* [PATCH v6 01/13] liveupdate: change file_set->count type to u64 for type safety
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 3:28 ` [PATCH v6 02/13] liveupdate: avoid mixing cleanup guards with goto in luo_session_retrieve_fd Pasha Tatashin
` (11 subsequent siblings)
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
This improves type safety and aligns the in-memory file_set->count with
the serialized count type. It avoids potential truncation or sign
conversion mismatch issues.
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>
---
kernel/liveupdate/luo_internal.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index dd53d4a7277e..ae58206f14ac 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -52,7 +52,7 @@ static inline int luo_ucmd_respond(struct luo_ucmd *ucmd,
struct luo_file_set {
struct list_head files_list;
struct luo_file_ser *files;
- long count;
+ u64 count;
};
/**
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 02/13] liveupdate: avoid mixing cleanup guards with goto in luo_session_retrieve_fd
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
2026-06-03 3:28 ` [PATCH v6 01/13] liveupdate: change file_set->count type to u64 for type safety Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 6:52 ` Mike Rapoport
2026-06-03 3:28 ` [PATCH v6 03/13] liveupdate: centralize state management into struct luo_ser Pasha Tatashin
` (10 subsequent siblings)
12 siblings, 1 reply; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
Refactoring luo_session_retrieve_fd() to avoid mixing automated
cleanup-style guards with goto-based resource release, which is not
recommended under the Linux kernel coding style.
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_session.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 5c6cebc6e326..47566db64598 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -291,10 +291,11 @@ static int luo_session_retrieve_fd(struct luo_session *session,
if (argp->fd < 0)
return argp->fd;
- guard(mutex)(&session->mutex);
+ mutex_lock(&session->mutex);
err = luo_retrieve_file(&session->file_set, argp->token, &file);
+ mutex_unlock(&session->mutex);
if (err < 0)
- goto err_put_fd;
+ goto err_put_fd;
err = luo_ucmd_respond(ucmd, sizeof(*argp));
if (err)
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* Re: [PATCH v6 02/13] liveupdate: avoid mixing cleanup guards with goto in luo_session_retrieve_fd
2026-06-03 3:28 ` [PATCH v6 02/13] liveupdate: avoid mixing cleanup guards with goto in luo_session_retrieve_fd Pasha Tatashin
@ 2026-06-03 6:52 ` Mike Rapoport
0 siblings, 0 replies; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 6:52 UTC (permalink / raw)
To: Pasha Tatashin
Cc: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, dmatlack, kexec, pratyush, skhawaja, graf
On Wed, 03 Jun 2026 03:28:53 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> Refactoring luo_session_retrieve_fd() to avoid mixing automated
> cleanup-style guards with goto-based resource release, which is not
> recommended under the Linux kernel coding style.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 27+ messages in thread
* [PATCH v6 03/13] liveupdate: centralize state management into struct luo_ser
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
2026-06-03 3:28 ` [PATCH v6 01/13] liveupdate: change file_set->count type to u64 for type safety Pasha Tatashin
2026-06-03 3:28 ` [PATCH v6 02/13] liveupdate: avoid mixing cleanup guards with goto in luo_session_retrieve_fd Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 6:52 ` Mike Rapoport
2026-06-03 3:28 ` [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree Pasha Tatashin
` (9 subsequent siblings)
12 siblings, 1 reply; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
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>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/kho/abi/luo.h | 91 +++++++++++---------------------
kernel/liveupdate/luo_core.c | 64 +++++++++++++++-------
kernel/liveupdate/luo_flb.c | 60 +++------------------
kernel/liveupdate/luo_internal.h | 8 +--
kernel/liveupdate/luo_session.c | 64 ++++------------------
5 files changed, 96 insertions(+), 191 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];
diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 5d5827ced73c..085c0dfc1ef1 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -61,7 +61,6 @@
#include <linux/rwsem.h>
#include <linux/sizes.h>
#include <linux/string.h>
-#include <linux/unaligned.h>
#include "kexec_handover_internal.h"
#include "luo_internal.h"
@@ -86,9 +85,11 @@ early_param("liveupdate", early_liveupdate_param);
static int __init luo_early_startup(void)
{
+ struct luo_ser *luo_ser;
+ int err, header_size;
phys_addr_t fdt_phys;
- int err, ln_size;
const void *ptr;
+ u64 luo_ser_pa;
if (!kho_is_enabled()) {
if (liveupdate_enabled())
@@ -119,26 +120,32 @@ static int __init luo_early_startup(void)
return -EINVAL;
}
- ln_size = 0;
- ptr = fdt_getprop(luo_global.fdt_in, 0, LUO_FDT_LIVEUPDATE_NUM,
- &ln_size);
- if (!ptr || ln_size != sizeof(luo_global.liveupdate_num)) {
- pr_err("Unable to get live update number '%s' [%d]\n",
- LUO_FDT_LIVEUPDATE_NUM, ln_size);
+ header_size = 0;
+ ptr = fdt_getprop(luo_global.fdt_in, 0, LUO_FDT_ABI_HEADER, &header_size);
+ if (!ptr || header_size != sizeof(u64)) {
+ pr_err("Unable to get ABI header '%s' [%d]\n",
+ LUO_FDT_ABI_HEADER, header_size);
return -EINVAL;
}
- luo_global.liveupdate_num = get_unaligned((u64 *)ptr);
+ luo_ser_pa = get_unaligned((u64 *)ptr);
+ luo_ser = phys_to_virt(luo_ser_pa);
+
+ luo_global.liveupdate_num = luo_ser->liveupdate_num;
pr_info("Retrieved live update data, liveupdate number: %lld\n",
luo_global.liveupdate_num);
- err = luo_session_setup_incoming(luo_global.fdt_in);
+ err = luo_session_setup_incoming(luo_ser->sessions_pa);
if (err)
- return err;
+ goto out_free_ser;
+
+ luo_flb_setup_incoming(luo_ser->flbs_pa);
- err = luo_flb_setup_incoming(luo_global.fdt_in);
+ err = 0;
+out_free_ser:
+ kho_restore_free(luo_ser);
return err;
}
@@ -160,7 +167,8 @@ early_initcall(liveupdate_early_init);
/* Called during boot to create outgoing LUO fdt tree */
static int __init luo_fdt_setup(void)
{
- const u64 ln = luo_global.liveupdate_num + 1;
+ struct luo_ser *luo_ser;
+ u64 luo_ser_pa;
void *fdt_out;
int err;
@@ -170,27 +178,45 @@ static int __init luo_fdt_setup(void)
return PTR_ERR(fdt_out);
}
+ luo_ser = kho_alloc_preserve(sizeof(*luo_ser));
+ if (IS_ERR(luo_ser)) {
+ err = PTR_ERR(luo_ser);
+ goto exit_free_fdt;
+ }
+ luo_ser_pa = virt_to_phys(luo_ser);
+
err = fdt_create(fdt_out, LUO_FDT_SIZE);
err |= fdt_finish_reservemap(fdt_out);
err |= fdt_begin_node(fdt_out, "");
err |= fdt_property_string(fdt_out, "compatible", LUO_FDT_COMPATIBLE);
- err |= fdt_property(fdt_out, LUO_FDT_LIVEUPDATE_NUM, &ln, sizeof(ln));
- err |= luo_session_setup_outgoing(fdt_out);
- err |= luo_flb_setup_outgoing(fdt_out);
+ err |= fdt_property(fdt_out, LUO_FDT_ABI_HEADER, &luo_ser_pa,
+ sizeof(luo_ser_pa));
err |= fdt_end_node(fdt_out);
err |= fdt_finish(fdt_out);
if (err)
- goto exit_free;
+ goto exit_free_luo_ser;
+
+ err = luo_session_setup_outgoing(&luo_ser->sessions_pa);
+ if (err)
+ goto exit_free_luo_ser;
+
+ err = luo_flb_setup_outgoing(&luo_ser->flbs_pa);
+ if (err)
+ goto exit_free_luo_ser;
+
+ luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
err = kho_add_subtree(LUO_FDT_KHO_ENTRY_NAME, fdt_out,
fdt_totalsize(fdt_out));
if (err)
- goto exit_free;
+ goto exit_free_luo_ser;
luo_global.fdt_out = fdt_out;
return 0;
-exit_free:
+exit_free_luo_ser:
+ kho_unpreserve_free(luo_ser);
+exit_free_fdt:
kho_unpreserve_free(fdt_out);
pr_err("failed to prepare LUO FDT: %d\n", err);
diff --git a/kernel/liveupdate/luo_flb.c b/kernel/liveupdate/luo_flb.c
index 8f5c5dd01cd0..5c27134ce7ba 100644
--- a/kernel/liveupdate/luo_flb.c
+++ b/kernel/liveupdate/luo_flb.c
@@ -44,13 +44,11 @@
#include <linux/io.h>
#include <linux/kexec_handover.h>
#include <linux/kho/abi/luo.h>
-#include <linux/libfdt.h>
#include <linux/list_private.h>
#include <linux/liveupdate.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
-#include <linux/unaligned.h>
#include "luo_internal.h"
#define LUO_FLB_PGCNT 1ul
@@ -551,27 +549,15 @@ int liveupdate_flb_get_outgoing(struct liveupdate_flb *flb, void **objp)
return 0;
}
-int __init luo_flb_setup_outgoing(void *fdt_out)
+int __init luo_flb_setup_outgoing(u64 *flbs_pa)
{
struct luo_flb_header_ser *header_ser;
- u64 header_ser_pa;
- int err;
header_ser = kho_alloc_preserve(LUO_FLB_PGCNT << PAGE_SHIFT);
if (IS_ERR(header_ser))
return PTR_ERR(header_ser);
- header_ser_pa = virt_to_phys(header_ser);
-
- err = fdt_begin_node(fdt_out, LUO_FDT_FLB_NODE_NAME);
- err |= fdt_property_string(fdt_out, "compatible",
- LUO_FDT_FLB_COMPATIBLE);
- err |= fdt_property(fdt_out, LUO_FDT_FLB_HEADER, &header_ser_pa,
- sizeof(header_ser_pa));
- err |= fdt_end_node(fdt_out);
-
- if (err)
- goto err_unpreserve;
+ *flbs_pa = virt_to_phys(header_ser);
header_ser->pgcnt = LUO_FLB_PGCNT;
luo_flb_global.outgoing.header_ser = header_ser;
@@ -579,53 +565,19 @@ int __init luo_flb_setup_outgoing(void *fdt_out)
luo_flb_global.outgoing.active = true;
return 0;
-
-err_unpreserve:
- kho_unpreserve_free(header_ser);
-
- return err;
}
-int __init luo_flb_setup_incoming(void *fdt_in)
+void __init luo_flb_setup_incoming(u64 flbs_pa)
{
struct luo_flb_header_ser *header_ser;
- int err, header_size, offset;
- const void *ptr;
- u64 header_ser_pa;
-
- offset = fdt_subnode_offset(fdt_in, 0, LUO_FDT_FLB_NODE_NAME);
- if (offset < 0) {
- pr_err("Unable to get FLB node [%s]\n", LUO_FDT_FLB_NODE_NAME);
-
- return -ENOENT;
- }
-
- err = fdt_node_check_compatible(fdt_in, offset,
- LUO_FDT_FLB_COMPATIBLE);
- if (err) {
- pr_err("FLB node is incompatible with '%s' [%d]\n",
- LUO_FDT_FLB_COMPATIBLE, err);
-
- return -EINVAL;
- }
-
- header_size = 0;
- ptr = fdt_getprop(fdt_in, offset, LUO_FDT_FLB_HEADER, &header_size);
- if (!ptr || header_size != sizeof(u64)) {
- pr_err("Unable to get FLB header property '%s' [%d]\n",
- LUO_FDT_FLB_HEADER, header_size);
- return -EINVAL;
- }
-
- header_ser_pa = get_unaligned((u64 *)ptr);
- header_ser = phys_to_virt(header_ser_pa);
+ if (!flbs_pa)
+ return;
+ header_ser = phys_to_virt(flbs_pa);
luo_flb_global.incoming.header_ser = header_ser;
luo_flb_global.incoming.ser = (void *)(header_ser + 1);
luo_flb_global.incoming.active = true;
-
- return 0;
}
/**
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index ae58206f14ac..fe22086bfbeb 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -79,8 +79,8 @@ extern struct rw_semaphore luo_register_rwlock;
int luo_session_create(const char *name, struct file **filep);
int luo_session_retrieve(const char *name, struct file **filep);
-int __init luo_session_setup_outgoing(void *fdt);
-int __init luo_session_setup_incoming(void *fdt);
+int __init luo_session_setup_outgoing(u64 *sessions_pa);
+int __init luo_session_setup_incoming(u64 sessions_pa);
int luo_session_serialize(void);
int luo_session_deserialize(void);
@@ -102,8 +102,8 @@ int luo_flb_file_preserve(struct liveupdate_file_handler *fh);
void luo_flb_file_unpreserve(struct liveupdate_file_handler *fh);
void luo_flb_file_finish(struct liveupdate_file_handler *fh);
void luo_flb_unregister_all(struct liveupdate_file_handler *fh);
-int __init luo_flb_setup_outgoing(void *fdt);
-int __init luo_flb_setup_incoming(void *fdt);
+int __init luo_flb_setup_outgoing(u64 *flbs_pa);
+void __init luo_flb_setup_incoming(u64 flbs_pa);
void luo_flb_serialize(void);
#ifdef CONFIG_LIVEUPDATE_TEST
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 47566db64598..85782c6f3d6c 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -25,9 +25,8 @@
*
* - Serialization: Session metadata is preserved using the KHO framework. When
* a live update is triggered via kexec, an array of `struct luo_session_ser`
- * is populated and placed in a preserved memory region. An FDT node is also
- * created, containing the count of sessions and the physical address of this
- * array.
+ * is populated and placed in a preserved memory region. The physical address
+ * of this array is stored in the centralized `struct luo_ser` structure.
*
* Session Lifecycle:
*
@@ -91,13 +90,11 @@
#include <linux/io.h>
#include <linux/kexec_handover.h>
#include <linux/kho/abi/luo.h>
-#include <linux/libfdt.h>
#include <linux/list.h>
#include <linux/liveupdate.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
-#include <linux/unaligned.h>
#include <uapi/linux/liveupdate.h>
#include "luo_internal.h"
@@ -527,75 +524,34 @@ int luo_session_retrieve(const char *name, struct file **filep)
return err;
}
-int __init luo_session_setup_outgoing(void *fdt_out)
+int __init luo_session_setup_outgoing(u64 *sessions_pa)
{
struct luo_session_header_ser *header_ser;
- u64 header_ser_pa;
- int err;
header_ser = kho_alloc_preserve(LUO_SESSION_PGCNT << PAGE_SHIFT);
if (IS_ERR(header_ser))
return PTR_ERR(header_ser);
- header_ser_pa = virt_to_phys(header_ser);
-
- err = fdt_begin_node(fdt_out, LUO_FDT_SESSION_NODE_NAME);
- err |= fdt_property_string(fdt_out, "compatible",
- LUO_FDT_SESSION_COMPATIBLE);
- err |= fdt_property(fdt_out, LUO_FDT_SESSION_HEADER, &header_ser_pa,
- sizeof(header_ser_pa));
- err |= fdt_end_node(fdt_out);
- if (err)
- goto err_unpreserve;
+ *sessions_pa = virt_to_phys(header_ser);
luo_session_global.outgoing.header_ser = header_ser;
luo_session_global.outgoing.ser = (void *)(header_ser + 1);
luo_session_global.outgoing.active = true;
return 0;
-
-err_unpreserve:
- kho_unpreserve_free(header_ser);
- return err;
}
-int __init luo_session_setup_incoming(void *fdt_in)
+int __init luo_session_setup_incoming(u64 sessions_pa)
{
struct luo_session_header_ser *header_ser;
- int err, header_size, offset;
- u64 header_ser_pa;
- const void *ptr;
-
- offset = fdt_subnode_offset(fdt_in, 0, LUO_FDT_SESSION_NODE_NAME);
- if (offset < 0) {
- pr_err("Unable to get session node: [%s]\n",
- LUO_FDT_SESSION_NODE_NAME);
- return -EINVAL;
- }
- err = fdt_node_check_compatible(fdt_in, offset,
- LUO_FDT_SESSION_COMPATIBLE);
- if (err) {
- pr_err("Session node incompatible [%s]\n",
- LUO_FDT_SESSION_COMPATIBLE);
- return -EINVAL;
- }
-
- header_size = 0;
- ptr = fdt_getprop(fdt_in, offset, LUO_FDT_SESSION_HEADER, &header_size);
- if (!ptr || header_size != sizeof(u64)) {
- pr_err("Unable to get session header '%s' [%d]\n",
- LUO_FDT_SESSION_HEADER, header_size);
- return -EINVAL;
+ if (sessions_pa) {
+ header_ser = phys_to_virt(sessions_pa);
+ luo_session_global.incoming.header_ser = header_ser;
+ luo_session_global.incoming.ser = (void *)(header_ser + 1);
+ luo_session_global.incoming.active = true;
}
- header_ser_pa = get_unaligned((u64 *)ptr);
- header_ser = phys_to_virt(header_ser_pa);
-
- luo_session_global.incoming.header_ser = header_ser;
- luo_session_global.incoming.ser = (void *)(header_ser + 1);
- luo_session_global.incoming.active = true;
-
return 0;
}
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* Re: [PATCH v6 03/13] liveupdate: centralize state management into struct luo_ser
2026-06-03 3:28 ` [PATCH v6 03/13] liveupdate: centralize state management into struct luo_ser Pasha Tatashin
@ 2026-06-03 6:52 ` Mike Rapoport
0 siblings, 0 replies; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 6:52 UTC (permalink / raw)
To: Pasha Tatashin
Cc: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, dmatlack, kexec, pratyush, skhawaja, graf
On Wed, 03 Jun 2026 03:28:54 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> 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.
