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=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 8E043C433FE for ; Mon, 13 Sep 2021 08:22:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7453360FC0 for ; Mon, 13 Sep 2021 08:22:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237945AbhIMIXS (ORCPT ); Mon, 13 Sep 2021 04:23:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45888 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234575AbhIMIXQ (ORCPT ); Mon, 13 Sep 2021 04:23:16 -0400 Received: from mail-yb1-xb2d.google.com (mail-yb1-xb2d.google.com [IPv6:2607:f8b0:4864:20::b2d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8E48AC061574 for ; Mon, 13 Sep 2021 01:22:01 -0700 (PDT) Received: by mail-yb1-xb2d.google.com with SMTP id y16so18822799ybm.3 for ; Mon, 13 Sep 2021 01:22:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=hA5SjJKuJahGLX31luP7D8mzJxDC+SO2vk0Mq3zJOdo=; b=AoG98t+mNqkfbrBywtW3MJma5qtkX/dgD6g7VOb+c5S1n0FjUnL6yOa9luwzbDC0MB NnE4WQDAKNb7Je59De5Z5Z9iZwATFiDUbv4xqPOuTLfNgLnIZEiJWmT2uFI8AESauw1f PMZNUSu1450/2jJTr/yR85ZtWx7ev71h29DEQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=hA5SjJKuJahGLX31luP7D8mzJxDC+SO2vk0Mq3zJOdo=; b=hwDThg5v09ik6JlsvwSAJQOvhFS7lkUK7D1h4JTws8ikV3NLXFxO/FZfS1vcTIsXVS e8ESTY8YOIK3kIqgXLgQEdJreq9Iun+PpABdNN8so5Pkw0x4MyzFFpRPbkdCf9q7Noe/ 5XYVh2zqzWSuhaBn6khR+vksmkp/3Iolq3RENDc8B5Ot0l76A40jwCUxgB97YLAWlVcI nF+ffVC6cEmamu6F6pqs/J7hwHLn0XpH89xlykqgF2NUKoT5oUyqV67VAqIADo1aWDj5 le0+UqRkPKFFs7Jf+OYSvB/PAikTc6HDdgA6om3szG8pIBrlPCwgNnyQlRjF2Xtu/hHb 0MtQ== X-Gm-Message-State: AOAM532srWrBydWQLl+qY82xcEJaGWJrV7Gpv+hns5xE3FpyDsLqIkaG ZlL1YRov9T/uzVXiGc3Jm6sp5CAMOHRs8DYEn0JP1rLfiUw= X-Google-Smtp-Source: ABdhPJyoIJv0HVf8WwdAxbVU4oGBg51HU76Y7j3Y3KgW0hMXTKS5AxkYn5ltcrEHX348TDlPO+2cPincRl0pRPxOhOo= X-Received: by 2002:a25:a522:: with SMTP id h31mr14948997ybi.355.1631521320765; Mon, 13 Sep 2021 01:22:00 -0700 (PDT) MIME-Version: 1.0 References: <20210830045925.4163412-1-stevensd@google.com> In-Reply-To: <20210830045925.4163412-1-stevensd@google.com> From: David Stevens Date: Mon, 13 Sep 2021 17:21:49 +0900 Message-ID: Subject: Re: [PATCH v7 0/7] Fixes for dma-iommu swiotlb bounce buffers To: Robin Murphy , Christoph Hellwig Cc: Joerg Roedel , Will Deacon , Lu Baolu , Tom Murphy , Rajat Jain , iommu@lists.linux-foundation.org, open list , David Stevens Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Is there further feedback on these patches? Only patch 7 is still pending review. -David On Mon, Aug 30, 2021 at 2:00 PM David Stevens wrote: > > This patch set includes various fixes for dma-iommu's swiotlb bounce > buffers for untrusted devices. > > The min_align_mask issue was found when running fio on an untrusted nvme > device with bs=512. The other issues were found via code inspection, so > I don't have any specific use cases where things were not working, nor > any concrete performance numbers. > > There are two issues related to min_align_mask that this patch series > does not attempt to fix. First, it does not address the case where > min_align_mask is larger than the IOVA granule. Doing so requires > changes to IOVA allocation, and is not specific to when swiotlb bounce > buffers are used. This is not a problem in practice today, since the > only driver which uses min_align_mask is nvme, which sets it to 4096. > > The second issue this series does not address is the fact that extra > swiotlb slots adjacent to a bounce buffer can be exposed to untrusted > devices whose drivers use min_align_mask. Fixing this requires being > able to allocate padding slots at the beginning of a swiotlb allocation. > This is a rather significant change that I am not comfortable making. > Without being able to handle this, there is also little point to > clearing the padding at the start of such a buffer, since we can only > clear based on (IO_TLB_SIZE - 1) instead of iova_mask. > > v6 -> v7: > - Remove unsafe attempt to clear padding at start of swiotlb buffer > - Rewrite commit message for min_align_mask commit to better explain > the problem it's fixing > - Rebase on iommu/core > - Acknowledge unsolved issues in cover letter > > v5 -> v6: > - Remove unnecessary line break > - Remove redundant config check > > v4 -> v5: > - Fix xen build error > - Move _swiotlb refactor into its own patch > > v3 -> v4: > - Fold _swiotlb functions into _page functions > - Add patch to align swiotlb buffer to iovad granule > - Combine if checks in iommu_dma_sync_sg_* functions > > v2 -> v3: > - Add new patch to address min_align_mask bug > - Set SKIP_CPU_SYNC flag after syncing in map/unmap > - Properly call arch_sync_dma_for_cpu in iommu_dma_sync_sg_for_cpu > > v1 -> v2: > - Split fixes into dedicated patches > - Less invasive changes to fix arch_sync when mapping > - Leave dev_is_untrusted check for strict iommu > > David Stevens (7): > dma-iommu: fix sync_sg with swiotlb > dma-iommu: fix arch_sync_dma for map > dma-iommu: skip extra sync during unmap w/swiotlb > dma-iommu: fold _swiotlb helpers into callers > dma-iommu: Check CONFIG_SWIOTLB more broadly > swiotlb: support aligned swiotlb buffers > dma-iommu: account for min_align_mask w/swiotlb > > drivers/iommu/dma-iommu.c | 188 +++++++++++++++++--------------------- > drivers/xen/swiotlb-xen.c | 2 +- > include/linux/swiotlb.h | 3 +- > kernel/dma/swiotlb.c | 11 ++- > 4 files changed, 93 insertions(+), 111 deletions(-) > > -- > 2.33.0.259.gc128427fd7-goog >