1 files changed, 843 insertions, 191 deletions

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 1f572c00a1be..74fe59f5a78c 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -1,52 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Virtio balloon implementation, inspired by Dor Laor and Marcelo
  * Tosatti's implementations.
  *
  *  Copyright 2008 Rusty Russell IBM Corporation
- *
- *  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; either version 2 of the License, or
- *  (at your option) any 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.  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
  */
 
 #include <linux/virtio.h>
 #include <linux/virtio_balloon.h>
 #include <linux/swap.h>
-#include <linux/kthread.h>
-#include <linux/freezer.h>
+#include <linux/workqueue.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/balloon_compaction.h>
+#include <linux/oom.h>
+#include <linux/wait.h>
+#include <linux/mm.h>
+#include <linux/page_reporting.h>
 
 /*
  * Balloon device works in 4K page units.  So each page is pointed to by
  * multiple balloon pages.  All memory counters in this driver are in balloon
  * page units.
  */
-#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
+#define VIRTIO_BALLOON_PAGES_PER_PAGE (unsigned int)(PAGE_SIZE >> VIRTIO_BALLOON_PFN_SHIFT)
 #define VIRTIO_BALLOON_ARRAY_PFNS_MAX 256
+/* Maximum number of (4k) pages to deflate on OOM notifications. */
+#define VIRTIO_BALLOON_OOM_NR_PAGES 256
+#define VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY 80
+
+#define VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG (__GFP_NORETRY | __GFP_NOWARN | \
+					     __GFP_NOMEMALLOC)
+/* The order of free page blocks to report to host */
+#define VIRTIO_BALLOON_HINT_BLOCK_ORDER MAX_PAGE_ORDER
+/* The size of a free page block in bytes */
+#define VIRTIO_BALLOON_HINT_BLOCK_BYTES \
+	(1 << (VIRTIO_BALLOON_HINT_BLOCK_ORDER + PAGE_SHIFT))
+#define VIRTIO_BALLOON_HINT_BLOCK_PAGES (1 << VIRTIO_BALLOON_HINT_BLOCK_ORDER)
+
+enum virtio_balloon_vq {
+	VIRTIO_BALLOON_VQ_INFLATE,
+	VIRTIO_BALLOON_VQ_DEFLATE,
+	VIRTIO_BALLOON_VQ_STATS,
+	VIRTIO_BALLOON_VQ_FREE_PAGE,
+	VIRTIO_BALLOON_VQ_REPORTING,
+	VIRTIO_BALLOON_VQ_MAX
+};
 
-struct virtio_balloon
-{
-	struct virtio_device *vdev;
-	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq;
-
-	/* Where the ballooning thread waits for config to change. */
-	wait_queue_head_t config_change;
+enum virtio_balloon_config_read {
+	VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
+};
 
-	/* The thread servicing the balloon. */
-	struct task_struct *thread;
+struct virtio_balloon {
+	struct virtio_device *vdev;
+	struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq;
+
+	/* Balloon's own wq for cpu-intensive work items */
+	struct workqueue_struct *balloon_wq;
+	/* The free page reporting work item submitted to the balloon wq */
+	struct work_struct report_free_page_work;
+
+	/* The balloon servicing is delegated to a freezable workqueue. */
+	struct work_struct update_balloon_stats_work;
+	struct work_struct update_balloon_size_work;
+
+	/* Prevent updating balloon when it is being canceled. */
+	spinlock_t stop_update_lock;
+	bool stop_update;
+	/* Bitmap to indicate if reading the related config fields are needed */
+	unsigned long config_read_bitmap;
+
+	/* The list of allocated free pages, waiting to be given back to mm */
+	struct list_head free_page_list;
+	spinlock_t free_page_list_lock;
+	/* The number of free page blocks on the above list */
+	unsigned long num_free_page_blocks;
+	/*
+	 * The cmd id received from host.
+	 * Read it via virtio_balloon_cmd_id_received to get the latest value
+	 * sent from host.
+	 */
+	u32 cmd_id_received_cache;
+	/* The cmd id that is actively in use */
+	__virtio32 cmd_id_active;
+	/* Buffer to store the stop sign */
+	__virtio32 cmd_id_stop;
 
 	/* Waiting for host to ack the pages we released. */
 	wait_queue_head_t acked;
@@ -59,21 +98,38 @@ struct virtio_balloon
 	 * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
 	 * to num_pages above.
 	 */
-	struct balloon_dev_info *vb_dev_info;
+	struct balloon_dev_info vb_dev_info;
 
 	/* Synchronize access/update to this struct virtio_balloon elements */
 	struct mutex balloon_lock;
 
 	/* The array of pfns we tell the Host about. */
 	unsigned int num_pfns;
-	u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
+	__virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
 
 	/* Memory statistics */
-	int need_stats_update;
 	struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
+
+	/* Shrinker to return free pages - VIRTIO_BALLOON_F_FREE_PAGE_HINT */
+	struct shrinker *shrinker;
+
+	/* OOM notifier to deflate on OOM - VIRTIO_BALLOON_F_DEFLATE_ON_OOM */
+	struct notifier_block oom_nb;
+
+	/* Free page reporting device */
+	struct virtqueue *reporting_vq;
+	struct page_reporting_dev_info pr_dev_info;
+
+	/* State for keeping the wakeup_source active while adjusting the balloon */
+	spinlock_t wakeup_lock;
+	bool processing_wakeup_event;
+	u32 wakeup_signal_mask;
 };
 
-static struct virtio_device_id id_table[] = {
+#define VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST (1 << 0)
+#define VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS (1 << 1)
+
+static const struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
 	{ 0 },
 };
@@ -87,10 +143,34 @@ static u32 page_to_balloon_pfn(struct page *page)
 	return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
 }
 
