netdev - Re: Linux 4.14 - regression: broken tun/tap / bridge network with virtio

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Date:   Wed, 6 Dec 2017 11:08:41 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Andreas Hartmann <andihartmann@...19freenet.de>
Cc:     netdev@...r.kernel.org, john.fastabend@...il.com,
        Michal Kubecek <mkubecek@...e.cz>
Subject: Re: Linux 4.14 - regression: broken tun/tap / bridge network with
 virtio - bisected



On 2017年12月06日 00:23, Andreas Hartmann wrote:
> On 12/05/2017 at 04:50 AM Jason Wang wrote:
>>
>> On 2017年12月05日 00:28, Andreas Hartmann wrote:
>>> On 12/03/2017 at 12:35 PM Andreas Hartmann wrote:
>>>> On 12/01/2017 at 11:11 AM Andreas Hartmann wrote:
>>>>> Hello!
>>>>>
>>>>> I hopefully could get rid of both of my problems (hanging network w/
>>>>> virtio) and endless hanging qemu-process on VM shutdown by upgrading
>>>>> qemu from 2.6.2 to 2.10.1. I hope it will persist.
>>>> It didn't persist. 10h later - same problems happened again. It's just
>>>> much harder to trigger the problems.
>>>>
>>>> I'm now trying it with
>>>>
>>>> CONFIG_RCU_NOCB_CPU=y and
>>>> rcu_nocbs=0-15
>>>>
>>>> Since then, I didn't see any problem any more. But this doesn't mean
>>>> anything until now ... .
>>> Didn't work ether. Disabling vhost_net's zcopy hadn't any effect, too.
>>>
>>> => It's just finally broken since
>>>
>>> 2ddf71e23cc246e95af72a6deed67b4a50a7b81c
>>> net: add notifier hooks for devmap bpf map
>> Hi:
>>
>> Did you use XDP devmap in host? If not, please double check it was the
>> first bad commit since the patch should only work when XDP/devmap is
>> used on host.
> How do I know if XDP/devmap is enabled / used? Could you please give
> some hint?
>
>
> Thanks,
> Andreas

Something like:

./ip link | grep xdp
10: tap0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 xdp qdisc mq master 
kvmbr0 state UNKNOWN mode DEFAULT group default qlen 1000
     prog/xdp id 4 tag 0381911915bc8d7f

But you should have some recent version of ip.

Thanks