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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /drivers/virtio/virtio_balloon.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/virtio/virtio_balloon.c')
-rw-r--r--drivers/virtio/virtio_balloon.c1132
1 files changed, 1132 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
new file mode 100644
index 0000000000..2d5d252ef4
--- /dev/null
+++ b/drivers/virtio/virtio_balloon.c
@@ -0,0 +1,1132 @@
+// 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
+ */
+
+#include <linux/virtio.h>
+#include <linux/virtio_balloon.h>
+#include <linux/swap.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 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_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
+};
+
+enum virtio_balloon_config_read {
+ VIRTIO_BALLOON_CONFIG_READ_CMD_ID = 0,
+};
+
+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;
+
+ /* Number of balloon pages we've told the Host we're not using. */
+ unsigned int num_pages;
+ /*
+ * The pages we've told the Host we're not using are enqueued
+ * at vb_dev_info->pages list.
+ * Each page on this list adds VIRTIO_BALLOON_PAGES_PER_PAGE
+ * to num_pages above.
+ */
+ 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;
+ __virtio32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
+
+ /* Memory statistics */
+ 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;
+};
+
+static const struct virtio_device_id id_table[] = {
+ { VIRTIO_ID_BALLOON, VIRTIO_DEV_ANY_ID },
+ { 0 },
+};
+
+static u32 page_to_balloon_pfn(struct page *page)
+{
+ unsigned long pfn = page_to_pfn(page);
+
+ BUILD_BUG_ON(PAGE_SHIFT < VIRTIO_BALLOON_PFN_SHIFT);
+ /* Convert pfn from Linux page size to balloon page size. */
+ return pfn * VIRTIO_BALLOON_PAGES_PER_PAGE;
+}
+
+static void balloon_ack(struct virtqueue *vq)
+{
+ struct virtio_balloon *vb = vq->vdev->priv;
+
+ wake_up(&vb->acked);
+}
+
+static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
+{
+ struct scatterlist sg;
+ unsigned int len;
+
+ 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. */
+ 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 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 | __GFP_NOWARN);
+
+ /*
+ * 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;
+
+ 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] = cpu_to_virtio32(vb->vdev,
+ page_to_balloon_pfn(page) + i);
+}
+
+static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num)
+{
+ 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));
+
+ for (num_pfns = 0; num_pfns < num;
+ num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) {
+ struct page *page = balloon_page_alloc();
+
+ if (!page) {
+ dev_info_ratelimited(&vb->vdev->dev,
+ "Out of puff! Can't get %u pages\n",
+ VIRTIO_BALLOON_PAGES_PER_PAGE);
+ /* Sleep for at least 1/5 of a second before retry. */
+ msleep(200);
+ break;
+ }
+
+ 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;
+ 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_balloon(struct virtio_balloon *vb,
+ struct list_head *pages)
+{
+ 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 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;
+ 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, 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);
+ * is true, we *have* to do it in this order
+ */
+ if (vb->num_pfns != 0)
+ tell_host(vb, vb->deflate_vq);
+ release_pages_balloon(vb, &pages);
+ mutex_unlock(&vb->balloon_lock);
+ 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 = 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 unsigned int update_balloon_stats(struct virtio_balloon *vb)
+{
+ unsigned long events[NR_VM_EVENT_ITEMS];
+ struct sysinfo i;
+ unsigned int idx = 0;
+ long available;
+ unsigned long caches;
+
+ all_vm_events(events);
+ si_meminfo(&i);
+
+ available = si_mem_available();
+ caches = global_node_page_state(NR_FILE_PAGES);
+
+#ifdef CONFIG_VM_EVENT_COUNTERS
+ update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_IN,
+ pages_to_bytes(events[PSWPIN]));
+ update_stat(vb, idx++, VIRTIO_BALLOON_S_SWAP_OUT,
+ 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]);
+#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
+#endif
+ 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;
+}
+
+/*
+ * While most virtqueues communicate guest-initiated requests to the hypervisor,
+ * the stats queue operates in reverse. The driver initializes the virtqueue
+ * 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 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;
+
+ spin_lock(&vb->stop_update_lock);
+ if (!vb->stop_update)
+ 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, num_stats;
+
+ 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[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((unsigned long)page_address(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 virtballoon_changed(struct virtio_device *vdev)
+{
+ struct virtio_balloon *vb = vdev->priv;
+ unsigned long flags;
+
+ spin_lock_irqsave(&vb->stop_update_lock, flags);
+ if (!vb->stop_update) {
+ queue_work(system_freezable_wq,
+ &vb->update_balloon_size_work);
+ virtio_balloon_queue_free_page_work(vb);
+ }
+ spin_unlock_irqrestore(&vb->stop_update_lock, flags);
+}
+
+static void update_balloon_size(struct virtio_balloon *vb)
+{
+ u32 actual = 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_stats_func(struct work_struct *work)
+{
+ struct virtio_balloon *vb;
+
+ vb = container_of(work, struct virtio_balloon,
+ update_balloon_stats_work);
+ stats_handle_request(vb);
+}
+
+static void update_balloon_size_func(struct work_struct *work)
+{
+ struct virtio_balloon *vb;
+ s64 diff;
+
+ vb = container_of(work, struct virtio_balloon,
+ update_balloon_size_work);
+ diff = towards_target(vb);
+
+ if (!diff)
+ return;
+
+ if (diff > 0)
+ diff -= fill_balloon(vb, diff);
+ else
+ diff += leak_balloon(vb, -diff);
+ update_balloon_size(vb);
+
+ if (diff)
+ queue_work(system_freezable_wq, work);
+}
+
+static int init_vqs(struct virtio_balloon *vb)
+{
+ struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
+ vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
+ const char *names[VIRTIO_BALLOON_VQ_MAX];
+ int err;
+
+ /*
+ * 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.