-static struct page *balloon_pfn_to_page(u32 pfn)
+static void start_wakeup_event(struct virtio_balloon *vb, u32 mask)
 {
-	BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
-	return pfn_to_page(pfn / VIRTIO_BALLOON_PAGES_PER_PAGE);
+	unsigned long flags;
+
+	spin_lock_irqsave(&vb->wakeup_lock, flags);
+	vb->wakeup_signal_mask |= mask;
+	if (!vb->processing_wakeup_event) {
+		vb->processing_wakeup_event = true;
+		pm_stay_awake(&vb->vdev->dev);
+	}
+	spin_unlock_irqrestore(&vb->wakeup_lock, flags);
+}
+
+static void process_wakeup_event(struct virtio_balloon *vb, u32 mask)
+{
+	spin_lock_irq(&vb->wakeup_lock);
+	vb->wakeup_signal_mask &= ~mask;
+	spin_unlock_irq(&vb->wakeup_lock);
+}
+
+static void finish_wakeup_event(struct virtio_balloon *vb)
+{
+	spin_lock_irq(&vb->wakeup_lock);
+	if (!vb->wakeup_signal_mask && vb->processing_wakeup_event) {
+		vb->processing_wakeup_event = false;
+		pm_relax(&vb->vdev->dev);
+	}
+	spin_unlock_irq(&vb->wakeup_lock);
 }
 
 static void balloon_ack(struct virtqueue *vq)
@@ -108,35 +188,70 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 
 	/* We should always be able to add one buffer to an empty queue. */
-	if (virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL) < 0)
-		BUG();
+	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 	virtqueue_kick(vq);
 
 	/* When host has read buffer, this completes via balloon_ack */
 	wait_event(vb->acked, virtqueue_get_buf(vq, &len));
+
 }
 
-static void set_page_pfns(u32 pfns[], struct page *page)
+static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
+				   struct scatterlist *sg, unsigned int nents)
+{
+	struct virtio_balloon *vb =
+		container_of(pr_dev_info, struct virtio_balloon, pr_dev_info);
+	struct virtqueue *vq = vb->reporting_vq;
+	unsigned int unused, err;
+
+	/* We should always be able to add these buffers to an empty queue. */
+	err = virtqueue_add_inbuf(vq, sg, nents, vb, GFP_NOWAIT);
+
+	/*
+	 * In the extremely unlikely case that something has occurred and we
+	 * are able to trigger an error we will simply display a warning
+	 * and exit without actually processing the pages.
+	 */
+	if (WARN_ON_ONCE(err))
+		return err;
+
+	virtqueue_kick(vq);
+
+	/* When host has read buffer, this completes via balloon_ack */
+	wait_event(vb->acked, virtqueue_get_buf(vq, &unused));
+
+	return 0;
+}
+
+static void set_page_pfns(struct virtio_balloon *vb,
+			  __virtio32 pfns[], struct page *page)
 {
 	unsigned int i;
 
-	/* Set balloon pfns pointing at this page.
-	 * Note that the first pfn points at start of the page. */
+	BUILD_BUG_ON(VIRTIO_BALLOON_PAGES_PER_PAGE > VIRTIO_BALLOON_ARRAY_PFNS_MAX);
+
+	/*
+	 * Set balloon pfns pointing at this page.
+	 * Note that the first pfn points at start of the page.
+	 */
 	for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
-		pfns[i] = page_to_balloon_pfn(page) + i;
+		pfns[i] = cpu_to_virtio32(vb->vdev,
+					  page_to_balloon_pfn(page) + i);
 }
 
-static void fill_balloon(struct virtio_balloon *vb, size_t num)
+static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
 {
-	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
+	unsigned int num_allocated_pages;
+	unsigned int num_pfns;
+	struct page *page;
+	LIST_HEAD(pages);
 
 	/* We can only do one array worth at a time. */
 	num = min(num, ARRAY_SIZE(vb->pfns));
 
-	mutex_lock(&vb->balloon_lock);
-	for (vb->num_pfns = 0; vb->num_pfns < num;
-	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
-		struct page *page = balloon_page_enqueue(vb_dev_info);
+	for (num_pfns = 0; num_pfns < num;
+	     num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
+		page = balloon_page_alloc();
 
 		if (!page) {
 			dev_info_ratelimited(&vb->vdev->dev,
@@ -146,47 +261,72 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
 			msleep(200);
 			break;
 		}
-		set_page_pfns(vb->pfns + vb->num_pfns, page);
+
+		balloon_page_push(&pages, page);
+	}
+
+	mutex_lock(&vb->balloon_lock);
+
+	vb->num_pfns = 0;
+
+	while ((page = balloon_page_pop(&pages))) {
+		balloon_page_enqueue(&vb->vb_dev_info, page);
+
+		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
 		vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE;
-		adjust_managed_page_count(page, -1);
+		if (!virtio_has_feature(vb->vdev,
+					VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+			adjust_managed_page_count(page, -1);
+		vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE;
 	}
 
+	num_allocated_pages = vb->num_pfns;
 	/* Did we get any? */
 	if (vb->num_pfns != 0)
 		tell_host(vb, vb->inflate_vq);
 	mutex_unlock(&vb->balloon_lock);
+
+	return num_allocated_pages;
 }
 
-static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
+static void release_pages_balloon(struct virtio_balloon *vb,
+				 struct list_head *pages)
 {
-	unsigned int i;
-
-	/* Find pfns pointing at start of each page, get pages and free them. */
-	for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
-		struct page *page = balloon_pfn_to_page(pfns[i]);
-		balloon_page_free(page);
-		adjust_managed_page_count(page, 1);
+	struct page *page, *next;
+
+	list_for_each_entry_safe(page, next, pages, lru) {
+		if (!virtio_has_feature(vb->vdev,
+					VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+			adjust_managed_page_count(page, 1);
+		list_del(&page->lru);
+		put_page(page); /* balloon reference */
 	}
 }
 
-static void leak_balloon(struct virtio_balloon *vb, size_t num)
+static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num)
 {
+	unsigned int num_freed_pages;
 	struct page *page;
-	struct balloon_dev_info *vb_dev_info = vb->vb_dev_info;
+	struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
+	LIST_HEAD(pages);
 
