Re: Shutting down a VM with Kernel 4.14 will sometime hang and a reboot is the only way to recover.

[Jason Wang <jasowang@redhat.com>]

On 2017年11月29日 10:52, Dave Hill wrote:
>>>
>>
>> Thanks. Zerocopy is disabled by several distribution by default. For 
>> upstream, the only reason to let it on is to hope more developers can 
>> help and fix the issues.
>>
>>
> So I never hit this issue with previous kernel and this issue started 
> happening with the v4.14-rc series.


Right, this still need to be investigated if it was introduced recently.

Looking at git history, the only suspected commit is for 4.14 is

commit 1e6f74536de08b5e50cf0e37e735911c2cef7c62
Author: Willem de Bruijn <willemb@google.com>
Date:   Fri Oct 6 13:22:31 2017 -0400

     vhost_net: do not stall on zerocopy depletion

Maybe you can try to revert it and see.

If it does not solve your issue, I suspect there's bug elsewhere that 
cause a packet to be held for very long time.

>   I'm using rawhide so perhaps this is why it isn't disabled by 
> default but I have to mention it's an update of FC25 up to FC28 and it 
> never got disabled.
> Perhaps it should be disabled in Fedora too if it's not the case... 
> I'm not sure this is the place to discuss this ... is it? 

Probably not, but I guess Fedora tries to use new technology aggressively.

Thanks