| Message ID | a35178fe9e90d2552990a6b359a626e0a40d8b17.1598865610.git.dimastep@yandex-team.ru |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v3,1/7] vhost: recheck dev state in the vhost_migration_log routine | expand |
On Mon, Aug 31, 2020 at 5:28 AM Dima Stepanov <dimastep@yandex-team.ru> wrote: > > 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 <dimastep@yandex-team.ru> Reviewed-by: Raphael Norwitz <raphael.norwitz@nutanix.com> > --- > hw/block/vhost-user-blk.c | 19 ++++++++++++++++--- > hw/virtio/vhost.c | 27 ++++++++++++++++++++++++--- > include/hw/virtio/vhost-user-blk.h | 10 ++++++++++ > 3 files changed, 50 insertions(+), 6 deletions(-) > > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c > index 39aec42..a076b1e 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 1a1384e..ffef7ab 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -861,21 +861,42 @@ 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) > diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h > index 292d171..4d6f4c0 100644 > --- a/include/hw/virtio/vhost-user-blk.h > +++ b/include/hw/virtio/vhost-user-blk.h > @@ -40,7 +40,17 @@ typedef 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; > } VHostUserBlk; > > #endif > -- > 2.7.4 > >
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c index 39aec42..a076b1e 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 1a1384e..ffef7ab 100644 --- a/hw/virtio/vhost.c +++ b/hw/virtio/vhost.c @@ -861,21 +861,42 @@ 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) diff --git a/include/hw/virtio/vhost-user-blk.h b/include/hw/virtio/vhost-user-blk.h index 292d171..4d6f4c0 100644 --- a/include/hw/virtio/vhost-user-blk.h +++ b/include/hw/virtio/vhost-user-blk.h @@ -40,7 +40,17 @@ typedef 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; } VHostUserBlk; #endif
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 <dimastep@yandex-team.ru> --- hw/block/vhost-user-blk.c | 19 ++++++++++++++++--- hw/virtio/vhost.c | 27 ++++++++++++++++++++++++--- include/hw/virtio/vhost-user-blk.h | 10 ++++++++++ 3 files changed, 50 insertions(+), 6 deletions(-)