netdev - Re: [PATCH net-next] virtio_net: implement VIRTIO_CONFIG_S_NEEDS

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Date:   Mon, 16 Oct 2017 11:03:18 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jason Wang <jasowang@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH net-next] virtio_net: implement VIRTIO_CONFIG_S_NEEDS_RESET

>> +static int virtnet_reset(struct virtnet_info *vi)
>> +{
>> +     struct virtio_device *dev = vi->vdev;
>> +     int ret;
>> +
>> +     virtio_config_disable(dev);
>> +     dev->failed = dev->config->get_status(dev) & VIRTIO_CONFIG_S_FAILED;
>> +     virtnet_freeze_down(dev, true);
>> +     remove_vq_common(vi);
>> +
>> +     virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE);
>> +     virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
>> +
>> +     ret = virtio_finalize_features(dev);
>> +     if (ret)
>> +             goto err;
>> +
>> +     ret = virtnet_restore_up(dev);
>> +     if (ret)
>> +             goto err;
>> +
>> +     ret = virtnet_set_queues(vi, vi->curr_queue_pairs);
>> +     if (ret)
>> +             goto err;
>> +
>> +     virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
>> +     virtio_config_enable(dev);
>> +     return 0;
>> +
>> +err:
>> +     virtio_add_status(dev, VIRTIO_CONFIG_S_FAILED);
>> +     return ret;
>> +}
>> +
>>  static int virtnet_set_guest_offloads(struct virtnet_info *vi, u64 offloads)
>>  {
>>       struct scatterlist sg;
>
> I have a question here though. How do things like MAC address
> get restored?
>
> What about the rx mode?
>
> vlans?

The function as is releases and reinitializes only ring state.
Device configuration such as mac and vlan persist across
the reset.

> Also, it seems that LINK_ANNOUNCE requests will get ignored
> even if they got set before the reset, leading to downtime.

Do you mean act on VIRTIO_NET_F_GUEST_ANNOUNCE
requests? That flag is tested and netdev_notify_peers
called before resetting virtio ring state.