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virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT 

The new feature enables the virtio-balloon device to receive hints of
guest free pages from the free page vq.

A notifier is registered to the migration precopy notifier chain. The
notifier calls free_page_start after the migration thread syncs the dirty
bitmap, so that the free page optimization starts to clear bits of free
pages from the bitmap. It calls the free_page_stop before the migration
thread syncs the bitmap, which is the end of the current round of ram
save. The free_page_stop is also called to stop the optimization in the
case when there is an error occurred in the process of ram saving.

Note: balloon will report pages which were free at the time of this call.
As the reporting happens asynchronously, dirty bit logging must be
enabled before this free_page_start call is made. Guest reporting must be
disabled before the migration dirty bitmap is synchronized.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
CC: Michael S. Tsirkin <mst@redhat.com>
CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Peter Xu <peterx@redhat.com>
Message-Id: <1544516693-5395-8-git-send-email-wei.w.wang@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
  dgilbert: Dropped kernel header update, fixed up CMD_ID_* name change
This commit is contained in:
Wei Wang 2018-12-11 16:24:53 +08:00 committed by Dr. David Alan Gilbert
parent 6eeb63f740
commit c13c4153f7
2 changed files with 290 additions and 1 deletions
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263
hw/virtio/virtio-balloon.c
View File

