Linux kernel stable tree (mirror) https://git.radix-linux.su/kernel/linux.git/atom?h=master 2026-04-15T19:59:16+00:00 2026-04-15T19:59:16+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-04-15T19:59:16+00:00 urn:sha1:334fbe734e687404f346eba7d5d96ed2b44d35ab Pull MM updates from Andrew Morton: - "maple_tree: Replace big node with maple copy" (Liam Howlett) Mainly prepararatory work for ongoing development but it does reduce stack usage and is an improvement. - "mm, swap: swap table phase III: remove swap_map" (Kairui Song) Offers memory savings by removing the static swap_map. It also yields some CPU savings and implements several cleanups. - "mm: memfd_luo: preserve file seals" (Pratyush Yadav) File seal preservation to LUO's memfd code - "mm: zswap: add per-memcg stat for incompressible pages" (Jiayuan Chen) Additional userspace stats reportng to zswap - "arch, mm: consolidate empty_zero_page" (Mike Rapoport) Some cleanups for our handling of ZERO_PAGE() and zero_pfn - "mm/kmemleak: Improve scan_should_stop() implementation" (Zhongqiu Han) A robustness improvement and some cleanups in the kmemleak code - "Improve khugepaged scan logic" (Vernon Yang) Improve khugepaged scan logic and reduce CPU consumption by prioritizing scanning tasks that access memory frequently - "Make KHO Stateless" (Jason Miu) Simplify Kexec Handover by transitioning KHO from an xarray-based metadata tracking system with serialization to a radix tree data structure that can be passed directly to the next kernel - "mm: vmscan: add PID and cgroup ID to vmscan tracepoints" (Thomas Ballasi and Steven Rostedt) Enhance vmscan's tracepointing - "mm: arch/shstk: Common shadow stack mapping helper and VM_NOHUGEPAGE" (Catalin Marinas) Cleanup for the shadow stack code: remove per-arch code in favour of a generic implementation - "Fix KASAN support for KHO restored vmalloc regions" (Pasha Tatashin) Fix a WARN() which can be emitted the KHO restores a vmalloc area - "mm: Remove stray references to pagevec" (Tal Zussman) Several cleanups, mainly udpating references to "struct pagevec", which became folio_batch three years ago - "mm: Eliminate fake head pages from vmemmap optimization" (Kiryl Shutsemau) Simplify the HugeTLB vmemmap optimization (HVO) by changing how tail pages encode their relationship to the head page - "mm/damon/core: improve DAMOS quota efficiency for core layer filters" (SeongJae Park) Improve two problematic behaviors of DAMOS that makes it less efficient when core layer filters are used - "mm/damon: strictly respect min_nr_regions" (SeongJae Park) Improve DAMON usability by extending the treatment of the min_nr_regions user-settable parameter - "mm/page_alloc: pcp locking cleanup" (Vlastimil Babka) The proper fix for a previously hotfixed SMP=n issue. Code simplifications and cleanups ensued - "mm: cleanups around unmapping / zapping" (David Hildenbrand) A bunch of cleanups around unmapping and zapping. Mostly simplifications, code movements, documentation and renaming of zapping functions - "support batched checking of the young flag for MGLRU" (Baolin Wang) Batched checking of the young flag for MGLRU. It's part cleanups; one benchmark shows large performance benefits for arm64 - "memcg: obj stock and slab stat caching cleanups" (Johannes Weiner) memcg cleanup and robustness improvements - "Allow order zero pages in page reporting" (Yuvraj Sakshith) Enhance free page reporting - it is presently and undesirably order-0 pages when reporting free memory. - "mm: vma flag tweaks" (Lorenzo Stoakes) Cleanup work following from the recent conversion of the VMA flags to a bitmap - "mm/damon: add optional debugging-purpose sanity checks" (SeongJae Park) Add some more developer-facing debug checks into DAMON core - "mm/damon: test and document power-of-2 min_region_sz