From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754897AbcCOUwq (ORCPT ); Tue, 15 Mar 2016 16:52:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51128 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751101AbcCOUwm (ORCPT ); Tue, 15 Mar 2016 16:52:42 -0400 From: Aaron Conole To: Paolo Abeni Cc: netdev@vger.kernel.org, "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [RFC -next 2/2] virtio_net: Read and use the advised MTU References: <1457620092-24170-1-git-send-email-aconole@redhat.com> <1457620092-24170-3-git-send-email-aconole@redhat.com> <1457621848.9753.44.camel@redhat.com> Date: Tue, 15 Mar 2016 16:52:39 -0400 In-Reply-To: <1457621848.9753.44.camel@redhat.com> (Paolo Abeni's message of "Thu, 10 Mar 2016 15:57:28 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paolo Abeni writes: > On Thu, 2016-03-10 at 09:28 -0500, Aaron Conole wrote: >> 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) { > > why don't: > > if ((vi->negotiated_mtu == true) && (dev->mtu != new_mtu)) > > ? Okay, I'll put this test in. >> + 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, > > Here a trailing white space slipped-in. > > Otherwise LGTM. > > Paolo D'oh! Okay, v2 will have this fixed. >> VIRTIO_F_ANY_LAYOUT, >> + VIRTIO_NET_F_MTU, >> }; >> >> static struct virtio_driver virtio_net_driver = { Thanks so much for the review, Paolo! -Aaron