I'm mostly happy with this. A couple comments. On Wed, May 20, 2020 at 11:54 AM Dima Stepanov <dimas...@yandex-team.ru> wrote: > > A socket write during vhost-user communication may trigger a disconnect > event, calling vhost_user_blk_disconnect() and clearing all the > vhost_dev structures holding data that vhost-user functions expect to > remain valid to roll back initialization correctly. Delay the cleanup to > keep vhost_dev structure valid. > There are two possible states to handle: > 1. RUN_STATE_PRELAUNCH: skip bh oneshot call and perform disconnect in > the caller routine. > 2. RUN_STATE_RUNNING: delay by using bh > > BH changes are based on the similar changes for the vhost-user-net > device: > commit e7c83a885f865128ae3cf1946f8cb538b63cbfba > "vhost-user: delay vhost_user_stop" > I'd also give credit to Li Feng here - he sent a similar patch:
https://lists.gnu.org/archive/html/qemu-devel/2020-04/msg02255.html > Signed-off-by: Dima Stepanov <dimas...@yandex-team.ru> > --- > hw/block/vhost-user-blk.c | 49 > +++++++++++++++++++++++++++++++++++++++++------ > 1 file changed, 43 insertions(+), 6 deletions(-) > > diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c > index 9d8c0b3..447fc9c 100644 > --- a/hw/block/vhost-user-blk.c > +++ b/hw/block/vhost-user-blk.c > @@ -337,11 +337,6 @@ static void vhost_user_blk_disconnect(DeviceState *dev) > VirtIODevice *vdev = VIRTIO_DEVICE(dev); > VHostUserBlk *s = VHOST_USER_BLK(vdev); > > - if (!s->connected) { > - return; > - } > - s->connected = false; > - > if (s->dev.started) { > vhost_user_blk_stop(vdev); > } > @@ -349,6 +344,19 @@ static void vhost_user_blk_disconnect(DeviceState *dev) > vhost_dev_cleanup(&s->dev); > } > > +static void vhost_user_blk_event(void *opaque, QEMUChrEvent event); > + > +static void vhost_user_blk_chr_closed_bh(void *opaque) > +{ > + DeviceState *dev = opaque; > + VirtIODevice *vdev = VIRTIO_DEVICE(dev); > + VHostUserBlk *s = VHOST_USER_BLK(vdev); > + > + vhost_user_blk_disconnect(dev); > + qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, vhost_user_blk_event, > + NULL, opaque, NULL, true); > +} > + > static void vhost_user_blk_event(void *opaque, QEMUChrEvent event) > { > DeviceState *dev = opaque; > @@ -363,7 +371,28 @@ static void vhost_user_blk_event(void *opaque, > QEMUChrEvent event) > } > break; > case CHR_EVENT_CLOSED: > - vhost_user_blk_disconnect(dev); > + /* > + * A close event may happen during a read/write, but vhost > + * code assumes the vhost_dev remains setup, so delay the > + * stop & clear. There are two possible paths to hit this > + * disconnect event: > + * 1. When VM is in the RUN_STATE_PRELAUNCH state. The > + * vhost_user_blk_device_realize() is a caller. > + * 2. In tha main loop phase after VM start. > + * > + * For p2 the disconnect event will be delayed. We can't > + * do the same for p1, because we are not running the loop > + * at this moment. So just skip this step and perform > + * disconnect in the caller function. > + */ > + if (s->connected && runstate_is_running()) { > + AioContext *ctx = qemu_get_current_aio_context(); > + > + qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, NULL, NULL, > + NULL, NULL, false); > + aio_bh_schedule_oneshot(ctx, vhost_user_blk_chr_closed_bh, > opaque); > + } > + s->connected = false; > break; > case CHR_EVENT_BREAK: > case CHR_EVENT_MUX_IN: > @@ -428,6 +457,14 @@ reconnect: > > ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg, > sizeof(struct virtio_blk_config)); I find checking s->connected before ret a little confusing. I think we should also enforce a reconnect if s->connected is false. AFIK if s->connected is false, ret must also be less than 0, but to be safe I’d prefer something like: if (ret < 0 || !s->connected) { if (!s->connected) { /* * Perform disconnect before making reconnect. More detailed * comment why it was delayed is in the vhost_user_blk_event() * routine. */ vhost_user_blk_disconnect(dev); } if (ret < 0) { error_report(“vhost-user-blk: get block config failed”); } goto reconnect; } > + if (!s->connected) { > + /* > + * Perform disconnect before making reconnect. More detailed > + * comment why it was delayed is in the vhost_user_blk_event() > + * routine. > + */ > + vhost_user_blk_disconnect(dev); > + } > if (ret < 0) { > error_report("vhost-user-blk: get block config failed"); > goto reconnect; > -- > 2.7.4 > >
