Re: [RFC PATCH 3/6] dt-bindings: xen: Add xen,dev-domid property description for xen-virtio layer

[Stefano Stabellini]

On Thu, 14 Apr 2022, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> 
> Introduce Xen specific binding for the virtio-mmio device to be used
> by Xen virtio support driver in a subsequent commit.
> 
> This binding specifies the ID of Xen domain where the corresponding
> device (backend) resides. This is needed for the option to restrict
> memory access using Xen grant mappings to work.
> 
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> ---
>  .../devicetree/bindings/virtio/xen,dev-domid.yaml  | 39 ++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/virtio/xen,dev-domid.yaml
> 
> diff --git a/Documentation/devicetree/bindings/virtio/xen,dev-domid.yaml b/Documentation/devicetree/bindings/virtio/xen,dev-domid.yaml
> new file mode 100644
> index 00000000..78be993
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/virtio/xen,dev-domid.yaml
> @@ -0,0 +1,39 @@
> +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/virtio/xen,dev-domid.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Xen specific binding for the virtio device
> +
> +maintainers:
> +  - Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> +
> +select: true
> +
> +description:
> +  This binding specifies the ID of Xen domain where the corresponding device
> +  (backend) resides. This is needed for the option to restrict memory access
> +  using Xen grant mappings to work.
> +
> +  Note that current and generic "iommus" bindings are mutually exclusive, since
> +  the restricted memory access model on Xen behaves as a kind of software IOMMU.

I don't think that this last statement is necessary or fully accurate, so
I would remove it. Other than that, this looks good to me.


> +properties:
> +  xen,dev-domid:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      Should contain the ID of device's domain.

Maybe better as:
"The domid (domain ID) of the domain where the device (backend) is running"



> +additionalProperties: true
> +
> +examples:
> +  - |
> +    virtio_block@3000 {
> +            compatible = "virtio,mmio";
> +            reg = <0x3000 0x100>;
> +            interrupts = <41>;
> +
> +            /* The device is located in Xen domain with ID 1 */
> +            xen,dev-domid = <1>;
> +    };
> -- 
> 2.7.4
>