From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755013AbbGCL3R (ORCPT ); Fri, 3 Jul 2015 07:29:17 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:47433 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755048AbbGCL3H (ORCPT ); Fri, 3 Jul 2015 07:29:07 -0400 Date: Fri, 3 Jul 2015 14:28:47 +0300 From: Dan Carpenter To: Haiyang Zhang Cc: davem@davemloft.net, netdev@vger.kernel.org, olaf@aepfle.de, jasowang@redhat.com, driverdev-devel@linuxdriverproject.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] hv_netvsc: Add support to set MTU reservation from guest side Message-ID: <20150703112847.GA28762@mwanda> References: <1435868255-10865-1-git-send-email-haiyangz@microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1435868255-10865-1-git-send-email-haiyangz@microsoft.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: userv0022.oracle.com [156.151.31.74] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 02, 2015 at 01:17:35PM -0700, Haiyang Zhang wrote: > When packet encapsulation is in use, the MTU needs to be reduced for > headroom reservation. > The existing code takes the updated MTU value only from the host side. > But vSwitch extensions, such as Open vSwitch, require the flexibility > to change the MTU to different values from within a guest during the > lifecycle of a vNIC, when the encapsulation protocol is changed. The > patch supports this kind of MTU changes. > > Signed-off-by: Haiyang Zhang > Reviewed-by: K. Y. Srinivasan > --- > drivers/net/hyperv/netvsc_drv.c | 3 +-- > drivers/net/hyperv/rndis_filter.c | 2 +- > 2 files changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c > index 358475e..68e7ece 100644 > --- a/drivers/net/hyperv/netvsc_drv.c > +++ b/drivers/net/hyperv/netvsc_drv.c > @@ -743,8 +743,7 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu) > if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2) > limit = NETVSC_MTU - ETH_HLEN; > > - /* Hyper-V hosts don't support MTU < ETH_DATA_LEN (1500) */ > - if (mtu < ETH_DATA_LEN || mtu > limit) > + if (mtu < 68 || mtu > limit) How did you calculate 68? Avoid magic numbers like this, make it a define. regards, dan carpenter