Re: [Qemu-devel] PCI: Hot-removing a virtio-blk causes guest panic

[Amos Kong]

On Sat, May 12, 2012 at 12:30 AM, Michael S. Tsirkin <address@hidden> wrote:
>
> On Fri, May 11, 2012 at 12:37:49PM +0800, Amos Kong wrote:
> > good: 3.3.0 guest kernel & qemu-kvm-rhel6
> > guest panic:  3.3.0 guest kernel & qemu-upstream (contains fix [1])
> >
> > I didn't change anything of guest kernel,
> > It seems a bug of qemu-upstream.
> >
> > [1] http://marc.info/?l=qemu-devel&m=133670266801022&w=2
> >     [PATCH] qom: fix refcounting in object_property_del_child()
>

This fix is wrong, I had sent another patch to fix the object release issues.

http://marc.info/?t=133674851100009&r=1&w=2

After apply this patch to qemu, guest panic disappears. Guest panic
should be caused that the object is not released in qemu.



>
> > >>> Start VM with one block device:
> > qemu-upstream --enable-kvm  -name 'vm1' -nodefaults -drive
> > file='nolvm.qcow2',index=0,if=virtio,cache=none,snapshot=on -net none -m
> > 2000 -smp 2 -vnc :0  -kernel vmlinuz-3.3.0 -append 'ro root=/dev/vda1
> > console=tty0 console=ttyS0,115200'   -drive
> > file=images/u0,if=none,id=drive-virtio0-0-0,format=qcow2,cache=none
> > -device virtio-blk-pci,drive=drive-virtio0-0-0,id=virti0-0-0 -monitor
> > unix:/tmp/m,nowait,server
> >
> > >>> hot-remove the virtio disk
> > (qemu)# echo "device_del virti0-0-0" | nc -U /tmp/m
> >
> > >>> guest panic:
>
>
> Find a working version and bisect?
>

I tried to bisect obj-ref issue first, and found guest panic is caused by that.


Amos