* [PATCH v4 23/30] mm: shmem: export some functions to internal.h
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
From: Pratyush Yadav <ptyadav@amazon.de>
shmem_inode_acct_blocks(), shmem_recalc_inode(), and
shmem_add_to_page_cache() are used by shmem_alloc_and_add_folio(). This
functionality will also be used in the future by Live Update
Orchestrator (LUO) to recreate memfd files after a live update.
Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
mm/internal.h | 6 ++++++
mm/shmem.c | 10 +++++-----
2 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 1561fc2ff5b8..4ba155524f80 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1562,6 +1562,12 @@ void __meminit __init_page_from_nid(unsigned long pfn, int nid);
unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
int priority);
+int shmem_add_to_page_cache(struct folio *folio,
+ struct address_space *mapping,
+ pgoff_t index, void *expected, gfp_t gfp);
+int shmem_inode_acct_blocks(struct inode *inode, long pages);
+bool shmem_recalc_inode(struct inode *inode, long alloced, long swapped);
+
#ifdef CONFIG_SHRINKER_DEBUG
static inline __printf(2, 0) int shrinker_debugfs_name_alloc(
struct shrinker *shrinker, const char *fmt, va_list ap)
diff --git a/mm/shmem.c b/mm/shmem.c
index bd7d9afe5a27..4647a0b2831c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -219,7 +219,7 @@ static inline void shmem_unacct_blocks(unsigned long flags, long pages)
vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
}
-static int shmem_inode_acct_blocks(struct inode *inode, long pages)
+int shmem_inode_acct_blocks(struct inode *inode, long pages)
{
struct shmem_inode_info *info = SHMEM_I(inode);
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
@@ -435,7 +435,7 @@ static void shmem_free_inode(struct super_block *sb, size_t freed_ispace)
*
* Return: true if swapped was incremented from 0, for shmem_writeout().
*/
-static bool shmem_recalc_inode(struct inode *inode, long alloced, long swapped)
+bool shmem_recalc_inode(struct inode *inode, long alloced, long swapped)
{
struct shmem_inode_info *info = SHMEM_I(inode);
bool first_swapped = false;
@@ -861,9 +861,9 @@ static void shmem_update_stats(struct folio *folio, int nr_pages)
/*
* Somewhat like filemap_add_folio, but error if expected item has gone.
*/
-static int shmem_add_to_page_cache(struct folio *folio,
- struct address_space *mapping,
- pgoff_t index, void *expected, gfp_t gfp)
+int shmem_add_to_page_cache(struct folio *folio,
+ struct address_space *mapping,
+ pgoff_t index, void *expected, gfp_t gfp)
{
XA_STATE_ORDER(xas, &mapping->i_pages, index, folio_order(folio));
unsigned long nr = folio_nr_pages(folio);
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 11/30] liveupdate: luo_session: Add sessions support
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Introduce concept of "Live Update Sessions" within the LUO framework.
LUO sessions provide a mechanism to group and manage `struct file *`
instances (representing file descriptors) that need to be preserved
across a kexec-based live update.
Each session is identified by a unique name and acts as a container
for file objects whose state is critical to a userspace workload, such
as a virtual machine or a high-performance database, aiming to maintain
their functionality across a kernel transition.
This groundwork establishes the framework for preserving file-backed
state across kernel updates, with the actual file data preservation
mechanisms to be implemented in subsequent patches.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/uapi/linux/liveupdate.h | 3 +
kernel/liveupdate/Makefile | 1 +
kernel/liveupdate/luo_internal.h | 34 ++
kernel/liveupdate/luo_session.c | 607 +++++++++++++++++++++++++++++++
4 files changed, 645 insertions(+)
create mode 100644 kernel/liveupdate/luo_session.c
diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h
index 3cb09b2c4353..e8c0c210a790 100644
--- a/include/uapi/linux/liveupdate.h
+++ b/include/uapi/linux/liveupdate.h
@@ -91,4 +91,7 @@ enum liveupdate_event {
LIVEUPDATE_CANCEL = 3,
};
+/* The maximum length of session name including null termination */
+#define LIVEUPDATE_SESSION_NAME_LENGTH 56
+
#endif /* _UAPI_LIVEUPDATE_H */
diff --git a/kernel/liveupdate/Makefile b/kernel/liveupdate/Makefile
index 2881bab0c6df..f64cfc92cbf0 100644
--- a/kernel/liveupdate/Makefile
+++ b/kernel/liveupdate/Makefile
@@ -3,6 +3,7 @@
luo-y := \
luo_core.o \
luo_ioctl.o \
+ luo_session.o \
luo_subsystems.o
obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index c62fbbb0790c..9223f71844ca 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -32,6 +32,40 @@ void *luo_contig_alloc_preserve(size_t size);
void luo_contig_free_unpreserve(void *mem, size_t size);
void luo_contig_free_restore(void *mem, size_t size);
+/**
+ * struct luo_session - Represents an active or incoming Live Update session.
+ * @name: A unique name for this session, used for identification and
+ * retrieval.
+ * @files_xa: An xarray used to store the files associated with this session.
+ * @ser: Pointer to the serialized data for this session.
+ * @count: A counter tracking the number of files currently stored in the
+ * @files_xa for this session.
+ * @list: A list_head member used to link this session into a global list
+ * of either outgoing (to be preserved) or incoming (restored from
+ * previous kernel) sessions.
+ * @retrieved: A boolean flag indicating whether this session has been retrieved
+ * by a consumer in the new kernel. Valid only during the
+ * LIVEUPDATE_STATE_UPDATED state.
+ * @mutex: Session lock, protects files_xa, and count.
+ * @state: State of this session: prepared/frozen/updated/normal.
+ * @files: The physical address of a contiguous memory block that holds
+ * the serialized state of files.
+ */
+struct luo_session {
+ char name[LIVEUPDATE_SESSION_NAME_LENGTH];
+ struct xarray files_xa;
+ struct luo_session_ser *ser;
+ long count;
+ struct list_head list;
+ bool retrieved;
+ struct mutex mutex;
+ enum liveupdate_state state;
+ u64 files;
+};
+
+int luo_session_create(const char *name, struct file **filep);
+int luo_session_retrieve(const char *name, struct file **filep);
+
void luo_subsystems_startup(void *fdt);
int luo_subsystems_fdt_setup(void *fdt);
int luo_do_subsystems_prepare_calls(void);
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
new file mode 100644
index 000000000000..74dee42e24b7
--- /dev/null
+++ b/kernel/liveupdate/luo_session.c
@@ -0,0 +1,607 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+/**
+ * DOC: LUO Sessions
+ *
+ * LUO Sessions provide the core mechanism for grouping and managing file
+ * descriptors that need to be preserved across a kexec-based live update.
+ * Each session acts as a named container for a set of file objects, allowing
+ * a userspace agent (e.g., a Live Update Orchestration Daemon) to manage the
+ * lifecycle of resources critical to a workload.
+ *
+ * Core Concepts:
+ *
+ * - Named Containers: Sessions are identified by a unique, user-provided name,
+ * which is used for both creation and retrieval.
+ *
+ * - Userspace Interface: Session management is driven from userspace via
+ * ioctls on /dev/liveupdate (e.g., CREATE_SESSION, RETRIEVE_SESSION).
+ *
+ * - Serialization: Session metadata is preserved using the KHO framework.
+ * During the 'prepare' phase, an array of `struct luo_session_ser` is
+ * allocated and preserved. An FDT node is also created, containing the
+ * count of sessions and the physical address of this array.
+ *
+ * Session Lifecycle and State Management:
+ *
+ * 1. Creation: A userspace agent calls `luo_session_create()` to create a new,
+ * empty session, receiving a file descriptor handle. This can be done in
+ * the NORMAL or UPDATED states.
+ *
+ * 2. Name Collision: In the UPDATED state, `luo_session_create()` checks for
+ * name conflicts against sessions preserved from the previous kernel to
+ * prevent ambiguity.
+ *
+ * 3. Preparation (`prepare` callback): When the global LUO PREPARE event is
+ * triggered, the list of all created sessions is serialized. The main
+ * `ser` array is allocated, and each active `struct luo_session` is given
+ * a direct pointer to its corresponding entry in this array.
+ *
+ * 4. Release After Prepare: When a session FD is closed *after* the PREPARE
+ * event, the `.release` handler uses the session's direct pointer to
+ * `memset(0)` its entry in the `ser` array. This effectively marks the
+ * session as defunct without needing to resize the already-preserved
+ * memory.
+ *
+ * 5. Boot (`boot` callback): In the new kernel, the FDT is read to locate
+ * the preserved `ser` array. The metadata (count, physical address) is
+ * stored in the `luo_session` global.
+ *
+ * 6. Lazy Deserialization: The actual `luo_session` list is populated on
+ * first use (e.g., by `retrieve`, `finish`, or `create`). During this
+ * process, any zeroed-out entries from step 4 are skipped.
+ *
+ * 7. Retrieval: The userspace agent calls `luo_session_retrieve()` in the new
+ * kernel to get a new FD handle for a preserved session by its name.
+ *
+ * 8. Finalization (`finish` callback): When the global LUO FINISH event is
+ * sent, any preserved sessions that were successfully retrieved are moved
+ * to the `luo_session_global` list, making them available for a subsequent
+ * live update. Any sessions that were not retrieved are considered stale
+ * and are cleaned up.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/anon_inodes.h>
+#include <linux/errno.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/libfdt.h>
+#include <linux/liveupdate.h>
+#include <uapi/linux/liveupdate.h>
+#include "luo_internal.h"
+
+#define LUO_SESSION_NODE_NAME "luo-session"
+#define LUO_SESSION_COMPATIBLE "luo-session-v1"
+
+/**
+ * struct luo_session_ser - Represents the serialized metadata for a LUO session.
+ * @name: The unique name of the session, copied from the `luo_session`
+ * structure.
+ * @files: The physical address of a contiguous memory block that holds
+ * the serialized state of files.
+ * @pgcnt: The number of pages occupied by the `files` memory block.
+ * @count: The total number of files that were part of this session during
+ * serialization. Used for iteration and validation during
+ * restoration.
+ *
+ * This structure is used to package session-specific metadata for transfer
+ * between kernels via Kexec Handover. An array of these structures (one per
+ * session) is created and passed to the new kernel, allowing it to reconstruct
+ * the session context.
+ *
+ * If this structure is modified, LUO_SESSION_COMPATIBLE must be updated.
+ */
+struct luo_session_ser {
+ char name[LIVEUPDATE_SESSION_NAME_LENGTH];
+ u64 files;
+ u64 pgcnt;
+ u64 count;
+} __packed;
+
+/**
+ * struct luo_session_global - Global container 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.
+ * @ser: A pointer to the contiguous block of memory holding the serialized
+ * session data (an array of `struct luo_session_ser`). For `_out`, this
+ * is allocated and populated during `prepare`. For `_in`, this points
+ * to the data restored from the previous kernel.
+ * @pgcnt: The size, in pages, of the memory block pointed to by @ser.
+ * @fdt: A pointer to the FDT blob that contains the metadata for this group
+ * of sessions. This FDT is what is ultimately passed to the parent LUO
+ * subsystem for preservation.
+ */
+struct luo_session_global {
+ long count;
+ struct list_head list;
+ struct rw_semaphore rwsem;
+ struct luo_session_ser *ser;
+ u64 pgcnt;
+ void *fdt;
+ long ser_count;
+};
+
+static struct luo_session_global luo_session_global;
+
+static struct luo_session *luo_session_alloc(const char *name)
+{
+ struct luo_session *session = kzalloc(sizeof(*session), GFP_KERNEL);
+
+ if (!session)
+ return NULL;
+
+ strscpy(session->name, name, sizeof(session->name));
+ xa_init(&session->files_xa);
+ session->count = 0;
+ INIT_LIST_HEAD(&session->list);
+ mutex_init(&session->mutex);
+ session->state = LIVEUPDATE_STATE_NORMAL;
+
+ return session;
+}
+
+static void luo_session_free(struct luo_session *session)
+{
+ WARN_ON(session->count);
+ xa_destroy(&session->files_xa);
+ mutex_destroy(&session->mutex);
+ kfree(session);
+}
+
+static int luo_session_insert(struct luo_session *session)
+{
+ struct luo_session *it;
+
+ lockdep_assert_held_write(&luo_session_global.rwsem);
+ /*
+ * For small number of sessions this loop won't hurt performance
+ * but if we ever start using a lot of sessions, this might
+ * become a bottle neck during deserialization time, as it would
+ * cause O(n*n) complexity.
+ */
+ list_for_each_entry(it, &luo_session_global.list, list) {
+ if (!strncmp(it->name, session->name, sizeof(it->name)))
+ return -EEXIST;
+ }
+ list_add_tail(&session->list, &luo_session_global.list);
+ luo_session_global.count++;
+
+ return 0;
+}
+
+static void luo_session_remove(struct luo_session *session)
+{
+ lockdep_assert_held_write(&luo_session_global.rwsem);
+ list_del(&session->list);
+ luo_session_global.count--;
+}
+
+/* One session switches from the updated state to normal state */
+static void luo_session_finish_one(struct luo_session *session)
+{
+}
+
+/* Cancel one session from frozen or prepared state, back to normal */
+static void luo_session_cancel_one(struct luo_session *session)
+{
+}
+
+/* One session is changed from normal to prepare state */
+static int luo_session_prepare_one(struct luo_session *session)
+{
+ return 0;
+}
+
+static int luo_session_release(struct inode *inodep, struct file *filep)
+{
+ struct luo_session *session = filep->private_data;
+
+ scoped_guard(rwsem_read, &luo_session_global.rwsem) {
+ scoped_guard(mutex, &session->mutex) {
+ if (session->ser) {
+ memset(session->ser, 0,
+ sizeof(struct luo_session_ser));
+ }
+ }
+ }
+
+ if (session->state == LIVEUPDATE_STATE_UPDATED)
+ luo_session_finish_one(session);
+ if (session->state == LIVEUPDATE_STATE_PREPARED ||
+ session->state == LIVEUPDATE_STATE_FROZEN) {
+ luo_session_cancel_one(session);
+ }
+
+ scoped_guard(rwsem_write, &luo_session_global.rwsem)
+ luo_session_remove(session);
+ luo_session_free(session);
+
+ return 0;
+}
+
+static const struct file_operations luo_session_fops = {
+ .owner = THIS_MODULE,
+ .release = luo_session_release,
+};
+
+static void luo_session_deserialize(void)
+{
+ static int visited;
+ int i;
+
+ if (visited)
+ return;
+
+ guard(rwsem_write)(&luo_session_global.rwsem);
+ if (visited)
+ return;
+ visited++;
+ for (i = 0; i < luo_session_global.ser_count; i++) {
+ struct luo_session *session;
+
+ /*
+ * If there is no name, this session was remove from
+ * preservation after prepare. So, skip it.
+ */
+ if (!luo_session_global.ser[i].name[0])
+ continue;
+
+ session = luo_session_alloc(luo_session_global.ser[i].name);
+ if (!session)
+ luo_restore_fail("Failed to allocate session on boot\n");
+
+ if (luo_session_insert(session)) {
+ luo_restore_fail("Failed to insert session due to name conflict [%s]\n",
+ session->name);
+ }
+
+ session->state = LIVEUPDATE_STATE_UPDATED;
+ session->count = luo_session_global.ser[i].count;
+ session->files = luo_session_global.ser[i].files;
+ }
+}
+
+/* Create a "struct file" for session, and delete it on case of failure */
+static int luo_session_getfile(struct luo_session *session, struct file **filep)
+{
+ char name_buf[128];
+ struct file *file;
+
+ scoped_guard(mutex, &session->mutex) {
+ lockdep_assert_held(&session->mutex);
+ snprintf(name_buf, sizeof(name_buf), "[luo_session] %s",
+ session->name);
+ file = anon_inode_getfile(name_buf, &luo_session_fops, session,
+ O_RDWR);
+ }
+ if (IS_ERR(file)) {
+ scoped_guard(rwsem_write, &luo_session_global.rwsem)
+ luo_session_remove(session);
+ luo_session_free(session);
+ return PTR_ERR(file);
+ }
+
+ *filep = file;
+ return 0;
+}
+
+int luo_session_create(const char *name, struct file **filep)
+{
+ struct luo_session *session;
+ int ret;
+
+ guard(rwsem_read)(&luo_state_rwsem);
+
+ /* New sessions cannot be added after prepared state */
+ if (!liveupdate_state_normal() && !liveupdate_state_updated())
+ return -EAGAIN;
+
+ session = luo_session_alloc(name);
+ if (!session)
+ return -ENOMEM;
+
+ scoped_guard(rwsem_write, &luo_session_global.rwsem)
+ ret = luo_session_insert(session);
+ if (ret) {
+ luo_session_free(session);
+ return ret;
+ }
+
+ return luo_session_getfile(session, filep);
+}
+
+int luo_session_retrieve(const char *name, struct file **filep)
+{
+ struct luo_session *session = NULL;
+ struct luo_session *it;
+
+ guard(rwsem_read)(&luo_state_rwsem);
+
+ /* Can only retrieve in the updated state */
+ if (!liveupdate_state_updated())
+ return -EAGAIN;
+
+ luo_session_deserialize();
+ scoped_guard(rwsem_read, &luo_session_global.rwsem) {
+ list_for_each_entry(it, &luo_session_global.list, list) {
+ if (!strncmp(it->name, name, sizeof(it->name))) {
+ session = it;
+ break;
+ }
+ }
+ }
+
+ if (!session)
+ return -ENOENT;
+
+ scoped_guard(mutex, &session->mutex) {
+ /*
+ * Session already retrieved or a session with the same name was
+ * created during updated state
+ */
+ if (session->retrieved || session->state != LIVEUPDATE_STATE_UPDATED)
+ return -EADDRINUSE;
+
+ session->retrieved = true;
+ }
+
+ return luo_session_getfile(session, filep);
+}
+
+static void luo_session_global_preserved_cleanup(void)
+{
+ lockdep_assert_held_write(&luo_session_global.rwsem);
+ if (luo_session_global.ser && !IS_ERR(luo_session_global.ser)) {
+ luo_contig_free_unpreserve(luo_session_global.ser,
+ luo_session_global.pgcnt << PAGE_SHIFT);
+ }
+ if (luo_session_global.fdt && !IS_ERR(luo_session_global.fdt))
+ luo_contig_free_unpreserve(luo_session_global.fdt, PAGE_SIZE);
+
+ luo_session_global.fdt = NULL;
+ luo_session_global.ser = NULL;
+ luo_session_global.ser_count = 0;
+ luo_session_global.pgcnt = 0;
+}
+
+static int luo_session_fdt_setup(void)
+{
+ u64 ser_pa;
+ int ret;
+
+ lockdep_assert_held_write(&luo_session_global.rwsem);
+ luo_session_global.pgcnt = DIV_ROUND_UP(luo_session_global.count *
+ sizeof(struct luo_session_ser), PAGE_SIZE);
+
+ if (luo_session_global.pgcnt > 0) {
+ size_t ser_size = luo_session_global.pgcnt << PAGE_SHIFT;
+
+ luo_session_global.ser = luo_contig_alloc_preserve(ser_size);
+ if (IS_ERR(luo_session_global.ser)) {
+ ret = PTR_ERR(luo_session_global.ser);
+ goto exit_cleanup;
+ }
+ }
+
+ luo_session_global.fdt = luo_contig_alloc_preserve(PAGE_SIZE);
+ if (IS_ERR(luo_session_global.fdt)) {
+ ret = PTR_ERR(luo_session_global.fdt);
+ goto exit_cleanup;
+ }
+
+ ret = fdt_create(luo_session_global.fdt, PAGE_SIZE);
+ if (ret < 0)
+ goto exit_cleanup;
+
+ ret = fdt_finish_reservemap(luo_session_global.fdt);
+ if (ret < 0)
+ goto exit_finish;
+
+ ret = fdt_begin_node(luo_session_global.fdt, LUO_SESSION_NODE_NAME);
+ if (ret < 0)
+ goto exit_finish;
+
+ ret = fdt_property_string(luo_session_global.fdt, "compatible",
+ LUO_SESSION_COMPATIBLE);
+ if (ret < 0)
+ goto exit_end_node;
+
+ ret = fdt_property_u64(luo_session_global.fdt, "count",
+ luo_session_global.count);
+ if (ret < 0)
+ goto exit_end_node;
+
+ ser_pa = luo_session_global.ser ? __pa(luo_session_global.ser) : 0;
+ ret = fdt_property_u64(luo_session_global.fdt, "data", ser_pa);
+ if (ret < 0)
+ goto exit_end_node;
+
+ ret = fdt_property_u64(luo_session_global.fdt, "pgcnt",
+ luo_session_global.pgcnt);
+ if (ret < 0)
+ goto exit_end_node;
+
+ ret = fdt_end_node(luo_session_global.fdt);
+ if (ret < 0)
+ goto exit_finish;
+
+ ret = fdt_finish(luo_session_global.fdt);
+ if (ret < 0)
+ goto exit_cleanup;
+
+ return 0;
+
+exit_end_node:
+ fdt_end_node(luo_session_global.fdt);
+exit_finish:
+ fdt_finish(luo_session_global.fdt);
+exit_cleanup:
+ luo_session_global_preserved_cleanup();
+
+ return ret;
+}
+
+/*
+ * Change all sessions to normal state: make every file within each session
+ * to be in the normal state.
+ */
+static void luo_session_cancel(struct liveupdate_subsystem *h, u64 data)
+{
+ struct luo_session *it;
+
+ guard(rwsem_write)(&luo_session_global.rwsem);
+ list_for_each_entry(it, &luo_session_global.list, list)
+ luo_session_cancel_one(it);
+ luo_session_global_preserved_cleanup();
+}
+
+static int luo_session_prepare(struct liveupdate_subsystem *h, u64 *data)
+{
+ struct luo_session_ser *ser;
+ struct luo_session *it;
+ int ret;
+
+ scoped_guard(rwsem_write, &luo_session_global.rwsem) {
+ ret = luo_session_fdt_setup();
+ if (ret)
+ return ret;
+
+ ser = luo_session_global.ser;
+ list_for_each_entry(it, &luo_session_global.list, list) {
+ if (it->state == LIVEUPDATE_STATE_NORMAL) {
+ ret = luo_session_prepare_one(it);
+ if (ret)
+ break;
+ }
+ strscpy(ser->name, it->name, sizeof(ser->name));
+ ser->count = it->count;
+ ser->files = it->files;
+ it->ser = ser;
+ ser++;
+ }
+
+ if (!ret)
+ *data = __pa(luo_session_global.fdt);
+ }
+
+ if (ret)
+ luo_session_cancel(h, 0);
+
+ return ret;
+}
+
+static int luo_session_freeze(struct liveupdate_subsystem *h, u64 *data)
+{
+ return 0;
+}
+
+/*
+ * Finish every file within each session. If session has not been reclaimed
+ * remove it, otherwise keep this session, so it can participate in the
+ * next live update.
+ */
+static void luo_session_finish(struct liveupdate_subsystem *h, u64 data)
+{
+ struct luo_session *session, *tmp;
+
+ luo_session_deserialize();
+
+ list_for_each_entry_safe(session, tmp, &luo_session_global.list, list) {
+ /*
+ * Skip sessions that were created in new kernel or have been
+ * finished already.
+ */
+ if (session->state != LIVEUPDATE_STATE_UPDATED)
+ continue;
+ luo_session_finish_one(session);
+ if (!session->retrieved) {
+ pr_warn("Removing unreclaimed session[%s]\n",
+ session->name);
+ scoped_guard(rwsem_write, &luo_session_global.rwsem)
+ luo_session_remove(session);
+ luo_session_free(session);
+ }
+ }
+
+ scoped_guard(rwsem_write, &luo_session_global.rwsem)
+ luo_session_global_preserved_cleanup();
+}
+
+static void luo_session_boot(struct liveupdate_subsystem *h, u64 data)
+{
+ u64 count, data_pa, pgcnt;
+ const void *prop;
+ int prop_len;
+ void *fdt;
+
+ fdt = __va(data);
+ if (fdt_node_check_compatible(fdt, 0, LUO_SESSION_COMPATIBLE))
+ luo_restore_fail("luo-session FDT incompatible\n");
+
+ prop = fdt_getprop(fdt, 0, "count", &prop_len);
+ if (!prop || prop_len != sizeof(u64))
+ luo_restore_fail("luo-session FDT missing or invalid 'count'\n");
+ count = be64_to_cpup(prop);
+
+ prop = fdt_getprop(fdt, 0, "data", &prop_len);
+ if (!prop || prop_len != sizeof(u64))
+ luo_restore_fail("luo-session FDT missing or invalid 'data'\n");
+ data_pa = be64_to_cpup(prop);
+
+ prop = fdt_getprop(fdt, 0, "pgcnt", &prop_len);
+ if (!prop || prop_len != sizeof(u64))
+ luo_restore_fail("luo-session FDT missing or invalid 'pgcnt'\n");
+ pgcnt = be64_to_cpup(prop);
+
+ if (!count)
+ return;
+
+ guard(rwsem_write)(&luo_session_global.rwsem);
+ luo_session_global.fdt = fdt;
+ luo_session_global.ser = __va(data_pa);
+ luo_session_global.ser_count = count;
+ luo_session_global.pgcnt = pgcnt;
+}
+
+static const struct liveupdate_subsystem_ops luo_session_subsys_ops = {
+ .prepare = luo_session_prepare,
+ .freeze = luo_session_freeze,
+ .cancel = luo_session_cancel,
+ .boot = luo_session_boot,
+ .finish = luo_session_finish,
+ .owner = THIS_MODULE,
+};
+
+static struct liveupdate_subsystem luo_session_subsys = {
+ .ops = &luo_session_subsys_ops,
+ .name = LUO_SESSION_COMPATIBLE,
+};
+
+static int __init luo_session_startup(void)
+{
+ int ret;
+
+ if (!liveupdate_enabled())
+ return 0;
+
+ init_rwsem(&luo_session_global.rwsem);
+ INIT_LIST_HEAD(&luo_session_global.list);
+
+ ret = liveupdate_register_subsystem(&luo_session_subsys);
+ if (ret) {
+ pr_warn("Failed to register luo_session subsystem [%d]\n", ret);
+ return ret;
+ }
+
+ return ret;
+}
+late_initcall(luo_session_startup);
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 22/30] mm: shmem: allow freezing inode mapping
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
From: Pratyush Yadav <ptyadav@amazon.de>
To prepare a shmem inode for live update via the Live Update
Orchestrator (LUO), its index -> folio mappings must be serialized. Once
the mappings are serialized, they cannot change since it would cause the
serialized data to become inconsistent. This can be done by pinning the
folios to avoid migration, and by making sure no folios can be added to
or removed from the inode.
While mechanisms to pin folios already exist, the only way to stop
folios being added or removed are the grow and shrink file seals. But
file seals come with their own semantics, one of which is that they
can't be removed. This doesn't work with liveupdate since it can be
cancelled or error out, which would need the seals to be removed and the
file's normal functionality to be restored.
Introduce SHMEM_F_MAPPING_FROZEN to indicate this instead. It is
internal to shmem and is not directly exposed to userspace. It functions
similar to F_SEAL_GROW | F_SEAL_SHRINK, but additionally disallows hole
punching, and can be removed.
Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
Signed-off-by: Pasha Tatashin <pahsa.tatashin@soleen.com>
---
include/linux/shmem_fs.h | 17 +++++++++++++++++
mm/shmem.c | 12 +++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 650874b400b5..a9f5db472a39 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -24,6 +24,14 @@ struct swap_iocb;
#define SHMEM_F_NORESERVE BIT(0)
/* Disallow swapping. */
#define SHMEM_F_LOCKED BIT(1)
+/*
+ * Disallow growing, shrinking, or hole punching in the inode. Combined with
+ * folio pinning, makes sure the inode's mapping stays fixed.
+ *
+ * In some ways similar to F_SEAL_GROW | F_SEAL_SHRINK, but can be removed and
+ * isn't directly visible to userspace.
+ */
+#define SHMEM_F_MAPPING_FROZEN BIT(2)
struct shmem_inode_info {
spinlock_t lock;
@@ -186,6 +194,15 @@ static inline bool shmem_file(struct file *file)
return shmem_mapping(file->f_mapping);
}
+/* Must be called with inode lock taken exclusive. */
+static inline void shmem_i_mapping_freeze(struct inode *inode, bool freeze)
+{
+ if (freeze)
+ SHMEM_I(inode)->flags |= SHMEM_F_MAPPING_FROZEN;
+ else
+ SHMEM_I(inode)->flags &= ~SHMEM_F_MAPPING_FROZEN;
+}
+
/*
* If fallocate(FALLOC_FL_KEEP_SIZE) has been used, there may be pages
* beyond i_size's notion of EOF, which fallocate has committed to reserving:
diff --git a/mm/shmem.c b/mm/shmem.c
index ce3b912f62da..bd7d9afe5a27 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1292,7 +1292,8 @@ static int shmem_setattr(struct mnt_idmap *idmap,
loff_t newsize = attr->ia_size;
/* protected by i_rwsem */
- if ((newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
+ if ((info->flags & SHMEM_F_MAPPING_FROZEN) ||
+ (newsize < oldsize && (info->seals & F_SEAL_SHRINK)) ||
(newsize > oldsize && (info->seals & F_SEAL_GROW)))
return -EPERM;
@@ -3287,6 +3288,10 @@ shmem_write_begin(const struct kiocb *iocb, struct address_space *mapping,
return -EPERM;
}
+ if (unlikely((info->flags & SHMEM_F_MAPPING_FROZEN) &&
+ pos + len > inode->i_size))
+ return -EPERM;
+
ret = shmem_get_folio(inode, index, pos + len, &folio, SGP_WRITE);
if (ret)
return ret;
@@ -3660,6 +3665,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
inode_lock(inode);
+ if (info->flags & SHMEM_F_MAPPING_FROZEN) {
+ error = -EPERM;
+ goto out;
+ }
+
if (mode & FALLOC_FL_PUNCH_HOLE) {
struct address_space *mapping = file->f_mapping;
loff_t unmap_start = round_up(offset, PAGE_SIZE);
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 21/30] mm: shmem: use SHMEM_F_* flags instead of VM_* flags
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
From: Pratyush Yadav <ptyadav@amazon.de>
shmem_inode_info::flags can have the VM flags VM_NORESERVE and
VM_LOCKED. These are used to suppress pre-accounting or to lock the
pages in the inode respectively. Using the VM flags directly makes it
difficult to add shmem-specific flags that are unrelated to VM behavior
since one would need to find a VM flag not used by shmem and re-purpose
it.
Introduce SHMEM_F_NORESERVE and SHMEM_F_LOCKED which represent the same
information, but their bits are independent of the VM flags. Callers can
still pass VM_NORESERVE to shmem_get_inode(), but it gets transformed to
the shmem-specific flag internally.
No functional changes intended.
Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/shmem_fs.h | 6 ++++++
mm/shmem.c | 29 ++++++++++++++++-------------
2 files changed, 22 insertions(+), 13 deletions(-)
diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 0e47465ef0fd..650874b400b5 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -10,6 +10,7 @@
#include <linux/xattr.h>
#include <linux/fs_parser.h>
#include <linux/userfaultfd_k.h>
+#include <linux/bits.h>
struct swap_iocb;
@@ -19,6 +20,11 @@ struct swap_iocb;
#define SHMEM_MAXQUOTAS 2
#endif
+/* Suppress pre-accounting of the entire object size. */
+#define SHMEM_F_NORESERVE BIT(0)
+/* Disallow swapping. */
+#define SHMEM_F_LOCKED BIT(1)
+
struct shmem_inode_info {
spinlock_t lock;
unsigned int seals; /* shmem seals */
diff --git a/mm/shmem.c b/mm/shmem.c
index b9081b817d28..ce3b912f62da 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -175,20 +175,20 @@ static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
*/
static inline int shmem_acct_size(unsigned long flags, loff_t size)
{
- return (flags & VM_NORESERVE) ?
+ return (flags & SHMEM_F_NORESERVE) ?
0 : security_vm_enough_memory_mm(current->mm, VM_ACCT(size));
}
static inline void shmem_unacct_size(unsigned long flags, loff_t size)
{
- if (!(flags & VM_NORESERVE))
+ if (!(flags & SHMEM_F_NORESERVE))
vm_unacct_memory(VM_ACCT(size));
}
static inline int shmem_reacct_size(unsigned long flags,
loff_t oldsize, loff_t newsize)
{
- if (!(flags & VM_NORESERVE)) {
+ if (!(flags & SHMEM_F_NORESERVE)) {
if (VM_ACCT(newsize) > VM_ACCT(oldsize))
return security_vm_enough_memory_mm(current->mm,
VM_ACCT(newsize) - VM_ACCT(oldsize));
@@ -206,7 +206,7 @@ static inline int shmem_reacct_size(unsigned long flags,
*/
static inline int shmem_acct_blocks(unsigned long flags, long pages)
{
- if (!(flags & VM_NORESERVE))
+ if (!(flags & SHMEM_F_NORESERVE))
return 0;
return security_vm_enough_memory_mm(current->mm,
@@ -215,7 +215,7 @@ static inline int shmem_acct_blocks(unsigned long flags, long pages)
static inline void shmem_unacct_blocks(unsigned long flags, long pages)
{
- if (flags & VM_NORESERVE)
+ if (flags & SHMEM_F_NORESERVE)
vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
}
@@ -1551,7 +1551,7 @@ int shmem_writeout(struct folio *folio, struct swap_iocb **plug,
int nr_pages;
bool split = false;
- if ((info->flags & VM_LOCKED) || sbinfo->noswap)
+ if ((info->flags & SHMEM_F_LOCKED) || sbinfo->noswap)
goto redirty;
if (!total_swap_pages)
@@ -2907,15 +2907,15 @@ int shmem_lock(struct file *file, int lock, struct ucounts *ucounts)
* ipc_lock_object() when called from shmctl_do_lock(),
* no serialization needed when called from shm_destroy().
