Re: [Qemu-devel] [vhost-user BUG ?] QEMU process segfault when shutdown or reboot with vhost-user

[Jason Wang <jasowang@redhat.com>]

On 11/04/2015 10:24 AM, zhanghailiang wrote:
> On 2015/11/3 22:54, Marc-André Lureau wrote:
>> Hi
>>
>> On Tue, Nov 3, 2015 at 2:01 PM, zhanghailiang
>> <zhang.zhanghailiang@huawei.com> wrote:
>>> The corresponding codes where gdb reports error are: (We have added
>>> some
>>> codes in net.c)
>>
>> Can you reproduce with unmodified qemu? Could you give instructions
>> to do so?
>>
>
> OK, i will try to do it. There is nothing special, we run iperf tool
> in VM,
> and then shutdown or reboot it. There is change you can catch segfault.
>
>>> ssize_t qemu_deliver_packet(NetClientState *sender,
>>>                              unsigned flags,
>>>                              const uint8_t *data,
>>>                              size_t size,
>>>                              void *opaque)
>>> {
>>>      NetClientState *nc = opaque;
>>>      ssize_t ret;
>>>
>>>      if (nc->link_down) {
>>>          return size;
>>>      }
>>>
>>>      if (nc->receive_disabled) {
>>>          return 0;
>>>      }
>>>
>>>      if (flags & QEMU_NET_PACKET_FLAG_RAW && nc->info->receive_raw) {
>>>          ret = nc->info->receive_raw(nc, data, size);
>>>      } else {
>>>          ret = nc->info->receive(nc, data, size);   ----> Here is
>>> 510 line
>>>      }
>>>
>>> I'm not quite familiar with vhost-user, but for vhost-user, these two
>>> callback functions seem to be always NULL,
>>> Why we can come here ?
>>
>> You should not come here, vhost-user has nc->receive_disabled (it
>> changes in 2.5)
>>
>
> I have looked at the newest codes, i think we can still have chance to
> come here, since we will change nc->receive_disable to false
> temporarily in
> qemu_flush_or_purge_queued_packets(), there is no difference between
> 2.3 and 2.5
> for this.
> Besides, is it possible for !QTAILQ_EMPTY(&queue->packets) to be true
> in qemu_net_queue_flush() for vhost-user ?

The only thing I can image is self announcing. Are you trying to do
migration? 2.5 only support sending rarp through this.

And it's better to have a breakpoint to see why a packet was queued for
vhost-user. The stack trace may also help in this case.

>
> i will try to reproduce it by using newest qemu.
>
> Thanks,
> zhanghailiang
>