Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757715AbdDRUGV (ORCPT ); Tue, 18 Apr 2017 16:06:21 -0400 Received: from ale.deltatee.com ([207.54.116.67]:54448 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755558AbdDRUGT (ORCPT ); Tue, 18 Apr 2017 16:06:19 -0400 To: Jason Gunthorpe References: <1492381396.25766.43.camel@kernel.crashing.org> <20170418164557.GA7181@obsidianresearch.com> <20170418190138.GH7181@obsidianresearch.com> <20170418194845.GA22895@obsidianresearch.com> Cc: Benjamin Herrenschmidt , Dan Williams , Bjorn Helgaas , Christoph Hellwig , Sagi Grimberg , "James E.J. Bottomley" , "Martin K. Petersen" , Jens Axboe , Steve Wise , Stephen Bates , Max Gurtovoy , Keith Busch , linux-pci@vger.kernel.org, linux-scsi , linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, linux-nvdimm , "linux-kernel@vger.kernel.org" , Jerome Glisse From: Logan Gunthorpe Message-ID: <643a2bf3-c60d-b0d1-666b-ff33b360723e@deltatee.com> Date: Tue, 18 Apr 2017 14:06:14 -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: <20170418194845.GA22895@obsidianresearch.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 172.16.1.111 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, 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, dan.j.williams@intel.com, benh@kernel.crashing.org, jgunthorpe@obsidianresearch.com 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: 695 Lines: 22 On 18/04/17 01:48 PM, Jason Gunthorpe wrote: > I think this is why progress on this keeps getting stuck - every > solution is a lot of work. Yup! There's also a ton of work just to get the iomem safety issues addressed. Let alone the dma mapping issues. > You could try to do a dummy mapping / create a MR early on to detect > this. Ok, that could be a workable solution. > FWIW, I wonder if from a RDMA perspective we have another > problem.. Should we allow P2P memory to be used with the local DMA > lkey? There are potential designs around virtualization that would not > allow that. Should we mandate that P2P memory be in its own MR? I can't say I understand these issues... Logan