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Author SHA1 Message Date
Pasha Tatashin
81cd25d263 liveupdate: luo_core: add user interface 
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_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.

Link: https://lkml.kernel.org/r/20251125165850.3389713-6-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Tested-by: David 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: Andrew Morton <akpm@linux-foundation.org>
 2025-11-27 14:24:38 -08:00
Pasha Tatashin
0153094d03 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: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Tested-by: David 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: Andrew Morton <akpm@linux-foundation.org>
 2025-11-27 14:24:38 -08:00
Pasha Tatashin
1aece82100 liveupdate: luo_core: integrate with KHO 
Integrate the LUO with the KHO framework to enable passing LUO state
across a kexec reboot.

This patch implements the lifecycle integration with KHO:

1. Incoming State: During early boot (`early_initcall`), LUO checks if
   KHO is active. If so, it retrieves the "LUO" subtree, verifies the
   "luo-v1" compatibility string, and reads the `liveupdate-number` to
   track the update count.

2. Outgoing State: During late initialization (`late_initcall`), LUO
   allocates a new FDT for the next kernel, populates it with the basic
   header (compatible string and incremented update number), and
   registers it with KHO (`kho_add_subtree`).

3. Finalization: The `liveupdate_reboot()` notifier is updated to invoke
   `kho_finalize()`. This ensures that all memory segments marked for
   preservation are properly serialized before the kexec jump.

Link: https://lkml.kernel.org/r/20251125165850.3389713-3-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Tested-by: David Matlack <dmatlack@google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
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: Andrew Morton <akpm@linux-foundation.org>
 2025-11-27 14:24:37 -08:00
Pasha Tatashin
9e2fd062fa liveupdate: luo_core: Live Update Orchestrator 
Patch series "Live Update Orchestrator", v8.

This series introduces the Live Update Orchestrator, a kernel subsystem
designed to facilitate live kernel updates using a kexec-based reboot. 
This capability is critical for cloud environments, allowing hypervisors
to be updated with minimal downtime for running virtual machines.  LUO
achieves this by preserving the state of selected resources, such as
memory, devices and their dependencies, across the kernel transition.

As a key feature, this series includes support for preserving memfd file
descriptors, which allows critical in-memory data, such as guest RAM or
any other large memory region, to be maintained in RAM across the kexec
reboot.

The other series that use LUO, are VFIO [1], IOMMU [2], and PCI [3]
preservations.

Github repo of this series [4].

The core of LUO is a framework for managing the lifecycle of preserved
resources through a userspace-driven interface. Key features include:

- Session Management
  Userspace agent (i.e. luod [5]) creates named sessions, each
  represented by a file descriptor (via centralized agent that controls
  /dev/liveupdate). The lifecycle of all preserved resources within a
  session is tied to this FD, ensuring automatic kernel cleanup if the
  controlling userspace agent crashes or exits unexpectedly.

- File Preservation
  A handler-based framework allows specific file types (demonstrated
  here with memfd) to be preserved. Handlers manage the serialization,
  restoration, and lifecycle of their specific file types.

- File-Lifecycle-Bound State
  A new mechanism for managing shared global state whose lifecycle is
  tied to the preservation of one or more files. This is crucial for
  subsystems like IOMMU or HugeTLB, where multiple file descriptors may
  depend on a single, shared underlying resource that must be preserved
  only once.

- KHO Integration
  LUO drives the Kexec Handover framework programmatically to pass its
  serialized metadata to the next kernel. The LUO state is finalized and
  added to the kexec image just before the reboot is triggered. In the
  future this step will also be removed once stateless KHO is
  merged [6].

- Userspace Interface
  Control is provided via ioctl commands on /dev/liveupdate for creating
  and retrieving sessions, as well as on session file descriptors for
  managing individual files.

- Testing
  The series includes a set of selftests, including userspace API
  validation, kexec-based lifecycle tests for various session and file
  scenarios, and a new in-kernel test module to validate the FLB logic.




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.

Link: https://lkml.kernel.org/r/20251125165850.3389713-1-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20251125165850.3389713-2-pasha.tatashin@soleen.com
Link: https://lore.kernel.org/all/20251018000713.677779-1-vipinsh@google.com/ [1]
Link: https://lore.kernel.org/linux-iommu/20250928190624.3735830-1-skhawaja@google.com [2]
Link: https://lore.kernel.org/linux-pci/20250916-luo-pci-v2-0-c494053c3c08@kernel.org [3]
Link: https://github.com/googleprodkernel/linux-liveupdate/tree/luo/v8 [4]
Link: https://tinyurl.com/luoddesign [5]
Link: https://lore.kernel.org/all/20251020100306.2709352-1-jasonmiu@google.com [6]
Link: https://lore.kernel.org/all/20251115233409.768044-1-pasha.tatashin@soleen.com [7]
Link: https://github.com/soleen/linux/blob/luo/v8b03/diff.v7.v8 [8]
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Tested-by: David 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: 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: Zijun Hu <quic_zijuhu@quicinc.com>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Zhu Yanjun <yanjun.zhu@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
 2025-11-27 14:24:37 -08:00