67 lines
1.9 KiB
Plaintext
67 lines
1.9 KiB
Plaintext
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* virtio IOMMU PCI device
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When virtio-iommu uses the PCI transport, its programming interface is
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discovered dynamically by the PCI probing infrastructure. However the
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device tree statically describes the relation between IOMMU and DMA
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masters. Therefore, the PCI root complex that hosts the virtio-iommu
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contains a child node representing the IOMMU device explicitly.
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Required properties:
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- compatible: Should be "virtio,pci-iommu"
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- reg: PCI address of the IOMMU. As defined in the PCI Bus
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Binding reference [1], the reg property is a five-cell
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address encoded as (phys.hi phys.mid phys.lo size.hi
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size.lo). phys.hi should contain the device's BDF as
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0b00000000 bbbbbbbb dddddfff 00000000. The other cells
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should be zero.
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- #iommu-cells: Each platform DMA master managed by the IOMMU is assigned
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an endpoint ID, described by the "iommus" property [2].
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For virtio-iommu, #iommu-cells must be 1.
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Notes:
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- DMA from the IOMMU device isn't managed by another IOMMU. Therefore the
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virtio-iommu node doesn't have an "iommus" property, and is omitted from
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the iommu-map property of the root complex.
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Example:
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pcie@10000000 {
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compatible = "pci-host-ecam-generic";
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...
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/* The IOMMU programming interface uses slot 00:01.0 */
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iommu0: iommu@0008 {
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compatible = "virtio,pci-iommu";
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reg = <0x00000800 0 0 0 0>;
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#iommu-cells = <1>;
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};
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/*
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* The IOMMU manages all functions in this PCI domain except
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* itself. Omit BDF 00:01.0.
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*/
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iommu-map = <0x0 &iommu0 0x0 0x8>
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<0x9 &iommu0 0x9 0xfff7>;
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};
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pcie@20000000 {
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compatible = "pci-host-ecam-generic";
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...
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/*
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* The IOMMU also manages all functions from this domain,
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* with endpoint IDs 0x10000 - 0x1ffff
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*/
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iommu-map = <0x0 &iommu0 0x10000 0x10000>;
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};
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ethernet@fe001000 {
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...
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/* The IOMMU manages this platform device with endpoint ID 0x20000 */
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iommus = <&iommu0 0x20000>;
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};
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[1] Documentation/devicetree/bindings/pci/pci.txt
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[2] Documentation/devicetree/bindings/iommu/iommu.txt
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