*/
- if (lock && !(info->flags & VM_LOCKED)) {
+ if (lock && !(info->flags & SHMEM_F_LOCKED)) {
if (!user_shm_lock(inode->i_size, ucounts))
goto out_nomem;
- info->flags |= VM_LOCKED;
+ info->flags |= SHMEM_F_LOCKED;
mapping_set_unevictable(file->f_mapping);
}
- if (!lock && (info->flags & VM_LOCKED) && ucounts) {
+ if (!lock && (info->flags & SHMEM_F_LOCKED) && ucounts) {
user_shm_unlock(inode->i_size, ucounts);
- info->flags &= ~VM_LOCKED;
+ info->flags &= ~SHMEM_F_LOCKED;
mapping_clear_unevictable(file->f_mapping);
}
retval = 0;
@@ -3059,7 +3059,8 @@ static struct inode *__shmem_get_inode(struct mnt_idmap *idmap,
spin_lock_init(&info->lock);
atomic_set(&info->stop_eviction, 0);
info->seals = F_SEAL_SEAL;
- info->flags = flags & VM_NORESERVE;
+ if (flags & VM_NORESERVE)
+ info->flags = SHMEM_F_NORESERVE;
info->i_crtime = inode_get_mtime(inode);
info->fsflags = (dir == NULL) ? 0 :
SHMEM_I(dir)->fsflags & SHMEM_FL_INHERITED;
@@ -5801,8 +5802,10 @@ static inline struct inode *shmem_get_inode(struct mnt_idmap *idmap,
/* common code */
static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name,
- loff_t size, unsigned long flags, unsigned int i_flags)
+ loff_t size, unsigned long vm_flags,
+ unsigned int i_flags)
{
+ unsigned long flags = (vm_flags & VM_NORESERVE) ? SHMEM_F_NORESERVE : 0;
struct inode *inode;
struct file *res;
@@ -5819,7 +5822,7 @@ static struct file *__shmem_file_setup(struct vfsmount *mnt, const char *name,
return ERR_PTR(-ENOMEM);
inode = shmem_get_inode(&nop_mnt_idmap, mnt->mnt_sb, NULL,
- S_IFREG | S_IRWXUGO, 0, flags);
+ S_IFREG | S_IRWXUGO, 0, vm_flags);
if (IS_ERR(inode)) {
shmem_unacct_size(flags, size);
return ERR_CAST(inode);
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 20/30] MAINTAINERS: add liveupdate entry
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Add a MAINTAINERS file entry for the new Live Update Orchestrator
introduced in previous patches.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
MAINTAINERS | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index e5c800ed4819..e99af6101d3c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14431,6 +14431,18 @@ F: kernel/module/livepatch.c
F: samples/livepatch/
F: tools/testing/selftests/livepatch/
+LIVE UPDATE
+M: Pasha Tatashin <pasha.tatashin@soleen.com>
+L: linux-kernel@vger.kernel.org
+S: Maintained
+F: Documentation/ABI/testing/sysfs-kernel-liveupdate
+F: Documentation/core-api/liveupdate.rst
+F: Documentation/userspace-api/liveupdate.rst
+F: include/linux/liveupdate.h
+F: include/uapi/linux/liveupdate.h
+F: kernel/liveupdate/
+F: tools/testing/selftests/liveupdate/
+
LLC (802.2)
L: netdev@vger.kernel.org
S: Odd fixes
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 19/30] docs: add luo documentation
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Add the documentation files for the Live Update Orchestrator
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
Documentation/core-api/index.rst | 1 +
Documentation/core-api/liveupdate.rst | 57 ++++++++++++++++++++++
Documentation/userspace-api/index.rst | 1 +
Documentation/userspace-api/liveupdate.rst | 25 ++++++++++
4 files changed, 84 insertions(+)
create mode 100644 Documentation/core-api/liveupdate.rst
create mode 100644 Documentation/userspace-api/liveupdate.rst
diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index 6cbdcbfa79c3..5eb0fbbbc323 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -138,6 +138,7 @@ Documents that don't fit elsewhere or which have yet to be categorized.
:maxdepth: 1
librs
+ liveupdate
netlink
.. only:: subproject and html
diff --git a/Documentation/core-api/liveupdate.rst b/Documentation/core-api/liveupdate.rst
new file mode 100644
index 000000000000..7c1c3af6f960
--- /dev/null
+++ b/Documentation/core-api/liveupdate.rst
@@ -0,0 +1,57 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+Live Update Orchestrator
+========================
+:Author: Pasha Tatashin <pasha.tatashin@soleen.com>
+
+.. kernel-doc:: kernel/liveupdate/luo_core.c
+ :doc: Live Update Orchestrator (LUO)
+
+LUO Subsystems Participation
+============================
+.. kernel-doc:: kernel/liveupdate/luo_subsystems.c
+ :doc: LUO Subsystems support
+
+LUO Sessions
+============
+.. kernel-doc:: kernel/liveupdate/luo_session.c
+ :doc: LUO Sessions
+
+LUO Preserving File Descriptors
+===============================
+.. kernel-doc:: kernel/liveupdate/luo_file.c
+ :doc: LUO file descriptors
+
+Public API
+==========
+.. kernel-doc:: include/linux/liveupdate.h
+
+.. kernel-doc:: kernel/liveupdate/luo_core.c
+ :export:
+
+.. kernel-doc:: kernel/liveupdate/luo_subsystems.c
+ :export:
+
+.. kernel-doc:: kernel/liveupdate/luo_file.c
+ :export:
+
+Internal API
+============
+.. kernel-doc:: kernel/liveupdate/luo_core.c
+ :internal:
+
+.. kernel-doc:: kernel/liveupdate/luo_subsystems.c
+ :internal:
+
+.. kernel-doc:: kernel/liveupdate/luo_session.c
+ :internal:
+
+.. kernel-doc:: kernel/liveupdate/luo_file.c
+ :internal:
+
+See Also
+========
+
+- :doc:`Live Update uAPI </userspace-api/liveupdate>`
+- :doc:`/core-api/kho/concepts`
diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst
index 0167e59b541e..64b0099ee161 100644
--- a/Documentation/userspace-api/index.rst
+++ b/Documentation/userspace-api/index.rst
@@ -61,6 +61,7 @@ Everything else
:maxdepth: 1
ELF
+ liveupdate
netlink/index
shadow_stack
sysfs-platform_profile
diff --git a/Documentation/userspace-api/liveupdate.rst b/Documentation/userspace-api/liveupdate.rst
new file mode 100644
index 000000000000..70b5017c0e3c
--- /dev/null
+++ b/Documentation/userspace-api/liveupdate.rst
@@ -0,0 +1,25 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+================
+Live Update uAPI
+================
+:Author: Pasha Tatashin <pasha.tatashin@soleen.com>
+
+ioctl interface
+===============
+.. kernel-doc:: kernel/liveupdate/luo_ioctl.c
+ :doc: LUO ioctl Interface
+
+ioctl uAPI
+===========
+.. kernel-doc:: include/uapi/linux/liveupdate.h
+
+LUO selftests ioctl
+===================
+.. kernel-doc:: kernel/liveupdate/luo_selftests.c
+ :doc: LUO Selftests
+
+See Also
+========
+
+- :doc:`Live Update Orchestrator </core-api/liveupdate>`
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 18/30] selftests/liveupdate: add subsystem/state tests
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Introduces a new set of userspace selftests for the LUO. These tests
verify the functionality LUO by using the kernel-side selftest ioctls
provided by the LUO module, primarily focusing on subsystem management
and basic LUO state transitions.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/liveupdate/.gitignore | 1 +
tools/testing/selftests/liveupdate/Makefile | 7 +
tools/testing/selftests/liveupdate/config | 6 +
.../testing/selftests/liveupdate/liveupdate.c | 348 ++++++++++++++++++
5 files changed, 363 insertions(+)
create mode 100644 tools/testing/selftests/liveupdate/.gitignore
create mode 100644 tools/testing/selftests/liveupdate/Makefile
create mode 100644 tools/testing/selftests/liveupdate/config
create mode 100644 tools/testing/selftests/liveupdate/liveupdate.c
diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index c46ebdb9b8ef..56e44a98d6a5 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -54,6 +54,7 @@ TARGETS += kvm
TARGETS += landlock
TARGETS += lib
TARGETS += livepatch
+TARGETS += liveupdate
TARGETS += lkdtm
TARGETS += lsm
TARGETS += membarrier
diff --git a/tools/testing/selftests/liveupdate/.gitignore b/tools/testing/selftests/liveupdate/.gitignore
new file mode 100644
index 000000000000..af6e773cf98f
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/.gitignore
@@ -0,0 +1 @@
+/liveupdate
diff --git a/tools/testing/selftests/liveupdate/Makefile b/tools/testing/selftests/liveupdate/Makefile
new file mode 100644
index 000000000000..2a573c36016e
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only
+CFLAGS += -Wall -O2 -Wno-unused-function
+CFLAGS += $(KHDR_INCLUDES)
+
+TEST_GEN_PROGS += liveupdate
+
+include ../lib.mk
diff --git a/tools/testing/selftests/liveupdate/config b/tools/testing/selftests/liveupdate/config
new file mode 100644
index 000000000000..382c85b89570
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/config
@@ -0,0 +1,6 @@
+CONFIG_KEXEC_FILE=y
+CONFIG_KEXEC_HANDOVER=y
+CONFIG_KEXEC_HANDOVER_DEBUG=y
+CONFIG_LIVEUPDATE=y
+CONFIG_LIVEUPDATE_SYSFS_API=y
+CONFIG_LIVEUPDATE_SELFTESTS=y
diff --git a/tools/testing/selftests/liveupdate/liveupdate.c b/tools/testing/selftests/liveupdate/liveupdate.c
new file mode 100644
index 000000000000..7c0ceaac0283
--- /dev/null
+++ b/tools/testing/selftests/liveupdate/liveupdate.c
@@ -0,0 +1,348 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+
+#include <linux/liveupdate.h>
+
+#include "../kselftest.h"
+#include "../kselftest_harness.h"
+#include "../../../../kernel/liveupdate/luo_selftests.h"
+
+struct subsystem_info {
+ void *data_page;
+ void *verify_page;
+ char test_name[LUO_NAME_LENGTH];
+ bool registered;
+};
+
+FIXTURE(subsystem) {
+ int fd;
+ int fd_dbg;
+ struct subsystem_info si[LUO_MAX_SUBSYSTEMS];
+};
+
+FIXTURE(state) {
+ int fd;
+ int fd_dbg;
+};
+
+#define LUO_DEVICE "/dev/liveupdate"
+#define LUO_DBG_DEVICE "/sys/kernel/debug/liveupdate/luo_selftest"
+static size_t page_size;
+
+const char *const luo_state_str[] = {
+ [LIVEUPDATE_STATE_UNDEFINED] = "undefined",
+ [LIVEUPDATE_STATE_NORMAL] = "normal",
+ [LIVEUPDATE_STATE_PREPARED] = "prepared",
+ [LIVEUPDATE_STATE_FROZEN] = "frozen",
+ [LIVEUPDATE_STATE_UPDATED] = "updated",
+};
+
+static int run_luo_selftest_cmd(int fd_dbg, __u64 cmd_code,
+ struct luo_arg_subsystem *subsys_arg)
+{
+ struct liveupdate_selftest k_arg;
+
+ k_arg.cmd = cmd_code;
+ k_arg.arg = (__u64)(unsigned long)subsys_arg;
+
+ return ioctl(fd_dbg, LIVEUPDATE_IOCTL_SELFTESTS, &k_arg);
+}
+
+static int register_subsystem(int fd_dbg, struct subsystem_info *si)
+{
+ struct luo_arg_subsystem subsys_arg;
+ int ret;
+
+ memset(&subsys_arg, 0, sizeof(subsys_arg));
+ snprintf(subsys_arg.name, LUO_NAME_LENGTH, "%s", si->test_name);
+ subsys_arg.data_page = si->data_page;
+
+ ret = run_luo_selftest_cmd(fd_dbg, LUO_CMD_SUBSYSTEM_REGISTER,
+ &subsys_arg);
+ if (!ret)
+ si->registered = true;
+
+ return ret;
+}
+
+static int unregister_subsystem(int fd_dbg, struct subsystem_info *si)
+{
+ struct luo_arg_subsystem subsys_arg;
+ int ret;
+
+ memset(&subsys_arg, 0, sizeof(subsys_arg));
+ snprintf(subsys_arg.name, LUO_NAME_LENGTH, "%s", si->test_name);
+
+ ret = run_luo_selftest_cmd(fd_dbg, LUO_CMD_SUBSYSTEM_UNREGISTER,
+ &subsys_arg);
+ if (!ret)
+ si->registered = false;
+
+ return ret;
+}
+
+FIXTURE_SETUP(state)
+{
+ page_size = sysconf(_SC_PAGE_SIZE);
+ self->fd = open(LUO_DEVICE, O_RDWR);
+ if (self->fd < 0)
+ SKIP(return, "open(%s) failed [%d]", LUO_DEVICE, errno);
+
+ self->fd_dbg = open(LUO_DBG_DEVICE, O_RDWR);
+ ASSERT_GE(self->fd_dbg, 0);
+}
+
+FIXTURE_TEARDOWN(state)
+{
+ struct liveupdate_ioctl_set_event cancel = {
+ .size = sizeof(cancel),
+ .event = LIVEUPDATE_CANCEL,
+ };
+ struct liveupdate_ioctl_get_state ligs = {.size = sizeof(ligs)};
+
+ ioctl(self->fd, LIVEUPDATE_IOCTL_GET_STATE, &ligs);
+ if (ligs.state != LIVEUPDATE_STATE_NORMAL)
+ ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &cancel);
+ close(self->fd);
+}
+
+FIXTURE_SETUP(subsystem)
+{
+ int i;
+
+ page_size = sysconf(_SC_PAGE_SIZE);
+ memset(&self->si, 0, sizeof(self->si));
+ self->fd = open(LUO_DEVICE, O_RDWR);
+ if (self->fd < 0)
+ SKIP(return, "open(%s) failed [%d]", LUO_DEVICE, errno);
+
+ self->fd_dbg = open(LUO_DBG_DEVICE, O_RDWR);
+ ASSERT_GE(self->fd_dbg, 0);
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++) {
+ snprintf(self->si[i].test_name, LUO_NAME_LENGTH,
+ NAME_NORMAL ".%d", i);
+
+ self->si[i].data_page = mmap(NULL, page_size,
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0);
+ ASSERT_NE(MAP_FAILED, self->si[i].data_page);
+ memset(self->si[i].data_page, 'A' + i, page_size);
+
+ self->si[i].verify_page = mmap(NULL, page_size,
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS,
+ -1, 0);
+ ASSERT_NE(MAP_FAILED, self->si[i].verify_page);
+ memset(self->si[i].verify_page, 0, page_size);
+ }
+}
+
+FIXTURE_TEARDOWN(subsystem)
+{
+ struct liveupdate_ioctl_set_event cancel = {
+ .size = sizeof(cancel),
+ .event = LIVEUPDATE_CANCEL,
+ };
+ enum liveupdate_state state = LIVEUPDATE_STATE_NORMAL;
+ int i;
+
+ ioctl(self->fd, LIVEUPDATE_IOCTL_GET_STATE, &state);
+ if (state != LIVEUPDATE_STATE_NORMAL)
+ ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &cancel);
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++) {
+ if (self->si[i].registered)
+ unregister_subsystem(self->fd_dbg, &self->si[i]);
+ munmap(self->si[i].data_page, page_size);
+ munmap(self->si[i].verify_page, page_size);
+ }
+
+ close(self->fd);
+}
+
+TEST_F(state, normal)
+{
+ struct liveupdate_ioctl_get_state ligs = {.size = sizeof(ligs)};
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_GET_STATE, &ligs));
+ ASSERT_EQ(ligs.state, LIVEUPDATE_STATE_NORMAL);
+}
+
+TEST_F(state, prepared)
+{
+ struct liveupdate_ioctl_get_state ligs = {.size = sizeof(ligs)};
+ struct liveupdate_ioctl_set_event prepare = {
+ .size = sizeof(prepare),
+ .event = LIVEUPDATE_PREPARE,
+ };
+ struct liveupdate_ioctl_set_event cancel = {
+ .size = sizeof(cancel),
+ .event = LIVEUPDATE_CANCEL,
+ };
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &prepare));
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_GET_STATE, &ligs));
+ ASSERT_EQ(ligs.state, LIVEUPDATE_STATE_PREPARED);
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &cancel));
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_GET_STATE, &ligs));
+ ASSERT_EQ(ligs.state, LIVEUPDATE_STATE_NORMAL);
+}
+
+TEST_F(state, sysfs_prepared)
+{
+ struct liveupdate_ioctl_set_event prepare = {
+ .size = sizeof(prepare),
+ .event = LIVEUPDATE_PREPARE,
+ };
+ struct liveupdate_ioctl_set_event cancel = {
+ .size = sizeof(cancel),
+ .event = LIVEUPDATE_CANCEL,
+ };
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &prepare));
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &cancel));
+}
+
+TEST_F(state, sysfs_frozen)
+{
+ struct liveupdate_ioctl_set_event prepare = {
+ .size = sizeof(prepare),
+ .event = LIVEUPDATE_PREPARE,
+ };
+ struct liveupdate_ioctl_set_event cancel = {
+ .size = sizeof(cancel),
+ .event = LIVEUPDATE_CANCEL,
+ };
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &prepare));
+ ASSERT_EQ(0, ioctl(self->fd_dbg, LIVEUPDATE_IOCTL_FREEZE, NULL));
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &cancel));
+}
+
+TEST_F(subsystem, register_unregister)
+{
+ ASSERT_EQ(0, register_subsystem(self->fd_dbg, &self->si[0]));
+ ASSERT_EQ(0, unregister_subsystem(self->fd_dbg, &self->si[0]));
+}
+
+TEST_F(subsystem, double_unregister)
+{
+ ASSERT_EQ(0, register_subsystem(self->fd_dbg, &self->si[0]));
+ ASSERT_EQ(0, unregister_subsystem(self->fd_dbg, &self->si[0]));
+ EXPECT_NE(0, unregister_subsystem(self->fd_dbg, &self->si[0]));
+ EXPECT_TRUE(errno == EINVAL || errno == ENOENT);
+}
+
+TEST_F(subsystem, register_unregister_many)
+{
+ int i;
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, register_subsystem(self->fd_dbg, &self->si[i]));
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, unregister_subsystem(self->fd_dbg, &self->si[i]));
+}
+
+TEST_F(subsystem, getdata_verify)
+{
+ struct liveupdate_ioctl_get_state ligs = {.size = sizeof(ligs), .state = 0};
+ struct liveupdate_ioctl_set_event prepare = {
+ .size = sizeof(prepare),
+ .event = LIVEUPDATE_PREPARE,
+ };
+ struct liveupdate_ioctl_set_event cancel = {
+ .size = sizeof(cancel),
+ .event = LIVEUPDATE_CANCEL,
+ };
+ int i;
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, register_subsystem(self->fd_dbg, &self->si[i]));
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &prepare));
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_GET_STATE, &ligs));
+ ASSERT_EQ(ligs.state, LIVEUPDATE_STATE_PREPARED);
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++) {
+ struct luo_arg_subsystem subsys_arg;
+
+ memset(&subsys_arg, 0, sizeof(subsys_arg));
+ snprintf(subsys_arg.name, LUO_NAME_LENGTH, "%s",
+ self->si[i].test_name);
+ subsys_arg.data_page = self->si[i].verify_page;
+
+ ASSERT_EQ(0, run_luo_selftest_cmd(self->fd_dbg,
+ LUO_CMD_SUBSYSTEM_GETDATA,
+ &subsys_arg));
+ ASSERT_EQ(0, memcmp(self->si[i].data_page,
+ self->si[i].verify_page,
+ page_size));
+ }
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &cancel));
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_GET_STATE, &ligs));
+ ASSERT_EQ(ligs.state, LIVEUPDATE_STATE_NORMAL);
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, unregister_subsystem(self->fd_dbg, &self->si[i]));
+}
+
+TEST_F(subsystem, prepare_fail)
+{
+ struct liveupdate_ioctl_set_event prepare = {
+ .size = sizeof(prepare),
+ .event = LIVEUPDATE_PREPARE,
+ };
+ struct liveupdate_ioctl_set_event cancel = {
+ .size = sizeof(cancel),
+ .event = LIVEUPDATE_CANCEL,
+ };
+ int i;
+
+ snprintf(self->si[LUO_MAX_SUBSYSTEMS - 1].test_name, LUO_NAME_LENGTH,
+ NAME_PREPARE_FAIL ".%d", LUO_MAX_SUBSYSTEMS - 1);
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, register_subsystem(self->fd_dbg, &self->si[i]));
+
+ ASSERT_EQ(-1, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &prepare));
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, unregister_subsystem(self->fd_dbg, &self->si[i]));
+
+ snprintf(self->si[LUO_MAX_SUBSYSTEMS - 1].test_name, LUO_NAME_LENGTH,
+ NAME_NORMAL ".%d", LUO_MAX_SUBSYSTEMS - 1);
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, register_subsystem(self->fd_dbg, &self->si[i]));
+
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &prepare));
+ ASSERT_EQ(0, ioctl(self->fd_dbg, LIVEUPDATE_IOCTL_FREEZE, NULL));
+ ASSERT_EQ(0, ioctl(self->fd, LIVEUPDATE_IOCTL_SET_EVENT, &cancel));
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++)
+ ASSERT_EQ(0, unregister_subsystem(self->fd_dbg, &self->si[i]));
+}
+
+TEST_HARNESS_MAIN
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 17/30] liveupdate: add selftests for subsystems un/registration
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Introduce a self-test mechanism for the LUO to allow verification of
core subsystem management functionality. This is primarily intended
for developers and system integrators validating the live update
feature.
The tests are enabled via the new Kconfig option
CONFIG_LIVEUPDATE_SELFTESTS (default 'n') and are triggered through
a new ioctl command, LIVEUPDATE_IOCTL_SELFTESTS, added to the
/dev/liveupdate device node.
This ioctl accepts commands defined in luo_selftests.h to:
- LUO_CMD_SUBSYSTEM_REGISTER: Creates and registers a dummy LUO
subsystem using the liveupdate_register_subsystem() function. It
allocates a data page and copies initial data from userspace.
- LUO_CMD_SUBSYSTEM_UNREGISTER: Unregisters the specified dummy
subsystem using the liveupdate_unregister_subsystem() function and
cleans up associated test resources.
- LUO_CMD_SUBSYSTEM_GETDATA: Copies the data page associated with a
registered test subsystem back to userspace, allowing verification of
data potentially modified or preserved by test callbacks.
This provides a way to test the fundamental registration and
unregistration flows within the LUO framework from userspace without
requiring a full live update sequence.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/Kconfig | 15 ++
kernel/liveupdate/Makefile | 1 +
kernel/liveupdate/luo_selftests.c | 345 ++++++++++++++++++++++++++++++
kernel/liveupdate/luo_selftests.h | 84 ++++++++
4 files changed, 445 insertions(+)
create mode 100644 kernel/liveupdate/luo_selftests.c
create mode 100644 kernel/liveupdate/luo_selftests.h
diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig
index f6b0bde188d9..8311c2593d32 100644
--- a/kernel/liveupdate/Kconfig
+++ b/kernel/liveupdate/Kconfig
@@ -29,6 +29,21 @@ config LIVEUPDATE
If unsure, say N.
+config LIVEUPDATE_SELFTESTS
+ bool "Live Update Orchestrator - self-tests"
+ depends on LIVEUPDATE
+ help
+ Say Y here to build self-tests for the LUO framework. When enabled,
+ these tests can be initiated via the ioctl interface to help verify
+ the core live update functionality.
+
+ This option is primarily intended for developers working on the
+ live update feature or for validation purposes during system
+ integration.
+
+ If you are unsure or are building a production kernel where size
+ or attack surface is a concern, say N.
+
config KEXEC_HANDOVER
bool "kexec handover"
depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
diff --git a/kernel/liveupdate/Makefile b/kernel/liveupdate/Makefile
index 282d36a18993..2df7dfdf45c1 100644
--- a/kernel/liveupdate/Makefile
+++ b/kernel/liveupdate/Makefile
@@ -11,3 +11,4 @@ obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
obj-$(CONFIG_LIVEUPDATE) += luo.o
+obj-$(CONFIG_LIVEUPDATE_SELFTESTS) += luo_selftests.o
diff --git a/kernel/liveupdate/luo_selftests.c b/kernel/liveupdate/luo_selftests.c
new file mode 100644
index 000000000000..a476b88468fa
--- /dev/null
+++ b/kernel/liveupdate/luo_selftests.c
@@ -0,0 +1,345 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+/**
+ * DOC: LUO Selftests
+ *
+ * We provide ioctl-based selftest interface for the LUO. It provides a
+ * mechanism to test core LUO functionality, particularly the registration,
+ * unregistration, and data handling aspects of LUO subsystems, without
+ * requiring a full live update event sequence.
+ *
+ * The tests are intended primarily for developers working on the LUO framework
+ * or for validation purposes during system integration. This functionality is
+ * conditionally compiled based on the `CONFIG_LIVEUPDATE_SELFTESTS` Kconfig
+ * option and should typically be disabled in production kernels.
+ *
+ * Interface:
+ * The selftests are accessed via the `/dev/liveupdate` character device using
+ * the `LIVEUPDATE_IOCTL_SELFTESTS` ioctl command. The argument to the ioctl
+ * is a pointer to a `struct liveupdate_selftest` structure (defined in
+ * `uapi/linux/liveupdate.h`), which contains:
+ * - `cmd`: The specific selftest command to execute (e.g.,
+ * `LUO_CMD_SUBSYSTEM_REGISTER`).
+ * - `arg`: A pointer to a command-specific argument structure. For subsystem
+ * tests, this points to a `struct luo_arg_subsystem` (defined in
+ * `luo_selftests.h`).
+ *
+ * Commands:
+ * - `LUO_CMD_SUBSYSTEM_REGISTER`:
+ * Registers a new dummy LUO subsystem. It allocates kernel memory for test
+ * data, copies initial data from the user-provided `data_page`, sets up
+ * simple logging callbacks, and calls the core
+ * `liveupdate_register_subsystem()`
+ * function. Requires `arg` pointing to `struct luo_arg_subsystem`.
+ * - `LUO_CMD_SUBSYSTEM_UNREGISTER`:
+ * Unregisters a previously registered dummy subsystem identified by `name`.
+ * It calls the core `liveupdate_unregister_subsystem()` function and then
+ * frees the associated kernel memory and internal tracking structures.
+ * Requires `arg` pointing to `struct luo_arg_subsystem` (only `name` used).
+ * - `LUO_CMD_SUBSYSTEM_GETDATA`:
+ * Copies the content of the kernel data page associated with the specified
+ * dummy subsystem (`name`) back to the user-provided `data_page`. This allows
+ * userspace to verify the state of the data after potential test operations.
+ * Requires `arg` pointing to `struct luo_arg_subsystem`.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/debugfs.h>
+#include <linux/errno.h>
+#include <linux/gfp.h>
+#include <linux/kexec_handover.h>
+#include <linux/liveupdate.h>
+#include <linux/mutex.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/liveupdate.h>
+#include "luo_internal.h"
+#include "luo_selftests.h"
+
+static struct luo_subsystems {
+ struct liveupdate_subsystem handle;
+ char name[LUO_NAME_LENGTH];
+ void *data;
+ bool in_use;
+ bool preserved;
+} luo_subsystems[LUO_MAX_SUBSYSTEMS];
+
+/* Only allow one selftest ioctl operation at a time */
+static DEFINE_MUTEX(luo_ioctl_mutex);
+
+static int luo_subsystem_prepare(struct liveupdate_subsystem *h, u64 *data)
+{
+ struct luo_subsystems *s = container_of(h, struct luo_subsystems,
+ handle);
+ unsigned long phys_addr = __pa(s->data);
+ int ret;
+
+ ret = kho_preserve_pages(phys_to_page(phys_addr), 1);
+ if (ret)
+ return ret;
+
+ s->preserved = true;
+ *data = phys_addr;
+ pr_info("Subsystem '%s' prepare data[%lx]\n",
+ s->name, phys_addr);
+
+ if (strstr(s->name, NAME_PREPARE_FAIL))
+ return -EAGAIN;
+
+ return 0;
+}
+
+static int luo_subsystem_freeze(struct liveupdate_subsystem *h, u64 *data)
+{
+ struct luo_subsystems *s = container_of(h, struct luo_subsystems,
+ handle);
+
+ pr_info("Subsystem '%s' freeze data[%llx]\n", s->name, *data);
+
+ return 0;
+}
+
+static void luo_subsystem_cancel(struct liveupdate_subsystem *h, u64 data)
+{
+ struct luo_subsystems *s = container_of(h, struct luo_subsystems,
+ handle);
+
+ pr_info("Subsystem '%s' canel data[%llx]\n", s->name, data);
+ s->preserved = false;
+ WARN_ON(kho_unpreserve_pages(phys_to_page(data), 1));
+}
+
+static void luo_subsystem_finish(struct liveupdate_subsystem *h, u64 data)
+{
+ struct luo_subsystems *s = container_of(h, struct luo_subsystems,
+ handle);
+
+ pr_info("Subsystem '%s' finish data[%llx]\n", s->name, data);
+}
+
+static const struct liveupdate_subsystem_ops luo_selftest_subsys_ops = {
+ .prepare = luo_subsystem_prepare,
+ .freeze = luo_subsystem_freeze,
+ .cancel = luo_subsystem_cancel,
+ .finish = luo_subsystem_finish,
+ .owner = THIS_MODULE,
+};
+
+static int luo_subsystem_idx(char *name)
+{
+ int i;
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++) {
+ if (luo_subsystems[i].in_use &&
+ !strcmp(luo_subsystems[i].name, name))
+ break;
+ }
+
+ if (i == LUO_MAX_SUBSYSTEMS) {
+ pr_warn("Subsystem with name '%s' is not registred\n", name);
+
+ return -EINVAL;
+ }
+
+ return i;
+}
+
+static void luo_put_and_free_subsystem(char *name)
+{
+ int i = luo_subsystem_idx(name);
+
+ if (i < 0)
+ return;
+
+ if (luo_subsystems[i].preserved)
+ kho_unpreserve_pages(virt_to_page(luo_subsystems[i].data), 1);
+ free_page((unsigned long)luo_subsystems[i].data);
+ luo_subsystems[i].in_use = false;
+ luo_subsystems[i].preserved = false;
+}
+
+static int luo_get_and_alloc_subsystem(char *name, void __user *data,
+ struct liveupdate_subsystem **hp)
+{
+ unsigned long page_addr, i;
+
+ page_addr = get_zeroed_page(GFP_KERNEL);
+ if (!page_addr) {
+ pr_warn("Failed to allocate memory for subsystem data\n");
+ return -ENOMEM;
+ }
+
+ if (copy_from_user((void *)page_addr, data, PAGE_SIZE)) {
+ free_page(page_addr);
+ return -EFAULT;
+ }
+
+ for (i = 0; i < LUO_MAX_SUBSYSTEMS; i++) {
+ if (!luo_subsystems[i].in_use)
+ break;
+ }
+
+ if (i == LUO_MAX_SUBSYSTEMS) {
+ pr_warn("Maximum number of subsystems registered\n");
+ free_page(page_addr);
+ return -ENOMEM;
+ }
+
+ luo_subsystems[i].in_use = true;
+ luo_subsystems[i].handle.ops = &luo_selftest_subsys_ops;
+ luo_subsystems[i].handle.name = luo_subsystems[i].name;
+ strscpy(luo_subsystems[i].name, name, LUO_NAME_LENGTH);
+ luo_subsystems[i].data = (void *)page_addr;
+
+ *hp = &luo_subsystems[i].handle;
+
+ return 0;
+}
+
+static int luo_cmd_subsystem_unregister(void __user *argp)
+{
+ struct luo_arg_subsystem arg;
+ int ret, i;
+
+ if (copy_from_user(&arg, argp, sizeof(arg)))
+ return -EFAULT;
+
+ i = luo_subsystem_idx(arg.name);
+ if (i < 0)
+ return i;
+
+ ret = liveupdate_unregister_subsystem(&luo_subsystems[i].handle);
+ if (ret)
+ return ret;
+
+ luo_put_and_free_subsystem(arg.name);
+
+ return 0;
+}
+
+static int luo_cmd_subsystem_register(void __user *argp)
+{
+ struct liveupdate_subsystem *h;
+ struct luo_arg_subsystem arg;
+ int ret;
+
+ if (copy_from_user(&arg, argp, sizeof(arg)))
+ return -EFAULT;
+
+ ret = luo_get_and_alloc_subsystem(arg.name,
+ (void __user *)arg.data_page, &h);
+ if (ret)
+ return ret;
+
+ ret = liveupdate_register_subsystem(h);
+ if (ret)
+ luo_put_and_free_subsystem(arg.name);
+
+ return ret;
+}
+
+static int luo_cmd_subsystem_getdata(void __user *argp)
+{
+ struct luo_arg_subsystem arg;
+ int i;
+
+ if (copy_from_user(&arg, argp, sizeof(arg)))
+ return -EFAULT;
+
+ i = luo_subsystem_idx(arg.name);
+ if (i < 0)
+ return i;
+
+ if (copy_to_user(arg.data_page, luo_subsystems[i].data,
+ PAGE_SIZE)) {
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
+static int luo_ioctl_selftests(void __user *argp)
+{
+ struct liveupdate_selftest luo_st;
+ void __user *cmd_argp;
+ int ret = 0;
+
+ if (copy_from_user(&luo_st, argp, sizeof(luo_st)))
+ return -EFAULT;
+
+ cmd_argp = (void __user *)luo_st.arg;
+
+ mutex_lock(&luo_ioctl_mutex);
+ switch (luo_st.cmd) {
+ case LUO_CMD_SUBSYSTEM_REGISTER:
+ ret = luo_cmd_subsystem_register(cmd_argp);
+ break;
+
+ case LUO_CMD_SUBSYSTEM_UNREGISTER:
+ ret = luo_cmd_subsystem_unregister(cmd_argp);
+ break;
+
+ case LUO_CMD_SUBSYSTEM_GETDATA:
+ ret = luo_cmd_subsystem_getdata(cmd_argp);
+ break;
+
+ default:
+ pr_warn("ioctl: unknown self-test command nr: 0x%llx\n",
+ luo_st.cmd);
+ ret = -ENOTTY;
+ break;
+ }
+ mutex_unlock(&luo_ioctl_mutex);
+
+ return ret;
+}
+
+static long luo_selftest_ioctl(struct file *filep, unsigned int cmd,
+ unsigned long arg)
+{
+ int ret = 0;
+
+ if (_IOC_TYPE(cmd) != LIVEUPDATE_IOCTL_TYPE)
+ return -ENOTTY;
+
+ switch (cmd) {
+ case LIVEUPDATE_IOCTL_FREEZE:
+ ret = luo_freeze();
+ break;
+
+ case LIVEUPDATE_IOCTL_SELFTESTS:
+ ret = luo_ioctl_selftests((void __user *)arg);
+ break;
+
+ default:
+ pr_warn("ioctl: unknown command nr: 0x%x\n", _IOC_NR(cmd));
+ ret = -ENOTTY;
+ break;
+ }
+
+ return ret;
+}
+
+static const struct file_operations luo_selftest_fops = {
+ .open = nonseekable_open,
+ .unlocked_ioctl = luo_selftest_ioctl,
+};
+
+static int __init luo_seltesttest_init(void)
+{
+ if (!liveupdate_debugfs_root) {
+ pr_err("liveupdate root is not set\n");
+ return 0;
+ }
+ debugfs_create_file_unsafe("luo_selftest", 0600,
+ liveupdate_debugfs_root, NULL,
+ &luo_selftest_fops);
+ return 0;
+}
+
+late_initcall(luo_seltesttest_init);
diff --git a/kernel/liveupdate/luo_selftests.h b/kernel/liveupdate/luo_selftests.h
new file mode 100644
index 000000000000..098f2e9e6a78
--- /dev/null
+++ b/kernel/liveupdate/luo_selftests.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#ifndef _LINUX_LUO_SELFTESTS_H
+#define _LINUX_LUO_SELFTESTS_H
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+/* Maximum number of subsystem self-test can register */
+#define LUO_MAX_SUBSYSTEMS 16
+#define LUO_NAME_LENGTH 32
+
+#define LUO_CMD_SUBSYSTEM_REGISTER 0
+#define LUO_CMD_SUBSYSTEM_UNREGISTER 1
+#define LUO_CMD_SUBSYSTEM_GETDATA 2
+struct luo_arg_subsystem {
+ char name[LUO_NAME_LENGTH];
+ void *data_page;
+};
+
+/*
+ * Test name prefixes:
+ * normal: prepare and freeze callbacks do not fail
+ * prepare_fail: prepare callback fails for this test.