@ -27,6 +27,7 @@
#include "qapi/visitor.h"
#include "trace.h"
#include "qemu/error-report.h"
#include "migration/misc.h"
#include "hw/virtio/virtio-bus.h"
#include "hw/virtio/virtio-access.h"
@ -378,6 +379,184 @@ out:
}
}
static void virtio_balloon_handle_free_page_vq(VirtIODevice *vdev,
VirtQueue *vq)
{
VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
qemu_bh_schedule(s->free_page_bh);
}
static bool get_free_page_hints(VirtIOBalloon *dev)
{
VirtQueueElement *elem;
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtQueue *vq = dev->free_page_vq;
while (dev->block_iothread) {
qemu_cond_wait(&dev->free_page_cond, &dev->free_page_lock);
}
elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
if (!elem) {
return false;
}
if (elem->out_num) {
uint32_t id;
size_t size = iov_to_buf(elem->out_sg, elem->out_num, 0,
&id, sizeof(id));
virtqueue_push(vq, elem, size);
g_free(elem);
virtio_tswap32s(vdev, &id);
if (unlikely(size != sizeof(id))) {
virtio_error(vdev, "received an incorrect cmd id");
return false;
}
if (id == dev->free_page_report_cmd_id) {
dev->free_page_report_status = FREE_PAGE_REPORT_S_START;
} else {
/*
* Stop the optimization only when it has started. This
* avoids a stale stop sign for the previous command.
*/
if (dev->free_page_report_status == FREE_PAGE_REPORT_S_START) {
dev->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
}
}
}
if (elem->in_num) {
if (dev->free_page_report_status == FREE_PAGE_REPORT_S_START) {
qemu_guest_free_page_hint(elem->in_sg[0].iov_base,
elem->in_sg[0].iov_len);
}
virtqueue_push(vq, elem, 1);
g_free(elem);
}
return true;
}
static void virtio_ballloon_get_free_page_hints(void *opaque)
{
VirtIOBalloon *dev = opaque;
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtQueue *vq = dev->free_page_vq;
bool continue_to_get_hints;
do {
qemu_mutex_lock(&dev->free_page_lock);
virtio_queue_set_notification(vq, 0);
continue_to_get_hints = get_free_page_hints(dev);
qemu_mutex_unlock(&dev->free_page_lock);
virtio_notify(vdev, vq);
/*
* Start to poll the vq once the reporting started. Otherwise, continue
* only when there are entries on the vq, which need to be given back.
*/
} while (continue_to_get_hints ||
dev->free_page_report_status == FREE_PAGE_REPORT_S_START);
virtio_queue_set_notification(vq, 1);
}
static bool virtio_balloon_free_page_support(void *opaque)
{
VirtIOBalloon *s = opaque;
VirtIODevice *vdev = VIRTIO_DEVICE(s);
return virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT);
}
static void virtio_balloon_free_page_start(VirtIOBalloon *s)
{
VirtIODevice *vdev = VIRTIO_DEVICE(s);
/* For the stop and copy phase, we don't need to start the optimization */
if (!vdev->vm_running) {
return;
}
if (s->free_page_report_cmd_id == UINT_MAX) {
s->free_page_report_cmd_id =
VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
} else {
s->free_page_report_cmd_id++;
}
s->free_page_report_status = FREE_PAGE_REPORT_S_REQUESTED;
virtio_notify_config(vdev);
}
static void virtio_balloon_free_page_stop(VirtIOBalloon *s)
{
VirtIODevice *vdev = VIRTIO_DEVICE(s);
if (s->free_page_report_status != FREE_PAGE_REPORT_S_STOP) {
/*
* The lock also guarantees us that the
* virtio_ballloon_get_free_page_hints exits after the
* free_page_report_status is set to S_STOP.
*/
qemu_mutex_lock(&s->free_page_lock);
/*
* The guest hasn't done the reporting, so host sends a notification
* to the guest to actively stop the reporting.
*/
s->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
qemu_mutex_unlock(&s->free_page_lock);
virtio_notify_config(vdev);
}
}
static void virtio_balloon_free_page_done(VirtIOBalloon *s)
{
VirtIODevice *vdev = VIRTIO_DEVICE(s);
s->free_page_report_status = FREE_PAGE_REPORT_S_DONE;
virtio_notify_config(vdev);
}
static int
virtio_balloon_free_page_report_notify(NotifierWithReturn *n, void *data)
{
VirtIOBalloon *dev = container_of(n, VirtIOBalloon,
free_page_report_notify);
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
PrecopyNotifyData *pnd = data;
if (!virtio_balloon_free_page_support(dev)) {
/*
* This is an optimization provided to migration, so just return 0 to
* have the normal migration process not affected when this feature is
* not supported.
*/
return 0;
}
switch (pnd->reason) {
case PRECOPY_NOTIFY_SETUP:
precopy_enable_free_page_optimization();
break;
case PRECOPY_NOTIFY_COMPLETE:
case PRECOPY_NOTIFY_CLEANUP:
case PRECOPY_NOTIFY_BEFORE_BITMAP_SYNC:
virtio_balloon_free_page_stop(dev);
break;
case PRECOPY_NOTIFY_AFTER_BITMAP_SYNC:
if (vdev->vm_running) {
virtio_balloon_free_page_start(dev);
} else {
virtio_balloon_free_page_done(dev);
}
break;
default:
virtio_error(vdev, "%s: %d reason unknown", __func__, pnd->reason);
}
return 0;
}
static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
{
VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
@ -386,6 +565,17 @@ static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
config.num_pages = cpu_to_le32(dev->num_pages);
config.actual = cpu_to_le32(dev->actual);
if (dev->free_page_report_status == FREE_PAGE_REPORT_S_REQUESTED) {
config.free_page_report_cmd_id =
cpu_to_le32(dev->free_page_report_cmd_id);
} else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_STOP) {
config.free_page_report_cmd_id =
cpu_to_le32(VIRTIO_BALLOON_CMD_ID_STOP);
} else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_DONE) {
config.free_page_report_cmd_id =
cpu_to_le32(VIRTIO_BALLOON_CMD_ID_DONE);
}
trace_virtio_balloon_get_config(config.num_pages, config.actual);
memcpy(config_data, &config, sizeof(struct virtio_balloon_config));
}
@ -446,6 +636,7 @@ static uint64_t virtio_balloon_get_features(VirtIODevice *vdev, uint64_t f,
VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
f |= dev->host_features;
virtio_add_feature(&f, VIRTIO_BALLOON_F_STATS_VQ);
return f;
}
@ -482,6 +673,18 @@ static int virtio_balloon_post_load_device(void *opaque, int version_id)
return 0;
}
static const VMStateDescription vmstate_virtio_balloon_free_page_report = {
.name = "virtio-balloon-device/free-page-report",
.version_id = 1,
.minimum_version_id = 1,
.needed = virtio_balloon_free_page_support,
.fields = (VMStateField[]) {
VMSTATE_UINT32(free_page_report_cmd_id, VirtIOBalloon),
VMSTATE_UINT32(free_page_report_status, VirtIOBalloon),
VMSTATE_END_OF_LIST()
}
};
static const VMStateDescription vmstate_virtio_balloon_device = {
.name = "virtio-balloon-device",
.version_id = 1,
@ -492,6 +695,10 @@ static const VMStateDescription vmstate_virtio_balloon_device = {
VMSTATE_UINT32(actual, VirtIOBalloon),
VMSTATE_END_OF_LIST()
},
.subsections = (const VMStateDescription * []) {
&vmstate_virtio_balloon_free_page_report,
NULL
}
};
static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
@ -516,6 +723,29 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp)
s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output);
s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats);
if (virtio_has_feature(s->host_features,
VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
s->free_page_vq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,
virtio_balloon_handle_free_page_vq);
s->free_page_report_status = FREE_PAGE_REPORT_S_STOP;
s->free_page_report_cmd_id =
VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN;
s->free_page_report_notify.notify =
virtio_balloon_free_page_report_notify;
precopy_add_notifier(&s->free_page_report_notify);
if (s->iothread) {
object_ref(OBJECT(s->iothread));
s->free_page_bh = aio_bh_new(iothread_get_aio_context(s->iothread),
virtio_ballloon_get_free_page_hints, s);
qemu_mutex_init(&s->free_page_lock);
qemu_cond_init(&s->free_page_cond);
s->block_iothread = false;
} else {
/* Simply disable this feature if the iothread wasn't created. */
s->host_features &= ~(1 << VIRTIO_BALLOON_F_FREE_PAGE_HINT);
virtio_error(vdev, "iothread is missing");
}
}
reset_stats(s);
}
@ -524,6 +754,11 @@ static void virtio_balloon_device_unrealize(DeviceState *dev, Error **errp)
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
VirtIOBalloon *s = VIRTIO_BALLOON(dev);
if (virtio_balloon_free_page_support(s)) {
qemu_bh_delete(s->free_page_bh);
virtio_balloon_free_page_stop(s);
precopy_remove_notifier(&s->free_page_report_notify);
}
balloon_stats_destroy_timer(s);
qemu_remove_balloon_handler(s);
virtio_cleanup(vdev);
@ -533,6 +768,10 @@ static void virtio_balloon_device_reset(VirtIODevice *vdev)
{
VirtIOBalloon *s = VIRTIO_BALLOON(vdev);
if (virtio_balloon_free_page_support(s)) {
virtio_balloon_free_page_stop(s);
}
if (s->stats_vq_elem != NULL) {
virtqueue_unpop(s->svq, s->stats_vq_elem, 0);
g_free(s->stats_vq_elem);
@ -550,6 +789,26 @@ static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t status)
* was stopped */
virtio_balloon_receive_stats(vdev, s->svq);
}
if (virtio_balloon_free_page_support(s)) {
/*
* The VM is woken up and the iothread was blocked, so signal it to
* continue.
*/
if (vdev->vm_running && s->block_iothread) {
qemu_mutex_lock(&s->free_page_lock);
s->block_iothread = false;
qemu_cond_signal(&s->free_page_cond);
qemu_mutex_unlock(&s->free_page_lock);
}
/* The VM is stopped, block the iothread. */
if (!vdev->vm_running) {
qemu_mutex_lock(&s->free_page_lock);
s->block_iothread = true;
qemu_mutex_unlock(&s->free_page_lock);
}
}
}
static void virtio_balloon_instance_init(Object *obj)
@ -578,6 +837,10 @@ static const VMStateDescription vmstate_virtio_balloon = {
static Property virtio_balloon_properties[] = {
DEFINE_PROP_BIT("deflate-on-oom", VirtIOBalloon, host_features,
VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false),
DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features,
VIRTIO_BALLOON_F_FREE_PAGE_HINT, false),
DEFINE_PROP_LINK("iothread", VirtIOBalloon, iothread, TYPE_IOTHREAD,
IOThread *),
DEFINE_PROP_END_OF_LIST(),
};

