From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751772Ab1GYJoA (ORCPT ); Mon, 25 Jul 2011 05:44:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41921 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750864Ab1GYJnw (ORCPT ); Mon, 25 Jul 2011 05:43:52 -0400 Date: Mon, 25 Jul 2011 12:44:14 +0300 From: "Michael S. Tsirkin" To: Herbert Xu Cc: Shirley Ma , davem@davemloft.net, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] skbuff: clear tx zero-copy flag Message-ID: <20110725094414.GA11776@redhat.com> References: <1310195566.25391.6.camel@localhost.localdomain> <20110725004200.GA25794@gondor.apana.org.au> <20110725080743.GC7840@redhat.com> <20110725084057.GA30311@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110725084057.GA30311@gondor.apana.org.au> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 25, 2011 at 04:40:57PM +0800, Herbert Xu wrote: > On Mon, Jul 25, 2011 at 11:07:43AM +0300, Michael S. Tsirkin wrote: > > > > However macvtap passes an skb directly to the > > lower device, so as long as macvtap is the only user > > of that interface, we are fine I think - there's > > no way for an skb to get from macvtap to splice > > read path I think. > > > > Right? > > Yes, as long as you can guarantee that the skb never loops back > then you should be fine. > > However, does macvtap really bypass everything, including the > qdisc layer? The qdisc layer is certainly capable of looping > the skb back with the redirect action. > > Cheers, No, I don't think macvtap bypasses the qdisc. Is the action in question here? static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a, struct tcf_result *res) if yes that seems to always clone an skb, which in turn does the copy so we are fine? > -- > Email: Herbert Xu > Home Page: http://gondor.apana.org.au/~herbert/ > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt