Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757242AbcKXQ02 (ORCPT ); Thu, 24 Nov 2016 11:26:28 -0500 Received: from quartz.orcorp.ca ([184.70.90.242]:42017 "EHLO quartz.orcorp.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756864AbcKXQ0Z (ORCPT ); Thu, 24 Nov 2016 11:26:25 -0500 Date: Thu, 24 Nov 2016 09:26:20 -0700 From: Jason Gunthorpe To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: Dan Williams , 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" , "Sander, Ben" , "Suthikulpanit, Suravee" , "Blinzer, Paul" , "Linux-media@vger.kernel.org" , Haggai Eran Subject: Re: Enabling peer to peer device transactions for PCIe devices Message-ID: <20161124162620.GC20818@obsidianresearch.com> References: <20161123190515.GA12146@obsidianresearch.com> <7bc38037-b6ab-943f-59db-6280e16901ab@amd.com> <20161123193228.GC12146@obsidianresearch.com> <20161123203332.GA15062@obsidianresearch.com> <20161123215510.GA16311@obsidianresearch.com> <20161123232503.GA13965@obsidianresearch.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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: 666 Lines: 14 On Thu, Nov 24, 2016 at 10:45:18AM +0100, Christian K?nig wrote: > Am 24.11.2016 um 00:25 schrieb Jason Gunthorpe: > >There is certainly nothing about the hardware that cares > >about ZONE_DEVICE vs System memory. > Well that is clearly not so simple. When your ZONE_DEVICE pages describe a > PCI BAR and another PCI device initiates a DMA to this address the DMA > subsystem must be able to check if the interconnection really works. I said the hardware doesn't care.. You are right, we still have an outstanding problem in Linux of how to generically DMA map a P2P address - which is a different issue from getting the P2P address from a __user pointer... Jason