requirement" (SeongJae Park) An additional DAMON kunit test and makes some adjustments to the addr_unit parameter handling - "mm/damon/core: make passed_sample_intervals comparisons overflow-safe" (SeongJae Park) Fix a hard-to-hit time overflow issue in DAMON core - "mm/damon: improve/fixup/update ratio calculation, test and documentation" (SeongJae Park) A batch of misc/minor improvements and fixups for DAMON - "mm: move vma_(kernel|mmu)_pagesize() out of hugetlb.c" (David Hildenbrand) Fix a possible issue with dax-device when CONFIG_HUGETLB=n. Some code movement was required. - "zram: recompression cleanups and tweaks" (Sergey Senozhatsky) A somewhat random mix of fixups, recompression cleanups and improvements in the zram code - "mm/damon: support multiple goal-based quota tuning algorithms" (SeongJae Park) Extend DAMOS quotas goal auto-tuning to support multiple tuning algorithms that users can select - "mm: thp: reduce unnecessary start_stop_khugepaged()" (Breno Leitao) Fix the khugpaged sysfs handling so we no longer spam the logs with reams of junk when starting/stopping khugepaged - "mm: improve map count checks" (Lorenzo Stoakes) Provide some cleanups and slight fixes in the mremap, mmap and vma code - "mm/damon: support addr_unit on default monitoring targets for modules" (SeongJae Park) Extend the use of DAMON core's addr_unit tunable - "mm: khugepaged cleanups and mTHP prerequisites" (Nico Pache) Cleanups to khugepaged and is a base for Nico's planned khugepaged mTHP support - "mm: memory hot(un)plug and SPARSEMEM cleanups" (David Hildenbrand) Code movement and cleanups in the memhotplug and sparsemem code - "mm: remove CONFIG_ARCH_ENABLE_MEMORY_HOTREMOVE and cleanup CONFIG_MIGRATION" (David Hildenbrand) Rationalize some memhotplug Kconfig support - "change young flag check functions to return bool" (Baolin Wang) Cleanups to change all young flag check functions to return bool - "mm/damon/sysfs: fix memory leak and NULL dereference issues" (Josh Law and SeongJae Park) Fix a few potential DAMON bugs - "mm/vma: convert vm_flags_t to vma_flags_t in vma code" (Lorenzo Stoakes) Convert a lot of the existing use of the legacy vm_flags_t data type to the new vma_flags_t type which replaces it. Mainly in the vma code. - "mm: expand mmap_prepare functionality and usage" (Lorenzo Stoakes) Expand the mmap_prepare functionality, which is intended to replace the deprecated f_op->mmap hook which has been the source of bugs and security issues for some time. Cleanups, documentation, extension of mmap_prepare into filesystem drivers - "mm/huge_memory: refactor zap_huge_pmd()" (Lorenzo Stoakes) Simplify and clean up zap_huge_pmd(). Additional cleanups around vm_normal_folio_pmd() and the softleaf functionality are performed. * tag 'mm-stable-2026-04-13-21-45' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits) mm: fix deferred split queue races during migration mm/khugepaged: fix issue with tracking lock mm/huge_memory: add and use has_deposited_pgtable() mm/huge_memory: add and use normal_or_softleaf_folio_pmd() mm: add softleaf_is_valid_pmd_entry(), pmd_to_softleaf_folio() mm/huge_memory: separate out the folio part of zap_huge_pmd() mm/huge_memory: use mm instead of tlb->mm mm/huge_memory: remove unnecessary sanity checks mm/huge_memory: deduplicate zap deposited table call mm/huge_memory: remove unnecessary VM_BUG_ON_PAGE() mm/huge_memory: add a common exit path to zap_huge_pmd() mm/huge_memory: handle buggy PMD entry in zap_huge_pmd() mm/huge_memory: have zap_huge_pmd return a boolean, add kdoc mm/huge: avoid big else branch in zap_huge_pmd() mm/huge_memory: simplify vma_is_specal_huge() mm: on remap assert that input range within the proposed VMA mm: add mmap_action_map_kernel_pages[_full]() uio: replace deprecated mmap hook with mmap_prepare in uio_info drivers: hv: vmbus: replace deprecated mmap hook with mmap_prepare mm: allow handling of stacked mmap_prepare hooks in more drivers ... 