On Thu, Aug 27, 2020 at 09:44:22PM -0400, Raphael Norwitz wrote: > Generally I’m happy with this. Some comments: > > On Mon, Aug 24, 2020 at 4:40 AM Dima Stepanov <dimas...@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 field which > > will be used for initialization and clean up. The disconnect event will > > set the overall VHOST device to the stopped state, so it can be used by > > the 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 > > > > What you’re doing here on a structural level is adding an additional > flag “started” to VhostUserBlk to track whether the device really > needs to be stopped and cleaned up on a vhost level on a disconnect. > Can you make that more clear in the commit message as you have in the > comments? Sounds reasonable, will update the commit message.
> > > > Signed-off-by: Dima Stepanov <dimas...@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(-) > > > > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c > > index a00b854..5573e89 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 = 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) { > > + return; > > + } > > + s->started = 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 34ad6f0..f4c0754 100644 > > --- a/include/hw/virtio/vhost-user-blk.h > > +++ b/include/hw/virtio/vhost-user-blk.h > > @@ -38,7 +38,17 @@ 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 */ > > I don’t like the name “started” for the vhost-user-blk flag because > it’s easy to get confused with the vhost_dev "started" field, and they > are used for very different things. Maybe call it “needs_cleanup” or > “started_internal”, or something to that effect? Good point. In this case i like the "started_internal" or "started_vu" just to show that it is only vhost-user start/stop routine flag. No other comments mixed in below. > > > > + bool started; > > } VHostUserBlk; > > > > #endif > > -- > > 2.7.4 > > > >