From 0349ff2887059112ce06831ab29aec47a2a7285a Mon Sep 17 00:00:00 2001 From: Pasha Tatashin Date: Wed, 3 Jun 2026 15:43:56 +0000 Subject: kho: add support for linked-block serialization Introduce a linked-block serialization mechanism for state handover. Previously, LUO used contiguous memory blocks for serializing sessions and files, which imposed limits on the total number of items that could be preserved across a live update. This commit adds the infrastructure for a more flexible, block-based approach where serialized data is stored in a chain of linked blocks. This is a generic KHO serialization block infrastructure that can be used by multiple subsystems. Signed-off-by: Pasha Tatashin Link: https://patch.msgid.link/20260603154402.468928-8-pasha.tatashin@soleen.com Signed-off-by: Mike Rapoport (Microsoft) --- include/linux/kho/abi/block.h | 54 ++++++++++++++++++++++++++++++++++ include/linux/kho/abi/kexec_handover.h | 2 +- 2 files changed, 55 insertions(+), 1 deletion(-) create mode 100644 include/linux/kho/abi/block.h (limited to 'include/linux/kho') diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h new file mode 100644 index 000000000000..d06d64b963be --- /dev/null +++ b/include/linux/kho/abi/block.h @@ -0,0 +1,54 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (c) 2026, Google LLC. + * Pasha Tatashin + */ + +/** + * DOC: KHO Serialization Blocks ABI + * + * Subsystems using the KHO Serialization Blocks framework rely on the stable + * Application Binary Interface defined below to pass serialized state from a + * pre-update kernel to a post-update kernel. + * + * This interface is a contract. Any modification to the structure fields, + * compatible strings, or the layout of the `__packed` serialization + * structures defined here constitutes a breaking change. Such changes require + * incrementing the version number in the `KHO_FDT_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. + */ + +#ifndef _LINUX_KHO_ABI_BLOCK_H +#define _LINUX_KHO_ABI_BLOCK_H + +#include +#include + +/** + * KHO_BLOCK_SIZE - The size of each serialization block. + * + * This is defined as PAGE_SIZE. PAGE_SIZE is ABI compliant because live + * update between kernels with different page sizes is not supported by KHO. + */ +#define KHO_BLOCK_SIZE PAGE_SIZE + +/** + * struct kho_block_header_ser - Header for the serialized data block. + * @next: Physical address of the next struct kho_block_header_ser. + * @count: The number of entries that immediately follow this header in the + * memory block. + * + * This structure is located at the beginning of a block of physical memory + * preserved across a kexec. It provides the necessary metadata to interpret + * the array of entries that follow. + */ +struct kho_block_header_ser { + u64 next; + u64 count; +} __packed; + +#endif /* _LINUX_KHO_ABI_BLOCK_H */ diff --git a/include/linux/kho/abi/kexec_handover.h b/include/linux/kho/abi/kexec_handover.h index fb2d37417ad9..5e2eb8519bda 100644 --- a/include/linux/kho/abi/kexec_handover.h +++ b/include/linux/kho/abi/kexec_handover.h @@ -90,7 +90,7 @@ */ /* The compatible string for the KHO FDT root node. */ -#define KHO_FDT_COMPATIBLE "kho-v3" +#define KHO_FDT_COMPATIBLE "kho-v4" /* The FDT property for the preserved memory map. */ #define KHO_FDT_MEMORY_MAP_PROP_NAME "preserved-memory-map" -- cgit v1.2.3