28
include/hw/virtio/virtio-balloon.h
View File

@ -17,11 +17,14 @@
#include "standard-headers/linux/virtio_balloon.h"
#include "hw/virtio/virtio.h"
#include "sysemu/iothread.h"
#define TYPE_VIRTIO_BALLOON "virtio-balloon-device"
#define VIRTIO_BALLOON(obj) \
OBJECT_CHECK(VirtIOBalloon, (obj), TYPE_VIRTIO_BALLOON)
#define VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN 0x80000000
typedef struct virtio_balloon_stat VirtIOBalloonStat;
typedef struct virtio_balloon_stat_modern {
@ -32,15 +35,38 @@ typedef struct virtio_balloon_stat_modern {
typedef struct PartiallyBalloonedPage PartiallyBalloonedPage;
enum virtio_balloon_free_page_report_status {
FREE_PAGE_REPORT_S_STOP = 0,
FREE_PAGE_REPORT_S_REQUESTED = 1,
FREE_PAGE_REPORT_S_START = 2,
FREE_PAGE_REPORT_S_DONE = 3,
};
typedef struct VirtIOBalloon {
VirtIODevice parent_obj;
VirtQueue *ivq, *dvq, *svq;
VirtQueue *ivq, *dvq, *svq, *free_page_vq;
uint32_t free_page_report_status;
uint32_t num_pages;
uint32_t actual;
uint32_t free_page_report_cmd_id;
uint64_t stats[VIRTIO_BALLOON_S_NR];
VirtQueueElement *stats_vq_elem;
size_t stats_vq_offset;
QEMUTimer *stats_timer;
IOThread *iothread;
QEMUBH *free_page_bh;
/*
* Lock to synchronize threads to access the free page reporting related
* fields (e.g. free_page_report_status).
*/
QemuMutex free_page_lock;
QemuCond free_page_cond;
/*
* Set to block iothread to continue reading free page hints as the VM is
* stopped.
*/
bool block_iothread;
NotifierWithReturn free_page_report_notify;
int64_t stats_last_update;
int64_t stats_poll_interval;
uint32_t host_features;