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Subject: Re: [PATCH] virtio_net: enable tx after resuming from suspend
To:     ake <ake@igel.co.jp>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20181011075127.2608-1-ake@igel.co.jp>
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 <a156fd7e-e36e-e4e9-c240-3117ecc5b1b4@redhat.com>
 <b294cbba-24a0-939d-98e8-d1483e3688a1@igel.co.jp>
 <4918ed7c-4c63-6f19-530b-8e16b0c496d4@redhat.com>
 <1aff0ad2-9d63-6d38-6b25-5c681eafdfb2@igel.co.jp>
 <e2baaccc-4ead-e61d-fc1e-d79435012e1c@igel.co.jp>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <024619cc-9b1b-dac2-18cc-5d757a76b1e3@redhat.com>
Date:   Tue, 16 Oct 2018 16:53:12 +0800
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On 2018/10/15 下午6:08, ake wrote:
>
> On 2018年10月12日 18:18, ake wrote:
>>
>> On 2018年10月12日 17:23, Jason Wang wrote:
>>>
>>> On 2018年10月12日 12:30, ake wrote:
>>>> On 2018年10月11日 22:06, Jason Wang wrote:
>>>>> On 2018年10月11日 18:22, ake wrote:
>>>>>> On 2018年10月11日 18:44, Jason Wang wrote:
>>>>>>> On 2018年10月11日 15:51, Ake Koomsin wrote:
>>>>>>>> commit 713a98d90c5e ("virtio-net: serialize tx routine during reset")
>>>>>>>> disabled the virtio tx before going to suspend to avoid a use after
>>>>>>>> free.
>>>>>>>> However, after resuming, it causes the virtio_net device to lose its
>>>>>>>> network connectivity.
>>>>>>>>
>>>>>>>> To solve the issue, we need to enable tx after resuming.
>>>>>>>>
>>>>>>>> Fixes commit 713a98d90c5e ("virtio-net: serialize tx routine during
>>>>>>>> reset")
>>>>>>>> Signed-off-by: Ake Koomsin <ake@igel.co.jp>
>>>>>>>> ---
>>>>>>>>      drivers/net/virtio_net.c | 1 +
>>>>>>>>      1 file changed, 1 insertion(+)
>>>>>>>>
>>>>>>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>>>>>>> index dab504ec5e50..3453d80f5f81 100644
>>>>>>>> --- a/drivers/net/virtio_net.c
>>>>>>>> +++ b/drivers/net/virtio_net.c
>>>>>>>> @@ -2256,6 +2256,7 @@ static int virtnet_restore_up(struct
>>>>>>>> virtio_device *vdev)
>>>>>>>>          }
>>>>>>>>            netif_device_attach(vi->dev);
>>>>>>>> +    netif_start_queue(vi->dev);
>>>>>>> I believe this is duplicated with netif_tx_wake_all_queues() in
>>>>>>> netif_device_attach() above?
>>>>>> Thank you for your review.
>>>>>>
>>>>>> If both netif_tx_wake_all_queues() and netif_start_queue() result in
>>>>>> clearing __QUEUE_STATE_DRV_XOFF, then is it possible that some
>>>>>> conditions in netif_device_attach() is not satisfied?
>>>>> Yes, maybe. One case I can see now is when the device is down, in this
>>>>> case netif_device_attach() won't try to wakeup the queue.
>>>>>
>>>>>>     Without
>>>>>> netif_start_queue(), the virtio_net device does not resume properly
>>>>>> after waking up.
>>>>> How do you trigger the issue? Just do suspend/resume?
>>>> Yes, simply suspend and resume.
>>>>
>>>> Here is how I trigger the issue:
>>>>
>>>> 1) Start the Virtual Machine Manager GUI program.
>>>> 2) Create a guest Linux OS. Make sure that the guest OS kernel is
>>>>      >= 4.12. Make sure that it uses virtio_net as its network device.
>>>>      In addition, make sure that the video adapter is VGA. Otherwise,
>>>>      waking up with the virtual power button does not work.
>>>> 3) After installing the guest OS, log in, and test the network
>>>>      connectivity by ping the host machine.
>>>> 4) Suspend. After this, the screen is blank.
>>>> 5) Resume by hitting the virtual power button. The login screen
>>>>      appears again.
>>>> 6) Log in again. The guest loses its network connection.
>>>>
>>>> In my test:
>>>> Guest: Ubuntu 16.04/18.04 with kernel 4.15.0-36-generic
>>>> Host: Ubuntu 16.04 with kernel 4.15.0-36-generic/4.4.0-137-generic
>>> I can not reproduce this issue if virtio-net interface is up in guest
>>> before the suspend. I'm using net-next.git and qemu master. But I do
>>> reproduce when virtio-net interface is down in guest before suspend,
>>> after resume, even if I make it up, the network is still lost.
>>>
>>> I think the interface is up in your case, but please confirm this.
>> If you mean the interface state before I hit the suspend button,
>> the answer is yes. The interface is up before I suspend the guest
>> machine.
>>
>> Note that my current QEMU version is QEMU emulator version 2.5.0
>> (Debian 1:2.5+dfsg-5ubuntu10.32).
>>
>> I will try with net-next.git and qemu master later and see if I can
>> reproduce the issue.
> Update. I tried with net-next and qemu master. Interestingly, the result
> is different from yours. The network is lost even if the virtio_net
> interface is up before suspending.
>
> Host: Ubuntu 16.04 with net-next kernel (default configuration)
> Guest: Ubuntu 18.04 with net-next kernel (default configuration)
> Qemu: master
> Qemu command:
> qemu-system-x86_64 -cpu host -m 2048 -enable-kvm \
> -bios /usr/share/OVMF/OVMF_CODE.fd \
> -drive file=/var/lib/libvirt/images/virtio_test.qcow2,if=virtio \
> -netdev user,id=hostnet0 \
> -device virtio-net-pci,netdev=hostnet0 \
> -device VGA,id=video0,vgamem_mb=16 \
> -global PIIX4_PM.disable_s3=1 \
> -global PIIX4_PM.disable_s4=1 -monitor stdio


Interesting, just notice you're using userspace network. To isolate the 
issue, can you retry with e.g tap or e1000 to make sure it's not a fault 
of slirp or virito-net?

Thanks