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Subject: Re: [PATCH] virtio_net: enable tx after resuming from suspend
To:     Jason Wang <jasowang@redhat.com>
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>
 <dd530053-efab-b661-3423-1faaab8fb12f@redhat.com>
From:   ake <ake@igel.co.jp>
Message-ID: <7e87b140-79ae-c79e-40ed-dc76b38eeae4@igel.co.jp>
Date:   Thu, 11 Oct 2018 19:22:47 +0900
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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? Without
netif_start_queue(), the virtio_net device does not resume properly
after waking up.

Is it better to report this as a bug first? If I am to do more
investigation, what areas should I look into?


Best Regards
Ake Koomsin