+ * freeze_fail: freeze callback fails for this test
+ */
+#define NAME_NORMAL "ksft_luo"
+#define NAME_PREPARE_FAIL "ksft_prepare_fail"
+#define NAME_FREEZE_FAIL "ksft_freeze_fail"
+
+/**
+ * struct liveupdate_selftest - Holds directions for the self-test operations.
+ * @cmd: Selftest comman defined in luo_selftests.h.
+ * @arg: Argument for the self test command.
+ *
+ * This structure is used only for the selftest purposes.
+ */
+struct liveupdate_selftest {
+ __u64 cmd;
+ __u64 arg;
+};
+
+/**
+ * LIVEUPDATE_IOCTL_FREEZE - Notify subsystems of imminent reboot
+ * transition.
+ *
+ * Argument: None.
+ *
+ * Notifies the live update subsystem and associated components that the kernel
+ * is about to execute the final reboot transition into the new kernel (e.g.,
+ * via kexec). This action triggers the internal %LIVEUPDATE_FREEZE kernel
+ * event. This event provides subsystems a final, brief opportunity (within the
+ * "blackout window") to save critical state or perform last-moment quiescing.
+ * Any remaining or deferred state saving for items marked via the PRESERVE
+ * ioctls typically occurs in response to the %LIVEUPDATE_FREEZE event.
+ *
+ * This ioctl should only be called when the system is in the
+ * %LIVEUPDATE_STATE_PREPARED state. This command does not transfer data.
+ *
+ * Return: 0 if the notification is successfully processed by the kernel (but
+ * reboot follows). Returns a negative error code if the notification fails
+ * or if the system is not in the %LIVEUPDATE_STATE_PREPARED state.
+ */
+#define LIVEUPDATE_IOCTL_FREEZE \
+ _IO(LIVEUPDATE_IOCTL_TYPE, 0x05)
+
+/**
+ * LIVEUPDATE_IOCTL_SELFTESTS - Interface for the LUO selftests
+ *
+ * Argument: Pointer to &struct liveupdate_selftest.
+ *
+ * Use by LUO selftests, commands are declared in luo_selftests.h
+ *
+ * Return: 0 on success, negative error code on failure (e.g., invalid token).
+ */
+#define LIVEUPDATE_IOCTL_SELFTESTS \
+ _IOWR(LIVEUPDATE_IOCTL_TYPE, 0x08, struct liveupdate_selftest)
+
+#endif /* _LINUX_LUO_SELFTESTS_H */
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 16/30] kho: move kho debugfs directory to liveupdate
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Now, that LUO and KHO both live under kernel/liveupdate, it makes
sense to also move the kho debugfs files to liveupdate/
The old names:
/sys/kernel/debug/kho/out/
/sys/kernel/debug/kho/in/
The new names:
/sys/kernel/debug/liveupdate/kho_out/
/sys/kernel/debug/liveupdate/kho_in/
Also, export the liveupdate_debufs_root, so LUO selftests could use
it as well.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/kexec_handover_debug.c | 11 ++++++-----
kernel/liveupdate/luo_internal.h | 4 ++++
2 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/kernel/liveupdate/kexec_handover_debug.c b/kernel/liveupdate/kexec_handover_debug.c
index af4bad225630..f06d6cdfeab3 100644
--- a/kernel/liveupdate/kexec_handover_debug.c
+++ b/kernel/liveupdate/kexec_handover_debug.c
@@ -14,8 +14,9 @@
#include <linux/libfdt.h>
#include <linux/mm.h>
#include "kexec_handover_internal.h"
+#include "luo_internal.h"
-static struct dentry *debugfs_root;
+struct dentry *liveupdate_debugfs_root;
struct fdt_debugfs {
struct list_head list;
@@ -120,7 +121,7 @@ __init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
INIT_LIST_HEAD(&dbg->fdt_list);
- dir = debugfs_create_dir("in", debugfs_root);
+ dir = debugfs_create_dir("in", liveupdate_debugfs_root);
if (IS_ERR(dir)) {
err = PTR_ERR(dir);
goto err_out;
@@ -180,7 +181,7 @@ __init int kho_out_debugfs_init(struct kho_debugfs *dbg)
INIT_LIST_HEAD(&dbg->fdt_list);
- dir = debugfs_create_dir("out", debugfs_root);
+ dir = debugfs_create_dir("out", liveupdate_debugfs_root);
if (IS_ERR(dir))
return -ENOMEM;
@@ -214,8 +215,8 @@ __init int kho_out_debugfs_init(struct kho_debugfs *dbg)
__init int kho_debugfs_init(void)
{
- debugfs_root = debugfs_create_dir("kho", NULL);
- if (IS_ERR(debugfs_root))
+ liveupdate_debugfs_root = debugfs_create_dir("liveupdate", NULL);
+ if (IS_ERR(liveupdate_debugfs_root))
return -ENOENT;
return 0;
}
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index c9bce82aac22..083b80754c9e 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -107,4 +107,8 @@ void luo_file_finish(struct luo_session *session);
void luo_file_cancel(struct luo_session *session);
void luo_file_deserialize(struct luo_session *session);
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
+extern struct dentry *liveupdate_debugfs_root;
+#endif
+
#endif /* _LINUX_LUO_INTERNAL_H */
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 15/30] reboot: call liveupdate_reboot() before kexec
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Modify the reboot() syscall handler in kernel/reboot.c to call
liveupdate_reboot() when processing the LINUX_REBOOT_CMD_KEXEC
command.
This ensures that the Live Update Orchestrator is notified just
before the kernel executes the kexec jump. The liveupdate_reboot()
function triggers the final LIVEUPDATE_FREEZE event, allowing
participating subsystems to perform last-minute state saving within
the blackout window, and transitions the LUO state machine to FROZEN.
The call is placed immediately before kernel_kexec() to ensure LUO
finalization happens at the latest possible moment before the kernel
transition.
If liveupdate_reboot() returns an error (indicating a failure during
LUO finalization), the kexec operation is aborted to prevent proceeding
with an inconsistent state.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/reboot.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/reboot.c b/kernel/reboot.c
index ec087827c85c..bdeb04a773db 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -13,6 +13,7 @@
#include <linux/kexec.h>
#include <linux/kmod.h>
#include <linux/kmsg_dump.h>
+#include <linux/liveupdate.h>
#include <linux/reboot.h>
#include <linux/suspend.h>
#include <linux/syscalls.h>
@@ -797,6 +798,9 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
#ifdef CONFIG_KEXEC_CORE
case LINUX_REBOOT_CMD_KEXEC:
+ ret = liveupdate_reboot();
+ if (ret)
+ break;
ret = kernel_kexec();
break;
#endif
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 14/30] liveupdate: luo_session: Add ioctls for file preservation and state management
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Introducing the userspace interface and internal logic required to
manage the lifecycle of file descriptors within a session. Previously, a
session was merely a container; this change makes it a functional
management unit.
The following capabilities are added:
A new set of ioctl commands are added, which operate on the file
descriptor returned by CREATE_SESSION. This allows userspace to:
- LIVEUPDATE_SESSION_PRESERVE_FD: Add a file descriptor to a session
to be preserved across the live update.
- LIVEUPDATE_SESSION_UNPRESERVE_FD: Remove a previously added file
descriptor from the session.
- LIVEUPDATE_SESSION_RESTORE_FD: Retrieve a preserved file in the
new kernel using its unique token.
A state machine for each individual session, distinct from the global
LUO state. This enables more granular control, allowing userspace to
prepare or freeze specific sessions independently. This is managed via:
- LIVEUPDATE_SESSION_SET_EVENT: An ioctl to send PREPARE, FREEZE,
CANCEL, or FINISH events to a single session.
- LIVEUPDATE_SESSION_GET_STATE: An ioctl to query the current state
of a single session.
The global subsystem callbacks (luo_session_prepare, luo_session_freeze)
are updated to iterate through all existing sessions. They now trigger
the appropriate per-session state transitions for any sessions that
haven't already been transitioned individually by userspace.
The session's .release handler is enhanced to be state-aware. When a
session's file descriptor is closed, it now correctly cancels or
finishes the session based on its current state before freeing all
associated file resources, preventing resource leaks.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/uapi/linux/liveupdate.h | 164 ++++++++++++++++++
kernel/liveupdate/luo_session.c | 284 +++++++++++++++++++++++++++++++-
2 files changed, 446 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h
index 2e38ef3094aa..59a0f561d148 100644
--- a/include/uapi/linux/liveupdate.h
+++ b/include/uapi/linux/liveupdate.h
@@ -132,6 +132,16 @@ enum {
LIVEUPDATE_CMD_RETRIEVE_SESSION = 0x03,
};
+/* ioctl commands for session file descriptors */
+enum {
+ LIVEUPDATE_CMD_SESSION_BASE = 0x40,
+ LIVEUPDATE_CMD_SESSION_PRESERVE_FD = LIVEUPDATE_CMD_SESSION_BASE,
+ LIVEUPDATE_CMD_SESSION_UNPRESERVE_FD = 0x41,
+ LIVEUPDATE_CMD_SESSION_RESTORE_FD = 0x42,
+ LIVEUPDATE_CMD_SESSION_GET_STATE = 0x43,
+ LIVEUPDATE_CMD_SESSION_SET_EVENT = 0x44,
+};
+
/**
* struct liveupdate_ioctl_get_state - ioctl(LIVEUPDATE_IOCTL_GET_STATE)
* @size: Input; sizeof(struct liveupdate_ioctl_get_state)
@@ -293,4 +303,158 @@ struct liveupdate_ioctl_retrieve_session {
#define LIVEUPDATE_IOCTL_RETRIEVE_SESSION \
_IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_RETRIEVE_SESSION)
+
+/* Session specific IOCTLs */
+
+/**
+ * struct liveupdate_session_preserve_fd - ioctl(LIVEUPDATE_SESSION_PRESERVE_FD)
+ * @size: Input; sizeof(struct liveupdate_session_preserve_fd)
+ * @fd: Input; The user-space file descriptor to be preserved.
+ * @token: Input; An opaque, unique token for preserved resource.
+ *
+ * Holds parameters for preserving Validate and initiate preservation for a file
+ * descriptor.
+ *
+ * User sets the @fd field identifying the file descriptor to preserve
+ * (e.g., memfd, kvm, iommufd, VFIO). The kernel validates if this FD type
+ * and its dependencies are supported for preservation. If validation passes,
+ * the kernel marks the FD internally and *initiates the process* of preparing
+ * its state for saving. The actual snapshotting of the state typically occurs
+ * during the subsequent %LIVEUPDATE_IOCTL_PREPARE execution phase, though
+ * some finalization might occur during freeze.
+ * On successful validation and initiation, the kernel uses the @token
+ * field with an opaque identifier representing the resource being preserved.
+ * This token confirms the FD is targeted for preservation and is required for
+ * the subsequent %LIVEUPDATE_SESSION_RESTORE_FD call after the live update.
+ *
+ * Return: 0 on success (validation passed, preservation initiated), negative
+ * error code on failure (e.g., unsupported FD type, dependency issue,
+ * validation failed).
+ */
+struct liveupdate_session_preserve_fd {
+ __u32 size;
+ __s32 fd;
+ __aligned_u64 token;
+};
+
+#define LIVEUPDATE_SESSION_PRESERVE_FD \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_PRESERVE_FD)
+
+/**
+ * struct liveupdate_session_unpreserve_FD - ioctl(LIVEUPDATE_SESSION_UNPRESERVE_FD)
+ * @size: Input; sizeof(struct liveupdate_session_unpreserve_fd)
+ * @reserved: Must be zero.
+ * @token: Input; A token for resource to be unpreserved.
+ *
+ * Remove a file descriptor from the preservation list.
+ *
+ * Allows user space to explicitly remove a file descriptor from the set of
+ * items marked as potentially preservable. User space provides a @token that
+ * was previously used by a successful %LIVEUPDATE_SESSION_PRESERVE_FD call
+ * (potentially from a prior, possibly canceled, live update attempt). The
+ * kernel reads the token value from the provided user-space address.
+ *
+ * On success, the kernel removes the corresponding entry (identified by the
+ * token value read from the user pointer) from its internal preservation list.
+ * The provided @token (representing the now-removed entry) becomes invalid
+ * after this call.
+ *
+ * Return: 0 on success, negative error code on failure (e.g., -EBUSY or -EINVAL
+ * if bad address provided, invalid token value read, token not found).
+ */
+struct liveupdate_session_unpreserve_fd {
+ __u32 size;
+ __u32 reserved;
+ __aligned_u64 token;
+};
+
+#define LIVEUPDATE_SESSION_UNPRESERVE_FD \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_UNPRESERVE_FD)
+
+/**
+ * struct liveupdate_session_restore_fd - ioctl(LIVEUPDATE_SESSION_RESTORE_FD)
+ * @size: Input; sizeof(struct liveupdate_session_restore_fd)
+ * @fd: Output; The new file descriptor representing the fully restored
+ * kernel resource.
+ * @token: Input; An opaque, token that was used to preserve the resource.
+ *
+ * Restore a previously preserved file descriptor.
+ *
+ * User sets the @token field to the value obtained from a successful
+ * %LIVEUPDATE_IOCTL_FD_PRESERVE call before the live update. On success,
+ * the kernel restores the state (saved during the PREPARE/FREEZE phases)
+ * associated with the token and populates the @fd field with a new file
+ * descriptor referencing the restored resource in the current (new) kernel.
+ * This operation must be performed *before* signaling completion via
+ * %LIVEUPDATE_IOCTL_FINISH.
+ *
+ * Return: 0 on success, negative error code on failure (e.g., invalid token).
+ */
+struct liveupdate_session_restore_fd {
+ __u32 size;
+ __s32 fd;
+ __aligned_u64 token;
+};
+
+#define LIVEUPDATE_SESSION_RESTORE_FD \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_RESTORE_FD)
+
+/**
+ * struct liveupdate_session_get_state - ioctl(LIVEUPDATE_SESSION_GET_STATE)
+ * @size: Input; sizeof(struct liveupdate_session_get_state)
+ * @incoming: Input; If 1, query the state of a restored file from the incoming
+ * (previous kernel's) set. If 0, query a file being prepared for
+ * preservation in the current set.
+ * @reserved: Must be zero.
+ * @state: Output; The live update state of this FD.
+ *
+ * Query the current live update state of a specific preserved file descriptor.
+ *
+ * - %LIVEUPDATE_STATE_NORMAL: Default state
+ * - %LIVEUPDATE_STATE_PREPARED: Prepare callback has been performed on this FD.
+ * - %LIVEUPDATE_STATE_FROZEN: Freeze callback ahs been performed on this FD.
+ * - %LIVEUPDATE_STATE_UPDATED: The system has successfully rebooted into the
+ * new kernel.
+ *
+ * See the definition of &enum liveupdate_state for more details on each state.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+struct liveupdate_session_get_state {
+ __u32 size;
+ __u8 incoming;
+ __u8 reserved[3];
+ __u32 state;
+};
+
+#define LIVEUPDATE_SESSION_GET_STATE \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_GET_STATE)
+
+/**
+ * struct liveupdate_session_set_event - ioctl(LIVEUPDATE_SESSION_SET_EVENT)
+ * @size: Input; sizeof(struct liveupdate_session_set_event)
+ * @event: Input; The live update event.
+ *
+ * Notify a specific preserved file descriptor of an event, that causes a state
+ * transition for that file descriptor.
+ *
+ * Event, can be one of the following:
+ *
+ * - %LIVEUPDATE_PREPARE: Initiates the FD live update preparation phase.
+ * - %LIVEUPDATE_FREEZE: Initiates the FD live update freeze phase.
+ * - %LIVEUPDATE_CANCEL: Cancel the FD preparation or freeze phase.
+ * - %LIVEUPDATE_FINISH: FD Restoration completion and trigger cleanup.
+ *
+ * See the definition of &enum liveupdate_event for more details on each state.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+struct liveupdate_session_set_event {
+ __u32 size;
+ __u32 event;
+};
+
+#define LIVEUPDATE_SESSION_SET_EVENT \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SESSION_SET_EVENT)
+
#endif /* _UAPI_LIVEUPDATE_H */
diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
index 74dee42e24b7..966b68532d79 100644
--- a/kernel/liveupdate/luo_session.c
+++ b/kernel/liveupdate/luo_session.c
@@ -188,17 +188,66 @@ static void luo_session_remove(struct luo_session *session)
/* One session switches from the updated state to normal state */
static void luo_session_finish_one(struct luo_session *session)
{
+ scoped_guard(mutex, &session->mutex) {
+ if (session->state != LIVEUPDATE_STATE_UPDATED)
+ return;
+ luo_file_finish(session);
+ session->files = 0;
+ luo_file_unpreserve_unreclaimed_files(session);
+ session->state = LIVEUPDATE_STATE_NORMAL;
+ }
}
/* Cancel one session from frozen or prepared state, back to normal */
static void luo_session_cancel_one(struct luo_session *session)
{
+ guard(mutex)(&session->mutex);
+ if (session->state == LIVEUPDATE_STATE_FROZEN ||
+ session->state == LIVEUPDATE_STATE_PREPARED) {
+ luo_file_cancel(session);
+ session->state = LIVEUPDATE_STATE_NORMAL;
+ session->files = 0;
+ session->ser = NULL;
+ }
}
/* One session is changed from normal to prepare state */
static int luo_session_prepare_one(struct luo_session *session)
{
- return 0;
+ int ret;
+
+ guard(mutex)(&session->mutex);
+ if (session->state != LIVEUPDATE_STATE_NORMAL)
+ return -EBUSY;
+
+ ret = luo_file_prepare(session);
+ if (!ret)
+ session->state = LIVEUPDATE_STATE_PREPARED;
+
+ return ret;
+}
+
+/* One session is changed from prepared to frozen state */
+static int luo_session_freeze_one(struct luo_session *session)
+{
+ int ret;
+
+ guard(mutex)(&session->mutex);
+ if (session->state != LIVEUPDATE_STATE_PREPARED)
+ return -EBUSY;
+
+ ret = luo_file_freeze(session);
+
+ /*
+ * If fail, freeze is cancel, and as a side effect, we go back to normal
+ * state
+ */
+ if (!ret)
+ session->state = LIVEUPDATE_STATE_FROZEN;
+ else
+ session->state = LIVEUPDATE_STATE_NORMAL;
+
+ return ret;
}
static int luo_session_release(struct inode *inodep, struct file *filep)
@@ -220,6 +269,8 @@ static int luo_session_release(struct inode *inodep, struct file *filep)
session->state == LIVEUPDATE_STATE_FROZEN) {
luo_session_cancel_one(session);
}
+ scoped_guard(mutex, &session->mutex)
+ luo_file_unpreserve_all_files(session);
scoped_guard(rwsem_write, &luo_session_global.rwsem)
luo_session_remove(session);
@@ -228,9 +279,219 @@ static int luo_session_release(struct inode *inodep, struct file *filep)
return 0;
}
+static int luo_session_preserve_fd(struct luo_session *session,
+ struct luo_ucmd *ucmd)
+{
+ struct liveupdate_session_preserve_fd *argp = ucmd->cmd;
+ int ret;
+
+ guard(rwsem_read)(&luo_state_rwsem);
+ if (!liveupdate_state_normal() && !liveupdate_state_updated()) {
+ pr_warn("File can be preserved only in normal or updated state\n");
+ return -EBUSY;
+ }
+
+ guard(mutex)(&session->mutex);
+
+ if (session->state != LIVEUPDATE_STATE_NORMAL)
+ return -EBUSY;
+
+ ret = luo_preserve_file(session, argp->token, argp->fd);
+ if (ret)
+ return ret;
+
+ ret = luo_ucmd_respond(ucmd, sizeof(*argp));
+ if (ret)
+ pr_warn("The file was successfully preserved, but response to user failed\n");
+
+ return ret;
+}
+
+static int luo_session_unpreserve_fd(struct luo_session *session,
+ struct luo_ucmd *ucmd)
+{
+ struct liveupdate_session_unpreserve_fd *argp = ucmd->cmd;
+ int ret;
+
+ if (argp->reserved)
+ return -EOPNOTSUPP;
+
+ guard(rwsem_read)(&luo_state_rwsem);
+ if (!liveupdate_state_normal() && !liveupdate_state_updated()) {
+ pr_warn("File can be preserved only in normal or updated state\n");
+ return -EBUSY;
+ }
+
+ guard(mutex)(&session->mutex);
+
+ if (session->state != LIVEUPDATE_STATE_NORMAL)
+ return -EBUSY;
+
+ ret = luo_unpreserve_file(session, argp->token);
+ if (ret)
+ return ret;
+
+ ret = luo_ucmd_respond(ucmd, sizeof(*argp));
+ if (ret)
+ pr_warn("The file was successfully unpreserved, but response to user failed\n");
+
+ return ret;
+}
+
+static int luo_session_restore_fd(struct luo_session *session,
+ struct luo_ucmd *ucmd)
+{
+ struct liveupdate_session_restore_fd *argp = ucmd->cmd;
+ struct file *file;
+ int ret;
+
+ guard(rwsem_read)(&luo_state_rwsem);
+ if (!liveupdate_state_updated())
+ return -EBUSY;
+
+ argp->fd = get_unused_fd_flags(O_CLOEXEC);
+ if (argp->fd < 0)
+ return argp->fd;
+
+ guard(mutex)(&session->mutex);
+
+ /* Session might have already finished independatly from global state */
+ if (session->state != LIVEUPDATE_STATE_UPDATED)
+ return -EBUSY;
+
+ ret = luo_retrieve_file(session, argp->token, &file);
+ if (ret < 0) {
+ put_unused_fd(argp->fd);
+
+ return ret;
+ }
+
+ ret = luo_ucmd_respond(ucmd, sizeof(*argp));
+ if (ret)
+ return ret;
+
+ fd_install(argp->fd, file);
+
+ return 0;
+}
+
+static int luo_session_get_state(struct luo_session *session,
+ struct luo_ucmd *ucmd)
+{
+ struct liveupdate_session_get_state *argp = ucmd->cmd;
+
+ if (argp->reserved[0] | argp->reserved[1] | argp->reserved[2])
+ return -EOPNOTSUPP;
+
+ argp->state = READ_ONCE(session->state);
+
+ return luo_ucmd_respond(ucmd, sizeof(*argp));
+}
+
+static int luo_session_set_event(struct luo_session *session,
+ struct luo_ucmd *ucmd)
+{
+ struct liveupdate_session_set_event *argp = ucmd->cmd;
+ int ret = 0;
+
+ switch (argp->event) {
+ case LIVEUPDATE_PREPARE:
+ ret = luo_session_prepare_one(session);
+ break;
+ case LIVEUPDATE_FREEZE:
+ ret = luo_session_freeze_one(session);
+ break;
+ case LIVEUPDATE_FINISH:
+ luo_session_finish_one(session);
+ break;
+ case LIVEUPDATE_CANCEL:
+ luo_session_cancel_one(session);
+ break;
+ default:
+ ret = -EINVAL;
+ }
+
+ return ret;
+}
+
+union ucmd_buffer {
+ struct liveupdate_session_get_state state;
+ struct liveupdate_session_preserve_fd preserve;
+ struct liveupdate_session_restore_fd restore;
+ struct liveupdate_session_set_event event;
+ struct liveupdate_session_unpreserve_fd unpreserve;
+};
+
+struct luo_ioctl_op {
+ unsigned int size;
+ unsigned int min_size;
+ unsigned int ioctl_num;
+ int (*execute)(struct luo_session *session, struct luo_ucmd *ucmd);
+};
+
+#define IOCTL_OP(_ioctl, _fn, _struct, _last) \
+ [_IOC_NR(_ioctl) - LIVEUPDATE_CMD_SESSION_BASE] = { \
+ .size = sizeof(_struct) + \
+ BUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) < \
+ sizeof(_struct)), \
+ .min_size = offsetofend(_struct, _last), \
+ .ioctl_num = _ioctl, \
+ .execute = _fn, \
+ }
+
+static const struct luo_ioctl_op luo_session_ioctl_ops[] = {
+ IOCTL_OP(LIVEUPDATE_SESSION_GET_STATE, luo_session_get_state,
+ struct liveupdate_session_get_state, state),
+ IOCTL_OP(LIVEUPDATE_SESSION_PRESERVE_FD, luo_session_preserve_fd,
+ struct liveupdate_session_preserve_fd, token),
+ IOCTL_OP(LIVEUPDATE_SESSION_RESTORE_FD, luo_session_restore_fd,
+ struct liveupdate_session_restore_fd, token),
+ IOCTL_OP(LIVEUPDATE_SESSION_SET_EVENT, luo_session_set_event,
+ struct liveupdate_session_set_event, event),
+ IOCTL_OP(LIVEUPDATE_SESSION_UNPRESERVE_FD, luo_session_unpreserve_fd,
+ struct liveupdate_session_unpreserve_fd, token),
+};
+
+static long luo_session_ioctl(struct file *filep, unsigned int cmd,
+ unsigned long arg)
+{
+ struct luo_session *session = filep->private_data;
+ const struct luo_ioctl_op *op;
+ struct luo_ucmd ucmd = {};
+ union ucmd_buffer buf;
+ unsigned int nr;
+ int ret;
+
+ nr = _IOC_NR(cmd);
+ if (nr < LIVEUPDATE_CMD_SESSION_BASE || (nr - LIVEUPDATE_CMD_SESSION_BASE) >=
+ ARRAY_SIZE(luo_session_ioctl_ops)) {
+ return -EINVAL;
+ }
+
+ ucmd.ubuffer = (void __user *)arg;
+ ret = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);
+ if (ret)
+ return ret;
+
+ op = &luo_session_ioctl_ops[nr - LIVEUPDATE_CMD_SESSION_BASE];
+ if (op->ioctl_num != cmd)
+ return -ENOIOCTLCMD;
+ if (ucmd.user_size < op->min_size)
+ return -EINVAL;
+
+ ucmd.cmd = &buf;
+ ret = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer,
+ ucmd.user_size);
+ if (ret)
+ return ret;
+
+ return op->execute(session, &ucmd);
+}
+
static const struct file_operations luo_session_fops = {
.owner = THIS_MODULE,
.release = luo_session_release,
+ .unlocked_ioctl = luo_session_ioctl,
};
static void luo_session_deserialize(void)
@@ -267,6 +528,7 @@ static void luo_session_deserialize(void)
session->state = LIVEUPDATE_STATE_UPDATED;
session->count = luo_session_global.ser[i].count;
session->files = luo_session_global.ser[i].files;
+ luo_file_deserialize(session);
}
}
@@ -501,7 +763,25 @@ static int luo_session_prepare(struct liveupdate_subsystem *h, u64 *data)
static int luo_session_freeze(struct liveupdate_subsystem *h, u64 *data)
{
- return 0;
+ struct luo_session *it;
+ int ret;
+
+ WARN_ON(!luo_session_global.fdt);
+
+ scoped_guard(rwsem_read, &luo_session_global.rwsem) {
+ list_for_each_entry(it, &luo_session_global.list, list) {
+ if (it->state == LIVEUPDATE_STATE_PREPARED) {
+ ret = luo_session_freeze_one(it);
+ if (ret)
+ break;
+ }
+ }
+ }
+
+ if (ret)
+ luo_session_cancel(h, 0);
+
+ return ret;
}
/*
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 13/30] liveupdate: luo_file: implement file systems callbacks
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Implements the core logic within luo_file.c to invoke the prepare,
reboot, finish, and cancel callbacks for preserved file instances,
replacing the previous stub implementations. It also handles
the persistence and retrieval of the u64 data payload associated with
each file via the LUO FDT.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/liveupdate.h | 79 ++++
kernel/liveupdate/Makefile | 1 +
kernel/liveupdate/luo_file.c | 599 +++++++++++++++++++++++++++++++
kernel/liveupdate/luo_internal.h | 14 +
4 files changed, 693 insertions(+)
create mode 100644 kernel/liveupdate/luo_file.c
diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
index 4c378a986cfe..c0a7f8c40719 100644
--- a/include/linux/liveupdate.h
+++ b/include/linux/liveupdate.h
@@ -13,6 +13,72 @@
#include <uapi/linux/liveupdate.h>
struct liveupdate_subsystem;
+struct liveupdate_file_handler;
+struct file;
+
+/**
+ * struct liveupdate_file_ops - Callbacks for live-updatable files.
+ * @prepare: Optional. Saves state for a specific file instance @file,
+ * before update, potentially returning value via @data.
+ * Returns 0 on success, negative errno on failure.
+ * @freeze: Optional. Performs final actions just before kernel
+ * transition, potentially reading/updating the handle via
+ * @data.
+ * Returns 0 on success, negative errno on failure.
+ * @cancel: Optional. Cleans up state/resources if update is aborted
+ * after prepare/freeze succeeded, using the @data handle (by
+ * value) from the successful prepare. Returns void.
+ * @finish: Optional. Performs final cleanup in the new kernel using the
+ * preserved @data handle (by value). Returns void.
+ * @retrieve: Retrieve the preserved file. Must be called before finish.
+ * @can_preserve: callback to determine if @file can be preserved by this
+ * handler.
+ * Return bool (true if preservable, false otherwise).
+ * @owner: Module reference
+ */
+struct liveupdate_file_ops {
+ int (*prepare)(struct liveupdate_file_handler *handler,
+ struct file *file, u64 *data);
+ int (*freeze)(struct liveupdate_file_handler *handler,
+ struct file *file, u64 *data);
+ void (*cancel)(struct liveupdate_file_handler *handler,
+ struct file *file, u64 data);
+ void (*finish)(struct liveupdate_file_handler *handler,
+ struct file *file, u64 data, bool reclaimed);
+ int (*retrieve)(struct liveupdate_file_handler *handler,
+ u64 data, struct file **file);
+ bool (*can_preserve)(struct liveupdate_file_handler *handler,
+ struct file *file);
+ struct module *owner;
+};
+
+/* The max size is set so it can be reliably used during in serialization */
+#define LIVEUPDATE_HNDL_COMPAT_LENGTH 48
+
+/**
+ * struct liveupdate_file_handler - Represents a handler for a live-updatable
+ * file type.
+ * @ops: Callback functions
+ * @compatible: The compatibility string (e.g., "memfd-v1", "vfiofd-v1")
+ * that uniquely identifies the file type this handler supports.
+ * This is matched against the compatible string associated with
+ * individual &struct liveupdate_file instances.
