Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751394AbaALMxF (ORCPT ); Sun, 12 Jan 2014 07:53:05 -0500 Received: from mail-ea0-f194.google.com ([209.85.215.194]:54294 "EHLO mail-ea0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751288AbaALMxC (ORCPT ); Sun, 12 Jan 2014 07:53:02 -0500 Message-ID: <52D29026.6000302@dev.mellanox.co.il> Date: Sun, 12 Jan 2014 14:52:54 +0200 From: Sagi Grimberg User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: "Martin K. Petersen" CC: "Nicholas A. Bellinger" , target-devel , linux-scsi , linux-kernel , Christoph Hellwig , Hannes Reinecke , Sagi Grimberg , Or Gerlitz , Nicholas Bellinger Subject: Re: [PATCH 09/14] target/configfs: Expose protection device attributes References: <1389212157-14540-1-git-send-email-nab@daterainc.com> <1389212157-14540-10-git-send-email-nab@daterainc.com> <52D28807.2000004@dev.mellanox.co.il> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/12/2014 2:43 PM, Martin K. Petersen wrote: >>>>>> "Sagi" == Sagi Grimberg writes: >>> The IP checksum is only supported by DIX between OS and initiator, >>> not by the target. I guess we could signal to the initiator via a >>> vendor-private VPD that IP checksum is supported directly. But now >>> what we have hardware-accelerated T10 CRC I don't think it's a big >>> deal. > Sagi> shouldn't it stick around if it is not deprecated yet, the > Sagi> transport is required to support ip-csum->CRC conversion anyhow. > > SBC mandates that the guard tag on the wire and on the target device be > the T10 CRC. The IP checksum is a DIX-optimization for application-HBA > exchanges. The only place you should support the IP checksum is in the > initiator. Right. > Note that you could conceivably do a T10 CRC to IP checksum conversion > on writes received by the target and store the IP checksum on disk. And > then convert back to T10 CRC when the data is eventually read. But it > makes no sense to do that given that you will have to do the T10 CRC > calculation regardless. Even if the backing store is DIX-capable and > supports the IP checksum. > I agree, but for backstore DIF (SW) emulation it will make sense. -- 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/