Linux kernel stable tree https://git.rulkc.org/pub/scm/linux/kernel/git/stable/linux-stable.git/atom?h=master 2026-08-21T01:17:08+00:00 2026-08-21T01:17:08+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-08-21T01:17:08+00:00 urn:sha1:ed3b875bea55a3ec4837113356df2ead11115af9 Pull MM updates from Andrew Morton: - "mm: drop "sub" prefix from various places" (Dev Jain) page->folio conversion and a naming cleanup - "mm/kasan: remove redundant initialization for kasan_flag_write_only" (Igor Putko) KASAN cleanup work - "mm/filemap: reduce unnecessary xarray lookups" (Chi Zhiling) Small speedup in the pagecaache read code - "mm/percpu: Fix possible NOFS/NOIO reclaim recursion" (Kaitao Cheng) Improve the vmalloc code - mainly the avoidance of GFP_KERNEL allocations when the caller asked for GFP_NOFS or GFP_NOIO - "mm/kmemleak: avoid soft lockup when scanning task stacks" (Breno Leitao) Avoid a soft lockup watchdog trigger from the kmemleak scanning code in extreme situations - "mm/page_owner: misc cleanups" (Ye Liu) Cleanups to the page_owner code. For some reason lots of people have been working on the page_owner code this cycle. - "mm: convert to walk_page_range_vma() to eliminate find_vma()" (Kefeng Wang) Simplify and accelerate the page walking library function - "mm/migrate: preparatory cleanups for batch copy and offload" (Shivank Garg) Cleanups in the migration code - "mm/page_owner: add per-fd filter infrastructure for print_mode and NUMA filtering" (Zhen Ni) Per-fd filtering to page_owner in order to reduce the sometimes vast amount of output it can produce - "mm: Refactor bootmem gigantic hugepage allocation" (Muchun Song) Fixes and preparatory cleanups around bootmem HugeTLB handling, sparse initialization ordering, and related vmemmap setup - "mm/zsmalloc: reduce lock contention in zs_free()" (Wenchao Hao) Reduce lock contention in zs_free(), which dominates the unmap path under memory pressure on Android (LMK kills) and on x86 servers running zswap-heavy workloads. Up to 1.83x improvement in microbenchmarking. - "move alloc_tag.c file under mm/" (Suren Baghdasaryan) - "samples/damon: handle damon_{start,stop}() failures" (SJ Park) Fix improper handling of damon_start(), damon_stop(), and damon_call() failures across DAMON sample modules to prevent potential memory leaks, operation disruptions and use-after-free bugs - "mm/damon/sysfs: kobject_del() directories that users can create/remove" (SJ Park) Fix delayed sysfs directory removal under DEBUG_KOBJECT_RELEASE causeing creation failures due to duplicate directory names by adding missing kobject_del() calls before creating new directories - "mm: cleanup clear_not_present_full_ptes()" (David Hildenbrand) Clean up the core pte handling code - "selftests/damon: misc fixes for test bugs" (Kunwu Chan) Fix several bugs in the DAMON selftests - "selftests/damon: fix memcg_path staging handling" (Cheng Nie) Fix a bug in _damon_sysfs.py for damos_filter memcg_path setup, and add a test case for it in sysfs.py. - "selftests/damon: test kdamond refresh_ms" (Ruslan Valiyev) Selftest coverage for DAMON's refresh_ms sysfs feature by updating the test control module and verifying that scheme stats update automatically without manual intervention - "mm/damon: five misc fixups" (Akinobu Mita) Miscellaneous DAMON fixups. - "mm/damon/core: detect internal variation above max_nr_regions/2" (Jiayuan Chen) Fix DAMON's region splitting behavior when region counts exceed half the maximum budget by dynamically scaling down the split fraction as the limit approaches, preventing large regions from staying un-split, and add corresponding KUnit test coverage - "mm: preparatory patches for PMD level swap entries" (Usama Arif) Refactor and clean up PMD softleaf helpers, call sites, and architecture flags to lay the groundwork for a follow-up series that introduces PMD page table swap entries - "mm/damon: update, optimize, and clean up doc, tests, and code" (SJ Park) Update DAMON design and ABI documentation, expands unit and selftest coverage, optimize damon_commit_target_regions(), and clean up recently added sysfs interface code for better readability - "mm/vmpressure: reduce CPU, memory and code overhead on cgroup v2" (Usama Arif) Optimize vmpressure() by skipping unnecessary work on cgroup v2 for userspace event notifications and refactor v1-only eventfd handling into mm/memcontrol-v1.c to reduce memory overhead and code complexity - "selftests/mm: refactor pkey helpers and fix mmap error handling" (Hongfu Li) Refactor pkeys shared tracing and assertion helpers into a common file, unify protection key selftests to use consistent diagnostic logging and assertions, and enforce standardized MAP_FAILED return checks for mmap() calls across the tests - "mm/damon: optimize out nr_accesses_bp" (SJ Park) Replace the error-prone, continuously updated nr_accesses_bp field in damon_region with an on-demand moving sum function, reducing structure memory overhead and avoiding state corruption bugs - "Open HugeTLB allocation routine for more generic use" (Ackerley Tng) Decouple HugeTLB folio allocation from VMA dependencies by introducing hugetlb_alloc_folio(), enabling subsystems like guest_memfd to allocate HugeTLB folios without standard VMA reservations or