linux/drivers/virtio/virtio_balloon.c
Alexander Duyck fb69c2c896 virtio-balloon: Disable free page reporting if page poison reporting is not enabled
We should disable free page reporting if page poisoning is enabled but we
cannot report it via the balloon interface. This way we can avoid the
possibility of corrupting guest memory. Normally the page poisoning feature
should always be present when free page reporting is enabled on the
hypervisor, however this allows us to correctly handle a case of the
virtio-balloon device being possibly misconfigured.

Fixes: 5d757c8d518d ("virtio-balloon: add support for providing free page reports to host")
Cc: stable@vger.kernel.org
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Link: https://lore.kernel.org/r/20200508173732.17877.85060.stgit@localhost.localdomain
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-06-04 15:36:51 -04:00

1156 lines
33 KiB
C

// 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/mount.h>
#include <linux/magic.h>
#include <linux/pseudo_fs.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_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 - 1)
/* 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)
#ifdef CONFIG_BALLOON_COMPACTION
static struct vfsmount *balloon_mnt;
#endif
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 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 fill_balloon(struct virtio_balloon *vb, size_t num)
{
unsigned num_allocated_pages;
unsigned 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 leak_balloon(struct virtio_balloon *vb, size_t num)
{
unsigned 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;
virtio_cread(vb->vdev, struct virtio_balloon_config, num_pages,
&num_pages);
/* Legacy balloon config space is LE, unlike all other devices. */
if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
num_pages = le32_to_cpu((__force __le32)num_pages);
target = num_pages;
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. */
if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1))
actual = (__force u32)cpu_to_le32(actual);
virtio_cwrite(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 = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX,
vqs, callbacks, names, NULL, 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))
virtio_cread(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 = virtio32_to_cpu(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 compation 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;
}
static int balloon_init_fs_context(struct fs_context *fc)
{
return init_pseudo(fc, BALLOON_KVM_MAGIC) ? 0 : -ENOMEM;
}
static struct file_system_type balloon_fs = {
.name = "balloon-kvm",
.init_fs_context = balloon_init_fs_context,
.kill_sb = kill_anon_super,
};
#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);
}
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
balloon_mnt = kern_mount(&balloon_fs);
if (IS_ERR(balloon_mnt)) {
err = PTR_ERR(balloon_mnt);
goto out_del_vqs;
}
vb->vb_dev_info.migratepage = virtballoon_migratepage;
vb->vb_dev_info.inode = alloc_anon_inode(balloon_mnt->mnt_sb);
if (IS_ERR(vb->vb_dev_info.inode)) {
err = PTR_ERR(vb->vb_dev_info.inode);
goto out_kern_unmount;
}
vb->vb_dev_info.inode->i_mapping->a_ops = &balloon_aops;
#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_iput;
}
vb->balloon_wq = alloc_workqueue("balloon-wq",
WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
if (!vb->balloon_wq) {
err = -ENOMEM;
goto out_iput;
}
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 (!want_init_on_free())
memset(&poison_val, PAGE_POISON, sizeof(poison_val));
virtio_cwrite(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;
}
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_iput:
#ifdef CONFIG_BALLOON_COMPACTION
iput(vb->vb_dev_info.inode);
out_kern_unmount:
kern_unmount(balloon_mnt);
out_del_vqs:
#endif
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. */
vb->vdev->config->reset(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);
#ifdef CONFIG_BALLOON_COMPACTION
if (vb->vb_dev_info.inode)
iput(vb->vb_dev_info.inode);
kern_unmount(balloon_mnt);
#endif
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() &&
(IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) ||
!page_poisoning_enabled()))
__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_IOMMU_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");