From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: tap/bridge: Dropping NETIF_F_GSO/NETIF_F_SG Date: Mon, 16 May 2011 11:28:10 +0300 Message-ID: <20110516082810.GA8252@redhat.com> References: <20110504181813.GA17547@redhat.com> <20110504223415.GA14819@gondor.apana.org.au> <20110504232854.GA11687@rere.qmqm.pl> <20110505084428.GB17647@redhat.com> <4DC26F33.8010700@cn.fujitsu.com> <20110505100506.GA20111@gondor.apana.org.au> <20110516073210.GB6610@redhat.com> <20110516080702.GA1857@gondor.apana.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Shan Wei , =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , netdev@vger.kernel.org, Ben Hutchings To: Herbert Xu Return-path: Received: from mx1.redhat.com ([209.132.183.28]:31537 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751739Ab1EPI2H (ORCPT ); Mon, 16 May 2011 04:28:07 -0400 Content-Disposition: inline In-Reply-To: <20110516080702.GA1857@gondor.apana.org.au> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, May 16, 2011 at 06:07:02PM +1000, Herbert Xu wrote: > On Mon, May 16, 2011 at 10:32:10AM +0300, Michael S. Tsirkin wrote: > > > > So how is NETIF_F_SG supposed to be enabled then? > > It should either be enabled at device creation time, or whatever > user-space entity managing the device creation should enable it > along with checksumming and anything else applicable. > > > In upstream kernels userspace can disable checksum offloading then > > re-enable and get SG set back. userspace came to depend on this > > behaviour so I think changing this is a regression. > > Can you point me to the relevant code in the upstream kernel? > I'm not aware of any automatic SG enabling for network devices > in general when you enable checksum offloading. > > Cheers, By the way with kvm we let an unpriveledged application control netdev flags through and ioctl. It's probably not a good idea to print out stuff on flag change unconditionally as that will let that application fill up the system log. > -- > Email: Herbert Xu > Home Page: http://gondor.apana.org.au/~herbert/ > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt