From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pegase2.c-s.fr (pegase2.c-s.fr [93.17.235.10]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 80AE01A8F6D; Thu, 14 Aug 2025 19:20:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=93.17.235.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755199237; cv=none; b=hCQBX8dqxDcSRklEdwrWHo49s7BSo6oEkMoy1eZcW7/UsEMsgylBdv4PhOclnr1IdHPm1F5tHbqPJpqXd97ue4PS3hJN9KAPg8mW+OR/6WC5XNNo8Vz+BJI37uU0ADL96mvbXd+C2s9tIHCQlOZaea8lEPaKXcESQcWJQ+NWLXY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755199237; c=relaxed/simple; bh=rD5JabdEJRljG8IExvrHN7NV5kOpcnQhHxBq2nt80PY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=L81okwSCj3rkG/5c8GHqLCtvldBn0OlxvG1eJe72n3de+vbH5uuAaFvd7u+Fsn5C+8BZZk2bLunLAJSbXS+bap/5oCjMTnvaPmlmvQsosQFZKiF7y5KSUhYG1iU3JWW6eclqy1ITe7GSdnqDvCjxv8g4m+4HReLcNfk3i0TUa24= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu; spf=pass smtp.mailfrom=csgroup.eu; arc=none smtp.client-ip=93.17.235.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=csgroup.eu Received: from localhost (mailhub4.si.c-s.fr [172.26.127.67]) by localhost (Postfix) with ESMTP id 4c2vpK65M9z9sSH; Thu, 14 Aug 2025 21:05:45 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase2.c-s.fr ([172.26.127.65]) by localhost (pegase2.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ZPu83EvDtL2B; Thu, 14 Aug 2025 21:05:45 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase2.c-s.fr (Postfix) with ESMTP id 4c2vpK3P9dz9sSC; Thu, 14 Aug 2025 21:05:45 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 16AD08B764; Thu, 14 Aug 2025 21:05:45 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id v81OkG88qzZ0; Thu, 14 Aug 2025 21:05:44 +0200 (CEST) Received: from [192.168.235.99] (unknown [192.168.235.99]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 592BF8B763; Thu, 14 Aug 2025 21:05:43 +0200 (CEST) Message-ID: Date: Thu, 14 Aug 2025 21:05:42 +0200 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 00/16] dma-mapping: migrate to physical address-based API To: Leon Romanovsky , Marek Szyprowski Cc: Jason Gunthorpe , Abdiel Janulgue , Alexander Potapenko , Alex Gaynor , Andrew Morton , Christoph Hellwig , Danilo Krummrich , iommu@lists.linux.dev, Jason Wang , Jens Axboe , Joerg Roedel , Jonathan Corbet , Juergen Gross , kasan-dev@googlegroups.com, Keith Busch , linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nvme@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-trace-kernel@vger.kernel.org, Madhavan Srinivasan , Masami Hiramatsu , Michael Ellerman , "Michael S. Tsirkin" , Miguel Ojeda , Robin Murphy , rust-for-linux@vger.kernel.org, Sagi Grimberg , Stefano Stabellini , Steven Rostedt , virtualization@lists.linux.dev, Will Deacon , xen-devel@lists.xenproject.org References: From: Christophe Leroy Content-Language: fr-FR In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Le 14/08/2025 à 19:53, Leon Romanovsky a écrit : > Changelog: > v3: > * Fixed typo in "cacheable" word > * Simplified kmsan patch a lot to be simple argument refactoring v2 sent today at 12:13, v3 sent today at 19:53 .... for only that ? Have you read https://docs.kernel.org//process/submitting-patches.html#don-t-get-discouraged-or-impatient ? Thanks Christophe > v2: https://lore.kernel.org/all/cover.1755153054.git.leon@kernel.org > * Used commit messages and cover letter from Jason > * Moved setting IOMMU_MMIO flag to dma_info_to_prot function > * Micro-optimized the code > * Rebased code on v6.17-rc1 > v1: https://lore.kernel.org/all/cover.1754292567.git.leon@kernel.org > * Added new DMA_ATTR_MMIO attribute to indicate > PCI_P2PDMA_MAP_THRU_HOST_BRIDGE path. > * Rewrote dma_map_* functions to use thus new attribute > v0: https://lore.kernel.org/all/cover.1750854543.git.leon@kernel.org/ > ------------------------------------------------------------------------ > > This series refactors the DMA mapping to use physical addresses > as the primary interface instead of page+offset parameters. This > change aligns the DMA API with the underlying hardware reality where > DMA operations work with physical addresses, not page structures. > > The series maintains export symbol backward compatibility by keeping > the old page-based API as wrapper functions around the new physical > address-based implementations. > > This series refactors the DMA mapping API to provide a phys_addr_t > based, and struct-page free, external API that can handle all the > mapping cases we want in modern systems: > > - struct page based cachable DRAM > - struct page MEMORY_DEVICE_PCI_P2PDMA PCI peer to peer non-cachable > MMIO > - struct page-less PCI peer to peer non-cachable MMIO > - struct page-less "resource" MMIO > > Overall this gets much closer to Matthew's long term wish for > struct-pageless IO to cachable DRAM. The remaining primary work would > be in the mm side to allow kmap_local_pfn()/phys_to_virt() to work on > phys_addr_t without a struct page. > > The general design is to remove struct page usage entirely from the > DMA API inner layers. For flows that need to have a KVA for the > physical address they can use kmap_local_pfn() or phys_to_virt(). This > isolates the struct page requirements to MM code only. Long term all > removals of struct page usage are supporting Matthew's memdesc > project which seeks to substantially transform how struct page works. > > Instead make the DMA API internals work on phys_addr_t. Internally > there are still dedicated 'page' and 'resource' flows, except they are > now distinguished by a new DMA_ATTR_MMIO instead of by callchain. Both > flows use the same phys_addr_t. > > When DMA_ATTR_MMIO is specified things work similar to the existing > 'resource' flow. kmap_local_pfn(), phys_to_virt(), phys_to_page(), > pfn_valid(), etc are never called on the phys_addr_t. This requires > rejecting any configuration that would need swiotlb. CPU cache > flushing is not required, and avoided, as ATTR_MMIO also indicates the > address have no cachable mappings. This effectively removes any > DMA API side requirement to have struct page when DMA_ATTR_MMIO is > used. > > In the !DMA_ATTR_MMIO mode things work similarly to the 'page' flow, > except on the common path of no cache flush, no swiotlb it never > touches a struct page. When cache flushing or swiotlb copying > kmap_local_pfn()/phys_to_virt() are used to get a KVA for CPU > usage. This was already the case on the unmap side, now the map side > is symmetric. > > Callers are adjusted to set DMA_ATTR_MMIO. Existing 'resource' users > must set it. The existing struct page based MEMORY_DEVICE_PCI_P2PDMA > path must also set it. This corrects some existing bugs where iommu > mappings for P2P MMIO were improperly marked IOMMU_CACHE. > > Since ATTR_MMIO is made to work with all the existing DMA map entry > points, particularly dma_iova_link(), this finally allows a way to use > the new DMA API to map PCI P2P MMIO without creating struct page. The > VFIO DMABUF series demonstrates how this works. This is intended to > replace the incorrect driver use of dma_map_resource() on PCI BAR > addresses. > > This series does the core code and modern flows. A followup series > will give the same treatment to the legacy dma_ops implementation. > > Thanks > > Leon Romanovsky (16): > dma-mapping: introduce new DMA attribute to indicate MMIO memory > iommu/dma: implement DMA_ATTR_MMIO for dma_iova_link(). > dma-debug: refactor to use physical addresses for page mapping > dma-mapping: rename trace_dma_*map_page to trace_dma_*map_phys > iommu/dma: rename iommu_dma_*map_page to iommu_dma_*map_phys > iommu/dma: extend iommu_dma_*map_phys API to handle MMIO memory > dma-mapping: convert dma_direct_*map_page to be phys_addr_t based > kmsan: convert kmsan_handle_dma to use physical addresses > dma-mapping: handle MMIO flow in dma_map|unmap_page > xen: swiotlb: Open code map_resource callback > dma-mapping: export new dma_*map_phys() interface > mm/hmm: migrate to physical address-based DMA mapping API > mm/hmm: properly take MMIO path > block-dma: migrate to dma_map_phys instead of map_page > block-dma: properly take MMIO path > nvme-pci: unmap MMIO pages with appropriate interface > > Documentation/core-api/dma-api.rst | 4 +- > Documentation/core-api/dma-attributes.rst | 18 ++++ > arch/powerpc/kernel/dma-iommu.c | 4 +- > block/blk-mq-dma.c | 15 ++- > drivers/iommu/dma-iommu.c | 61 +++++------ > drivers/nvme/host/pci.c | 18 +++- > drivers/virtio/virtio_ring.c | 4 +- > drivers/xen/swiotlb-xen.c | 21 +++- > include/linux/blk-mq-dma.h | 6 +- > include/linux/blk_types.h | 2 + > include/linux/dma-direct.h | 2 - > include/linux/dma-map-ops.h | 8 +- > include/linux/dma-mapping.h | 33 ++++++ > include/linux/iommu-dma.h | 11 +- > include/linux/kmsan.h | 9 +- > include/trace/events/dma.h | 9 +- > kernel/dma/debug.c | 71 ++++--------- > kernel/dma/debug.h | 37 ++----- > kernel/dma/direct.c | 22 +--- > kernel/dma/direct.h | 52 ++++++---- > kernel/dma/mapping.c | 117 +++++++++++++--------- > kernel/dma/ops_helpers.c | 6 +- > mm/hmm.c | 19 ++-- > mm/kmsan/hooks.c | 7 +- > rust/kernel/dma.rs | 3 + > tools/virtio/linux/kmsan.h | 2 +- > 26 files changed, 306 insertions(+), 255 deletions(-) >