+ * @list: used for linking this handler instance into a global list of
+ * registered file handlers.
+ * @count: Atomic counter of number of files that are preserved and use
+ * this handler.
+ *
+ * Modules that want to support live update for specific file types should
+ * register an instance of this structure. LUO uses this registration to
+ * determine if a given file can be preserved and to find the appropriate
+ * operations to manage its state across the update.
+ */
+struct liveupdate_file_handler {
+ const struct liveupdate_file_ops *ops;
+ const char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
+ struct list_head list;
+ atomic_t count;
+};
/**
* struct liveupdate_subsystem_ops - LUO events callback functions
@@ -83,6 +149,9 @@ int liveupdate_register_subsystem(struct liveupdate_subsystem *h);
int liveupdate_unregister_subsystem(struct liveupdate_subsystem *h);
int liveupdate_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data);
+int liveupdate_register_file_handler(struct liveupdate_file_handler *h);
+int liveupdate_unregister_file_handler(struct liveupdate_file_handler *h);
+
#else /* CONFIG_LIVEUPDATE */
static inline int liveupdate_reboot(void)
@@ -126,5 +195,15 @@ static inline int liveupdate_get_subsystem_data(struct liveupdate_subsystem *h,
return -ENODATA;
}
+static inline int liveupdate_register_file_handler(struct liveupdate_file_handler *h)
+{
+ return 0;
+}
+
+static inline int liveupdate_unregister_file_handler(struct liveupdate_file_handler *h)
+{
+ return 0;
+}
+
#endif /* CONFIG_LIVEUPDATE */
#endif /* _LINUX_LIVEUPDATE_H */
diff --git a/kernel/liveupdate/Makefile b/kernel/liveupdate/Makefile
index f64cfc92cbf0..282d36a18993 100644
--- a/kernel/liveupdate/Makefile
+++ b/kernel/liveupdate/Makefile
@@ -2,6 +2,7 @@
luo-y := \
luo_core.o \
+ luo_file.o \
luo_ioctl.o \
luo_session.o \
luo_subsystems.o
diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c
new file mode 100644
index 000000000000..69f3acf90da5
--- /dev/null
+++ b/kernel/liveupdate/luo_file.c
@@ -0,0 +1,599 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+/**
+ * DOC: LUO file descriptors
+ *
+ * LUO provides the infrastructure necessary to preserve
+ * specific types of stateful file descriptors across a kernel live
+ * update transition. The primary goal is to allow workloads, such as virtual
+ * machines using vfio, memfd, or iommufd to retain access to their essential
+ * resources without interruption after the underlying kernel is updated.
+ *
+ * The framework operates based on handler registration and instance tracking:
+ *
+ * 1. Handler Registration: Kernel modules responsible for specific file
+ * types (e.g., memfd, vfio) register a &struct liveupdate_file_handler
+ * handler. This handler contains callbacks
+ * (&liveupdate_file_handler.ops->prepare,
+ * &liveupdate_file_handler.ops->freeze,
+ * &liveupdate_file_handler.ops->finish, etc.) and a unique 'compatible' string
+ * identifying the file type. Registration occurs via
+ * liveupdate_register_file_handler().
+ *
+ * 2. File Instance Tracking: When a potentially preservable file needs to be
+ * managed for live update, the core LUO logic (luo_preserve_file()) finds a
+ * compatible registered handler using its
+ * &liveupdate_file_handler.ops->can_preserve callback. If found, an internal
+ * &struct luo_file instance is created, assigned a unique u64 'token', and
+ * added to a list.
+ *
+ * 3. State Persistence ...
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/atomic.h>
+#include <linux/err.h>
+#include <linux/file.h>
+#include <linux/kexec_handover.h>
+#include <linux/liveupdate.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/xarray.h>
+#include "luo_internal.h"
+
+/* Registered files. */
+static DECLARE_RWSEM(luo_file_handler_list_rwsem);
+static LIST_HEAD(luo_file_handler_list);
+
+/**
+ * struct luo_file_ser - Represents the serialized preserves files.
+ * @compatible: File handler compatabile string.
+ * @files: Private data
+ * @token: User provided token for this file
+ *
+ * If this structure is modified, LUO_SESSION_COMPATIBLE must be updated.
+ */
+struct luo_file_ser {
+ char compatible[LIVEUPDATE_HNDL_COMPAT_LENGTH];
+ u64 data;
+ u64 token;
+} __packed;
+
+/**
+ * struct luo_file - Represents a file descriptor instance preserved
+ * across live update.
+ * @fh: Pointer to the &struct liveupdate_file_handler containing
+ * the implementation of prepare, freeze, cancel, and finish
+ * operations specific to this file's type.
+ * @file: A pointer to the kernel's &struct file object representing
+ * the open file descriptor that is being preserved.
+ * @private_data: Internal storage used by the live update core framework
+ * between phases.
+ * @reclaimed: Flag indicating whether this preserved file descriptor has
+ * been successfully 'reclaimed' (e.g., requested via an ioctl)
+ * by user-space or the owning kernel subsystem in the new
+ * kernel after the live update.
+ * @state: The current state of file descriptor, it is allowed to
+ * prepare, freeze, and finish FDs before the global state
+ * switch.
+ * @mutex: Lock to protect FD state, and allow independently to change
+ * the FD state compared to global state.
+ *
+ * This structure holds the necessary callbacks and context for managing a
+ * specific open file descriptor throughout the different phases of a live
+ * update process. Instances of this structure are typically allocated,
+ * populated with file-specific details (&file, &arg, callbacks, compatibility
+ * string, token), and linked into a central list managed by the LUO. The
+ * private_data field is used internally by the core logic to store state
+ * between phases.
+ */
+struct luo_file {
+ struct liveupdate_file_handler *fh;
+ struct file *file;
+ u64 private_data;
+ bool reclaimed;
+ enum liveupdate_state state;
+ struct mutex mutex;
+};
+
+static int luo_file_prepare_one(struct luo_file *h)
+{
+ int ret = 0;
+
+ guard(mutex)(&h->mutex);
+ if (h->state == LIVEUPDATE_STATE_NORMAL) {
+ if (h->fh->ops->prepare) {
+ ret = h->fh->ops->prepare(h->fh, h->file,
+ &h->private_data);
+ }
+ if (!ret)
+ h->state = LIVEUPDATE_STATE_PREPARED;
+ } else {
+ WARN_ON_ONCE(h->state != LIVEUPDATE_STATE_PREPARED &&
+ h->state != LIVEUPDATE_STATE_FROZEN);
+ }
+
+ return ret;
+}
+
+static int luo_file_freeze_one(struct luo_file *h)
+{
+ int ret = 0;
+
+ guard(mutex)(&h->mutex);
+ if (h->state == LIVEUPDATE_STATE_PREPARED) {
+ if (h->fh->ops->freeze) {
+ ret = h->fh->ops->freeze(h->fh, h->file,
+ &h->private_data);
+ }
+ if (!ret)
+ h->state = LIVEUPDATE_STATE_FROZEN;
+ } else {
+ WARN_ON_ONCE(h->state != LIVEUPDATE_STATE_FROZEN);
+ }
+
+ return ret;
+}
+
+static void luo_file_finish_one(struct luo_file *h)
+{
+ guard(mutex)(&h->mutex);
+ if (h->state == LIVEUPDATE_STATE_UPDATED) {
+ if (h->fh->ops->finish) {
+ h->fh->ops->finish(h->fh, h->file, h->private_data,
+ h->reclaimed);
+ }
+ h->state = LIVEUPDATE_STATE_NORMAL;
+ } else {
+ WARN_ON_ONCE(h->state != LIVEUPDATE_STATE_NORMAL);
+ }
+}
+
+static void luo_file_cancel_one(struct luo_file *h)
+{
+ guard(mutex)(&h->mutex);
+ if (h->state == LIVEUPDATE_STATE_NORMAL)
+ return;
+
+ if (WARN_ON_ONCE(h->state != LIVEUPDATE_STATE_PREPARED &&
+ h->state != LIVEUPDATE_STATE_FROZEN)) {
+ return;
+ }
+
+ if (h->fh->ops->cancel)
+ h->fh->ops->cancel(h->fh, h->file, h->private_data);
+
+ h->private_data = 0;
+ h->state = LIVEUPDATE_STATE_NORMAL;
+}
+
+static void __luo_file_cancel(struct luo_session *session)
+{
+ unsigned long token;
+ struct luo_file *h;
+
+ xa_for_each(&session->files_xa, token, h)
+ luo_file_cancel_one(h);
+}
+
+int luo_file_prepare(struct luo_session *session)
+{
+ struct luo_file *luo_file;
+ struct luo_file_ser *ser;
+ unsigned long token;
+ size_t ser_size;
+ int ret = 0;
+ int i;
+
+ if (!session->count)
+ return 0;
+
+ ser_size = session->count * sizeof(struct luo_file_ser);
+ ser = luo_contig_alloc_preserve(ser_size);
+ if (IS_ERR(ser))
+ return PTR_ERR(ser);
+
+ i = 0;
+ xa_for_each(&session->files_xa, token, luo_file) {
+ ret = luo_file_prepare_one(luo_file);
+ if (ret < 0) {
+ pr_err("Prepare failed for session[%s] token[%#0llx] handler[%s] ret[%d]\n",
+ session->name, (u64)token, luo_file->fh->compatible, ret);
+ goto exit_cleanup;
+ }
+
+ strscpy(ser[i].compatible, luo_file->fh->compatible,
+ sizeof(ser[i].compatible));
+ ser[i].data = luo_file->private_data;
+ ser[i].token = token;
+ i++;
+ }
+
+ session->files = __pa(ser);
+
+ return 0;
+
+exit_cleanup:
+ __luo_file_cancel(session);
+ luo_contig_free_unpreserve(ser, ser_size);
+
+ return ret;
+}
+
+int luo_file_freeze(struct luo_session *session)
+{
+ struct luo_file *luo_file;
+ struct luo_file_ser *ser;
+ unsigned long token;
+ size_t ser_size;
+ int ret = 0;
+ int i;
+
+ if (!session->count)
+ return 0;
+
+ if (WARN_ON(!session->files))
+ return -EINVAL;
+
+ ser = __va(session->files);
+
+ i = 0;
+ xa_for_each(&session->files_xa, token, luo_file) {
+ ret = luo_file_freeze_one(luo_file);
+ if (ret < 0) {
+ pr_err("Freeze failed for session[%s] token[%#0llx] handler[%s] ret[%d]\n",
+ session->name, (u64)token, luo_file->fh->compatible, ret);
+ goto exit_cleanup;
+ }
+ ser[i].data = luo_file->private_data;
+ i++;
+ }
+
+ return 0;
+
+exit_cleanup:
+ __luo_file_cancel(session);
+ ser_size = session->count * sizeof(struct luo_file_ser);
+ luo_contig_free_unpreserve(ser, ser_size);
+
+ return ret;
+}
+
+void luo_file_finish(struct luo_session *session)
+{
+ struct luo_file *luo_file;
+ struct luo_file_ser *ser;
+ unsigned long token;
+ size_t ser_size;
+
+ if (!session->count)
+ return;
+
+ xa_for_each(&session->files_xa, token, luo_file)
+ luo_file_finish_one(luo_file);
+
+ ser_size = session->count * sizeof(struct luo_file_ser);
+ ser = __va(session->files);
+ luo_contig_free_restore(ser, ser_size);
+}
+
+void luo_file_cancel(struct luo_session *session)
+{
+ struct luo_file_ser *ser;
+ size_t ser_size;
+
+ if (!session->count)
+ return;
+
+ __luo_file_cancel(session);
+
+ if (session->files) {
+ ser = __va(session->files);
+ ser_size = session->count * sizeof(struct luo_file_ser);
+ luo_contig_free_unpreserve(ser, ser_size);
+ session->files = 0;
+ }
+}
+
+void luo_file_deserialize(struct luo_session *session)
+{
+ struct luo_file_ser *ser;
+ u64 i;
+
+ if (!session->files)
+ return;
+
+ guard(rwsem_read)(&luo_file_handler_list_rwsem);
+ ser = __va(session->files);
+ for (i = 0; i < session->count; i++) {
+ struct liveupdate_file_handler *fh;
+ bool handler_found = false;
+ struct luo_file *luo_file;
+ int ret;
+
+ if (xa_load(&session->files_xa, ser[i].token)) {
+ luo_restore_fail("Duplicate token %llu found in incoming FDT for file descriptors.\n",
+ ser[i].token);
+ }
+
+ list_for_each_entry(fh, &luo_file_handler_list, list) {
+ if (!strcmp(fh->compatible, ser[i].compatible)) {
+ handler_found = true;
+ break;
+ }
+ }
+
+ if (!handler_found) {
+ luo_restore_fail("No registered handler for compatible '%s'\n",
+ ser[i].compatible);
+ }
+
+ luo_file = kzalloc(sizeof(*luo_file),
+ GFP_KERNEL | __GFP_NOFAIL);
+ luo_file->fh = fh;
+ luo_file->file = NULL;
+ luo_file->private_data = ser[i].data;
+ luo_file->reclaimed = false;
+ mutex_init(&luo_file->mutex);
+ luo_file->state = LIVEUPDATE_STATE_UPDATED;
+ ret = xa_err(xa_store(&session->files_xa, ser[i].token,
+ luo_file, GFP_KERNEL | __GFP_NOFAIL));
+ if (ret < 0) {
+ luo_restore_fail("Failed to store luo_file for token %llu in XArray: %d\n",
+ ser[i].token, ret);
+ }
+ }
+}
+
+/**
+ * luo_preserve_file - Register a file descriptor for live update management.
+ * @token: Token value for this file descriptor.
+ * @fd: file descriptor to be preserved.
+ *
+ * Context: Must be called when LUO is in 'normal' state.
+ *
+ * Return: 0 on success. Negative errno on failure.
+ */
+int luo_preserve_file(struct luo_session *session, u64 token, int fd)
+{
+ struct liveupdate_file_handler *fh;
+ struct luo_file *luo_file;
+ bool found = false;
+ int ret = -ENOENT;
+ struct file *file;
+
+ file = fget(fd);
+ if (!file) {
+ pr_err("Bad file descriptor\n");
+ return -EBADF;
+ }
+
+ guard(rwsem_read)(&luo_file_handler_list_rwsem);
+ list_for_each_entry(fh, &luo_file_handler_list, list) {
+ if (fh->ops->can_preserve(fh, file)) {
+ found = true;
+ break;
+ }
+ }
+
+ if (!found)
+ goto exit_cleanup;
+
+ luo_file = kzalloc(sizeof(*luo_file), GFP_KERNEL);
+ if (!luo_file) {
+ ret = -ENOMEM;
+ goto exit_cleanup;
+ }
+
+ luo_file->private_data = 0;
+ luo_file->reclaimed = false;
+
+ luo_file->file = file;
+ luo_file->fh = fh;
+ mutex_init(&luo_file->mutex);
+ luo_file->state = LIVEUPDATE_STATE_NORMAL;
+
+ if (xa_load(&session->files_xa, token)) {
+ ret = -EEXIST;
+ pr_warn("Token %llu is already taken\n", token);
+ mutex_destroy(&luo_file->mutex);
+ kfree(luo_file);
+ goto exit_cleanup;
+ }
+
+ ret = xa_err(xa_store(&session->files_xa, token, luo_file,
+ GFP_KERNEL));
+ if (ret < 0) {
+ pr_warn("Failed to store file for token %llu in XArray: %d\n",
+ token, ret);
+ mutex_destroy(&luo_file->mutex);
+ kfree(luo_file);
+ goto exit_cleanup;
+ }
+ atomic_inc(&luo_file->fh->count);
+ session->count++;
+
+exit_cleanup:
+ if (ret)
+ fput(file);
+
+ return ret;
+}
+
+/**
+ * luo_unpreserve_file - Unregister a file instance using its token.
+ * @token: The unique token of the file instance to unregister.
+ *
+ * Finds the &struct luo_file associated with the @token in the
+ * global list and removes it. This function *only* removes the entry from the
+ * list; it does *not* free the memory allocated for the &struct luo_file
+ * itself. The caller is responsible for freeing the structure after this
+ * function returns successfully.
+ *
+ * Context: Can be called when a preserved file descriptor is closed or
+ * no longer needs live update management.
+ *
+ * Return: 0 on success. Negative errno on failure.
+ */
+int luo_unpreserve_file(struct luo_session *session, u64 token)
+{
+ struct luo_file *luo_file;
+
+ luo_file = xa_erase(&session->files_xa, token);
+ if (!luo_file)
+ return -ENOENT;
+
+ if (luo_file->file)
+ fput(luo_file->file);
+ mutex_destroy(&luo_file->mutex);
+ scoped_guard(rwsem_read, &luo_file_handler_list_rwsem)
+ atomic_dec(&luo_file->fh->count);
+ kfree(luo_file);
+ session->count--;
+
+ return 0;
+}
+
+/**
+ * luo_retrieve_file - Find a registered file instance by its token.
+ * @token: The unique token of the file instance to retrieve.
+ * @filep: Output parameter. On success (return value 0), this will point
+ * to the retrieved "struct file".
+ *
+ * Searches the global list for a &struct luo_file matching the @token. Uses a
+ * read lock, allowing concurrent retrievals.
+ *
+ * Return: 0 on success. Negative errno on failure.
+ */
+int luo_retrieve_file(struct luo_session *session, u64 token,
+ struct file **filep)
+{
+ struct luo_file *luo_file;
+ int ret = 0;
+
+ luo_file = xa_load(&session->files_xa, token);
+ if (!luo_file)
+ return -ENOENT;
+
+ if (luo_file->reclaimed)
+ return -EADDRINUSE;
+
+ guard(mutex)(&luo_file->mutex);
+ if (luo_file->reclaimed)
+ return -EADDRINUSE;
+
+ ret = luo_file->fh->ops->retrieve(luo_file->fh, luo_file->private_data,
+ filep);
+ if (!ret) {
+ /* Get a reference so, we can keep this file in LUO */
+ luo_file->file = *filep;
+ get_file(luo_file->file);
+ luo_file->reclaimed = true;
+ }
+
+ return ret;
+}
+
+void luo_file_unpreserve_all_files(struct luo_session *session)
+{
+ unsigned long token;
+ struct luo_file *h;
+
+ xa_for_each(&session->files_xa, token, h)
+ luo_unpreserve_file(session, token);
+}
+
+void luo_file_unpreserve_unreclaimed_files(struct luo_session *session)
+{
+ unsigned long token;
+ struct luo_file *h;
+
+ xa_for_each(&session->files_xa, token, h) {
+ if (!h->reclaimed) {
+ pr_err("Unpreserving unreclaimed file, session[%s] token[%#0llx] handler[%s]\n",
+ session->name, (u64)token, h->fh->compatible);
+ luo_unpreserve_file(session, token);
+ }
+ }
+}
+
+/**
+ * liveupdate_register_file_handler - Register a file handler with LUO.
+ * @fh: Pointer to a caller-allocated &struct liveupdate_file_handler.
+ * The caller must initialize this structure, including a unique
+ * 'compatible' string and a valid 'fh' callbacks. This function adds the
+ * handler to the global list of supported file handlers.
+ *
+ * Context: Typically called during module initialization for file types that
+ * support live update preservation.
+ *
+ * Return: 0 on success. Negative errno on failure.
+ */
+int liveupdate_register_file_handler(struct liveupdate_file_handler *fh)
+{
+ struct liveupdate_file_handler *fh_iter;
+
+ guard(rwsem_read)(&luo_state_rwsem);
+ if (!liveupdate_state_normal() && !liveupdate_state_updated())
+ return -EBUSY;
+
+ guard(rwsem_write)(&luo_file_handler_list_rwsem);
+ list_for_each_entry(fh_iter, &luo_file_handler_list, list) {
+ if (!strcmp(fh_iter->compatible, fh->compatible)) {
+ pr_err("File handler registration failed: Compatible string '%s' already registered.\n",
+ fh->compatible);
+ return -EEXIST;
+ }
+ }
+
+ if (!try_module_get(fh->ops->owner))
+ return -EAGAIN;
+
+ INIT_LIST_HEAD(&fh->list);
+ atomic_set(&fh->count, 0);
+ list_add_tail(&fh->list, &luo_file_handler_list);
+
+ return 0;
+}
+
+/**
+ * liveupdate_unregister_file - Unregister a file handler.
+ * @fh: Pointer to the specific &struct liveupdate_file_handler instance
+ * that was previously returned by or passed to
+ * liveupdate_register_file_handler.
+ *
+ * Removes the specified handler instance @fh from the global list of
+ * registered file handlers. This function only removes the entry from the
+ * list; it does not free the memory associated with @fh itself. The caller
+ * is responsible for freeing the structure memory after this function returns
+ * successfully.
+ *
+ * Return: 0 on success. Negative errno on failure.
+ */
+int liveupdate_unregister_file_handler(struct liveupdate_file_handler *fh)
+{
+ guard(rwsem_read)(&luo_state_rwsem);
+ if (!liveupdate_state_normal() && !liveupdate_state_updated())
+ return -EBUSY;
+
+ guard(rwsem_write)(&luo_file_handler_list_rwsem);
+ if (atomic_read(&fh->count)) {
+ pr_warn("Unable to unregister file handler, files are preserved\n");
+ return -EBUSY;
+ }
+
+ list_del_init(&fh->list);
+ module_put(fh->ops->owner);
+
+ return 0;
+}
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index a14e0b685ccb..c9bce82aac22 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -8,6 +8,8 @@
#ifndef _LINUX_LUO_INTERNAL_H
#define _LINUX_LUO_INTERNAL_H
+#include <linux/liveupdate.h>
+
/*
* Handles a deserialization failure: devices and memory is in unpredictable
* state.
@@ -93,4 +95,16 @@ int luo_do_subsystems_freeze_calls(void);
void luo_do_subsystems_finish_calls(void);
void luo_do_subsystems_cancel_calls(void);
+int luo_retrieve_file(struct luo_session *session, u64 token, struct file **filep);
+int luo_preserve_file(struct luo_session *session, u64 token, int fd);
+int luo_unpreserve_file(struct luo_session *session, u64 token);
+void luo_file_unpreserve_all_files(struct luo_session *session);
+void luo_file_unpreserve_unreclaimed_files(struct luo_session *session);
+
+int luo_file_prepare(struct luo_session *session);
+int luo_file_freeze(struct luo_session *session);
+void luo_file_finish(struct luo_session *session);
+void luo_file_cancel(struct luo_session *session);
+void luo_file_deserialize(struct luo_session *session);
+
#endif /* _LINUX_LUO_INTERNAL_H */
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 12/30] liveupdate: luo_ioctl: add user interface
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Introduce the user-space interface for the Live Update Orchestrator
via ioctl commands, enabling external control over the live update
process and management of preserved resources.
The idea is that there is going to be a single userspace agent driving
the live update, therefore, only a single process can ever hold this
device opened at a time.
The following ioctl commands are introduced:
LIVEUPDATE_IOCTL_GET_STATE
Allows userspace to query the current state of the LUO state machine
(e.g., NORMAL, PREPARED, UPDATED).
LIVEUPDATE_IOCTL_SET_EVENT
Enables userspace to drive the LUO state machine by sending global
events. This includes:
LIVEUPDATE_PREPARE
To begin the state-saving process.
LIVEUPDATE_FINISH
To signal completion of restoration in the new kernel.
LIVEUPDATE_CANCEL
To abort a prepared update.
LIVEUPDATE_IOCTL_CREATE_SESSION
Provides a way for userspace to create a named session for grouping file
descriptors that need to be preserved. It returns a new file descriptor
representing the session.
LIVEUPDATE_IOCTL_RETRIEVE_SESSION
Allows the userspace agent in the new kernel to reclaim a preserved
session by its name, receiving a new file descriptor to manage the
restored resources.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/uapi/linux/liveupdate.h | 199 ++++++++++++++++++++++++++++++
kernel/liveupdate/luo_internal.h | 20 +++
kernel/liveupdate/luo_ioctl.c | 201 +++++++++++++++++++++++++++++++
3 files changed, 420 insertions(+)
diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h
index e8c0c210a790..2e38ef3094aa 100644
--- a/include/uapi/linux/liveupdate.h
+++ b/include/uapi/linux/liveupdate.h
@@ -14,6 +14,32 @@
#include <linux/ioctl.h>
#include <linux/types.h>
+/**
+ * DOC: General ioctl format
+ *
+ * The ioctl interface follows a general format to allow for extensibility. Each
+ * ioctl is passed in a structure pointer as the argument providing the size of
+ * the structure in the first u32. The kernel checks that any structure space
+ * beyond what it understands is 0. This allows userspace to use the backward
+ * compatible portion while consistently using the newer, larger, structures.
+ *
+ * ioctls use a standard meaning for common errnos:
+ *
+ * - ENOTTY: The IOCTL number itself is not supported at all
+ * - E2BIG: The IOCTL number is supported, but the provided structure has
+ * non-zero in a part the kernel does not understand.
+ * - EOPNOTSUPP: The IOCTL number is supported, and the structure is
+ * understood, however a known field has a value the kernel does not
+ * understand or support.
+ * - EINVAL: Everything about the IOCTL was understood, but a field is not
+ * correct.
+ * - ENOENT: A provided token does not exist.
+ * - ENOMEM: Out of memory.
+ * - EOVERFLOW: Mathematics overflowed.
+ *
+ * As well as additional errnos, within specific ioctls.
+ */
+
/**
* enum liveupdate_state - Defines the possible states of the live update
* orchestrator.
@@ -94,4 +120,177 @@ enum liveupdate_event {
/* The maximum length of session name including null termination */
#define LIVEUPDATE_SESSION_NAME_LENGTH 56
+/* The ioctl type, documented in ioctl-number.rst */
+#define LIVEUPDATE_IOCTL_TYPE 0xBA
+
+/* The /dev/liveupdate ioctl commands */
+enum {
+ LIVEUPDATE_CMD_BASE = 0x00,
+ LIVEUPDATE_CMD_GET_STATE = LIVEUPDATE_CMD_BASE,
+ LIVEUPDATE_CMD_SET_EVENT = 0x01,
+ LIVEUPDATE_CMD_CREATE_SESSION = 0x02,
+ LIVEUPDATE_CMD_RETRIEVE_SESSION = 0x03,
+};
+
+/**
+ * struct liveupdate_ioctl_get_state - ioctl(LIVEUPDATE_IOCTL_GET_STATE)
+ * @size: Input; sizeof(struct liveupdate_ioctl_get_state)
+ * @state: Output; The current live update state.
+ *
+ * Query the current state of the live update orchestrator.
+ *
+ * The kernel fills the @state with the current
+ * state of the live update subsystem. Possible states are:
+ *
+ * - %LIVEUPDATE_STATE_NORMAL: Default state; no live update operation is
+ * currently in progress.
+ * - %LIVEUPDATE_STATE_PREPARED: The preparation phase (triggered by
+ * %LIVEUPDATE_PREPARE) has completed
+ * successfully. The system is ready for the
+ * reboot transition. Note that some
+ * device operations (e.g., unbinding, new DMA
+ * mappings) might be restricted in this state.
+ * - %LIVEUPDATE_STATE_UPDATED: The system has successfully rebooted into the
+ * new kernel via live update. It is now running
+ * the new kernel code and is awaiting the
+ * completion signal from user space via
+ * %LIVEUPDATE_FINISH after restoration tasks are
+ * done.
+ *
+ * See the definition of &enum liveupdate_state for more details on each state.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+struct liveupdate_ioctl_get_state {
+ __u32 size;
+ __u32 state;
+};
+
+#define LIVEUPDATE_IOCTL_GET_STATE \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_GET_STATE)
+
+/**
+ * struct liveupdate_ioctl_set_event - ioctl(LIVEUPDATE_IOCTL_SET_EVENT)
+ * @size: Input; sizeof(struct liveupdate_ioctl_set_event)
+ * @event: Input; The live update event.
+ *
+ * Notify live update orchestrator about global event, that causes a state
+ * transition.
+ *
+ * Event, can be one of the following:
+ *
+ * - %LIVEUPDATE_PREPARE: Initiates the live update preparation phase. This
+ * typically triggers the saving process for items marked
+ * via the PRESERVE ioctls. This typically occurs
+ * *before* the "blackout window", while user
+ * applications (e.g., VMs) may still be running. Kernel
+ * subsystems receiving the %LIVEUPDATE_PREPARE event
+ * should serialize necessary state. This command does
+ * not transfer data.
+ * - %LIVEUPDATE_FINISH: Signal restoration completion and triggercleanup.
+ *
+ * Signals that user space has completed all necessary
+ * restoration actions in the new kernel (after a live
+ * update reboot). Calling this ioctl triggers the
+ * cleanup phase: any resources that were successfully
+ * preserved but were *not* subsequently restored
+ * (reclaimed) via the RESTORE ioctls will have their
+ * preserved state discarded and associated kernel
+ * resources released. Involved devices may be reset. All
+ * desired restorations *must* be completed *before*
+ * this. Kernel callbacks for the %LIVEUPDATE_FINISH
+ * event must not fail. Successfully completing this
+ * phase transitions the system state from
+ * %LIVEUPDATE_STATE_UPDATED back to
+ * %LIVEUPDATE_STATE_NORMAL. This command does
+ * not transfer data.
+ * - %LIVEUPDATE_CANCEL: Cancel the live update preparation phase.
+ *
+ * Notifies the live update subsystem to abort the
+ * preparation sequence potentially initiated by
+ * %LIVEUPDATE_PREPARE event.
+ *
+ * When triggered, subsystems receiving the
+ * %LIVEUPDATE_CANCEL event should revert any state
+ * changes or actions taken specifically for the aborted
+ * prepare phase (e.g., discard partially serialized
+ * state). The kernel releases resources allocated
+ * specifically for this *aborted preparation attempt*.
+ *
+ * This operation cancels the current *attempt* to
+ * prepare for a live update but does **not** remove
+ * previously validated items from the internal list
+ * of potentially preservable resources.
+ *
+ * This command does not transfer data. Kernel callbacks
+ * for the %LIVEUPDATE_CANCEL event must not fail.
+ *
+ * See the definition of &enum liveupdate_event for more details on each state.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+struct liveupdate_ioctl_set_event {
+ __u32 size;
+ __u32 event;
+};
+
+#define LIVEUPDATE_IOCTL_SET_EVENT \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_SET_EVENT)
+
+/**
+ * struct liveupdate_ioctl_create_session - ioctl(LIVEUPDATE_IOCTL_CREATE_SESSION)
+ * @size: Input; sizeof(struct liveupdate_ioctl_create_session)
+ * @fd: Output; The new file descriptor for the created session.
+ * @name: Input; A null-terminated string for the session name, max
+ * length %LIVEUPDATE_SESSION_NAME_LENGTH including termination
+ * char.
+ *
+ * Creates a new live update session for managing preserved resources.
+ * This ioctl can only be called on the main /dev/liveupdate device.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+struct liveupdate_ioctl_create_session {
+ __u32 size;
+ __s32 fd;
+ __u8 name[LIVEUPDATE_SESSION_NAME_LENGTH];
+};
+
+#define LIVEUPDATE_IOCTL_CREATE_SESSION \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_CREATE_SESSION)
+
+/**
+ * struct liveupdate_ioctl_retrieve_session - ioctl(LIVEUPDATE_IOCTL_RETRIEVE_SESSION)
+ * @size: Input; sizeof(struct liveupdate_ioctl_retrieve_session)
+ * @fd: Output; The new file descriptor for the retrieved session.
+ * @name: Input; A null-terminated string identifying the session to retrieve.
+ * The name must exactly match the name used when the session was
+ * created in the previous kernel.
+ *
+ * Retrieves a handle (a new file descriptor) for a preserved session by its
+ * name. This is the primary mechanism for a userspace agent to regain control
+ * of its preserved resources after a live update.
+ *
+ * The userspace application provides the null-terminated `name` of a session
+ * it created before the live update. If a preserved session with a matching
+ * name is found, the kernel instantiates it and returns a new file descriptor
+ * in the `fd` field. This new session FD can then be used for all file-specific
+ * operations, such as restoring individual file descriptors with
+ * LIVEUPDATE_SESSION_RESTORE_FD.
+ *
+ * It is the responsibility of the userspace application to know the names of
+ * the sessions it needs to retrieve. If no session with the given name is
+ * found, the ioctl will fail with -ENOENT.
+ *
+ * This ioctl can only be called on the main /dev/liveupdate device when the
+ * system is in the LIVEUPDATE_STATE_UPDATED state.
+ */
+struct liveupdate_ioctl_retrieve_session {
+ __u32 size;
+ __s32 fd;
+ __u8 name[64];
+};
+
+#define LIVEUPDATE_IOCTL_RETRIEVE_SESSION \
+ _IO(LIVEUPDATE_IOCTL_TYPE, LIVEUPDATE_CMD_RETRIEVE_SESSION)
#endif /* _UAPI_LIVEUPDATE_H */
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index 9223f71844ca..a14e0b685ccb 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -17,6 +17,26 @@
*/
#define luo_restore_fail(__fmt, ...) panic(__fmt, ##__VA_ARGS__)
+struct luo_ucmd {
+ void __user *ubuffer;
+ u32 user_size;
+ void *cmd;
+};
+
+static inline int luo_ucmd_respond(struct luo_ucmd *ucmd,
+ size_t kernel_cmd_size)
+{
+ /*
+ * Copy the minimum of what the user provided and what we actually
+ * have.
