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Message-ID: <20260105165839.285270-7-rppt@kernel.org>
Date: Mon, 5 Jan 2026 18:58:39 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexander Graf <graf@...zon.com>,
Jason Miu <jasonmiu@...gle.com>,
Jonathan Corbet <corbet@....net>,
Mike Rapoport <rppt@...nel.org>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Pratyush Yadav <pratyush@...nel.org>,
kexec@...ts.infradead.org,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: [PATCH 6/6] kho/abi: add memblock ABI header
From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
Introduce KHO ABI header describing preservation ABI for memblock's
reserve_mem regions and link the relevant documentation to KHO docs.
Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
---
Documentation/core-api/kho/abi.rst | 6 ++
.../kho/bindings/memblock/memblock.yaml | 39 ----------
.../kho/bindings/memblock/reserve-mem.yaml | 40 -----------
include/linux/kho/abi/memblock.h | 72 +++++++++++++++++++
mm/memblock.c | 4 +-
5 files changed, 79 insertions(+), 82 deletions(-)
delete mode 100644 Documentation/core-api/kho/bindings/memblock/memblock.yaml
delete mode 100644 Documentation/core-api/kho/bindings/memblock/reserve-mem.yaml
create mode 100644 include/linux/kho/abi/memblock.h
diff --git a/Documentation/core-api/kho/abi.rst b/Documentation/core-api/kho/abi.rst
index 1d9916adee23..2e63be3486cf 100644
--- a/Documentation/core-api/kho/abi.rst
+++ b/Documentation/core-api/kho/abi.rst
@@ -16,6 +16,12 @@ vmalloc preservation ABI
.. kernel-doc:: include/linux/kho/abi/kexec_handover.h
:doc: Kexec Handover ABI for vmalloc Preservation
+memblock preservation ABI
+=========================
+
+.. kernel-doc:: include/linux/kho/abi/memblock.h
+ :doc: memblock kexec handover ABI
+
See Also
========
diff --git a/Documentation/core-api/kho/bindings/memblock/memblock.yaml b/Documentation/core-api/kho/bindings/memblock/memblock.yaml
deleted file mode 100644
index d388c28eb91d..000000000000
--- a/Documentation/core-api/kho/bindings/memblock/memblock.yaml
+++ /dev/null
@@ -1,39 +0,0 @@
-# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
-%YAML 1.2
----
-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.yaml#
- description: reserved memory regions
-
-required:
- - compatible
-
-additionalProperties: false
-
-examples:
- - |
- memblock {
- compatible = "memblock-v1";
- n1 {
- compatible = "reserve-mem-v1";
- start = <0xc06b 0x4000000>;
- size = <0x04 0x00>;
- };
- };
diff --git a/Documentation/core-api/kho/bindings/memblock/reserve-mem.yaml b/Documentation/core-api/kho/bindings/memblock/reserve-mem.yaml
deleted file mode 100644
index 10282d3d1bcd..000000000000
--- a/Documentation/core-api/kho/bindings/memblock/reserve-mem.yaml
+++ /dev/null
@@ -1,40 +0,0 @@
-# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
-%YAML 1.2
----
-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-v1
-
- start:
- description: |
- physical address (u64) of the reserved memory region.
-
- size:
- description: |
- size (u64) of the reserved memory region.
-
-required:
- - compatible
- - start
- - size
-
-additionalProperties: false
-
-examples:
- - |
- n1 {
- compatible = "reserve-mem-v1";
- start = <0xc06b 0x4000000>;
- size = <0x04 0x00>;
- };
diff --git a/include/linux/kho/abi/memblock.h b/include/linux/kho/abi/memblock.h
new file mode 100644
index 000000000000..fbfb2eb1b1cf
--- /dev/null
+++ b/include/linux/kho/abi/memblock.h
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _LINUX_KHO_ABI_MEMBLOCK_H
+#define _LINUX_KHO_ABI_MEMBLOCK_H
+
+/**
+ * DOC: memblock kexec handover ABI
+ *
+ * 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.
+ *
+ * The state is serialized using Flattened Device Tree (FDT) format. Any
+ * modification to the FDT structure, node properties, or the compatible
+ * strings constitutes a breaking change. Such changes require incrementing the
+ * version number in the relevant `_COMPATIBLE` string to prevent a new kernel
+ * from misinterpreting data from an old kernel.
+ *
+ * Changes are allowed provided the compatibility version is incremented.
+ * However, backward/forward compatibility is only guaranteed for kernels
+ * supporting the same ABI version.
+ *
+ * FDT Structure Overview:
+ * The entire memblock state is encapsulated within a single KHO entry named
+ * "memblock".
+ * This entry contains an FDT with the following layout:
+ *
+ * .. code-block:: none
+ *
+ * / {
+ * compatible = "memblock-v1";
+ *
+ * n1 {
+ * compatible = "reserve-mem-v1";
+ * start = <0xc06b 0x4000000>;
+ * size = <0x04 0x00>;
+ * };
+ * };
+ *
+ * Main memblock node (/):
+ *
+ * - compatible: "memblock-v1"
+
+ * Identifies the overall memblock ABI version.
+ *
+ * reserved_mem node:
+ * These nodes describe all reserve_mem regions.
+ *
+ * - compatible: "reserve-mem-v1"
+ *
+ * Identifies the ABI version of reserve_mem descriptions
+ *
+ * - start: u64
+ *
+ * Physical address of the reserved memory region.
+ *
+ * - size: u64
+ *
+ * size in bytes of the reserved memory region.
+ */
+
+/* Top level memblock FDT node name. */
+#define MEMBLOCK_KHO_FDT "memblock"
+
+/* The compatible string for the memblock FDT root node. */
+#define MEMBLOCK_KHO_NODE_COMPATIBLE "memblock-v1"
+
+/* The compatible string for the reserve_mem FDT nodes. */
+#define RESERVE_MEM_KHO_NODE_COMPATIBLE "reserve-mem-v1"
+
+#endif /* _LINUX_KHO_ABI_MEMBLOCK_H */
diff --git a/mm/memblock.c b/mm/memblock.c
index 905d06b16348..6cff515d82f4 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -21,6 +21,7 @@
#ifdef CONFIG_KEXEC_HANDOVER
#include <linux/libfdt.h>
#include <linux/kexec_handover.h>
+#include <linux/kho/abi/memblock.h>
#endif /* CONFIG_KEXEC_HANDOVER */
#include <asm/sections.h>
@@ -2442,9 +2443,6 @@ int reserve_mem_release_by_name(const char *name)
}
#ifdef CONFIG_KEXEC_HANDOVER
-#define MEMBLOCK_KHO_FDT "memblock"
-#define MEMBLOCK_KHO_NODE_COMPATIBLE "memblock-v1"
-#define RESERVE_MEM_KHO_NODE_COMPATIBLE "reserve-mem-v1"
static int __init reserved_mem_preserve(void)
{
--
2.51.0
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