Re: [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
On Wed, 03 Jun 2026 03:28:55 +, Pasha Tatashin wrote: > Entirely remove the LUO FDT wrapper since the FDT only carries the > compatible string and the pointer to the centralized struct luo_ser. > Instead, register the struct luo_ser via the KHO raw subtree > API, placing the compatibility string inside the structure itself. Acked-by: Mike Rapoport (Microsoft) -- Sincerely yours, Mike.
Re: [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
On Wed, Jun 03, 2026 at 09:50:24AM +0300, Mike Rapoport wrote: > # Add your code comments below. There is no need to trim or delete > # any existing content -- just insert your comments under the relevant > # lines of code. Lines starting with "> " are quoted diff context and > # lines starting with "| " are comments from other reviewers. > # The final email will be reformatted automatically to include only > # the sections that have your comments. > # looks like b4 review bug or misuse from my side :) -- Sincerely yours, Mike.
Re: [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
# Add your code comments below. There is no need to trim or delete
# any existing content -- just insert your comments under the relevant
# lines of code. Lines starting with "> " are quoted diff context and
# lines starting with "| " are comments from other reviewers.
# The final email will be reformatted automatically to include only
# the sections that have your comments.
#
> Entirely remove the LUO FDT wrapper since the FDT only carries the
> compatible string and the pointer to the centralized struct luo_ser.
> Instead, register the struct luo_ser via the KHO raw subtree
> API, placing the compatibility string inside the structure itself.
>
> Signed-off-by: Pasha Tatashin
>
> diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
> index 1b2f865a771a..9a4fe491812b 100644
> --- a/include/linux/kho/abi/luo.h
> +++ b/include/linux/kho/abi/luo.h
> @@ -10,11 +10,11 @@
> *
> * Live Update Orchestrator uses the stable Application Binary Interface
> * defined below to pass state from a pre-update kernel to a post-update
> - * kernel. The ABI is built upon the Kexec HandOver framework and uses a
> - * Flattened Device Tree to describe the preserved data.
> + * kernel. The ABI is built upon the Kexec HandOver framework and registers
> + * the central `struct luo_ser` via the KHO raw subtree API.
> *
> - * This interface is a contract. Any modification to the FDT structure, node
> - * properties, compatible strings, or the layout of the `__packed`
> serialization
> + * 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 relevant `_COMPATIBLE` string to
> * prevent a new kernel from misinterpreting data from an old kernel.
> @@ -23,31 +23,15 @@
> * however, backward/forward compatibility is only guaranteed for kernels
> * supporting the same ABI version.
> *
> - * FDT Structure Overview:
> + * KHO Structure Overview:
> * The entire LUO state is encapsulated within a single KHO entry named
> "LUO".
> - * This entry contains an FDT with the following layout:
> - *
> - * .. code-block:: none
> - *
> - * / {
> - * compatible = "luo-v2";
> - * luo-abi-header = ;
> - * };
> - *
> - * Main LUO Node (/):
> - *
> - * - compatible: "luo-v2"
> - * Identifies the overall LUO ABI version.
> - * - luo-abi-header: u64
> - * The physical address of `struct luo_ser`.
> + * This entry contains the `struct luo_ser` structure.
> *
> * Serialization Structures:
> - * The FDT properties point to memory regions containing arrays of simple,
> - * `__packed` structures. These structures contain the actual preserved
> state.
> - *
> * - struct luo_ser:
> * The central ABI structure that contains the overall state of the LUO.
> - * It includes the liveupdate-number and pointers to sessions and FLBs.
> + * It includes the compatibility string, the liveupdate-number, and
> pointers
> + * to sessions and FLBs.
> *
> * - struct luo_session_header_ser:
> * Header for the session array. Contains the total page count of the
> @@ -78,26 +62,27 @@
> #ifndef _LINUX_KHO_ABI_LUO_H
> #define _LINUX_KHO_ABI_LUO_H
>
> +#include
> #include
>
> /*
> - * The LUO FDT hooks all LUO state for sessions, fds, etc.
> + * The LUO state is registered under this KHO entry name.
> */
> -#define LUO_FDT_SIZE PAGE_SIZE
> -#define LUO_FDT_KHO_ENTRY_NAME "LUO"
> -#define LUO_FDT_COMPATIBLE "luo-v2"
> -#define LUO_FDT_ABI_HEADER "luo-abi-header"
> +#define LUO_KHO_ENTRY_NAME "LUO"
> +#define LUO_ABI_COMPATIBLE "luo-v3"
> +#define LUO_ABI_COMPAT_LEN ALIGN(sizeof(LUO_ABI_COMPATIBLE), 8)
>
> /**
> * struct luo_ser - Centralized LUO ABI header.
> + * @compatible: Compatibility string identifying the LUO ABI version.
> * @liveupdate_num: A counter tracking the number of successful live updates.
> * @sessions_pa:Physical address of the first session block header.
> * @flbs_pa:Physical address of the FLB header.
> *
> - * This structure is the root of all preserved LUO state. It is pointed to by
> - * the "luo-abi-header" property in the LUO FDT.
> + * This structure is the root of all preserved LUO state.
