During inter-host migration, waiting for disk requests to be drained in the vhost-user backend can incur significant downtime.
This can be avoided if QEMU migrates the inflight region in vhost-user-blk. Thus, during the qemu migration, with feature flag the vhost-user back-end can immediately stop vrings, so all in-flight requests will be migrated to another host. Signed-off-by: Alexandr Moshkov <[email protected]> Reviewed-by: Stefan Hajnoczi <[email protected]> --- hw/block/vhost-user-blk.c | 27 +++++++++++++++++++++++++++ include/hw/virtio/vhost-user-blk.h | 1 + include/hw/virtio/vhost.h | 6 ++++++ 3 files changed, 34 insertions(+) diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c index 4d81d2dc34..c151e83677 100644 --- a/hw/block/vhost-user-blk.c +++ b/hw/block/vhost-user-blk.c @@ -353,6 +353,7 @@ static int vhost_user_blk_connect(DeviceState *dev, Error **errp) vhost_dev_set_config_notifier(&s->dev, &blk_ops); s->vhost_user.supports_config = true; + s->vhost_user.supports_inflight_migration = s->inflight_migration; ret = vhost_dev_init(&s->dev, &s->vhost_user, VHOST_BACKEND_TYPE_USER, 0, errp); if (ret < 0) { @@ -568,6 +569,26 @@ static struct vhost_dev *vhost_user_blk_get_vhost(VirtIODevice *vdev) return &s->dev; } +static bool vhost_user_blk_inflight_needed(void *opaque) +{ + struct VHostUserBlk *s = opaque; + + bool inflight_migration = virtio_has_feature(s->dev.protocol_features, + VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT); + + return inflight_migration; +} + +static const VMStateDescription vmstate_vhost_user_blk_inflight = { + .name = "vhost-user-blk/inflight", + .version_id = 1, + .needed = vhost_user_blk_inflight_needed, + .fields = (const VMStateField[]) { + VMSTATE_VHOST_INFLIGHT_REGION(inflight, VHostUserBlk), + VMSTATE_END_OF_LIST() + }, +}; + static const VMStateDescription vmstate_vhost_user_blk = { .name = "vhost-user-blk", .minimum_version_id = 1, @@ -576,6 +597,10 @@ static const VMStateDescription vmstate_vhost_user_blk = { VMSTATE_VIRTIO_DEVICE, VMSTATE_END_OF_LIST() }, + .subsections = (const VMStateDescription * const []) { + &vmstate_vhost_user_blk_inflight, + NULL + } }; static const Property vhost_user_blk_properties[] = { @@ -591,6 +616,8 @@ static const Property vhost_user_blk_properties[] = { VIRTIO_BLK_F_WRITE_ZEROES, true), DEFINE_PROP_BOOL("skip-get-vring-base-on-force-shutdown", VHostUserBlk, skip_get_vring_base_on_force_shutdown, false), + DEFINE_PROP_BOOL("inflight-migration", VHostUserBlk, + inflight_migration, false), }; static void vhost_user_blk_class_init(ObjectClass *klass, const void *data) diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h index 8158d4673d..1e41a2bcdf 100644 --- a/include/hw/virtio/vhost-user-blk.h +++ b/include/hw/virtio/vhost-user-blk.h @@ -52,6 +52,7 @@ struct VHostUserBlk { bool started_vu; bool skip_get_vring_base_on_force_shutdown; + bool inflight_migration; }; #endif diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h index 08bbb4dfe9..89817bd848 100644 --- a/include/hw/virtio/vhost.h +++ b/include/hw/virtio/vhost.h @@ -554,4 +554,10 @@ static inline int vhost_load_backend_state(struct vhost_dev *dev, QEMUFile *f, } #endif +extern const VMStateDescription vmstate_vhost_inflight_region; +#define VMSTATE_VHOST_INFLIGHT_REGION(_field, _state) \ + VMSTATE_STRUCT_POINTER(_field, _state, \ + vmstate_vhost_inflight_region, \ + struct vhost_inflight) + #endif -- 2.34.1