>
> [...]
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 27+ messages in thread
* [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (2 preceding siblings ...)
2026-06-03 3:28 ` [PATCH v6 03/13] liveupdate: centralize state management into struct luo_ser Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 6:50 ` Mike Rapoport
2026-06-03 13:31 ` Mike Rapoport
2026-06-03 3:28 ` [PATCH v6 05/13] liveupdate: Extract luo_file_deserialize_one helper Pasha Tatashin
` (8 subsequent siblings)
12 siblings, 2 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
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 <pasha.tatashin@soleen.com>
---
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 = <phys_addr_of_luo_ser>;
- * };
- *
- * 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 <linux/align.h>
#include <uapi/linux/liveupdate.h>
/*
- * 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) is created and passed to the new kernel, allowing it to reconstruct
* the session context.
*
- * 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_ser {
char name[LIVEUPDATE_SESSION_NAME_LENGTH];
@@ -180,7 +165,7 @@ struct luo_session_ser {
* This structure is located at the physical address specified by the
* flbs_pa in luo_ser.
*
- * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_flb_header_ser {
u64 pgcnt;
@@ -202,7 +187,7 @@ 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_COMPATIBLE` must be updated.
+ * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
*/
struct luo_flb_ser {
char name[LIVEUPDATE_FLB_COMPAT_LENGTH];
diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 085c0dfc1ef1..69b00e7d0f8f 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -54,7 +54,6 @@
#include <linux/kexec_handover.h>
#include <linux/kho/abi/luo.h>
#include <linux/kobject.h>
-#include <linux/libfdt.h>
#include <linux/liveupdate.h>
#include <linux/miscdevice.h>
#include <linux/mm.h>
@@ -67,8 +66,7 @@
static struct {
bool enabled;
- void *fdt_out;
- void *fdt_in;
+ struct luo_ser *luo_ser_out;
u64 liveupdate_num;
} luo_global;
@@ -85,11 +83,10 @@ early_param("liveupdate", early_liveupdate_param);
static int __init luo_early_startup(void)
{
+ phys_addr_t luo_ser_phys;
struct luo_ser *luo_ser;
- int err, header_size;
- phys_addr_t fdt_phys;
- const void *ptr;
- u64 luo_ser_pa;
+ size_t len;
+ int err;
if (!kho_is_enabled()) {
if (liveupdate_enabled())
@@ -98,40 +95,29 @@ static int __init luo_early_startup(void)
return 0;
}
- /* Retrieve LUO subtree, and verify its format. */
- err = kho_retrieve_subtree(LUO_FDT_KHO_ENTRY_NAME, &fdt_phys, NULL);
+ /* Retrieve LUO state from KHO. */
+ err = kho_retrieve_subtree(LUO_KHO_ENTRY_NAME, &luo_ser_phys, &len);
if (err) {
if (err != -ENOENT) {
- pr_err("failed to retrieve FDT '%s' from KHO: %pe\n",
- LUO_FDT_KHO_ENTRY_NAME, ERR_PTR(err));
+ pr_err("failed to retrieve LUO state '%s' from KHO: %pe\n",
+ LUO_KHO_ENTRY_NAME, ERR_PTR(err));
return err;
}
return 0;
}
- luo_global.fdt_in = phys_to_virt(fdt_phys);
- err = fdt_node_check_compatible(luo_global.fdt_in, 0,
- LUO_FDT_COMPATIBLE);
- if (err) {
- pr_err("FDT '%s' is incompatible with '%s' [%d]\n",
- LUO_FDT_KHO_ENTRY_NAME, LUO_FDT_COMPATIBLE, err);
-
+ if (len < sizeof(*luo_ser)) {
+ pr_err("LUO state is too small (%zu < %zu)\n", len, sizeof(*luo_ser));
return -EINVAL;
}
- header_size = 0;
- ptr = fdt_getprop(luo_global.fdt_in, 0, LUO_FDT_ABI_HEADER, &header_size);
- if (!ptr || header_size != sizeof(u64)) {
- pr_err("Unable to get ABI header '%s' [%d]\n",
- LUO_FDT_ABI_HEADER, header_size);
-
+ luo_ser = phys_to_virt(luo_ser_phys);
+ if (strncmp(luo_ser->compatible, LUO_ABI_COMPATIBLE, LUO_ABI_COMPAT_LEN)) {
+ pr_err("LUO state is incompatible with '%s'\n", LUO_ABI_COMPATIBLE);
return -EINVAL;
}
- luo_ser_pa = get_unaligned((u64 *)ptr);
- luo_ser = phys_to_virt(luo_ser_pa);
-
luo_global.liveupdate_num = luo_ser->liveupdate_num;
pr_info("Retrieved live update data, liveupdate number: %lld\n",
luo_global.liveupdate_num);
@@ -164,37 +150,20 @@ static int __init liveupdate_early_init(void)
}
early_initcall(liveupdate_early_init);
-/* Called during boot to create outgoing LUO fdt tree */
-static int __init luo_fdt_setup(void)
+/* Called during boot to create outgoing LUO state */
+static int __init luo_state_setup(void)
{
struct luo_ser *luo_ser;
- u64 luo_ser_pa;
- void *fdt_out;
int err;
- fdt_out = kho_alloc_preserve(LUO_FDT_SIZE);
- if (IS_ERR(fdt_out)) {
- pr_err("failed to allocate/preserve FDT memory\n");
- return PTR_ERR(fdt_out);
- }
-
luo_ser = kho_alloc_preserve(sizeof(*luo_ser));
if (IS_ERR(luo_ser)) {
- err = PTR_ERR(luo_ser);
- goto exit_free_fdt;
+ pr_err("failed to allocate/preserve LUO state memory\n");
+ return PTR_ERR(luo_ser);
}
- luo_ser_pa = virt_to_phys(luo_ser);
-
- err = fdt_create(fdt_out, LUO_FDT_SIZE);
- err |= fdt_finish_reservemap(fdt_out);
- err |= fdt_begin_node(fdt_out, "");
- err |= fdt_property_string(fdt_out, "compatible", LUO_FDT_COMPATIBLE);
- err |= fdt_property(fdt_out, LUO_FDT_ABI_HEADER, &luo_ser_pa,
- sizeof(luo_ser_pa));
- err |= fdt_end_node(fdt_out);
- err |= fdt_finish(fdt_out);
- if (err)
- goto exit_free_luo_ser;
+
+ strscpy(luo_ser->compatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser->compatible));
+ luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
err = luo_session_setup_outgoing(&luo_ser->sessions_pa);
if (err)
@@ -204,21 +173,17 @@ static int __init luo_fdt_setup(void)
if (err)
goto exit_free_luo_ser;
- luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
-
- err = kho_add_subtree(LUO_FDT_KHO_ENTRY_NAME, fdt_out,
- fdt_totalsize(fdt_out));
+ err = kho_add_subtree(LUO_KHO_ENTRY_NAME, luo_ser, sizeof(*luo_ser));
if (err)
goto exit_free_luo_ser;
- luo_global.fdt_out = fdt_out;
+
+ luo_global.luo_ser_out = luo_ser;
return 0;
exit_free_luo_ser:
kho_unpreserve_free(luo_ser);
-exit_free_fdt:
- kho_unpreserve_free(fdt_out);
- pr_err("failed to prepare LUO FDT: %d\n", err);
+ pr_err("failed to prepare LUO state: %d\n", err);
return err;
}
@@ -234,7 +199,7 @@ static int __init luo_late_startup(void)
if (!liveupdate_enabled())
return 0;
- err = luo_fdt_setup();
+ err = luo_state_setup();
if (err)
luo_global.enabled = false;
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* Re: [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
2026-06-03 3:28 ` [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree Pasha Tatashin
@ 2026-06-03 6:50 ` Mike Rapoport
2026-06-03 9:32 ` Mike Rapoport
2026-06-03 13:31 ` Mike Rapoport
1 sibling, 1 reply; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 6:50 UTC (permalink / raw)
To: Pasha Tatashin
Cc: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, dmatlack, kexec, pratyush, skhawaja, graf
# 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 <pasha.tatashin@soleen.com>
>
> 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 = <phys_addr_of_luo_ser>;
> - * };
> - *
> - * 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 <linux/align.h>
> #include <uapi/linux/liveupdate.h>
>
> /*
> - * 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) is created and passed to the new kernel, allowing it to reconstruct
> * the session context.
> *
> - * 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_ser {
> char name[LIVEUPDATE_SESSION_NAME_LENGTH];
> @@ -180,7 +165,7 @@ struct luo_session_ser {
> * This structure is located at the physical address specified by the
> * flbs_pa in luo_ser.
> *
> - * If this structure is modified, `LUO_FDT_COMPATIBLE` must be updated.
> + * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
> */
> struct luo_flb_header_ser {
> u64 pgcnt;
> @@ -202,7 +187,7 @@ 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_COMPATIBLE` must be updated.
> + * If this structure is modified, `LUO_ABI_COMPATIBLE` must be updated.
> */
> struct luo_flb_ser {
> char name[LIVEUPDATE_FLB_COMPAT_LENGTH];
> diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
> index fbc18c5f4230..e261a03a1b47 100644
> --- a/kernel/liveupdate/luo_core.c
> +++ b/kernel/liveupdate/luo_core.c
> @@ -50,7 +50,6 @@
> #include <linux/kexec_handover.h>
> #include <linux/kho/abi/luo.h>
> #include <linux/kobject.h>
> -#include <linux/libfdt.h>
> #include <linux/liveupdate.h>
> #include <linux/miscdevice.h>
> #include <linux/mm.h>
> @@ -63,8 +62,7 @@
>
> static struct {
> bool enabled;
> - void *fdt_out;
> - void *fdt_in;
> + struct luo_ser *luo_ser_out;
> u64 liveupdate_num;
> } luo_global;
>
> @@ -81,11 +79,10 @@ early_param("liveupdate", early_liveupdate_param);
>
> static int __init luo_early_startup(void)
> {
> + phys_addr_t luo_ser_phys;
> struct luo_ser *luo_ser;
> - int err, header_size;
> - phys_addr_t fdt_phys;
> - const void *ptr;
> - u64 luo_ser_pa;
> + size_t len;
> + int err;
>
> if (!kho_is_enabled()) {
> if (liveupdate_enabled())
> @@ -94,40 +91,29 @@ static int __init luo_early_startup(void)
> return 0;
> }
>
> - /* Retrieve LUO subtree, and verify its format. */
> - err = kho_retrieve_subtree(LUO_FDT_KHO_ENTRY_NAME, &fdt_phys, NULL);
> + /* Retrieve LUO state from KHO. */
> + err = kho_retrieve_subtree(LUO_KHO_ENTRY_NAME, &luo_ser_phys, &len);
> if (err) {
> if (err != -ENOENT) {
> - pr_err("failed to retrieve FDT '%s' from KHO: %pe\n",
> - LUO_FDT_KHO_ENTRY_NAME, ERR_PTR(err));
> + pr_err("failed to retrieve LUO state '%s' from KHO: %pe\n",
> + LUO_KHO_ENTRY_NAME, ERR_PTR(err));
> return err;
> }
>
> return 0;
> }
>
> - luo_global.fdt_in = phys_to_virt(fdt_phys);
> - err = fdt_node_check_compatible(luo_global.fdt_in, 0,
> - LUO_FDT_COMPATIBLE);
> - if (err) {
> - pr_err("FDT '%s' is incompatible with '%s' [%d]\n",
> - LUO_FDT_KHO_ENTRY_NAME, LUO_FDT_COMPATIBLE, err);
> -
> + if (len < sizeof(*luo_ser)) {
> + pr_err("LUO state is too small (%zu < %zu)\n", len, sizeof(*luo_ser));
> return -EINVAL;
> }
>
> - header_size = 0;
> - ptr = fdt_getprop(luo_global.fdt_in, 0, LUO_FDT_ABI_HEADER, &header_size);
> - if (!ptr || header_size != sizeof(u64)) {
> - pr_err("Unable to get ABI header '%s' [%d]\n",
> - LUO_FDT_ABI_HEADER, header_size);
> -
> + luo_ser = phys_to_virt(luo_ser_phys);
> + if (strncmp(luo_ser->compatible, LUO_ABI_COMPATIBLE, LUO_ABI_COMPAT_LEN)) {
> + pr_err("LUO state is incompatible with '%s'\n", LUO_ABI_COMPATIBLE);
> return -EINVAL;
> }
>
> - luo_ser_pa = get_unaligned((u64 *)ptr);
> - luo_ser = phys_to_virt(luo_ser_pa);
> -
> luo_global.liveupdate_num = luo_ser->liveupdate_num;
> pr_info("Retrieved live update data, liveupdate number: %lld\n",
> luo_global.liveupdate_num);
> @@ -160,37 +146,20 @@ static int __init liveupdate_early_init(void)
> }
> early_initcall(liveupdate_early_init);
>
> -/* Called during boot to create outgoing LUO fdt tree */
> -static int __init luo_fdt_setup(void)
> +/* Called during boot to create outgoing LUO state */
> +static int __init luo_state_setup(void)
> {
> struct luo_ser *luo_ser;
> - u64 luo_ser_pa;
> - void *fdt_out;
> int err;
>
> - fdt_out = kho_alloc_preserve(LUO_FDT_SIZE);
> - if (IS_ERR(fdt_out)) {
> - pr_err("failed to allocate/preserve FDT memory\n");
> - return PTR_ERR(fdt_out);
> - }
> -
> luo_ser = kho_alloc_preserve(sizeof(*luo_ser));
> if (IS_ERR(luo_ser)) {
> - err = PTR_ERR(luo_ser);
> - goto exit_free_fdt;
> + pr_err("failed to allocate/preserve LUO state memory\n");
> + return PTR_ERR(luo_ser);
> }
> - luo_ser_pa = virt_to_phys(luo_ser);
> -
> - err = fdt_create(fdt_out, LUO_FDT_SIZE);
> - err |= fdt_finish_reservemap(fdt_out);
> - err |= fdt_begin_node(fdt_out, "");
> - err |= fdt_property_string(fdt_out, "compatible", LUO_FDT_COMPATIBLE);
> - err |= fdt_property(fdt_out, LUO_FDT_ABI_HEADER, &luo_ser_pa,
> - sizeof(luo_ser_pa));
> - err |= fdt_end_node(fdt_out);
> - err |= fdt_finish(fdt_out);
> - if (err)
> - goto exit_free_luo_ser;
> +
> + strscpy(luo_ser->compatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser->compatible));
> + luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
>
> err = luo_session_setup_outgoing(&luo_ser->sessions_pa);
> if (err)
> @@ -200,21 +169,17 @@ static int __init luo_fdt_setup(void)
> if (err)
> goto exit_free_luo_ser;
>
> - luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
> -
> - err = kho_add_subtree(LUO_FDT_KHO_ENTRY_NAME, fdt_out,
> - fdt_totalsize(fdt_out));
> + err = kho_add_subtree(LUO_KHO_ENTRY_NAME, luo_ser, sizeof(*luo_ser));
> if (err)
> goto exit_free_luo_ser;
> - luo_global.fdt_out = fdt_out;
> +
> + luo_global.luo_ser_out = luo_ser;
>
> return 0;
>
> exit_free_luo_ser:
> kho_unpreserve_free(luo_ser);
> -exit_free_fdt:
> - kho_unpreserve_free(fdt_out);
> - pr_err("failed to prepare LUO FDT: %d\n", err);
> + pr_err("failed to prepare LUO state: %d\n", err);
>
> return err;
> }
> @@ -230,7 +195,7 @@ static int __init luo_late_startup(void)
> if (!liveupdate_enabled())
> return 0;
>
> - err = luo_fdt_setup();
> + err = luo_state_setup();
> if (err)
> luo_global.enabled = false;
>
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 27+ messages in thread* Re: [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
2026-06-03 6:50 ` Mike Rapoport
@ 2026-06-03 9:32 ` Mike Rapoport
0 siblings, 0 replies; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 9:32 UTC (permalink / raw)
To: Pasha Tatashin
Cc: linux-kselftest, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, dmatlack, kexec, pratyush, skhawaja, graf
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.
