From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [RFC PATCH 2/2] macvtap: TX zero copy between guest and host kernel Date: Wed, 15 Sep 2010 19:30:34 +0200 Message-ID: <20100915173034.GB2612@redhat.com> References: <1284490143.13351.82.camel@localhost.localdomain> <20100914190156.GA16037@redhat.com> <1284492983.13351.95.camel@localhost.localdomain> <20100915051241.GA25340@redhat.com> <1284531675.24603.259.camel@localhost.localdomain> <20100915101000.GB28016@redhat.com> <1284562354.2573.12.camel@localhost.localdomain> <20100915150412.GA679@redhat.com> <20100915153927.GA1065@redhat.com> <1284570004.2573.14.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Arnd Bergmann , Avi Kivity , "Xin, Xiaohui" , David Miller , netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Shirley Ma Return-path: Received: from mx1.redhat.com ([209.132.183.28]:8872 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752560Ab0IORgq (ORCPT ); Wed, 15 Sep 2010 13:36:46 -0400 Content-Disposition: inline In-Reply-To: <1284570004.2573.14.camel@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Sep 15, 2010 at 10:00:04AM -0700, Shirley Ma wrote: > On Wed, 2010-09-15 at 17:39 +0200, Michael S. Tsirkin wrote: > > In fact, I rechecked: both bridge and loopback have NETIF_F_HIGHDMA > > set. > > So maybe we should check NETIF_F_NETNS_LOCAL ... > > > > macvtap in bridged mode is interesting as well. > > I found that too, just wondered which flag to use is better. :) > > Thanks > Shirley At some level NETIF_F_NETNS_LOCAL makes sense: local packets can get anywhere. OTOH one wonders whether there might be other issues, e.g. in theory devices could hang on to frag pages just by doing get_page. There might be other issues. Maybe we are better off white-listing known-good drivers with a new flag? -- MST