2026-04-15T17:54:24+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-04-15T17:54:24+00:00 urn:sha1:5bdb4078e1efba9650c03753616866192d680718 Pull sched_ext updates from Tejun Heo: - cgroup sub-scheduler groundwork Multiple BPF schedulers can be attached to cgroups and the dispatch path is made hierarchical. This involves substantial restructuring of the core dispatch, bypass, watchdog, and dump paths to be per-scheduler, along with new infrastructure for scheduler ownership enforcement, lifecycle management, and cgroup subtree iteration The enqueue path is not yet updated and will follow in a later cycle - scx_bpf_dsq_reenq() generalized to support any DSQ including remote local DSQs and user DSQs Built on top of this, SCX_ENQ_IMMED guarantees that tasks dispatched to local DSQs either run immediately or get reenqueued back through ops.enqueue(), giving schedulers tighter control over queueing latency Also useful for opportunistic CPU sharing across sub-schedulers - ops.dequeue() was only invoked when the core knew a task was in BPF data structures, missing scheduling property change events and skipping callbacks for non-local DSQ dispatches from ops.select_cpu() Fixed to guarantee exactly one ops.dequeue() call when a task leaves BPF scheduler custody - Kfunc access validation moved from runtime to BPF verifier time, removing runtime mask enforcement - Idle SMT sibling prioritization in the idle CPU selection path - Documentation, selftest, and tooling updates. Misc bug fixes and cleanups * tag 'sched_ext-for-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (134 commits) tools/sched_ext: Add explicit cast from void* in RESIZE_ARRAY() sched_ext: Make string params of __ENUM_set() const tools/sched_ext: Kick home CPU for stranded tasks in scx_qmap sched_ext: Drop spurious warning on kick during scheduler disable sched_ext: Warn on task-based SCX op recursion sched_ext: Rename scx_kf_allowed_on_arg_tasks() to scx_kf_arg_task_ok() sched_ext: Remove runtime kfunc mask enforcement sched_ext: Add verifier-time kfunc context filter sched_ext: Drop redundant rq-locked check from scx_bpf_task_cgroup() sched_ext: Decouple kfunc unlocked-context check from kf_mask sched_ext: Fix ops.cgroup_move() invocation kf_mask and rq tracking sched_ext: Track @p's rq lock across set_cpus_allowed_scx -> ops.set_cpumask sched_ext: Add select_cpu kfuncs to scx_kfunc_ids_unlocked sched_ext: Drop TRACING access to select_cpu kfuncs selftests/sched_ext: Fix wrong DSQ ID in peek_dsq error message sched_ext: Documentation: improve accuracy of task lifecycle pseudo-code selftests/sched_ext: Improve runner error reporting for invalid arguments sched_ext: Documentation: Fix scx_bpf_move_to_local kfunc name sched_ext: Documentation: Add ops.dequeue() to task lifecycle tools/sched_ext: Fix off-by-one in scx_sdt payload zeroing ... 2026-04-14T17:53:44+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-04-14T17:53:44+00:00 urn:sha1:f21f7b5162e9dbde6d3d5ce727d4ca2552d76ce9 Pull vdso updates from Thomas Gleixner: - Make the handling of compat functions consistent and more robust - Rework the underlying data store so that it is dynamically allocated, which allows the conversion of the last holdout SPARC64 to the generic VDSO implementation - Rework the SPARC64 VDSO to utilize the generic implementation - Mop up the left overs of the non-generic VDSO support in the core code - Expand the VDSO selftest and make them more robust - Allow time namespaces to be enabled independently of the generic VDSO support, which was not possible before due to SPARC64 not using it - Various cleanups and improvements in the related code * tag 'timers-vdso-2026-04-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits) timens: Use task_lock guard in timens_get*() timens: Use mutex guard in proc_timens_set_offset() timens: Simplify some calls to put_time_ns() timens: Add a __free() wrapper for put_time_ns() timens: Remove dependency on the vDSO vdso/timens: Move functions to new file selftests: vDSO: vdso_test_correctness: Add a test for time() selftests: vDSO: vdso_test_correctness: Use facilities from parse_vdso.c selftests: vDSO: vdso_test_correctness: Handle different tv_usec types selftests: vDSO: vdso_test_correctness: Drop SYS_getcpu fallbacks selftests: vDSO: vdso_test_gettimeofday: Remove nolibc checks Revert "selftests: vDSO: parse_vdso: Use UAPI headers instead of libc headers" random: vDSO: Remove ifdeffery random: vDSO: Trim vDSO includes vdso/datapage: Trim down unnecessary includes vdso/datapage: Remove inclusion of gettimeofday.h vdso/helpers: Explicitly include vdso/processor.h vdso/gettimeofday: Add explicit includes random: vDSO: Add explicit includes MIPS: vdso: Explicitly include asm/vdso/vdso.h ... 2026-04-14T16:18:40+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-04-14T16:18:40+00:00 urn:sha1:5d0d3623303775d750e122a2542d1a26c8573d38 Pull Kbuild/Kconfig updates from Nicolas Schier: "Kbuild: - reject unexpected values for LLVM= - uapi: remove usage of toolchain headers - switch from '-fms-extensions' to '-fms-anonymous-structs' when available (currently: clang >= 23.0.0) - reduce the number of compiler-generated suffixes for clang thin-lto build - reduce output spam ("GEN Makefile") when building out of tree - improve portability for testing headers - also test UAPI headers against C++ compilers - drop build ID architecture allow-list in vdso_install - only run checksyscalls when necessary - update the debug information notes in reproducible-builds.rst - expand inlining hints with -fdiagnostics-show-inlining-chain Kconfig: - forbid multiple entries with the same symbol in a choice - error out on duplicated kconfig inclusion" * tag 'kbuild-7.1-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux: (35 commits) kbuild: expand inlining hints with -fdiagnostics-show-inlining-chain kconfig: forbid multiple entries with the same symbol in a choice Documentation: kbuild: Update the debug information notes in reproducible-builds.rst checksyscalls: move instance functionality into generic code checksyscalls: only run when necessary checksyscalls: fail on all intermediate errors checksyscalls: move path to reference table to a variable kbuild: vdso_install: drop build ID architecture allow-list kbuild: vdso_install: gracefully handle images without build ID kbuild: vdso_install: hide readelf warnings kbuild: vdso_install: split out the readelf invocation kbuild: uapi: also test UAPI headers against C++ compilers kbuild: uapi: provide a C++ compatible dummy definition of NULL kbuild: uapi: handle UML in architecture-specific exclusion lists kbuild: uapi: move all include path flags together kbuild: uapi: move some compiler arguments out of the command definition check-uapi: use dummy libc includes check-uapi: honor ${CROSS_COMPILE} setting check-uapi: link into shared objects kbuild: reduce output spam when building out of tree ... 