liveupdate: centralize state management into struct luo_ser

Transition the LUO to ABI v2, which centralizes state management into a
single struct luo_ser header.

Previously, LUO state was spread across multiple FDT properties and
subnodes. ABI v2 simplifies this by placing all core state, including
the liveupdate number and physical addresses for sessions and FLB
headers into a centralized struct luo_ser.

Note that this change introduces a semantic difference: the sessions
and FLB serialization formats are no longer completely independent of
the core LUO. Their metadata (such as physical addresses for sessions
and FLB headers) is now coupled to and managed via the centralized
struct luo_ser.

Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://patch.msgid.link/20260603154402.468928-4-pasha.tatashin@soleen.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

1 files changed, 31 insertions, 60 deletions

diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
index 46750a0ddf88..1b2f865a771a 100644
--- a/include/linux/kho/abi/luo.h
+++ b/include/linux/kho/abi/luo.h
@@ -30,52 +30,25 @@
  *   .. code-block:: none
  *
  *     / {
- *         compatible = "luo-v1";
- *         liveupdate-number = <...>;
- *
- *         luo-session {
- *             compatible = "luo-session-v1";
- *             luo-session-header = <phys_addr_of_session_header_ser>;
- *         };
- *
- *         luo-flb {
- *             compatible = "luo-flb-v1";
- *             luo-flb-header = <phys_addr_of_flb_header_ser>;
- *         };
+ *         compatible = "luo-v2";
+ *         luo-abi-header = <phys_addr_of_luo_ser>;
  *     };
  *
  * Main LUO Node (/):
  *
- *   - compatible: "luo-v1"
+ *   - compatible: "luo-v2"
  *     Identifies the overall LUO ABI version.
- *   - liveupdate-number: u64
- *     A counter tracking the number of successful live updates performed.
- *
- * Session Node (luo-session):
- *   This node describes all preserved user-space sessions.
- *
- *   - compatible: "luo-session-v1"
- *     Identifies the session ABI version.
- *   - luo-session-header: u64
- *     The physical address of a `struct luo_session_header_ser`. This structure
- *     is the header for a contiguous block of memory containing an array of
- *     `struct luo_session_ser`, one for each preserved session.
- *
- * File-Lifecycle-Bound Node (luo-flb):
- *   This node describes all preserved global objects whose lifecycle is bound
- *   to that of the preserved files (e.g., shared IOMMU state).
- *
- *   - compatible: "luo-flb-v1"
- *     Identifies the FLB ABI version.
- *   - luo-flb-header: u64
- *     The physical address of a `struct luo_flb_header_ser`. This structure is
- *     the header for a contiguous block of memory containing an array of
- *     `struct luo_flb_ser`, one for each preserved global object.
+ *   - luo-abi-header: u64
+ *     The physical address of `struct luo_ser`.
  *
  * 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.
+ *
  *   - struct luo_session_header_ser:
  *     Header for the session array. Contains the total page count of the
  *     preserved memory block and the number of `struct luo_session_ser`
@@ -109,13 +82,26 @@
 
 /*
  * The LUO FDT hooks all LUO state for sessions, fds, etc.
- * In the root it also carries "liveupdate-number" 64-bit property that
- * corresponds to the number of live-updates performed on this machine.
  */
 #define LUO_FDT_SIZE		PAGE_SIZE
 #define LUO_FDT_KHO_ENTRY_NAME	"LUO"
-#define LUO_FDT_COMPATIBLE	"luo-v1"
-#define LUO_FDT_LIVEUPDATE_NUM	"liveupdate-number"
+#define LUO_FDT_COMPATIBLE	"luo-v2"
+#define LUO_FDT_ABI_HEADER	"luo-abi-header"
+
+/**
+ * struct luo_ser - Centralized LUO ABI header.
+ * @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.
+ */
+struct luo_ser {
+	u64 liveupdate_num;
+	u64 sessions_pa;
+	u64 flbs_pa;
+} __packed;
 
 #define LIVEUPDATE_HNDL_COMPAT_LENGTH	48
 
@@ -147,15 +133,6 @@ struct luo_file_set_ser {
 	u64 count;
 } __packed;
 
-/*
- * LUO FDT session node
- * LUO_FDT_SESSION_HEADER:  is a u64 physical address of struct
- *                          luo_session_header_ser
- */
-#define LUO_FDT_SESSION_NODE_NAME	"luo-session"
-#define LUO_FDT_SESSION_COMPATIBLE	"luo-session-v2"
-#define LUO_FDT_SESSION_HEADER		"luo-session-header"
-
 /**
  * struct luo_session_header_ser - Header for the serialized session data block.
  * @count: The number of `struct luo_session_ser` entries that immediately
@@ -165,7 +142,7 @@ 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_SESSION_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
  */
 struct luo_session_header_ser {
 	u64 count;
@@ -182,7 +159,7 @@ struct luo_session_header_ser {
  * session) is created and passed to the new kernel, allowing it to reconstruct
  * the session context.
  *
- * If this structure is modified, `LUO_FDT_SESSION_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
  */
 struct luo_session_ser {
 	char name[LIVEUPDATE_SESSION_NAME_LENGTH];
@@ -192,10 +169,6 @@ struct luo_session_ser {
 /* The max size is set so it can be reliably used during in serialization */
 #define LIVEUPDATE_FLB_COMPAT_LENGTH	48
 
-#define LUO_FDT_FLB_NODE_NAME	"luo-flb"
-#define LUO_FDT_FLB_COMPATIBLE	"luo-flb-v1"
-#define LUO_FDT_FLB_HEADER	"luo-flb-header"
-
 /**
  * struct luo_flb_header_ser - Header for the serialized FLB data block.
  * @pgcnt: The total number of pages occupied by the entire preserved memory
@@ -205,11 +178,9 @@ struct luo_session_ser {
  *         in the memory block.
  *
  * This structure is located at the physical address specified by the
- * `LUO_FDT_FLB_HEADER` FDT property. It provides the new kernel with the
- * necessary information to find and iterate over the array of preserved
- * File-Lifecycle-Bound objects and to manage the underlying memory.
+ * flbs_pa in luo_ser.
  *
- * If this structure is modified, LUO_FDT_FLB_COMPATIBLE must be updated.
+ * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
  */
 struct luo_flb_header_ser {
 	u64 pgcnt;
@@ -231,7 +202,7 @@ struct luo_flb_header_ser {
  * passed to the new kernel. Each entry allows the LUO core to restore one
  * global, shared object.
  *
- * If this structure is modified, LUO_FDT_FLB_COMPATIBLE must be updated.
+ * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
  */
 struct luo_flb_ser {
 	char name[LIVEUPDATE_FLB_COMPAT_LENGTH];