From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161352AbeCATeP (ORCPT ); Thu, 1 Mar 2018 14:34:15 -0500 Received: from ale.deltatee.com ([207.54.116.67]:37762 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161195AbeCATeJ (ORCPT ); Thu, 1 Mar 2018 14:34:09 -0500 To: Sagi Grimberg , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org, linux-nvdimm@lists.01.org, linux-block@vger.kernel.org Cc: Stephen Bates , Christoph Hellwig , Jens Axboe , Keith Busch , Bjorn Helgaas , Jason Gunthorpe , Max Gurtovoy , Dan Williams , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Benjamin Herrenschmidt , Alex Williamson References: <20180228234006.21093-1-logang@deltatee.com> <90b658d9-da8a-af36-ad8f-a72ef0c6e3c1@grimberg.me> From: Logan Gunthorpe Message-ID: <112b6d99-8aac-3d45-486e-ebea62fb8670@deltatee.com> Date: Thu, 1 Mar 2018 12:33:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <90b658d9-da8a-af36-ad8f-a72ef0c6e3c1@grimberg.me> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 172.16.1.162 X-SA-Exim-Rcpt-To: alex.williamson@redhat.com, benh@kernel.crashing.org, jglisse@redhat.com, dan.j.williams@intel.com, maxg@mellanox.com, jgg@mellanox.com, bhelgaas@google.com, keith.busch@intel.com, axboe@kernel.dk, hch@lst.de, sbates@raithlin.com, linux-block@vger.kernel.org, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, sagi@grimberg.me X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH v2 00/10] Copy Offload in NVMe Fabrics with P2P PCI Memory X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +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 On 01/03/18 03:31 AM, Sagi Grimberg wrote: >> * We also reject using devices that employ 'dma_virt_ops' which should >>    fairly simply handle Jason's concerns that this work might break with >>    the HFI, QIB and rxe drivers that use the virtual ops to implement >>    their own special DMA operations. > > That's good, but what would happen for these devices? simply fail the > mapping causing the ulp to fail its rdma operation? I would think > that we need a capability flag for devices that support it. pci_p2pmem_find() will simply not return any devices when any client that uses dma_virt_ops. So in the NVMe target case it simply will not use P2P memory. And just in case, pci_p2pdma_map_sg() will also return 0 if the device passed to it uses dma_virt_ops as well. So if someone bypasses pci_p2pmem_find() they will get a failure during map. Logan