From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: [PATCH 10/11] IB: only keep a single key in struct ib_mr Date: Tue, 22 Dec 2015 15:50:12 +0200 Message-ID: <56795514.9090704@dev.mellanox.co.il> References: <1448214409-7729-1-git-send-email-hch@lst.de> <1448214409-7729-11-git-send-email-hch@lst.de> <56791542.6020604@dev.mellanox.co.il> <20151222131326.GA25267@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20151222131326.GA25267-jcswGhMUV9g@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Christoph Hellwig Cc: dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Liran Liss List-Id: linux-rdma@vger.kernel.org On 22/12/2015 15:13, Christoph Hellwig wrote: > On Tue, Dec 22, 2015 at 11:17:54AM +0200, Sagi Grimberg wrote: >> What makes me worried here is that the IB/RoCE specification really >> defines different keys for local and remote access. I'm less concerned >> about our consumers but more about our providers. We keep seeing new >> providers come along and its not impossible that a specific HW will >> *rely* on this distinction. In such a case we'd need to revert this >> patch altogether in that very moment. >> >> I think we're better off working on proper abstractions to help ULPs >> get it right (and simple!), without risking future devices support. > > With the new API in the next patch ULPs simply can't request an lkey > and a rkey at the same time, so for kernel use it's not a problmblem at > all. This is why I said that the problem here is not the ULPs. But if a new HW comes along with distinction between rkeys and lkeys it will have a problem. For example a HW allocates two different keys, rkey and lkey. And, it chooses to fail SEND from a rkey, or incoming READ/WRITE to a lkey. How can such a device be supported with an API that allows a single key per MR? -- 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