From f5b22d06fb0526c9292568dd1fc13b9d1a8b003e Mon Sep 17 00:00:00 2001 From: Dima Stepanov Date: Fri, 11 Sep 2020 11:39:43 +0300 Subject: [PATCH] vhost: recheck dev state in the vhost_migration_log routine 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 ) at softmmu/memory.c:2664 #2 0x000056398603dd30 in memory_listener_register (listener=0x563989cf7be0, as=0x563986ea4340 ) 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 Reviewed-by: Raphael Norwitz Message-Id: <9fbfba06791a87813fcee3e2315f0b904cc6789a.1599813294.git.dimastep@yandex-team.ru> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- 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 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) 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