 	/* We can only do one array worth at a time. */
 	num = min(num, ARRAY_SIZE(vb->pfns));
 
 	mutex_lock(&vb->balloon_lock);
+	/* We can't release more pages than taken */
+	num = min(num, (size_t)vb->num_pages);
 	for (vb->num_pfns = 0; vb->num_pfns < num;
 	     vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
 		page = balloon_page_dequeue(vb_dev_info);
 		if (!page)
 			break;
-		set_page_pfns(vb->pfns + vb->num_pfns, page);
+		set_page_pfns(vb, vb->pfns + vb->num_pfns, page);
+		list_add(&page->lru, &pages);
 		vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE;
 	}
 
+	num_freed_pages = vb->num_pfns;
 	/*
 	 * Note that if
 	 * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST);
@@ -194,39 +334,92 @@ static void leak_balloon(struct virtio_balloon *vb, size_t num)
 	 */
 	if (vb->num_pfns != 0)
 		tell_host(vb, vb->deflate_vq);
+	release_pages_balloon(vb, &pages);
 	mutex_unlock(&vb->balloon_lock);
-	release_pages_by_pfn(vb->pfns, vb->num_pfns);
+	return num_freed_pages;
 }
 
 static inline void update_stat(struct virtio_balloon *vb, int idx,
 			       u16 tag, u64 val)
 {
 	BUG_ON(idx >= VIRTIO_BALLOON_S_NR);
-	vb->stats[idx].tag = tag;
-	vb->stats[idx].val = val;
+	vb->stats[idx].tag = cpu_to_virtio16(vb->vdev, tag);
+	vb->stats[idx].val = cpu_to_virtio64(vb->vdev, val);
 }
 
 #define pages_to_bytes(x) ((u64)(x) << PAGE_SHIFT)
 
-static void update_balloon_stats(struct virtio_balloon *vb)
+#ifdef CONFIG_VM_EVENT_COUNTERS
+/* Return the number of entries filled by vm events */
+static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
 {
 	unsigned long events[NR_VM_EVENT_ITEMS];
-	struct sysinfo i;
-	int idx = 0;
+	unsigned int idx = 0;
+	unsigned int zid;
+	unsigned long stall = 0;
 
 	all_vm_events(events);
-	si_meminfo(&i);
-
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
-				pages_to_bytes(events[PSWPIN]));
+		    pages_to_bytes(events[PSWPIN]));
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
-				pages_to_bytes(events[PSWPOUT]));
+		    pages_to_bytes(events[PSWPOUT]));
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MAJFLT, events[PGMAJFAULT]);
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MINFLT, events[PGFAULT]);
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_OOM_KILL, events[OOM_KILL]);
+
+	/* sum all the stall events */
+	for (zid = 0; zid < MAX_NR_ZONES; zid++)
+		stall += events[ALLOCSTALL_NORMAL - ZONE_NORMAL + zid];
+
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_ALLOC_STALL, stall);
+
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_ASYNC_SCAN,
+		    pages_to_bytes(events[PGSCAN_KSWAPD]));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_DIRECT_SCAN,
+		    pages_to_bytes(events[PGSCAN_DIRECT]));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_ASYNC_RECLAIM,
+		    pages_to_bytes(events[PGSTEAL_KSWAPD]));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_DIRECT_RECLAIM,
+		    pages_to_bytes(events[PGSTEAL_DIRECT]));
+
+#ifdef CONFIG_HUGETLB_PAGE
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGALLOC,
+		    events[HTLB_BUDDY_PGALLOC]);
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_HTLB_PGFAIL,
+		    events[HTLB_BUDDY_PGALLOC_FAIL]);
+#endif /* CONFIG_HUGETLB_PAGE */
+
+	return idx;
+}
+#else /* CONFIG_VM_EVENT_COUNTERS */
+static inline unsigned int update_balloon_vm_stats(struct virtio_balloon *vb)
+{
+	return 0;
+}
+#endif /* CONFIG_VM_EVENT_COUNTERS */
+
+static unsigned int update_balloon_stats(struct virtio_balloon *vb)
+{
+	struct sysinfo i;
+	unsigned int idx;
+	long available;
+	unsigned long caches;
+
+	idx = update_balloon_vm_stats(vb);
+
+	si_meminfo(&i);
+	available = si_mem_available();
+	caches = global_node_page_state(NR_FILE_PAGES);
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMFREE,
 				pages_to_bytes(i.freeram));
 	update_stat(vb, idx++, VIRTIO_BALLOON_S_MEMTOT,
 				pages_to_bytes(i.totalram));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_AVAIL,
+				pages_to_bytes(available));
+	update_stat(vb, idx++, VIRTIO_BALLOON_S_CACHES,
+				pages_to_bytes(caches));
+
+	return idx;
 }
 
 /*
@@ -235,128 +428,386 @@ static void update_balloon_stats(struct virtio_balloon *vb)
  * with a single buffer.  From that point forward, all conversations consist of
  * a hypervisor request (a call to this function) which directs us to refill
  * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
- * we notify our kthread which does the actual work via stats_handle_request().
+ * we delegate the job to a freezable workqueue that will do the actual work via
+ * stats_handle_request().
  */
 static void stats_request(struct virtqueue *vq)
 {
 	struct virtio_balloon *vb = vq->vdev->priv;
 
-	vb->need_stats_update = 1;
-	wake_up(&vb->config_change);
+	spin_lock(&vb->stop_update_lock);
+	if (!vb->stop_update) {
+		start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
+		queue_work(system_freezable_wq, &vb->update_balloon_stats_work);
+	}
+	spin_unlock(&vb->stop_update_lock);
 }
 
 static void stats_handle_request(struct virtio_balloon *vb)
 {
 	struct virtqueue *vq;
 	struct scatterlist sg;
-	unsigned int len;
+	unsigned int len, num_stats;
 
-	vb->need_stats_update = 0;
-	update_balloon_stats(vb);
+	num_stats = update_balloon_stats(vb);
 
 	vq = vb->stats_vq;
 	if (!virtqueue_get_buf(vq, &len))
 		return;
-	sg_init_one(&sg, vb->stats, sizeof(vb->stats));
-	if (virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL) < 0)
-		BUG();
+	sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
+	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
 	virtqueue_kick(vq);
 }
 