pseudo-VMAs - "mm/damon: provide pseudo moving sum probe_hits" (SJ Park) Integrate DAMON's probe_hits attribute counter into the pseudo moving sum infrastructure, enabling real-time, online monitoring without waiting for full aggregation intervals - "mm: Some cleanups for page allocator APIs" (Brendan Jackman) Simplify and refactor the page allocator entry points and flags by unifying allocation paths, adding internal alloc_flags arguments, and eliminating redundant __ prefixed alloc_pages variants. - "Fix incorrect access of hugetlb pte entries" (Dev Jain) Enforce the consistent use of huge_ptep_get() instead of ptep_get() for HugeTLB entries and fixes an unaligned address issue in arm64's huge_ptep_get() implementation - "mm/damon: validate all parameters in the core" (SJ Park) Consolidate parameter validation into the DAMON core specifically within damon_start() and damon_commit_ctx() to centralize error checking, eliminate caller-side redundant checks and to improve maintenance efficiency - "tools/mm/page_owner_sort: fix filtering and cleanup issues" (Yichong Chen) Rename is_need() to filter_record() for clearer return semantics, fix per-record allocation memory leaks and bound output copies in search_pattern() to address an existing buffer issue - "memcg: bail out reclaim when memcg is dying" (Jiayuan Chen) Mitigate a system-wide stall which occurs when a cgroup is removed while one of its memory control files is doing synchronous reclaim - "mm/memory-failure: add panic option for unrecoverable pages" (Breno Leitao) Introduce an opt-in vm.panic_on_unrecoverable_memory_failure sysctl that immediately panics the kernel on unrecoverable memory errors in kernel-owned pages to preserve error context and prevent delayed, silent data corruption - "mm/damon: refactor damon_{start,stop,commit}() for simple error handling" (SJ Park) Refactor the DAMON core API functions to guarantee that all contexts are fully stopped when damon_start(), damon_stop(), or damon_commit() fail, eliminating the need for complex and error-prone caller-side cleanup code - "Keep tail page private zero at free and folio split" (Zi Yan) Add checks to ensure tail_page->private is zero when freeing compound or high-order pages and when promoting tail pages during large folio splits. By validating these fields at free and split time, it allows the removal of redundant private field clearing inside prep_compound_tail() - "mm: drop redundant lru_add_drain in anon folio reuse paths" (Barry Song) Eliminate redundant lru_add_drain() calls in wp_can_reuse_anon_folio() and do_swap_page() to reduce LRU lock contention and system overhead By validating folio refcounts against the LRU cache before draining and removing unnecessary drains in the swap path, it achieves up to a 30.5% reduction in drain calls during heavy swap workloads - "mm: clean up folio LRU and swap declarations" (Jianyue Wu) Reorganize folio LRU and swap code by relocating page-cluster state to mm/swap_state.c, renaming mm/swap.c to mm/folio.c, and moving MM-internal reclaim declarations into mm/internal.h. - "userfaultfd: working set tracking for VM guest memory" (Kiryl Shutsemau) Add userfaultfd support for tracking the working set of VM guest memory, so a VMM can identify hot pages and reclaim cold ones to tiered or remote storage - "mm: remove CONFIG_HAVE_BOOTMEM_INFO_NODE (Part 2)" (David Hildenbrand) Remove the remaining pieces of CONFIG_HAVE_BOOTMEM_INFO_NODE, performing some smaller cleanups around freeing of reserved vmemmap pages on the way. - "mm/damon: update probe hits for runtime parameter commits" (SJ Park) Ensure that DAMON's probe_hits attribute counter is properly updated when monitoring intervals are changed at runtime, matching the behavior of nr_accesses. To achieve this, it refactors and renames existing helper functions for shared use, applies the updates to probe_hits, and handles edge cases in damon_probe_hits_mvsum() to maintain measurement accuracy. - "KSM: performance optimizations for rmap_walk_ksm" (xu xin) Resolve a severe KSM reverse-mapping performance bottleneck where thousands of split VMAs sharing a single anon_vma cause extended lock contention. By adding an interval-filtering check during the rmap walk, it reduces worst-case anon_vma lock hold times from over 500ms down to under 2ms, preventing application freezes and latency spikes under memory pressure. - "mm: split a couple of headers from internal.h" (Mike Rapoport) Split declarations related to mm_init, memblock, vmalloc and sparse into new headers - "KSM: use linear_page_index in collect_procs_ksm()" (xu xin) Apply the interval tree optimization from rmap_walk_ksm() to collect_procs_ksm() to avoid iterating over non-matching VMAs during KSM memory error handling. It hoists loop-invariant address initialization and restricts the anon_vma_interval_tree_foreach walk to a targeted page offset range, reducing redundant checks and improving lookup efficiency. - "selftests/mm: avoid false failures in hugetlb and KSM tests" (Sayali Patil) Fix issues in the hugetlb and KSM MM selftest categories that can report failures when the prerequisites for the tests are not satisfied - "mm/damon: introduce data attributes only monitoring" (SJ Park) Introduce attribute-weighted region management