+ */
+ if (copy_to_user(ucmd->ubuffer, ucmd->cmd,
+ min_t(size_t, ucmd->user_size, kernel_cmd_size))) {
+ return -EFAULT;
+ }
+ return 0;
+}
+
int luo_cancel(void);
int luo_prepare(void);
int luo_freeze(void);
diff --git a/kernel/liveupdate/luo_ioctl.c b/kernel/liveupdate/luo_ioctl.c
index fc2afb450ad5..01ccb8a6d3f4 100644
--- a/kernel/liveupdate/luo_ioctl.c
+++ b/kernel/liveupdate/luo_ioctl.c
@@ -5,6 +5,25 @@
* Pasha Tatashin <pasha.tatashin@soleen.com>
*/
+/**
+ * DOC: LUO ioctl Interface
+ *
+ * The IOCTL user-space control interface for the LUO subsystem.
+ * It registers a character device, typically found at ``/dev/liveupdate``,
+ * which allows a userspace agent to manage the LUO state machine and its
+ * associated resources, such as preservable file descriptors.
+ *
+ * To ensure that the state machine is controlled by a single entity, access
+ * to this device is exclusive: only one process is permitted to have
+ * ``/dev/liveupdate`` open at any given time. Subsequent open attempts will
+ * fail with -EBUSY until the first process closes its file descriptor.
+ * This singleton model simplifies state management by preventing conflicting
+ * commands from multiple userspace agents.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/atomic.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/fs.h>
@@ -19,10 +38,191 @@
struct luo_device_state {
struct miscdevice miscdev;
+ atomic_t in_use;
+};
+
+static int luo_ioctl_get_state(struct luo_ucmd *ucmd)
+{
+ struct liveupdate_ioctl_get_state *argp = ucmd->cmd;
+
+ argp->state = liveupdate_get_state();
+
+ return luo_ucmd_respond(ucmd, sizeof(*argp));
+}
+
+static int luo_ioctl_set_event(struct luo_ucmd *ucmd)
+{
+ struct liveupdate_ioctl_set_event *argp = ucmd->cmd;
+ int ret;
+
+ switch (argp->event) {
+ case LIVEUPDATE_PREPARE:
+ ret = luo_prepare();
+ break;
+ case LIVEUPDATE_FINISH:
+ ret = luo_finish();
+ break;
+ case LIVEUPDATE_CANCEL:
+ ret = luo_cancel();
+ break;
+ default:
+ ret = -EOPNOTSUPP;
+ }
+
+ return ret;
+}
+
+static int luo_ioctl_create_session(struct luo_ucmd *ucmd)
+{
+ struct liveupdate_ioctl_create_session *argp = ucmd->cmd;
+ struct file *file;
+ int ret;
+
+ argp->fd = get_unused_fd_flags(O_CLOEXEC);
+ if (argp->fd < 0)
+ return argp->fd;
+
+ ret = luo_session_create(argp->name, &file);
+ if (ret)
+ return ret;
+
+ ret = luo_ucmd_respond(ucmd, sizeof(*argp));
+ if (ret) {
+ fput(file);
+ put_unused_fd(argp->fd);
+ return ret;
+ }
+
+ fd_install(argp->fd, file);
+
+ return 0;
+}
+
+static int luo_ioctl_retrieve_session(struct luo_ucmd *ucmd)
+{
+ struct liveupdate_ioctl_retrieve_session *argp = ucmd->cmd;
+ struct file *file;
+ int ret;
+
+ argp->fd = get_unused_fd_flags(O_CLOEXEC);
+ if (argp->fd < 0)
+ return argp->fd;
+
+ ret = luo_session_retrieve(argp->name, &file);
+ if (ret < 0) {
+ put_unused_fd(argp->fd);
+
+ return ret;
+ }
+
+ ret = luo_ucmd_respond(ucmd, sizeof(*argp));
+ if (ret) {
+ fput(file);
+ put_unused_fd(argp->fd);
+ return ret;
+ }
+
+ fd_install(argp->fd, file);
+
+ return 0;
+}
+
+static int luo_open(struct inode *inodep, struct file *filep)
+{
+ struct luo_device_state *ldev = container_of(filep->private_data,
+ struct luo_device_state,
+ miscdev);
+
+ if (atomic_cmpxchg(&ldev->in_use, 0, 1))
+ return -EBUSY;
+
+ return 0;
+}
+
+static int luo_release(struct inode *inodep, struct file *filep)
+{
+ struct luo_device_state *ldev = container_of(filep->private_data,
+ struct luo_device_state,
+ miscdev);
+ atomic_set(&ldev->in_use, 0);
+
+ return 0;
+}
+
+union ucmd_buffer {
+ struct liveupdate_ioctl_create_session create;
+ struct liveupdate_ioctl_get_state state;
+ struct liveupdate_ioctl_retrieve_session retrieve;
+ struct liveupdate_ioctl_set_event event;
};
+struct luo_ioctl_op {
+ unsigned int size;
+ unsigned int min_size;
+ unsigned int ioctl_num;
+ int (*execute)(struct luo_ucmd *ucmd);
+};
+
+#define IOCTL_OP(_ioctl, _fn, _struct, _last) \
+ [_IOC_NR(_ioctl) - LIVEUPDATE_CMD_BASE] = { \
+ .size = sizeof(_struct) + \
+ BUILD_BUG_ON_ZERO(sizeof(union ucmd_buffer) < \
+ sizeof(_struct)), \
+ .min_size = offsetofend(_struct, _last), \
+ .ioctl_num = _ioctl, \
+ .execute = _fn, \
+ }
+
+static const struct luo_ioctl_op luo_ioctl_ops[] = {
+ IOCTL_OP(LIVEUPDATE_IOCTL_CREATE_SESSION, luo_ioctl_create_session,
+ struct liveupdate_ioctl_create_session, name),
+ IOCTL_OP(LIVEUPDATE_IOCTL_GET_STATE, luo_ioctl_get_state,
+ struct liveupdate_ioctl_get_state, state),
+ IOCTL_OP(LIVEUPDATE_IOCTL_RETRIEVE_SESSION, luo_ioctl_retrieve_session,
+ struct liveupdate_ioctl_retrieve_session, name),
+ IOCTL_OP(LIVEUPDATE_IOCTL_SET_EVENT, luo_ioctl_set_event,
+ struct liveupdate_ioctl_set_event, event),
+};
+
+static long luo_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
+{
+ const struct luo_ioctl_op *op;
+ struct luo_ucmd ucmd = {};
+ union ucmd_buffer buf;
+ unsigned int nr;
+ int ret;
+
+ nr = _IOC_NR(cmd);
+ if (nr < LIVEUPDATE_CMD_BASE ||
+ (nr - LIVEUPDATE_CMD_BASE) >= ARRAY_SIZE(luo_ioctl_ops)) {
+ return -EINVAL;
+ }
+
+ ucmd.ubuffer = (void __user *)arg;
+ ret = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);
+ if (ret)
+ return ret;
+
+ op = &luo_ioctl_ops[nr - LIVEUPDATE_CMD_BASE];
+ if (op->ioctl_num != cmd)
+ return -ENOIOCTLCMD;
+ if (ucmd.user_size < op->min_size)
+ return -EINVAL;
+
+ ucmd.cmd = &buf;
+ ret = copy_struct_from_user(ucmd.cmd, op->size, ucmd.ubuffer,
+ ucmd.user_size);
+ if (ret)
+ return ret;
+
+ return op->execute(&ucmd);
+}
+
static const struct file_operations luo_fops = {
.owner = THIS_MODULE,
+ .open = luo_open,
+ .release = luo_release,
+ .unlocked_ioctl = luo_ioctl,
};
static struct luo_device_state luo_dev = {
@@ -31,6 +231,7 @@ static struct luo_device_state luo_dev = {
.name = "liveupdate",
.fops = &luo_fops,
},
+ .in_use = ATOMIC_INIT(0),
};
static int __init liveupdate_init(void)
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 10/30] liveupdate: luo_subsystems: implement subsystem callbacks
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Implement the core logic within luo_subsystems.c to handle the
invocation of registered subsystem callbacks and manage the persistence
of their state via the LUO FDT. This replaces the stub implementations
from the previous patch.
This completes the core mechanism enabling subsystems to actively
participate in the LUO state machine, execute phase-specific logic, and
persist/restore a u64 state across the live update transition
using the FDT.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_subsystems.c | 167 ++++++++++++++++++++++++++++-
1 file changed, 164 insertions(+), 3 deletions(-)
diff --git a/kernel/liveupdate/luo_subsystems.c b/kernel/liveupdate/luo_subsystems.c
index 69f00d5c000e..ebb7c0db08f3 100644
--- a/kernel/liveupdate/luo_subsystems.c
+++ b/kernel/liveupdate/luo_subsystems.c
@@ -101,8 +101,81 @@ void __init luo_subsystems_startup(void *fdt)
luo_fdt_in = fdt;
}
+static void __luo_do_subsystems_cancel_calls(struct liveupdate_subsystem *boundary_subsystem)
+{
+ struct liveupdate_subsystem *subsystem;
+
+ list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+ if (subsystem == boundary_subsystem)
+ break;
+
+ if (subsystem->ops->cancel) {
+ subsystem->ops->cancel(subsystem,
+ subsystem->private_data);
+ }
+ subsystem->private_data = 0;
+ }
+}
+
+static void luo_subsystems_retrieve_data_from_fdt(void)
+{
+ struct liveupdate_subsystem *subsystem;
+ int node_offset, prop_len;
+ const void *prop;
+
+ if (!luo_fdt_in)
+ return;
+
+ node_offset = fdt_subnode_offset(luo_fdt_in, 0,
+ LUO_SUBSYSTEMS_NODE_NAME);
+ list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+ prop = fdt_getprop(luo_fdt_in, node_offset,
+ subsystem->name, &prop_len);
+
+ if (!prop || prop_len != sizeof(u64)) {
+ luo_restore_fail("In FDT node '/%s' can't find property '%s': %s\n",
+ LUO_SUBSYSTEMS_NODE_NAME,
+ subsystem->name,
+ fdt_strerror(node_offset));
+ }
+ memcpy(&subsystem->private_data, prop, sizeof(u64));
+ }
+}
+
+static int luo_subsystems_commit_data_to_fdt(void)
+{
+ struct liveupdate_subsystem *subsystem;
+ int ret, node_offset;
+
+ node_offset = fdt_subnode_offset(luo_fdt_out, 0,
+ LUO_SUBSYSTEMS_NODE_NAME);
+ list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+ ret = fdt_setprop(luo_fdt_out, node_offset, subsystem->name,
+ &subsystem->private_data, sizeof(u64));
+ if (ret < 0) {
+ pr_err("Failed to set FDT property for subsystem '%s' %s\n",
+ subsystem->name, fdt_strerror(ret));
+ return -ENOENT;
+ }
+ }
+
+ return 0;
+}
+
static int luo_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
{
+ int node_offset, prop_len;
+ const void *prop;
+
+ node_offset = fdt_subnode_offset(luo_fdt_in, 0,
+ LUO_SUBSYSTEMS_NODE_NAME);
+ prop = fdt_getprop(luo_fdt_in, node_offset, h->name, &prop_len);
+ if (!prop || prop_len != sizeof(u64)) {
+ luo_state_read_exit();
+ return -ENOENT;
+ }
+ memcpy(data, prop, sizeof(u64));
+
return 0;
}
@@ -121,7 +194,30 @@ static int luo_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
*/
int luo_do_subsystems_prepare_calls(void)
{
- return 0;
+ struct liveupdate_subsystem *subsystem;
+ int ret;
+
+ guard(mutex)(&luo_subsystem_list_mutex);
+ list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+ if (!subsystem->ops->prepare)
+ continue;
+
+ ret = subsystem->ops->prepare(subsystem,
+ &subsystem->private_data);
+ if (ret < 0) {
+ pr_err("Subsystem '%s' prepare callback failed [%d]\n",
+ subsystem->name, ret);
+ __luo_do_subsystems_cancel_calls(subsystem);
+
+ return ret;
+ }
+ }
+
+ ret = luo_subsystems_commit_data_to_fdt();
+ if (ret)
+ __luo_do_subsystems_cancel_calls(NULL);
+
+ return ret;
}
/**
@@ -139,7 +235,30 @@ int luo_do_subsystems_prepare_calls(void)
*/
int luo_do_subsystems_freeze_calls(void)
{
- return 0;
+ struct liveupdate_subsystem *subsystem;
+ int ret;
+
+ guard(mutex)(&luo_subsystem_list_mutex);
+ list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+ if (!subsystem->ops->freeze)
+ continue;
+
+ ret = subsystem->ops->freeze(subsystem,
+ &subsystem->private_data);
+ if (ret < 0) {
+ pr_err("Subsystem '%s' freeze callback failed [%d]\n",
+ subsystem->name, ret);
+ __luo_do_subsystems_cancel_calls(subsystem);
+
+ return ret;
+ }
+ }
+
+ ret = luo_subsystems_commit_data_to_fdt();
+ if (ret)
+ __luo_do_subsystems_cancel_calls(NULL);
+
+ return ret;
}
/**
@@ -150,6 +269,18 @@ int luo_do_subsystems_freeze_calls(void)
*/
void luo_do_subsystems_finish_calls(void)
{
+ struct liveupdate_subsystem *subsystem;
+
+ guard(mutex)(&luo_subsystem_list_mutex);
+ luo_subsystems_retrieve_data_from_fdt();
+
+ list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+ if (subsystem->ops->finish) {
+ subsystem->ops->finish(subsystem,
+ subsystem->private_data);
+ }
+ subsystem->private_data = 0;
+ }
}
/**
@@ -163,6 +294,9 @@ void luo_do_subsystems_finish_calls(void)
*/
void luo_do_subsystems_cancel_calls(void)
{
+ guard(mutex)(&luo_subsystem_list_mutex);
+ __luo_do_subsystems_cancel_calls(NULL);
+ luo_subsystems_commit_data_to_fdt();
}
/**
@@ -285,7 +419,34 @@ int liveupdate_unregister_subsystem(struct liveupdate_subsystem *h)
return ret;
}
+/**
+ * liveupdate_get_subsystem_data - Retrieve raw private data for a subsystem
+ * from FDT.
+ * @h: Pointer to the liveupdate_subsystem structure representing the
+ * subsystem instance. The 'name' field is used to find the property.
+ * @data: Output pointer where the subsystem's raw private u64 data will be
+ * stored via memcpy.
+ *
+ * Reads the 8-byte data property associated with the subsystem @h->name
+ * directly from the '/subsystems' node within the globally accessible
+ * 'luo_fdt_in' blob. Returns appropriate error codes if inputs are invalid, or
+ * nodes/properties are missing or invalid.
+ *
+ * Return: 0 on success. -ENOENT on error.
+ */
int liveupdate_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
{
- return 0;
+ int ret;
+
+ luo_state_read_enter();
+ if (WARN_ON_ONCE(!luo_fdt_in || !liveupdate_state_updated())) {
+ luo_state_read_exit();
+ return -ENOENT;
+ }
+
+ scoped_guard(mutex, &luo_subsystem_list_mutex)
+ ret = luo_get_subsystem_data(h, data);
+ luo_state_read_exit();
+
+ return ret;
}
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 09/30] liveupdate: luo_subsystems: add subsystem registration
From: Pasha Tatashin @ 2025-09-29 1:03 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Introduce the framework for kernel subsystems (e.g., KVM, IOMMU, device
drivers) to register with LUO and participate in the live update process
via callbacks.
Subsystem Registration:
- Defines struct liveupdate_subsystem in linux/liveupdate.h,
which subsystems use to provide their name and optional callbacks
(prepare, freeze, cancel, finish). The callbacks accept
a u64 *data intended for passing state/handles.
- Exports liveupdate_register_subsystem() and
liveupdate_unregister_subsystem() API functions.
- Adds drivers/misc/liveupdate/luo_subsystems.c to manage a list
of registered subsystems.
Registration/unregistration is restricted to
specific LUO states (NORMAL/UPDATED).
Callback Framework:
- The main luo_core.c state transition functions
now delegate to new luo_do_subsystems_*_calls() functions
defined in luo_subsystems.c.
- These new functions are intended to iterate through the registered
subsystems and invoke their corresponding callbacks.
FDT Integration:
- Adds a /subsystems subnode within the main LUO FDT created in
luo_core.c. This node has its own compatibility string
(subsystems-v1).
- luo_subsystems_fdt_setup() populates this node by adding a
property for each registered subsystem, using the subsystem's
name.
Currently, these properties are initialized with a placeholder
u64 value (0).
- luo_subsystems_startup() is called from luo_core.c on boot to
find and validate the /subsystems node in the FDT received via
KHO.
- Adds a stub API function liveupdate_get_subsystem_data() intended
for subsystems to retrieve their persisted u64 data from the FDT
in the new kernel.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/liveupdate.h | 66 +++++++
kernel/liveupdate/Makefile | 3 +-
kernel/liveupdate/luo_core.c | 19 +-
kernel/liveupdate/luo_internal.h | 7 +
kernel/liveupdate/luo_subsystems.c | 291 +++++++++++++++++++++++++++++
5 files changed, 383 insertions(+), 3 deletions(-)
create mode 100644 kernel/liveupdate/luo_subsystems.c
diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
index 85a6828c95b0..4c378a986cfe 100644
--- a/include/linux/liveupdate.h
+++ b/include/linux/liveupdate.h
@@ -12,6 +12,52 @@
#include <linux/list.h>
#include <uapi/linux/liveupdate.h>
+struct liveupdate_subsystem;
+
+/**
+ * struct liveupdate_subsystem_ops - LUO events callback functions
+ * @prepare: Optional. Called during LUO prepare phase. Should perform
+ * preparatory actions and can store a u64 handle/state
+ * via the 'data' pointer for use in later callbacks.
+ * Return 0 on success, negative error code on failure.
+ * @freeze: Optional. Called during LUO freeze event (before actual jump
+ * to new kernel). Should perform final state saving actions and
+ * can update the u64 handle/state via the 'data' pointer. Retur:
+ * 0 on success, negative error code on failure.
+ * @cancel: Optional. Called if the live update process is canceled after
+ * prepare (or freeze) was called. Receives the u64 data
+ * set by prepare/freeze. Used for cleanup.
+ * @boot: Optional. Call durng boot post live update. This callback is
+ * done when subsystem register during live update.
+ * @finish: Optional. Called after the live update is finished in the new
+ * kernel.
+ * Receives the u64 data set by prepare/freeze. Used for cleanup.
+ * @owner: Module reference
+ */
+struct liveupdate_subsystem_ops {
+ int (*prepare)(struct liveupdate_subsystem *handle, u64 *data);
+ int (*freeze)(struct liveupdate_subsystem *handle, u64 *data);
+ void (*cancel)(struct liveupdate_subsystem *handle, u64 data);
+ void (*boot)(struct liveupdate_subsystem *handle, u64 data);
+ void (*finish)(struct liveupdate_subsystem *handle, u64 data);
+ struct module *owner;
+};
+
+/**
+ * struct liveupdate_subsystem - Represents a subsystem participating in LUO
+ * @ops: Callback functions
+ * @name: Unique name identifying the subsystem.
+ * @list: List head used internally by LUO. Should not be modified by
+ * caller after registration.
+ * @private_data: For LUO internal use, cached value of data field.
+ */
+struct liveupdate_subsystem {
+ const struct liveupdate_subsystem_ops *ops;
+ const char *name;
+ struct list_head list;
+ u64 private_data;
+};
+
#ifdef CONFIG_LIVEUPDATE
/* Return true if live update orchestrator is enabled */
@@ -33,6 +79,10 @@ bool liveupdate_state_normal(void);
enum liveupdate_state liveupdate_get_state(void);
+int liveupdate_register_subsystem(struct liveupdate_subsystem *h);
+int liveupdate_unregister_subsystem(struct liveupdate_subsystem *h);
+int liveupdate_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data);
+
#else /* CONFIG_LIVEUPDATE */
static inline int liveupdate_reboot(void)
@@ -60,5 +110,21 @@ static inline enum liveupdate_state liveupdate_get_state(void)
return LIVEUPDATE_STATE_NORMAL;
}
+static inline int liveupdate_register_subsystem(struct liveupdate_subsystem *h)
+{
+ return 0;
+}
+
+static inline int liveupdate_unregister_subsystem(struct liveupdate_subsystem *h)
+{
+ return 0;
+}
+
+static inline int liveupdate_get_subsystem_data(struct liveupdate_subsystem *h,
+ u64 *data)
+{
+ return -ENODATA;
+}
+
#endif /* CONFIG_LIVEUPDATE */
#endif /* _LINUX_LIVEUPDATE_H */
diff --git a/kernel/liveupdate/Makefile b/kernel/liveupdate/Makefile
index d90cc3b4bf7b..2881bab0c6df 100644
--- a/kernel/liveupdate/Makefile
+++ b/kernel/liveupdate/Makefile
@@ -2,7 +2,8 @@
luo-y := \
luo_core.o \
- luo_ioctl.o
+ luo_ioctl.o \
+ luo_subsystems.o
obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 10796481447a..92edaeaaad3e 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -130,6 +130,10 @@ static int luo_fdt_setup(void)
if (ret)
goto exit_free;
+ ret = luo_subsystems_fdt_setup(fdt_out);
+ if (ret)
+ goto exit_free;
+
ret = kho_add_subtree(LUO_KHO_ENTRY_NAME, fdt_out);
if (ret)
goto exit_free;
@@ -153,20 +157,30 @@ static void luo_fdt_destroy(void)
static int luo_do_prepare_calls(void)
{
- return 0;
+ int ret;
+
+ ret = luo_do_subsystems_prepare_calls();
+
+ return ret;
}
static int luo_do_freeze_calls(void)
{
- return 0;
+ int ret;
+
+ ret = luo_do_subsystems_freeze_calls();
+
+ return ret;
}
static void luo_do_finish_calls(void)
{
+ luo_do_subsystems_finish_calls();
}
static void luo_do_cancel_calls(void)
{
+ luo_do_subsystems_cancel_calls();
}
static int __luo_prepare(void)
@@ -408,6 +422,7 @@ static int __init luo_startup(void)
}
__luo_set_state(LIVEUPDATE_STATE_UPDATED);
+ luo_subsystems_startup(luo_fdt_in);
return 0;
}
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index c98842caa4a0..c62fbbb0790c 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -32,4 +32,11 @@ void *luo_contig_alloc_preserve(size_t size);
void luo_contig_free_unpreserve(void *mem, size_t size);
void luo_contig_free_restore(void *mem, size_t size);
+void luo_subsystems_startup(void *fdt);
+int luo_subsystems_fdt_setup(void *fdt);
+int luo_do_subsystems_prepare_calls(void);
+int luo_do_subsystems_freeze_calls(void);
+void luo_do_subsystems_finish_calls(void);
+void luo_do_subsystems_cancel_calls(void);
+
#endif /* _LINUX_LUO_INTERNAL_H */
diff --git a/kernel/liveupdate/luo_subsystems.c b/kernel/liveupdate/luo_subsystems.c
new file mode 100644
index 000000000000..69f00d5c000e
--- /dev/null
+++ b/kernel/liveupdate/luo_subsystems.c
@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+/**
+ * DOC: LUO Subsystems support
+ *
+ * Various kernel subsystems register with the Live Update Orchestrator to
+ * participate in the live update process. These subsystems are notified at
+ * different stages of the live update sequence, allowing them to serialize
+ * device state before the reboot and restore it afterwards. Examples include
+ * the device layer, interrupt controllers, KVM, IOMMU, and specific device
+ * drivers.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/err.h>
+#include <linux/libfdt.h>
+#include <linux/liveupdate.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/string.h>
+#include "luo_internal.h"
+
+#define LUO_SUBSYSTEMS_NODE_NAME "subsystems"
+#define LUO_SUBSYSTEMS_COMPATIBLE "subsystems-v1"
+
+static DEFINE_MUTEX(luo_subsystem_list_mutex);
+static LIST_HEAD(luo_subsystems_list);
+static void *luo_fdt_out;
+static void *luo_fdt_in;
+
+/**
+ * luo_subsystems_fdt_setup - Adds and populates the 'subsystems' node in the
+ * FDT.
+ * @fdt: Pointer to the LUO FDT blob.
+ *
+ * Add subsystems node and each subsystem to the LUO FDT blob.
+ *
+ * Returns: 0 on success, negative errno on failure.
+ */
+int luo_subsystems_fdt_setup(void *fdt)
+{
+ struct liveupdate_subsystem *subsystem;
+ const u64 zero_data = 0;
+ int ret, node_offset;
+
+ guard(mutex)(&luo_subsystem_list_mutex);
+ ret = fdt_add_subnode(fdt, 0, LUO_SUBSYSTEMS_NODE_NAME);
+ if (ret < 0)
+ goto exit_error;
+
+ node_offset = ret;
+ ret = fdt_setprop_string(fdt, node_offset, "compatible",
+ LUO_SUBSYSTEMS_COMPATIBLE);
+ if (ret < 0)
+ goto exit_error;
+
+ list_for_each_entry(subsystem, &luo_subsystems_list, list) {
+ ret = fdt_setprop(fdt, node_offset, subsystem->name,
+ &zero_data, sizeof(zero_data));
+ if (ret < 0)
+ goto exit_error;
+ }
+
+ luo_fdt_out = fdt;
+ return 0;
+exit_error:
+ pr_err("Failed to setup 'subsystems' node to FDT: %s\n",
+ fdt_strerror(ret));
+ return -ENOSPC;
+}
+
+/**
+ * luo_subsystems_startup - Validates the LUO subsystems FDT node at startup.
+ * @fdt: Pointer to the LUO FDT blob passed from the previous kernel.
+ *
+ * This __init function checks the existence and validity of the '/subsystems'
+ * node in the FDT. This node is considered mandatory.
+ */
+void __init luo_subsystems_startup(void *fdt)
+{
+ int ret, node_offset;
+
+ guard(mutex)(&luo_subsystem_list_mutex);
+ node_offset = fdt_subnode_offset(fdt, 0, LUO_SUBSYSTEMS_NODE_NAME);
+ if (node_offset < 0)
+ luo_restore_fail("Failed to find /subsystems node\n");
+
+ ret = fdt_node_check_compatible(fdt, node_offset,
+ LUO_SUBSYSTEMS_COMPATIBLE);
+ if (ret) {
+ luo_restore_fail("FDT '%s' is incompatible with '%s' [%d]\n",
+ LUO_SUBSYSTEMS_NODE_NAME,
+ LUO_SUBSYSTEMS_COMPATIBLE, ret);
+ }
+ luo_fdt_in = fdt;
+}
+
+static int luo_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
+{
+ return 0;
+}
+
+/**
+ * luo_do_subsystems_prepare_calls - Calls prepare callbacks and updates FDT
+ * if all prepares succeed. Handles cancellation on failure.
+ *
+ * Phase 1: Calls 'prepare' for all subsystems and stores results temporarily.
+ * If any 'prepare' fails, calls 'cancel' on previously prepared subsystems
+ * and returns the error.
+ * Phase 2: If all 'prepare' calls succeeded, writes the stored data to the FDT.
+ * If any FDT write fails, calls 'cancel' on *all* prepared subsystems and
+ * returns the FDT error.
+ *
+ * Returns: 0 on success. Negative errno on failure.
+ */
+int luo_do_subsystems_prepare_calls(void)
+{
+ return 0;
+}
+
+/**
+ * luo_do_subsystems_freeze_calls - Calls freeze callbacks and updates FDT
+ * if all freezes succeed. Handles cancellation on failure.
+ *
+ * Phase 1: Calls 'freeze' for all subsystems and stores results temporarily.
+ * If any 'freeze' fails, calls 'cancel' on previously called subsystems
+ * and returns the error.
+ * Phase 2: If all 'freeze' calls succeeded, writes the stored data to the FDT.
+ * If any FDT write fails, calls 'cancel' on *all* subsystems and
+ * returns the FDT error.
+ *
+ * Returns: 0 on success. Negative errno on failure.
+ */
+int luo_do_subsystems_freeze_calls(void)
+{
+ return 0;
+}
+
+/**
+ * luo_do_subsystems_finish_calls- Calls finish callbacks for all subsystems.
+ *
+ * This function is called at the end of live update cycle to do the final
+ * clean-up or housekeeping of the post-live update states.
+ */
+void luo_do_subsystems_finish_calls(void)
+{
+}
+
+/**
+ * luo_do_subsystems_cancel_calls - Calls cancel callbacks for all subsystems.
+ *
+ * This function is typically called when the live update process needs to be
+ * aborted externally, for example, after the prepare phase may have run but
+ * before actual reboot. It iterates through all registered subsystems and calls
+ * the 'cancel' callback for those that implement it and likely completed
+ * prepare.
+ */
+void luo_do_subsystems_cancel_calls(void)
+{
+}
+
+/**
+ * liveupdate_register_subsystem - Register a kernel subsystem handler with LUO
+ * @h: Pointer to the liveupdate_subsystem structure allocated and populated
+ * by the calling subsystem.
+ *
+ * Registers a subsystem handler that provides callbacks for different events
+ * of the live update cycle. Registration is typically done during the
+ * subsystem's module init or core initialization.
+ *
+ * Can only be called when LUO is in the NORMAL or UPDATED states.
+ * The provided name (@h->name) must be unique among registered subsystems.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int liveupdate_register_subsystem(struct liveupdate_subsystem *h)
+{
+ struct liveupdate_subsystem *iter;
+ int ret = 0;
+
+ luo_state_read_enter();
+ if (!liveupdate_state_normal() && !liveupdate_state_updated()) {
+ luo_state_read_exit();
+ return -EBUSY;
+ }
+
+ guard(mutex)(&luo_subsystem_list_mutex);
+ list_for_each_entry(iter, &luo_subsystems_list, list) {
+ if (iter == h) {
+ pr_warn("Subsystem '%s' (%p) already registered.\n",
+ h->name, h);
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+
+ if (!strcmp(iter->name, h->name)) {
+ pr_err("Subsystem with name '%s' already registered.\n",
+ h->name);
+ ret = -EEXIST;
+ goto out_unlock;
+ }
+ }
+
+ if (!try_module_get(h->ops->owner)) {
+ pr_warn("Subsystem '%s' unable to get reference.\n", h->name);
+ ret = -EAGAIN;
+ goto out_unlock;
+ }
+
+ INIT_LIST_HEAD(&h->list);
+ list_add_tail(&h->list, &luo_subsystems_list);
+
+out_unlock:
+ /*
+ * If we are booting during live update, and subsystem provided a boot
+ * callback, do it now, since we know that subsystem has already
+ * initialized.
+ */
+ if (!ret && liveupdate_state_updated() && h->ops->boot) {
+ u64 data;
+
+ ret = luo_get_subsystem_data(h, &data);
+ if (!WARN_ON_ONCE(ret))
+ h->ops->boot(h, data);
+ }
+
+ luo_state_read_exit();
+
+ return ret;
+}
+
+/**
+ * liveupdate_unregister_subsystem - Unregister a kernel subsystem handler from
+ * LUO
+ * @h: Pointer to the same liveupdate_subsystem structure that was used during
+ * registration.
+ *
+ * Unregisters a previously registered subsystem handler. Typically called
+ * during module exit or subsystem teardown. LUO removes the structure from its
+ * internal list; the caller is responsible for any necessary memory cleanup
+ * of the structure itself.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ * -EINVAL if h is NULL.
+ * -ENOENT if the specified handler @h is not found in the registration list.
+ * -EBUSY if LUO is not in the NORMAL state.
+ */
+int liveupdate_unregister_subsystem(struct liveupdate_subsystem *h)
+{
+ struct liveupdate_subsystem *iter;
+ bool found = false;
+ int ret = 0;
+
+ luo_state_read_enter();
+ if (!liveupdate_state_normal() && !liveupdate_state_updated()) {
+ luo_state_read_exit();
+ return -EBUSY;
+ }
+
+ guard(mutex)(&luo_subsystem_list_mutex);
+ list_for_each_entry(iter, &luo_subsystems_list, list) {
+ if (iter == h) {
+ found = true;
+ break;
+ }
+ }
+
+ if (found) {
+ list_del_init(&h->list);
+ } else {
+ pr_warn("Subsystem handler '%s' not found for unregistration.\n",
+ h->name);
+ ret = -ENOENT;
+ }
+
+ module_put(h->ops->owner);
+ luo_state_read_exit();
+
+ return ret;
+}
+
+int liveupdate_get_subsystem_data(struct liveupdate_subsystem *h, u64 *data)
+{
+ return 0;
+}
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 08/30] liveupdate: luo_core: integrate with KHO
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Integrate the LUO with the KHO framework to enable passing LUO state
across a kexec reboot.
When LUO is transitioned to a "prepared" state, it tells KHO to
finalize, so all memory segments that were added to KHO preservation
list are getting preserved. After "Prepared" state no new segments
can be preserved. If LUO is canceled, it also tells KHO to cancel the
serialization, and therefore, later LUO can go back into the prepared
state.
This patch introduces the following changes:
- During the KHO finalization phase allocate FDT blob.
- Populate this FDT with a LUO compatibility string ("luo-v1").
LUO now depends on `CONFIG_KEXEC_HANDOVER`. The core state transition
logic (`luo_do_*_calls`) remains unimplemented in this patch.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/liveupdate/luo_core.c | 282 ++++++++++++++++++++++++++++++-
kernel/liveupdate/luo_internal.h | 13 ++
2 files changed, 292 insertions(+), 3 deletions(-)
diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 954d533bd8c4..10796481447a 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -47,9 +47,13 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/err.h>
+#include <linux/kexec_handover.h>
#include <linux/kobject.h>
+#include <linux/libfdt.h>
#include <linux/liveupdate.h>
+#include <linux/mm.h>
#include <linux/rwsem.h>
+#include <linux/sizes.h>
#include <linux/string.h>
#include "luo_internal.h"
@@ -67,6 +71,21 @@ static const char *const luo_state_str[] = {
static bool luo_enabled;
+static void *luo_fdt_out;
+static void *luo_fdt_in;
+
+/*
+ * The LUO FDT size depends on the number of participating subsystems,
+ *
+ * The current fixed size (4K) is large enough to handle reasonable number of
+ * preserved entities. If this size ever becomes insufficient, it can either be
+ * increased, or a dynamic size calculation mechanism could be implemented in
+ * the future.
