On Wed, 8 Apr 2020 10:25:42 +0800
Li Feng <fen...@smartx.com> wrote:
> Hi all,
>
> Hotplug of vhost-user-blk doesn't not work in qemu master branch and
> all previous version.
>
> The action I insert a vhost-user-blk disk is:
> (qemu) chardev-add socket,id=spdk_vhost_blk2,path=/vhost-blk.0,reconnect=1
> (qemu) device_add
> vhost-user-blk-pci,chardev=spdk_vhost_blk2,id=spdk_vhost_blk2,num-queues=4
>
> Until here, it's well.
>
> Then I unplug it from qemu:
> (qemu) device_del spdk_vhost_blk2
> (qemu) chardev-remove spdk_vhost_blk2
> Error: Chardev 'spdk_vhost_blk2' is busy
>
> The related code is here:
> qmp_chardev_remove
> -> qemu_chr_is_busy
> -> object_unparent(OBJECT(chr));
>
> 330 static bool qemu_chr_is_busy(Chardev *s)
> 331 {
> 332 if (CHARDEV_IS_MUX(s)) {
> 333 MuxChardev *d = MUX_CHARDEV(s);
> 334 return d->mux_cnt >= 0;
> 335 } else {
> 336 return s->be != NULL;
> 337 }
> 338 }
>
> My question is:
> 1. s->be is set to NULL when qemu_chr_fe_deinit is called.
> However, the qmp_chardev_remove is blocked at qemu_chr_is_busy check,
> then the object_unparent will not be called.
> 2. Is there a path that device_del will trigger the s->be that been set to
> NULL?
device_del is request for guest to eject device and once it's done backend
could be removed.
what's you command line? (so I could point out entry point where ejection
happens
for you to troubleshoot it further)
>
> How should I fix this issue?
> I have tested that comment the qemu_chr_is_busy works well.
>
> Thanks in advance.
>
> Feng Li
>