+static inline s64 towards_target(struct virtio_balloon *vb)
+{
+	s64 target;
+	u32 num_pages;
+
+	/* Legacy balloon config space is LE, unlike all other devices. */
+	virtio_cread_le(vb->vdev, struct virtio_balloon_config, num_pages,
+			&num_pages);
+
+	/*
+	 * Aligned up to guest page size to avoid inflating and deflating
+	 * balloon endlessly.
+	 */
+	target = ALIGN(num_pages, VIRTIO_BALLOON_PAGES_PER_PAGE);
+	return target - vb->num_pages;
+}
+
+/* Gives back @num_to_return blocks of free pages to mm. */
+static unsigned long return_free_pages_to_mm(struct virtio_balloon *vb,
+					     unsigned long num_to_return)
+{
+	struct page *page;
+	unsigned long num_returned;
+
+	spin_lock_irq(&vb->free_page_list_lock);
+	for (num_returned = 0; num_returned < num_to_return; num_returned++) {
+		page = balloon_page_pop(&vb->free_page_list);
+		if (!page)
+			break;
+		__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
+	}
+	vb->num_free_page_blocks -= num_returned;
+	spin_unlock_irq(&vb->free_page_list_lock);
+
+	return num_returned;
+}
+
+static void virtio_balloon_queue_free_page_work(struct virtio_balloon *vb)
+{
+	if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		return;
+
+	/* No need to queue the work if the bit was already set. */
+	if (test_and_set_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
+			     &vb->config_read_bitmap))
+		return;
+
+	queue_work(vb->balloon_wq, &vb->report_free_page_work);
+}
+
+static void start_update_balloon_size(struct virtio_balloon *vb)
+{
+	start_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
+	queue_work(system_freezable_wq, &vb->update_balloon_size_work);
+}
+
 static void virtballoon_changed(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;
+	unsigned long flags;
 
-	wake_up(&vb->config_change);
+	spin_lock_irqsave(&vb->stop_update_lock, flags);
+	if (!vb->stop_update) {
+		start_update_balloon_size(vb);
+		virtio_balloon_queue_free_page_work(vb);
+	}
+	spin_unlock_irqrestore(&vb->stop_update_lock, flags);
 }
 
-static inline s64 towards_target(struct virtio_balloon *vb)
+static void update_balloon_size(struct virtio_balloon *vb)
 {
-	__le32 v;
-	s64 target;
+	u32 actual = vb->num_pages;
 
-	vb->vdev->config->get(vb->vdev,
-			      offsetof(struct virtio_balloon_config, num_pages),
-			      &v, sizeof(v));
-	target = le32_to_cpu(v);
-	return target - vb->num_pages;
+	/* Legacy balloon config space is LE, unlike all other devices. */
+	virtio_cwrite_le(vb->vdev, struct virtio_balloon_config, actual,
+			 &actual);
 }
 
-static void update_balloon_size(struct virtio_balloon *vb)
+static void update_balloon_stats_func(struct work_struct *work)
 {
-	__le32 actual = cpu_to_le32(vb->num_pages);
+	struct virtio_balloon *vb;
+
+	vb = container_of(work, struct virtio_balloon,
+			  update_balloon_stats_work);
 
-	vb->vdev->config->set(vb->vdev,
-			      offsetof(struct virtio_balloon_config, actual),
-			      &actual, sizeof(actual));
+	process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_STATS);
+	stats_handle_request(vb);
+	finish_wakeup_event(vb);
 }
 
-static int balloon(void *_vballoon)
+static void update_balloon_size_func(struct work_struct *work)
 {
-	struct virtio_balloon *vb = _vballoon;
+	struct virtio_balloon *vb;
+	s64 diff;
+
+	vb = container_of(work, struct virtio_balloon,
+			  update_balloon_size_work);
 
-	set_freezable();
-	while (!kthread_should_stop()) {
-		s64 diff;
+	process_wakeup_event(vb, VIRTIO_BALLOON_WAKEUP_SIGNAL_ADJUST);
 
-		try_to_freeze();
-		wait_event_interruptible(vb->config_change,
-					 (diff = towards_target(vb)) != 0
-					 || vb->need_stats_update
-					 || kthread_should_stop()
-					 || freezing(current));
-		if (vb->need_stats_update)
-			stats_handle_request(vb);
+	diff = towards_target(vb);
+
+	if (diff) {
 		if (diff > 0)
-			fill_balloon(vb, diff);
-		else if (diff < 0)
-			leak_balloon(vb, -diff);
+			diff -= fill_balloon(vb, diff);
+		else
+			diff += leak_balloon(vb, -diff);
 		update_balloon_size(vb);
 	}
-	return 0;
+
+	if (diff)
+		queue_work(system_freezable_wq, work);
+	else
+		finish_wakeup_event(vb);
 }
 
 static int init_vqs(struct virtio_balloon *vb)
 {
-	struct virtqueue *vqs[3];
-	vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
-	const char *names[] = { "inflate", "deflate", "stats" };
-	int err, nvqs;
+	struct virtqueue_info vqs_info[VIRTIO_BALLOON_VQ_MAX] = {};
+	struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
+	int err;
 
 	/*
-	 * We expect two virtqueues: inflate and deflate, and
-	 * optionally stat.
+	 * Inflateq and deflateq are used unconditionally. The names[]
+	 * will be NULL if the related feature is not enabled, which will
+	 * cause no allocation for the corresponding virtqueue in find_vqs.
 	 */
-	nvqs = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) ? 3 : 2;
-	err = vb->vdev->config->find_vqs(vb->vdev, nvqs, vqs, callbacks, names);
+	vqs_info[VIRTIO_BALLOON_VQ_INFLATE].callback = balloon_ack;
+	vqs_info[VIRTIO_BALLOON_VQ_INFLATE].name = "inflate";
+	vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].callback = balloon_ack;
+	vqs_info[VIRTIO_BALLOON_VQ_DEFLATE].name = "deflate";
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
+		vqs_info[VIRTIO_BALLOON_VQ_STATS].name = "stats";
+		vqs_info[VIRTIO_BALLOON_VQ_STATS].callback = stats_request;
+	}
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		vqs_info[VIRTIO_BALLOON_VQ_FREE_PAGE].name = "free_page_vq";
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
+		vqs_info[VIRTIO_BALLOON_VQ_REPORTING].name = "reporting_vq";
+		vqs_info[VIRTIO_BALLOON_VQ_REPORTING].callback = balloon_ack;
+	}
+
+	err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
+			      vqs_info, NULL);
 	if (err)
 		return err;
 
