Re: [PATCH v4 14/14] Documentation: KHO: Add memblock bindings

[Krzysztof Kozlowski <krzk@kernel.org>]

On 06/02/2025 14:27, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> We introduced KHO into Linux: A framework that allows Linux to pass
> metadata and memory across kexec from Linux to Linux. KHO reuses fdt
> as file format and shares a lot of the same properties of firmware-to-
> Linux boot formats: It needs a stable, documented ABI that allows for
> forward and backward compatibility as well as versioning.

Please use subject prefixes matching the subsystem. You can get them for
example with `git log --oneline -- DIRECTORY_OR_FILE` on the directory
your patch is touching. For bindings, the preferred subjects are
explained here:
https://www.kernel.org/doc/html/latest/devicetree/bindings/submitting-patches.html#i-for-patch-submitters


> 
> As first user of KHO, we introduced memblock which can now preserve
> memory ranges reserved with reserve_mem command line options contents
> across kexec, so you can use the post-kexec kernel to read traces from
> the pre-kexec kernel.
> 
> This patch adds memblock schemas similar to "device" device tree ones to
> a new kho bindings directory. This allows us to force contributors to
> document the data that moves across KHO kexecs and catch breaking change
> during review.
> 
> Co-developed-by: Alexander Graf <graf@amazon.com>
> Signed-off-by: Alexander Graf <graf@amazon.com>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  .../kho/bindings/memblock/reserve_mem.yaml    | 41 ++++++++++++++++++
>  .../bindings/memblock/reserve_mem_map.yaml    | 42 +++++++++++++++++++
>  2 files changed, 83 insertions(+)
>  create mode 100644 Documentation/kho/bindings/memblock/reserve_mem.yaml
>  create mode 100644 Documentation/kho/bindings/memblock/reserve_mem_map.yaml
> 
> diff --git a/Documentation/kho/bindings/memblock/reserve_mem.yaml b/Documentation/kho/bindings/memblock/reserve_mem.yaml
> new file mode 100644
> index 000000000000..7b01791b10b3
> --- /dev/null
> +++ b/Documentation/kho/bindings/memblock/reserve_mem.yaml
> @@ -0,0 +1,41 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/memblock/reserve_mem.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Memblock reserved memory
> +
> +maintainers:
> +  - Mike Rapoport <rppt@kernel.org>
> +
> +description: |
> +  Memblock can serialize its current memory reservations created with
> +  reserve_mem command line option across kexec through KHO.
> +  The post-KHO kernel can then consume these reservations and they are
> +  guaranteed to have the same physical address.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - reserve_mem-v1

NAK, underscores are not allowed. Please follow carefully DTS coding style.

> +
> +patternProperties:
> +  "$[0-9a-f_]+^":

No underscores.

> +    $ref: reserve_mem_map.yaml#
> +    description: reserved memory regions
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    reserve_mem {

Again, do not introduce own coding style.

I don't understand why do you need this in the first place. There is
already reserved-memory block.


> +      compatible = "reserve_mem-v1";
> +        r1 {
> +          compatible = "reserve_mem_map-v1";
> +          mem = <0xc07c 0x2000000 0x01 0x00>;
> +        };
> +    };
> diff --git a/Documentation/kho/bindings/memblock/reserve_mem_map.yaml b/Documentation/kho/bindings/memblock/reserve_mem_map.yaml
> new file mode 100644
> index 000000000000..09001c5f2124
> --- /dev/null
> +++ b/Documentation/kho/bindings/memblock/reserve_mem_map.yaml
> @@ -0,0 +1,42 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/memblock/reserve_mem_map.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Memblock reserved memory regions
> +
> +maintainers:
> +  - Mike Rapoport <rppt@kernel.org>
> +
> +description: |
> +  Memblock can serialize its current memory reservations created with
> +  reserve_mem command line option across kexec through KHO.
> +  This object describes each such region.
> +
> +properties:
> +  compatible:
> +    enum:
> +      - reserve_mem_map-v1

Explain why you cannot use existing reserved memory bindings.


Best regards,
Krzysztof