Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933364AbcKWTMY (ORCPT ); Wed, 23 Nov 2016 14:12:24 -0500 Received: from quartz.orcorp.ca ([184.70.90.242]:53308 "EHLO quartz.orcorp.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933122AbcKWTMX (ORCPT ); Wed, 23 Nov 2016 14:12:23 -0500 Date: Wed, 23 Nov 2016 12:12:15 -0700 From: Jason Gunthorpe To: Dan Williams Cc: Bart Van Assche , Logan Gunthorpe , Serguei Sagalovitch , "Deucher, Alexander" , "linux-nvdimm@lists.01.org" , "linux-rdma@vger.kernel.org" , "linux-pci@vger.kernel.org" , "Kuehling, Felix" , "Bridgman, John" , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "Koenig, Christian" , "Sander, Ben" , "Suthikulpanit, Suravee" , "Blinzer, Paul" , "Linux-media@vger.kernel.org" Subject: Re: Enabling peer to peer device transactions for PCIe devices Message-ID: <20161123191215.GB12146@obsidianresearch.com> References: <75a1f44f-c495-7d1e-7e1c-17e89555edba@amd.com> <45c6e878-bece-7987-aee7-0e940044158c@deltatee.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-Broken-Reverse-DNS: no host name found for IP address 10.0.0.151 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 555 Lines: 14 On Wed, Nov 23, 2016 at 10:40:47AM -0800, Dan Williams wrote: > I don't think that was designed for the case where the backing memory > is a special/static physical address range rather than anonymous > "System RAM", right? The hardware doesn't care where the memory is. ODP is just a generic mechanism to provide demand-fault behavior for a mirrored page table. ODP has the same issue as everything else, it needs to translate a page table entry into a DMA address, and we have no API to do that when the page table points to peer-peer memory. Jason