From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: A question regarding "multiple SGL" Date: Thu, 27 Oct 2016 08:41:15 +0200 Message-ID: <20161027064115.GA5864@lst.de> References: <20161027005230.9904DC00097@webmail.sinamail.sina.com.cn> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20161027005230.9904DC00097-2RFepEojUI2gQzYKMK1YzK/p1tWXv8elb9TvmfFkwKk@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: =?utf-8?B?6ZGr5oS/?= Cc: Bart Van Assche , Jens Axboe , "linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , James Bottomley , "Martin K. Petersen" , Mike Snitzer , "linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Ming Lei , "linux-nvme-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , Keith Busch , Doug Ledford , "linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Laurence Oberman , Christoph Hellwig , "tiger.zhao" , qiuxin List-Id: linux-rdma@vger.kernel.org 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 -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html