Changes in Kconfig

c6073743d0c7f011461bc542c9112180471affad - kho: make preserved pages compatible with deferred struct page init

Thu, 23 Apr 2026 14:25:37 +0200

kho: make preserved pages compatible with deferred struct page initWhen CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled, struct pageinitialization is deferred to parallel kthreads that run laterin the boot process.During KHO restoration, kho_preserved_memory_reserve() writes metadatafor each preserved memory region. However, if the struct page has notbeen initialized, this write targets uninitialized memory, potentiallyleading to errors like:BUG: unable to handle page fault for address: ...Fix this by introducing kho_get_preserved_page(), which ensuresall struct pages in a preserved region are initialized by callinginit_deferred_page() which is a no-op when the struct page is alreadyinitialized.Signed-off-by: Evangelos Petrongonas Co-developed-by: Michal Clapinski Signed-off-by: Michal Clapinski Reviewed-by: Pratyush Yadav (Google) Reviewed-by: Pasha Tatashin Reviewed-by: Mike Rapoport (Microsoft) Link: https://patch.msgid.link/20260423122538.140993-3-mclapinski@google.comSigned-off-by: Mike Rapoport (Microsoft) List of files: /linux/kernel/liveupdate/Kconfig

998be0a4dbcaa796a05c7b52327f3a09c29d3662 - liveupdate: separate memfd support into LIVEUPDATE_MEMFD

Tue, 30 Dec 2025 17:14:02 +0100

liveupdate: separate memfd support into LIVEUPDATE_MEMFDDecouple memfd preservation support from the core Live Update Orchestratorconfiguration.Previously, enabling CONFIG_LIVEUPDATE forced a dependency on CONFIG_SHMEMand unconditionally compiled memfd_luo.o. However, Live Update may beused for purposes that do not require memfd-backed memory preservation.Introduce CONFIG_LIVEUPDATE_MEMFD to gate memfd_luo.o. This moves theSHMEM and MEMFD_CREATE dependencies to the specific feature that needsthem, allowing the base LIVEUPDATE option to be selected independently ofshared memory support.Link: https://lkml.kernel.org/r/20251230161402.1542099-1-pasha.tatashin@soleen.comSigned-off-by: Pasha Tatashin Reviewed-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) Signed-off-by: Andrew Morton List of files: /linux/kernel/liveupdate/Kconfig

601cc399a01049efa76be8f496541315dc9cf914 - mm: memfd_luo: add CONFIG_SHMEM dependency

Thu, 04 Dec 2025 11:01:58 +0100

mm: memfd_luo: add CONFIG_SHMEM dependencyThe new memfd code fails to link without SHMEM:aarch64-linux-ld: mm/memfd_luo.o: in function `memfd_luo_retrieve_folios':memfd_luo.c:(.text.memfd_luo_retrieve_folios+0xdc): undefined reference to `shmem_add_to_page_cache'memfd_luo.c:(.text.memfd_luo_retrieve_folios+0x11c): undefined reference to `shmem_inode_acct_blocks'memfd_luo.c:(.text.memfd_luo_retrieve_folios+0x134): undefined reference to `shmem_recalc_inode'Add a Kconfig dependency to disallow that configuration.Link: https://lkml.kernel.org/r/20251204100203.1034394-1-arnd@kernel.orgFixes: b3749f174d68 ("mm: memfd_luo: allow preserving memfd")Signed-off-by: Arnd Bergmann Reviewed-by: Pratyush Yadav Acked-by: Mike Rapoport (Microsoft) Reviewed-by: Pasha Tatashin Signed-off-by: Andrew Morton List of files: /linux/kernel/liveupdate/Kconfig

9e2fd062fa1713a33380cc97ef324d086dd45ba5 - liveupdate: luo_core: Live Update Orchestrator