2026-04-13T16:54:20+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-04-13T16:54:20+00:00 urn:sha1:26ff969926a08eee069767ddbbbc301adbcd9676 Pull Rust updates from Miguel Ojeda: "Toolchain and infrastructure: - Bump the minimum Rust version to 1.85.0 (and 'bindgen' to 0.71.1). As proposed in LPC 2025 and the Maintainers Summit [1], we are going to follow Debian Stable's Rust versions as our minimum versions. Debian Trixie was released on 2025-08-09 with a Rust 1.85.0 and 'bindgen' 0.71.1 toolchain, which is a fair amount of time for e.g. kernel developers to upgrade. Other major distributions support a Rust version that is high enough as well, including: + Arch Linux. + Fedora Linux. + Gentoo Linux. + Nix. + openSUSE Slowroll and openSUSE Tumbleweed. + Ubuntu 25.10 and 26.04 LTS. In addition, 24.04 LTS using their versioned packages. The merged patch series comes with the associated cleanups and simplifications treewide that can be performed thanks to both bumps, as well as documentation updates. In addition, start using 'bindgen''s '--with-attribute-custom-enum' feature to set the 'cfi_encoding' attribute for the 'lru_status' enum used in Binder. Link: https://lwn.net/Articles/1050174/ [1] - Add experimental Kconfig option ('CONFIG_RUST_INLINE_HELPERS') that inlines C helpers into Rust. Essentially, it performs a step similar to LTO, but just for the helpers, i.e. very local and fast. It relies on 'llvm-link' and its '--internalize' flag, and requires a compatible LLVM between Clang and 'rustc' (i.e. same major version, 'CONFIG_RUSTC_CLANG_LLVM_COMPATIBLE'). It is only enabled for two architectures for now. The result is a measurable speedup in different workloads that different users have tested. For instance, for the null block driver, it amounts to a 2%. - Support global per-version flags. While we already have per-version flags in many places, we didn't have a place to set global ones that depend on the compiler version, i.e. in 'rust_common_flags', which sometimes is needed to e.g. tweak the lints set per version. Use that to allow the 'clippy::precedence' lint for Rust < 1.86.0, since it had a change in behavior. - Support overriding the crate name and apply it to Rust Binder, which wanted the module to be called 'rust_binder'. - Add the remaining '__rust_helper' annotations (started in the previous cycle). 'kernel' crate: - Introduce the 'const_assert!' macro: a more powerful version of 'static_assert!' that can refer to generics inside functions or implementation bodies, e.g.: fn f<const N: usize>() { const_assert!(N > 1); } fn g<T>() { const_assert!(size_of::<T>() > 0, "T cannot be ZST"); } In addition, reorganize our set of build-time assertion macros ('{build,const,static_assert}!') to live in the 'build_assert' module. Finally, improve the docs as well to clarify how these are different from one another and how to pick the right one to use, and their equivalence (if any) to the existing C ones for extra clarity. - 'sizes' module: add 'SizeConstants' trait. This gives us typed 'SZ_*' constants (avoiding casts) for use in device address spaces where the address width depends on the hardware (e.g. 32-bit MMIO windows, 64-bit GPU framebuffers, etc.), e.g.: let gpu_heap = 14 * u64::SZ_1M; let mmio_window = u32::SZ_16M; - 'clk' module: implement 'Send' and 'Sync' for 'Clk' and thus simplify the users in Tyr and PWM. - 'ptr' module: add 'const_align_up'. - 'str' module: improve the documentation of the 'c_str!' macro to explain that one should only use it for non-literal cases (for the other case we instead use C string literals, e.g. 'c"abc"'). - Disallow the use of 'CStr::{as_ptr,from_ptr}' and clean one such use in the 'task' module. - 'sync' module: finish the move of 'ARef' and 'AlwaysRefCounted' outside of the 'types' module, i.e. update the last remaining instances and finally remove the re-exports. - 'error' module: clarify that 'from_err_ptr' can return 'Ok(NULL)', including runtime-tested examples. The intention is to hopefully prevent UB that assumes the result of the function is not 'NULL' if successful. This originated from a case of UB I noticed in 'regulator' that created a 'NonNull' on it. Timekeeping: - Expand the example section in the 'HrTimer' documentation. - Mark the 'ClockSource' trait as unsafe to ensure valid values for 'ktime_get()'. - Add 'Delta::from_nanos()'. 