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Subject: [PATCH v10 7/7] 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>
---
hw/virtio/virtio-balloon.c | 263 ++++++++++++++++++++++++
include/hw/virtio/virtio-balloon.h | 28 ++-
include/standard-headers/linux/virtio_balloon.h | 5 +
3 files changed, 295 insertions(+), 1 deletion(-)
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 1728e4f..5376f9b 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -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"
@@ -308,6 +309,184 @@ 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_disable_bulk_stage();
+ 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);
@@ -316,6 +495,17 @@ 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_FREE_PAGE_REPORT_STOP_ID);
+ } else if (dev->free_page_report_status == FREE_PAGE_REPORT_S_DONE) {
+ config.free_page_report_cmd_id =
+ cpu_to_le32(VIRTIO_BALLOON_FREE_PAGE_REPORT_DONE_ID);
+ }
+
trace_virtio_balloon_get_config(config.num_pages, config.actual);
memcpy(config_data, &config, sizeof(struct virtio_balloon_config));
}
@@ -376,6 +566,7 @@ 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;
}
@@ -412,6 +603,18 @@ 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,
@@ -422,6 +625,10 @@ 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)
@@ -446,6 +653,29 @@ 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);
}
@@ -454,6 +684,11 @@ 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);
@@ -463,6 +698,10 @@ 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);
@@ -480,6 +719,26 @@ 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)
@@ -508,6 +767,10 @@ 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(),
};
diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h
index e0df352..503349a 100644
--- a/include/hw/virtio/virtio-balloon.h
+++ b/include/hw/virtio/virtio-balloon.h
@@ -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 {
@@ -30,15 +33,38 @@ typedef struct virtio_balloon_stat_modern {
uint64_t val;
} VirtIOBalloonStatModern;
+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;
diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h
index 4dbb7dc..9eee1c6 100644
--- a/include/standard-headers/linux/virtio_balloon.h
+++ b/include/standard-headers/linux/virtio_balloon.h
@@ -34,15 +34,20 @@
#define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */
#define VIRTIO_BALLOON_F_STATS_VQ 1 /* Memory Stats virtqueue */
#define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */
+#define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */
/* Size of a PFN in the balloon interface. */
#define VIRTIO_BALLOON_PFN_SHIFT 12
+#define VIRTIO_BALLOON_FREE_PAGE_REPORT_STOP_ID 0
+#define VIRTIO_BALLOON_FREE_PAGE_REPORT_DONE_ID 1
struct virtio_balloon_config {
/* Number of pages host wants Guest to give up. */
uint32_t num_pages;
/* Number of pages we've actually got in balloon. */
uint32_t actual;
+ /* Free page report command id, readonly by guest */
+ uint32_t free_page_report_cmd_id;
};
#define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */
--
1.8.3.1
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