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=-17.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 9961BC4320A for ; Thu, 19 Aug 2021 09:03:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BA5C61028 for ; Thu, 19 Aug 2021 09:03:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235642AbhHSJEB (ORCPT ); Thu, 19 Aug 2021 05:04:01 -0400 Received: from foss.arm.com ([217.140.110.172]:33362 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229804AbhHSJDy (ORCPT ); Thu, 19 Aug 2021 05:03:54 -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 312251FB; Thu, 19 Aug 2021 02:03:18 -0700 (PDT) Received: from [10.57.36.146] (unknown [10.57.36.146]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E5C243F66F; Thu, 19 Aug 2021 02:03:16 -0700 (PDT) Subject: Re: [PATCH v6 7/7] dma-iommu: account for min_align_mask To: David Stevens , Christoph Hellwig Cc: Joerg Roedel , Will Deacon , Lu Baolu , Tom Murphy , iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20210817013852.3222824-1-stevensd@google.com> <20210817013852.3222824-8-stevensd@google.com> From: Robin Murphy Message-ID: Date: Thu, 19 Aug 2021 10:03:09 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210817013852.3222824-8-stevensd@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021-08-17 02:38, David Stevens wrote: > From: David Stevens > > For devices which set min_align_mask, swiotlb preserves the offset of > the original physical address within that mask. Since __iommu_dma_map > accounts for non-aligned addresses, passing a non-aligned swiotlb > address with the swiotlb aligned size results in the offset being > accounted for twice in the size passed to iommu_map_atomic. The extra > page exposed to DMA is also not cleaned up by __iommu_dma_unmap, since > that function unmaps with the correct size. This causes mapping failures > if the iova gets reused, due to collisions in the iommu page tables. > > To fix this, pass the original size to __iommu_dma_map, since that > function already handles alignment. > > Additionally, when swiotlb returns non-aligned addresses, there is > padding at the start of the bounce buffer that needs to be cleared. > > Fixes: 1f221a0d0dbf ("swiotlb: respect min_align_mask") > Signed-off-by: David Stevens > --- > drivers/iommu/dma-iommu.c | 24 +++++++++++++----------- > 1 file changed, 13 insertions(+), 11 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 6738420fc081..f2fb360c2907 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -788,7 +788,6 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > struct iommu_domain *domain = iommu_get_dma_domain(dev); > struct iommu_dma_cookie *cookie = domain->iova_cookie; > struct iova_domain *iovad = &cookie->iovad; > - size_t aligned_size = size; > dma_addr_t iova, dma_mask = dma_get_mask(dev); > > /* > @@ -796,8 +795,8 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > * page aligned, we don't need to use a bounce page. > */ > if (dev_use_swiotlb(dev) && iova_offset(iovad, phys | size)) { > - void *padding_start; > - size_t padding_size; > + void *tlb_start; > + size_t aligned_size, iova_off, mapping_end_off; > > aligned_size = iova_align(iovad, size); > phys = swiotlb_tbl_map_single(dev, phys, size, aligned_size, > @@ -806,23 +805,26 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page, > if (phys == DMA_MAPPING_ERROR) > return DMA_MAPPING_ERROR; > > - /* Cleanup the padding area. */ > - padding_start = phys_to_virt(phys); > - padding_size = aligned_size; > + iova_off = iova_offset(iovad, phys); > + tlb_start = phys_to_virt(phys - iova_off); > > if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) && > (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)) { > - padding_start += size; > - padding_size -= size; > + /* Cleanup the padding area. */ > + mapping_end_off = iova_off + size; > + memset(tlb_start, 0, iova_off); > + memset(tlb_start + mapping_end_off, 0, > + aligned_size - mapping_end_off); > + } else { > + /* Nothing was sync'ed, so clear the whole buffer. */ > + memset(tlb_start, 0, aligned_size); > } > - > - memset(padding_start, 0, padding_size); > } > > if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) > arch_sync_dma_for_device(phys, size, dir); > > - iova = __iommu_dma_map(dev, phys, aligned_size, prot, dma_mask); > + iova = __iommu_dma_map(dev, phys, size, prot, dma_mask); I still don't see how this preserves min_align_mask if it is larger than the IOVA granule (either way this change here does nothing since the first thing __iommu_dma_map() does is iova_align() the size right back anyway). Robin. > if (iova == DMA_MAPPING_ERROR && is_swiotlb_buffer(phys)) > swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs); > return iova; >