Re: [PATCH V4 5/8] dt-bindings: Add xen,grant-dma IOMMU description for xen-grant DMA ops

Rob Herring
2022-06-05T22:45:42Z

On Thu, 02 Jun 2022 22:23:50 +0300, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>
> The main purpose of this binding is to communicate Xen specific
> information using generic IOMMU device tree bindings (which is
> a good fit here) rather than introducing a custom property.
>
> Introduce Xen specific IOMMU for the virtualized device (e.g. virtio)
> to be used by Xen grant DMA-mapping layer in the subsequent commit.
>
> The reference to Xen specific IOMMU node using "iommus" property
> indicates that Xen grant mappings need to be enabled for the device,
> and it specifies the ID of the domain where the corresponding backend
> resides. The domid (domain ID) is used as an argument to the Xen grant
> mapping APIs.
>
> This is needed for the option to restrict memory access using Xen grant
> mappings to work which primary goal is to enable using virtio devices
> in Xen guests.
>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
> ---
> Changes RFC -> V1:
> - update commit subject/description and text in description
> - move to devicetree/bindings/arm/
>
> Changes V1 -> V2:
> - update text in description
> - change the maintainer of the binding
> - fix validation issue
> - reference xen,dev-domid.yaml schema from virtio/mmio.yaml
>
> Change V2 -> V3:
> - Stefano already gave his Reviewed-by, I dropped it due to the changes (significant)
> - use generic IOMMU device tree bindings instead of custom property
> "xen,dev-domid"
> - change commit subject and description, was
> "dt-bindings: Add xen,dev-domid property description for xen-grant DMA ops"
>
> Changes V3 -> V4:
> - add Stefano's R-b
> - remove underscore in iommu node name
> - remove consumer example virtio@3000
> - update text for two descriptions
> ---
> .../devicetree/bindings/iommu/xen,grant-dma.yaml | 39 ++++++++++++++++++++++
> 1 file changed, 39 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/iommu/xen,grant-dma.yaml
>

Reviewed-by: Rob Herring <robh@kernel.org>