Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752225AbcCJO2h (ORCPT ); Thu, 10 Mar 2016 09:28:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58064 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752104AbcCJO2R (ORCPT ); Thu, 10 Mar 2016 09:28:17 -0500 From: Aaron Conole To: netdev@vger.kernel.org, "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: [RFC -next 2/2] virtio_net: Read and use the advised MTU Date: Thu, 10 Mar 2016 09:28:12 -0500 Message-Id: <1457620092-24170-3-git-send-email-aconole@redhat.com> In-Reply-To: <1457620092-24170-1-git-send-email-aconole@redhat.com> References: <1457620092-24170-1-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: 2023 Lines: 65 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 --- drivers/net/virtio_net.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 767ab11..7175563 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -146,6 +146,7 @@ struct virtnet_info { virtio_net_ctrl_ack ctrl_status; u8 ctrl_promisc; u8 ctrl_allmulti; + bool negotiated_mtu; }; struct padded_vnet_hdr { @@ -1390,8 +1391,12 @@ 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; + if (vi->negotiated_mtu == true) { + pr_warn("changing mtu from negotiated mtu."); + } dev->mtu = new_mtu; return 0; } @@ -1836,6 +1841,13 @@ 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)) { + vi->negotiated_mtu = true; + dev->mtu = virtio_cread16(vdev, + offsetof(struct virtio_net_config, + mtu)); + } + if (vi->any_header_sg) dev->needed_headroom = vi->hdr_len; @@ -2017,8 +2029,9 @@ static unsigned int features[] = { VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ, VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, - VIRTIO_NET_F_CTRL_MAC_ADDR, + VIRTIO_NET_F_CTRL_MAC_ADDR, VIRTIO_F_ANY_LAYOUT, + VIRTIO_NET_F_MTU, }; static struct virtio_driver virtio_net_driver = { -- 2.5.0