kho: relocate vmalloc preservation structure to KHO ABI header

The `struct kho_vmalloc` defines the in-memory layout for preserving
vmalloc regions across kexec.  This layout is a contract between kernels
and part of the KHO ABI.

To reflect this relationship, the related structs and helper macros are
relocated to the ABI header, `include/linux/kho/abi/kexec_handover.h`. 
This move places the structure's definition under the protection of the
KHO_FDT_COMPATIBLE version string.

The structure and its components are now also documented within the ABI
header to describe the contract and prevent ABI breaks.

[rppt@kernel.org: update comment, per Pratyush]
  Link: https://lkml.kernel.org/r/aW_Mqp6HcqLwQImS@kernel.org
Link: https://lkml.kernel.org/r/20260105165839.285270-6-rppt@kernel.org
Signed-off-by: Jason Miu <jasonmiu@google.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 2 insertions, 25 deletions

diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 5f7b9de97e8d..a56ff3ffaf17 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -11,34 +11,11 @@ struct kho_scratch {
 	phys_addr_t size;
 };
 
+struct kho_vmalloc;
+
 struct folio;
 struct page;
 
-#define DECLARE_KHOSER_PTR(name, type) \
-	union {                        \
-		phys_addr_t phys;      \
-		type ptr;              \
-	} name
-#define KHOSER_STORE_PTR(dest, val)               \
-	({                                        \
-		typeof(val) v = val;              \
-		typecheck(typeof((dest).ptr), v); \
-		(dest).phys = virt_to_phys(v);    \
-	})
-#define KHOSER_LOAD_PTR(src)                                                 \
-	({                                                                   \
-		typeof(src) s = src;                                         \
-		(typeof((s).ptr))((s).phys ? phys_to_virt((s).phys) : NULL); \
-	})
-
-struct kho_vmalloc_chunk;
-struct kho_vmalloc {
-	DECLARE_KHOSER_PTR(first, struct kho_vmalloc_chunk *);
-	unsigned int total_pages;
-	unsigned short flags;
-	unsigned short order;
-};
-
 #ifdef CONFIG_KEXEC_HANDOVER
 bool kho_is_enabled(void);
 bool is_kho_boot(void);