Re: [PATCH V1 4/6] dt-bindings: Add xen, dev-domid property description for xen-grant DMA ops

Re: [PATCH V1 4/6] dt-bindings: Add xen, dev-domid property description for xen-grant DMA ops

[Stefano Stabellini]

On Fri, 22 Apr 2022, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> Introduce Xen specific binding for the virtualized device (e.g. virtio)
> to be used by Xen grant DMA-mapping layer in the subsequent commit.
> 
> This binding indicates that Xen grant mappings scheme needs to be
> enabled for the device which DT node contains that property and specifies
> the ID of Xen domain where the corresponding backend resides. The ID
> (domid) is used as an argument to the 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>

Looks OK to me. Just a couple of grammar improvements below. Aside from
those, I have no further comments.


> ---
> Changes RFC -> V1:
>    - update commit subject/description and text in description
>    - move to devicetree/bindings/arm/
> ---
>  .../devicetree/bindings/arm/xen,dev-domid.yaml     | 37 ++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> 
> diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> new file mode 100644
> index 00000000..ef0f747
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> @@ -0,0 +1,37 @@
> +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/arm/xen,dev-domid.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Xen specific binding for the virtualized device (e.g. virtio)

NIT: Xen specific binding for virtualized devices (e.g. virtio)


> +maintainers:
> +  - Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> +
> +select: true
> +
> +description:
> +  This binding indicates that Xen grant mappings scheme needs to be enabled
> +  for that device and 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.

NIT:

This binding indicates that Xen grant mappings need to be enabled for
the device, and it specifies the ID of the domain where the
corresponding device (backend) resides. The property is required to
restrict memory access using Xen grant mappings.


> +properties:
> +  xen,dev-domid:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      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>;
> +    };

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Re: [PATCH V1 4/6] dt-bindings: Add xen,dev-domid property description for xen-grant DMA ops

[Rob Herring]

On Fri, Apr 22, 2022 at 07:51:01PM +0300, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> Introduce Xen specific binding for the virtualized device (e.g. virtio)
> to be used by Xen grant DMA-mapping layer in the subsequent commit.
> 
> This binding indicates that Xen grant mappings scheme needs to be
> enabled for the device which DT node contains that property and specifies
> the ID of Xen domain where the corresponding backend resides. The ID
> (domid) is used as an argument to the 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>
> ---
> Changes RFC -> V1:
>    - update commit subject/description and text in description
>    - move to devicetree/bindings/arm/
> ---
>  .../devicetree/bindings/arm/xen,dev-domid.yaml     | 37 ++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> 
> diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> new file mode 100644
> index 00000000..ef0f747
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> @@ -0,0 +1,37 @@
> +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/arm/xen,dev-domid.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Xen specific binding for the virtualized device (e.g. virtio)
> +
> +maintainers:
> +  - Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> +
> +select: true

Do we really need to support this property everywhere?

> +
> +description:
> +  This binding indicates that Xen grant mappings scheme needs to be enabled
> +  for that device and 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.
> +
> +properties:
> +  xen,dev-domid:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description:
> +      The domid (domain ID) of the domain where the device (backend) is running.
> +
> +additionalProperties: true
> +
> +examples:
> +  - |
> +    virtio_block@3000 {

virtio@3000

> +            compatible = "virtio,mmio";
> +            reg = <0x3000 0x100>;
> +            interrupts = <41>;
> +
> +            /* The device is located in Xen domain with ID 1 */
> +            xen,dev-domid = <1>;

This fails validation:

Documentation/devicetree/bindings/arm/xen,dev-domid.example.dtb: virtio_block@3000: xen,dev-domid: [[1]] is not of type 'object'
        From schema: /home/rob/proj/git/linux-dt/Documentation/devicetree/bindings/virtio/mmio.yaml

The property has to be added to the virtio/mmio.yaml schema. If it is 
not needed elsewhere, then *just* add the property there.

