Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753981AbdDNRab (ORCPT ); Fri, 14 Apr 2017 13:30:31 -0400 Received: from ale.deltatee.com ([207.54.116.67]:41293 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751612AbdDNRa2 (ORCPT ); Fri, 14 Apr 2017 13:30:28 -0400 To: Benjamin Herrenschmidt , Jason Gunthorpe , Bjorn Helgaas References: <1490911959-5146-1-git-send-email-logang@deltatee.com> <1491974532.7236.43.camel@kernel.crashing.org> <5ac22496-56ec-025d-f153-140001d2a7f9@deltatee.com> <1492034124.7236.77.camel@kernel.crashing.org> <81888a1e-eb0d-cbbc-dc66-0a09c32e4ea2@deltatee.com> <20170413232631.GB24910@bhelgaas-glaptop.roam.corp.google.com> <20170414041656.GA30694@obsidianresearch.com> <1492169849.25766.3.camel@kernel.crashing.org> Cc: Christoph Hellwig , Sagi Grimberg , "James E.J. Bottomley" , "Martin K. Petersen" , Jens Axboe , Steve Wise , Stephen Bates , Max Gurtovoy , Dan Williams , Keith Busch , linux-pci@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, linux-nvdimm@ml01.01.org, linux-kernel@vger.kernel.org, Jerome Glisse From: Logan Gunthorpe Message-ID: <630c1c63-ff17-1116-e069-2b8f93e50fa2@deltatee.com> Date: Fri, 14 Apr 2017 11:30:14 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.6.0 MIME-Version: 1.0 In-Reply-To: <1492169849.25766.3.camel@kernel.crashing.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 50.66.97.235 X-SA-Exim-Rcpt-To: jglisse@redhat.com, linux-kernel@vger.kernel.org, linux-nvdimm@ml01.01.org, linux-rdma@vger.kernel.org, linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org, linux-pci@vger.kernel.org, keith.busch@intel.com, dan.j.williams@intel.com, maxg@mellanox.com, sbates@raithlin.com, swise@opengridcomputing.com, axboe@kernel.dk, martin.petersen@oracle.com, jejb@linux.vnet.ibm.com, sagi@grimberg.me, hch@lst.de, helgaas@kernel.org, jgunthorpe@obsidianresearch.com, benh@kernel.crashing.org X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [RFC 0/8] Copy Offload with Peer-to-Peer PCI Memory X-SA-Exim-Version: 4.2.1 (built Mon, 26 Dec 2011 16:24:06 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 974 Lines: 21 On 14/04/17 05:37 AM, Benjamin Herrenschmidt wrote: > I object to designing a subsystem that by design cannot work on whole > categories of architectures out there. Hardly. That's extreme. We'd design a subsystem that works for the easy cases and needs more work to support the offset cases. It would not be designed in such a way that it could _never_ support those architectures. It would simply be such that it only permits use by the cases that are known to work. Then those cases could be expanded as time goes on and people work on adding more support. There's tons of stuff that needs to be done to get this upstream. I'd rather not require it to work for every possible architecture from the start. The testing alone would be impossible. Many subsystems start by working for x86 first and then adding support in other architectures later. (Often with that work done by the people who care about those systems and actually have the hardware to test with.) Logan