On Thu, May 30, 2019 at 06:09:24PM +0100, Jean-Philippe Brucker wrote:
> Some systems implement virtio-iommu as a PCI endpoint. The operating
> system needs to discover the relationship between IOMMU and masters long
> before the PCI endpoint gets probed. Add a PCI child node to describe the
> virtio-iommu device.
>
> The virtio-pci-iommu is conceptually split between a PCI programming
> interface and a translation component on the parent bus. The latter
> doesn't have a node in the device tree. The virtio-pci-iommu node
> describes both, by linking the PCI endpoint to "iommus" property of DMA
> master nodes and to "iommu-map" properties of bus nodes.
>
> Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
So this is just an example right?
We are not defining any new properties or anything like that.
I think down the road for non dt platforms we want to put this
info in the config space of the device. I do not think ACPI
is the best option for this since not all systems have it.
But that can wait.
> ---
> .../devicetree/bindings/virtio/iommu.txt | 66 +++++++++++++++++++
> 1 file changed, 66 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/virtio/iommu.txt
>
> diff --git a/Documentation/devicetree/bindings/virtio/iommu.txt b/Documentation/devicetree/bindings/virtio/iommu.txt
> new file mode 100644
> index 000000000000..2407fea0651c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/virtio/iommu.txt
> @@ -0,0 +1,66 @@
> +* virtio IOMMU PCI device
> +
> +When virtio-iommu uses the PCI transport, its programming interface is
> +discovered dynamically by the PCI probing infrastructure. However the
> +device tree statically describes the relation between IOMMU and DMA
> +masters. Therefore, the PCI root complex that hosts the virtio-iommu
> +contains a child node representing the IOMMU device explicitly.
> +
> +Required properties:
> +
> +- compatible: Should be "virtio,pci-iommu"
> +- reg: PCI address of the IOMMU. As defined in the PCI Bus
> + Binding reference [1], the reg property is a five-cell
> + address encoded as (phys.hi phys.mid phys.lo size.hi
> + size.lo). phys.hi should contain the device's BDF as
> + 0b00000000 bbbbbbbb dddddfff 00000000. The other cells
> + should be zero.
> +- #iommu-cells: Each platform DMA master managed by the IOMMU is assigned
> + an endpoint ID, described by the "iommus" property [2].
> + For virtio-iommu, #iommu-cells must be 1.
> +
> +Notes:
> +
> +- DMA from the IOMMU device isn't managed by another IOMMU. Therefore the
> + virtio-iommu node doesn't have an "iommus" property, and is omitted from
> + the iommu-map property of the root complex.
> +
> +Example:
> +
> +pcie@10000000 {
> + compatible = "pci-host-ecam-generic";
> + ...
> +
> + /* The IOMMU programming interface uses slot 00:01.0 */
> + iommu0: iommu@0008 {
> + compatible = "virtio,pci-iommu";
> + reg = <0x00000800 0 0 0 0>;
> + #iommu-cells = <1>;
> + };
> +
> + /*
> + * The IOMMU manages all functions in this PCI domain except
> + * itself. Omit BDF 00:01.0.
> + */
> + iommu-map = <0x0 &iommu0 0x0 0x8>
> + <0x9 &iommu0 0x9 0xfff7>;
> +};
> +
> +pcie@20000000 {
> + compatible = "pci-host-ecam-generic";
> + ...
> + /*
> + * The IOMMU also manages all functions from this domain,
> + * with endpoint IDs 0x10000 - 0x1ffff
> + */
> + iommu-map = <0x0 &iommu0 0x10000 0x10000>;
> +};
> +
> +ethernet@fe001000 {
> + ...
> + /* The IOMMU manages this platform device with endpoint ID 0x20000 */
> + iommus = <&iommu0 0x20000>;
> +};
> +
> +[1] Documentation/devicetree/bindings/pci/pci.txt
> +[2] Documentation/devicetree/bindings/iommu/iommu.txt
> --
> 2.21.0
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