Rob
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Re: [PATCH V1 4/6] dt-bindings: Add xen,dev-domid property description for xen-grant DMA ops

[Rob Herring]

On Tue, May 03, 2022 at 08:09:32PM +0300, Oleksandr wrote:
> 
> On 03.05.22 00:59, Rob Herring wrote:
> 
> Hello Rob
> 
> 
> > On Fri, Apr 22, 2022 at 07:51:01PM +0300, Oleksandr Tyshchenko wrote:
> > > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> > > 
> > > Introduce Xen specific binding for the virtualized device (e.g. virtio)
> > > to be used by Xen grant DMA-mapping layer in the subsequent commit.
> > > 
> > > This binding indicates that Xen grant mappings scheme needs to be
> > > enabled for the device which DT node contains that property and specifies
> > > the ID of Xen domain where the corresponding backend resides. The ID
> > > (domid) is used as an argument to the 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>
> > > ---
> > > Changes RFC -> V1:
> > >     - update commit subject/description and text in description
> > >     - move to devicetree/bindings/arm/
> > > ---
> > >   .../devicetree/bindings/arm/xen,dev-domid.yaml     | 37 ++++++++++++++++++++++
> > >   1 file changed, 37 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> > > 
> > > diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> > > new file mode 100644
> > > index 00000000..ef0f747
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> > > @@ -0,0 +1,37 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/arm/xen,dev-domid.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Xen specific binding for the virtualized device (e.g. virtio)
> > > +
> > > +maintainers:
> > > +  - Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> > > +
> > > +select: true
> > Do we really need to support this property everywhere?
> 
> From my understanding - yes.
> 
> As, I think, any device node describing virtulized device in the guest
> device tree can have this property.  Initially (in the RFC series) the
> "solution to restrict memory access using Xen grant mappings" was
> virtio-specific.
> 
> Although the support of virtio is a primary target of this series, we
> decided to generalize this work and expand it to any device [1]. So the Xen
> grant mappings scheme (this property to be used for) can be theoretically
> used for any device emulated by the Xen backend.
> 
> 
> > > +
> > > +description:
> > > +  This binding indicates that Xen grant mappings scheme needs to be enabled
> > > +  for that device and 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.
> > > +
> > > +properties:
> > > +  xen,dev-domid:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    description:
> > > +      The domid (domain ID) of the domain where the device (backend) is running.
> > > +
> > > +additionalProperties: true
> > > +
> > > +examples:
> > > +  - |
> > > +    virtio_block@3000 {
> > virtio@3000
> 
> ok, will change
> 
> 
> > 
> > > +            compatible = "virtio,mmio";
> > > +            reg = <0x3000 0x100>;
> > > +            interrupts = <41>;
> > > +
> > > +            /* The device is located in Xen domain with ID 1 */
> > > +            xen,dev-domid = <1>;
> > This fails validation:
> > 
> > Documentation/devicetree/bindings/arm/xen,dev-domid.example.dtb: virtio_block@3000: xen,dev-domid: [[1]] is not of type 'object'
> >          From schema: /home/rob/proj/git/linux-dt/Documentation/devicetree/bindings/virtio/mmio.yaml
> 
> Thank you for pointing this out, my fault, I haven't "properly" checked this
> before. I think, we need to remove "compatible = "virtio,mmio"; here

Uhh, no. That just means the example is incomplete. You need to add this 
property or reference this schema from virtio/mmio.yaml.


> diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> index 2daa8aa..d2f2140 100644
> --- a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> +++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
> @@ -28,7 +28,7 @@ additionalProperties: true
>  examples:
>    - |
>      virtio_block@3000 {
> -            compatible = "virtio,mmio";
> +            /* ... */
>              reg = <0x3000 0x100>;
>              interrupts = <41>;
> 
> 
> 
> > 
> > The property has to be added to the virtio/mmio.yaml schema. If it is
> > not needed elsewhere, then *just* add the property there.
> 
> As I described above, the property is not virtio specific and can be used
> for any virtualized device for which Xen grant mappings scheme needs to be
> enabled (xen-grant DMA-mapping layer).

But that's a finite list of devices, right? In any case, you have to 
list the property anywhere it can be used.

Rob
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