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree
2026-06-03 3:28 ` [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree Pasha Tatashin
2026-06-03 6:50 ` Mike Rapoport
@ 2026-06-03 13:31 ` Mike Rapoport
1 sibling, 0 replies; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 13:31 UTC (permalink / raw)
To: Pasha Tatashin
Cc: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, dmatlack, kexec, pratyush, skhawaja, graf
On Wed, 03 Jun 2026 03:28:55 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> 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) <rppt@kernel.org>
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 27+ messages in thread
* [PATCH v6 05/13] liveupdate: Extract luo_file_deserialize_one helper
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (3 preceding siblings ...)
2026-06-03 3:28 ` [PATCH v6 04/13] liveupdate: register luo_ser as KHO subtree Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 3:28 ` [PATCH v6 06/13] liveupdate: Extract luo_session_deserialize_one helper Pasha Tatashin
` (7 subsequent siblings)
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
Extract the logic for deserializing single entries for files into
separate helper functions. In preparation to a linked-block
serialization for files.
This is a pure code movement, no other changes intended.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_file.c | 77 ++++++++++++++++++++----------------
1 file changed, 44 insertions(+), 33 deletions(-)
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index 208987502f73..9eec07a9e9fc 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -753,6 +753,46 @@ int luo_file_finish(struct luo_file_set *file_set)
return 0;
}
+static int luo_file_deserialize_one(struct luo_file_set *file_set,
+ struct luo_file_ser *ser)
+{
+ struct liveupdate_file_handler *fh;
+ bool handler_found = false;
+ struct luo_file *luo_file;
+
+ down_read(&luo_register_rwlock);
+ list_private_for_each_entry(fh, &luo_file_handler_list, list) {
+ if (!strcmp(fh->compatible, ser->compatible)) {
+ if (try_module_get(fh->ops->owner))
+ handler_found = true;
+ break;
+ }
+ }
+ up_read(&luo_register_rwlock);
+
+ if (!handler_found) {
+ pr_warn("No registered handler for compatible '%.*s'\n",
+ (int)sizeof(ser->compatible),
+ ser->compatible);
+ return -ENOENT;
+ }
+
+ luo_file = kzalloc_obj(*luo_file);
+ if (!luo_file) {
+ module_put(fh->ops->owner);
+ return -ENOMEM;
+ }
+
+ luo_file->fh = fh;
+ luo_file->file = NULL;
+ luo_file->serialized_data = ser->data;
+ luo_file->token = ser->token;
+ mutex_init(&luo_file->mutex);
+ list_add_tail(&luo_file->list, &file_set->files_list);
+
+ return 0;
+}
+
/**
* luo_file_deserialize - Reconstructs the list of preserved files in the new kernel.
* @file_set: The incoming file_set to fill with deserialized data.
@@ -782,6 +822,7 @@ int luo_file_deserialize(struct luo_file_set *file_set,
struct luo_file_set_ser *file_set_ser)
{
struct luo_file_ser *file_ser;
+ int err;
u64 i;
if (!file_set_ser->files) {
@@ -809,39 +850,9 @@ int luo_file_deserialize(struct luo_file_set *file_set,
*/
file_ser = file_set->files;
for (i = 0; i < file_set->count; i++) {
- struct liveupdate_file_handler *fh;
- bool handler_found = false;
- struct luo_file *luo_file;
-
- down_read(&luo_register_rwlock);
- list_private_for_each_entry(fh, &luo_file_handler_list, list) {
- if (!strcmp(fh->compatible, file_ser[i].compatible)) {
- if (try_module_get(fh->ops->owner))
- handler_found = true;
- break;
- }
- }
- up_read(&luo_register_rwlock);
-
- if (!handler_found) {
- pr_warn("No registered handler for compatible '%.*s'\n",
- (int)sizeof(file_ser[i].compatible),
- file_ser[i].compatible);
- return -ENOENT;
- }
-
- luo_file = kzalloc_obj(*luo_file);
- if (!luo_file) {
- module_put(fh->ops->owner);
- return -ENOMEM;
- }
-
- luo_file->fh = fh;
- luo_file->file = NULL;
- luo_file->serialized_data = file_ser[i].data;
- luo_file->token = file_ser[i].token;
- mutex_init(&luo_file->mutex);
- list_add_tail(&luo_file->list, &file_set->files_list);
+ err = luo_file_deserialize_one(file_set, &file_ser[i]);
+ if (err)
+ return err;
}
return 0;
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 06/13] liveupdate: Extract luo_session_deserialize_one helper
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (4 preceding siblings ...)
2026-06-03 3:28 ` [PATCH v6 05/13] liveupdate: Extract luo_file_deserialize_one helper Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 3:28 ` [PATCH v6 07/13] kho: add support for linked-block serialization Pasha Tatashin
` (6 subsequent siblings)
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
Extract the logic for deserializing single entries for sessions into
separate helper functions. In preparation to a linked-block
serialization for sessions.
This is a pure code movement, no other changes intended.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_session.c | 63 +++++++++++++++++++--------------
1 file changed, 36 insertions(+), 27 deletions(-)
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 85782c6f3d6c..1cd315e0f6de 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -555,6 +555,40 @@ int __init luo_session_setup_incoming(u64 sessions_pa)
return 0;
}
+static int luo_session_deserialize_one(struct luo_session_header *sh,
+ struct luo_session_ser *ser)
+{
+ struct luo_session *session;
+ int err;
+
+ session = luo_session_alloc(ser->name);
+ if (IS_ERR(session)) {
+ pr_warn("Failed to allocate session [%.*s] during deserialization %pe\n",
+ (int)sizeof(ser->name), ser->name, session);
+ return PTR_ERR(session);
+ }
+
+ err = luo_session_insert(sh, session);
+ if (err) {
+ pr_warn("Failed to insert session [%s] %pe\n",
+ session->name, ERR_PTR(err));
+ luo_session_free(session);
+ return err;
+ }
+
+ scoped_guard(mutex, &session->mutex) {
+ err = luo_file_deserialize(&session->file_set,
+ &ser->file_set_ser);
+ }
+ if (err) {
+ pr_warn("Failed to deserialize files for session [%s] %pe\n",
+ session->name, ERR_PTR(err));
+ return err;
+ }
+
+ return 0;
+}
+
int luo_session_deserialize(void)
{
struct luo_session_header *sh = &luo_session_global.incoming;
@@ -586,34 +620,9 @@ int luo_session_deserialize(void)
* reliably reset devices and reclaim memory.
*/
for (int i = 0; i < sh->header_ser->count; i++) {
- struct luo_session *session;
-
- session = luo_session_alloc(sh->ser[i].name);
- if (IS_ERR(session)) {
- pr_warn("Failed to allocate session [%.*s] during deserialization %pe\n",
- (int)sizeof(sh->ser[i].name),
- sh->ser[i].name, session);
- err = PTR_ERR(session);
- goto save_err;
- }
-
- err = luo_session_insert(sh, session);
- if (err) {
- pr_warn("Failed to insert session [%s] %pe\n",
- session->name, ERR_PTR(err));
- luo_session_free(session);
- goto save_err;
- }
-
- scoped_guard(mutex, &session->mutex) {
- err = luo_file_deserialize(&session->file_set,
- &sh->ser[i].file_set_ser);
- }
- if (err) {
- pr_warn("Failed to deserialize files for session [%s] %pe\n",
- session->name, ERR_PTR(err));
+ err = luo_session_deserialize_one(sh, &sh->ser[i]);
+ if (err)
goto save_err;
- }
}
kho_restore_free(sh->header_ser);
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (5 preceding siblings ...)
2026-06-03 3:28 ` [PATCH v6 06/13] liveupdate: Extract luo_session_deserialize_one helper Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 6:49 ` Mike Rapoport
2026-06-03 3:28 ` [PATCH v6 08/13] liveupdate: defer session block allocation and physical address setting Pasha Tatashin
` (5 subsequent siblings)
12 siblings, 1 reply; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
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 <pasha.tatashin@soleen.com>
---
Documentation/core-api/kho/abi.rst | 5 +
Documentation/core-api/kho/index.rst | 11 +
MAINTAINERS | 1 +
include/linux/kho/abi/block.h | 56 ++++
include/linux/kho_block.h | 106 +++++++
kernel/liveupdate/Makefile | 1 +
kernel/liveupdate/kho_block.c | 411 +++++++++++++++++++++++++++
7 files changed, 591 insertions(+)
create mode 100644 include/linux/kho/abi/block.h
create mode 100644 include/linux/kho_block.h
create mode 100644 kernel/liveupdate/kho_block.c
diff --git a/Documentation/core-api/kho/abi.rst b/Documentation/core-api/kho/abi.rst
index 799d743105a6..edeb5b311963 100644
--- a/Documentation/core-api/kho/abi.rst
+++ b/Documentation/core-api/kho/abi.rst
@@ -28,6 +28,11 @@ KHO persistent memory tracker ABI
.. kernel-doc:: include/linux/kho/abi/kexec_handover.h
:doc: KHO persistent memory tracker
+KHO serialization block ABI
+===========================
+
+.. kernel-doc:: include/linux/kho/abi/block.h
+
See Also
========
diff --git a/Documentation/core-api/kho/index.rst b/Documentation/core-api/kho/index.rst
index 0a2dee4f8e7d..320914a42178 100644
--- a/Documentation/core-api/kho/index.rst
+++ b/Documentation/core-api/kho/index.rst
@@ -83,6 +83,17 @@ Public API
.. kernel-doc:: kernel/liveupdate/kexec_handover.c
:export:
+KHO Serialization Blocks API
+============================
+
+.. kernel-doc:: kernel/liveupdate/kho_block.c
+ :doc: KHO Serialization Blocks
+
+.. kernel-doc:: include/linux/kho_block.h
+
+.. kernel-doc:: kernel/liveupdate/kho_block.c
+ :internal:
+
See Also
========
diff --git a/MAINTAINERS b/MAINTAINERS
index 9ec290e38b44..920ba7622afa 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14208,6 +14208,7 @@ F: Documentation/admin-guide/mm/kho.rst
F: Documentation/core-api/kho/*
F: include/linux/kexec_handover.h
F: include/linux/kho/
+F: include/linux/kho_block.h
F: kernel/liveupdate/kexec_handover*
F: lib/test_kho.c
F: tools/testing/selftests/kho/
diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
new file mode 100644
index 000000000000..8641c20b379b
--- /dev/null
+++ b/include/linux/kho/abi/block.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2026, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+/**
+ * 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_BLOCK_ABI_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 <asm/page.h>
+#include <linux/types.h>
+
+#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
+
+/**
+ * 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_block.h b/include/linux/kho_block.h
new file mode 100644
index 000000000000..93a7cc2be5f5
--- /dev/null
+++ b/include/linux/kho_block.h
@@ -0,0 +1,106 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2026, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#ifndef _LINUX_KHO_BLOCK_H
+#define _LINUX_KHO_BLOCK_H
+
+#include <linux/list.h>
+#include <linux/types.h>
+#include <linux/kho/abi/block.h>
+
+/**
+ * struct kho_block - Internal representation of a serialization block.
+ * @list: List head for linking blocks in memory.
+ * @ser: Pointer to the serialized header in preserved memory.
+ */
+struct kho_block {
+ struct list_head list;
+ struct kho_block_header_ser *ser;
+};
+
+/**
+ * struct kho_block_set - A set of blocks containing serialized entries of the same type.
+ * @blocks: The list of serialization blocks (struct kho_block).
+ * @nblocks: The number of allocated serialization blocks.
+ * @head_pa: Physical address of the first block header.
+ * @entry_size: The size of each entry in the blocks.
+ * @count_per_block: The maximum number of entries each block can hold.
+ * @incoming: True if this block set was restored from the previous kernel.
+ *
+ * Note: Synchronization and locking are the responsibility of the caller.
+ * The block set structure itself is not internally synchronized.
+ */
+struct kho_block_set {
+ struct list_head blocks;
+ long nblocks;
+ u64 head_pa;
+ size_t entry_size;
+ u64 count_per_block;
+ bool incoming;
+};
+
+/**
+ * struct kho_block_set_it - Iterator for serializing entries into blocks.
+ * @bs: The block set being iterated.
+ * @block: The current block.
+ * @i: The current entry index within @block.
+ */
+struct kho_block_set_it {
+ struct kho_block_set *bs;
+ struct kho_block *block;
+ u64 i;
+};
+
+/**
+ * KHO_BLOCK_SET_INIT - Initialize a static kho_block_set.
+ * @_name: Name of the kho_block_set variable.
+ * @_entry_size: The size of each entry in the block set.
+ */
+#define KHO_BLOCK_SET_INIT(_name, _entry_size) { \
+ .blocks = LIST_HEAD_INIT((_name).blocks), \
+ .entry_size = _entry_size, \
+ .count_per_block = (KHO_BLOCK_SIZE - \
+ sizeof(struct kho_block_header_ser)) / \
+ (_entry_size), \
+}
+
+void kho_block_set_init(struct kho_block_set *bs, size_t entry_size);
+
+int kho_block_set_grow(struct kho_block_set *bs, u64 count);
+void kho_block_set_shrink(struct kho_block_set *bs, u64 count);
+
+int kho_block_set_restore(struct kho_block_set *bs, u64 head_pa);
+void kho_block_set_destroy(struct kho_block_set *bs);
+void kho_block_set_clear(struct kho_block_set *bs);
+
+/**
+ * kho_block_set_head_pa - Get the physical address of the first block header.
+ * @bs: The block set.
+ *
+ * Return: The physical address of the first block header, or 0 if empty.
+ */
+static inline u64 kho_block_set_head_pa(struct kho_block_set *bs)
+{
+ return bs->head_pa;
+}
+
+/**
+ * kho_block_set_is_empty - Check if the block set has no allocated blocks.
+ * @bs: The block set.
+ *
+ * Return: True if there are no blocks in the set, false otherwise.
+ */
+static inline bool kho_block_set_is_empty(struct kho_block_set *bs)
+{
+ return list_empty(&bs->blocks);
+}
+
+void kho_block_set_it_init(struct kho_block_set_it *it, struct kho_block_set *bs);
+void *kho_block_set_it_reserve_entry(struct kho_block_set_it *it);
+void *kho_block_set_it_read_entry(struct kho_block_set_it *it);
+void *kho_block_set_it_prev(struct kho_block_set_it *it);
+
+#endif /* _LINUX_KHO_BLOCK_H */
diff --git a/kernel/liveupdate/Makefile b/kernel/liveupdate/Makefile
index d2f779cbe279..eec9d3ae07eb 100644
--- a/kernel/liveupdate/Makefile
+++ b/kernel/liveupdate/Makefile
@@ -1,6 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
luo-y := \
+ kho_block.o \
luo_core.o \
luo_file.o \
luo_flb.o \
diff --git a/kernel/liveupdate/kho_block.c b/kernel/liveupdate/kho_block.c
new file mode 100644
index 000000000000..4f147c308e6b
--- /dev/null
+++ b/kernel/liveupdate/kho_block.c
@@ -0,0 +1,411 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2026, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+/**
+ * DOC: KHO Serialization Blocks
+ *
+ * KHO provides a mechanism to preserve stateful data across a kexec handover
+ * by serializing it into memory blocks, and provides the common
+ * infrastructure for managing these blocks.
+ *
+ * Each block consists of a header (struct kho_block_header_ser) followed by an
+ * array of serialized entries. Multiple blocks are linked together via a
+ * physical pointer in the header, forming a linked list that can be easily
+ * traversed in both the current and the next kernel.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/io.h>
+#include <linux/kexec_handover.h>
+#include <linux/kho/abi/block.h>
+#include <linux/kho_block.h>
+#include <linux/slab.h>
+
+/*
+ * Safeguard limit for the number of serialization blocks. This is used to
+ * prevent infinite loops and excessive memory allocation in case of memory
+ * corruption in the preserved state.
+ *
+ * With a 4KB page size, 10k blocks is about 40MB. For 32-byte entries
+ * (e.g. 4 u64s), each block holds up to 127 entries (accounting for the
+ * 16-byte header), allowing the block set to hold up to 1.27M entries.
+ */
+#define KHO_MAX_BLOCKS 10000
+
+/**
+ * kho_block_set_init - Initialize a block set.
+ * @bs: The block set to initialize.
+ * @entry_size: The size of each entry in the blocks.