+ */
+#define LUO_FDT_SIZE PAGE_SIZE
+#define LUO_KHO_ENTRY_NAME "LUO"
+#define LUO_COMPATIBLE "luo-v1"
+
static int __init early_liveupdate_param(char *buf)
{
return kstrtobool(buf, &luo_enabled);
@@ -91,6 +110,52 @@ static inline void luo_set_state(enum liveupdate_state state)
__luo_set_state(state);
}
+/* Called during the prepare phase, to create LUO fdt tree */
+static int luo_fdt_setup(void)
+{
+ void *fdt_out;
+ int ret;
+
+ fdt_out = luo_contig_alloc_preserve(LUO_FDT_SIZE);
+ if (IS_ERR(fdt_out)) {
+ pr_err("failed to allocate/preserve FDT memory\n");
+ return PTR_ERR(fdt_out);
+ }
+
+ ret = fdt_create_empty_tree(fdt_out, LUO_FDT_SIZE);
+ if (ret)
+ goto exit_free;
+
+ ret = fdt_setprop_string(fdt_out, 0, "compatible", LUO_COMPATIBLE);
+ if (ret)
+ goto exit_free;
+
+ ret = kho_add_subtree(LUO_KHO_ENTRY_NAME, fdt_out);
+ if (ret)
+ goto exit_free;
+ luo_fdt_out = fdt_out;
+
+ return 0;
+
+exit_free:
+ luo_contig_free_unpreserve(fdt_out, LUO_FDT_SIZE);
+ pr_err("failed to prepare LUO FDT: %d\n", ret);
+
+ return ret;
+}
+
+static void luo_fdt_destroy(void)
+{
+ kho_remove_subtree(luo_fdt_out);
+ luo_contig_free_unpreserve(luo_fdt_out, LUO_FDT_SIZE);
+ luo_fdt_out = NULL;
+}
+
+static int luo_do_prepare_calls(void)
+{
+ return 0;
+}
+
static int luo_do_freeze_calls(void)
{
return 0;
@@ -100,6 +165,71 @@ static void luo_do_finish_calls(void)
{
}
+static void luo_do_cancel_calls(void)
+{
+}
+
+static int __luo_prepare(void)
+{
+ int ret;
+
+ if (down_write_killable(&luo_state_rwsem)) {
+ pr_warn("[prepare] event canceled by user\n");
+ return -EAGAIN;
+ }
+
+ if (!is_current_luo_state(LIVEUPDATE_STATE_NORMAL)) {
+ pr_warn("Can't switch to [%s] from [%s] state\n",
+ luo_state_str[LIVEUPDATE_STATE_PREPARED],
+ luo_current_state_str());
+ ret = -EINVAL;
+ goto exit_unlock;
+ }
+
+ ret = luo_fdt_setup();
+ if (ret)
+ goto exit_unlock;
+
+ ret = luo_do_prepare_calls();
+ if (ret) {
+ luo_fdt_destroy();
+ goto exit_unlock;
+ }
+
+ luo_set_state(LIVEUPDATE_STATE_PREPARED);
+
+exit_unlock:
+ up_write(&luo_state_rwsem);
+
+ return ret;
+}
+
+static int __luo_cancel(void)
+{
+ if (down_write_killable(&luo_state_rwsem)) {
+ pr_warn("[cancel] event canceled by user\n");
+ return -EAGAIN;
+ }
+
+ if (!is_current_luo_state(LIVEUPDATE_STATE_PREPARED) &&
+ !is_current_luo_state(LIVEUPDATE_STATE_FROZEN)) {
+ pr_warn("Can't switch to [%s] from [%s] state\n",
+ luo_state_str[LIVEUPDATE_STATE_NORMAL],
+ luo_current_state_str());
+ up_write(&luo_state_rwsem);
+
+ return -EINVAL;
+ }
+
+ luo_do_cancel_calls();
+ luo_fdt_destroy();
+ luo_set_state(LIVEUPDATE_STATE_NORMAL);
+
+ up_write(&luo_state_rwsem);
+
+ return 0;
+}
+
/* Get the current state as a string */
const char *luo_current_state_str(void)
{
@@ -111,9 +241,28 @@ enum liveupdate_state liveupdate_get_state(void)
return READ_ONCE(luo_state);
}
+/**
+ * luo_prepare - Initiate the live update preparation phase.
+ *
+ * This function is called to begin the live update process. It attempts to
+ * transition the luo to the ``LIVEUPDATE_STATE_PREPARED`` state.
+ *
+ * If the calls complete successfully, the orchestrator state is set
+ * to ``LIVEUPDATE_STATE_PREPARED``. If any call fails a
+ * ``LIVEUPDATE_CANCEL`` is sent to roll back any actions.
+ *
+ * @return 0 on success, ``-EAGAIN`` if the state change was cancelled by the
+ * user while waiting for the lock, ``-EINVAL`` if the orchestrator is not in
+ * the normal state, or a negative error code returned by the calls.
+ */
int luo_prepare(void)
{
- return 0;
+ int err = __luo_prepare();
+
+ if (err)
+ return err;
+
+ return kho_finalize();
}
/**
@@ -193,9 +342,28 @@ int luo_finish(void)
return 0;
}
+/**
+ * luo_cancel - Cancel the ongoing live update from prepared or frozen states.
+ *
+ * This function is called to abort a live update that is currently in the
+ * ``LIVEUPDATE_STATE_PREPARED`` state.
+ *
+ * If the state is correct, it triggers the ``LIVEUPDATE_CANCEL`` notifier chain
+ * to allow subsystems to undo any actions performed during the prepare or
+ * freeze events. Finally, the orchestrator state is transitioned back to
+ * ``LIVEUPDATE_STATE_NORMAL``.
+ *
+ * @return 0 on success, or ``-EAGAIN`` if the state change was cancelled by the
+ * user while waiting for the lock.
+ */
int luo_cancel(void)
{
- return 0;
+ int err = kho_abort();
+
+ if (err)
+ return err;
+
+ return __luo_cancel();
}
void luo_state_read_enter(void)
@@ -210,7 +378,36 @@ void luo_state_read_exit(void)
static int __init luo_startup(void)
{
- __luo_set_state(LIVEUPDATE_STATE_NORMAL);
+ phys_addr_t fdt_phys;
+ int ret;
+
+ if (!kho_is_enabled()) {
+ if (luo_enabled)
+ pr_warn("Disabling liveupdate because KHO is disabled\n");
+ luo_enabled = false;
+ return 0;
+ }
+
+ /* Retrieve LUO subtree, and verify its format. */
+ ret = kho_retrieve_subtree(LUO_KHO_ENTRY_NAME, &fdt_phys);
+ if (ret) {
+ if (ret != -ENOENT) {
+ luo_restore_fail("failed to retrieve FDT '%s' from KHO: %d\n",
+ LUO_KHO_ENTRY_NAME, ret);
+ }
+ __luo_set_state(LIVEUPDATE_STATE_NORMAL);
+
+ return 0;
+ }
+
+ luo_fdt_in = __va(fdt_phys);
+ ret = fdt_node_check_compatible(luo_fdt_in, 0, LUO_COMPATIBLE);
+ if (ret) {
+ luo_restore_fail("FDT '%s' is incompatible with '%s' [%d]\n",
+ LUO_KHO_ENTRY_NAME, LUO_COMPATIBLE, ret);
+ }
+
+ __luo_set_state(LIVEUPDATE_STATE_UPDATED);
return 0;
}
@@ -295,3 +492,82 @@ bool liveupdate_enabled(void)
{
return luo_enabled;
}
+
+/**
+ * luo_contig_alloc_preserve - Allocate, zero, and preserve contiguous memory.
+ * @size: The number of bytes to allocate.
+ *
+ * Allocates a physically contiguous block of zeroed pages that is large
+ * enough to hold @size bytes. The allocated memory is then registered with
+ * KHO for preservation across a kexec.
+ *
+ * Note: The actual allocated size will be rounded up to the nearest
+ * power-of-two page boundary.
+ *
+ * @return A virtual pointer to the allocated and preserved memory on success,
+ * or an ERR_PTR() encoded error on failure.
+ */
+void *luo_contig_alloc_preserve(size_t size)
+{
+ int order, ret;
+ void *mem;
+
+ if (!size)
+ return ERR_PTR(-EINVAL);
+
+ order = get_order(size);
+ if (order > MAX_PAGE_ORDER)
+ return ERR_PTR(-E2BIG);
+
+ mem = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, order);
+ if (!mem)
+ return ERR_PTR(-ENOMEM);
+
+ ret = kho_preserve_pages(virt_to_page(mem), 1 << order);
+ if (ret) {
+ free_pages((unsigned long)mem, order);
+ return ERR_PTR(ret);
+ }
+
+ return mem;
+}
+
+/**
+ * luo_contig_free_unpreserve - Unpreserve and free contiguous memory.
+ * @mem: Pointer to the memory allocated by luo_contig_alloc_preserve().
+ * @size: The original size requested during allocation. This is used to
+ * recalculate the correct order for freeing the pages.
+ *
+ * Unregisters the memory from KHO preservation and frees the underlying
+ * pages back to the system. This function should be called to clean up
+ * memory allocated with luo_contig_alloc_preserve().
+ */
+void luo_contig_free_unpreserve(void *mem, size_t size)
+{
+ unsigned int order;
+
+ if (!mem || !size)
+ return;
+
+ order = get_order(size);
+ if (WARN_ON_ONCE(order > MAX_PAGE_ORDER))
+ return;
+
+ WARN_ON_ONCE(kho_unpreserve_pages(virt_to_page(mem), 1 << order));
+ free_pages((unsigned long)mem, order);
+}
+
+void luo_contig_free_restore(void *mem, size_t size)
+{
+ unsigned int order;
+
+ if (!mem || !size)
+ return;
+
+ order = get_order(size);
+ if (WARN_ON_ONCE(order > MAX_PAGE_ORDER))
+ return;
+
+ WARN_ON_ONCE(!kho_restore_pages(__pa(mem), 1 << order));
+ free_pages((unsigned long)mem, order);
+}
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
index 2e0861781673..c98842caa4a0 100644
--- a/kernel/liveupdate/luo_internal.h
+++ b/kernel/liveupdate/luo_internal.h
@@ -8,6 +8,15 @@
#ifndef _LINUX_LUO_INTERNAL_H
#define _LINUX_LUO_INTERNAL_H
+/*
+ * Handles a deserialization failure: devices and memory is in unpredictable
+ * state.
+ *
+ * Continuing the boot process after a failure is dangerous because it could
+ * lead to leaks of private data.
+ */
+#define luo_restore_fail(__fmt, ...) panic(__fmt, ##__VA_ARGS__)
+
int luo_cancel(void);
int luo_prepare(void);
int luo_freeze(void);
@@ -19,4 +28,8 @@ extern struct rw_semaphore luo_state_rwsem;
const char *luo_current_state_str(void);
+void *luo_contig_alloc_preserve(size_t size);
+void luo_contig_free_unpreserve(void *mem, size_t size);
+void luo_contig_free_restore(void *mem, size_t size);
+
#endif /* _LINUX_LUO_INTERNAL_H */
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 07/30] liveupdate: luo_core: luo_ioctl: Live Update Orchestrator
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Introduce LUO, a mechanism intended to facilitate kernel updates while
keeping designated devices operational across the transition (e.g., via
kexec). The primary use case is updating hypervisors with minimal
disruption to running virtual machines. For userspace side of hypervisor
update we have copyless migration. LUO is for updating the kernel.
This initial patch lays the groundwork for the LUO subsystem.
Further functionality, including the implementation of state transition
logic, integration with KHO, and hooks for subsystems and file
descriptors, will be added in subsequent patches.
Create a character device at /dev/liveupdate.
A new uAPI header, <uapi/linux/liveupdate.h>, will define the necessary
structures. The magic number for IOCTL is registered in
Documentation/userspace-api/ioctl/ioctl-number.rst.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
.../userspace-api/ioctl/ioctl-number.rst | 2 +
include/linux/liveupdate.h | 64 ++++
include/uapi/linux/liveupdate.h | 94 ++++++
kernel/liveupdate/Kconfig | 27 ++
kernel/liveupdate/Makefile | 6 +
kernel/liveupdate/luo_core.c | 297 ++++++++++++++++++
kernel/liveupdate/luo_internal.h | 22 ++
kernel/liveupdate/luo_ioctl.c | 54 ++++
8 files changed, 566 insertions(+)
create mode 100644 include/linux/liveupdate.h
create mode 100644 include/uapi/linux/liveupdate.h
create mode 100644 kernel/liveupdate/luo_core.c
create mode 100644 kernel/liveupdate/luo_internal.h
create mode 100644 kernel/liveupdate/luo_ioctl.c
diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index 7c527a01d1cf..7232b3544cec 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -385,6 +385,8 @@ Code Seq# Include File Comments
0xB8 01-02 uapi/misc/mrvl_cn10k_dpi.h Marvell CN10K DPI driver
0xB8 all uapi/linux/mshv.h Microsoft Hyper-V /dev/mshv driver
<mailto:linux-hyperv@vger.kernel.org>
+0xBA 00-0F uapi/linux/liveupdate.h Pasha Tatashin
+ <mailto:pasha.tatashin@soleen.com>
0xC0 00-0F linux/usb/iowarrior.h
0xCA 00-0F uapi/misc/cxl.h Dead since 6.15
0xCA 10-2F uapi/misc/ocxl.h
diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h
new file mode 100644
index 000000000000..85a6828c95b0
--- /dev/null
+++ b/include/linux/liveupdate.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+#ifndef _LINUX_LIVEUPDATE_H
+#define _LINUX_LIVEUPDATE_H
+
+#include <linux/bug.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <uapi/linux/liveupdate.h>
+
+#ifdef CONFIG_LIVEUPDATE
+
+/* Return true if live update orchestrator is enabled */
+bool liveupdate_enabled(void);
+
+/* Called during reboot to tell participants to complete serialization */
+int liveupdate_reboot(void);
+
+/*
+ * Return true if machine is in updated state (i.e. live update boot in
+ * progress)
+ */
+bool liveupdate_state_updated(void);
+
+/*
+ * Return true if machine is in normal state (i.e. no live update in progress).
+ */
+bool liveupdate_state_normal(void);
+
+enum liveupdate_state liveupdate_get_state(void);
+
+#else /* CONFIG_LIVEUPDATE */
+
+static inline int liveupdate_reboot(void)
+{
+ return 0;
+}
+
+static inline bool liveupdate_enabled(void)
+{
+ return false;
+}
+
+static inline bool liveupdate_state_updated(void)
+{
+ return false;
+}
+
+static inline bool liveupdate_state_normal(void)
+{
+ return true;
+}
+
+static inline enum liveupdate_state liveupdate_get_state(void)
+{
+ return LIVEUPDATE_STATE_NORMAL;
+}
+
+#endif /* CONFIG_LIVEUPDATE */
+#endif /* _LINUX_LIVEUPDATE_H */
diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h
new file mode 100644
index 000000000000..3cb09b2c4353
--- /dev/null
+++ b/include/uapi/linux/liveupdate.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+/*
+ * Userspace interface for /dev/liveupdate
+ * Live Update Orchestrator
+ *
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#ifndef _UAPI_LIVEUPDATE_H
+#define _UAPI_LIVEUPDATE_H
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+/**
+ * enum liveupdate_state - Defines the possible states of the live update
+ * orchestrator.
+ * @LIVEUPDATE_STATE_UNDEFINED: State has not yet been initialized.
+ * @LIVEUPDATE_STATE_NORMAL: Default state, no live update in progress.
+ * @LIVEUPDATE_STATE_PREPARED: Live update is prepared for reboot; the
+ * LIVEUPDATE_PREPARE callbacks have completed
+ * successfully.
+ * Devices might operate in a limited state
+ * for example the participating devices might
+ * not be allowed to unbind, and also the
+ * setting up of new DMA mappings might be
+ * disabled in this state.
+ * @LIVEUPDATE_STATE_FROZEN: The final reboot event
+ * (%LIVEUPDATE_FREEZE) has been sent, and the
+ * system is performing its final state saving
+ * within the "blackout window". User
+ * workloads must be suspended. The actual
+ * reboot (kexec) into the next kernel is
+ * imminent.
+ * @LIVEUPDATE_STATE_UPDATED: The system has rebooted into the next
+ * kernel via live update the system is now
+ * running the next kernel, awaiting the
+ * finish event.
+ *
+ * These states track the progress and outcome of a live update operation.
+ */
+enum liveupdate_state {
+ LIVEUPDATE_STATE_UNDEFINED = 0,
+ LIVEUPDATE_STATE_NORMAL = 1,
+ LIVEUPDATE_STATE_PREPARED = 2,
+ LIVEUPDATE_STATE_FROZEN = 3,
+ LIVEUPDATE_STATE_UPDATED = 4,
+};
+
+/**
+ * enum liveupdate_event - Events that trigger live update callbacks.
+ * @LIVEUPDATE_PREPARE: PREPARE should happen *before* the blackout window.
+ * Subsystems should prepare for an upcoming reboot by
+ * serializing their states. However, it must be considered
+ * that user applications, e.g. virtual machines are still
+ * running during this phase.
+ * @LIVEUPDATE_FREEZE: FREEZE sent from the reboot() syscall, when the current
+ * kernel is on its way out. This is the final opportunity
+ * for subsystems to save any state that must persist
+ * across the reboot. Callbacks for this event should be as
+ * fast as possible since they are on the critical path of
+ * rebooting into the next kernel.
+ * @LIVEUPDATE_FINISH: FINISH is sent in the newly booted kernel after a
+ * successful live update and normally *after* the blackout
+ * window. Subsystems should perform any final cleanup
+ * during this phase. This phase also provides an
+ * opportunity to clean up devices that were preserved but
+ * never explicitly reclaimed during the live update
+ * process. State restoration should have already occurred
+ * before this event. Callbacks for this event must not
+ * fail. The completion of this call transitions the
+ * machine from ``updated`` to ``normal`` state.
+ * @LIVEUPDATE_CANCEL: CANCEL the live update and go back to normal state. This
+ * event is user initiated, or is done automatically when
+ * LIVEUPDATE_PREPARE or LIVEUPDATE_FREEZE stage fails.
+ * Subsystems should revert any actions taken during the
+ * corresponding prepare event. Callbacks for this event
+ * must not fail.
+ *
+ * These events represent the different stages and actions within the live
+ * update process that subsystems (like device drivers and bus drivers)
+ * need to be aware of to correctly serialize and restore their state.
+ *
+ */
+enum liveupdate_event {
+ LIVEUPDATE_PREPARE = 0,
+ LIVEUPDATE_FREEZE = 1,
+ LIVEUPDATE_FINISH = 2,
+ LIVEUPDATE_CANCEL = 3,
+};
+
+#endif /* _UAPI_LIVEUPDATE_H */
diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig
index eebe564b385d..f6b0bde188d9 100644
--- a/kernel/liveupdate/Kconfig
+++ b/kernel/liveupdate/Kconfig
@@ -1,7 +1,34 @@
# SPDX-License-Identifier: GPL-2.0-only
+#
+# Copyright (c) 2025, Google LLC.
+# Pasha Tatashin <pasha.tatashin@soleen.com>
+#
+# Live Update Orchestrator
+#
menu "Live Update"
+config LIVEUPDATE
+ bool "Live Update Orchestrator"
+ depends on KEXEC_HANDOVER
+ help
+ Enable the Live Update Orchestrator. Live Update is a mechanism,
+ typically based on kexec, that allows the kernel to be updated
+ while keeping selected devices operational across the transition.
+ These devices are intended to be reclaimed by the new kernel and
+ re-attached to their original workload without requiring a device
+ reset.
+
+ Ability to handover a device from current to the next kernel depends
+ on specific support within device drivers and related kernel
+ subsystems.
+
+ This feature primarily targets virtual machine hosts to quickly update
+ the kernel hypervisor with minimal disruption to the running virtual
+ machines.
+
+ If unsure, say N.
+
config KEXEC_HANDOVER
bool "kexec handover"
depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
diff --git a/kernel/liveupdate/Makefile b/kernel/liveupdate/Makefile
index 67c7f71b33fa..d90cc3b4bf7b 100644
--- a/kernel/liveupdate/Makefile
+++ b/kernel/liveupdate/Makefile
@@ -1,4 +1,10 @@
# SPDX-License-Identifier: GPL-2.0
+luo-y := \
+ luo_core.o \
+ luo_ioctl.o
+
obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
+
+obj-$(CONFIG_LIVEUPDATE) += luo.o
diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
new file mode 100644
index 000000000000..954d533bd8c4
--- /dev/null
+++ b/kernel/liveupdate/luo_core.c
@@ -0,0 +1,297 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+/**
+ * DOC: Live Update Orchestrator (LUO)
+ *
+ * Live Update is a specialized, kexec-based reboot process that allows a
+ * running kernel to be updated from one version to another while preserving
+ * the state of selected resources and keeping designated hardware devices
+ * operational. For these devices, DMA activity may continue throughout the
+ * kernel transition.
+ *
+ * While the primary use case driving this work is supporting live updates of
+ * the Linux kernel when it is used as a hypervisor in cloud environments, the
+ * LUO framework itself is designed to be workload-agnostic. Much like Kernel
+ * Live Patching, which applies security fixes regardless of the workload,
+ * Live Update facilitates a full kernel version upgrade for any type of system.
+ *
+ * For example, a non-hypervisor system running an in-memory cache like
+ * memcached with many gigabytes of data can use LUO. The userspace service
+ * can place its cache into a memfd, have its state preserved by LUO, and
+ * restore it immediately after the kernel kexec.
+ *
+ * Whether the system is running virtual machines, containers, a
+ * high-performance database, or networking services, LUO's primary goal is to
+ * enable a full kernel update by preserving critical userspace state and
+ * keeping essential devices operational.
+ *
+ * The core of LUO is a state machine that tracks the progress of a live update,
+ * along with a callback API that allows other kernel subsystems to participate
+ * in the process. Example subsystems that can hook into LUO include: kvm,
+ * iommu, interrupts, vfio, participating filesystems, and memory management.
+ *
+ * LUO uses Kexec Handover to transfer memory state from the current kernel to
+ * the next kernel. For more details see
+ * Documentation/core-api/kho/concepts.rst.
+ *
+ * The LUO state machine ensures that operations are performed in the correct
+ * sequence and provides a mechanism to track and recover from potential
+ * failures.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/err.h>
+#include <linux/kobject.h>
+#include <linux/liveupdate.h>
+#include <linux/rwsem.h>
+#include <linux/string.h>
+#include "luo_internal.h"
+
+DECLARE_RWSEM(luo_state_rwsem);
+
+static enum liveupdate_state luo_state = LIVEUPDATE_STATE_UNDEFINED;
+
+static const char *const luo_state_str[] = {
+ [LIVEUPDATE_STATE_UNDEFINED] = "undefined",
+ [LIVEUPDATE_STATE_NORMAL] = "normal",
+ [LIVEUPDATE_STATE_PREPARED] = "prepared",
+ [LIVEUPDATE_STATE_FROZEN] = "frozen",
+ [LIVEUPDATE_STATE_UPDATED] = "updated",
+};
+
+static bool luo_enabled;
+
+static int __init early_liveupdate_param(char *buf)
+{
+ return kstrtobool(buf, &luo_enabled);
+}
+early_param("liveupdate", early_liveupdate_param);
+
+/* Return true if the current state is equal to the provided state */
+static inline bool is_current_luo_state(enum liveupdate_state expected_state)
+{
+ return liveupdate_get_state() == expected_state;
+}
+
+static void __luo_set_state(enum liveupdate_state state)
+{
+ WRITE_ONCE(luo_state, state);
+}
+
+static inline void luo_set_state(enum liveupdate_state state)
+{
+ pr_info("Switched from [%s] to [%s] state\n",
+ luo_current_state_str(), luo_state_str[state]);
+ __luo_set_state(state);
+}
+
+static int luo_do_freeze_calls(void)
+{
+ return 0;
+}
+
+static void luo_do_finish_calls(void)
+{
+}
+
+/* Get the current state as a string */
+const char *luo_current_state_str(void)
+{
+ return luo_state_str[liveupdate_get_state()];
+}
+
+enum liveupdate_state liveupdate_get_state(void)
+{
+ return READ_ONCE(luo_state);
+}
+
+int luo_prepare(void)
+{
+ return 0;
+}
+
+/**
+ * luo_freeze() - Initiate the final freeze notification phase for live update.
+ *
+ * Attempts to transition the live update orchestrator state from
+ * %LIVEUPDATE_STATE_PREPARED to %LIVEUPDATE_STATE_FROZEN. This function is
+ * typically called just before the actual reboot system call (e.g., kexec)
+ * is invoked, either directly by the orchestration tool or potentially from
+ * within the reboot syscall path itself.
+ *
+ * @return 0: Success. Negative error otherwise. State is reverted to
+ * %LIVEUPDATE_STATE_NORMAL in case of an error during callbacks, and everything
+ * is canceled via cancel notifcation.
+ */
+int luo_freeze(void)
+{
+ int ret;
+
+ if (down_write_killable(&luo_state_rwsem)) {
+ pr_warn("[freeze] event canceled by user\n");
+ return -EAGAIN;
+ }
+
+ if (!is_current_luo_state(LIVEUPDATE_STATE_PREPARED)) {
+ pr_warn("Can't switch to [%s] from [%s] state\n",
+ luo_state_str[LIVEUPDATE_STATE_FROZEN],
+ luo_current_state_str());
+ up_write(&luo_state_rwsem);
+
+ return -EINVAL;
+ }
+
+ ret = luo_do_freeze_calls();
+ if (!ret)
+ luo_set_state(LIVEUPDATE_STATE_FROZEN);
+ else
+ luo_set_state(LIVEUPDATE_STATE_NORMAL);
+
+ up_write(&luo_state_rwsem);
+
+ return ret;
+}
+
+/**
+ * luo_finish - Finalize the live update process in the new kernel.
+ *
+ * This function is called after a successful live update reboot into a new
+ * kernel, once the new kernel is ready to transition to the normal operational
+ * state. It signals the completion of the live update sequence to subsystems.
+ *
+ * @return 0 on success, ``-EAGAIN`` if the state change was cancelled by the
+ * user while waiting for the lock, or ``-EINVAL`` if the orchestrator is not in
+ * the updated state.
+ */
+int luo_finish(void)
+{
+ if (down_write_killable(&luo_state_rwsem)) {
+ pr_warn("[finish] event canceled by user\n");
+ return -EAGAIN;
+ }
+
+ if (!is_current_luo_state(LIVEUPDATE_STATE_UPDATED)) {
+ pr_warn("Can't switch to [%s] from [%s] state\n",
+ luo_state_str[LIVEUPDATE_STATE_NORMAL],
+ luo_current_state_str());
+ up_write(&luo_state_rwsem);
+
+ return -EINVAL;
+ }
+
+ luo_do_finish_calls();
+ luo_set_state(LIVEUPDATE_STATE_NORMAL);
+
+ up_write(&luo_state_rwsem);
+
+ return 0;
+}
+
+int luo_cancel(void)
+{
+ return 0;
+}
+
+void luo_state_read_enter(void)
+{
+ down_read(&luo_state_rwsem);
+}
+
+void luo_state_read_exit(void)
+{
+ up_read(&luo_state_rwsem);
+}
+
+static int __init luo_startup(void)
+{
+ __luo_set_state(LIVEUPDATE_STATE_NORMAL);
+
+ return 0;
+}
+early_initcall(luo_startup);
+
+/* Public Functions */
+
+/**
+ * liveupdate_reboot() - Kernel reboot notifier for live update final
+ * serialization.
+ *
+ * This function is invoked directly from the reboot() syscall pathway if a
+ * reboot is initiated while the live update state is %LIVEUPDATE_STATE_PREPARED
+ * (i.e., if the user did not explicitly trigger the frozen state). It handles
+ * the implicit transition into the final frozen state.
+ *
+ * It triggers the %LIVEUPDATE_REBOOT event callbacks for participating
+ * subsystems. These callbacks must perform final state saving very quickly as
+ * they execute during the blackout period just before kexec.
+ *
+ * If any %LIVEUPDATE_FREEZE callback fails, this function triggers the
+ * %LIVEUPDATE_CANCEL event for all participants to revert their state, aborts
+ * the live update, and returns an error.
+ */
+int liveupdate_reboot(void)
+{
+ if (!is_current_luo_state(LIVEUPDATE_STATE_PREPARED))
+ return 0;
+
+ return luo_freeze();
+}
+
+/**
+ * liveupdate_state_updated - Check if the system is in the live update
+ * 'updated' state.
+ *
+ * This function checks if the live update orchestrator is in the
+ * ``LIVEUPDATE_STATE_UPDATED`` state. This state indicates that the system has
+ * successfully rebooted into a new kernel as part of a live update, and the
+ * preserved devices are expected to be in the process of being reclaimed.
+ *
+ * This is typically used by subsystems during early boot of the new kernel
+ * to determine if they need to attempt to restore state from a previous
+ * live update.
+ *
+ * @return true if the system is in the ``LIVEUPDATE_STATE_UPDATED`` state,
+ * false otherwise.
+ */
+bool liveupdate_state_updated(void)
+{
+ return is_current_luo_state(LIVEUPDATE_STATE_UPDATED);
+}
+
+/**
+ * liveupdate_state_normal - Check if the system is in the live update 'normal'
+ * state.
+ *
+ * This function checks if the live update orchestrator is in the
+ * ``LIVEUPDATE_STATE_NORMAL`` state. This state indicates that no live update
+ * is in progress. It represents the default operational state of the system.
+ *
+ * This can be used to gate actions that should only be performed when no
+ * live update activity is occurring.
+ *
+ * @return true if the system is in the ``LIVEUPDATE_STATE_NORMAL`` state,
+ * false otherwise.
+ */
+bool liveupdate_state_normal(void)
+{
+ return is_current_luo_state(LIVEUPDATE_STATE_NORMAL);
+}
+
+/**
+ * liveupdate_enabled - Check if the live update feature is enabled.
+ *
+ * This function returns the state of the live update feature flag, which
+ * can be controlled via the ``liveupdate`` kernel command-line parameter.
+ *
+ * @return true if live update is enabled, false otherwise.
+ */
+bool liveupdate_enabled(void)
+{
+ return luo_enabled;
+}
diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h
new file mode 100644
index 000000000000..2e0861781673
--- /dev/null
+++ b/kernel/liveupdate/luo_internal.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#ifndef _LINUX_LUO_INTERNAL_H
+#define _LINUX_LUO_INTERNAL_H
+
+int luo_cancel(void);
+int luo_prepare(void);
+int luo_freeze(void);
+int luo_finish(void);
+
+void luo_state_read_enter(void);
+void luo_state_read_exit(void);
+extern struct rw_semaphore luo_state_rwsem;
+
+const char *luo_current_state_str(void);
+
+#endif /* _LINUX_LUO_INTERNAL_H */
diff --git a/kernel/liveupdate/luo_ioctl.c b/kernel/liveupdate/luo_ioctl.c
new file mode 100644
index 000000000000..fc2afb450ad5
--- /dev/null
+++ b/kernel/liveupdate/luo_ioctl.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/liveupdate.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <uapi/linux/liveupdate.h>
+#include "luo_internal.h"
+
+struct luo_device_state {
+ struct miscdevice miscdev;
+};
+
+static const struct file_operations luo_fops = {
+ .owner = THIS_MODULE,
+};
+
+static struct luo_device_state luo_dev = {
+ .miscdev = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "liveupdate",
+ .fops = &luo_fops,
+ },
+};
+
+static int __init liveupdate_init(void)
+{
+ if (!liveupdate_enabled())
+ return 0;
+
+ return misc_register(&luo_dev.miscdev);
+}
+module_init(liveupdate_init);
+
+static void __exit liveupdate_exit(void)
+{
+ misc_deregister(&luo_dev.miscdev);
+}
+module_exit(liveupdate_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Pasha Tatashin");
+MODULE_DESCRIPTION("Live Update Orchestrator");
+MODULE_VERSION("0.1");
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 06/30] liveupdate: kho: move to kernel/liveupdate
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Move KHO to kernel/liveupdate/ in preparation of placing all Live Update
core kernel related files to the same place.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
---
Documentation/core-api/kho/concepts.rst | 2 +-
MAINTAINERS | 2 +-
init/Kconfig | 2 ++
kernel/Kconfig.kexec | 25 ----------------
kernel/Makefile | 3 +-
kernel/liveupdate/Kconfig | 30 +++++++++++++++++++
kernel/liveupdate/Makefile | 4 +++
kernel/{ => liveupdate}/kexec_handover.c | 6 ++--
.../{ => liveupdate}/kexec_handover_debug.c | 0
.../kexec_handover_internal.h | 0
10 files changed, 42 insertions(+), 32 deletions(-)
create mode 100644 kernel/liveupdate/Kconfig
create mode 100644 kernel/liveupdate/Makefile
rename kernel/{ => liveupdate}/kexec_handover.c (99%)
rename kernel/{ => liveupdate}/kexec_handover_debug.c (100%)
rename kernel/{ => liveupdate}/kexec_handover_internal.h (100%)
diff --git a/Documentation/core-api/kho/concepts.rst b/Documentation/core-api/kho/concepts.rst
index 36d5c05cfb30..d626d1dbd678 100644
--- a/Documentation/core-api/kho/concepts.rst
+++ b/Documentation/core-api/kho/concepts.rst
@@ -70,5 +70,5 @@ in the FDT. That state is called the KHO finalization phase.