> */
> struct luo_ser {
> + char compatible[LUO_ABI_COMPAT_LEN];
> u64 liveupdate_num;
> u64 sessions_pa;
> u64 flbs_pa;
> @@ -111,7 +96,7 @@ struct luo_ser {
> * @data:Private data
> * @token: User provided token for this file
> *
> - * If this structure is modified, LUO_SESSION_COMPATIBLE must be updated.
> + * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
> */
> struct luo_file_ser {
> char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
> @@ -142,7 +127,7 @@ struct luo_file_set_ser {
> * physica
[PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
Entirely remove the LUO FDT wrapper since the FDT only carries the
compatible string and the pointer to the centralized struct luo_ser.
Instead, register the struct luo_ser via the KHO raw subtree
API, placing the compatibility string inside the structure itself.
Signed-off-by: Pasha Tatashin
---
include/linux/kho/abi/luo.h | 57 +---
kernel/liveupdate/luo_core.c | 85 +++-
2 files changed, 46 insertions(+), 96 deletions(-)
diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
index 1b2f865a771a..9a4fe491812b 100644
--- a/include/linux/kho/abi/luo.h
+++ b/include/linux/kho/abi/luo.h
@@ -10,11 +10,11 @@
*
* Live Update Orchestrator uses the stable Application Binary Interface
* defined below to pass state from a pre-update kernel to a post-update
- * kernel. The ABI is built upon the Kexec HandOver framework and uses a
- * Flattened Device Tree to describe the preserved data.
+ * kernel. The ABI is built upon the Kexec HandOver framework and registers
+ * the central `struct luo_ser` via the KHO raw subtree API.
*
- * This interface is a contract. Any modification to the FDT structure, node
- * properties, compatible strings, or the layout of the `__packed`
serialization
+ * 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 relevant `_COMPATIBLE` string to
* prevent a new kernel from misinterpreting data from an old kernel.
@@ -23,31 +23,15 @@
* however, backward/forward compatibility is only guaranteed for kernels
* supporting the same ABI version.
*
- * FDT Structure Overview:
+ * KHO Structure Overview:
* The entire LUO state is encapsulated within a single KHO entry named
"LUO".
- * This entry contains an FDT with the following layout:
- *
- * .. code-block:: none
- *
- * / {
- * compatible = "luo-v2";
- * luo-abi-header = ;
- * };
- *
- * Main LUO Node (/):
- *
- * - compatible: "luo-v2"
- * Identifies the overall LUO ABI version.
- * - luo-abi-header: u64
- * The physical address of `struct luo_ser`.
+ * This entry contains the `struct luo_ser` structure.
*
* Serialization Structures:
- * The FDT properties point to memory regions containing arrays of simple,
- * `__packed` structures. These structures contain the actual preserved
state.
- *
* - struct luo_ser:
* The central ABI structure that contains the overall state of the LUO.
- * It includes the liveupdate-number and pointers to sessions and FLBs.
+ * It includes the compatibility string, the liveupdate-number, and
pointers
+ * to sessions and FLBs.
*
* - struct luo_session_header_ser:
* Header for the session array. Contains the total page count of the
@@ -78,26 +62,27 @@
#ifndef _LINUX_KHO_ABI_LUO_H
#define _LINUX_KHO_ABI_LUO_H
+#include
#include
/*
- * The LUO FDT hooks all LUO state for sessions, fds, etc.
+ * The LUO state is registered under this KHO entry name.
*/
-#define LUO_FDT_SIZE PAGE_SIZE
-#define LUO_FDT_KHO_ENTRY_NAME "LUO"
-#define LUO_FDT_COMPATIBLE "luo-v2"
-#define LUO_FDT_ABI_HEADER "luo-abi-header"
+#define LUO_KHO_ENTRY_NAME "LUO"
+#define LUO_ABI_COMPATIBLE "luo-v3"
+#define LUO_ABI_COMPAT_LEN ALIGN(sizeof(LUO_ABI_COMPATIBLE), 8)
/**
* struct luo_ser - Centralized LUO ABI header.
+ * @compatible: Compatibility string identifying the LUO ABI version.
* @liveupdate_num: A counter tracking the number of successful live updates.
* @sessions_pa:Physical address of the first session block header.
* @flbs_pa:Physical address of the FLB header.
*
- * This structure is the root of all preserved LUO state. It is pointed to by
- * the "luo-abi-header" property in the LUO FDT.
+ * This structure is the root of all preserved LUO state.
*/
struct luo_ser {
+ char compatible[LUO_ABI_COMPAT_LEN];
u64 liveupdate_num;
u64 sessions_pa;
u64 flbs_pa;
@@ -111,7 +96,7 @@ struct luo_ser {
* @data:Private data
* @token: User provided token for this file
*
- * If this structure is modified, LUO_SESSION_COMPATIBLE must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_file_ser {
char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
@@ -142,7 +127,7 @@ struct luo_file_set_ser {
* physical memory preserved across the kexec. It provides the necessary
* metadata to interpret the array of session entries that follow.
*
- * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_session_header_ser {
u64 count;
@@ -159,7 +144,7 @@ struct luo_session_header_ser {
* session) i