+ */
+void kho_block_set_init(struct kho_block_set *bs, size_t entry_size)
+{
+ *bs = (struct kho_block_set)KHO_BLOCK_SET_INIT(*bs, entry_size);
+ WARN_ON_ONCE(!bs->count_per_block);
+}
+
+/* Serialized entries start immediately after the block header */
+static void *kho_block_entries(struct kho_block *block)
+{
+ return (void *)(block->ser + 1);
+}
+
+/* Get the address of the serialized entry at the specified index */
+static void *kho_block_entry(struct kho_block_set_it *it, u64 index)
+{
+ return kho_block_entries(it->block) + (index * it->bs->entry_size);
+}
+
+/* Free serialized data */
+static void kho_block_free_ser(struct kho_block_set *bs,
+ struct kho_block_header_ser *ser)
+{
+ if (bs->incoming)
+ kho_restore_free(ser);
+ else
+ kho_unpreserve_free(ser);
+}
+
+static struct kho_block_header_ser *kho_block_alloc_ser(struct kho_block_set *bs)
+{
+ WARN_ON_ONCE(bs->incoming);
+ return kho_alloc_preserve(KHO_BLOCK_SIZE);
+}
+
+static int kho_block_add(struct kho_block_set *bs,
+ struct kho_block_header_ser *ser)
+{
+ struct kho_block *block, *last;
+
+ if (bs->nblocks >= KHO_MAX_BLOCKS)
+ return -ENOSPC;
+
+ block = kzalloc_obj(*block);
+ if (!block)
+ return -ENOMEM;
+
+ block->ser = ser;
+ last = list_last_entry_or_null(&bs->blocks, struct kho_block, list);
+ list_add_tail(&block->list, &bs->blocks);
+ bs->nblocks++;
+
+ if (last)
+ last->ser->next = virt_to_phys(ser);
+ else
+ bs->head_pa = virt_to_phys(ser);
+
+ return 0;
+}
+
+static int kho_block_set_grow_one(struct kho_block_set *bs)
+{
+ struct kho_block_header_ser *ser;
+ int err;
+
+ ser = kho_block_alloc_ser(bs);
+ if (IS_ERR(ser))
+ return PTR_ERR(ser);
+
+ err = kho_block_add(bs, ser);
+ if (err) {
+ kho_block_free_ser(bs, ser);
+ return err;
+ }
+
+ return 0;
+}
+
+/**
+ * kho_block_set_grow - Expand the block set to accommodate the target count.
+ * @bs: The block set.
+ * @count: The target number of valid entries to accommodate.
+ *
+ * Acts as a runtime notifier when new resources (such as files or sessions)
+ * are registered. Dynamically preallocates and links preserved memory blocks
+ * if the target entry count exceeds the current total capacity of the set,
+ * ensuring they are available during serialization/deserialization.
+ *
+ * Context: Caller must hold a lock protecting the block set.
+ * Return: 0 on success, or a negative errno on failure.
+ */
+int kho_block_set_grow(struct kho_block_set *bs, u64 count)
+{
+ if (WARN_ON_ONCE(bs->incoming))
+ return -EINVAL;
+
+ while (count > bs->nblocks * bs->count_per_block) {
+ int err = kho_block_set_grow_one(bs);
+
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
+static void kho_block_set_shrink_one(struct kho_block_set *bs)
+{
+ struct kho_block *last, *new_last;
+
+ if (list_empty(&bs->blocks))
+ return;
+
+ last = list_last_entry(&bs->blocks, struct kho_block, list);
+ list_del(&last->list);
+ bs->nblocks--;
+ kho_block_free_ser(bs, last->ser);
+ kfree(last);
+
+ new_last = list_last_entry_or_null(&bs->blocks, struct kho_block, list);
+ if (new_last)
+ new_last->ser->next = 0;
+ else
+ bs->head_pa = 0;
+}
+
+/**
+ * kho_block_set_shrink - Shrink the block set to accommodate the target count.
+ * @bs: The block set.
+ * @count: The target number of valid entries to accommodate.
+ *
+ * Acts as a runtime notifier when resources (such as files or sessions) are
+ * unregistered, allowing the block set to release and unallocate redundant
+ * preserved memory blocks. Checks if the last block in the set can be removed
+ * because the remaining entry count is fully accommodated by the preceding blocks.
+ *
+ * Note: It is the caller's responsibility to ensure that entries are removed
+ * in LIFO (last-in, first-out) order (the reverse order of their insertion).
+ * Because shrinking destroys the last block in the set, removing entries in
+ * any other order would corrupt active data.
+ *
+ * Context: Caller must hold a lock protecting the block set.
+ */
+void kho_block_set_shrink(struct kho_block_set *bs, u64 count)
+{
+ while (bs->nblocks > 0 && count <= (bs->nblocks - 1) * bs->count_per_block)
+ kho_block_set_shrink_one(bs);
+}
+
+/*
+ * kho_block_set_is_cyclic - Check for cycles in a linked list of blocks.
+ * Uses Floyd's cycle-finding algorithm to ensure sanity of the incoming list.
+ *
+ * Return: true if a cycle or corruption is detected, false otherwise.
+ */
+static bool kho_block_set_is_cyclic(struct kho_block_set *bs)
+{
+ struct kho_block_header_ser *fast;
+ struct kho_block_header_ser *slow;
+ int count = 0;
+
+ fast = phys_to_virt(bs->head_pa);
+ slow = fast;
+
+ while (fast) {
+ if (count++ >= KHO_MAX_BLOCKS) {
+ pr_err("Block set is corrupted\n");
+ return true;
+ }
+
+ if (!fast->next)
+ break;
+
+ fast = phys_to_virt(fast->next);
+ if (!fast->next)
+ break;
+
+ fast = phys_to_virt(fast->next);
+ slow = phys_to_virt(slow->next);
+
+ if (slow == fast) {
+ pr_err("Block set is corrupted\n");
+ return true;
+ }
+ }
+
+ return false;
+}
+
+/**
+ * kho_block_set_restore - Restore a block set from a physical address.
+ * @bs: The block set to restore.
+ * @head_pa: Physical address of the first block header.
+ *
+ * Restores a serialized block set from a given physical address. The caller is
+ * responsible for ensuring that the block set @bs has been allocated and
+ * initialized prior to calling this function.
+ *
+ * Return: 0 on success, or a negative errno on failure.
+ */
+int kho_block_set_restore(struct kho_block_set *bs, u64 head_pa)
+{
+ struct kho_block_header_ser *ser;
+ u64 next_pa = head_pa;
+ int err;
+
+ /* Restored block sets use size from the previous kernel */
+ bs->incoming = true;
+ if (!head_pa)
+ return 0;
+
+ bs->head_pa = head_pa;
+ if (kho_block_set_is_cyclic(bs)) {
+ bs->head_pa = 0;
+ return -EINVAL;
+ }
+
+ while (next_pa) {
+ ser = phys_to_virt(next_pa);
+ if (!ser->count || ser->count > bs->count_per_block) {
+ pr_warn("Block contains invalid entry count: %llu\n",
+ ser->count);
+ err = -EINVAL;
+ goto err_destroy;
+ }
+ err = kho_block_add(bs, ser);
+ if (err)
+ goto err_destroy;
+ next_pa = ser->next;
+ }
+
+ return 0;
+
+err_destroy:
+ kho_block_set_destroy(bs);
+
+ /* Free the remaining un-restored blocks in the physical chain */
+ while (next_pa) {
+ struct kho_block_header_ser *next_ser = phys_to_virt(next_pa);
+
+ next_pa = next_ser->next;
+ kho_block_free_ser(bs, next_ser);
+ }
+ return err;
+}
+
+/**
+ * kho_block_set_destroy - Destroy all blocks in a block set.
+ * @bs: The block set.
+ */
+void kho_block_set_destroy(struct kho_block_set *bs)
+{
+ struct kho_block *block, *tmp;
+
+ list_for_each_entry_safe(block, tmp, &bs->blocks, list) {
+ list_del(&block->list);
+ kho_block_free_ser(bs, block->ser);
+ kfree(block);
+ }
+ bs->nblocks = 0;
+ bs->head_pa = 0;
+}
+
+/**
+ * kho_block_set_clear - Clear all serialized data in a block set.
+ * @bs: The block set to clear.
+ */
+void kho_block_set_clear(struct kho_block_set *bs)
+{
+ struct kho_block *block;
+
+ list_for_each_entry(block, &bs->blocks, list) {
+ block->ser->count = 0;
+ memset(block->ser + 1, 0, KHO_BLOCK_SIZE - sizeof(*block->ser));
+ }
+}
+
+/**
+ * kho_block_set_it_init - Initialize a block set iterator.
+ * @it: The iterator to initialize.
+ * @bs: The block set to iterate over.
+ */
+void kho_block_set_it_init(struct kho_block_set_it *it, struct kho_block_set *bs)
+{
+ it->bs = bs;
+ it->block = list_first_entry_or_null(&bs->blocks, struct kho_block, list);
+ it->i = 0;
+}
+
+/**
+ * kho_block_set_it_reserve_entry - Reserve and return the next available slot for writing.
+ * @it: The block iterator.
+ *
+ * Reserves a slot in the current block during state serialization to add a new
+ * entry, advancing the internal index. If the current block is full, it
+ * automatically moves to the next block in the set.
+ *
+ * Return: A pointer to the reserved entry slot, or NULL if the block set's
+ * capacity is fully exhausted.
+ */
+void *kho_block_set_it_reserve_entry(struct kho_block_set_it *it)
+{
+ void *entry;
+
+ if (!it->block)
+ return NULL;
+
+ if (it->i == it->bs->count_per_block) {
+ if (list_is_last(&it->block->list, &it->bs->blocks))
+ return NULL;
+ it->block = list_next_entry(it->block, list);
+ it->i = 0;
+ }
+
+ entry = kho_block_entry(it, it->i++);
+ it->block->ser->count = it->i;
+ return entry;
+}
+
+/**
+ * kho_block_set_it_read_entry - Read the next serialized entry from the block set.
+ * @it: The block iterator.
+ *
+ * Iterates through previously written entries during state deserialization,
+ * respecting the actual count stored in each block's header.
+ *
+ * Return: A pointer to the next serialized entry, or NULL if all serialized
+ * entries have been read.
+ */
+void *kho_block_set_it_read_entry(struct kho_block_set_it *it)
+{
+ if (!it->block)
+ return NULL;
+
+ if (it->i == it->block->ser->count) {
+ if (list_is_last(&it->block->list, &it->bs->blocks))
+ return NULL;
+ it->block = list_next_entry(it->block, list);
+ it->i = 0;
+ }
+
+ return kho_block_entry(it, it->i++);
+}
+
+/**
+ * kho_block_set_it_prev - Return the previous entry slot in the block set.
+ * @it: The block iterator.
+ *
+ * If the current index is at the start of a block, it automatically moves to
+ * the end of the previous block.
+ *
+ * Return: A pointer to the previous entry slot, or NULL if at the very
+ * beginning of the block set.
+ */
+void *kho_block_set_it_prev(struct kho_block_set_it *it)
+{
+ if (!it->block)
+ return NULL;
+
+ if (it->i == 0) {
+ if (list_is_first(&it->block->list, &it->bs->blocks))
+ return NULL;
+ it->block = list_prev_entry(it->block, list);
+ it->i = it->bs->count_per_block;
+ }
+
+ return kho_block_entry(it, --it->i);
+}
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 3:28 ` [PATCH v6 07/13] kho: add support for linked-block serialization Pasha Tatashin
@ 2026-06-03 6:49 ` Mike Rapoport
2026-06-03 12:05 ` Pasha Tatashin
0 siblings, 1 reply; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 6:49 UTC (permalink / raw)
To: Pasha Tatashin
Cc: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, dmatlack, kexec, pratyush, skhawaja, graf
On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> new file mode 100644
> index 000000000000..8641c20b379b
> --- /dev/null
> +++ b/include/linux/kho/abi/block.h
> @@ -0,0 +1,56 @@
> [ ... skip 25 lines ... ]
> +#define _LINUX_KHO_ABI_BLOCK_H
> +
> +#include <asm/page.h>
> +#include <linux/types.h>
> +
> +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
It's never used by block set and after looking at the following patches I
found that it's appended to LUO compatible string.
While this works for LUO, I think it should be kho_block_set_restore()
responsibility to verify the compatibility.
>
> diff --git a/kernel/liveupdate/kho_block.c b/kernel/liveupdate/kho_block.c
> new file mode 100644
> index 000000000000..4f147c308e6b
> --- /dev/null
> +++ b/kernel/liveupdate/kho_block.c
> @@ -0,0 +1,411 @@
> [ ... skip 121 lines ... ]
> +/**
> + * kho_block_set_grow - Expand the block set to accommodate the target count.
> + * @bs: The block set.
> + * @count: The target number of valid entries to accommodate.
> + *
> + * Acts as a runtime notifier when new resources (such as files or sessions)
Not sure I understand what "runtime notifier" means in this context.
> [ ... skip 11 lines ... ]
> +
> + while (count > bs->nblocks * bs->count_per_block) {
> + int err = kho_block_set_grow_one(bs);
> +
> + if (err)
> + return err;
This leaks memory if more than one block is added.
> [ ... skip 31 lines ... ]
> + * unregistered, allowing the block set to release and unallocate redundant
> + * preserved memory blocks. Checks if the last block in the set can be removed
> + * because the remaining entry count is fully accommodated by the preceding blocks.
> + *
> + * Note: It is the caller's responsibility to ensure that entries are removed
> + * in LIFO (last-in, first-out) order (the reverse order of their insertion).
I think "in LIFO order" is sufficient :)
> [ ... skip 173 lines ... ]
> + it->i = 0;
> + }
> +
> + entry = kho_block_entry(it, it->i++);
> + it->block->ser->count = it->i;
> + return entry;
This looks way better than the previous version :)
Thanks!
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 27+ messages in thread* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 6:49 ` Mike Rapoport
@ 2026-06-03 12:05 ` Pasha Tatashin
2026-06-03 13:21 ` Pasha Tatashin
2026-06-03 13:59 ` Mike Rapoport
0 siblings, 2 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 12:05 UTC (permalink / raw)
To: Mike Rapoport
Cc: Pasha Tatashin, linux-kselftest, shuah, akpm, linux-mm, skhan,
linux-doc, linux-kernel, corbet, dmatlack, kexec, pratyush,
skhawaja, graf
On 06-03 09:49, Mike Rapoport wrote:
> On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > new file mode 100644
> > index 000000000000..8641c20b379b
> > --- /dev/null
> > +++ b/include/linux/kho/abi/block.h
> > @@ -0,0 +1,56 @@
> > [ ... skip 25 lines ... ]
> > +#define _LINUX_KHO_ABI_BLOCK_H
> > +
> > +#include <asm/page.h>
> > +#include <linux/types.h>
> > +
> > +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
>
> It's never used by block set and after looking at the following patches I
> found that it's appended to LUO compatible string.
>
> While this works for LUO, I think it should be kho_block_set_restore()
> responsibility to verify the compatibility.
It should work for any component that relies on kho_block. My proposal
is to use this method for other common KHO data structures (e.g., kho
vmalloc, kho radix, future kho xarray). There is no need for them to
carry the compatibility string in their metadata, as whoever uses them
will include their compatibility string.
For now, reviewers will have to make sure that if the ABI header content
is changed, the compatibility string is updated.
> > diff --git a/kernel/liveupdate/kho_block.c b/kernel/liveupdate/kho_block.c
> > new file mode 100644
> > index 000000000000..4f147c308e6b
> > --- /dev/null
> > +++ b/kernel/liveupdate/kho_block.c
> > @@ -0,0 +1,411 @@
> > [ ... skip 121 lines ... ]
> > +/**
> > + * kho_block_set_grow - Expand the block set to accommodate the target count.
> > + * @bs: The block set.
> > + * @count: The target number of valid entries to accommodate.
> > + *
> > + * Acts as a runtime notifier when new resources (such as files or sessions)
>
> Not sure I understand what "runtime notifier" means in this context.
It came from discussion with Pratyush, but I think we are on the same
page what they are, and I will just remove this.
>
> > [ ... skip 11 lines ... ]
> > +
> > + while (count > bs->nblocks * bs->count_per_block) {
> > + int err = kho_block_set_grow_one(bs);
> > +
> > + if (err)
> > + return err;
>
> This leaks memory if more than one block is added.
>
> > [ ... skip 31 lines ... ]
> > + * unregistered, allowing the block set to release and unallocate redundant
> > + * preserved memory blocks. Checks if the last block in the set can be removed
> > + * because the remaining entry count is fully accommodated by the preceding blocks.
> > + *
> > + * Note: It is the caller's responsibility to ensure that entries are removed
> > + * in LIFO (last-in, first-out) order (the reverse order of their insertion).
>
> I think "in LIFO order" is sufficient :)
Oh, I keep removing those :-)
> > [ ... skip 173 lines ... ]
> > + it->i = 0;
> > + }
> > +
> > + entry = kho_block_entry(it, it->i++);
> > + it->block->ser->count = it->i;
> > + return entry;
>
> This looks way better than the previous version :)
> Thanks!
Thank you. I will send a new version of this patch as a reply to this
email to avoid cluttering the mailing list.
Pasha
>
> --
> Sincerely yours,
> Mike.
