linux-kernel - [PATCH v4 14/14] Documentation: KHO: Add memblock bindings

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Message-ID: <20250206132754.2596694-15-rppt@kernel.org>
Date: Thu,  6 Feb 2025 15:27:54 +0200
From: Mike Rapoport <rppt@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Alexander Graf <graf@...zon.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Anthony Yznaga <anthony.yznaga@...cle.com>,
	Arnd Bergmann <arnd@...db.de>,
	Ashish Kalra <ashish.kalra@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Borislav Petkov <bp@...en8.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Eric Biederman <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...hat.com>,
	James Gowans <jgowans@...zon.com>,
	Jonathan Corbet <corbet@....net>,
	Krzysztof Kozlowski <krzk@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Mike Rapoport <rppt@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Pasha Tatashin <pasha.tatashin@...een.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pratyush Yadav <ptyadav@...zon.de>,
	Rob Herring <robh+dt@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tom Lendacky <thomas.lendacky@....com>,
	Usama Arif <usama.arif@...edance.com>,
	Will Deacon <will@...nel.org>,
	devicetree@...r.kernel.org,
	kexec@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-doc@...r.kernel.org,
	linux-mm@...ck.org,
	x86@...nel.org
Subject: [PATCH v4 14/14] Documentation: KHO: Add memblock bindings

From: "Mike Rapoport (Microsoft)" <rppt@...nel.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.

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@...zon.com>
Signed-off-by: Alexander Graf <graf@...zon.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.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@...nel.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
+
+patternProperties:
+  "$[0-9a-f_]+^":
+    $ref: reserve_mem_map.yaml#
+    description: reserved memory regions
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    reserve_mem {
+      compatible = "reserve_mem-v1";
+        r1 {
+          compatible = "reserve_mem_map-v1";
+          mem = <0xc07c 0x2000000 0x01 0x00>;
+        };
+    };
diff --git a/Documentation/kho/bindings/memblock/reserve_mem_map.yaml b/Documentation/kho/bindings/memblock/reserve_mem_map.yaml
new file mode 100644
index 000000000000..09001c5f2124
--- /dev/null
+++ b/Documentation/kho/bindings/memblock/reserve_mem_map.yaml
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$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@...nel.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
+
+  mem:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    description: |
+      Array of { u64 phys_addr, u64 len } elements that describe a list of
+      memory ranges.
+
+required:
+  - compatible
+  - mem
+
+additionalProperties: false
+
+examples:
+  - |
+    reserve_mem {
+      compatible = "reserve_mem-v1";
+        r1 {
+          compatible = "reserve_mem_map-v1";
+          mem = <0xc07c 0x2000000 0x01 0x00>;
+        };
+    };
-- 
2.47.2