Public API
==========
-.. kernel-doc:: kernel/kexec_handover.c
+.. kernel-doc:: kernel/liveupdate/kexec_handover.c
:export:
diff --git a/MAINTAINERS b/MAINTAINERS
index a6cbcc7fb396..e5c800ed4819 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13766,7 +13766,7 @@ S: Maintained
F: Documentation/admin-guide/mm/kho.rst
F: Documentation/core-api/kho/*
F: include/linux/kexec_handover.h
-F: kernel/kexec_handover*
+F: kernel/liveupdate/kexec_handover*
F: tools/testing/selftests/kho/
KEYS-ENCRYPTED
diff --git a/init/Kconfig b/init/Kconfig
index d295e79d3547..9952c112154f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2138,6 +2138,8 @@ config TRACEPOINTS
source "kernel/Kconfig.kexec"
+source "kernel/liveupdate/Kconfig"
+
endmenu # General setup
source "arch/Kconfig"
diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
index e68156d8c72b..15632358bcf7 100644
--- a/kernel/Kconfig.kexec
+++ b/kernel/Kconfig.kexec
@@ -94,31 +94,6 @@ config KEXEC_JUMP
Jump between original kernel and kexeced kernel and invoke
code in physical address mode via KEXEC
-config KEXEC_HANDOVER
- bool "kexec handover"
- depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
- depends on !DEFERRED_STRUCT_PAGE_INIT
- select MEMBLOCK_KHO_SCRATCH
- select KEXEC_FILE
- select DEBUG_FS
- select LIBFDT
- select CMA
- help
- Allow kexec to hand over state across kernels by generating and
- passing additional metadata to the target kernel. This is useful
- to keep data or state alive across the kexec. For this to work,
- both source and target kernels need to have this option enabled.
-
-config KEXEC_HANDOVER_DEBUG
- bool "kexec handover debug interface"
- depends on KEXEC_HANDOVER
- depends on DEBUG_FS
- help
- Allow to control kexec handover device tree via debugfs
- interface, i.e. finalize the state or aborting the finalization.
- Also, enables inspecting the KHO fdt trees with the debugfs binary
- blobs.
-
config CRASH_DUMP
bool "kernel crash dumps"
default ARCH_DEFAULT_CRASH_DUMP
diff --git a/kernel/Makefile b/kernel/Makefile
index 9fe722305c9b..e83669841b8c 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -52,6 +52,7 @@ obj-y += printk/
obj-y += irq/
obj-y += rcu/
obj-y += livepatch/
+obj-y += liveupdate/
obj-y += dma/
obj-y += entry/
obj-y += unwind/
@@ -82,8 +83,6 @@ obj-$(CONFIG_CRASH_DUMP_KUNIT_TEST) += crash_core_test.o
obj-$(CONFIG_KEXEC) += kexec.o
obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
-obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
-obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup/
diff --git a/kernel/liveupdate/Kconfig b/kernel/liveupdate/Kconfig
new file mode 100644
index 000000000000..eebe564b385d
--- /dev/null
+++ b/kernel/liveupdate/Kconfig
@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menu "Live Update"
+
+config KEXEC_HANDOVER
+ bool "kexec handover"
+ depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
+ depends on !DEFERRED_STRUCT_PAGE_INIT
+ select MEMBLOCK_KHO_SCRATCH
+ select KEXEC_FILE
+ select DEBUG_FS
+ select LIBFDT
+ select CMA
+ help
+ Allow kexec to hand over state across kernels by generating and
+ passing additional metadata to the target kernel. This is useful
+ to keep data or state alive across the kexec. For this to work,
+ both source and target kernels need to have this option enabled.
+
+config KEXEC_HANDOVER_DEBUG
+ bool "kexec handover debug interface"
+ depends on KEXEC_HANDOVER
+ depends on DEBUG_FS
+ help
+ Allow to control kexec handover device tree via debugfs
+ interface, i.e. finalize the state or aborting the finalization.
+ Also, enables inspecting the KHO fdt trees with the debugfs binary
+ blobs.
+
+endmenu
diff --git a/kernel/liveupdate/Makefile b/kernel/liveupdate/Makefile
new file mode 100644
index 000000000000..67c7f71b33fa
--- /dev/null
+++ b/kernel/liveupdate/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
diff --git a/kernel/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
similarity index 99%
rename from kernel/kexec_handover.c
rename to kernel/liveupdate/kexec_handover.c
index 61b31cfc75f2..71e98c44cf47 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -24,8 +24,8 @@
* KHO is tightly coupled with mm init and needs access to some of mm
* internal APIs.
*/
-#include "../mm/internal.h"
-#include "kexec_internal.h"
+#include "../../mm/internal.h"
+#include "../kexec_internal.h"
#include "kexec_handover_internal.h"
#define KHO_FDT_COMPATIBLE "kho-v1"
@@ -1129,7 +1129,7 @@ static int __kho_finalize(void)
err |= fdt_finish_reservemap(root);
err |= fdt_begin_node(root, "");
err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
- /**
+ /*
* Reserve the preserved-memory-map property in the root FDT, so
* that all property definitions will precede subnodes created by
* KHO callers.
diff --git a/kernel/kexec_handover_debug.c b/kernel/liveupdate/kexec_handover_debug.c
similarity index 100%
rename from kernel/kexec_handover_debug.c
rename to kernel/liveupdate/kexec_handover_debug.c
diff --git a/kernel/kexec_handover_internal.h b/kernel/liveupdate/kexec_handover_internal.h
similarity index 100%
rename from kernel/kexec_handover_internal.h
rename to kernel/liveupdate/kexec_handover_internal.h
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 05/30] kho: don't unpreserve memory during abort
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
KHO allows clients to preserve memory regions at any point before the
KHO state is finalized. The finalization process itself involves KHO
performing its own actions, such as serializing the overall
preserved memory map.
If this finalization process is aborted, the current implementation
destroys KHO's internal memory tracking structures
(`kho_out.ser.track.orders`). This behavior effectively unpreserves
all memory from KHO's perspective, regardless of whether those
preservations were made by clients before the finalization attempt
or by KHO itself during finalization.
This premature unpreservation is incorrect. An abort of the
finalization process should only undo actions taken by KHO as part of
that specific finalization attempt. Individual memory regions
preserved by clients prior to finalization should remain preserved,
as their lifecycle is managed by the clients themselves. These
clients might still need to call kho_unpreserve_folio() or
kho_unpreserve_phys() based on their own logic, even after a KHO
finalization attempt is aborted.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
kernel/kexec_handover.c | 21 +--------------------
1 file changed, 1 insertion(+), 20 deletions(-)
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 26e035eb1314..61b31cfc75f2 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -1083,31 +1083,12 @@ EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
static int __kho_abort(void)
{
- int err = 0;
- unsigned long order;
- struct kho_mem_phys *physxa;
-
- xa_for_each(&kho_out.track.orders, order, physxa) {
- struct kho_mem_phys_bits *bits;
- unsigned long phys;
-
- xa_for_each(&physxa->phys_bits, phys, bits)
- kfree(bits);
-
- xa_destroy(&physxa->phys_bits);
- kfree(physxa);
- }
- xa_destroy(&kho_out.track.orders);
-
if (kho_out.preserved_mem_map) {
kho_mem_ser_free(kho_out.preserved_mem_map);
kho_out.preserved_mem_map = NULL;
}
- if (err)
- pr_err("Failed to abort KHO finalization: %d\n", err);
-
- return err;
+ return 0;
}
int kho_abort(void)
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 04/30] kho: add interfaces to unpreserve folios and page ranes
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Allow users of KHO to cancel the previous preservation by adding the
necessary interfaces to unpreserve folio and pages.
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/kexec_handover.h | 12 +++++
kernel/kexec_handover.c | 85 ++++++++++++++++++++++++++++------
2 files changed, 84 insertions(+), 13 deletions(-)
diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 2faf290803ce..4ba145713838 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -43,7 +43,9 @@ bool kho_is_enabled(void);
bool is_kho_boot(void);
int kho_preserve_folio(struct folio *folio);
+int kho_unpreserve_folio(struct folio *folio);
int kho_preserve_pages(struct page *page, unsigned int nr_pages);
+int kho_unpreserve_pages(struct page *page, unsigned int nr_pages);
int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation);
struct folio *kho_restore_folio(phys_addr_t phys);
struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages);
@@ -76,11 +78,21 @@ static inline int kho_preserve_folio(struct folio *folio)
return -EOPNOTSUPP;
}
+static inline int kho_unpreserve_folio(struct folio *folio)
+{
+ return -EOPNOTSUPP;
+}
+
static inline int kho_preserve_pages(struct page *page, unsigned int nr_pages)
{
return -EOPNOTSUPP;
}
+static inline int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
+{
+ return -EOPNOTSUPP;
+}
+
static inline int kho_preserve_vmalloc(void *ptr,
struct kho_vmalloc *preservation)
{
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index e0dc0ed565ef..26e035eb1314 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -153,26 +153,33 @@ static void *xa_load_or_alloc(struct xarray *xa, unsigned long index, size_t sz)
return elm;
}
-static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
- unsigned long end_pfn)
+static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn,
+ unsigned int order)
{
struct kho_mem_phys_bits *bits;
struct kho_mem_phys *physxa;
+ const unsigned long pfn_high = pfn >> order;
- while (pfn < end_pfn) {
- const unsigned int order =
- min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
- const unsigned long pfn_high = pfn >> order;
+ physxa = xa_load(&track->orders, order);
+ if (!physxa)
+ return;
+
+ bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
+ if (!bits)
+ return;
- physxa = xa_load(&track->orders, order);
- if (!physxa)
- continue;
+ clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+}
+
+static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
+ unsigned long end_pfn)
+{
+ unsigned int order;
- bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
- if (!bits)
- continue;
+ while (pfn < end_pfn) {
+ order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
- clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+ __kho_unpreserve_order(track, pfn, order);
pfn += 1 << order;
}
@@ -734,6 +741,30 @@ int kho_preserve_folio(struct folio *folio)
}
EXPORT_SYMBOL_GPL(kho_preserve_folio);
+/**
+ * kho_unpreserve_folio - unpreserve a folio.
+ * @folio: folio to unpreserve.
+ *
+ * Instructs KHO to unpreserve a folio that was preserved by
+ * kho_preserve_folio() before. The provided @folio (pfn and order)
+ * must exactly match a previously preserved folio.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_folio(struct folio *folio)
+{
+ const unsigned long pfn = folio_pfn(folio);
+ const unsigned int order = folio_order(folio);
+ struct kho_mem_track *track = &kho_out.track;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve_order(track, pfn, order);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
+
/**
* kho_preserve_pages - preserve contiguous pages across kexec
* @page: first page in the list.
@@ -773,6 +804,34 @@ int kho_preserve_pages(struct page *page, unsigned int nr_pages)
}
EXPORT_SYMBOL_GPL(kho_preserve_pages);
+/**
+ * kho_unpreserve_pages - unpreserve contiguous pages.
+ * @page: first page in the list.
+ * @nr_pages: number of pages.
+ *
+ * Instructs KHO to unpreserve @nr_pages contigious pages starting from @page.
+ * This call must exactly match a granularity at which memory was originally
+ * preserved by kho_preserve_pages, call with the same @page and
+ * @nr_pages). Unpreserving arbitrary sub-ranges of larger preserved blocks is
+ * not supported.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ const unsigned long start_pfn = page_to_pfn(page);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve(track, start_pfn, end_pfn);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_pages);
+
struct kho_vmalloc_hdr {
DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *);
};
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 03/30] kho: drop notifiers
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
The KHO framework uses a notifier chain as the mechanism for clients to
participate in the finalization process. While this works for a single,
central state machine, it is too restrictive for kernel-internal
components like pstore/reserve_mem or IMA. These components need a
simpler, direct way to register their state for preservation (e.g.,
during their initcall) without being part of a complex,
shutdown-time notifier sequence. The notifier model forces all
participants into a single finalization flow and makes direct
preservation from an arbitrary context difficult.
This patch refactors the client participation model by removing the
notifier chain and introducing a direct API for managing FDT subtrees.
The core kho_finalize() and kho_abort() state machine remains, but
clients now register their data with KHO beforehand.
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/kexec_handover.h | 28 +----
kernel/kexec_handover.c | 184 +++++++++++++++----------------
kernel/kexec_handover_debug.c | 17 +--
kernel/kexec_handover_internal.h | 5 +-
mm/memblock.c | 60 ++--------
5 files changed, 118 insertions(+), 176 deletions(-)
diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 04d0108db98e..2faf290803ce 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -10,14 +10,7 @@ struct kho_scratch {
phys_addr_t size;
};
-/* KHO Notifier index */
-enum kho_event {
- KEXEC_KHO_FINALIZE = 0,
- KEXEC_KHO_ABORT = 1,
-};
-
struct folio;
-struct notifier_block;
struct page;
#define DECLARE_KHOSER_PTR(name, type) \
@@ -37,8 +30,6 @@ struct page;
(typeof((s).ptr))((s).phys ? phys_to_virt((s).phys) : NULL); \
})
-struct kho_serialization;
-
struct kho_vmalloc_chunk;
struct kho_vmalloc {
DECLARE_KHOSER_PTR(first, struct kho_vmalloc_chunk *);
@@ -57,12 +48,10 @@ int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation);
struct folio *kho_restore_folio(phys_addr_t phys);
struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages);
void *kho_restore_vmalloc(const struct kho_vmalloc *preservation);
-int kho_add_subtree(struct kho_serialization *ser, const char *name, void *fdt);
+int kho_add_subtree(const char *name, void *fdt);
+void kho_remove_subtree(void *fdt);
int kho_retrieve_subtree(const char *name, phys_addr_t *phys);
-int register_kho_notifier(struct notifier_block *nb);
-int unregister_kho_notifier(struct notifier_block *nb);
-
void kho_memory_init(void);
void kho_populate(phys_addr_t fdt_phys, u64 fdt_len, phys_addr_t scratch_phys,
@@ -114,23 +103,16 @@ static inline void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
return NULL;
}
-static inline int kho_add_subtree(struct kho_serialization *ser,
- const char *name, void *fdt)
+static inline int kho_add_subtree(const char *name, void *fdt)
{
return -EOPNOTSUPP;
}
-static inline int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
+static inline void kho_remove_subtree(void *fdt)
{
- return -EOPNOTSUPP;
}
-static inline int register_kho_notifier(struct notifier_block *nb)
-{
- return -EOPNOTSUPP;
-}
-
-static inline int unregister_kho_notifier(struct notifier_block *nb)
+static inline int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
{
return -EOPNOTSUPP;
}
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index f0f6c6b8ad83..e0dc0ed565ef 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -15,7 +15,6 @@
#include <linux/libfdt.h>
#include <linux/list.h>
#include <linux/memblock.h>
-#include <linux/notifier.h>
#include <linux/page-isolation.h>
#include <linux/vmalloc.h>
@@ -99,33 +98,34 @@ struct kho_mem_track {
struct khoser_mem_chunk;
-struct kho_serialization {
- struct page *fdt;
- struct kho_mem_track track;
- /* First chunk of serialized preserved memory map */
- struct khoser_mem_chunk *preserved_mem_map;
+struct kho_sub_fdt {
+ struct list_head l;
+ const char *name;
+ void *fdt;
};
struct kho_out {
- struct blocking_notifier_head chain_head;
+ void *fdt;
+ bool finalized;
+ struct mutex lock; /* protects KHO FDT finalization */
- struct dentry *dir;
+ struct list_head sub_fdts;
+ struct mutex fdts_lock;
- struct mutex lock; /* protects KHO FDT finalization */
+ struct kho_mem_track track;
+ /* First chunk of serialized preserved memory map */
+ struct khoser_mem_chunk *preserved_mem_map;
- struct kho_serialization ser;
- bool finalized;
+ struct kho_debugfs dbg;
};
static struct kho_out kho_out = {
- .chain_head = BLOCKING_NOTIFIER_INIT(kho_out.chain_head),
.lock = __MUTEX_INITIALIZER(kho_out.lock),
- .ser = {
- .fdt_list = LIST_HEAD_INIT(kho_out.ser.fdt_list),
- .track = {
- .orders = XARRAY_INIT(kho_out.ser.track.orders, 0),
- },
+ .track = {
+ .orders = XARRAY_INIT(kho_out.track.orders, 0),
},
+ .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts),
+ .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock),
.finalized = false,
};
@@ -366,14 +366,14 @@ static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
}
}
-static int kho_mem_serialize(struct kho_serialization *ser)
+static int kho_mem_serialize(struct kho_out *kho_out)
{
struct khoser_mem_chunk *first_chunk = NULL;
struct khoser_mem_chunk *chunk = NULL;
struct kho_mem_phys *physxa;
unsigned long order;
- xa_for_each(&ser->track.orders, order, physxa) {
+ xa_for_each(&kho_out->track.orders, order, physxa) {
struct kho_mem_phys_bits *bits;
unsigned long phys;
@@ -401,7 +401,7 @@ static int kho_mem_serialize(struct kho_serialization *ser)
}
}
- ser->preserved_mem_map = first_chunk;
+ kho_out->preserved_mem_map = first_chunk;
return 0;
@@ -660,28 +660,8 @@ static void __init kho_reserve_scratch(void)
kho_enable = false;
}
-struct kho_out {
- struct blocking_notifier_head chain_head;
- struct mutex lock; /* protects KHO FDT finalization */
- struct kho_serialization ser;
- bool finalized;
- struct kho_debugfs dbg;
-};
-
-static struct kho_out kho_out = {
- .chain_head = BLOCKING_NOTIFIER_INIT(kho_out.chain_head),
- .lock = __MUTEX_INITIALIZER(kho_out.lock),
- .ser = {
- .track = {
- .orders = XARRAY_INIT(kho_out.ser.track.orders, 0),
- },
- },
- .finalized = false,
-};
-
/**
* kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
- * @ser: serialization control object passed by KHO notifiers.
* @name: name of the sub tree.
* @fdt: the sub tree blob.
*
@@ -695,34 +675,45 @@ static struct kho_out kho_out = {
*
* Return: 0 on success, error code on failure
*/
-int kho_add_subtree(struct kho_serialization *ser, const char *name, void *fdt)
+int kho_add_subtree(const char *name, void *fdt)
{
- int err = 0;
- u64 phys = (u64)virt_to_phys(fdt);
- void *root = page_to_virt(ser->fdt);
+ struct kho_sub_fdt *sub_fdt;
+ int err;
- err |= fdt_begin_node(root, name);
- err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
- err |= fdt_end_node(root);
+ sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL);
+ if (!sub_fdt)
+ return -ENOMEM;
- if (err)
- return err;
+ INIT_LIST_HEAD(&sub_fdt->l);
+ sub_fdt->name = name;
+ sub_fdt->fdt = fdt;
+
+ mutex_lock(&kho_out.fdts_lock);
+ list_add_tail(&sub_fdt->l, &kho_out.sub_fdts);
+ err = kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false);
+ mutex_unlock(&kho_out.fdts_lock);
- return kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false);
+ return err;
}
EXPORT_SYMBOL_GPL(kho_add_subtree);
-int register_kho_notifier(struct notifier_block *nb)
+void kho_remove_subtree(void *fdt)
{
- return blocking_notifier_chain_register(&kho_out.chain_head, nb);
-}
-EXPORT_SYMBOL_GPL(register_kho_notifier);
+ struct kho_sub_fdt *sub_fdt;
+
+ mutex_lock(&kho_out.fdts_lock);
+ list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) {
+ if (sub_fdt->fdt == fdt) {
+ list_del(&sub_fdt->l);
+ kfree(sub_fdt);
+ kho_debugfs_fdt_remove(&kho_out.dbg, fdt);
+ break;
+ }
+ }
+ mutex_unlock(&kho_out.fdts_lock);
-int unregister_kho_notifier(struct notifier_block *nb)
-{
- return blocking_notifier_chain_unregister(&kho_out.chain_head, nb);
}
-EXPORT_SYMBOL_GPL(unregister_kho_notifier);
+EXPORT_SYMBOL_GPL(kho_remove_subtree);
/**
* kho_preserve_folio - preserve a folio across kexec.
@@ -737,7 +728,7 @@ int kho_preserve_folio(struct folio *folio)
{
const unsigned long pfn = folio_pfn(folio);
const unsigned int order = folio_order(folio);
- struct kho_mem_track *track = &kho_out.ser.track;
+ struct kho_mem_track *track = &kho_out.track;
return __kho_preserve_order(track, pfn, order);
}
@@ -755,7 +746,7 @@ EXPORT_SYMBOL_GPL(kho_preserve_folio);
*/
int kho_preserve_pages(struct page *page, unsigned int nr_pages)
{
- struct kho_mem_track *track = &kho_out.ser.track;
+ struct kho_mem_track *track = &kho_out.track;
const unsigned long start_pfn = page_to_pfn(page);
const unsigned long end_pfn = start_pfn + nr_pages;
unsigned long pfn = start_pfn;
@@ -851,7 +842,7 @@ static struct kho_vmalloc_chunk *new_vmalloc_chunk(struct kho_vmalloc_chunk *cur
static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk)
{
- struct kho_mem_track *track = &kho_out.ser.track;
+ struct kho_mem_track *track = &kho_out.track;
unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
__kho_unpreserve(track, pfn, pfn + 1);
@@ -1033,11 +1024,11 @@ EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
static int __kho_abort(void)
{
- int err;
+ int err = 0;
unsigned long order;
struct kho_mem_phys *physxa;
- xa_for_each(&kho_out.ser.track.orders, order, physxa) {
+ xa_for_each(&kho_out.track.orders, order, physxa) {
struct kho_mem_phys_bits *bits;
unsigned long phys;
@@ -1047,17 +1038,13 @@ static int __kho_abort(void)
xa_destroy(&physxa->phys_bits);
kfree(physxa);
}
- xa_destroy(&kho_out.ser.track.orders);
+ xa_destroy(&kho_out.track.orders);
- if (kho_out.ser.preserved_mem_map) {
- kho_mem_ser_free(kho_out.ser.preserved_mem_map);
- kho_out.ser.preserved_mem_map = NULL;
+ if (kho_out.preserved_mem_map) {
+ kho_mem_ser_free(kho_out.preserved_mem_map);
+ kho_out.preserved_mem_map = NULL;
}
- err = blocking_notifier_call_chain(&kho_out.chain_head, KEXEC_KHO_ABORT,
- NULL);
- err = notifier_to_errno(err);
-
if (err)
pr_err("Failed to abort KHO finalization: %d\n", err);
@@ -1084,7 +1071,7 @@ int kho_abort(void)
kho_out.finalized = false;
- kho_debugfs_cleanup(&kho_out.dbg);
+ kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt);
unlock:
mutex_unlock(&kho_out.lock);
@@ -1095,41 +1082,46 @@ static int __kho_finalize(void)
{
int err = 0;
u64 *preserved_mem_map;
- void *fdt = page_to_virt(kho_out.ser.fdt);
+ void *root = kho_out.fdt;
+ struct kho_sub_fdt *fdt;
- err |= fdt_create(fdt, PAGE_SIZE);
- err |= fdt_finish_reservemap(fdt);
- err |= fdt_begin_node(fdt, "");
- err |= fdt_property_string(fdt, "compatible", KHO_FDT_COMPATIBLE);
+ err |= fdt_create(root, PAGE_SIZE);
+ err |= fdt_finish_reservemap(root);
+ err |= fdt_begin_node(root, "");
+ err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
/**
* Reserve the preserved-memory-map property in the root FDT, so
* that all property definitions will precede subnodes created by
* KHO callers.
*/
- err |= fdt_property_placeholder(fdt, PROP_PRESERVED_MEMORY_MAP,
+ err |= fdt_property_placeholder(root, PROP_PRESERVED_MEMORY_MAP,
sizeof(*preserved_mem_map),
(void **)&preserved_mem_map);
if (err)
goto abort;
- err = kho_preserve_folio(page_folio(kho_out.ser.fdt));
+ err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
if (err)
goto abort;
- err = blocking_notifier_call_chain(&kho_out.chain_head,
- KEXEC_KHO_FINALIZE, &kho_out.ser);
- err = notifier_to_errno(err);
+ err = kho_mem_serialize(&kho_out);
if (err)
goto abort;
- err = kho_mem_serialize(&kho_out.ser);
- if (err)
- goto abort;
+ *preserved_mem_map = (u64)virt_to_phys(kho_out.preserved_mem_map);
- *preserved_mem_map = (u64)virt_to_phys(kho_out.ser.preserved_mem_map);
+ mutex_lock(&kho_out.fdts_lock);
+ list_for_each_entry(fdt, &kho_out.sub_fdts, l) {
+ phys_addr_t phys = virt_to_phys(fdt->fdt);
- err |= fdt_end_node(fdt);
- err |= fdt_finish(fdt);
+ err |= fdt_begin_node(root, fdt->name);
+ err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
+ err |= fdt_end_node(root);
+ };
+ mutex_unlock(&kho_out.fdts_lock);
+
+ err |= fdt_end_node(root);
+ err |= fdt_finish(root);
abort:
if (err) {
@@ -1160,7 +1152,7 @@ int kho_finalize(void)
kho_out.finalized = true;
ret = kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
- page_to_virt(kho_out.ser.fdt), true);
+ kho_out.fdt, true);
unlock:
mutex_unlock(&kho_out.lock);
@@ -1252,15 +1244,17 @@ static __init int kho_init(void)
{
int err = 0;
const void *fdt = kho_get_fdt();
+ struct page *fdt_page;
if (!kho_enable)
return 0;
- kho_out.ser.fdt = alloc_page(GFP_KERNEL);
- if (!kho_out.ser.fdt) {
+ fdt_page = alloc_page(GFP_KERNEL);
+ if (!fdt_page) {
err = -ENOMEM;
goto err_free_scratch;
}
+ kho_out.fdt = page_to_virt(fdt_page);
err = kho_debugfs_init();
if (err)
@@ -1288,8 +1282,8 @@ static __init int kho_init(void)
return 0;
err_free_fdt:
- put_page(kho_out.ser.fdt);
- kho_out.ser.fdt = NULL;
+ put_page(fdt_page);
+ kho_out.fdt = NULL;
err_free_scratch:
for (int i = 0; i < kho_scratch_cnt; i++) {
void *start = __va(kho_scratch[i].addr);
@@ -1300,7 +1294,7 @@ static __init int kho_init(void)
kho_enable = false;
return err;
}
-late_initcall(kho_init);
+fs_initcall(kho_init);
static void __init kho_release_scratch(void)
{
@@ -1436,7 +1430,7 @@ int kho_fill_kimage(struct kimage *image)
if (!kho_out.finalized)
return 0;
- image->kho.fdt = page_to_phys(kho_out.ser.fdt);
+ image->kho.fdt = virt_to_phys(kho_out.fdt);
scratch_size = sizeof(*kho_scratch) * kho_scratch_cnt;
scratch = (struct kexec_buf){
diff --git a/kernel/kexec_handover_debug.c b/kernel/kexec_handover_debug.c
index b88d138a97be..af4bad225630 100644
--- a/kernel/kexec_handover_debug.c
+++ b/kernel/kexec_handover_debug.c
@@ -61,14 +61,17 @@ int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
}
-void kho_debugfs_cleanup(struct kho_debugfs *dbg)
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt)
{
- struct fdt_debugfs *ff, *tmp;
-
- list_for_each_entry_safe(ff, tmp, &dbg->fdt_list, list) {
- debugfs_remove(ff->file);
- list_del(&ff->list);
- kfree(ff);
+ struct fdt_debugfs *ff;
+
+ list_for_each_entry(ff, &dbg->fdt_list, list) {
+ if (ff->wrapper.data == fdt) {
+ debugfs_remove(ff->file);
+ list_del(&ff->list);
+ kfree(ff);
+ break;
+ }
}
}
diff --git a/kernel/kexec_handover_internal.h b/kernel/kexec_handover_internal.h
index f6f172ddcae4..229a05558b99 100644
--- a/kernel/kexec_handover_internal.h
+++ b/kernel/kexec_handover_internal.h
@@ -30,7 +30,7 @@ void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
int kho_out_debugfs_init(struct kho_debugfs *dbg);
int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
const void *fdt, bool root);
-void kho_debugfs_cleanup(struct kho_debugfs *dbg);
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt);
#else
static inline int kho_debugfs_init(void) { return 0; }
static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
@@ -38,7 +38,8 @@ static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
const void *fdt, bool root) { return 0; }
-static inline void kho_debugfs_cleanup(struct kho_debugfs *dbg) {}
+static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg,
+ void *fdt) { }
#endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
diff --git a/mm/memblock.c b/mm/memblock.c
index e23e16618e9b..c4b2d4e4c715 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -2444,53 +2444,18 @@ int reserve_mem_release_by_name(const char *name)
#define MEMBLOCK_KHO_FDT "memblock"
#define MEMBLOCK_KHO_NODE_COMPATIBLE "memblock-v1"
#define RESERVE_MEM_KHO_NODE_COMPATIBLE "reserve-mem-v1"
-static struct page *kho_fdt;
-
-static int reserve_mem_kho_finalize(struct kho_serialization *ser)
-{
- int err = 0, i;
-
- for (i = 0; i < reserved_mem_count; i++) {
- struct reserve_mem_table *map = &reserved_mem_table[i];
- struct page *page = phys_to_page(map->start);
- unsigned int nr_pages = map->size >> PAGE_SHIFT;
-
- err |= kho_preserve_pages(page, nr_pages);
- }
-
- err |= kho_preserve_folio(page_folio(kho_fdt));
- err |= kho_add_subtree(ser, MEMBLOCK_KHO_FDT, page_to_virt(kho_fdt));
-
- return notifier_from_errno(err);
-}
-
-static int reserve_mem_kho_notifier(struct notifier_block *self,
- unsigned long cmd, void *v)
-{
- switch (cmd) {
- case KEXEC_KHO_FINALIZE:
- return reserve_mem_kho_finalize((struct kho_serialization *)v);
- case KEXEC_KHO_ABORT:
- return NOTIFY_DONE;
- default:
- return NOTIFY_BAD;
- }
-}
-
-static struct notifier_block reserve_mem_kho_nb = {
- .notifier_call = reserve_mem_kho_notifier,
-};
static int __init prepare_kho_fdt(void)
{
int err = 0, i;
+ struct page *fdt_page;
void *fdt;
- kho_fdt = alloc_page(GFP_KERNEL);
- if (!kho_fdt)
+ fdt_page = alloc_page(GFP_KERNEL);
+ if (!fdt_page)
return -ENOMEM;
- fdt = page_to_virt(kho_fdt);
+ fdt = page_to_virt(fdt_page);
err |= fdt_create(fdt, PAGE_SIZE);
err |= fdt_finish_reservemap(fdt);
@@ -2499,7 +2464,10 @@ static int __init prepare_kho_fdt(void)
err |= fdt_property_string(fdt, "compatible", MEMBLOCK_KHO_NODE_COMPATIBLE);
for (i = 0; i < reserved_mem_count; i++) {
struct reserve_mem_table *map = &reserved_mem_table[i];
+ struct page *page = phys_to_page(map->start);
+ unsigned int nr_pages = map->size >> PAGE_SHIFT;
+ err |= kho_preserve_pages(page, nr_pages);
err |= fdt_begin_node(fdt, map->name);
err |= fdt_property_string(fdt, "compatible", RESERVE_MEM_KHO_NODE_COMPATIBLE);
err |= fdt_property(fdt, "start", &map->start, sizeof(map->start));
@@ -2507,13 +2475,14 @@ static int __init prepare_kho_fdt(void)
err |= fdt_end_node(fdt);
}
err |= fdt_end_node(fdt);
-
err |= fdt_finish(fdt);
+ err |= kho_preserve_folio(page_folio(fdt_page));
+ err |= kho_add_subtree(MEMBLOCK_KHO_FDT, fdt);
+
if (err) {
pr_err("failed to prepare memblock FDT for KHO: %d\n", err);
- put_page(kho_fdt);
- kho_fdt = NULL;
+ put_page(fdt_page);
}
return err;
@@ -2529,13 +2498,6 @@ static int __init reserve_mem_init(void)
err = prepare_kho_fdt();
if (err)
return err;
-
- err = register_kho_notifier(&reserve_mem_kho_nb);
- if (err) {
- put_page(kho_fdt);
- kho_fdt = NULL;
- }
-
return err;
}
late_initcall(reserve_mem_init);
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 02/30] kho: make debugfs interface optional
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Currently, KHO is controlled via debugfs interface, but once LUO is
introduced, it can control KHO, and the debug interface becomes
optional.
Add a separate config CONFIG_KEXEC_HANDOVER_DEBUG that enables
the debugfs interface, and allows to inspect the tree.
Move all debugfs related code to a new file to keep the .c files
clear of ifdefs.
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
MAINTAINERS | 3 +-
kernel/Kconfig.kexec | 10 ++
kernel/Makefile | 1 +
kernel/kexec_handover.c | 255 +++++--------------------------
kernel/kexec_handover_debug.c | 218 ++++++++++++++++++++++++++
kernel/kexec_handover_internal.h | 44 ++++++
6 files changed, 311 insertions(+), 220 deletions(-)
create mode 100644 kernel/kexec_handover_debug.c
create mode 100644 kernel/kexec_handover_internal.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 156fa8eefa69..a6cbcc7fb396 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13759,13 +13759,14 @@ KEXEC HANDOVER (KHO)
M: Alexander Graf <graf@amazon.com>
M: Mike Rapoport <rppt@kernel.org>
M: Changyuan Lyu <changyuanl@google.com>
+M: Pasha Tatashin <pasha.tatashin@soleen.com>
L: kexec@lists.infradead.org
L: linux-mm@kvack.org
S: Maintained
F: Documentation/admin-guide/mm/kho.rst
F: Documentation/core-api/kho/*
F: include/linux/kexec_handover.h
-F: kernel/kexec_handover.c
+F: kernel/kexec_handover*
F: tools/testing/selftests/kho/
KEYS-ENCRYPTED
diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
index 422270d64820..e68156d8c72b 100644
--- a/kernel/Kconfig.kexec
+++ b/kernel/Kconfig.kexec
@@ -109,6 +109,16 @@ config KEXEC_HANDOVER
to keep data or state alive across the kexec. For this to work,
both source and target kernels need to have this option enabled.