>
^ permalink raw reply [flat|nested] 27+ messages in thread* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 12:05 ` Pasha Tatashin
@ 2026-06-03 13:21 ` Pasha Tatashin
2026-06-03 13:59 ` Mike Rapoport
1 sibling, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 13:21 UTC (permalink / raw)
To: Mike Rapoport
Cc: Pasha Tatashin, linux-kselftest, shuah, akpm, linux-mm, skhan,
linux-doc, linux-kernel, corbet, dmatlack, kexec, pratyush,
skhawaja, graf
On 06-03 12:05, Pasha Tatashin wrote:
> On 06-03 09:49, Mike Rapoport wrote:
> > On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > > new file mode 100644
> > > index 000000000000..8641c20b379b
> > > --- /dev/null
> > > +++ b/include/linux/kho/abi/block.h
> > > @@ -0,0 +1,56 @@
> > > [ ... skip 25 lines ... ]
> > > +#define _LINUX_KHO_ABI_BLOCK_H
> > > +
> > > +#include <asm/page.h>
> > > +#include <linux/types.h>
> > > +
> > > +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
> >
> > It's never used by block set and after looking at the following patches I
> > found that it's appended to LUO compatible string.
> >
> > While this works for LUO, I think it should be kho_block_set_restore()
> > responsibility to verify the compatibility.
>
> It should work for any component that relies on kho_block. My proposal
> is to use this method for other common KHO data structures (e.g., kho
> vmalloc, kho radix, future kho xarray). There is no need for them to
> carry the compatibility string in their metadata, as whoever uses them
> will include their compatibility string.
>
> For now, reviewers will have to make sure that if the ABI header content
> is changed, the compatibility string is updated.
>
> > > diff --git a/kernel/liveupdate/kho_block.c b/kernel/liveupdate/kho_block.c
> > > new file mode 100644
> > > index 000000000000..4f147c308e6b
> > > --- /dev/null
> > > +++ b/kernel/liveupdate/kho_block.c
> > > @@ -0,0 +1,411 @@
> > > [ ... skip 121 lines ... ]
> > > +/**
> > > + * kho_block_set_grow - Expand the block set to accommodate the target count.
> > > + * @bs: The block set.
> > > + * @count: The target number of valid entries to accommodate.
> > > + *
> > > + * Acts as a runtime notifier when new resources (such as files or sessions)
> >
> > Not sure I understand what "runtime notifier" means in this context.
>
> It came from discussion with Pratyush, but I think we are on the same
> page what they are, and I will just remove this.
>
> >
> > > [ ... skip 11 lines ... ]
> > > +
> > > + while (count > bs->nblocks * bs->count_per_block) {
> > > + int err = kho_block_set_grow_one(bs);
> > > +
> > > + if (err)
> > > + return err;
> >
> > This leaks memory if more than one block is added.
> >
> > > [ ... skip 31 lines ... ]
> > > + * unregistered, allowing the block set to release and unallocate redundant
> > > + * preserved memory blocks. Checks if the last block in the set can be removed
> > > + * because the remaining entry count is fully accommodated by the preceding blocks.
> > > + *
> > > + * Note: It is the caller's responsibility to ensure that entries are removed
> > > + * in LIFO (last-in, first-out) order (the reverse order of their insertion).
> >
> > I think "in LIFO order" is sufficient :)
>
> Oh, I keep removing those :-)
>
> > > [ ... skip 173 lines ... ]
> > > + it->i = 0;
> > > + }
> > > +
> > > + entry = kho_block_entry(it, it->i++);
> > > + it->block->ser->count = it->i;
> > > + return entry;
> >
> > This looks way better than the previous version :)
> > Thanks!
>
> Thank you. I will send a new version of this patch as a reply to this
> email to avoid cluttering the mailing list.
The patch is here:
https://lore.kernel.org/all/20260603130612.397948-1-pasha.tatashin@soleen.com/
I messed up in-reply-to field with wrong message-id.
Pasha
>
> Pasha
>
> >
> > --
> > Sincerely yours,
> > Mike.
> >
^ permalink raw reply [flat|nested] 27+ messages in thread* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 12:05 ` Pasha Tatashin
2026-06-03 13:21 ` Pasha Tatashin
@ 2026-06-03 13:59 ` Mike Rapoport
2026-06-03 14:11 ` Pasha Tatashin
1 sibling, 1 reply; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 13:59 UTC (permalink / raw)
To: Pasha Tatashin
Cc: linux-kselftest, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, dmatlack, kexec, pratyush, skhawaja, graf
On Wed, Jun 03, 2026 at 12:05:04PM +0000, Pasha Tatashin wrote:
> On 06-03 09:49, Mike Rapoport wrote:
> > On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > > new file mode 100644
> > > index 000000000000..8641c20b379b
> > > --- /dev/null
> > > +++ b/include/linux/kho/abi/block.h
> > > @@ -0,0 +1,56 @@
> > > [ ... skip 25 lines ... ]
> > > +#define _LINUX_KHO_ABI_BLOCK_H
> > > +
> > > +#include <asm/page.h>
> > > +#include <linux/types.h>
> > > +
> > > +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
> >
> > It's never used by block set and after looking at the following patches I
> > found that it's appended to LUO compatible string.
> >
> > While this works for LUO, I think it should be kho_block_set_restore()
> > responsibility to verify the compatibility.
>
> It should work for any component that relies on kho_block. My proposal
> is to use this method for other common KHO data structures (e.g., kho
> vmalloc, kho radix, future kho xarray). There is no need for them to
> carry the compatibility string in their metadata, as whoever uses them
> will include their compatibility string.
So if, say, memfd_luo uses kho vmalloc, xarray and blocks it'll have five
compatibility strings glued together?
> For now, reviewers will have to make sure that if the ABI header content
> is changed, the compatibility string is updated.
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 13:59 ` Mike Rapoport
@ 2026-06-03 14:11 ` Pasha Tatashin
2026-06-03 14:34 ` Mike Rapoport
0 siblings, 1 reply; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 14:11 UTC (permalink / raw)
To: Mike Rapoport
Cc: Pasha Tatashin, linux-kselftest, shuah, akpm, linux-mm, skhan,
linux-doc, linux-kernel, corbet, dmatlack, kexec, pratyush,
skhawaja, graf
On 06-03 16:59, Mike Rapoport wrote:
> On Wed, Jun 03, 2026 at 12:05:04PM +0000, Pasha Tatashin wrote:
> > On 06-03 09:49, Mike Rapoport wrote:
> > > On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > > > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > > > new file mode 100644
> > > > index 000000000000..8641c20b379b
> > > > --- /dev/null
> > > > +++ b/include/linux/kho/abi/block.h
> > > > @@ -0,0 +1,56 @@
> > > > [ ... skip 25 lines ... ]
> > > > +#define _LINUX_KHO_ABI_BLOCK_H
> > > > +
> > > > +#include <asm/page.h>
> > > > +#include <linux/types.h>
> > > > +
> > > > +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
> > >
> > > It's never used by block set and after looking at the following patches I
> > > found that it's appended to LUO compatible string.
> > >
> > > While this works for LUO, I think it should be kho_block_set_restore()
> > > responsibility to verify the compatibility.
> >
> > It should work for any component that relies on kho_block. My proposal
> > is to use this method for other common KHO data structures (e.g., kho
> > vmalloc, kho radix, future kho xarray). There is no need for them to
> > carry the compatibility string in their metadata, as whoever uses them
> > will include their compatibility string.
>
> So if, say, memfd_luo uses kho vmalloc, xarray and blocks it'll have five
> compatibility strings glued together?
That is correct, but it will be in only one place: the header of the
client's KHO subtree. Since it is dynamically sized and 8-byte aligned,
it should be safe to include in any struct.
Pasha
>
> > For now, reviewers will have to make sure that if the ABI header content
> > is changed, the compatibility string is updated.
>
> --
> Sincerely yours,
> Mike.
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 14:11 ` Pasha Tatashin
@ 2026-06-03 14:34 ` Mike Rapoport
2026-06-03 15:03 ` Pasha Tatashin
0 siblings, 1 reply; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 14:34 UTC (permalink / raw)
To: Pasha Tatashin
Cc: Mike Rapoport, linux-kselftest, shuah, akpm, linux-mm, skhan,
linux-doc, linux-kernel, corbet, dmatlack, kexec, pratyush,
skhawaja, graf
On 2026-06-03 14:11 +0000, Pasha Tatashin wrote:
> On 06-03 16:59, Mike Rapoport wrote:
> > On Wed, Jun 03, 2026 at 12:05:04PM +0000, Pasha Tatashin wrote:
> > > On 06-03 09:49, Mike Rapoport wrote:
> > > > On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > > > > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > > > > new file mode 100644
> > > > > index 000000000000..8641c20b379b
> > > > > --- /dev/null
> > > > > +++ b/include/linux/kho/abi/block.h
> > > > > @@ -0,0 +1,56 @@
> > > > > [ ... skip 25 lines ... ]
> > > > > +#define _LINUX_KHO_ABI_BLOCK_H
> > > > > +
> > > > > +#include <asm/page.h>
> > > > > +#include <linux/types.h>
> > > > > +
> > > > > +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
> > > >
> > > > It's never used by block set and after looking at the following patches I
> > > > found that it's appended to LUO compatible string.
> > > >
> > > > While this works for LUO, I think it should be kho_block_set_restore()
> > > > responsibility to verify the compatibility.
> > >
> > > It should work for any component that relies on kho_block. My proposal
> > > is to use this method for other common KHO data structures (e.g., kho
> > > vmalloc, kho radix, future kho xarray). There is no need for them to
> > > carry the compatibility string in their metadata, as whoever uses them
> > > will include their compatibility string.
> >
> > So if, say, memfd_luo uses kho vmalloc, xarray and blocks it'll have five
> > compatibility strings glued together?
>
> That is correct, but it will be in only one place: the header of the
> client's KHO subtree. Since it is dynamically sized and 8-byte aligned,
> it should be safe to include in any struct.
This is safe, you are right.
But I have more usability concerns from one side and the duplication it
causes from the other.
I can see the downside of putting the version information in the data
structure itself as it either requires a different header for the first
element or needlessly increases all the headers.
But
#define LUO_ABI_COMPATIBLE LUO_COMPAT_BASE "-" KHO_BLOCK_ABI_COMPATIBLE "-" KHO_VMALLOC_ABI_COMPATIBLE "-" KHO_RADIX_COMPATIBLE
is not really digestible too. And it forces KHO users to potentially
track KHO internal changes.
We still don't promise any compatibility between different kernel
versions so to avoid blocking this series on the decision what is the
best way to convey KHO data structures compatibility I suggest to bump
kho ABI version in v6.2* of the patch that adds KHO blocks and postpone
this discussion to after rc1 when we'll have plenty of time.
* sending a new version of a single file does same email traffic, but it
confuses b4 and quite possibly other tools, so I think v7 is better.
> Pasha
>
> >
> > > For now, reviewers will have to make sure that if the ABI header content
> > > is changed, the compatibility string is updated.
> >
> --
> > Sincerely yours,
> > Mike.
>
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 14:34 ` Mike Rapoport
@ 2026-06-03 15:03 ` Pasha Tatashin
2026-06-03 15:18 ` Mike Rapoport
0 siblings, 1 reply; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 15:03 UTC (permalink / raw)
To: Mike Rapoport
Cc: Pasha Tatashin, linux-kselftest, shuah, akpm, linux-mm, skhan,
linux-doc, linux-kernel, corbet, dmatlack, kexec, pratyush,
skhawaja, graf
On 06-03 17:34, Mike Rapoport wrote:
> On 2026-06-03 14:11 +0000, Pasha Tatashin wrote:
> > On 06-03 16:59, Mike Rapoport wrote:
> > > On Wed, Jun 03, 2026 at 12:05:04PM +0000, Pasha Tatashin wrote:
> > > > On 06-03 09:49, Mike Rapoport wrote:
> > > > > On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > > > > > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > > > > > new file mode 100644
> > > > > > index 000000000000..8641c20b379b
> > > > > > --- /dev/null
> > > > > > +++ b/include/linux/kho/abi/block.h
> > > > > > @@ -0,0 +1,56 @@
> > > > > > [ ... skip 25 lines ... ]
> > > > > > +#define _LINUX_KHO_ABI_BLOCK_H
> > > > > > +
> > > > > > +#include <asm/page.h>
> > > > > > +#include <linux/types.h>
> > > > > > +
> > > > > > +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
> > > > >
> > > > > It's never used by block set and after looking at the following patches I
> > > > > found that it's appended to LUO compatible string.
> > > > >
> > > > > While this works for LUO, I think it should be kho_block_set_restore()
> > > > > responsibility to verify the compatibility.
> > > >
> > > > It should work for any component that relies on kho_block. My proposal
> > > > is to use this method for other common KHO data structures (e.g., kho
> > > > vmalloc, kho radix, future kho xarray). There is no need for them to
> > > > carry the compatibility string in their metadata, as whoever uses them
> > > > will include their compatibility string.
> > >
> > > So if, say, memfd_luo uses kho vmalloc, xarray and blocks it'll have five
> > > compatibility strings glued together?
> >
> > That is correct, but it will be in only one place: the header of the
> > client's KHO subtree. Since it is dynamically sized and 8-byte aligned,
> > it should be safe to include in any struct.
>
> This is safe, you are right.
> But I have more usability concerns from one side and the duplication it
> causes from the other.
>
> I can see the downside of putting the version information in the data
> structure itself as it either requires a different header for the first
> element or needlessly increases all the headers.
>
> But
>
> #define LUO_ABI_COMPATIBLE LUO_COMPAT_BASE "-" KHO_BLOCK_ABI_COMPATIBLE "-" KHO_VMALLOC_ABI_COMPATIBLE "-" KHO_RADIX_COMPATIBLE
>
> is not really digestible too. And it forces KHO users to potentially
> track KHO internal changes.
These are compatibilities; I think they are quite digestible, both to
write and also when the LUO_ABI_COMPATIBLE string is printed out for
debugging/info purposes.
> We still don't promise any compatibility between different kernel
> versions so to avoid blocking this series on the decision what is the
> best way to convey KHO data structures compatibility I suggest to bump
> kho ABI version in v6.2* of the patch that adds KHO blocks and postpone
> this discussion to after rc1 when we'll have plenty of time.
Let's keep this patch as is for now. We will have a broader discussion
when we convert other participants to this new scheme. If we decide not
to pursue this approach, we will change this code to use an independent
compatibility string. However, having this in place as a template will
help us convert other components correctly, ensuring proper alignment
and that correct string helpers like strncmp / strscpy are used—which I
have already ensured is the case in LUO.
> * sending a new version of a single file does same email traffic, but it
> confuses b4 and quite possibly other tools, so I think v7 is better.
Agreed, I also prefer re-sending the whole series...
Pasha
> > Pasha
> >
> > >
> > > > For now, reviewers will have to make sure that if the ABI header content
> > > > is changed, the compatibility string is updated.
> > >
> > --
> > > Sincerely yours,
> > > Mike.
> >
>
>
^ permalink raw reply [flat|nested] 27+ messages in thread
* Re: [PATCH v6 07/13] kho: add support for linked-block serialization
2026-06-03 15:03 ` Pasha Tatashin
@ 2026-06-03 15:18 ` Mike Rapoport
0 siblings, 0 replies; 27+ messages in thread
From: Mike Rapoport @ 2026-06-03 15:18 UTC (permalink / raw)
To: Pasha Tatashin
Cc: Mike Rapoport, linux-kselftest, shuah, akpm, linux-mm, skhan,
linux-doc, linux-kernel, corbet, dmatlack, kexec, pratyush,
skhawaja, graf
On 2026-06-03 15:03 +0000, Pasha Tatashin wrote:
> On 06-03 17:34, Mike Rapoport wrote:
> > On 2026-06-03 14:11 +0000, Pasha Tatashin wrote:
> > > On 06-03 16:59, Mike Rapoport wrote:
> > > > On Wed, Jun 03, 2026 at 12:05:04PM +0000, Pasha Tatashin wrote:
> > > > > On 06-03 09:49, Mike Rapoport wrote:
> > > > > > On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > > > > > > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > > > > > > new file mode 100644
> > > > > > > index 000000000000..8641c20b379b
> > > > > > > --- /dev/null
> > > > > > > +++ b/include/linux/kho/abi/block.h
> > > > > > > @@ -0,0 +1,56 @@
> > > > > > > [ ... skip 25 lines ... ]
> > > > > > > +#define _LINUX_KHO_ABI_BLOCK_H
> > > > > > > +
> > > > > > > +#include <asm/page.h>
> > > > > > > +#include <linux/types.h>
> > > > > > > +
> > > > > > > +#define KHO_BLOCK_ABI_COMPATIBLE "kho-block-v1"
> > > > > >
> > > > > > It's never used by block set and after looking at the following patches I
> > > > > > found that it's appended to LUO compatible string.
> > > > > >
> > > > > > While this works for LUO, I think it should be kho_block_set_restore()
> > > > > > responsibility to verify the compatibility.
