From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:48083)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1W4086-0008Pd-0f
	for qemu-devel@nongnu.org; Thu, 16 Jan 2014 22:30:03 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1W407z-0001WW-Jh
	for qemu-devel@nongnu.org; Thu, 16 Jan 2014 22:29:57 -0500
Received: from mx1.redhat.com ([209.132.183.28]:25467)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <stefanha@redhat.com>) id 1W407z-0001WQ-3h
	for qemu-devel@nongnu.org; Thu, 16 Jan 2014 22:29:51 -0500
Date: Fri, 17 Jan 2014 11:29:39 +0800
From: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20140117032939.GD16061@stefanha-thinkpad.redhat.com>
References: <1389697190-6198-1-git-send-email-v.maffione@gmail.com>
	<1389697190-6198-3-git-send-email-v.maffione@gmail.com>
	<20140116092933.GA21761@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20140116092933.GA21761@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v2 2/6] net: removing tap_using_vnet_hdr()
	function
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: marcel.a@redhat.com, jasowang@redhat.com, qemu-devel@nongnu.org, Vincenzo Maffione <v.maffione@gmail.com>, lcapitulino@redhat.com, aliguori@amazon.com, dmitry@daynix.com, pbonzini@redhat.com, g.lettieri@iet.unipi.it, rizzo@iet.unipi.it

On Thu, Jan 16, 2014 at 11:29:34AM +0200, Michael S. Tsirkin wrote:
> On Tue, Jan 14, 2014 at 11:59:46AM +0100, Vincenzo Maffione wrote:
> > This function was used to set the using_vnet_hdr field into the
> > TAPState struct. However, it is always called immediately before
> > (see virtio-net.c) or immediately after (see vmxnet3.c) the function
> > tap_set_vnet_hdr_len(). It's therefore possible to set the
> > using_vnet_hdr field directly in tap_set_vnet_hdr_len() and remove
> > tap_using_vnet_hdr(), making the code simpler.
> > 
> > Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
> 
> 
> virtio net only calls tap_set_vnet_hdr_len if tap_has_vnet_hdr_len
> returns true.
> I think this patch will break old linux hosts which don't support
> modifying vnet_hdr_len.

This is a good point.  Let's leave the API alone then.

Stefan