+config KEXEC_HANDOVER_DEBUG
+ bool "kexec handover debug interface"
+ depends on KEXEC_HANDOVER
+ depends on DEBUG_FS
+ help
+ Allow to control kexec handover device tree via debugfs
+ interface, i.e. finalize the state or aborting the finalization.
+ Also, enables inspecting the KHO fdt trees with the debugfs binary
+ blobs.
+
config CRASH_DUMP
bool "kernel crash dumps"
default ARCH_DEFAULT_CRASH_DUMP
diff --git a/kernel/Makefile b/kernel/Makefile
index df3dd8291bb6..9fe722305c9b 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -83,6 +83,7 @@ obj-$(CONFIG_KEXEC) += kexec.o
obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup/
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 0ba5a2dbae28..f0f6c6b8ad83 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -10,7 +10,6 @@
#include <linux/cma.h>
#include <linux/count_zeros.h>
-#include <linux/debugfs.h>
#include <linux/kexec.h>
#include <linux/kexec_handover.h>
#include <linux/libfdt.h>
@@ -28,6 +27,7 @@
*/
#include "../mm/internal.h"
#include "kexec_internal.h"
+#include "kexec_handover_internal.h"
#define KHO_FDT_COMPATIBLE "kho-v1"
#define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
@@ -101,8 +101,6 @@ struct khoser_mem_chunk;
struct kho_serialization {
struct page *fdt;
- struct list_head fdt_list;
- struct dentry *sub_fdt_dir;
struct kho_mem_track track;
/* First chunk of serialized preserved memory map */
struct khoser_mem_chunk *preserved_mem_map;
@@ -465,8 +463,8 @@ static void __init kho_mem_deserialize(const void *fdt)
* area for early allocations that happen before page allocator is
* initialized.
*/
-static struct kho_scratch *kho_scratch;
-static unsigned int kho_scratch_cnt;
+struct kho_scratch *kho_scratch;
+unsigned int kho_scratch_cnt;
/*
* The scratch areas are scaled by default as percent of memory allocated from
@@ -662,36 +660,24 @@ static void __init kho_reserve_scratch(void)
kho_enable = false;
}
-struct fdt_debugfs {
- struct list_head list;
- struct debugfs_blob_wrapper wrapper;
- struct dentry *file;
+struct kho_out {
+ struct blocking_notifier_head chain_head;
+ struct mutex lock; /* protects KHO FDT finalization */
+ struct kho_serialization ser;
+ bool finalized;
+ struct kho_debugfs dbg;
};
-static int kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
- const char *name, const void *fdt)
-{
- struct fdt_debugfs *f;
- struct dentry *file;
-
- f = kmalloc(sizeof(*f), GFP_KERNEL);
- if (!f)
- return -ENOMEM;
-
- f->wrapper.data = (void *)fdt;
- f->wrapper.size = fdt_totalsize(fdt);
-
- file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
- if (IS_ERR(file)) {
- kfree(f);
- return PTR_ERR(file);
- }
-
- f->file = file;
- list_add(&f->list, list);
-
- return 0;
-}
+static struct kho_out kho_out = {
+ .chain_head = BLOCKING_NOTIFIER_INIT(kho_out.chain_head),
+ .lock = __MUTEX_INITIALIZER(kho_out.lock),
+ .ser = {
+ .track = {
+ .orders = XARRAY_INIT(kho_out.ser.track.orders, 0),
+ },
+ },
+ .finalized = false,
+};
/**
* kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
@@ -704,7 +690,8 @@ static int kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
* by KHO for the new kernel to retrieve it after kexec.
*
* A debugfs blob entry is also created at
- * ``/sys/kernel/debug/kho/out/sub_fdts/@name``.
+ * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured with
+ * CONFIG_KEXEC_HANDOVER_DEBUG
*
* Return: 0 on success, error code on failure
*/
@@ -721,7 +708,7 @@ int kho_add_subtree(struct kho_serialization *ser, const char *name, void *fdt)
if (err)
return err;
- return kho_debugfs_fdt_add(&ser->fdt_list, ser->sub_fdt_dir, name, fdt);
+ return kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false);
}
EXPORT_SYMBOL_GPL(kho_add_subtree);
@@ -1044,29 +1031,6 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
}
EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
-/* Handling for debug/kho/out */
-
-static struct dentry *debugfs_root;
-
-static int kho_out_update_debugfs_fdt(void)
-{
- int err = 0;
- struct fdt_debugfs *ff, *tmp;
-
- if (kho_out.finalized) {
- err = kho_debugfs_fdt_add(&kho_out.ser.fdt_list, kho_out.dir,
- "fdt", page_to_virt(kho_out.ser.fdt));
- } else {
- list_for_each_entry_safe(ff, tmp, &kho_out.ser.fdt_list, list) {
- debugfs_remove(ff->file);
- list_del(&ff->list);
- kfree(ff);
- }
- }
-
- return err;
-}
-
static int __kho_abort(void)
{
int err;
@@ -1119,7 +1083,8 @@ int kho_abort(void)
goto unlock;
kho_out.finalized = false;
- ret = kho_out_update_debugfs_fdt();
+
+ kho_debugfs_cleanup(&kho_out.dbg);
unlock:
mutex_unlock(&kho_out.lock);
@@ -1169,7 +1134,7 @@ static int __kho_finalize(void)
abort:
if (err) {
pr_err("Failed to convert KHO state tree: %d\n", err);
- kho_abort();
+ __kho_abort();
}
return err;
@@ -1194,119 +1159,32 @@ int kho_finalize(void)
goto unlock;
kho_out.finalized = true;
- ret = kho_out_update_debugfs_fdt();
+ ret = kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
+ page_to_virt(kho_out.ser.fdt), true);
unlock:
mutex_unlock(&kho_out.lock);
return ret;
}
-static int kho_out_finalize_get(void *data, u64 *val)
+bool kho_finalized(void)
{
- mutex_lock(&kho_out.lock);
- *val = kho_out.finalized;
- mutex_unlock(&kho_out.lock);
-
- return 0;
-}
-
-static int kho_out_finalize_set(void *data, u64 _val)
-{
- int ret = 0;
- bool val = !!_val;
+ bool ret;
mutex_lock(&kho_out.lock);
-
- if (val == kho_out.finalized) {
- if (kho_out.finalized)
- ret = -EEXIST;
- else
- ret = -ENOENT;
- goto unlock;
- }
-
- if (val)
- ret = kho_finalize();
- else
- ret = kho_abort();
-
- if (ret)
- goto unlock;
-
- kho_out.finalized = val;
- ret = kho_out_update_debugfs_fdt();
-
-unlock:
+ ret = kho_out.finalized;
mutex_unlock(&kho_out.lock);
- return ret;
-}
-
-DEFINE_DEBUGFS_ATTRIBUTE(fops_kho_out_finalize, kho_out_finalize_get,
- kho_out_finalize_set, "%llu\n");
-
-static int scratch_phys_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_phys);
-static int scratch_len_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].size);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_len);
-
-static __init int kho_out_debugfs_init(void)
-{
- struct dentry *dir, *f, *sub_fdt_dir;
-
- dir = debugfs_create_dir("out", debugfs_root);
- if (IS_ERR(dir))
- return -ENOMEM;
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
- if (IS_ERR(sub_fdt_dir))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
- &scratch_phys_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_len", 0400, dir, NULL,
- &scratch_len_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("finalize", 0600, dir, NULL,
- &fops_kho_out_finalize);
- if (IS_ERR(f))
- goto err_rmdir;
-
- kho_out.dir = dir;
- kho_out.ser.sub_fdt_dir = sub_fdt_dir;
- return 0;
-
-err_rmdir:
- debugfs_remove_recursive(dir);
- return -ENOENT;
+ return ret;
}
struct kho_in {
- struct dentry *dir;
phys_addr_t fdt_phys;
phys_addr_t scratch_phys;
- struct list_head fdt_list;
+ struct kho_debugfs dbg;
};
static struct kho_in kho_in = {
- .fdt_list = LIST_HEAD_INIT(kho_in.fdt_list),
};
static const void *kho_get_fdt(void)
@@ -1370,56 +1248,6 @@ int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
}
EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
-/* Handling for debugfs/kho/in */
-
-static __init int kho_in_debugfs_init(const void *fdt)
-{
- struct dentry *sub_fdt_dir;
- int err, child;
-
- kho_in.dir = debugfs_create_dir("in", debugfs_root);
- if (IS_ERR(kho_in.dir))
- return PTR_ERR(kho_in.dir);
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", kho_in.dir);
- if (IS_ERR(sub_fdt_dir)) {
- err = PTR_ERR(sub_fdt_dir);
- goto err_rmdir;
- }
-
- err = kho_debugfs_fdt_add(&kho_in.fdt_list, kho_in.dir, "fdt", fdt);
- if (err)
- goto err_rmdir;
-
- fdt_for_each_subnode(child, fdt, 0) {
- int len = 0;
- const char *name = fdt_get_name(fdt, child, NULL);
- const u64 *fdt_phys;
-
- fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
- if (!fdt_phys)
- continue;
- if (len != sizeof(*fdt_phys)) {
- pr_warn("node `%s`'s prop `fdt` has invalid length: %d\n",
- name, len);
- continue;
- }
- err = kho_debugfs_fdt_add(&kho_in.fdt_list, sub_fdt_dir, name,
- phys_to_virt(*fdt_phys));
- if (err) {
- pr_warn("failed to add fdt `%s` to debugfs: %d\n", name,
- err);
- continue;
- }
- }
-
- return 0;
-
-err_rmdir:
- debugfs_remove_recursive(kho_in.dir);
- return err;
-}
-
static __init int kho_init(void)
{
int err = 0;
@@ -1434,27 +1262,16 @@ static __init int kho_init(void)
goto err_free_scratch;
}
- debugfs_root = debugfs_create_dir("kho", NULL);
- if (IS_ERR(debugfs_root)) {
- err = -ENOENT;
+ err = kho_debugfs_init();
+ if (err)
goto err_free_fdt;
- }
- err = kho_out_debugfs_init();
+ err = kho_out_debugfs_init(&kho_out.dbg);
if (err)
goto err_free_fdt;
if (fdt) {
- err = kho_in_debugfs_init(fdt);
- /*
- * Failure to create /sys/kernel/debug/kho/in does not prevent
- * reviving state from KHO and setting up KHO for the next
- * kexec.
- */
- if (err)
- pr_err("failed exposing handover FDT in debugfs: %d\n",
- err);
-
+ kho_in_debugfs_init(&kho_in.dbg, fdt);
return 0;
}
diff --git a/kernel/kexec_handover_debug.c b/kernel/kexec_handover_debug.c
new file mode 100644
index 000000000000..b88d138a97be
--- /dev/null
+++ b/kernel/kexec_handover_debug.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover.c - kexec handover metadata processing
+ * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
+ * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
+ * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/libfdt.h>
+#include <linux/mm.h>
+#include "kexec_handover_internal.h"
+
+static struct dentry *debugfs_root;
+
+struct fdt_debugfs {
+ struct list_head list;
+ struct debugfs_blob_wrapper wrapper;
+ struct dentry *file;
+};
+
+static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
+ const char *name, const void *fdt)
+{
+ struct fdt_debugfs *f;
+ struct dentry *file;
+
+ f = kmalloc(sizeof(*f), GFP_KERNEL);
+ if (!f)
+ return -ENOMEM;
+
+ f->wrapper.data = (void *)fdt;
+ f->wrapper.size = fdt_totalsize(fdt);
+
+ file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
+ if (IS_ERR(file)) {
+ kfree(f);
+ return PTR_ERR(file);
+ }
+
+ f->file = file;
+ list_add(&f->list, list);
+
+ return 0;
+}
+
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root)
+{
+ struct dentry *dir;
+
+ if (root)
+ dir = dbg->dir;
+ else
+ dir = dbg->sub_fdt_dir;
+
+ return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
+}
+
+void kho_debugfs_cleanup(struct kho_debugfs *dbg)
+{
+ struct fdt_debugfs *ff, *tmp;
+
+ list_for_each_entry_safe(ff, tmp, &dbg->fdt_list, list) {
+ debugfs_remove(ff->file);
+ list_del(&ff->list);
+ kfree(ff);
+ }
+}
+
+static int kho_out_finalize_get(void *data, u64 *val)
+{
+ *val = kho_finalized();
+
+ return 0;
+}
+
+static int kho_out_finalize_set(void *data, u64 _val)
+{
+ bool val = !!_val;
+
+ if (val)
+ return kho_finalize();
+
+ return kho_abort();
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
+ kho_out_finalize_set, "%llu\n");
+
+static int scratch_phys_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_phys);
+
+static int scratch_len_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].size);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_len);
+
+__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
+{
+ struct dentry *dir, *sub_fdt_dir;
+ int err, child;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("in", debugfs_root);
+ if (IS_ERR(dir)) {
+ err = PTR_ERR(dir);
+ goto err_out;
+ }
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir)) {
+ err = PTR_ERR(sub_fdt_dir);
+ goto err_rmdir;
+ }
+
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt);
+ if (err)
+ goto err_rmdir;
+
+ fdt_for_each_subnode(child, fdt, 0) {
+ int len = 0;
+ const char *name = fdt_get_name(fdt, child, NULL);
+ const u64 *fdt_phys;
+
+ fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
+ if (!fdt_phys)
+ continue;
+ if (len != sizeof(*fdt_phys)) {
+ pr_warn("node %s prop fdt has invalid length: %d\n",
+ name, len);
+ continue;
+ }
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
+ phys_to_virt(*fdt_phys));
+ if (err) {
+ pr_warn("failed to add fdt %s to debugfs: %d\n", name,
+ err);
+ continue;
+ }
+ }
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+
+ return;
+err_rmdir:
+ debugfs_remove_recursive(dir);
+err_out:
+ /*
+ * Failure to create /sys/kernel/debug/kho/in does not prevent
+ * reviving state from KHO and setting up KHO for the next
+ * kexec.
+ */
+ if (err)
+ pr_err("failed exposing handover FDT in debugfs: %d\n", err);
+}
+
+__init int kho_out_debugfs_init(struct kho_debugfs *dbg)
+{
+ struct dentry *dir, *f, *sub_fdt_dir;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("out", debugfs_root);
+ if (IS_ERR(dir))
+ return -ENOMEM;
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
+ &scratch_phys_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_len", 0400, dir, NULL,
+ &scratch_len_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("finalize", 0600, dir, NULL,
+ &kho_out_finalize_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+ return 0;
+
+err_rmdir:
+ debugfs_remove_recursive(dir);
+ return -ENOENT;
+}
+
+__init int kho_debugfs_init(void)
+{
+ debugfs_root = debugfs_create_dir("kho", NULL);
+ if (IS_ERR(debugfs_root))
+ return -ENOENT;
+ return 0;
+}
diff --git a/kernel/kexec_handover_internal.h b/kernel/kexec_handover_internal.h
new file mode 100644
index 000000000000..f6f172ddcae4
--- /dev/null
+++ b/kernel/kexec_handover_internal.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
+#define LINUX_KEXEC_HANDOVER_INTERNAL_H
+
+#include <linux/kexec_handover.h>
+#include <linux/list.h>
+#include <linux/types.h>
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
+#include <linux/debugfs.h>
+
+struct kho_debugfs {
+ struct dentry *dir;
+ struct dentry *sub_fdt_dir;
+ struct list_head fdt_list;
+};
+
+#else
+struct kho_debugfs {};
+#endif
+
+extern struct kho_scratch *kho_scratch;
+extern unsigned int kho_scratch_cnt;
+
+bool kho_finalized(void);
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
+int kho_debugfs_init(void);
+void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
+int kho_out_debugfs_init(struct kho_debugfs *dbg);
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root);
+void kho_debugfs_cleanup(struct kho_debugfs *dbg);
+#else
+static inline int kho_debugfs_init(void) { return 0; }
+static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
+ const void *fdt) { }
+static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
+static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root) { return 0; }
+static inline void kho_debugfs_cleanup(struct kho_debugfs *dbg) {}
+#endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
+
+#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 01/30] kho: allow to drive kho from within kernel
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
In-Reply-To: <20250929010321.3462457-1-pasha.tatashin@soleen.com>
Allow to do finalize and abort from kernel modules, so LUO could
drive the KHO sequence via its own state machine.
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
include/linux/kexec_handover.h | 15 +++++++++
kernel/kexec_handover.c | 56 ++++++++++++++++++++++++++++++++--
2 files changed, 69 insertions(+), 2 deletions(-)
diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
index 25042c1d8d54..04d0108db98e 100644
--- a/include/linux/kexec_handover.h
+++ b/include/linux/kexec_handover.h
@@ -67,6 +67,10 @@ void kho_memory_init(void);
void kho_populate(phys_addr_t fdt_phys, u64 fdt_len, phys_addr_t scratch_phys,
u64 scratch_len);
+
+int kho_finalize(void);
+int kho_abort(void);
+
#else
static inline bool kho_is_enabled(void)
{
@@ -139,6 +143,17 @@ static inline void kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
phys_addr_t scratch_phys, u64 scratch_len)
{
}
+
+static inline int kho_finalize(void)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int kho_abort(void)
+{
+ return -EOPNOTSUPP;
+}
+
#endif /* CONFIG_KEXEC_HANDOVER */
#endif /* LINUX_KEXEC_HANDOVER_H */
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 76f0940fb485..0ba5a2dbae28 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -1067,7 +1067,7 @@ static int kho_out_update_debugfs_fdt(void)
return err;
}
-static int kho_abort(void)
+static int __kho_abort(void)
{
int err;
unsigned long order;
@@ -1100,7 +1100,33 @@ static int kho_abort(void)
return err;
}
-static int kho_finalize(void)
+int kho_abort(void)
+{
+ int ret = 0;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ mutex_lock(&kho_out.lock);
+
+ if (!kho_out.finalized) {
+ ret = -ENOENT;
+ goto unlock;
+ }
+
+ ret = __kho_abort();
+ if (ret)
+ goto unlock;
+
+ kho_out.finalized = false;
+ ret = kho_out_update_debugfs_fdt();
+
+unlock:
+ mutex_unlock(&kho_out.lock);
+ return ret;
+}
+
+static int __kho_finalize(void)
{
int err = 0;
u64 *preserved_mem_map;
@@ -1149,6 +1175,32 @@ static int kho_finalize(void)
return err;
}
+int kho_finalize(void)
+{
+ int ret = 0;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ mutex_lock(&kho_out.lock);
+
+ if (kho_out.finalized) {
+ ret = -EEXIST;
+ goto unlock;
+ }
+
+ ret = __kho_finalize();
+ if (ret)
+ goto unlock;
+
+ kho_out.finalized = true;
+ ret = kho_out_update_debugfs_fdt();
+
+unlock:
+ mutex_unlock(&kho_out.lock);
+ return ret;
+}
+
static int kho_out_finalize_get(void *data, u64 *val)
{
mutex_lock(&kho_out.lock);
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply related
* [PATCH v4 00/30] Live Update Orchestrator
From: Pasha Tatashin @ 2025-09-29 1:02 UTC (permalink / raw)
To: pratyush, jasonmiu, graf, changyuanl, pasha.tatashin, rppt,
dmatlack, rientjes, corbet, rdunlap, ilpo.jarvinen, kanie, ojeda,
aliceryhl, masahiroy, akpm, tj, yoann.congal, mmaurer,
roman.gushchin, chenridong, axboe, mark.rutland, jannh,
vincent.guittot, hannes, dan.j.williams, david, joel.granados,
rostedt, anna.schumaker, song, zhangguopeng, linux, linux-kernel,
linux-doc, linux-mm, gregkh, tglx, mingo, bp, dave.hansen, x86,
hpa, rafael, dakr, bartosz.golaszewski, cw00.choi, myungjoo.ham,
yesanishhere, Jonathan.Cameron, quic_zijuhu, aleksander.lobakin,
ira.weiny, andriy.shevchenko, leon, lukas, bhelgaas, wagi,
djeffery, stuart.w.hayes, ptyadav, lennart, brauner, linux-api,
linux-fsdevel, saeedm, ajayachandra, jgg, parav, leonro, witu,
hughd, skhawaja, chrisl, steven.sistare
This series introduces the Live Update Orchestrator (LUO), a kernel
subsystem designed to facilitate live kernel updates. LUO enables
kexec-based reboots with minimal downtime, a critical capability for
cloud environments where hypervisors must be updated without disrupting
running virtual machines. By preserving the state of selected resources,
such as file descriptors and memory, LUO allows workloads to resume
seamlessly in the new kernel.
The git branch for this series can be found at:
https://github.com/googleprodkernel/linux-liveupdate/tree/luo/v4
The patch series applies against linux-next tag: next-20250926
While this series is showed cased using memfd preservation. There are
works to preserve devices:
1. IOMMU: https://lore.kernel.org/all/20250928190624.3735830-16-skhawaja@google.com
2. PCI: https://lore.kernel.org/all/20250916-luo-pci-v2-0-c494053c3c08@kernel.org
=======================================================================
Changelog since v3:
(https://lore.kernel.org/all/20250807014442.3829950-1-pasha.tatashin@soleen.com):
- The main architectural change in this version is introduction of
"sessions" to manage the lifecycle of preserved file descriptors.
In v3, session management was left to a single userspace agent. This
approach has been revised to improve robustness. Now, each session is
represented by a file descriptor (/dev/liveupdate). The lifecycle of
all preserved resources within a session is tied to this FD, ensuring
automatic cleanup by the kernel if the controlling userspace agent
crashes or exits unexpectedly.
- The first three KHO fixes from the previous series have been merged
into Linus' tree.
- Various bug fixes and refactorings, including correcting memory
unpreservation logic during a kho_abort() sequence.
- Addressing all comments from reviewers.
- Removing sysfs interface (/sys/kernel/liveupdate/state), the state
can now be queried only via ioctl() API.
=======================================================================
What is Live Update?
Live Update is a kexec-based reboot process where selected kernel
resources (memory, file descriptors, and eventually devices) are kept
operational or their state is preserved across a kernel transition. For
certain resources, DMA and interrupt activity might continue with
minimal interruption during the kernel reboot.
LUO provides a framework for coordinating live updates. It features:
State Machine
Manages the live update process through states: NORMAL, PREPARED,
FROZEN, UPDATED.
Session Management
==================
Userspace creates named sessions (driven by LUOD: Live Update
Orchestrator Daemon, see: https://tinyurl.com/luoddesign), each
represented by a file descriptor. Preserved resources are tied to a
session, and their lifecycle is managed by the session's FD, ensuring
automatic cleanup if the controlling process exits unexpectedly.
Furthermore, sessions can be finished, prepared, and frozen
independently of the global LUO states. This granular control allows a
VMM to serialize and resume specific VMs as soon as their resources are
ready, without having to wait for all VMs to be prepared.
After a reboot, a central live update agent can retrieve a session
handle and pass it to the VMM process, which then restores its own file
descriptors. This ensures that resource allocations, such as cgroup
memory charges, are correctly accounted against the workload's cgroup
instead of the administrative agent's.
KHO Integration
===============
LUO programmatically drives KHO's finalization and abort sequences
(KHO may soon to become completely stateless, which will make KHO
interraction with LUO even simpler:
https://lore.kernel.org/all/20250917025019.1585041-1-jasonmiu@google.com)
KHO's debugfs interface is now optional, configured via
CONFIG_KEXEC_HANDOVER_DEBUG. LUO preserves its own metadata via KHO's
kho_add_subtree() and kho_preserve_phys() mechanisms.
Subsystem Participation
=======================
A callback API, liveupdate_register_subsystem(), allows kernel
subsystems (e.g., KVM, IOMMU, VFIO, PCI) to register handlers for LUO
events (PREPARE, FREEZE, FINISH, CANCEL) and persist a u64 payload via
the LUO FDT.
File Descriptor Preservation
============================
An infrastructure (liveupdate_register_file_handler, luo_preserve_file,
luo_retrieve_file) allows specific types of file descriptors (e.g.,
memfd, vfio) to be preserved and restored within a session. Handlers for
specific file types can be registered to manage their preservation,
storing a u64 payload in the LUO FDT.
Userspace Interface
===================
ioctl (/dev/liveupdate): The primary control interface for creating and
retrieving sessions, triggering global LUO state transitions (prepare,
finish, cancel), and managing preserved file descriptors within a
session.
sysfs (/sys/kernel/liveupdate/state)
A read-only interface for monitoring the current LUO state.
Selftests
=========
Includes kernel-side hooks and an extensive userspace selftest suite to
verify core LUO functionality, including subsystem registration, state
transitions, and complex multi-kexec session lifecycles.
LUO State Machine and Events
============================
NORMAL: Default operational state.
PREPARED: Initial preparation complete after LIVEUPDATE_PREPARE event.
Subsystems have saved initial state.
FROZEN: Final "blackout window" state after LIVEUPDATE_FREEZE event,
just before kexec. Workloads must be suspended.
UPDATED: Next kernel has booted via live update, awaiting restoration
and LIVEUPDATE_FINISH.
Events
LIVEUPDATE_PREPARE: Prepare for reboot, serialize state.
LIVEUPDATE_FREEZE: Final opportunity to save state before kexec.
LIVEUPDATE_FINISH: Post-reboot cleanup in the next kernel.
LIVEUPDATE_CANCEL: Abort prepare or freeze, revert changes.
Mike Rapoport (Microsoft) (1):
kho: drop notifiers
Pasha Tatashin (24):
kho: allow to drive kho from within kernel
kho: make debugfs interface optional
kho: add interfaces to unpreserve folios and page ranes
kho: don't unpreserve memory during abort
liveupdate: kho: move to kernel/liveupdate
liveupdate: luo_core: luo_ioctl: Live Update Orchestrator
liveupdate: luo_core: integrate with KHO
liveupdate: luo_subsystems: add subsystem registration
liveupdate: luo_subsystems: implement subsystem callbacks
liveupdate: luo_session: Add sessions support
liveupdate: luo_ioctl: add user interface
liveupdate: luo_file: implement file systems callbacks
liveupdate: luo_session: Add ioctls for file preservation and state
management
reboot: call liveupdate_reboot() before kexec
kho: move kho debugfs directory to liveupdate
liveupdate: add selftests for subsystems un/registration
selftests/liveupdate: add subsystem/state tests
docs: add luo documentation
MAINTAINERS: add liveupdate entry
selftests/liveupdate: Add multi-kexec session lifecycle test
selftests/liveupdate: Add multi-file and unreclaimed file test
selftests/liveupdate: Add multi-session workflow and state interaction
test
selftests/liveupdate: Add test for unreclaimed resource cleanup
selftests/liveupdate: Add tests for per-session state and cancel
cycles
Pratyush Yadav (5):
mm: shmem: use SHMEM_F_* flags instead of VM_* flags
mm: shmem: allow freezing inode mapping
mm: shmem: export some functions to internal.h
luo: allow preserving memfd
docs: add documentation for memfd preservation via LUO
Documentation/core-api/index.rst | 1 +
Documentation/core-api/kho/concepts.rst | 2 +-
Documentation/core-api/liveupdate.rst | 64 ++
Documentation/mm/index.rst | 1 +
Documentation/mm/memfd_preservation.rst | 138 +++
Documentation/userspace-api/index.rst | 1 +
.../userspace-api/ioctl/ioctl-number.rst | 2 +
Documentation/userspace-api/liveupdate.rst | 25 +
MAINTAINERS | 18 +-
include/linux/kexec_handover.h | 53 +-
include/linux/liveupdate.h | 209 +++++
include/linux/shmem_fs.h | 23 +
include/uapi/linux/liveupdate.h | 460 +++++++++
init/Kconfig | 2 +
kernel/Kconfig.kexec | 15 -
kernel/Makefile | 2 +-
kernel/liveupdate/Kconfig | 72 ++
kernel/liveupdate/Makefile | 14 +
kernel/{ => liveupdate}/kexec_handover.c | 507 ++++------
kernel/liveupdate/kexec_handover_debug.c | 222 +++++
kernel/liveupdate/kexec_handover_internal.h | 45 +
kernel/liveupdate/luo_core.c | 588 ++++++++++++
kernel/liveupdate/luo_file.c | 599 ++++++++++++
kernel/liveupdate/luo_internal.h | 114 +++
kernel/liveupdate/luo_ioctl.c | 255 +++++
kernel/liveupdate/luo_selftests.c | 345 +++++++
kernel/liveupdate/luo_selftests.h | 84 ++
kernel/liveupdate/luo_session.c | 887 ++++++++++++++++++
kernel/liveupdate/luo_subsystems.c | 452 +++++++++
kernel/reboot.c | 4 +
mm/Makefile | 1 +
mm/internal.h | 6 +
mm/memblock.c | 60 +-
mm/memfd_luo.c | 523 +++++++++++
mm/shmem.c | 51 +-
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/liveupdate/.gitignore | 2 +
tools/testing/selftests/liveupdate/Makefile | 48 +
tools/testing/selftests/liveupdate/config | 6 +
.../testing/selftests/liveupdate/do_kexec.sh | 6 +
.../testing/selftests/liveupdate/liveupdate.c | 404 ++++++++
.../selftests/liveupdate/luo_multi_file.c | 119 +++
.../selftests/liveupdate/luo_multi_kexec.c | 182 ++++
.../selftests/liveupdate/luo_multi_session.c | 155 +++
.../selftests/liveupdate/luo_test_utils.c | 241 +++++
.../selftests/liveupdate/luo_test_utils.h | 51 +
.../selftests/liveupdate/luo_unreclaimed.c | 107 +++
47 files changed, 6757 insertions(+), 410 deletions(-)
create mode 100644 Documentation/core-api/liveupdate.rst
create mode 100644 Documentation/mm/memfd_preservation.rst
create mode 100644 Documentation/userspace-api/liveupdate.rst
create mode 100644 include/linux/liveupdate.h
create mode 100644 include/uapi/linux/liveupdate.h
create mode 100644 kernel/liveupdate/Kconfig
create mode 100644 kernel/liveupdate/Makefile
rename kernel/{ => liveupdate}/kexec_handover.c (80%)
create mode 100644 kernel/liveupdate/kexec_handover_debug.c
create mode 100644 kernel/liveupdate/kexec_handover_internal.h
create mode 100644 kernel/liveupdate/luo_core.c
create mode 100644 kernel/liveupdate/luo_file.c
create mode 100644 kernel/liveupdate/luo_internal.h
create mode 100644 kernel/liveupdate/luo_ioctl.c
create mode 100644 kernel/liveupdate/luo_selftests.c
create mode 100644 kernel/liveupdate/luo_selftests.h
create mode 100644 kernel/liveupdate/luo_session.c
create mode 100644 kernel/liveupdate/luo_subsystems.c
create mode 100644 mm/memfd_luo.c
create mode 100644 tools/testing/selftests/liveupdate/.gitignore
create mode 100644 tools/testing/selftests/liveupdate/Makefile
create mode 100644 tools/testing/selftests/liveupdate/config
create mode 100755 tools/testing/selftests/liveupdate/do_kexec.sh
create mode 100644 tools/testing/selftests/liveupdate/liveupdate.c
create mode 100644 tools/testing/selftests/liveupdate/luo_multi_file.c
create mode 100644 tools/testing/selftests/liveupdate/luo_multi_kexec.c
create mode 100644 tools/testing/selftests/liveupdate/luo_multi_session.c
create mode 100644 tools/testing/selftests/liveupdate/luo_test_utils.c
create mode 100644 tools/testing/selftests/liveupdate/luo_test_utils.h
create mode 100644 tools/testing/selftests/liveupdate/luo_unreclaimed.c
--
2.51.0.536.g15c5d4f767-goog
^ permalink raw reply
* Re: [PATCH v2 0/3] ext4: Add support for mounted updates to the superblock via an ioctl
From: Theodore Ts'o @ 2025-09-26 21:47 UTC (permalink / raw)
To: Theodore Ts'o; +Cc: linux-ext4, linux-api, stable
In-Reply-To: <20250916-tune2fs-v2-0-d594dc7486f0@mit.edu>
On Tue, 16 Sep 2025 23:22:46 -0400, Theodore Ts'o wrote:
> This patch series enables a future version of tune2fs to be able to
> modify certain parts of the ext4 superblock without to write to the
> block device.
>
> The first patch fixes a potential buffer overrun caused by a
> maliciously moified superblock. The second patch adds support for
> 32-bit uid and gid's which can have access to the reserved blocks pool.
> The last patch adds the ioctl's which will be used by tune2fs.
>
> [...]
Applied, thanks!
[1/3] ext4: avoid potential buffer over-read in parse_apply_sb_mount_options()
commit: 8ecb790ea8c3fc69e77bace57f14cf0d7c177bd8
[2/3] ext4: add support for 32-bit default reserved uid and gid values
commit: 12c84dd4d308551568d85203fd6ed2685e861fda
[3/3] ext4: implemet new ioctls to set and get superblock parameters
commit: 04a91570ac67760301e5458d65eaf1342ecca314
Best regards,
--
Theodore Ts'o <tytso@mit.edu>
^ permalink raw reply
page: next (older) | prev (newer) | latest
- recent:[subjects (threaded)|topics (new)|topics (active)]
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox