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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 55A75C624D0 for ; Wed, 2 Sep 2026 10:59:27 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id B6AC710F114; Wed, 2 Sep 2026 10:59:26 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="RyOKoEmb"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7F12610F114 for ; Wed, 2 Sep 2026 10:59:25 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 8A9DA600C8; Wed, 2 Sep 2026 10:59:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9E4C91F000E9; Wed, 2 Sep 2026 10:59:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788346764; bh=OBVmQw0sO4Pqp+7c+CugRQe5Vt/ZmRFWAeUf3jC3dWA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=RyOKoEmbZeg1aphhoTTpEaSIx8jXa6UWfDyctpucawNu6Z8Z3QEFvG+aAQiX5811Q UhaExyceGBB/5wIot7ioceNrrpzg0hJOhDlHLxle+yiT6zHlJlKqEtrq/LFGvcRbu/ bU4B4iQMLzRRiczAfE8WSQLzCOBAmES3EPeT+pvdv65HRWkWrKSlkwQguvv6M/Snai nEkEca7YfmhKCToruciCfWidpSlY3S01HOhHZyrCJ0+g8Hz2eMDMUqDiN1qiEbrkwB NdnTFIO5Kz0F8tVGTocGnZYK2DRb6d4NmBy0ufnb4yXJDSQX5jUtHXv6a5Qb1qqnCG t9/dRhGdQCAHg== Date: Wed, 2 Sep 2026 13:59:19 +0300 From: Leon Romanovsky To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: David Hu , sumit.semwal@linaro.org, alex@shazbot.org, ankita@nvidia.com, chriscli@google.com, david.laight.linux@gmail.com, dri-devel@lists.freedesktop.org, iommu@lists.linux.dev, jgg@ziepe.ca, jmoroni@google.com, kevin.tian@intel.com, kpberry@google.com, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, nicolinc@nvidia.com, praan@google.com, sashiko-bot@kernel.org, stable@vger.kernel.org, viursachi@google.com, xuehaohu@google.com Subject: Re: [PATCH v8 0/2] dma-buf: Fix silent overflow and alignment Message-ID: <20260902105919.GV24140@unreal> References: <20260901170849.4052816-1-dhu@x6u.co> <2bf581db-7cc5-4f38-a075-1b988c332f3c@amd.com> <20260902073936.GR24140@unreal> <20260902083232.GT24140@unreal> <20260902095338.GU24140@unreal> <65dc4ca1-6882-490d-baad-3e0abd708af3@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <65dc4ca1-6882-490d-baad-3e0abd708af3@amd.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Wed, Sep 02, 2026 at 12:00:25PM +0200, Christian König wrote: > On 9/2/26 11:53, Leon Romanovsky wrote: > > On Wed, Sep 02, 2026 at 10:44:59AM +0200, Christian König wrote: > >> On 9/2/26 10:32, Leon Romanovsky wrote: > >>> On Wed, Sep 02, 2026 at 09:56:06AM +0200, Christian König wrote: > >>>> On 9/2/26 09:39, Leon Romanovsky wrote: > >>>>> On Wed, Sep 02, 2026 at 09:00:46AM +0200, Christian König wrote: > >>>>>> On 9/1/26 19:08, David Hu wrote: > >>>>>>> From: David Hu > >>>>>>> > >>>>>>> This series address two related issues in scatter-gather mapping, > >>>>>>> specifically for the MMIO based dma-buf mapping. The fixes ensure > >>>>>>> sgt mapping is correct, and proper for large MMIO regions. > >>>>>>> > >>>>>>> Patch 1 fixes a silent integer overflow for mapping length exceeding 4G > >>>>>>> (Previously submitted as [PATCH v7] dma-buf: Fix silent overflow for > >>>>>>> phys vec to sgt) > >>>>>>> https://lore.kernel.org/all/20260609164047.486227-1-xuehaohu@google.com/ > >>>>>>> > >>>>>>> Patch 2 Splits sgl by largest page aligned chunk > >>>>>>> (Previously submitted as [PATCH v3] dma-buf: Split sgl by largest page-aligned chunk) > >>>>>>> https://lore.kernel.org/all/20260722233806.3922093-1-dhu@x6u.co/ > >>>>>> > >>>>>> *sigh* such issues are exactly the reason why I didn't wanted the dma-mapping stuff inside DMA-buf. That clearly doesn't belong here. > >>>>> > >>>>> And this is why so many in the kernel community want to get rid of SG > >>>>> lists. It would be great if DMA-BUF could also eliminate the need to > >>>>> convert to an SGL, like Jason proposed. > >>>>> > >>>>> The DMA layer no longer needs SGL. These bugs belong to the DMA-BUF layer, > >>>>> which is the one that depends on it. > >>>> > >>>> I'm all fine using an array/xarray of dma_addr_t in DMA-buf, just phys_vec is a clear no-go. > >>> > >>> You are proposing the same thing as an SGL, just in a different format. > >> > >> Yes, because that is the right thing todo as far as I can see. > >> > >>> It does not address the issue that dma_addr_t is expected to hold a DMA > >>> address, while that is not always the case. For example, in the P2P case, > >>> the addresses are not DMA addresses. > >> > >> Yes they are. They must be DMA addresses because that is the only thing the importer needs to do it's DMA. > > > > They can perform DMA, but that still does not make them suitable for the > > dma_addr_t type. For the PCI_P2PDMA_MAP_BUS_ADDR flow, these addresses > > follow completely different rules: they are not unmapped, require no cache > > synchronization, are valid only for peer access, and require separate error > > handling. > > The PCI_P2PDMA_MAP_BUS_ADDR is not supported by DMA-buf and as far as I can see is a complete dead end. Maybe you mean DRM, but VFIO works perfectly with PCI_P2PDMA_MAP_BUS_ADDR flow in DMA-buf. What am I missing? Thanks