From: Dima Stepanov <dimas...@yandex-team.ru>
vhost-user devices can get a disconnect in the middle of the VHOST-USER
handshake on the migration start. If disconnect event happened right
before sending next VHOST-USER command, then the vhost_dev_set_log()
call in the vhost_migration_log() function will return error. This error
will lead to the assert() and close the QEMU migration source process.
For the vhost-user devices the disconnect event should not break the
migration process, because:
- the device will be in the stopped state, so it will not be changed
during migration
- if reconnect will be made the migration log will be reinitialized as
part of reconnect/init process:
#0 vhost_log_global_start (listener=0x563989cf7be0)
at hw/virtio/vhost.c:920
#1 0x000056398603d8bc in listener_add_address_space
(listener=0x563989cf7be0,
as=0x563986ea4340 <address_space_memory>)
at softmmu/memory.c:2664
#2 0x000056398603dd30 in memory_listener_register (listener=0x563989cf7be0,
as=0x563986ea4340 <address_space_memory>)
at softmmu/memory.c:2740
#3 0x0000563985fd6956 in vhost_dev_init (hdev=0x563989cf7bd8,
opaque=0x563989cf7e30, backend_type=VHOST_BACKEND_TYPE_USER,
busyloop_timeout=0)
at hw/virtio/vhost.c:1385
#4 0x0000563985f7d0b8 in vhost_user_blk_connect (dev=0x563989cf7990)
at hw/block/vhost-user-blk.c:315
#5 0x0000563985f7d3f6 in vhost_user_blk_event (opaque=0x563989cf7990,
event=CHR_EVENT_OPENED)
at hw/block/vhost-user-blk.c:379
Update the vhost-user-blk device with the internal started_vu field which
will be used for initialization (vhost_user_blk_start) and clean up
(vhost_user_blk_stop). This additional flag in the VhostUserBlk structure
will be used to track whether the device really needs to be stopped and
cleaned up on a vhost-user level.
The disconnect event will set the overall VHOST device (not vhost-user) to
the stopped state, so it can be used by the general vhost_migration_log
routine.
Such approach could be propogated to the other vhost-user devices, but
better idea is just to make the same connect/disconnect code for all the
vhost-user devices.
This migration issue was slightly discussed earlier:
- https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg01509.html
- https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg05241.html
Signed-off-by: Dima Stepanov <dimas...@yandex-team.ru>
Reviewed-by: Raphael Norwitz <raphael.norw...@nutanix.com>
Message-Id:
<9fbfba06791a87813fcee3e2315f0b904cc6789a.1599813294.git.dimas...@yandex-team.ru>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
include/hw/virtio/vhost-user-blk.h | 10 ++++++++++
hw/block/vhost-user-blk.c | 19 ++++++++++++++++---
hw/virtio/vhost.c | 27 ++++++++++++++++++++++++---
3 files changed, 50 insertions(+), 6 deletions(-)
diff --git a/include/hw/virtio/vhost-user-blk.h
b/include/hw/virtio/vhost-user-blk.h
index f536576d20..7c91f15040 100644
--- a/include/hw/virtio/vhost-user-blk.h
+++ b/include/hw/virtio/vhost-user-blk.h
@@ -40,7 +40,17 @@ struct VHostUserBlk {
VhostUserState vhost_user;
struct vhost_virtqueue *vhost_vqs;
VirtQueue **virtqs;
+
+ /*
+ * There are at least two steps of initialization of the
+ * vhost-user device. The first is a "connect" step and
+ * second is a "start" step. Make a separation between
+ * those initialization phases by using two fields.
+ */
+ /* vhost_user_blk_connect/vhost_user_blk_disconnect */
bool connected;
+ /* vhost_user_blk_start/vhost_user_blk_stop */
+ bool started_vu;
};
#endif
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 39aec42dae..a076b1e54d 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -150,6 +150,7 @@ static int vhost_user_blk_start(VirtIODevice *vdev)
error_report("Error starting vhost: %d", -ret);
goto err_guest_notifiers;
}
+ s->started_vu = true;
/* guest_notifier_mask/pending not used yet, so just unmask
* everything here. virtio-pci will do the right thing by
@@ -175,6 +176,11 @@ static void vhost_user_blk_stop(VirtIODevice *vdev)
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
int ret;
+ if (!s->started_vu) {
+ return;
+ }
+ s->started_vu = false;
+
if (!k->set_guest_notifiers) {
return;
}
@@ -341,9 +347,7 @@ static void vhost_user_blk_disconnect(DeviceState *dev)
}
s->connected = false;
- if (s->dev.started) {
- vhost_user_blk_stop(vdev);
- }
+ vhost_user_blk_stop(vdev);
vhost_dev_cleanup(&s->dev);
}
@@ -399,6 +403,15 @@ static void vhost_user_blk_event(void *opaque,
QEMUChrEvent event)
NULL, NULL, false);
aio_bh_schedule_oneshot(ctx, vhost_user_blk_chr_closed_bh, opaque);
}
+
+ /*
+ * Move vhost device to the stopped state. The vhost-user device
+ * will be clean up and disconnected in BH. This can be useful in
+ * the vhost migration code. If disconnect was caught there is an
+ * option for the general vhost code to get the dev state without
+ * knowing its type (in this case vhost-user).
+ */
+ s->dev.started = false;
break;
case CHR_EVENT_BREAK:
case CHR_EVENT_MUX_IN:
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 8087f200e9..60bc516003 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -871,21 +871,42 @@ static int vhost_migration_log(MemoryListener *listener,
bool enable)
dev->log_enabled = enable;
return 0;
}
+
+ r = 0;
if (!enable) {
r = vhost_dev_set_log(dev, false);
if (r < 0) {
- return r;
+ goto check_dev_state;
}
vhost_log_put(dev, false);
} else {
vhost_dev_log_resize(dev, vhost_get_log_size(dev));
r = vhost_dev_set_log(dev, true);
if (r < 0) {
- return r;
+ goto check_dev_state;
}
}
+
+check_dev_state:
dev->log_enabled = enable;
- return 0;
+ /*
+ * vhost-user-* devices could change their state during log
+ * initialization due to disconnect. So check dev state after
+ * vhost communication.
+ */
+ if (!dev->started) {
+ /*
+ * Since device is in the stopped state, it is okay for
+ * migration. Return success.
+ */
+ r = 0;
+ }
+ if (r) {
+ /* An error is occured. */
+ dev->log_enabled = false;
+ }
+
+ return r;
}
static void vhost_log_global_start(MemoryListener *listener)
--
MST