+ */
+ callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
+ names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
+ callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
+ names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
+ callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
+ names[VIRTIO_BALLOON_VQ_STATS] = NULL;
+ callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
+ names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
+ names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
+
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
+ names[VIRTIO_BALLOON_VQ_STATS] = "stats";
+ callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
+ }
+
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
+ names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
+ callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
+ }
+
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
+ names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
+ callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
+ }
+
+ err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
+ callbacks, names, NULL);
+ if (err)
+ return err;
+
+ 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;
+ 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 (it can't be broken yet!).
+ */
+ 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((unsigned long)p,
+ 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((unsigned long)p, VIRTIO_BALLOON_HINT_BLOCK_ORDER);
+ }
+
+ return 0;
+}
+
+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 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.
+ *
+ * After a ballooned page gets isolated by compaction procedures, this is the
+ * function that performs the page migration on behalf of a compaction thread
+ * The page migration for virtio balloon is done in a simple swap fashion which
+ * follows these two macro steps:
+ * 1) insert newpage into vb->pages list and update the host about it;
+ * 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
+ */
+static int virtballoon_migratepage(struct balloon_dev_info *vb_dev_info,
+ struct page *newpage, struct page *page, enum migrate_mode mode)
+{
+ struct virtio_balloon *vb = container_of(vb_dev_info,
+ struct virtio_balloon, vb_dev_info);
+ unsigned long flags;
+
+ /*
+ * In order to avoid lock contention while migrating pages concurrently
+ * to leak_balloon() or fill_balloon() we just give up the balloon_lock
+ * this turn, as it is easier to retry the page migration later.
+ * This also prevents fill_balloon() getting stuck into a mutex
+ * recursion in the case it ends up triggering memory compaction
+ * while it is attempting to inflate the ballon.
+ */
+ 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(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, vb->pfns, newpage);
+ tell_host(vb, vb->inflate_vq);
+
+ /* balloon's page migration 2nd step -- deflate "page" */
+ spin_lock_irqsave(&vb_dev_info->pages_lock, flags);
+ balloon_page_delete(page);
+ spin_unlock_irqrestore(&vb_dev_info->pages_lock, flags);
+ vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
+ set_page_pfns(vb, vb->pfns, page);
+ tell_host(vb, vb->deflate_vq);
+
+ mutex_unlock(&vb->balloon_lock);
+
+ put_page(page); /* balloon reference */
+
+ return MIGRATEPAGE_SUCCESS;
+}
+#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 = container_of(shrinker,
+ struct virtio_balloon, shrinker);
+
+ 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 = container_of(shrinker,
+ struct virtio_balloon, shrinker);
+
+ 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)
+{
+ unregister_shrinker(&vb->shrinker);
+}
+
+static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
+{
+ vb->shrinker.scan_objects = virtio_balloon_shrinker_scan;
+ vb->shrinker.count_objects = virtio_balloon_shrinker_count;
+ vb->shrinker.seeks = DEFAULT_SEEKS;
+
+ return register_shrinker(&vb->shrinker, "virtio-balloon");
+}
+
+static int virtballoon_probe(struct virtio_device *vdev)
+{
+ struct virtio_balloon *vb;
+ int err;
+
+ 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;
+ }
+
+ 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->acked);
+ vb->vdev = vdev;
+
+ 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, 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;
+ }
+
+ if (virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) {
+ /* Start with poison val of 0 representing general init */
+ __u32 poison_val = 0;
+
+ /*
+ * 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.
+ */
+ 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->pr_dev_info.report = virtballoon_free_page_report;
+ if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
+ unsigned int capacity;
+
+ 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
+
+ err = page_reporting_register(&vb->pr_dev_info);
+ if (err)
+ goto out_unregister_oom;
+ }
+
+ 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:
+ kfree(vb);
+out:
+ return err;
+}
+
+static void remove_common(struct virtio_balloon *vb)
+{
+ /* There might be pages left in the balloon: free them. */
+ while (vb->num_pages)
+ 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. */
+ virtio_reset_device(vb->vdev);
+
+ vb->vdev->config->del_vqs(vb->vdev);
+}
+
+static void virtballoon_remove(struct virtio_device *vdev)
+{
+ struct virtio_balloon *vb = vdev->priv;
+
+ 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);
+ kfree(vb);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int virtballoon_freeze(struct virtio_device *vdev)
+{
+ struct virtio_balloon *vb = vdev->priv;
+
+ /*
+ * The workqueue is already frozen by the PM core before this
+ * function is called.
+ */
+ remove_common(vb);
+ return 0;
+}
+
+static int virtballoon_restore(struct virtio_device *vdev)
+{
+ struct virtio_balloon *vb = vdev->priv;
+ int ret;
+
+ ret = init_vqs(vdev->priv);
+ if (ret)
+ return ret;
+
+ 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_SLEEP
+ .freeze = virtballoon_freeze,
+ .restore = virtballoon_restore,
+#endif
+};
+
+module_virtio_driver(virtio_balloon_driver);
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio balloon driver");
+MODULE_LICENSE("GPL");