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Tue, 05 Jan 2021 19:42:09 -0800 (PST) Received: from localhost ([2401:fa00:1:10:3e52:82ff:fe5e:cc9d]) by smtp.gmail.com with ESMTPSA id f7sm581725pjs.25.2021.01.05.19.42.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Jan 2021 19:42:09 -0800 (PST) From: Claire Chang To: robh+dt@kernel.org, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, joro@8bytes.org, will@kernel.org, frowand.list@gmail.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com Subject: [RFC PATCH v3 5/6] dt-bindings: of: Add restricted DMA pool Date: Wed, 6 Jan 2021 11:41:23 +0800 Message-Id: <20210106034124.30560-6-tientzu@chromium.org> X-Mailer: git-send-email 2.29.2.729.g45daf8777d-goog In-Reply-To: <20210106034124.30560-1-tientzu@chromium.org> References: <20210106034124.30560-1-tientzu@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Wed, 06 Jan 2021 14:44:46 +1100 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: heikki.krogerus@linux.intel.com, peterz@infradead.org, grant.likely@arm.com, mingo@kernel.org, drinkcat@chromium.org, saravanak@google.com, xypron.glpk@gmx.de, rafael.j.wysocki@intel.com, bgolaszewski@baylibre.com, xen-devel@lists.xenproject.org, treding@nvidia.com, devicetree@vger.kernel.org, Claire Chang , dan.j.williams@intel.com, andriy.shevchenko@linux.intel.com, gregkh@linuxfoundation.org, rdunlap@infradead.org, linux-kernel@vger.kernel.org, tfiga@chromium.org, iommu@lists.linux-foundation.org, linuxppc-dev@lists.ozlabs.org, bauerman@linux.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Introduce the new compatible string, restricted-dma-pool, for restricted DMA. One can specify the address and length of the restricted DMA memory region by restricted-dma-pool in the device tree. Signed-off-by: Claire Chang --- .../reserved-memory/reserved-memory.txt | 24 +++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt index e8d3096d922c..44975e2a1fd2 100644 --- a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt +++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt @@ -51,6 +51,20 @@ compatible (optional) - standard definition used as a shared pool of DMA buffers for a set of devices. It can be used by an operating system to instantiate the necessary pool management subsystem if necessary. + - restricted-dma-pool: This indicates a region of memory meant to be + used as a pool of restricted DMA buffers for a set of devices. The + memory region would be the only region accessible to those devices. + When using this, the no-map and reusable properties must not be set, + so the operating system can create a virtual mapping that will be used + for synchronization. The main purpose for restricted DMA is to + mitigate the lack of DMA access control on systems without an IOMMU, + which could result in the DMA accessing the system memory at + unexpected times and/or unexpected addresses, possibly leading to data + leakage or corruption. The feature on its own provides a basic level + of protection against the DMA overwriting buffer contents at + unexpected times. However, to protect against general data leakage and + system memory corruption, the system needs to provide way to restrict + the DMA to a predefined memory region. - vendor specific string in the form ,[-] no-map (optional) - empty property - Indicates the operating system must not create a virtual mapping @@ -120,6 +134,11 @@ one for multimedia processing (named multimedia-memory@77000000, 64MiB). compatible = "acme,multimedia-memory"; reg = <0x77000000 0x4000000>; }; + + restricted_dma_mem_reserved: restricted_dma_mem_reserved { + compatible = "restricted-dma-pool"; + reg = <0x50000000 0x400000>; + }; }; /* ... */ @@ -138,4 +157,9 @@ one for multimedia processing (named multimedia-memory@77000000, 64MiB). memory-region = <&multimedia_reserved>; /* ... */ }; + + pcie_device: pcie_device@0,0 { + memory-region = <&restricted_dma_mem_reserved>; + /* ... */ + }; }; -- 2.29.2.729.g45daf8777d-goog