On 3/27/2024 6:47 PM, Stefano Garzarella wrote:
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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.
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