Hi Christoph, Thanks , got it.
Could you please do me favor to let me know the background why we ONLY support " MSDBD ==1"? I am NOT trying to resist or oppose anything , I just want to know the reason. You know, it is a little wired for me, as "MSDBD ==1" does not fulfill all the use cases which is depicted in the spec. Best, Robert Qiuxin ________________________________________ Robert Qiuxin 华为技术有限公司 Huawei Technologies Co., Ltd. Phone: +86-755-28420357 Fax: Mobile: +86 15986638429 Email: qiu...@huawei.com 地址：深圳市龙岗区坂田华为基地 邮编：518129 Huawei Technologies Co., Ltd. Bantian, Longgang District,Shenzhen 518129, P.R.China http://www.huawei.com ________________________________________ 本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群组。禁 止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮件中 的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！ This e-mail and its attachments contain confidential information from HUAWEI, which is intended only for the person or entity whose address is listed above. Any use of the information contained herein in any way (including, but not limited to, total or partial disclosure, reproduction, or dissemination) by persons other than the intended recipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email immediately and delete it! -----邮件原件----- 发件人: Christoph Hellwig [mailto:h...@lst.de] 发送时间: 2016年10月27日 14:41 收件人: 鑫愿 抄送: Bart Van Assche; Jens Axboe; linux-block@vger.kernel.org; James Bottomley; Martin K. Petersen; Mike Snitzer; linux-r...@vger.kernel.org; Ming Lei; linux-n...@lists.infradead.org; Keith Busch; Doug Ledford; linux-s...@vger.kernel.org; Laurence Oberman; Christoph Hellwig; Tiger zhao; Qiuxin (robert) 主题: Re: A question regarding "multiple SGL" Hi Robert, There is no feature called "Multiple SGL in one NVMe capsule". The NVMe over Fabrics specification allows a controller to advertise how many SGL descriptors it supports using the MSDBD Identify field: "Maximum SGL Data Block Descriptors (MSDBD): This field indicates the maximum number of (Keyed) SGL Data Block descriptors that a host is allowed to place in a capsule. A value of 0h indicates no limit." Setting this value to 1 is perfectly valid. Similarly a host is free to chose any number of SGL descriptors between 0 (only for command that don't transfer data) to the limit imposed by the controller using the MSDBD field. There are no plans to support a MSDBD value larger than 1 in the Linux NVMe target, and there are no plans to ever submit commands with multiple SGLs from the host driver either. Cheers, Christoph
