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Wysocki" , heikki.krogerus@linux.intel.com, Andy Shevchenko , Randy Dunlap , Dan Williams , Bartosz Golaszewski , linux-devicetree , lkml , linuxppc-dev@lists.ozlabs.org, xen-devel@lists.xenproject.org, Nicolas Boichat , Jim Quinlan , tfiga@chromium.org, bskeggs@redhat.com, bhelgaas@google.com, chris@chris-wilson.co.uk, tientzu@chromium.org, daniel@ffwll.ch, airlied@linux.ie, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, jani.nikula@linux.intel.com, jxgao@google.com, joonas.lahtinen@linux.intel.com, linux-pci@vger.kernel.org, maarten.lankhorst@linux.intel.com, matthew.auld@intel.com, nouveau@lists.freedesktop.org, rodrigo.vivi@intel.com, thomas.hellstrom@linux.intel.com Subject: [PATCH v6 14/15] dt-bindings: of: Add restricted DMA pool Date: Mon, 10 May 2021 17:50:25 +0800 Message-Id: <20210510095026.3477496-15-tientzu@chromium.org> X-Mailer: git-send-email 2.31.1.607.g51e8a6a459-goog In-Reply-To: <20210510095026.3477496-1-tientzu@chromium.org> References: <20210510095026.3477496-1-tientzu@chromium.org> MIME-Version: 1.0 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 reserved-memory node. Signed-off-by: Claire Chang --- .../reserved-memory/reserved-memory.txt | 27 +++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt index e8d3096d922c..284aea659015 100644 --- a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt +++ b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt @@ -51,6 +51,23 @@ 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 lock down + the memory access, e.g., MPU. Note that since coherent allocation + needs remapping, one must set up another device coherent pool by + shared-dma-pool and use dma_alloc_from_dev_coherent instead for atomic + coherent allocation. - vendor specific string in the form ,[-] no-map (optional) - empty property - Indicates the operating system must not create a virtual mapping @@ -120,6 +137,11 @@ 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 +160,9 @@ 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>; + /* ... */ + }; };