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

Stefano Stabellini
2022-04-15T22:01:32Z

On Thu, 14 Apr 2022, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>
> 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@epam.com>
> ---
> .../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@epam.com>
> +
> +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
>