From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v3 1/3] fm10k: enable FTAG based forwarding Date: Fri, 26 Feb 2016 21:48:20 +0100 Message-ID: <1994581.FACV9pjC7W@xps13> References: <1454410216-13333-2-git-send-email-xiao.w.wang@intel.com> <4126401.C51dJZWCEs@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org To: "Wang, Xiao W" Return-path: Received: from mail-wm0-f54.google.com (mail-wm0-f54.google.com [74.125.82.54]) by dpdk.org (Postfix) with ESMTP id 42FB837B2 for ; Fri, 26 Feb 2016 21:49:54 +0100 (CET) Received: by mail-wm0-f54.google.com with SMTP id p65so1389255wmp.1 for ; Fri, 26 Feb 2016 12:49:54 -0800 (PST) In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 2016-02-26 09:24, Wang, Xiao W: > Hi, > > > -----Original Message----- > > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com] > > Sent: Friday, February 26, 2016 5:06 PM > > To: Wang, Xiao W > > Cc: Richardson, Bruce ; Chen, Jing D > > ; dev@dpdk.org > > Subject: Re: [dpdk-dev] [PATCH v3 1/3] fm10k: enable FTAG based forwarding > > > > 2016-02-26 04:31, Wang, Xiao W: > > > From: Richardson, Bruce > > > > On Thu, Feb 25, 2016 at 03:45:45PM +0000, Chen, Jing D wrote: > > > > > From: Richardson, Bruce > > > > > > On Thu, Feb 25, 2016 at 10:04:02AM +0000, Chen, Jing D wrote: > > > > > > > This feature is trying to use FTAG (a unique tech in fm10k) > > > > > > > instead of mac/vlan to forward packets. App need a way to tell > > > > > > > PMD driver that which forwarding style it would like to use. > > > > > > > > > > > > Why not just specify this in the port configuration at setup time? > > > > > > > > > > > > > > > > Please educate me. I think the port configuration flags are also > > > > > common to all PMD Drivers. Is it possible to add a flag like > > "RTE_USE_FTAG" > > > > and pass to PMD driver? > > > > > > > > > They are. > > > > For something PMD specific, like FTAG, it's always a challenge, and > > > > I don't know off the top of my head if there is a simple option. > > > > However, given the choice between an mbuf flag and a port config > > > > flag, I'd always choose the former. > > > > Other alternatives would be to have a fm10k specific API in the > > > > fm10k driver alone. > > > > > > > > I'll let Thomas as ethdev maintainer comment if he has other > > > > suggestions as to how to handle this case. I suspect this won't be > > > > the first device-specific piece of functionality we need to deal with. > > > > > > > > /Bruce > > > > > > Whatever method we choose, we have to find a way for the user to > > > express his need for FTAG, it maybe a build time config option, or a > > > port config flag (no such flag now), or a fast path flag in mbuf (no > > > such flag now) etc. For the customer Topsec's use case, they use FTAG > > > for all the TX packets, so all the above methods (per build config, > > > per port config, per mbuf config) can meet their need. Since the pmd > > > frame work is for common, it's hard to add new fields only for one specific > > NIC, so I add a build time config and make an introduction in the doc. > > > > > > Thanks for the discussion, Thomas, do you have any suggestions? > > > > I don't understand why you say this feature is specific to fm10k. Can we > > imagine another NIC having this capability? > > As you know, fm10k has a switch logic between the Mac and Phy, every packets > Sent out from the host will be switched inside the NIC, other NICs don't have > a switch inside, and the FTAG feature is related to the switch function. > > As introduced in the second patch: > The FM10K family of NICs support the addition of a Fabric Tag (FTAG) to carry > special information. The FTAG is placed at the beginning of the frame, it contains > information such as where the packet comes from and goes, and the vlan tag. In > FTAG based forwarding mode, the switch logic forwards packets according to > glort (global resource tag) information, rather than the mac and vlan table. > So this is a feature specific to fm10k. No I still don't think you should consider it specific to fm10k. But yes it is specific to a switch device. I'm OK to have a structure for switch configuration in ethdev.