'pin-init' crate: - Replace the 'Zeroable' impls for 'Option<NonZero*>' with impls of 'ZeroableOption' for 'NonZero*'. - Improve feature gate handling for unstable features. - Declutter the documentation of implementations of 'Zeroable' for tuples. - Replace uses of 'addr_of[_mut]!' with '&raw [mut]'. rust-analyzer: - Add type annotations to 'generate_rust_analyzer.py'. - Add support for scripts written in Rust ('generate_rust_target.rs', 'rustdoc_test_builder.rs', 'rustdoc_test_gen.rs'). - Refactor 'generate_rust_analyzer.py' to explicitly identify host and target crates, improve readability, and reduce duplication. And some other fixes, cleanups and improvements" * tag 'rust-7.1' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (79 commits) rust: sizes: add SizeConstants trait for device address space constants rust: kernel: update `file_with_nul` comment rust: kbuild: allow `clippy::precedence` for Rust < 1.86.0 rust: kbuild: support global per-version flags rust: declare cfi_encoding for lru_status docs: rust: general-information: use real example docs: rust: general-information: simplify Kconfig example docs: rust: quick-start: remove GDB/Binutils mention docs: rust: quick-start: remove Nix "unstable channel" note docs: rust: quick-start: remove Gentoo "testing" note docs: rust: quick-start: add Ubuntu 26.04 LTS and remove subsection title docs: rust: quick-start: update minimum Ubuntu version docs: rust: quick-start: update Ubuntu versioned packages docs: rust: quick-start: openSUSE provides `rust-src` package nowadays rust: kbuild: remove "dummy parameter" workaround for `bindgen` < 0.71.1 rust: kbuild: update `bindgen --rust-target` version and replace comment rust: rust_is_available: remove warning for `bindgen` < 0.69.5 && libclang >= 19.1 rust: rust_is_available: remove warning for `bindgen` 0.66.[01] rust: bump `bindgen` minimum supported version to 0.71.1 (Debian Trixie) rust: block: update `const_refs_to_static` MSRV TODO comment ... 2026-04-07T08:00:24+00:00 Miguel Ojeda ojeda@kernel.org 2026-04-05T23:52:57+00:00 urn:sha1:93553d9922b07555344095b5d9202a3f5b84541c Until the version bump of `bindgen`, we needed to pass a dummy parameter to avoid failing the `--version` call. Thus remove it. Reviewed-by: Tamir Duberstein <tamird@kernel.org> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://patch.msgid.link/20260405235309.418950-22-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org> 2026-04-07T08:00:23+00:00 Miguel Ojeda ojeda@kernel.org 2026-04-05T23:52:46+00:00 urn:sha1:4ab22c543f18cfbcc2f8ae691dc5ec5cc0ac35fb With the Rust version bump in place, the `RUSTC_HAS_COERCE_POINTEE` Kconfig (automatic) option is always true. Thus remove the option and simplify the code. In particular, this includes removing our use of the predecessor unstable features we used with Rust < 1.84.0 (`coerce_unsized`, `dispatch_from_dyn` and `unsize`). Reviewed-by: Tamir Duberstein <tamird@kernel.org> Acked-by: Danilo Krummrich <dakr@kernel.org> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://patch.msgid.link/20260405235309.418950-11-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org> 2026-04-07T08:00:23+00:00 Miguel Ojeda ojeda@kernel.org 2026-04-05T23:52:45+00:00 urn:sha1:9b398d0565438e9929afbfbb8a1cd1f3242067ac With the Rust version bump in place, the `RUSTC_HAS_SLICE_AS_FLATTENED` Kconfig (automatic) option is always true. Thus remove the option and simplify the code. In particular, this includes removing the `slice` module which contained the temporary slice helpers, i.e. the `AsFlattened` extension trait and its `impl`s. Reviewed-by: Tamir Duberstein <tamird@kernel.org> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://patch.msgid.link/20260405235309.418950-10-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org> 