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=-12.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 027F0C433E1 for ; Wed, 26 Aug 2020 18:14:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D568C2083B for ; Wed, 26 Aug 2020 18:14:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726765AbgHZSOi (ORCPT ); Wed, 26 Aug 2020 14:14:38 -0400 Received: from foss.arm.com ([217.140.110.172]:49688 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726241AbgHZSOh (ORCPT ); Wed, 26 Aug 2020 14:14:37 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EF4DA101E; Wed, 26 Aug 2020 11:14:36 -0700 (PDT) Received: from [10.57.40.122] (unknown [10.57.40.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6133E3F71F; Wed, 26 Aug 2020 11:14:31 -0700 (PDT) Subject: Re: [PATCH 0/8] Convert the intel iommu driver to the dma-iommu api To: Tom Murphy , iommu@lists.linux-foundation.org Cc: Heiko Stuebner , kvm@vger.kernel.org, David Airlie , Joonas Lahtinen , dri-devel@lists.freedesktop.org, Bjorn Andersson , linux-tegra@vger.kernel.org, Julien Grall , Thierry Reding , Will Deacon , Jean-Philippe Brucker , linux-samsung-soc@vger.kernel.org, Marc Zyngier , Krzysztof Kozlowski , Jonathan Hunter , linux-rockchip@lists.infradead.org, Andy Gross , linux-arm-kernel@lists.infradead.org, linux-s390@vger.kernel.org, linux-arm-msm@vger.kernel.org, intel-gfx@lists.freedesktop.org, Jani Nikula , Alex Williamson , linux-mediatek@lists.infradead.org, Rodrigo Vivi , Matthias Brugger , Thomas Gleixner , virtualization@lists.linux-foundation.org, Gerald Schaefer , David Woodhouse , Cornelia Huck , linux-kernel@vger.kernel.org, Kukjin Kim , Daniel Vetter References: <20191221150402.13868-1-murphyt7@tcd.ie> From: Robin Murphy Message-ID: <03caf286-09e8-a072-8d3a-b6bcca991516@arm.com> Date: Wed, 26 Aug 2020 19:14:28 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20191221150402.13868-1-murphyt7@tcd.ie> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi Tom, On 2019-12-21 15:03, Tom Murphy wrote: > This patchset converts the intel iommu driver to the dma-iommu api. > > While converting the driver I exposed a bug in the intel i915 driver which causes a huge amount of artifacts on the screen of my laptop. You can see a picture of it here: > https://github.com/pippy360/kernelPatches/blob/master/IMG_20191219_225922.jpg > > This issue is most likely in the i915 driver and is most likely caused by the driver not respecting the return value of the dma_map_ops::map_sg function. You can see the driver ignoring the return value here: > https://github.com/torvalds/linux/blob/7e0165b2f1a912a06e381e91f0f4e495f4ac3736/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c#L51 > > Previously this didn’t cause issues because the intel map_sg always returned the same number of elements as the input scatter gather list but with the change to this dma-iommu api this is no longer the case. I wasn’t able to track the bug down to a specific line of code unfortunately. > > Could someone from the intel team look at this? > > > I have been testing on a lenovo x1 carbon 5th generation. Let me know if there’s any more information you need. > > To allow my patch set to be tested I have added a patch (patch 8/8) in this series to disable combining sg segments in the dma-iommu api which fixes the bug but it doesn't fix the actual problem. > > As part of this patch series I copied the intel bounce buffer code to the dma-iommu path. The addition of the bounce buffer code took me by surprise. I did most of my development on this patch series before the bounce buffer code was added and my reimplementation in the dma-iommu path is very rushed and not properly tested but I’m running out of time to work on this patch set. > > On top of that I also didn’t port over the intel tracing code from this commit: > https://github.com/torvalds/linux/commit/3b53034c268d550d9e8522e613a14ab53b8840d8#diff-6b3e7c4993f05e76331e463ab1fc87e1 > So all the work in that commit is now wasted. The code will need to be removed and reimplemented in the dma-iommu path. I would like to take the time to do this but I really don’t have the time at the moment and I want to get these changes out before the iommu code changes any more. Further to what we just discussed at LPC, I've realised that tracepoints are actually something I could do with *right now* for debugging my Arm DMA ops series, so if I'm going to hack something up anyway I may as well take responsibility for polishing it into a proper patch as well :) Robin. > > Tom Murphy (8): > iommu/vt-d: clean up 32bit si_domain assignment > iommu/vt-d: Use default dma_direct_* mapping functions for direct > mapped devices > iommu/vt-d: Remove IOVA handling code from non-dma_ops path > iommu: Handle freelists when using deferred flushing in iommu drivers > iommu: Add iommu_dma_free_cpu_cached_iovas function > iommu: allow the dma-iommu api to use bounce buffers > iommu/vt-d: Convert intel iommu driver to the iommu ops > DO NOT MERGE: iommu: disable list appending in dma-iommu > > drivers/iommu/Kconfig | 1 + > drivers/iommu/amd_iommu.c | 14 +- > drivers/iommu/arm-smmu-v3.c | 3 +- > drivers/iommu/arm-smmu.c | 3 +- > drivers/iommu/dma-iommu.c | 183 +++++-- > drivers/iommu/exynos-iommu.c | 3 +- > drivers/iommu/intel-iommu.c | 936 ++++---------------------------- > drivers/iommu/iommu.c | 39 +- > drivers/iommu/ipmmu-vmsa.c | 3 +- > drivers/iommu/msm_iommu.c | 3 +- > drivers/iommu/mtk_iommu.c | 3 +- > drivers/iommu/mtk_iommu_v1.c | 3 +- > drivers/iommu/omap-iommu.c | 3 +- > drivers/iommu/qcom_iommu.c | 3 +- > drivers/iommu/rockchip-iommu.c | 3 +- > drivers/iommu/s390-iommu.c | 3 +- > drivers/iommu/tegra-gart.c | 3 +- > drivers/iommu/tegra-smmu.c | 3 +- > drivers/iommu/virtio-iommu.c | 3 +- > drivers/vfio/vfio_iommu_type1.c | 2 +- > include/linux/dma-iommu.h | 3 + > include/linux/intel-iommu.h | 1 - > include/linux/iommu.h | 32 +- > 23 files changed, 345 insertions(+), 908 deletions(-) >