				   b->vmci_doorbell.resource, dummy);
+
+	STATS_INC(b->stats.doorbell_set);
+
+	if (error != VMW_BALLOON_SUCCESS)
+		goto fail;
+
+	return 0;
+fail:
+	vmballoon_vmci_cleanup(b);
+	return -EIO;
+}
+
+/*
+ * 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)
+{
+	int error;
+
+	vmballoon_vmci_cleanup(b);
+
+	/* free all pages, skipping monitor unlock */
+	vmballoon_pop(b);
+
+	if (!vmballoon_send_start(b, VMW_BALLOON_CAPABILITIES))
+		return;
+
+	if ((b->capabilities & VMW_BALLOON_BATCHED_CMDS) != 0) {
+		b->ops = &vmballoon_batched_ops;
+		b->batch_max_pages = VMW_BALLOON_BATCH_MAX_PAGES;
+		if (!vmballoon_init_batching(b)) {
+			/*
+			 * We failed to initialize batching, inform the monitor
+			 * about it by sending a null capability.
+			 *
+			 * The guest will retry in one second.
+			 */
+			vmballoon_send_start(b, 0);
+			return;
+		}
+	} else if ((b->capabilities & VMW_BALLOON_BASIC_CMDS) != 0) {
+		b->ops = &vmballoon_basic_ops;
+		b->batch_max_pages = 1;
+	}
+
+	b->reset_required = false;
+
+	error = vmballoon_vmci_init(b);
+	if (error)
+		pr_err("failed to initialize vmci doorbell\n");
+
+	if (!vmballoon_send_guest_id(b))
+		pr_err("failed to send guest ID to the host\n");
+}
+
+/*
+ * 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->reset_required && vmballoon_send_get_target(b, &target)) {
+		/* update target, adjust size */
+		b->target = target;
+
+		if (b->size < target)
+			vmballoon_inflate(b);
+		else if (target == 0 ||
+				b->size > target + vmballoon_page_size(true))
+			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 capabilities info */
+	seq_printf(f,
+		   "balloon capabilities:   %#4x\n"
+		   "used capabilities:      %#4lx\n"
+		   "is resetting:           %c\n",
+		   VMW_BALLOON_CAPABILITIES, b->capabilities,
+		   b->reset_required ? 'y' : 'n');
+
+	/* format size info */
+	seq_printf(f,
+		   "target:             %8d pages\n"
+		   "current:            %8d pages\n",
+		   b->target, b->size);
+
+	seq_printf(f,
+		   "\n"
+		   "timer:              %8u\n"
+		   "doorbell:           %8u\n"
+		   "start:              %8u (%4u failed)\n"
+		   "guestType:          %8u (%4u failed)\n"
+		   "2m-lock:            %8u (%4u failed)\n"
+		   "lock:               %8u (%4u failed)\n"
+		   "2m-unlock:          %8u (%4u failed)\n"
+		   "unlock:             %8u (%4u failed)\n"
+		   "target:             %8u (%4u failed)\n"
+		   "prim2mAlloc:        %8u (%4u failed)\n"
+		   "primNoSleepAlloc:   %8u (%4u failed)\n"
+		   "primCanSleepAlloc:  %8u (%4u failed)\n"
+		   "prim2mFree:         %8u\n"
+		   "primFree:           %8u\n"
+		   "err2mAlloc:         %8u\n"
+		   "errAlloc:           %8u\n"
+		   "err2mFree:          %8u\n"
+		   "errFree:            %8u\n"
+		   "doorbellSet:        %8u\n"
+		   "doorbellUnset:      %8u\n",
+		   stats->timer,
+		   stats->doorbell,
+		   stats->start, stats->start_fail,
+		   stats->guest_type, stats->guest_type_fail,
+		   stats->lock[true],  stats->lock_fail[true],
+		   stats->lock[false],  stats->lock_fail[false],
+		   stats->unlock[true], stats->unlock_fail[true],
+		   stats->unlock[false], stats->unlock_fail[false],
+		   stats->target, stats->target_fail,
+		   stats->alloc[true], stats->alloc_fail[true],
+		   stats->alloc[false], stats->alloc_fail[false],
+		   stats->sleep_alloc, stats->sleep_alloc_fail,
+		   stats->free[true],
+		   stats->free[false],
+		   stats->refused_alloc[true], stats->refused_alloc[false],
+		   stats->refused_free[true], stats->refused_free[false],
+		   stats->doorbell_set, stats->doorbell_unset);
+
+	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;
+	unsigned is_2m_pages;
+	/*
+	 * Check if we are running on VMware's hypervisor and bail out
+	 * if we are not.
+	 */
+	if (x86_hyper_type != X86_HYPER_VMWARE)
+		return -ENODEV;
+
+	for (is_2m_pages = 0; is_2m_pages < VMW_BALLOON_NUM_PAGE_SIZES;
+			is_2m_pages++) {
+		INIT_LIST_HEAD(&balloon.page_sizes[is_2m_pages].pages);
+		INIT_LIST_HEAD(&balloon.page_sizes[is_2m_pages].refused_pages);
+	}
+
+	INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);
+
+	error = vmballoon_debugfs_init(&balloon);
+	if (error)
+		return error;
+
+	balloon.vmci_doorbell = VMCI_INVALID_HANDLE;
+	balloon.batch_page = NULL;
+	balloon.page = NULL;
+	balloon.reset_required = true;
+
+	queue_delayed_work(system_freezable_wq, &balloon.dwork, 0);
+
+	return 0;
+}
+
+/*
+ * Using late_initcall() instead of module_init() allows the balloon to use the
+ * VMCI doorbell even when the balloon is built into the kernel. Otherwise the
+ * VMCI is probed only after the balloon is initialized. If the balloon is used
+ * as a module, late_initcall() is equivalent to module_init().
+ */
+late_initcall(vmballoon_init);
+
+static void __exit vmballoon_exit(void)
+{
+	vmballoon_vmci_cleanup(&balloon);
+	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, 0);
+	vmballoon_pop(&balloon);
+}
+module_exit(vmballoon_exit);