-	vb->inflate_vq = vqs[0];
-	vb->deflate_vq = vqs[1];
+	vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
+	vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 		struct scatterlist sg;
-		vb->stats_vq = vqs[2];
+		unsigned int num_stats;
+		vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
 
 		/*
 		 * Prime this virtqueue with one buffer so the hypervisor can
-		 * use it to signal us later.
+		 * use it to signal us later (it can't be broken yet!).
 		 */
-		sg_init_one(&sg, vb->stats, sizeof vb->stats);
-		if (virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb, GFP_KERNEL)
-		    < 0)
-			BUG();
+		num_stats = update_balloon_stats(vb);
+
+		sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
+		err = virtqueue_add_outbuf(vb->stats_vq, &sg, 1, vb,
+					   GFP_KERNEL);
+		if (err) {
+			dev_warn(&vb->vdev->dev, "%s: add stat_vq failed\n",
+				 __func__);
+			return err;
+		}
 		virtqueue_kick(vb->stats_vq);
 	}
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
+		vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
+
+	return 0;
+}
+
+static u32 virtio_balloon_cmd_id_received(struct virtio_balloon *vb)
+{
+	if (test_and_clear_bit(VIRTIO_BALLOON_CONFIG_READ_CMD_ID,
+			       &vb->config_read_bitmap)) {
+		/* Legacy balloon config space is LE, unlike all other devices. */
+		virtio_cread_le(vb->vdev, struct virtio_balloon_config,
+				free_page_hint_cmd_id,
+				&vb->cmd_id_received_cache);
+	}
+
+	return vb->cmd_id_received_cache;
+}
+
+static int send_cmd_id_start(struct virtio_balloon *vb)
+{
+	struct scatterlist sg;
+	struct virtqueue *vq = vb->free_page_vq;
+	int err, unused;
+
+	/* Detach all the used buffers from the vq */
+	while (virtqueue_get_buf(vq, &unused))
+		;
+
+	vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
+					virtio_balloon_cmd_id_received(vb));
+	sg_init_one(&sg, &vb->cmd_id_active, sizeof(vb->cmd_id_active));
+	err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_active, GFP_KERNEL);
+	if (!err)
+		virtqueue_kick(vq);
+	return err;
+}
+
+static int send_cmd_id_stop(struct virtio_balloon *vb)
+{
+	struct scatterlist sg;
+	struct virtqueue *vq = vb->free_page_vq;
+	int err, unused;
+
+	/* Detach all the used buffers from the vq */
+	while (virtqueue_get_buf(vq, &unused))
+		;
+
+	sg_init_one(&sg, &vb->cmd_id_stop, sizeof(vb->cmd_id_stop));
+	err = virtqueue_add_outbuf(vq, &sg, 1, &vb->cmd_id_stop, GFP_KERNEL);
+	if (!err)
+		virtqueue_kick(vq);
+	return err;
+}
+
+static int get_free_page_and_send(struct virtio_balloon *vb)
+{
+	struct virtqueue *vq = vb->free_page_vq;
+	struct page *page;
+	struct scatterlist sg;
+	int err, unused;
+	void *p;
+
+	/* Detach all the used buffers from the vq */
+	while (virtqueue_get_buf(vq, &unused))
+		;
+
+	page = alloc_pages(VIRTIO_BALLOON_FREE_PAGE_ALLOC_FLAG,
+			   VIRTIO_BALLOON_HINT_BLOCK_ORDER);
+	/*
+	 * When the allocation returns NULL, it indicates that we have got all
+	 * the possible free pages, so return -EINTR to stop.
+	 */
+	if (!page)
+		return -EINTR;
+
+	p = page_address(page);
+	sg_init_one(&sg, p, VIRTIO_BALLOON_HINT_BLOCK_BYTES);
+	/* There is always 1 entry reserved for the cmd id to use. */
+	if (vq->num_free > 1) {
+		err = virtqueue_add_inbuf(vq, &sg, 1, p, GFP_KERNEL);
+		if (unlikely(err)) {
+			__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
+			return err;
+		}
+		virtqueue_kick(vq);
+		spin_lock_irq(&vb->free_page_list_lock);
+		balloon_page_push(&vb->free_page_list, page);
+		vb->num_free_page_blocks++;
+		spin_unlock_irq(&vb->free_page_list_lock);
+	} else {
+		/*
+		 * The vq has no available entry to add this page block, so
+		 * just free it.
+		 */
+		__free_pages(page, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
+	}
+
 	return 0;
 }
 
