Commit 0153094d authored by Pasha Tatashin's avatar Pasha Tatashin Committed by Andrew Morton
Browse files

liveupdate: luo_session: add sessions support 

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.

[dan.carpenter@linaro.org: fix use after free in luo_session_deserialize()]
  Link: https://lkml.kernel.org/r/c5dd637d7eed3a3be48c5e9fedb881596a3b1f5a.1764163896.git.dan.carpenter@linaro.org
Link: https://lkml.kernel.org/r/20251125165850.3389713-5-pasha.tatashin@soleen.com


Signed-off-by: default avatarPasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: default avatarDan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: default avatarMike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: default avatarPratyush Yadav <pratyush@kernel.org>
Tested-by: default avatarDavid Matlack <dmatlack@google.com>
Cc: Aleksander Lobakin <aleksander.lobakin@intel.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andriy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: anish kumar <yesanishhere@gmail.com>
Cc: Anna Schumaker <anna.schumaker@oracle.com>
Cc: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Chanwoo Choi <cw00.choi@samsung.com>
Cc: Chen Ridong <chenridong@huawei.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Daniel Wagner <wagi@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Jeffery <djeffery@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guixin Liu <kanie@linux.alibaba.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joanthan Cameron <Jonathan.Cameron@huawei.com>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Leon Romanovsky <leonro@nvidia.com>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Myugnjoo Ham <myungjoo.ham@samsung.com>
Cc: Parav Pandit <parav@nvidia.com>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: Samiullah Khawaja <skhawaja@google.com>
Cc: Song Liu <song@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Stuart Hayes <stuart.w.hayes@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: William Tu <witu@nvidia.com>
Cc: Yoann Congal <yoann.congal@smile.fr>
Cc: Zhu Yanjun <yanjun.zhu@linux.dev>
Cc: Zijun Hu <quic_zijuhu@quicinc.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent db8bed80

include/linux/kho/abi/luo.h

+71 −0
Original line number Diff line number Diff line
@@ -32,6 +32,11 @@ 
 *     / {

 *         compatible = "luo-v1";

 *         liveupdate-number = <...>;

 *

 *         luo-session {

 *             compatible = "luo-session-v1";

 *             luo-session-header = <phys_addr_of_session_header_ser>;

 *         };

 *     };

 *

 * Main LUO Node (/):
@@ -40,11 +45,37 @@ 
 *     Identifies the overall LUO ABI version.

 *   - liveupdate-number: u64

 *     A counter tracking the number of successful live updates performed.

 *

 * Session Node (luo-session):

 *   This node describes all preserved user-space sessions.

 *

 *   - compatible: "luo-session-v1"

 *     Identifies the session ABI version.

 *   - luo-session-header: u64

 *     The physical address of a `struct luo_session_header_ser`. This structure

 *     is the header for a contiguous block of memory containing an array of

 *     `struct luo_session_ser`, one for each preserved session.

 *

 * Serialization Structures:

 *   The FDT properties point to memory regions containing arrays of simple,

 *   `__packed` structures. These structures contain the actual preserved state.

 *

 *   - struct luo_session_header_ser:

 *     Header for the session array. Contains the total page count of the

 *     preserved memory block and the number of `struct luo_session_ser`

 *     entries that follow.

 *

 *   - struct luo_session_ser:

 *     Metadata for a single session, including its name and a physical pointer

 *     to another preserved memory block containing an array of

 *     `struct luo_file_ser` for all files in that session.

 */



#ifndef _LINUX_KHO_ABI_LUO_H

#define _LINUX_KHO_ABI_LUO_H



#include <uapi/linux/liveupdate.h>



/*

 * The LUO FDT hooks all LUO state for sessions, fds, etc.

 * In the root it also carries "liveupdate-number" 64-bit property that
@@ -55,4 +86,44 @@ 
#define LUO_FDT_COMPATIBLE	"luo-v1"

#define LUO_FDT_LIVEUPDATE_NUM	"liveupdate-number"



/*

 * LUO FDT session node

 * LUO_FDT_SESSION_HEADER:  is a u64 physical address of struct

 *                          luo_session_header_ser

 */

#define LUO_FDT_SESSION_NODE_NAME	"luo-session"

#define LUO_FDT_SESSION_COMPATIBLE	"luo-session-v1"

#define LUO_FDT_SESSION_HEADER		"luo-session-header"



/**

 * struct luo_session_header_ser - Header for the serialized session data block.

