From dd1e79ef6ca188678ece81a77d0076ae7403116c Mon Sep 17 00:00:00 2001 From: "Mike Rapoport (Microsoft)" Date: Mon, 5 Jan 2026 18:58:39 +0200 Subject: kho/abi: add memblock ABI header Introduce KHO ABI header describing preservation ABI for memblock's reserve_mem regions and link the relevant documentation to KHO docs. [lukas.bulwahn@redhat.com: MAINTAINERS: adjust file entry in MEMBLOCK AND MEMORY MANAGEMENT INITIALIZATION] Link: https://lkml.kernel.org/r/20260107090438.22901-1-lukas.bulwahn@redhat.com [rppt@kernel.org: update reserved_mem node description, per Pratyush] Link: https://lkml.kernel.org/r/aW_M-HYZzx5SkbnZ@kernel.org Link: https://lkml.kernel.org/r/20260105165839.285270-7-rppt@kernel.org Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Pratyush Yadav Cc: Alexander Graf Cc: Jason Miu Cc: Jonathan Corbet Cc: Pasha Tatashin Signed-off-by: Andrew Morton --- include/linux/kho/abi/memblock.h | 73 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 include/linux/kho/abi/memblock.h (limited to 'include/linux') diff --git a/include/linux/kho/abi/memblock.h b/include/linux/kho/abi/memblock.h new file mode 100644 index 000000000000..27b042f470e1 --- /dev/null +++ b/include/linux/kho/abi/memblock.h @@ -0,0 +1,73 @@ +/* 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. The node name is the name + * defined by the user for a reserve_mem region. + * + * - 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 */ -- cgit v1.2.3