Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933047AbaLDSl5 (ORCPT ); Thu, 4 Dec 2014 13:41:57 -0500 Received: from na6sys009bog021.obsmtp.com ([74.125.150.82]:32815 "HELO na6sys009bog021.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S932215AbaLDSlz (ORCPT ); Thu, 4 Dec 2014 13:41:55 -0500 MIME-Version: 1.0 In-Reply-To: References: <1416525081-27779-1-git-send-email-joestringer@nicira.com> From: Joe Stringer Date: Thu, 4 Dec 2014 10:41:34 -0800 Message-ID: Subject: Re: [PATCHv2 net] i40e: Implement ndo_gso_check() To: Jesse Gross Cc: Tom Herbert , netdev , Shannon Nelson , "Brandeburg, Jesse" , Jeff Kirsher , "linux.nics" , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2 December 2014 at 10:26, Jesse Gross wrote: > On Mon, Dec 1, 2014 at 4:09 PM, Tom Herbert wrote: >> On Mon, Dec 1, 2014 at 3:53 PM, Jesse Gross wrote: >>> On Mon, Dec 1, 2014 at 3:47 PM, Tom Herbert wrote: >>>> On Mon, Dec 1, 2014 at 3:35 PM, Joe Stringer wrote: >>>>> On 21 November 2014 at 09:59, Joe Stringer wrote: >>>>>> On 20 November 2014 16:19, Jesse Gross wrote: >>>>>>> I don't know if we need to have the check at all for IPIP though - >>>>>>> after all the driver doesn't expose support for it all (actually it >>>>>>> doesn't expose GRE either). This raises kind of an interesting >>>>>>> question about the checks though - it's pretty easy to add support to >>>>>>> the driver for a new GSO type (and I imagine that people will be >>>>>>> adding GRE soon) and forget to update the check. >>>>>> >>>>>> If the check is more conservative, then testing would show that it's >>>>>> not working and lead people to figure out why (and update the check). >>>>> >>>>> More concretely, one suggestion would be something like following at >>>>> the start of each gso_check(): >>>>> >>>>> + const int supported = SKB_GSO_TCPV4 | SKB_GSO_TCPV6 | SKB_GSO_FCOE | >>>>> + SKB_GSO_UDP | SKB_GSO_UDP_TUNNEL; >>>>> + >>>>> + if (skb_shinfo(skb)->gso_type & ~supported) >>>>> + return false; >>>> >>>> This should already be handled by net_gso_ok. >>> >>> My original point wasn't so much that this isn't handled at the moment >>> but that it's easy to add a supported GSO type but then forget to >>> update this check - i.e. if a driver already supports UDP_TUNNEL and >>> adds support for GRE with the same constraints. It seems not entirely >>> ideal that this function is acting as a blacklist rather than a >>> whitelist. >> >> Agreed, it would be nice to have all the checking logic in one place. >> If all the drivers end up implementing ndo_gso_check then we could >> potentially get rid of the GSO types as features. This probably >> wouldn't be a bad thing since we already know that the features >> mechanism doesn't scale (for instance there's no way to indicate that >> certain combinations of GSO types are supported by a device). > > This crossed my mind and I agree that it's pretty clear that the > features mechanism isn't scaling very well. Presumably, the logical > extension of this is that each driver would have a function that looks > at a packet and returns a set of offload operations that it can > support rather than exposing a set of protocols. However, it seems > like it would probably result in a bunch of duplicate code in each > driver. Given the discussion is still pretty open-ended, I've made the basic feedback changes for v3 and haven't tried to address the concern about forgetting to update this check when a driver adds support. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/