-static const struct address_space_operations virtio_balloon_aops;
+static int send_free_pages(struct virtio_balloon *vb)
+{
+	int err;
+	u32 cmd_id_active;
+
+	while (1) {
+		/*
+		 * If a stop id or a new cmd id was just received from host,
+		 * stop the reporting.
+		 */
+		cmd_id_active = virtio32_to_cpu(vb->vdev, vb->cmd_id_active);
+		if (unlikely(cmd_id_active !=
+			     virtio_balloon_cmd_id_received(vb)))
+			break;
+
+		/*
+		 * The free page blocks are allocated and sent to host one by
+		 * one.
+		 */
+		err = get_free_page_and_send(vb);
+		if (err == -EINTR)
+			break;
+		else if (unlikely(err))
+			return err;
+	}
+
+	return 0;
+}
+
+static void virtio_balloon_report_free_page(struct virtio_balloon *vb)
+{
+	int err;
+	struct device *dev = &vb->vdev->dev;
+
+	/* Start by sending the received cmd id to host with an outbuf. */
+	err = send_cmd_id_start(vb);
+	if (unlikely(err))
+		dev_err(dev, "Failed to send a start id, err = %d\n", err);
+
+	err = send_free_pages(vb);
+	if (unlikely(err))
+		dev_err(dev, "Failed to send a free page, err = %d\n", err);
+
+	/* End by sending a stop id to host with an outbuf. */
+	err = send_cmd_id_stop(vb);
+	if (unlikely(err))
+		dev_err(dev, "Failed to send a stop id, err = %d\n", err);
+}
+
+static void report_free_page_func(struct work_struct *work)
+{
+	struct virtio_balloon *vb = container_of(work, struct virtio_balloon,
+						 report_free_page_work);
+	u32 cmd_id_received;
+
+	cmd_id_received = virtio_balloon_cmd_id_received(vb);
+	if (cmd_id_received == VIRTIO_BALLOON_CMD_ID_DONE) {
+		/* Pass ULONG_MAX to give back all the free pages */
+		return_free_pages_to_mm(vb, ULONG_MAX);
+	} else if (cmd_id_received != VIRTIO_BALLOON_CMD_ID_STOP &&
+		   cmd_id_received !=
+		   virtio32_to_cpu(vb->vdev, vb->cmd_id_active)) {
+		virtio_balloon_report_free_page(vb);
+	}
+}
+
 #ifdef CONFIG_BALLOON_COMPACTION
 /*
  * virtballoon_migratepage - perform the balloon page migration on behalf of
- *			     a compation thread.     (called under page lock)
- * @mapping: the page->mapping which will be assigned to the new migrated page.
+ *			     a compaction thread.     (called under page lock)
+ * @vb_dev_info: the balloon device
  * @newpage: page that will replace the isolated page after migration finishes.
  * @page   : the isolated (old) page that is about to be migrated to newpage.
  * @mode   : compaction mode -- not used for balloon page migration.
@@ -369,19 +820,15 @@ static const struct address_space_operations virtio_balloon_aops;
  *  2) update the host about the old page removed from vb->pages list;
  *
  * This function preforms the balloon page migration task.
- * Called through balloon_mapping->a_ops->migratepage
+ * Called through movable_operations->migrate_page
  */
-int virtballoon_migratepage(struct address_space *mapping,
+static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
 		struct page *newpage, struct page *page, enum migrate_mode mode)
 {
-	struct balloon_dev_info *vb_dev_info = balloon_page_device(page);
-	struct virtio_balloon *vb;
+	struct virtio_balloon *vb = container_of(vb_dev_info,
+			struct virtio_balloon, vb_dev_info);
 	unsigned long flags;
 
-	BUG_ON(!vb_dev_info);
-
-	vb = vb_dev_info->balloon_device;
-
 	/*
 	 * In order to avoid lock contention while migrating pages concurrently
 	 * to leak_balloon() or fill_balloon() we just give up the balloon_lock
@@ -393,96 +840,260 @@ int virtballoon_migratepage(struct address_space *mapping,
 	if (!mutex_trylock(&vb->balloon_lock))
 		return -EAGAIN;
 
+	get_page(newpage); /* balloon reference */
+
+	/*
+	  * When we migrate a page to a different zone and adjusted the
+	  * managed page count when inflating, we have to fixup the count of
+	  * both involved zones.
+	  */
+	if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM) &&
+	    page_zone(page) != page_zone(newpage)) {
+		adjust_managed_page_count(page, 1);
+		adjust_managed_page_count(newpage, -1);
+	}
+
 	/* balloon's page migration 1st step  -- inflate "newpage" */
 	spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
-	balloon_page_insert(newpage, mapping, &vb_dev_info->pages);
+	balloon_page_insert(vb_dev_info, newpage);
 	vb_dev_info->isolated_pages--;
+	__count_vm_event(BALLOON_MIGRATE);
 	spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
 	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
-	set_page_pfns(vb->pfns, newpage);
+	set_page_pfns(vb, vb->pfns, newpage);
 	tell_host(vb, vb->inflate_vq);
 
-	/*
-	 * balloon's page migration 2nd step -- deflate "page"
-	 *
-	 * It's safe to delete page->lru here because this page is at
-	 * an isolated migration list, and this step is expected to happen here
-	 */
-	balloon_page_delete(page);
+	/* balloon's page migration 2nd step -- deflate "page" */
 	vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
-	set_page_pfns(vb->pfns, page);
+	set_page_pfns(vb, vb->pfns, page);
 	tell_host(vb, vb->deflate_vq);
 
 	mutex_unlock(&vb->balloon_lock);
 
-	return MIGRATEPAGE_BALLOON_SUCCESS;
-}
+	balloon_page_finalize(page);
+	put_page(page); /* balloon reference */
 
-/* define the balloon_mapping->a_ops callback to allow balloon page migration */
-static const struct address_space_operations virtio_balloon_aops = {
-			.migratepage = virtballoon_migratepage,
-};
+	return 0;
+}
 #endif /* CONFIG_BALLOON_COMPACTION */
 
+static unsigned long shrink_free_pages(struct virtio_balloon *vb,
+				       unsigned long pages_to_free)
+{
+	unsigned long blocks_to_free, blocks_freed;
+
+	pages_to_free = round_up(pages_to_free,
+				 VIRTIO_BALLOON_HINT_BLOCK_PAGES);
+	blocks_to_free = pages_to_free / VIRTIO_BALLOON_HINT_BLOCK_PAGES;
+	blocks_freed = return_free_pages_to_mm(vb, blocks_to_free);
+
+	return blocks_freed * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
+}
+
+static unsigned long virtio_balloon_shrinker_scan(struct shrinker *shrinker,
+						  struct shrink_control *sc)
+{
+	struct virtio_balloon *vb = shrinker->private_data;
+
+	return shrink_free_pages(vb, sc->nr_to_scan);
+}
+
+static unsigned long virtio_balloon_shrinker_count(struct shrinker *shrinker,
+						   struct shrink_control *sc)
+{
+	struct virtio_balloon *vb = shrinker->private_data;
+
+	return vb->num_free_page_blocks * VIRTIO_BALLOON_HINT_BLOCK_PAGES;
+}
+
+static int virtio_balloon_oom_notify(struct notifier_block *nb,
+				     unsigned long dummy, void *parm)
+{
+	struct virtio_balloon *vb = container_of(nb,
+						 struct virtio_balloon, oom_nb);
+	unsigned long *freed = parm;
+
+	*freed += leak_balloon(vb, VIRTIO_BALLOON_OOM_NR_PAGES) /
+		  VIRTIO_BALLOON_PAGES_PER_PAGE;
+	update_balloon_size(vb);
+
+	return NOTIFY_OK;
+}
+
+static void virtio_balloon_unregister_shrinker(struct virtio_balloon *vb)
+{
+	shrinker_free(vb->shrinker);
+}
+
+static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
+{
+	vb->shrinker = shrinker_alloc(0, "virtio-balloon");
+	if (!vb->shrinker)
+		return -ENOMEM;
+
+	vb->shrinker->scan_objects = virtio_balloon_shrinker_scan;
+	vb->shrinker->count_objects = virtio_balloon_shrinker_count;
+	vb->shrinker->private_data = vb;
+
+	shrinker_register(vb->shrinker);
+
+	return 0;
+}
+
 static int virtballoon_probe(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb;
-	struct address_space *vb_mapping;
-	struct balloon_dev_info *vb_devinfo;
 	int err;
 
-	vdev->priv = vb = kmalloc(sizeof(*vb), GFP_KERNEL);
+	if (!vdev->config->get) {
+		dev_err(&vdev->dev, "%s failure: config access disabled\n",
+			__func__);
+		return -EINVAL;
+	}
+
+	vdev->priv = vb = kzalloc(sizeof(*vb), GFP_KERNEL);
 	if (!vb) {
 		err = -ENOMEM;
 		goto out;
 	}
 
-	vb->num_pages = 0;
+	INIT_WORK(&vb->update_balloon_stats_work, update_balloon_stats_func);
+	INIT_WORK(&vb->update_balloon_size_work, update_balloon_size_func);
+	spin_lock_init(&vb->stop_update_lock);
 	mutex_init(&vb->balloon_lock);
-	init_waitqueue_head(&vb->config_change);
 	init_waitqueue_head(&vb->acked);
 	vb->vdev = vdev;
-	vb->need_stats_update = 0;
 
-	vb_devinfo = balloon_devinfo_alloc(vb);
-	if (IS_ERR(vb_devinfo)) {
-		err = PTR_ERR(vb_devinfo);
+	balloon_devinfo_init(&vb->vb_dev_info);
+
+	err = init_vqs(vb);
+	if (err)
 		goto out_free_vb;
+
+#ifdef CONFIG_BALLOON_COMPACTION
+	vb->vb_dev_info.migratepage = virtballoon_migratepage;
+#endif
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+		/*
+		 * There is always one entry reserved for cmd id, so the ring
+		 * size needs to be at least two to report free page hints.
+		 */
+		if (virtqueue_get_vring_size(vb->free_page_vq) < 2) {
+			err = -ENOSPC;
+			goto out_del_vqs;
+		}
+		vb->balloon_wq = alloc_workqueue("balloon-wq",
+					WQ_FREEZABLE | WQ_CPU_INTENSIVE | WQ_PERCPU,
+					0);
+		if (!vb->balloon_wq) {
+			err = -ENOMEM;
+			goto out_del_vqs;
+		}
+		INIT_WORK(&vb->report_free_page_work, report_free_page_func);
+		vb->cmd_id_received_cache = VIRTIO_BALLOON_CMD_ID_STOP;
+		vb->cmd_id_active = cpu_to_virtio32(vb->vdev,
+						  VIRTIO_BALLOON_CMD_ID_STOP);
+		vb->cmd_id_stop = cpu_to_virtio32(vb->vdev,
+						  VIRTIO_BALLOON_CMD_ID_STOP);
+		spin_lock_init(&vb->free_page_list_lock);
+		INIT_LIST_HEAD(&vb->free_page_list);
+		/*
+		 * We're allowed to reuse any free pages, even if they are
+		 * still to be processed by the host.
+		 */
+		err = virtio_balloon_register_shrinker(vb);
+		if (err)
+			goto out_del_balloon_wq;
+	}
+
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) {
+		vb->oom_nb.notifier_call = virtio_balloon_oom_notify;
+		vb->oom_nb.priority = VIRTIO_BALLOON_OOM_NOTIFY_PRIORITY;
+		err = register_oom_notifier(&vb->oom_nb);
+		if (err < 0)
+			goto out_unregister_shrinker;
 	}
 
-	vb_mapping = balloon_mapping_alloc(vb_devinfo,
-					   (balloon_compaction_check()) ?
-					   &virtio_balloon_aops : NULL);
-	if (IS_ERR(vb_mapping)) {
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
+		/* Start with poison val of 0 representing general init */
+		__u32 poison_val = 0;
+
 		/*
-		 * IS_ERR(vb_mapping) && PTR_ERR(vb_mapping) == -EOPNOTSUPP
-		 * This means !CONFIG_BALLOON_COMPACTION, otherwise we get off.
+		 * Let the hypervisor know that we are expecting a
+		 * specific value to be written back in balloon pages.
+		 *
+		 * If the PAGE_POISON value was larger than a byte we would
+		 * need to byte swap poison_val here to guarantee it is
+		 * little-endian. However for now it is a single byte so we
+		 * can pass it as-is.
 		 */
-		err = PTR_ERR(vb_mapping);
-		if (err != -EOPNOTSUPP)
-			goto out_free_vb_devinfo;
+		if (!want_init_on_free())
+			memset(&poison_val, PAGE_POISON, sizeof(poison_val));
+
+		virtio_cwrite_le(vb->vdev, struct virtio_balloon_config,
+				 poison_val, &poison_val);
 	}
 
-	vb->vb_dev_info = vb_devinfo;
+	vb->pr_dev_info.report = virtballoon_free_page_report;
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
+		unsigned int capacity;
 
