- 根目录:
- drivers
- virtio
- virtio_balloon.c
/*
* 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/delay.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/balloon_compaction.h>
#include <linux/oom.h>
#include <linux/wait.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
#define OOM_VBALLOON_DEFAULT_PAGES 256
#define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80
static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES;
module_param(oom_pages, int, S_IRUSR | S_IWUSR);
MODULE_PARM_DESC(oom_pages, "pages to free on OOM");
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;
/* The thread servicing the balloon. */
struct task_struct *thread;
/* 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;
u32 pfns[VIRTIO_BALLOON_ARRAY_PFNS_MAX];
/* Memory statistics */
int need_stats_update;
struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
/* To register callback in oom notifier call chain */
struct notifier_block nb;
};
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 struct page *balloon_pfn_to_page(u32 pfn)
{
BUG_ON(pfn % VIRTIO_BALLOON_PAGES_PER_PAGE);
return pfn_to_page(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 void set_page_pfns(u32 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. */
for (i = 0; i < VIRTIO_BALLOON_PAGES_PER_PAGE; i++)
pfns[i] = page_to_balloon_pfn(page) + i;
}
static void fill_balloon(struct virtio_balloon *vb, size_t num)
{
struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info;
/* 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);
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;
}
set_page_pfns(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);
}
/* Did we get any? */
if (vb->num_pfns != 0)
tell_host(vb, vb->inflate_vq);
mutex_unlock(&vb->balloon_lock);
}
static void release_pages_balloon(struct virtio_balloon *vb)
{
unsigned int i;
/* Find pfns pointing at start of each page, get pages and free them. */
for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
struct page *page = balloon_pfn_to_page(vb->pfns[i]);
if (!virtio_has_feature(vb->vdev,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
adjust_managed_page_count(page, 1);
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;
/* 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) {
page = balloon_page_dequeue(vb_dev_info);
if (!page)
break;
set_page_pfns(vb->pfns + vb->num_pfns, page);
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);
mutex_unlock(&vb->balloon_lock);
release_pages_balloon(vb);
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 void update_balloon_stats(struct virtio_balloon *vb)
{
unsigned long events[NR_VM_EVENT_ITEMS];
struct sysinfo i;
int idx = 0;
all_vm_events(events);
si_meminfo(&i);
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]);
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));
}
/*
* 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 notify our kthread which does 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);
}
static void stats_handle_request(struct virtio_balloon *vb)
{
struct virtqueue *vq;
struct scatterlist sg;
unsigned int len;
vb->need_stats_update = 0;
update_balloon_stats(vb);
vq = vb->stats_vq;
if (!virtqueue_get_buf(vq, &len))
return;
sg_init_one(&sg, vb->stats, sizeof(vb->stats));
virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
virtqueue_kick(vq);
}
static void virtballoon_changed(struct virtio_device *vdev)
{
struct virtio_balloon *vb = vdev->priv;
wake_up(&vb->config_change);
}
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;
}
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);
}
/*
* virtballoon_oom_notify - release pages when system is under severe
* memory pressure (called from out_of_memory())
* @self : notifier block struct
* @dummy: not used
* @parm : returned - number of freed pages
*
* The balancing of memory by use of the virtio balloon should not cause
* the termination of processes while there are pages in the balloon.
* If virtio balloon manages to release some memory, it will make the
* system return and retry the allocation that forced the OOM killer
* to run.
*/
static int virtballoon_oom_notify(struct notifier_block *self,
unsigned long dummy, void *parm)
{
struct virtio_balloon *vb;
unsigned long *freed;
unsigned num_freed_pages;
vb = container_of(self, struct virtio_balloon, nb);
if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM))
return NOTIFY_OK;
freed = parm;
num_freed_pages = leak_balloon(vb, oom_pages);
update_balloon_size(vb);
*freed += num_freed_pages;
return NOTIFY_OK;
}
static int balloon(void *_vballoon)
{
struct virtio_balloon *vb = _vballoon;
DEFINE_WAIT_FUNC(wait, woken_wake_function);
set_freezable();
while (!kthread_should_stop()) {
s64 diff;
try_to_freeze();
add_wait_queue(&vb->config_change, &wait);
for (;;) {
if ((diff = towards_target(vb)) != 0 ||
vb->need_stats_update ||
kthread_should_stop() ||
freezing(current))
break;
wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
remove_wait_queue(&vb->config_change, &wait);
if (vb->need_stats_update)
stats_handle_request(vb);
if (diff > 0)
fill_balloon(vb, diff);
else if (diff < 0)
leak_balloon(vb, -diff);
update_balloon_size(vb);
/*
* For large balloon changes, we could spend a lot of time
* and always have work to do. Be nice if preempt disabled.
*/
cond_resched();
}
return 0;
}
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;
/*
* We expect two virtqueues: inflate and deflate, and
* optionally stat.
*/
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);
if (err)
return err;
vb->inflate_vq = vqs[0];
vb->deflate_vq = vqs[1];
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
struct scatterlist sg;
vb->stats_vq = vqs[2];
/*
* Prime this virtqueue with one buffer so the hypervisor can
* 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();
virtqueue_kick(vb->stats_vq);
}
return 0;
}
#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 */
/* 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->pfns, newpage);
tell_host(vb, vb->inflate_vq);
/* balloon's page migration 2nd step -- deflate "page" */
balloon_page_delete(page);
vb->num_pfns = VIRTIO_BALLOON_PAGES_PER_PAGE;
set_page_pfns(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 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 = kmalloc(sizeof(*vb), GFP_KERNEL);
if (!vb) {
err = -ENOMEM;
goto out;
}
vb->num_pages = 0;
mutex_init(&vb->balloon_lock);
init_waitqueue_head(&vb->config_change);
init_waitqueue_head(&vb->acked);
vb->vdev = vdev;
vb->need_stats_update = 0;
balloon_devinfo_init(&vb->vb_dev_info);
#ifdef CONFIG_BALLOON_COMPACTION
vb->vb_dev_info.migratepage = virtballoon_migratepage;
#endif
err = init_vqs(vb);
if (err)
goto out_free_vb;
vb->nb.notifier_call = virtballoon_oom_notify;
vb->nb.priority = VIRTBALLOON_OOM_NOTIFY_PRIORITY;
err = register_oom_notifier(&vb->nb);
if (err < 0)
goto out_oom_notify;
virtio_device_ready(vdev);
vb->thread = kthread_run(balloon, vb, "vballoon");
if (IS_ERR(vb->thread)) {
err = PTR_ERR(vb->thread);
goto out_del_vqs;
}
return 0;
out_del_vqs:
unregister_oom_notifier(&vb->nb);
out_oom_notify:
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);
/* 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;
unregister_oom_notifier(&vb->nb);
kthread_stop(vb->thread);
remove_common(vb);
kfree(vb);
}
#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
* 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);
fill_balloon(vb, towards_target(vb));
update_balloon_size(vb);
return 0;
}
#endif
static unsigned int features[] = {
VIRTIO_BALLOON_F_MUST_TELL_HOST,
VIRTIO_BALLOON_F_STATS_VQ,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM,
};
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,
.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");