> > > > >
> > > > > It should work for any component that relies on kho_block. My proposal
> > > > > is to use this method for other common KHO data structures (e.g., kho
> > > > > vmalloc, kho radix, future kho xarray). There is no need for them to
> > > > > carry the compatibility string in their metadata, as whoever uses them
> > > > > will include their compatibility string.
> > > >
> > > > So if, say, memfd_luo uses kho vmalloc, xarray and blocks it'll have five
> > > > compatibility strings glued together?
> > >
> > > That is correct, but it will be in only one place: the header of the
> > > client's KHO subtree. Since it is dynamically sized and 8-byte aligned,
> > > it should be safe to include in any struct.
> >
> > This is safe, you are right.
> > But I have more usability concerns from one side and the duplication it
> > causes from the other.
> >
> > I can see the downside of putting the version information in the data
> > structure itself as it either requires a different header for the first
> > element or needlessly increases all the headers.
> >
> > But
> >
> > #define LUO_ABI_COMPATIBLE LUO_COMPAT_BASE "-" KHO_BLOCK_ABI_COMPATIBLE "-" KHO_VMALLOC_ABI_COMPATIBLE "-" KHO_RADIX_COMPATIBLE
> >
> > is not really digestible too. And it forces KHO users to potentially
> > track KHO internal changes.
>
> These are compatibilities; I think they are quite digestible, both to
> write and also when the LUO_ABI_COMPATIBLE string is printed out for
> debugging/info purposes.
I agree to disagree :)
It's KHO property, not it's users.
> > We still don't promise any compatibility between different kernel
> > versions so to avoid blocking this series on the decision what is the
> > best way to convey KHO data structures compatibility I suggest to bump
> > kho ABI version in v6.2* of the patch that adds KHO blocks and postpone
> > this discussion to after rc1 when we'll have plenty of time.
>
> Let's keep this patch as is for now. We will have a broader discussion
> when we convert other participants to this new scheme. If we decide not
> to pursue this approach, we will change this code to use an independent
> compatibility string. However, having this in place as a template will
> help us convert other components correctly, ensuring proper alignment
> and that correct string helpers like strncmp / strscpy are used—which I
> have already ensured is the case in LUO.
Pasha, this sounds like salami approach :)
We didn't agree yet to convert other components and even to use this
scheme globally. Changing this during -rc does not seem a good practice.
So whatever new versioning scheme we'll come up with, it'll have to wait
until v7.3.
Let's bump kho and LUO ABI versions and drop the concatenation for now.
It's a small change to the patches, so I don't see it as a blocker for
merging them in v7.2.
> > * sending a new version of a single file does same email traffic, but it
> > confuses b4 and quite possibly other tools, so I think v7 is better.
>
> Agreed, I also prefer re-sending the whole series...
>
> Pasha
>
> > > Pasha
> > >
> > > >
> > > > > For now, reviewers will have to make sure that if the ABI header content
> > > > > is changed, the compatibility string is updated.
> > > >
> > > --
> > > > Sincerely yours,
> > > > Mike.
> > >
> >
> >
>
^ permalink raw reply [flat|nested] 27+ messages in thread
* [PATCH v6 08/13] liveupdate: defer session block allocation and physical address setting
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (6 preceding siblings ...)
2026-06-03 3:28 ` [PATCH v6 07/13] kho: add support for linked-block serialization Pasha Tatashin
@ 2026-06-03 3:28 ` Pasha Tatashin
2026-06-03 3:29 ` [PATCH v6 09/13] liveupdate: Remove limit on the number of sessions Pasha Tatashin
` (4 subsequent siblings)
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:28 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
Currently, luo_session_setup_outgoing() allocates the session block and
sets its physical address in the header immediately. With upcoming
dynamic block-based session management, this makes the first block
different from the rest. Move the allocation to where it is first needed.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_core.c | 4 +-
kernel/liveupdate/luo_internal.h | 2 +-
kernel/liveupdate/luo_session.c | 68 ++++++++++++++++++++------------
3 files changed, 45 insertions(+), 29 deletions(-)
diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 69b00e7d0f8f..1b2bda22902d 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -165,9 +165,7 @@ static int __init luo_state_setup(void)
strscpy(luo_ser->compatible, LUO_ABI_COMPATIBLE, sizeof(luo_ser->compatible));
luo_ser->liveupdate_num = luo_global.liveupdate_num + 1;
- err = luo_session_setup_outgoing(&luo_ser->sessions_pa);
- if (err)
- goto exit_free_luo_ser;
+ luo_session_setup_outgoing(&luo_ser->sessions_pa);
err = luo_flb_setup_outgoing(&luo_ser->flbs_pa);
if (err)
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index fe22086bfbeb..ee18f9a11b91 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -79,7 +79,7 @@ extern struct rw_semaphore luo_register_rwlock;
int luo_session_create(const char *name, struct file **filep);
int luo_session_retrieve(const char *name, struct file **filep);
-int __init luo_session_setup_outgoing(u64 *sessions_pa);
+void __init luo_session_setup_outgoing(u64 *sessions_pa);
int __init luo_session_setup_incoming(u64 sessions_pa);
int luo_session_serialize(void);
int luo_session_deserialize(void);
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 1cd315e0f6de..2411849a34e3 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -108,15 +108,16 @@ static DECLARE_RWSEM(luo_session_serialize_rwsem);
/**
* struct luo_session_header - Header struct for managing LUO sessions.
- * @count: The number of sessions currently tracked in the @list.
- * @list: The head of the linked list of `struct luo_session` instances.
- * @rwsem: A read-write semaphore providing synchronized access to the
- * session list and other fields in this structure.
- * @header_ser: The header data of serialization array.
- * @ser: The serialized session data (an array of
- * `struct luo_session_ser`).
- * @active: Set to true when first initialized. If previous kernel did not
- * send session data, active stays false for incoming.
+ * @count: The number of sessions currently tracked in the @list.
+ * @list: The head of the linked list of `struct luo_session` instances.
+ * @rwsem: A read-write semaphore providing synchronized access to the
+ * session list and other fields in this structure.
+ * @header_ser: The header data of serialization array.
+ * @ser: The serialized session data (an array of
+ * `struct luo_session_ser`).
+ * @sessions_pa: Points to the location of sessions_pa within struct luo_ser.
+ * @active: Set to true when first initialized. If previous kernel did not
+ * send session data, active stays false for incoming.
*/
struct luo_session_header {
long count;
@@ -124,6 +125,7 @@ struct luo_session_header {
struct rw_semaphore rwsem;
struct luo_session_header_ser *header_ser;
struct luo_session_ser *ser;
+ u64 *sessions_pa;
bool active;
};
@@ -171,10 +173,30 @@ static void luo_session_free(struct luo_session *session)
kfree(session);
}
+static int luo_session_grow_ser(struct luo_session_header *sh)
+{
+ struct luo_session_header_ser *header_ser;
+
+ if (sh->count == LUO_SESSION_MAX)
+ return -ENOMEM;
+
+ if (sh->header_ser)
+ return 0;
+
+ header_ser = kho_alloc_preserve(LUO_SESSION_PGCNT << PAGE_SHIFT);
+ if (IS_ERR(header_ser))
+ return PTR_ERR(header_ser);
+
+ sh->header_ser = header_ser;
+ sh->ser = (void *)(header_ser + 1);
+ return 0;
+}
+
static int luo_session_insert(struct luo_session_header *sh,
struct luo_session *session)
{
struct luo_session *it;
+ int err;
guard(rwsem_write)(&sh->rwsem);
@@ -183,8 +205,9 @@ static int luo_session_insert(struct luo_session_header *sh,
* for new session.
*/
if (sh == &luo_session_global.outgoing) {
- if (sh->count == LUO_SESSION_MAX)
- return -ENOMEM;
+ err = luo_session_grow_ser(sh);
+ if (err)
+ return err;
}
/*
@@ -524,21 +547,10 @@ int luo_session_retrieve(const char *name, struct file **filep)
return err;
}
-int __init luo_session_setup_outgoing(u64 *sessions_pa)
+void __init luo_session_setup_outgoing(u64 *sessions_pa)
{
- struct luo_session_header_ser *header_ser;
-
- header_ser = kho_alloc_preserve(LUO_SESSION_PGCNT << PAGE_SHIFT);
- if (IS_ERR(header_ser))
- return PTR_ERR(header_ser);
-
- *sessions_pa = virt_to_phys(header_ser);
-
- luo_session_global.outgoing.header_ser = header_ser;
- luo_session_global.outgoing.ser = (void *)(header_ser + 1);
+ luo_session_global.outgoing.sessions_pa = sessions_pa;
luo_session_global.outgoing.active = true;
-
- return 0;
}
int __init luo_session_setup_incoming(u64 sessions_pa)
@@ -644,6 +656,8 @@ int luo_session_serialize(void)
down_write(&luo_session_serialize_rwsem);
down_write(&sh->rwsem);
+ *sh->sessions_pa = 0;
+
list_for_each_entry(session, &sh->list, list) {
err = luo_session_freeze_one(session, &sh->ser[i]);
if (err)
@@ -653,7 +667,11 @@ int luo_session_serialize(void)
sizeof(sh->ser[i].name));
i++;
}
- sh->header_ser->count = sh->count;
+
+ if (sh->header_ser && sh->count > 0) {
+ sh->header_ser->count = sh->count;
+ *sh->sessions_pa = virt_to_phys(sh->header_ser);
+ }
up_write(&sh->rwsem);
return 0;
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 09/13] liveupdate: Remove limit on the number of sessions
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (7 preceding siblings ...)
2026-06-03 3:28 ` [PATCH v6 08/13] liveupdate: defer session block allocation and physical address setting Pasha Tatashin
@ 2026-06-03 3:29 ` Pasha Tatashin
2026-06-03 3:29 ` [PATCH v6 10/13] liveupdate: Remove limit on the number of files per session Pasha Tatashin
` (3 subsequent siblings)
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:29 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
Currently, the number of LUO sessions is limited by a fixed number of
pre-allocated pages for serialization (16 pages, allowing for ~819
sessions).
This limitation is problematic if LUO is used to support things such as
systemd file descriptor store, and would be used not just as VM memory
but to save other states on the machine.
Remove this limit by transitioning to a linked-block approach for
session metadata serialization. Instead of a single contiguous block,
session metadata is now stored in a chain of 16-page blocks. Each block
starts with a header containing the physical address of the next block
and the number of session entries in the current block.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/kho/abi/luo.h | 24 +------
kernel/liveupdate/luo_session.c | 113 +++++++++++++++-----------------
2 files changed, 56 insertions(+), 81 deletions(-)
diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
index 9a4fe491812b..79758d92ed5f 100644
--- a/include/linux/kho/abi/luo.h
+++ b/include/linux/kho/abi/luo.h
@@ -33,11 +33,6 @@
* 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
- * preserved memory block and the number of `struct luo_session_ser`
- * entries that follow.
- *
* - struct luo_session_ser:
* Metadata for a single session, including its name and a physical pointer
* to another preserved memory block containing an array of
@@ -63,13 +58,15 @@
#define _LINUX_KHO_ABI_LUO_H
#include <linux/align.h>
+#include <linux/kho/abi/block.h>
#include <uapi/linux/liveupdate.h>
/*
* The LUO state is registered under this KHO entry name.
*/
#define LUO_KHO_ENTRY_NAME "LUO"
-#define LUO_ABI_COMPATIBLE "luo-v3"
+#define LUO_COMPAT_BASE "luo-v3"
+#define LUO_ABI_COMPATIBLE LUO_COMPAT_BASE "-" KHO_BLOCK_ABI_COMPATIBLE
#define LUO_ABI_COMPAT_LEN ALIGN(sizeof(LUO_ABI_COMPATIBLE), 8)
/**
@@ -118,21 +115,6 @@ struct luo_file_set_ser {
u64 count;
} __packed;
-/**
- * struct luo_session_header_ser - Header for the serialized session data block.
- * @count: The number of `struct luo_session_ser` entries that immediately
- * follow this header in the memory block.
- *
- * This structure is located at the beginning of a contiguous block of
- * 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_ABI_COMPATIBLE` must be updated.
- */
-struct luo_session_header_ser {
- u64 count;
-} __packed;
-
/**
* struct luo_session_ser - Represents the serialized metadata for a LUO session.
* @name: The unique name of the session, provided by the userspace at
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 2411849a34e3..b79b2a488974 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -24,9 +24,10 @@
* ioctls on /dev/liveupdate.
*
* - Serialization: Session metadata is preserved using the KHO framework. When
- * a live update is triggered via kexec, an array of `struct luo_session_ser`
- * is populated and placed in a preserved memory region. The physical address
- * of this array is stored in the centralized `struct luo_ser` structure.
+ * a live update is triggered via kexec, session metadata is serialized into
+ * a chain of linked-blocks and placed in a preserved memory region. The
+ * physical address of the first block header is stored in the centralized
+ * `struct luo_ser` structure.
*
* Session Lifecycle:
*
@@ -89,6 +90,7 @@
#include <linux/fs.h>
#include <linux/io.h>
#include <linux/kexec_handover.h>
+#include <linux/kho_block.h>
#include <linux/kho/abi/luo.h>
#include <linux/list.h>
#include <linux/liveupdate.h>
@@ -98,23 +100,14 @@
#include <uapi/linux/liveupdate.h>
#include "luo_internal.h"
-/* 16 4K pages, give space for 744 sessions */
-#define LUO_SESSION_PGCNT 16ul
-#define LUO_SESSION_MAX (((LUO_SESSION_PGCNT << PAGE_SHIFT) - \
- sizeof(struct luo_session_header_ser)) / \
- sizeof(struct luo_session_ser))
-
static DECLARE_RWSEM(luo_session_serialize_rwsem);
-
/**
* struct luo_session_header - Header struct for managing LUO sessions.
* @count: The number of sessions currently tracked in the @list.
* @list: The head of the linked list of `struct luo_session` instances.
* @rwsem: A read-write semaphore providing synchronized access to the
* session list and other fields in this structure.
- * @header_ser: The header data of serialization array.
- * @ser: The serialized session data (an array of
- * `struct luo_session_ser`).
+ * @block_set: The set of serialization blocks.
* @sessions_pa: Points to the location of sessions_pa within struct luo_ser.
* @active: Set to true when first initialized. If previous kernel did not
* send session data, active stays false for incoming.
@@ -123,8 +116,7 @@ struct luo_session_header {
long count;
struct list_head list;
struct rw_semaphore rwsem;
- struct luo_session_header_ser *header_ser;
- struct luo_session_ser *ser;
+ struct kho_block_set block_set;
u64 *sessions_pa;
bool active;
};
@@ -143,10 +135,14 @@ static struct luo_session_global luo_session_global = {
.incoming = {
.list = LIST_HEAD_INIT(luo_session_global.incoming.list),
.rwsem = __RWSEM_INITIALIZER(luo_session_global.incoming.rwsem),
+ .block_set = KHO_BLOCK_SET_INIT(luo_session_global.incoming.block_set,
+ sizeof(struct luo_session_ser)),
},
.outgoing = {
.list = LIST_HEAD_INIT(luo_session_global.outgoing.list),
.rwsem = __RWSEM_INITIALIZER(luo_session_global.outgoing.rwsem),
+ .block_set = KHO_BLOCK_SET_INIT(luo_session_global.outgoing.block_set,
+ sizeof(struct luo_session_ser)),
},
};
@@ -173,25 +169,6 @@ static void luo_session_free(struct luo_session *session)
kfree(session);
}
-static int luo_session_grow_ser(struct luo_session_header *sh)
-{
- struct luo_session_header_ser *header_ser;
-
- if (sh->count == LUO_SESSION_MAX)
- return -ENOMEM;
-
- if (sh->header_ser)
- return 0;
-
- header_ser = kho_alloc_preserve(LUO_SESSION_PGCNT << PAGE_SHIFT);
- if (IS_ERR(header_ser))
- return PTR_ERR(header_ser);
-
- sh->header_ser = header_ser;
- sh->ser = (void *)(header_ser + 1);
- return 0;
-}
-
static int luo_session_insert(struct luo_session_header *sh,
struct luo_session *session)
{
@@ -205,7 +182,7 @@ static int luo_session_insert(struct luo_session_header *sh,
* for new session.