-	err = init_vqs(vb);
-	if (err)
-		goto out_free_vb_mapping;
+		capacity = virtqueue_get_vring_size(vb->reporting_vq);
+		if (capacity < PAGE_REPORTING_CAPACITY) {
+			err = -ENOSPC;
+			goto out_unregister_oom;
+		}
+
+		/*
+		 * The default page reporting order is @pageblock_order, which
+		 * corresponds to 512MB in size on ARM64 when 64KB base page
+		 * size is used. The page reporting won't be triggered if the
+		 * freeing page can't come up with a free area like that huge.
+		 * So we specify the page reporting order to 5, corresponding
+		 * to 2MB. It helps to avoid THP splitting if 4KB base page
+		 * size is used by host.
+		 *
+		 * Ideally, the page reporting order is selected based on the
+		 * host's base page size. However, it needs more work to report
+		 * that value. The hard-coded order would be fine currently.
+		 */
+#if defined(CONFIG_ARM64) && defined(CONFIG_ARM64_64K_PAGES)
+		vb->pr_dev_info.order = 5;
+#endif
 
-	vb->thread = kthread_run(balloon, vb, "vballoon");
-	if (IS_ERR(vb->thread)) {
-		err = PTR_ERR(vb->thread);
-		goto out_del_vqs;
+		err = page_reporting_register(&vb->pr_dev_info);
+		if (err)
+			goto out_unregister_oom;
 	}
 
+	spin_lock_init(&vb->wakeup_lock);
+
+	/*
+	 * The virtio balloon itself can't wake up the device, but it is
+	 * responsible for processing wakeup events passed up from the transport
+	 * layer. Wakeup sources don't support nesting/chaining calls, so we use
+	 * our own wakeup source to ensure wakeup events are properly handled
+	 * without trampling on the transport layer's wakeup source.
+	 */
+	device_set_wakeup_capable(&vb->vdev->dev, true);
+
+	virtio_device_ready(vdev);
+
+	if (towards_target(vb))
+		virtballoon_changed(vdev);
 	return 0;
 
+out_unregister_oom:
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+		unregister_oom_notifier(&vb->oom_nb);
+out_unregister_shrinker:
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		virtio_balloon_unregister_shrinker(vb);
+out_del_balloon_wq:
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		destroy_workqueue(vb->balloon_wq);
 out_del_vqs:
 	vdev->config->del_vqs(vdev);
-out_free_vb_mapping:
-	balloon_mapping_free(vb_mapping);
-out_free_vb_devinfo:
-	balloon_devinfo_free(vb_devinfo);
 out_free_vb:
 	kfree(vb);
 out:
@@ -496,8 +1107,12 @@ static void remove_common(struct virtio_balloon *vb)
 		leak_balloon(vb, vb->num_pages);
 	update_balloon_size(vb);
 
+	/* There might be free pages that are being reported: release them. */
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		return_free_pages_to_mm(vb, ULONG_MAX);
+
 	/* Now we reset the device so we can clean up the queues. */
-	vb->vdev->config->reset(vb->vdev);
+	virtio_reset_device(vb->vdev);
 
 	vb->vdev->config->del_vqs(vb->vdev);
 }
@@ -506,23 +1121,36 @@ static void virtballoon_remove(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;
 
-	kthread_stop(vb->thread);
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
+		page_reporting_unregister(&vb->pr_dev_info);
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
+		unregister_oom_notifier(&vb->oom_nb);
+	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+		virtio_balloon_unregister_shrinker(vb);
+	spin_lock_irq(&vb->stop_update_lock);
+	vb->stop_update = true;
+	spin_unlock_irq(&vb->stop_update_lock);
+	cancel_work_sync(&vb->update_balloon_size_work);
+	cancel_work_sync(&vb->update_balloon_stats_work);
+
+	if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+		cancel_work_sync(&vb->report_free_page_work);
+		destroy_workqueue(vb->balloon_wq);
+	}
+
 	remove_common(vb);
-	balloon_mapping_free(vb->vb_dev_info->mapping);
-	balloon_devinfo_free(vb->vb_dev_info);
 	kfree(vb);
 }
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 static int virtballoon_freeze(struct virtio_device *vdev)
 {
 	struct virtio_balloon *vb = vdev->priv;
 
 	/*
-	 * The kthread is already frozen by the PM core before this
+	 * The workqueue is already frozen by the PM core before this
 	 * function is called.
 	 */
-
 	remove_common(vb);
 	return 0;
 }
@@ -536,27 +1164,51 @@ static int virtballoon_restore(struct virtio_device *vdev)
 	if (ret)
 		return ret;
 
-	fill_balloon(vb, towards_target(vb));
+	virtio_device_ready(vdev);
+
+	if (towards_target(vb))
+		virtballoon_changed(vdev);
 	update_balloon_size(vb);
 	return 0;
 }
 #endif
 
+static int virtballoon_validate(struct virtio_device *vdev)
+{
+	/*
+	 * Inform the hypervisor that our pages are poisoned or
+	 * initialized. If we cannot do that then we should disable
+	 * page reporting as it could potentially change the contents
+	 * of our free pages.
+	 */
+	if (!want_init_on_free() && !page_poisoning_enabled_static())
+		__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON);
+	else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON))
+		__virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING);
+
+	__virtio_clear_bit(vdev, VIRTIO_F_ACCESS_PLATFORM);
+	return 0;
+}
+
 static unsigned int features[] = {
 	VIRTIO_BALLOON_F_MUST_TELL_HOST,
 	VIRTIO_BALLOON_F_STATS_VQ,
+	VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
+	VIRTIO_BALLOON_F_FREE_PAGE_HINT,
+	VIRTIO_BALLOON_F_PAGE_POISON,
+	VIRTIO_BALLOON_F_REPORTING,
 };
 
 static struct virtio_driver virtio_balloon_driver = {
 	.feature_table = features,
 	.feature_table_size = ARRAY_SIZE(features),
 	.driver.name =	KBUILD_MODNAME,
-	.driver.owner =	THIS_MODULE,
 	.id_table =	id_table,
+	.validate =	virtballoon_validate,
 	.probe =	virtballoon_probe,
 	.remove =	virtballoon_remove,
 	.config_changed = virtballoon_changed,
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 	.freeze	=	virtballoon_freeze,
 	.restore =	virtballoon_restore,
 #endif