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vhost-user-blk: support inter-host inflight migration

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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 <dtalexundeer@yandex-team.ru>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Raphael Norwitz <raphael.s.norwitz@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260115081103.655749-6-dtalexundeer@yandex-team.ru>
This commit is contained in:
Alexandr Moshkov
2026-01-15 13:11:09 +05:00
committed by Michael S. Tsirkin
parent 3a80ff0721
commit 3dfd711ea9
3 changed files with 34 additions and 0 deletions
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27
hw/block/vhost-user-blk.c
View File

@@ -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)

1
include/hw/virtio/vhost-user-blk.h
View File

@@ -52,6 +52,7 @@ struct VHostUserBlk {
bool started_vu;
bool skip_get_vring_base_on_force_shutdown;
bool inflight_migration;
};
#endif

6
include/hw/virtio/vhost.h
View File

@@ -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