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Date: Sat, 19 Jun 2021 11:40:42 +0800
From: Claire Chang <tientzu@...omium.org>
To: Rob Herring <robh+dt@...nel.org>, mpe@...erman.id.au,
Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
Frank Rowand <frowand.list@...il.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
boris.ostrovsky@...cle.com, jgross@...e.com,
Christoph Hellwig <hch@....de>,
Marek Szyprowski <m.szyprowski@...sung.com>
Cc: benh@...nel.crashing.org, paulus@...ba.org,
"list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
sstabellini@...nel.org, Robin Murphy <robin.murphy@....com>,
grant.likely@....com, xypron.glpk@....de,
Thierry Reding <treding@...dia.com>, mingo@...nel.org,
bauerman@...ux.ibm.com, peterz@...radead.org,
Greg KH <gregkh@...uxfoundation.org>,
Saravana Kannan <saravanak@...gle.com>,
"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
heikki.krogerus@...ux.intel.com,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Randy Dunlap <rdunlap@...radead.org>,
Dan Williams <dan.j.williams@...el.com>,
Bartosz Golaszewski <bgolaszewski@...libre.com>,
linux-devicetree <devicetree@...r.kernel.org>,
lkml <linux-kernel@...r.kernel.org>,
linuxppc-dev@...ts.ozlabs.org, xen-devel@...ts.xenproject.org,
Nicolas Boichat <drinkcat@...omium.org>,
Jim Quinlan <james.quinlan@...adcom.com>, tfiga@...omium.org,
bskeggs@...hat.com, bhelgaas@...gle.com, chris@...is-wilson.co.uk,
tientzu@...omium.org, daniel@...ll.ch, airlied@...ux.ie,
dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
jani.nikula@...ux.intel.com, jxgao@...gle.com,
joonas.lahtinen@...ux.intel.com, linux-pci@...r.kernel.org,
maarten.lankhorst@...ux.intel.com, matthew.auld@...el.com,
rodrigo.vivi@...el.com, thomas.hellstrom@...ux.intel.com,
thomas.lendacky@....com
Subject: [PATCH v14 11/12] dt-bindings: of: Add restricted DMA pool
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 <tientzu@...omium.org>
Tested-by: Stefano Stabellini <sstabellini@...nel.org>
Tested-by: Will Deacon <will@...nel.org>
---
.../reserved-memory/reserved-memory.txt | 36 +++++++++++++++++--
1 file changed, 33 insertions(+), 3 deletions(-)
diff --git a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
index e8d3096d922c..39b5f4c5a511 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 <vendor>,[<device>-]<usage>
no-map (optional) - empty property
- Indicates the operating system must not create a virtual mapping
@@ -85,10 +102,11 @@ memory-region-names (optional) - a list of names, one for each corresponding
Example
-------
-This example defines 3 contiguous regions are defined for Linux kernel:
+This example defines 4 contiguous regions for Linux kernel:
one default of all device drivers (named linux,cma@...00000 and 64MiB in size),
-one dedicated to the framebuffer device (named framebuffer@...00000, 8MiB), and
-one for multimedia processing (named multimedia-memory@...00000, 64MiB).
+one dedicated to the framebuffer device (named framebuffer@...00000, 8MiB),
+one for multimedia processing (named multimedia-memory@...00000, 64MiB), and
+one for restricted dma pool (named restricted_dma_reserved@...0000000, 64MiB).
/ {
#address-cells = <1>;
@@ -120,6 +138,11 @@ one for multimedia processing (named multimedia-memory@...00000, 64MiB).
compatible = "acme,multimedia-memory";
reg = <0x77000000 0x4000000>;
};
+
+ restricted_dma_reserved: restricted_dma_reserved {
+ compatible = "restricted-dma-pool";
+ reg = <0x50000000 0x4000000>;
+ };
};
/* ... */
@@ -138,4 +161,11 @@ one for multimedia processing (named multimedia-memory@...00000, 64MiB).
memory-region = <&multimedia_reserved>;
/* ... */
};
+
+ pcie_device: pcie_device@0,0 {
+ reg = <0x83010000 0x0 0x00000000 0x0 0x00100000
+ 0x83010000 0x0 0x00100000 0x0 0x00100000>;
+ memory-region = <&restricted_dma_reserved>;
+ /* ... */
+ };
};
--
2.32.0.288.g62a8d224e6-goog
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