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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 599F9C87FDA for ; Thu, 7 Aug 2025 14:59:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=f/3vSq9381IaXbqW9OZrKrqA9rxmKdWI6yV8YceURS0=; b=JuhKIC/Urx0fSi0ewVGeUCwWyG yL0ZNUDCkXZxdgMjjcF+WBVLr5eKSCpsqQoyE0XnlSEyg3tfQMR7AQHqeQchShKGl2a9EgmNlxfbh YhB0HVAgYsTUVgXSO0Q3nzM6ae7hKClEf3DGM0gIXr9fRkXGaHgwy9HsxEgnoBPn2sKxsTAYL+AGp Zr9iSJNEQH1DG4jDYRNwOswdy/2nI5wElTpQicYR5rSLgNSjaGhAsOMBtySzGWSCjn805CpkWFJS5 4lsoIygjPs8j3jueXM8I2D93e2FWZtcCOsNhxfXRx+dvVvppYFa8rbVmO36KMF2KJUIgWtzDpOvyT 2guEKS6w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uk25o-00000000ttb-2cER; Thu, 07 Aug 2025 14:59:44 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uiuXJ-0000000AOnM-1iAc for linux-nvme@lists.infradead.org; Mon, 04 Aug 2025 12:43:30 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 28A9644938; Mon, 4 Aug 2025 12:43:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96668C4CEF8; Mon, 4 Aug 2025 12:43:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754311409; bh=B6ggJVOQfTYMCOE/nJsgZM614saTj7Qtn55LwfqKBMA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mACwCJwnciJCEbZnCrkOPhfxhxsK8nNGbFRTcuF/UprHjNhigkEBz4Qjo6q3nOYnE NNEuUiRwpxiJJ+5+lJPFbBh1pz1NHdaolrAAyyFd/BDEth7WPdBMjVzrlmdIaxA3Qb 2RsWBm5LtpycB6Eoe6pJbVmXbTVoQjyF0BJrKzZPE5F7UARnqwUUZNfC3023xQAdCk GMv+SVJ7lY8MSINtMTSQNgemwlQgadSRLsUt+7E2s6eroO/rhcn1uAVTTMaXvcyAt7 AFjFAFTQV2Ju8uDUJFNXpQWgxbDaQrFpkFb9ltCXITe4mMxj1t62jvARy38KRhJWAk x4Lll22SY+E5Q== From: Leon Romanovsky To: Marek Szyprowski Cc: Leon Romanovsky , 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 Subject: [PATCH v1 01/16] dma-mapping: introduce new DMA attribute to indicate MMIO memory Date: Mon, 4 Aug 2025 15:42:35 +0300 Message-ID: X-Mailer: git-send-email 2.50.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250804_054329_484496_B0810DAC X-CRM114-Status: GOOD ( 17.59 ) X-Mailman-Approved-At: Thu, 07 Aug 2025 07:59:41 -0700 X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org From: Leon Romanovsky This patch introduces the DMA_ATTR_MMIO attribute to mark DMA buffers that reside in memory-mapped I/O (MMIO) regions, such as device BARs exposed through the host bridge, which are accessible for peer-to-peer (P2P) DMA. This attribute is especially useful for exporting device memory to other devices for DMA without CPU involvement, and avoids unnecessary or potentially detrimental CPU cache maintenance calls. Signed-off-by: Leon Romanovsky --- Documentation/core-api/dma-attributes.rst | 7 +++++++ include/linux/dma-mapping.h | 14 ++++++++++++++ include/trace/events/dma.h | 3 ++- rust/kernel/dma.rs | 3 +++ 4 files changed, 26 insertions(+), 1 deletion(-) diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst index 1887d92e8e926..91acd2684e506 100644 --- a/Documentation/core-api/dma-attributes.rst +++ b/Documentation/core-api/dma-attributes.rst @@ -130,3 +130,10 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged subsystem that the buffer is fully accessible at the elevated privilege level (and ideally inaccessible or at least read-only at the lesser-privileged levels). + +DMA_ATTR_MMIO +------------- + +This attribute is especially useful for exporting device memory to other +devices for DMA without CPU involvement, and avoids unnecessary or +potentially detrimental CPU cache maintenance calls. diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 55c03e5fe8cb3..afc89835c7457 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -58,6 +58,20 @@ */ #define DMA_ATTR_PRIVILEGED (1UL << 9) +/* + * DMA_ATTR_MMIO - Indicates memory-mapped I/O (MMIO) region for DMA mapping + * + * This attribute is used for MMIO memory regions that are exposed through + * the host bridge and are accessible for peer-to-peer (P2P) DMA. Memory + * marked with this attribute is not system RAM and may represent device + * BAR windows or peer-exposed memory. + * + * Typical usage is for mapping hardware memory BARs or exporting device + * memory to other devices for DMA without involving main system RAM. + * The attribute guarantees no CPU cache maintenance calls will be made. + */ +#define DMA_ATTR_MMIO (1UL << 10) + /* * A dma_addr_t can hold any valid DMA or bus address for the platform. It can * be given to a device to use as a DMA source or target. It is specific to a diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h index d8ddc27b6a7c8..ee90d6f1dcf35 100644 --- a/include/trace/events/dma.h +++ b/include/trace/events/dma.h @@ -31,7 +31,8 @@ TRACE_DEFINE_ENUM(DMA_NONE); { DMA_ATTR_FORCE_CONTIGUOUS, "FORCE_CONTIGUOUS" }, \ { DMA_ATTR_ALLOC_SINGLE_PAGES, "ALLOC_SINGLE_PAGES" }, \ { DMA_ATTR_NO_WARN, "NO_WARN" }, \ - { DMA_ATTR_PRIVILEGED, "PRIVILEGED" }) + { DMA_ATTR_PRIVILEGED, "PRIVILEGED" }, \ + { DMA_ATTR_MMIO, "MMIO" }) DECLARE_EVENT_CLASS(dma_map, TP_PROTO(struct device *dev, phys_addr_t phys_addr, dma_addr_t dma_addr, diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs index 2bc8ab51ec280..61d9eed7a786e 100644 --- a/rust/kernel/dma.rs +++ b/rust/kernel/dma.rs @@ -242,6 +242,9 @@ pub mod attrs { /// Indicates that the buffer is fully accessible at an elevated privilege level (and /// ideally inaccessible or at least read-only at lesser-privileged levels). pub const DMA_ATTR_PRIVILEGED: Attrs = Attrs(bindings::DMA_ATTR_PRIVILEGED); + + /// Indicates that the buffer is MMIO memory. + pub const DMA_ATTR_MMIO: Attrs = Attrs(bindings::DMA_ATTR_MMIO); } /// An abstraction of the `dma_alloc_coherent` API. -- 2.50.1