On Mon, Apr 01, 2024 at 10:08:10AM +0800, Yajun Wu wrote: > > On 3/27/2024 6:47 PM, Stefano Garzarella wrote: > > External email: Use caution opening links or attachments > > > > > > Hi Yajun, > > > > On Mon, Mar 25, 2024 at 10:54:13AM +0000, Yajun Wu wrote: > > > Hi experts, > > > > > > With latest QEMU (8.2.90), we find two vhost-user-blk backend reconnect > > > failure scenarios: > > Do you know if has it ever worked and so it's a regression, or have we > > always had this problem? > > I am afraid this commit: "71e076a07d (2022-12-01 02:30:13 -0500) hw/virtio: > generalise CHR_EVENT_CLOSED handling" caused both failures. Previous hash > is good.
CC Alex who wrote that commit. > I suspect the "if (vhost->vdev)" in vhost_user_async_close_bh is the cause, > previous code doesn't have this check? > > > > > Thanks, > > Stefano > > > > > 1. Disconnect vhost-user-blk backend before guest driver probe vblk > > > device, then reconnect backend after guest driver probe device. QEMU > > > won't send out any vhost messages to restore backend. > > > This is because vhost->vdev is NULL before guest driver probe vblk > > > device, so vhost_user_blk_disconnect won't be called, s->connected is > > > still true. Next vhost_user_blk_connect will simply return without doing > > > anything. > > > > > > 2. modprobe -r virtio-blk inside VM, then disconnect backend, then > > > reconnect backend, then modprobe virtio-blk. QEMU won't send messages in > > > vhost_dev_init. > > > This is because rmmod will let qemu call vhost_user_blk_stop, vhost->vdev > > > also become NULL(in vhost_dev_stop), vhost_user_blk_disconnect won't be > > > called. Again s->connected is still true, even chr connect is closed. > > > > > > I think even vhost->vdev is NULL, vhost_user_blk_disconnect should be > > > called when chr connect close? > > > Hope we can have a fix soon. > > > > > > > > > Thanks, > > > Yajun > > >
