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, the vhost-user backend can cancel all inflight requests and then, after migration, they will be executed on another host. In vhost_user_blk_stop() on incoming inter-host migration make should_drain = true, so after GET_VRING_BASE message all in-flight requests will be migrated to other vm Signed-off-by: Alexandr Moshkov <[email protected]> --- hw/block/vhost-user-blk.c | 25 +++++++++++++++++++++++++ include/hw/virtio/vhost-user-blk.h | 1 + 2 files changed, 26 insertions(+) diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c index 56d55c18c8..c537e7ef9b 100644 --- a/hw/block/vhost-user-blk.c +++ b/hw/block/vhost-user-blk.c @@ -242,6 +242,7 @@ static int vhost_user_blk_stop(VirtIODevice *vdev) force_stop = s->skip_get_vring_base_on_force_shutdown && qemu_force_shutdown_requested(); + should_drain = !s->inflight_migration; s->dev.backend_transfer = s->dev.backend_transfer || (runstate_check(RUN_STATE_FINISH_MIGRATE) && @@ -657,6 +658,24 @@ 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; + + return s->inflight_migration && + !migrate_local_vhost_user_blk(); +} + +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 bool vhost_user_blk_pre_incoming(void *opaque, Error **errp) { VHostUserBlk *s = VHOST_USER_BLK(opaque); @@ -679,6 +698,10 @@ 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 bool vhost_user_needed(void *opaque) @@ -752,6 +775,8 @@ 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 b06f55fd6f..e1466e5cf6 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; bool incoming_backend; }; -- 2.34.1
