Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754679AbcDATcV (ORCPT ); Fri, 1 Apr 2016 15:32:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50442 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbcDATcU (ORCPT ); Fri, 1 Apr 2016 15:32:20 -0400 From: Aaron Conole To: netdev@vger.kernel.org, "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Paolo Abeni , Sergei Shtylyov , Pankaj Gupta Subject: [RFC v3 -next 2/2] virtio_net: Read the advised MTU Date: Fri, 1 Apr 2016 15:32:16 -0400 Message-Id: <1459539136-13948-3-git-send-email-aconole@redhat.com> In-Reply-To: <1459539136-13948-1-git-send-email-aconole@redhat.com> References: <1459539136-13948-1-git-send-email-aconole@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1721 Lines: 55 This patch checks the feature bit for the VIRTIO_NET_F_MTU feature. If it exists, read the advised MTU and use it. No proper error handling is provided for the case where a user changes the negotiated MTU. A future commit will add proper error handling. Instead, a warning is emitted if the guest changes the device MTU after previously being given advice. Signed-off-by: Aaron Conole --- v2: * Whitespace cleanup in the last hunk * Code style change around the pr_warn * Additional test for mtu change before printing warning v3: * removed the mtu change warning drivers/net/virtio_net.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 49d84e5..2308083 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1450,6 +1450,7 @@ static const struct ethtool_ops virtnet_ethtool_ops = { static int virtnet_change_mtu(struct net_device *dev, int new_mtu) { + struct virtnet_info *vi = netdev_priv(dev); if (new_mtu < MIN_MTU || new_mtu > MAX_MTU) return -EINVAL; dev->mtu = new_mtu; @@ -1896,6 +1897,12 @@ static int virtnet_probe(struct virtio_device *vdev) if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ)) vi->has_cvq = true; + if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) { + dev->mtu = virtio_cread16(vdev, + offsetof(struct virtio_net_config, + mtu)); + } + if (vi->any_header_sg) dev->needed_headroom = vi->hdr_len; @@ -2081,6 +2088,7 @@ static unsigned int features[] = { VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, VIRTIO_NET_F_CTRL_MAC_ADDR, VIRTIO_F_ANY_LAYOUT, + VIRTIO_NET_F_MTU, }; static struct virtio_driver virtio_net_driver = { -- 2.5.5