Tue, 25 Nov 2025 17:58:31 +0100

liveupdate: luo_core: Live Update OrchestratorPatch series "Live Update Orchestrator", v8.This series introduces the Live Update Orchestrator, a kernel subsystemdesigned to facilitate live kernel updates using a kexec-based reboot. This capability is critical for cloud environments, allowing hypervisorsto be updated with minimal downtime for running virtual machines. LUOachieves this by preserving the state of selected resources, such asmemory, devices and their dependencies, across the kernel transition.As a key feature, this series includes support for preserving memfd filedescriptors, which allows critical in-memory data, such as guest RAM orany other large memory region, to be maintained in RAM across the kexecreboot.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 preservedresources 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 whilekeeping designated devices operational across the transition (e.g., viakexec). The primary use case is updating hypervisors with minimaldisruption to running virtual machines. For userspace side of hypervisorupdate 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 transitionlogic, integration with KHO, and hooks for subsystems and filedescriptors, will be added in subsequent patches.Create a character device at /dev/liveupdate.A new uAPI header, , will define the necessarystructures. The magic number for IOCTL is registered inDocumentation/userspace-api/ioctl/ioctl-number.rst.Link: https://lkml.kernel.org/r/20251125165850.3389713-1-pasha.tatashin@soleen.comLink: https://lkml.kernel.org/r/20251125165850.3389713-2-pasha.tatashin@soleen.comLink: 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 Reviewed-by: Pratyush Yadav Reviewed-by: Mike Rapoport (Microsoft) Tested-by: David Matlack Cc: Aleksander Lobakin Cc: Alexander Graf Cc: Alice Ryhl Cc: Andriy Shevchenko Cc: anish kumar Cc: Anna Schumaker Cc: Bartosz Golaszewski Cc: Bjorn Helgaas Cc: Borislav Betkov Cc: Chanwoo Choi Cc: Chen Ridong Cc: Chris Li Cc: Christian Brauner Cc: Daniel Wagner Cc: Danilo Krummrich Cc: Dan Williams Cc: David Hildenbrand Cc: David Jeffery Cc: David Rientjes Cc: Greg Kroah-Hartman Cc: Guixin Liu Cc: "H. Peter Anvin" Cc: Hugh Dickins Cc: Ilpo Järvinen Cc: Ingo Molnar Cc: Ira Weiny Cc: Jann Horn Cc: Jason Gunthorpe Cc: Jens Axboe Cc: Joanthan Cameron Cc: Joel Granados Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Lennart Poettering Cc: Leon Romanovsky Cc: Leon Romanovsky Cc: Lukas Wunner Cc: Marc Rutland Cc: Masahiro Yamada Cc: Matthew Maurer Cc: Miguel Ojeda Cc: Myugnjoo Ham Cc: Parav Pandit Cc: Randy Dunlap Cc: Roman Gushchin Cc: Saeed Mahameed Cc: Samiullah Khawaja Cc: Song Liu Cc: Steven Rostedt Cc: Stuart Hayes Cc: Tejun Heo Cc: Thomas Gleinxer Cc: Thomas Weißschuh Cc: Vincent Guittot Cc: William Tu Cc: Yoann Congal Cc: Zijun Hu Cc: Pratyush Yadav Cc: Zhu Yanjun Signed-off-by: Andrew Morton List of files: /linux/kernel/liveupdate/Kconfig

7bd3643f94a357863beef646b85cf10292398629 - kho: add Kconfig option to enable KHO by default

Fri, 14 Nov 2025 20:00:02 +0100

kho: add Kconfig option to enable KHO by defaultCurrently, Kexec Handover must be explicitly enabled via the kernelcommand line parameter `kho=on`.For workloads that rely on KHO as a foundational requirement (such as theupcoming Live Update Orchestrator), requiring an explicit boot parameteradds redundant configuration steps.Introduce CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT. When selected, KHOdefaults to enabled. This is equivalent to passing kho=on at boot. Thebehavior can still be disabled at runtime by passing kho=off.Link: https://lkml.kernel.org/r/20251114190002.3311679-14-pasha.tatashin@soleen.comSigned-off-by: Pasha Tatashin Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Pratyush Yadav Cc: Alexander Graf Cc: Arnd Bergmann Cc: Baoquan He Cc: Coiby Xu Cc: Dave Vasilevsky Cc: Eric Biggers Cc: Kees Cook Signed-off-by: Andrew Morton List of files: /linux/kernel/liveupdate/Kconfig

48a1b2321d763b5edeaf20bd4576d8c4b5df772b - liveupdate: kho: move to kernel/liveupdate

Sat, 01 Nov 2025 15:23:23 +0100

liveupdate: kho: move to kernel/liveupdateMove KHO to kernel/liveupdate/ in preparation of placing all Live Updatecore kernel related files to the same place.[pasha.tatashin@soleen.com: disable the menu when DEFERRED_STRUCT_PAGE_INIT] Link: https://lkml.kernel.org/r/CA+CK2bAvh9Oa2SLfsbJ8zztpEjrgr_hr-uGgF1coy8yoibT39A@mail.gmail.comLink: https://lkml.kernel.org/r/20251101142325.1326536-8-pasha.tatashin@soleen.comSigned-off-by: Pasha Tatashin Reviewed-by: Jason Gunthorpe Reviewed-by: Mike Rapoport (Microsoft) Cc: Alexander Graf Cc: Changyuan Lyu Cc: Christian Brauner Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Masahiro Yamada Cc: Miguel Ojeda Cc: Pratyush Yadav Cc: Randy Dunlap Cc: Simon Horman Cc: Tejun Heo Cc: Zhu Yanjun Signed-off-by: Andrew Morton List of files: /linux/kernel/liveupdate/Kconfig