From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06379C76190 for ; Thu, 25 Jul 2019 19:17:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DC9B4214AE for ; Thu, 25 Jul 2019 19:17:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726797AbfGYTRR (ORCPT ); Thu, 25 Jul 2019 15:17:17 -0400 Received: from ale.deltatee.com ([207.54.116.67]:42248 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726736AbfGYTRR (ORCPT ); Thu, 25 Jul 2019 15:17:17 -0400 Received: from s01061831bf6ec98c.cg.shawcable.net ([68.147.80.180] helo=[192.168.6.132]) by ale.deltatee.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.89) (envelope-from ) id 1hqjEe-0003mV-J9; Thu, 25 Jul 2019 13:17:05 -0600 To: Jason Gunthorpe Cc: "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-rdma@vger.kernel.org" , Bjorn Helgaas , Christoph Hellwig , Christian Koenig , Sagi Grimberg , Keith Busch , Jens Axboe , Dan Williams , Eric Pilmore , Stephen Bates References: <20190722230859.5436-1-logang@deltatee.com> <20190722230859.5436-12-logang@deltatee.com> <20190725185830.GH7450@mellanox.com> From: Logan Gunthorpe Message-ID: Date: Thu, 25 Jul 2019 13:17:02 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190725185830.GH7450@mellanox.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 68.147.80.180 X-SA-Exim-Rcpt-To: sbates@raithlin.com, epilmore@gigaio.com, dan.j.williams@intel.com, axboe@fb.com, kbusch@kernel.org, sagi@grimberg.me, Christian.Koenig@amd.com, hch@lst.de, bhelgaas@google.com, linux-rdma@vger.kernel.org, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, jgg@mellanox.com X-SA-Exim-Mail-From: logang@deltatee.com Subject: Re: [PATCH 11/14] PCI/P2PDMA: dma_map P2PDMA map requests that traverse the host bridge 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-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 2019-07-25 12:58 p.m., Jason Gunthorpe wrote: > On Mon, Jul 22, 2019 at 05:08:56PM -0600, Logan Gunthorpe wrote: >> Any requests that traverse the host bridge will need to be mapped into >> the IOMMU, so call dma_map_sg() inside pci_p2pdma_map_sg() when >> appropriate. >> >> Similarly, call dma_unmap_sg() inside pci_p2pdma_unmap_sg(). >> >> Signed-off-by: Logan Gunthorpe >> drivers/pci/p2pdma.c | 31 ++++++++++++++++++++++++++++++- >> 1 file changed, 30 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c >> index 5f43f92f9336..76f51678342c 100644 >> +++ b/drivers/pci/p2pdma.c >> @@ -830,8 +830,22 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg, >> int nents, enum dma_data_direction dir, unsigned long attrs) >> { >> struct dev_pagemap *pgmap = sg_page(sg)->pgmap; >> + struct pci_dev *client; >> + int dist; >> + >> + client = find_parent_pci_dev(dev); >> + if (WARN_ON_ONCE(!client)) >> + return 0; >> >> - return __pci_p2pdma_map_sg(pgmap, dev, sg, nents); >> + dist = upstream_bridge_distance(pgmap->pci_p2pdma_provider, >> + client, NULL); >> + if (WARN_ON_ONCE(dist & P2PDMA_NOT_SUPPORTED)) >> + return 0; >> + >> + if (dist & P2PDMA_THRU_HOST_BRIDGE) >> + return dma_map_sg_attrs(dev, sg, nents, dir, attrs); > > IIRC at this point the SG will have struct page references to the BAR > memory - so (all?) the IOMMU drivers are able to handle P2P setup in > this case? Yes. The IOMMU drivers refer to the physical address for BAR which they can get from the struct page. And this works fine today. > Didn't you also have a patch to remove the struct page's for the BAR > memory? Well that was an RFC that's not going anywhere in it's current form. I'd still like to remove struct pages but that's going to take a while and when that happens, this will have to be reworked. Probably to use dma_map_resource() instead but will depend on the form the removal takes. Logan