2026-04-07T08:00:23+00:00 Miguel Ojeda ojeda@kernel.org 2026-04-05T23:52:44+00:00 urn:sha1:b28711ac98e8b43bfbf5c918022018a54dcedd45 With the Rust version bump in place, several Kconfig conditions based on `RUSTC_VERSION` are always true. Thus simplify them. The minimum supported major LLVM version by our new Rust minimum version is now LLVM 18, instead of LLVM 16. However, there are no possible cleanups for `RUSTC_LLVM_VERSION`. Reviewed-by: Tamir Duberstein <tamird@kernel.org> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://patch.msgid.link/20260405235309.418950-9-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org> 2026-04-05T20:53:33+00:00 David Hildenbrand (Arm) david@kernel.org 2026-03-19T08:19:41+00:00 urn:sha1:6ebf98d71f9b509e833e0af00795ad3723d2f410 CONFIG_MEMORY_HOTREMOVE, CONFIG_COMPACTION and CONFIG_CMA all select CONFIG_MIGRATION, because they require it to work (users). Only CONFIG_NUMA_BALANCING and CONFIG_BALLOON_MIGRATION depend on CONFIG_MIGRATION. CONFIG_BALLOON_MIGRATION is not an actual user, but an implementation of migration support, so the dependency is correct (CONFIG_BALLOON_MIGRATION does not make any sense without CONFIG_MIGRATION). However, kconfig-language.rst clearly states "In general use select only for non-visible symbols". So far CONFIG_MIGRATION is user-visible ... and the dependencies rather confusing. The whole reason why CONFIG_MIGRATION is user-visible is because of CONFIG_NUMA: some users might want CONFIG_NUMA but not page migration support. Let's clean all that up by introducing a dedicated CONFIG_NUMA_MIGRATION config option for that purpose only. Make CONFIG_NUMA_BALANCING that so far depended on CONFIG_NUMA && CONFIG_MIGRATION to depend on CONFIG_MIGRATION instead. CONFIG_NUMA_MIGRATION will depend on CONFIG_NUMA && CONFIG_MMU. CONFIG_NUMA_MIGRATION is user-visible and will default to "y". We use that default so new configs will automatically enable it, just like it was the case with CONFIG_MIGRATION. The downside is that some configs that used to have CONFIG_MIGRATION=n might get it re-enabled by CONFIG_NUMA_MIGRATION=y, which shouldn't be a problem. CONFIG_MIGRATION is now a non-visible config option. Any code that select CONFIG_MIGRATION (as before) must depend directly or indirectly on CONFIG_MMU. CONFIG_NUMA_MIGRATION is responsible for any NUMA migration code, which is mempolicy migration code, memory-tiering code, and move_pages() code in migrate.c. CONFIG_NUMA_BALANCING uses its functionality. Note that this implies that with CONFIG_NUMA_MIGRATION=n, move_pages() will not be available even though CONFIG_MIGRATION=y, which is an expected change. In migrate.c, we can remove the CONFIG_NUMA check as both CONFIG_NUMA_MIGRATION and CONFIG_NUMA_BALANCING depend on it. With this change, CONFIG_MIGRATION is an internal config, all users of migration selects CONFIG_MIGRATION, and only CONFIG_BALLOON_MIGRATION depends on it. Link: https://lkml.kernel.org/r/20260319-config_migration-v1-2-42270124966f@kernel.org Signed-off-by: David Hildenbrand (Arm) <david@kernel.org> Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org> Acked-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Alexandre Ghiti <alex@ghiti.fr> Cc: Alistair Popple <apopple@nvidia.com> Cc: "Borislav Petkov (AMD)" <bp@alien8.de> Cc: Byungchul Park <byungchul@sk.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Gregory Price <gourry@gourry.net> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: "Huang, Ying" <ying.huang@linux.alibaba.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Joshua Hahn <joshua.hahnjy@gmail.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Madhavan Srinivasan <maddy@linux.ibm.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Rakie Kim <rakie.kim@sk.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>