*/
if (sh == &luo_session_global.outgoing) {
- err = luo_session_grow_ser(sh);
+ err = kho_block_set_grow(&sh->block_set, sh->count + 1);
if (err)
return err;
}
@@ -232,6 +209,8 @@ static void luo_session_remove(struct luo_session_header *sh,
guard(rwsem_write)(&sh->rwsem);
list_del(&session->list);
sh->count--;
+ if (sh == &luo_session_global.outgoing)
+ kho_block_set_shrink(&sh->block_set, sh->count);
}
static int luo_session_finish_one(struct luo_session *session)
@@ -555,15 +534,17 @@ void __init luo_session_setup_outgoing(u64 *sessions_pa)
int __init luo_session_setup_incoming(u64 sessions_pa)
{
- struct luo_session_header_ser *header_ser;
+ struct luo_session_header *sh = &luo_session_global.incoming;
+ int err;
- if (sessions_pa) {
- header_ser = phys_to_virt(sessions_pa);
- luo_session_global.incoming.header_ser = header_ser;
- luo_session_global.incoming.ser = (void *)(header_ser + 1);
- luo_session_global.incoming.active = true;
- }
+ if (!sessions_pa)
+ return 0;
+ err = kho_block_set_restore(&sh->block_set, sessions_pa);
+ if (err)
+ return err;
+
+ sh->active = true;
return 0;
}
@@ -605,6 +586,8 @@ int luo_session_deserialize(void)
{
struct luo_session_header *sh = &luo_session_global.incoming;
static bool is_deserialized;
+ struct luo_session_ser *ser;
+ struct kho_block_set_it it;
static int saved_err;
int err;
@@ -631,18 +614,19 @@ int luo_session_deserialize(void)
* userspace to detect the failure and trigger a reboot, which will
* reliably reset devices and reclaim memory.
*/
- for (int i = 0; i < sh->header_ser->count; i++) {
- err = luo_session_deserialize_one(sh, &sh->ser[i]);
+ kho_block_set_it_init(&it, &sh->block_set);
+ while ((ser = kho_block_set_it_read_entry(&it))) {
+ err = luo_session_deserialize_one(sh, ser);
if (err)
goto save_err;
}
- kho_restore_free(sh->header_ser);
- sh->header_ser = NULL;
- sh->ser = NULL;
+ kho_block_set_destroy(&sh->block_set);
return 0;
+
save_err:
+ kho_block_set_destroy(&sh->block_set);
saved_err = err;
return err;
}
@@ -651,36 +635,45 @@ int luo_session_serialize(void)
{
struct luo_session_header *sh = &luo_session_global.outgoing;
struct luo_session *session;
- int i = 0;
+ struct kho_block_set_it it;
int err;
down_write(&luo_session_serialize_rwsem);
down_write(&sh->rwsem);
*sh->sessions_pa = 0;
+ kho_block_set_it_init(&it, &sh->block_set);
+
list_for_each_entry(session, &sh->list, list) {
- err = luo_session_freeze_one(session, &sh->ser[i]);
- if (err)
+ struct luo_session_ser *ser = kho_block_set_it_reserve_entry(&it);
+
+ /* This should not fail normally as blocks were pre-allocated */
+ if (WARN_ON_ONCE(!ser)) {
+ err = -ENOSPC;
goto err_undo;
+ }
- strscpy(sh->ser[i].name, session->name,
- sizeof(sh->ser[i].name));
- i++;
- }
+ err = luo_session_freeze_one(session, ser);
+ if (err) {
+ kho_block_set_it_prev(&it);
+ goto err_undo;
+ }
- if (sh->header_ser && sh->count > 0) {
- sh->header_ser->count = sh->count;
- *sh->sessions_pa = virt_to_phys(sh->header_ser);
+ strscpy(ser->name, session->name, sizeof(ser->name));
}
+
+ if (sh->count > 0)
+ *sh->sessions_pa = kho_block_set_head_pa(&sh->block_set);
up_write(&sh->rwsem);
return 0;
err_undo:
list_for_each_entry_continue_reverse(session, &sh->list, list) {
- i--;
- luo_session_unfreeze_one(session, &sh->ser[i]);
- memset(sh->ser[i].name, 0, sizeof(sh->ser[i].name));
+ struct luo_session_ser *ser = kho_block_set_it_prev(&it);
+
+ luo_session_unfreeze_one(session, ser);
+ memset(ser->name, 0, sizeof(ser->name));
}
up_write(&sh->rwsem);
up_write(&luo_session_serialize_rwsem);
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 10/13] liveupdate: Remove limit on the number of files per session
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (8 preceding siblings ...)
2026-06-03 3:29 ` [PATCH v6 09/13] liveupdate: Remove limit on the number of sessions Pasha Tatashin
@ 2026-06-03 3:29 ` Pasha Tatashin
2026-06-03 3:29 ` [PATCH v6 11/13] selftests/liveupdate: Test session and file limit removal Pasha Tatashin
` (2 subsequent siblings)
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:29 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
To remove the fixed limit on the number of preserved files per session,
transition the file metadata serialization from a single contiguous
memory block to a chain of linked blocks.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/kho/abi/luo.h | 13 +--
kernel/liveupdate/luo_file.c | 138 ++++++++++++++-----------------
kernel/liveupdate/luo_internal.h | 6 +-
3 files changed, 74 insertions(+), 83 deletions(-)
diff --git a/include/linux/kho/abi/luo.h b/include/linux/kho/abi/luo.h
index 79758d92ed5f..16df550ef143 100644
--- a/include/linux/kho/abi/luo.h
+++ b/include/linux/kho/abi/luo.h
@@ -35,8 +35,8 @@
*
* - struct luo_session_ser:
* Metadata for a single session, including its name and a physical pointer
- * to another preserved memory block containing an array of
- * `struct luo_file_ser` for all files in that session.
+ * to the first `struct kho_block_header_ser` for all files in that session.
+ * Multiple blocks are linked via the `next` field in the header.
*
* - struct luo_file_ser:
* Metadata for a single preserved file. Contains the `compatible` string to
@@ -65,7 +65,7 @@
* The LUO state is registered under this KHO entry name.
*/
#define LUO_KHO_ENTRY_NAME "LUO"
-#define LUO_COMPAT_BASE "luo-v3"
+#define LUO_COMPAT_BASE "luo-v4"
#define LUO_ABI_COMPATIBLE LUO_COMPAT_BASE "-" KHO_BLOCK_ABI_COMPATIBLE
#define LUO_ABI_COMPAT_LEN ALIGN(sizeof(LUO_ABI_COMPATIBLE), 8)
@@ -103,9 +103,10 @@ struct luo_file_ser {
/**
* struct luo_file_set_ser - Represents the serialized metadata for file set
- * @files: The physical address of a contiguous memory block that holds
- * the serialized state of files (array of luo_file_ser) in this file
- * set.
+ * @files: The physical address of the first `struct kho_block_header_ser`.
+ * This structure is the header for a block of memory containing
+ * an array of `struct luo_file_ser` entries. Multiple blocks are
+ * linked via the `next` field in the header.
* @count: The total number of files that were part of this session during
* serialization. Used for iteration and validation during
* restoration.
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
index 9eec07a9e9fc..c39f96961a85 100644
--- a/kernel/liveupdate/luo_file.c
+++ b/kernel/liveupdate/luo_file.c
@@ -118,11 +118,6 @@ static LIST_HEAD(luo_file_handler_list);
/* Keep track of files being preserved by LUO */
static DEFINE_XARRAY(luo_preserved_files);
-/* 2 4K pages, give space for 128 files per file_set */
-#define LUO_FILE_PGCNT 2ul
-#define LUO_FILE_MAX \
- ((LUO_FILE_PGCNT << PAGE_SHIFT) / sizeof(struct luo_file_ser))
-
/**
* struct luo_file - Represents a single preserved file instance.
* @fh: Pointer to the &struct liveupdate_file_handler that manages
@@ -174,39 +169,6 @@ struct luo_file {
u64 token;
};
-static int luo_alloc_files_mem(struct luo_file_set *file_set)
-{
- size_t size;
- void *mem;
-
- if (file_set->files)
- return 0;
-
- WARN_ON_ONCE(file_set->count);
-
- size = LUO_FILE_PGCNT << PAGE_SHIFT;
- mem = kho_alloc_preserve(size);
- if (IS_ERR(mem))
- return PTR_ERR(mem);
-
- file_set->files = mem;
-
- return 0;
-}
-
-static void luo_free_files_mem(struct luo_file_set *file_set)
-{
- /* If file_set has files, no need to free preservation memory */
- if (file_set->count)
- return;
-
- if (!file_set->files)
- return;
-
- kho_unpreserve_free(file_set->files);
- file_set->files = NULL;
-}
-
static unsigned long luo_get_id(struct liveupdate_file_handler *fh,
struct file *file)
{
@@ -276,16 +238,15 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
if (luo_token_is_used(file_set, token))
return -EEXIST;
- if (file_set->count == LUO_FILE_MAX)
- return -ENOSPC;
+ err = kho_block_set_grow(&file_set->block_set, file_set->count + 1);
+ if (err)
+ return err;
file = fget(fd);
- if (!file)
- return -EBADF;
-
- err = luo_alloc_files_mem(file_set);
- if (err)
- goto err_fput;
+ if (!file) {
+ err = -EBADF;
+ goto err_shrink;
+ }
err = -ENOENT;
down_read(&luo_register_rwlock);
@@ -300,7 +261,7 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
/* err is still -ENOENT if no handler was found */
if (err)
- goto err_free_files_mem;
+ goto err_fput;
err = xa_insert(&luo_preserved_files, luo_get_id(fh, file),
file, GFP_KERNEL);
@@ -343,10 +304,10 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd)
xa_erase(&luo_preserved_files, luo_get_id(fh, file));
err_module_put:
module_put(fh->ops->owner);
-err_free_files_mem:
- luo_free_files_mem(file_set);
err_fput:
fput(file);
+err_shrink:
+ kho_block_set_shrink(&file_set->block_set, file_set->count);
return err;
}
@@ -392,13 +353,14 @@ void luo_file_unpreserve_files(struct luo_file_set *file_set)
list_del(&luo_file->list);
file_set->count--;
+ kho_block_set_shrink(&file_set->block_set, file_set->count);
fput(luo_file->file);
mutex_destroy(&luo_file->mutex);
kfree(luo_file);
}
- luo_free_files_mem(file_set);
+ kho_block_set_destroy(&file_set->block_set);
}
static int luo_file_freeze_one(struct luo_file_set *file_set,
@@ -454,7 +416,7 @@ static void __luo_file_unfreeze(struct luo_file_set *file_set,
luo_file_unfreeze_one(file_set, luo_file);
}
- memset(file_set->files, 0, LUO_FILE_PGCNT << PAGE_SHIFT);
+ kho_block_set_clear(&file_set->block_set);
}
/**
@@ -493,19 +455,24 @@ static void __luo_file_unfreeze(struct luo_file_set *file_set,
int luo_file_freeze(struct luo_file_set *file_set,
struct luo_file_set_ser *file_set_ser)
{
- struct luo_file_ser *file_ser = file_set->files;
struct luo_file *luo_file;
+ struct kho_block_set_it it;
int err;
- int i;
if (!file_set->count)
return 0;
- if (WARN_ON(!file_ser))
- return -EINVAL;
+ kho_block_set_it_init(&it, &file_set->block_set);
- i = 0;
list_for_each_entry(luo_file, &file_set->files_list, list) {
+ struct luo_file_ser *file_ser = kho_block_set_it_reserve_entry(&it);
+
+ /* This should not fail normally as blocks were pre-allocated */
+ if (WARN_ON_ONCE(!file_ser)) {
+ err = -ENOSPC;
+ goto err_unfreeze;
+ }
+
err = luo_file_freeze_one(file_set, luo_file);
if (err < 0) {
pr_warn("Freeze failed for token[%#0llx] handler[%s] err[%pe]\n",
@@ -514,16 +481,14 @@ int luo_file_freeze(struct luo_file_set *file_set,
goto err_unfreeze;
}
- strscpy(file_ser[i].compatible, luo_file->fh->compatible,
- sizeof(file_ser[i].compatible));
- file_ser[i].data = luo_file->serialized_data;
- file_ser[i].token = luo_file->token;
- i++;
+ strscpy(file_ser->compatible, luo_file->fh->compatible,
+ sizeof(file_ser->compatible));
+ file_ser->data = luo_file->serialized_data;
+ file_ser->token = luo_file->token;
}
file_set_ser->count = file_set->count;
- if (file_set->files)
- file_set_ser->files = virt_to_phys(file_set->files);
+ file_set_ser->files = kho_block_set_head_pa(&file_set->block_set);
return 0;
@@ -741,14 +706,12 @@ int luo_file_finish(struct luo_file_set *file_set)
module_put(luo_file->fh->ops->owner);
list_del(&luo_file->list);
file_set->count--;
+ kho_block_set_shrink(&file_set->block_set, file_set->count);
mutex_destroy(&luo_file->mutex);
kfree(luo_file);
}
- if (file_set->files) {
- kho_restore_free(file_set->files);
- file_set->files = NULL;
- }
+ kho_block_set_destroy(&file_set->block_set);
return 0;
}
@@ -822,16 +785,18 @@ int luo_file_deserialize(struct luo_file_set *file_set,
struct luo_file_set_ser *file_set_ser)
{
struct luo_file_ser *file_ser;
+ struct kho_block_set_it it;
int err;
- u64 i;
if (!file_set_ser->files) {
WARN_ON(file_set_ser->count);
return 0;
}
- file_set->count = file_set_ser->count;
- file_set->files = phys_to_virt(file_set_ser->files);
+ file_set->count = 0;
+ err = kho_block_set_restore(&file_set->block_set, file_set_ser->files);
+ if (err)
+ return err;
/*
* Note on error handling:
@@ -848,25 +813,50 @@ int luo_file_deserialize(struct luo_file_set *file_set,
* userspace to detect the failure and trigger a reboot, which will
* reliably reset devices and reclaim memory.
*/
- file_ser = file_set->files;
- for (i = 0; i < file_set->count; i++) {
- err = luo_file_deserialize_one(file_set, &file_ser[i]);
+ kho_block_set_it_init(&it, &file_set->block_set);
+ while ((file_ser = kho_block_set_it_read_entry(&it))) {
+ err = luo_file_deserialize_one(file_set, file_ser);
if (err)
- return err;
+ goto err_destroy_blocks;
+ file_set->count++;
+ }
+
+ if (file_set->count != file_set_ser->count) {
+ pr_warn("File count mismatch: expected %llu, found %llu\n",
+ file_set_ser->count, file_set->count);
+ err = -EINVAL;
+ goto err_destroy_blocks;
}
return 0;
+
+err_destroy_blocks:
+ while (!list_empty(&file_set->files_list)) {
+ struct luo_file *luo_file;
+
+ luo_file = list_first_entry(&file_set->files_list,
+ struct luo_file, list);
+ list_del(&luo_file->list);
+ module_put(luo_file->fh->ops->owner);
+ mutex_destroy(&luo_file->mutex);
+ kfree(luo_file);
+ }
+ file_set->count = 0;
+ kho_block_set_destroy(&file_set->block_set);
+ return err;
}
void luo_file_set_init(struct luo_file_set *file_set)
{
INIT_LIST_HEAD(&file_set->files_list);
+ kho_block_set_init(&file_set->block_set, sizeof(struct luo_file_ser));
}
void luo_file_set_destroy(struct luo_file_set *file_set)
{
WARN_ON(file_set->count);
WARN_ON(!list_empty(&file_set->files_list));
+ WARN_ON(!kho_block_set_is_empty(&file_set->block_set));
}
/**
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index ee18f9a11b91..64879ffe7378 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -10,6 +10,7 @@
#include <linux/liveupdate.h>
#include <linux/uaccess.h>
+#include <linux/kho_block.h>
struct luo_ucmd {
void __user *ubuffer;
@@ -44,14 +45,13 @@ static inline int luo_ucmd_respond(struct luo_ucmd *ucmd,
* struct luo_file_set - A set of files that belong to the same sessions.
* @files_list: An ordered list of files associated with this session, it is
* ordered by preservation time.
- * @files: The physically contiguous memory block that holds the serialized
- * state of files.
+ * @block_set: The set of serialization blocks.
* @count: A counter tracking the number of files currently stored in the
* @files_list for this session.
*/
struct luo_file_set {
struct list_head files_list;
- struct luo_file_ser *files;
+ struct kho_block_set block_set;
u64 count;
};
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 11/13] selftests/liveupdate: Test session and file limit removal
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (9 preceding siblings ...)
2026-06-03 3:29 ` [PATCH v6 10/13] liveupdate: Remove limit on the number of files per session Pasha Tatashin
@ 2026-06-03 3:29 ` Pasha Tatashin
2026-06-03 3:29 ` [PATCH v6 12/13] selftests/liveupdate: Add stress-sessions kexec test Pasha Tatashin
2026-06-03 3:29 ` [PATCH v6 13/13] selftests/liveupdate: Add stress-files " Pasha Tatashin
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:29 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
With the removal of static limits on the number of sessions and files per
session, the orchestrator now uses dynamic allocation.