 * @count: The number of `struct luo_session_ser` entries that immediately

 *         follow this header in the memory block.

 *

 * This structure is located at the beginning of a contiguous block of

 * physical memory preserved across the kexec. It provides the necessary

 * metadata to interpret the array of session entries that follow.

 *

 * If this structure is modified, `LUO_FDT_SESSION_COMPATIBLE` must be updated.

 */

struct luo_session_header_ser {

	u64 count;

} __packed;



/**

 * struct luo_session_ser - Represents the serialized metadata for a LUO session.

 * @name:         The unique name of the session, provided by the userspace at

 *                the time of session creation.

 *

 * 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_FDT_SESSION_COMPATIBLE` must be updated.

 */

struct luo_session_ser {

	char name[LIVEUPDATE_SESSION_NAME_LENGTH];

} __packed;



#endif /* _LINUX_KHO_ABI_LUO_H */

include/uapi/linux/liveupdate.h

+3 −0
Original line number Diff line number Diff line
@@ -43,4 +43,7 @@ 
/* The ioctl type, documented in ioctl-number.rst */

#define LIVEUPDATE_IOCTL_TYPE		0xBA



/* The maximum length of session name including null termination */

#define LIVEUPDATE_SESSION_NAME_LENGTH 64



#endif /* _UAPI_LIVEUPDATE_H */

kernel/liveupdate/Makefile

+2 −1
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0



luo-y :=								\

		luo_core.o

		luo_core.o						\

		luo_session.o



obj-$(CONFIG_KEXEC_HANDOVER)		+= kexec_handover.o

obj-$(CONFIG_KEXEC_HANDOVER_DEBUG)	+= kexec_handover_debug.o

kernel/liveupdate/luo_core.c

+9 −0
Original line number Diff line number Diff line
@@ -118,6 +118,10 @@ static int __init luo_early_startup(void) 
	pr_info("Retrieved live update data, liveupdate number: %lld\n",

		luo_global.liveupdate_num);



	err = luo_session_setup_incoming(luo_global.fdt_in);

	if (err)

		return err;



	return 0;

}
@@ -154,6 +158,7 @@ static int __init luo_fdt_setup(void) 
	err |= fdt_begin_node(fdt_out, "");

	err |= fdt_property_string(fdt_out, "compatible", LUO_FDT_COMPATIBLE);

	err |= fdt_property(fdt_out, LUO_FDT_LIVEUPDATE_NUM, &ln, sizeof(ln));

	err |= luo_session_setup_outgoing(fdt_out);

	err |= fdt_end_node(fdt_out);

	err |= fdt_finish(fdt_out);

	if (err)
@@ -211,6 +216,10 @@ int liveupdate_reboot(void) 
	if (!liveupdate_enabled())

		return 0;



	err = luo_session_serialize();

	if (err)

		return err;



	err = kho_finalize();

	if (err) {

		pr_err("kho_finalize failed %d\n", err);

kernel/liveupdate/luo_internal.h

+29 −0
Original line number Diff line number Diff line
@@ -19,4 +19,33 @@ 
 */

#define luo_restore_fail(__fmt, ...) panic(__fmt, ##__VA_ARGS__)



/**

 * struct luo_session - Represents an active or incoming Live Update session.

 * @name:       A unique name for this session, used for identification and

 *              retrieval.

 * @ser:        Pointer to the serialized data 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.

 * @mutex:      protects fields in the luo_session.

 */

struct luo_session {

	char name[LIVEUPDATE_SESSION_NAME_LENGTH];

	struct luo_session_ser *ser;

	struct list_head list;

	bool retrieved;

	struct mutex mutex;

};



int luo_session_create(const char *name, struct file **filep);

int luo_session_retrieve(const char *name, struct file **filep);

int __init luo_session_setup_outgoing(void *fdt);

int __init luo_session_setup_incoming(void *fdt);

int luo_session_serialize(void);

int luo_session_deserialize(void);

bool luo_session_quiesce(void);

void luo_session_resume(void);



#endif /* _LINUX_LUO_INTERNAL_H */