From patchwork Tue Mar 15 21:04:13 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aaron Conole X-Patchwork-Id: 597862 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3qPnF32Qqbz9sRZ for ; Wed, 16 Mar 2016 08:04:55 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752390AbcCOVEr (ORCPT ); Tue, 15 Mar 2016 17:04:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59007 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751101AbcCOVEQ (ORCPT ); Tue, 15 Mar 2016 17:04:16 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 2A8387AEB1; Tue, 15 Mar 2016 21:04:16 +0000 (UTC) Received: from aconole-fed23.bos.redhat.com (dhcp-25-35.bos.redhat.com [10.18.25.35]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u2FL4EIw021463; Tue, 15 Mar 2016 17:04:15 -0400 From: Aaron Conole To: netdev@vger.kernel.org, "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: [RFC v2 -next 2/2] virtio_net: Read the advised MTU Date: Tue, 15 Mar 2016 17:04:13 -0400 Message-Id: <1458075853-14789-3-git-send-email-aconole@redhat.com> In-Reply-To: <1458075853-14789-1-git-send-email-aconole@redhat.com> References: <1458075853-14789-1-git-send-email-aconole@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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 drivers/net/virtio_net.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 767ab11..429fe01 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 +1391,11 @@ 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) && (dev->mtu != new_mtu)) + pr_warn("changing mtu while the advised mtu bit exists."); dev->mtu = new_mtu; return 0; } @@ -1836,6 +1840,13 @@ 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; @@ -2019,6 +2030,7 @@ 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 = {