Add new test cases to verify that the system can handle a large number of
sessions and files. These tests ensure that the dynamic block allocation
and reuse logic for session metadata and outgoing files work correctly
beyond the previous static limits.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
.../testing/selftests/liveupdate/liveupdate.c | 75 +++++++++++++++++++
.../selftests/liveupdate/luo_test_utils.c | 24 ++++++
.../selftests/liveupdate/luo_test_utils.h | 2 +
3 files changed, 101 insertions(+)
diff --git a/tools/testing/selftests/liveupdate/liveupdate.c b/tools/testing/selftests/liveupdate/liveupdate.c
index c7d94b9181e1..502fb3567e38 100644
--- a/tools/testing/selftests/liveupdate/liveupdate.c
+++ b/tools/testing/selftests/liveupdate/liveupdate.c
@@ -26,6 +26,7 @@
#include <linux/liveupdate.h>
+#include "luo_test_utils.h"
#include "../kselftest.h"
#include "../kselftest_harness.h"
@@ -499,4 +500,78 @@ TEST_F(liveupdate_device, get_session_name_max_length)
ASSERT_EQ(close(session_fd), 0);
}
+/*
+ * Test Case: Manage Many Sessions
+ *
+ * Verifies that a large number of sessions can be created and then
+ * destroyed during normal system operation. This specifically tests the
+ * dynamic block allocation and reuse logic for session metadata management
+ * without preserving any files.
+ */
+TEST_F(liveupdate_device, preserve_many_sessions)
+{
+#define MANY_SESSIONS 2000
+ int session_fds[MANY_SESSIONS];
+ int ret, i;
+
+ self->fd1 = open(LIVEUPDATE_DEV, O_RDWR);
+ if (self->fd1 < 0 && errno == ENOENT)
+ SKIP(return, "%s does not exist", LIVEUPDATE_DEV);
+ ASSERT_GE(self->fd1, 0);
+
+ ret = luo_ensure_nofile_limit(MANY_SESSIONS);
+ if (ret == -EPERM)
+ SKIP(return, "Insufficient privileges to set RLIMIT_NOFILE");
+ ASSERT_EQ(ret, 0);
+
+ for (i = 0; i < MANY_SESSIONS; i++) {
+ char name[64];
+
+ snprintf(name, sizeof(name), "many-session-%d", i);
+ session_fds[i] = create_session(self->fd1, name);
+ ASSERT_GE(session_fds[i], 0);
+ }
+
+ for (i = 0; i < MANY_SESSIONS; i++)
+ ASSERT_EQ(close(session_fds[i]), 0);
+}
+
+/*
+ * Test Case: Preserve Many Files
+ *
+ * Verifies that a large number of files can be preserved in a single session
+ * and then destroyed during normal system operation. This tests the dynamic
+ * block allocation and management for outgoing files.
+ */
+TEST_F(liveupdate_device, preserve_many_files)
+{
+#define MANY_FILES 500
+ int mem_fds[MANY_FILES];
+ int session_fd, ret, i;
+
+ self->fd1 = open(LIVEUPDATE_DEV, O_RDWR);
+ if (self->fd1 < 0 && errno == ENOENT)
+ SKIP(return, "%s does not exist", LIVEUPDATE_DEV);
+ ASSERT_GE(self->fd1, 0);
+
+ session_fd = create_session(self->fd1, "many-files-test");
+ ASSERT_GE(session_fd, 0);
+
+ ret = luo_ensure_nofile_limit(MANY_FILES + 10);
+ if (ret == -EPERM)
+ SKIP(return, "Insufficient privileges to set RLIMIT_NOFILE");
+ ASSERT_EQ(ret, 0);
+
+ for (i = 0; i < MANY_FILES; i++) {
+ mem_fds[i] = memfd_create("test-memfd", 0);
+ ASSERT_GE(mem_fds[i], 0);
+ ASSERT_EQ(preserve_fd(session_fd, mem_fds[i], i), 0);
+ }
+
+ for (i = 0; i < MANY_FILES; i++)
+ ASSERT_EQ(close(mem_fds[i]), 0);
+
+ ASSERT_EQ(close(session_fd), 0);
+}
+
TEST_HARNESS_MAIN
diff --git a/tools/testing/selftests/liveupdate/luo_test_utils.c b/tools/testing/selftests/liveupdate/luo_test_utils.c
index 3c8721c505df..333a3530051b 100644
--- a/tools/testing/selftests/liveupdate/luo_test_utils.c
+++ b/tools/testing/selftests/liveupdate/luo_test_utils.c
@@ -17,6 +17,7 @@
#include <sys/syscall.h>
#include <sys/mman.h>
#include <sys/types.h>
+#include <sys/resource.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdarg.h>
@@ -28,6 +29,29 @@ int luo_open_device(void)
return open(LUO_DEVICE, O_RDWR);
}
+int luo_ensure_nofile_limit(long min_limit)
+{
+ struct rlimit hl;
+
+ /* Allow to extra files to be used by test itself */
+ min_limit += 32;
+
+ if (getrlimit(RLIMIT_NOFILE, &hl) < 0)
+ return -errno;
+
+ if (hl.rlim_cur >= min_limit)
+ return 0;
+
+ hl.rlim_cur = min_limit;
+ if (hl.rlim_cur > hl.rlim_max)
+ hl.rlim_max = hl.rlim_cur;
+
+ if (setrlimit(RLIMIT_NOFILE, &hl) < 0)
+ return -errno;
+
+ return 0;
+}
+
int luo_create_session(int luo_fd, const char *name)
{
struct liveupdate_ioctl_create_session arg = { .size = sizeof(arg) };
diff --git a/tools/testing/selftests/liveupdate/luo_test_utils.h b/tools/testing/selftests/liveupdate/luo_test_utils.h
index 90099bf49577..6a0d85386613 100644
--- a/tools/testing/selftests/liveupdate/luo_test_utils.h
+++ b/tools/testing/selftests/liveupdate/luo_test_utils.h
@@ -26,6 +26,8 @@ int luo_create_session(int luo_fd, const char *name);
int luo_retrieve_session(int luo_fd, const char *name);
int luo_session_finish(int session_fd);
+int luo_ensure_nofile_limit(long min_limit);
+
int create_and_preserve_memfd(int session_fd, int token, const char *data);
int restore_and_verify_memfd(int session_fd, int token, const char *expected_data);
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 12/13] selftests/liveupdate: Add stress-sessions kexec test
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (10 preceding siblings ...)
2026-06-03 3:29 ` [PATCH v6 11/13] selftests/liveupdate: Test session and file limit removal Pasha Tatashin
@ 2026-06-03 3:29 ` Pasha Tatashin
2026-06-03 3:29 ` [PATCH v6 13/13] selftests/liveupdate: Add stress-files " Pasha Tatashin
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:29 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
Add a new test that creates 2000 LUO sessions before a kexec
reboot and verifies their presence after the reboot. This ensures
that the linked-block serialization mechanism works correctly for
a large number of sessions.
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
tools/testing/selftests/liveupdate/Makefile | 1 +
.../liveupdate/luo_stress_sessions.c | 102 ++++++++++++++++++
2 files changed, 103 insertions(+)
create mode 100644 tools/testing/selftests/liveupdate/luo_stress_sessions.c
diff --git a/tools/testing/selftests/liveupdate/Makefile b/tools/testing/selftests/liveupdate/Makefile
index 080754787ede..ed7534468386 100644
--- a/tools/testing/selftests/liveupdate/Makefile
+++ b/tools/testing/selftests/liveupdate/Makefile
@@ -6,6 +6,7 @@ TEST_GEN_PROGS += liveupdate
TEST_GEN_PROGS_EXTENDED += luo_kexec_simple
TEST_GEN_PROGS_EXTENDED += luo_multi_session
+TEST_GEN_PROGS_EXTENDED += luo_stress_sessions
TEST_FILES += do_kexec.sh
diff --git a/tools/testing/selftests/liveupdate/luo_stress_sessions.c b/tools/testing/selftests/liveupdate/luo_stress_sessions.c
new file mode 100644
index 000000000000..f201b1839d1d
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/luo_stress_sessions.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (c) 2026, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ *
+ * Validate that LUO can handle a large number of sessions across a kexec
+ * reboot.
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include "luo_test_utils.h"
+
+#define NUM_SESSIONS 2000
+#define STATE_SESSION_NAME "kexec_many_state"
+#define STATE_MEMFD_TOKEN 999
+
+/* Stage 1: Executed before the kexec reboot. */
+static void run_stage_1(int luo_fd)
+{
+ int ret, i;
+
+ ksft_print_msg("[STAGE 1] Increasing ulimit for open files...\n");
+ ret = luo_ensure_nofile_limit(NUM_SESSIONS);
+ if (ret == -EPERM)
+ ksft_exit_skip("Insufficient privileges to set RLIMIT_NOFILE\n");
+ if (ret < 0)
+ ksft_exit_fail_msg("luo_ensure_nofile_limit failed: %s\n", strerror(-ret));
+
+ ksft_print_msg("[STAGE 1] Creating state file for next stage (2)...\n");
+ create_state_file(luo_fd, STATE_SESSION_NAME, STATE_MEMFD_TOKEN, 2);
+
+ ksft_print_msg("[STAGE 1] Creating %d sessions...\n", NUM_SESSIONS);
+
+ for (i = 0; i < NUM_SESSIONS; i++) {
+ char name[LIVEUPDATE_SESSION_NAME_LENGTH];
+ int s_fd;
+
+ snprintf(name, sizeof(name), "many-test-%d", i);
+ s_fd = luo_create_session(luo_fd, name);
+ if (s_fd < 0) {
+ fail_exit("luo_create_session for '%s' at index %d",
+ name, i);
+ }
+ }
+
+ ksft_print_msg("[STAGE 1] Successfully created %d sessions.\n",
+ NUM_SESSIONS);
+
+ close(luo_fd);
+ daemonize_and_wait();
+}
+
+/* Stage 2: Executed after the kexec reboot. */
+static void run_stage_2(int luo_fd, int state_session_fd)
+{
+ int i, stage;
+
+ ksft_print_msg("[STAGE 2] Starting post-kexec verification...\n");
+
+ restore_and_read_stage(state_session_fd, STATE_MEMFD_TOKEN, &stage);
+ if (stage != 2) {
+ fail_exit("Expected stage 2, but state file contains %d",
+ stage);
+ }
+
+ ksft_print_msg("[STAGE 2] Retrieving and finishing %d sessions...\n",
+ NUM_SESSIONS);
+
+ for (i = 0; i < NUM_SESSIONS; i++) {
+ char name[LIVEUPDATE_SESSION_NAME_LENGTH];
+ int s_fd;
+
+ snprintf(name, sizeof(name), "many-test-%d", i);
+ s_fd = luo_retrieve_session(luo_fd, name);
+ if (s_fd < 0) {
+ fail_exit("luo_retrieve_session for '%s' at index %d",
+ name, i);
+ }
+
+ if (luo_session_finish(s_fd) < 0) {
+ fail_exit("luo_session_finish for '%s' at index %d",
+ name, i);
+ }
+ close(s_fd);
+ }
+
+ ksft_print_msg("[STAGE 2] Finalizing state session...\n");
+ if (luo_session_finish(state_session_fd) < 0)
+ fail_exit("luo_session_finish for state session");
+ close(state_session_fd);
+
+ ksft_print_msg("\n--- MANY-SESSIONS KEXEC TEST PASSED (%d sessions) ---\n",
+ NUM_SESSIONS);
+}
+
+int main(int argc, char *argv[])
+{
+ return luo_test(argc, argv, STATE_SESSION_NAME,
+ run_stage_1, run_stage_2);
+}
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread* [PATCH v6 13/13] selftests/liveupdate: Add stress-files kexec test
2026-06-03 3:28 [PATCH v6 00/13] liveupdate: Remove limits on sessions and files Pasha Tatashin
` (11 preceding siblings ...)
2026-06-03 3:29 ` [PATCH v6 12/13] selftests/liveupdate: Add stress-sessions kexec test Pasha Tatashin
@ 2026-06-03 3:29 ` Pasha Tatashin
12 siblings, 0 replies; 27+ messages in thread
From: Pasha Tatashin @ 2026-06-03 3:29 UTC (permalink / raw)
To: linux-kselftest, rppt, shuah, akpm, linux-mm, skhan, linux-doc,
linux-kernel, corbet, pasha.tatashin, dmatlack, kexec, pratyush,
skhawaja, graf
Add a new luo_stress_files kexec test that verifies preserving and
retrieving 500 files across a kexec reboot.
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>
---
tools/testing/selftests/liveupdate/Makefile | 1 +
.../selftests/liveupdate/luo_stress_files.c | 97 +++++++++++++++++++
2 files changed, 98 insertions(+)
create mode 100644 tools/testing/selftests/liveupdate/luo_stress_files.c
diff --git a/tools/testing/selftests/liveupdate/Makefile b/tools/testing/selftests/liveupdate/Makefile
index ed7534468386..30689d22cb02 100644
--- a/tools/testing/selftests/liveupdate/Makefile
+++ b/tools/testing/selftests/liveupdate/Makefile
@@ -7,6 +7,7 @@ TEST_GEN_PROGS += liveupdate
TEST_GEN_PROGS_EXTENDED += luo_kexec_simple
TEST_GEN_PROGS_EXTENDED += luo_multi_session
TEST_GEN_PROGS_EXTENDED += luo_stress_sessions
+TEST_GEN_PROGS_EXTENDED += luo_stress_files
TEST_FILES += do_kexec.sh
diff --git a/tools/testing/selftests/liveupdate/luo_stress_files.c b/tools/testing/selftests/liveupdate/luo_stress_files.c
new file mode 100644
index 000000000000..0cdf9cd4bac7
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/luo_stress_files.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (c) 2026, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ *
+ * Validate that LUO can handle a large number of files per session across
+ * a kexec reboot.
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include "luo_test_utils.h"
+
+#define NUM_FILES 500
+#define STATE_SESSION_NAME "kexec_many_files_state"
+#define STATE_MEMFD_TOKEN 9999
+#define TEST_SESSION_NAME "many_files_session"
+
+/* Stage 1: Executed before the kexec reboot. */
+static void run_stage_1(int luo_fd)
+{
+ int session_fd, i;
+
+ ksft_print_msg("[STAGE 1] Creating state file for next stage (2)...\n");
+ create_state_file(luo_fd, STATE_SESSION_NAME, STATE_MEMFD_TOKEN, 2);
+
+ ksft_print_msg("[STAGE 1] Creating test session '%s'...\n", TEST_SESSION_NAME);
+ session_fd = luo_create_session(luo_fd, TEST_SESSION_NAME);
+ if (session_fd < 0)
+ fail_exit("luo_create_session");
+
+ ksft_print_msg("[STAGE 1] Preserving %d files...\n", NUM_FILES);
+ for (i = 0; i < NUM_FILES; i++) {
+ char data[64];
+
+ snprintf(data, sizeof(data), "file-data-%d", i);
+ if (create_and_preserve_memfd(session_fd, i, data) < 0)
+ fail_exit("create_and_preserve_memfd for index %d", i);
+ }
+
+ ksft_print_msg("[STAGE 1] Successfully preserved %d files.\n", NUM_FILES);
+
+ close(luo_fd);
+ daemonize_and_wait();
+}
+
+/* Stage 2: Executed after the kexec reboot. */
+static void run_stage_2(int luo_fd, int state_session_fd)
+{
+ int session_fd;
+ int i, stage;
+
+ ksft_print_msg("[STAGE 2] Starting post-kexec verification...\n");
+
+ restore_and_read_stage(state_session_fd, STATE_MEMFD_TOKEN, &stage);
+ if (stage != 2) {
+ fail_exit("Expected stage 2, but state file contains %d",
+ stage);
+ }
+
+ ksft_print_msg("[STAGE 2] Retrieving test session '%s'...\n", TEST_SESSION_NAME);
+ session_fd = luo_retrieve_session(luo_fd, TEST_SESSION_NAME);
+ if (session_fd < 0)
+ fail_exit("luo_retrieve_session");
+
+ ksft_print_msg("[STAGE 2] Verifying %d files...\n", NUM_FILES);
+ for (i = 0; i < NUM_FILES; i++) {
+ char data[64];
+ int fd;
+
+ snprintf(data, sizeof(data), "file-data-%d", i);
+ fd = restore_and_verify_memfd(session_fd, i, data);
+ if (fd < 0)
+ fail_exit("restore_and_verify_memfd for index %d", i);
+ close(fd);
+ }
+
+ ksft_print_msg("[STAGE 2] Finishing test session...\n");
+ if (luo_session_finish(session_fd) < 0)
+ fail_exit("luo_session_finish for test session");
+ close(session_fd);
+
+ ksft_print_msg("[STAGE 2] Finalizing state session...\n");
+ if (luo_session_finish(state_session_fd) < 0)
+ fail_exit("luo_session_finish for state session");
+ close(state_session_fd);
+
+ ksft_print_msg("\n--- MANY-FILES KEXEC TEST PASSED (%d files) ---\n",
+ NUM_FILES);
+}
+
+int main(int argc, char *argv[])
+{
+ return luo_test(argc, argv, STATE_SESSION_NAME,
+ run_stage_1, run_stage_2);
+}
--
2.53.0
^ permalink raw reply related [flat|nested] 27+ messages in thread