netdev - Re: [net-next PATCH v2 1/5] net: virtio dynamically disable/enable LRO

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Date:   Tue, 22 Nov 2016 00:16:26 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     daniel@...earbox.net, eric.dumazet@...il.com, kubakici@...pl,
        shm@...ulusnetworks.com, davem@...emloft.net,
        alexei.starovoitov@...il.com, netdev@...r.kernel.org,
        bblanco@...mgrid.com, john.r.fastabend@...el.com,
        brouer@...hat.com, tgraf@...g.ch
Subject: Re: [net-next PATCH v2 1/5] net: virtio dynamically disable/enable
 LRO

On 16-11-21 03:23 PM, Michael S. Tsirkin wrote:
> On Sat, Nov 19, 2016 at 06:49:34PM -0800, John Fastabend wrote:
>> This adds support for dynamically setting the LRO feature flag. The
>> message to control guest features in the backend uses the
>> CTRL_GUEST_OFFLOADS msg type.
>>
>> Signed-off-by: John Fastabend <john.r.fastabend@...el.com>
>> ---
>>  drivers/net/virtio_net.c |   45 ++++++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 44 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index ca5239a..8189e5b 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1419,6 +1419,41 @@ static void virtnet_init_settings(struct net_device *dev)
>>  	.set_settings = virtnet_set_settings,
>>  };
>>  
>> +static int virtnet_set_features(struct net_device *netdev,
>> +				netdev_features_t features)
>> +{
>> +	struct virtnet_info *vi = netdev_priv(netdev);
>> +	struct virtio_device *vdev = vi->vdev;
>> +	struct scatterlist sg;
>> +	u64 offloads = 0;
>> +
>> +	if (features & NETIF_F_LRO)
>> +		offloads |= (1 << VIRTIO_NET_F_GUEST_TSO4) |
>> +			    (1 << VIRTIO_NET_F_GUEST_TSO6);
>> +
>> +	if (features & NETIF_F_RXCSUM)
>> +		offloads |= (1 << VIRTIO_NET_F_GUEST_CSUM);
>> +
>> +	if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
>> +		sg_init_one(&sg, &offloads, sizeof(uint64_t));
>> +		if (!virtnet_send_command(vi,
>> +					  VIRTIO_NET_CTRL_GUEST_OFFLOADS,
>> +					  VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET,
>> +					  &sg)) {
>> +			dev_warn(&netdev->dev,
>> +				 "Failed to set guest offloads by virtnet command.\n");
>> +			return -EINVAL;
>> +		}
>> +	} else if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) &&
>> +		   !virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) {
>> +		dev_warn(&netdev->dev,
>> +			 "No support for setting offloads pre version_1.\n");
>> +		return -EINVAL;
>> +	}
> 
> I don't get this last warning. VIRTIO_NET_F_CTRL_GUEST_OFFLOADS
> was exposes by legacy devices, I don't think it's related to
> VIRTIO_F_VERSION_1.
> 

OK looks like I can just drop the else if branch here.

Thanks,
John