in DAMON, allowing users to prioritize specific data attributes (such as page sizes or cgroups) over or instead of access monitoring. By assigning weights to attribute probes, DAMON can completely disable access tracking and adjust monitoring regions based on weighted probe-hit counters to optimize monitoring quality for attribute-focused workloads. - "mm/hmm: Add mmap lock-drop support for userfaultfd-backed mappings" (Stanislav Kinsburskii) Extend hmm_range_fault() to support userfaultfd-backed regions by allowing the mmap lock to be dropped during fault handling via a new hmm_range_fault_locked() helper. By accepting a locked pointer and signaling retry status when lock release occurs, it enables page fault resolution in userfaultfd regions while preserving backward compatibility for existing callers. - "mm: make VMA page offset handling more consistent" (Lorenzo Stoakes) Clean up and standardize how vma->vm_pgoff is accessed and manipulated across file-backed and anonymous mappings in the kernel It introduces dedicated helper functions such as vma_start_pgoff(), vma_end_pgoff(), vma_set_pgoff() and linear_page_delta() while renaming rmap interval tree helpers to better reflect their functionality. These changes establish a cleaner foundation for future work that will unify virtual page offset indexing for all anonymous and CoW'd folios. - "mm: handle device-private PMDs in walk callbacks" (Usama Arif) Address kernel panics and state corruption caused by MM walk callbacks reaching non-present device-private PMD swap entries created during HMM migrations It ensures that functions which acquire pmd_trans_huge_lock() properly recognize device-private PMDs instead of assuming a present THP or a standard migration entry. - "mm/rmap: Refactor try_to_unmap_one" (Dev Jain) Refactor try_to_unmap_one by modularizing Hugetlb, anonymous-lazyfree, and anonymous-swapbacked logic into dedicated functions, laying the structural groundwork for batched anonymous large folio unmapping. - "Docs/ABI/damon: sysfs ABI document fixes and additions" (Song Hu) Fix typos and fills in missing entries in the DAMON sysfs ABI document - "dax/kmem: atomic whole-device hotplug via sysfs" (Gregory Price) Introduce an atomic sysfs state attribute and supporting DAX/MM infrastructure to prevent userland races when offlining and removing entire memory regions By adding an unplugged state alongside standard online modes, it enables whole-device atomic hotplug control while preserving backward compatibility. - "mm: convert more vm_flags_t users to vma_flags_t" (Lorenzo Stoakes) Continue transitioning the kernel from the deprecated vm_flags_t type to vma_flags_t across core memory management infrastructure. It replaces legacy type usage in core functions such as do_mmap(), unmapped area allocation, mm->def_vma_flags, and VMA operations like mlock, mprotect, and mremap. - "Two small patches to clean up mm/mm_slot.h" (xu xin) Refactor mm_slot.h by introducing mm_slot_remove() to unify duplicate slot deletion sequences in khugepaged and KSM. It also adds code documentation explaining why mm_slot_lookup and mm_slot_insert must remain as preprocessor macros rather than static inline functions. - "mm/damon/core: hide core-private struct fields" (SJ Park) Clean up DAMON core structures by consistently marking internal-only fields with private: comment tags to prevent improper direct access from outer layers. It enforces encapsulation across core structures including damon_region, damon_target, and damon_ctx and updates DAMON_SYSFS to interact through approved access APIs instead of exposing raw struct members. - "mm/damon: unurgent fixes for infinite loop, NULL de-ref and races" (SJ Park) Address potential infinite loops, NULL dereferences, and race conditions identified in DAMON It fixes an infinite loop triggered by extreme user configurations, a NULL pointer dereference within unit tests and minor monitoring accuracy degradation caused by subtle runtime races. - "mm/page_alloc: fixes for free_pages_nolock() on RT/UP" (Brendan Jackman) Fix an NMI safety flaw in __free_frozen_pages() where freeing pages on non-SMP or PREEMPT_RT kernels can bypass can_spin_trylock() checks via non-PCP or isolated migration paths. It also resolves potential kernel crashes and privilege escalation risks triggered when BPF tracing runs in NMI context alongside memory hotplug or large allocation frees. - "mm/page_alloc: couple of followups for recent cleanups" (Brendan Jackman) Clean up and update page allocator nomenclature, documentation, and debug assertions. It aligns internal FPI_ flags with the public "nolock" naming convention, removes outdated internal implementation details from high-level page allocator comments, and eliminates obsolete VM_BUG_ON() assertions in allocation paths. - "mm/mseal: further cleanups" (Lorenzo Stoakes) Refactor and simplify the mseal implementation by clarifying API boundaries and removing unnecessary code complexity. It replaces generic do_mseal() usage outside the syscall with a dedicated mseal_mmap_page_zero() helper for MMAP_PAGE_ZERO, eliminates mm_struct parameters to enforce that sealing applies only to current->mm, and streamlines overall logic and comments with no functional changes intended. - "mm/vmscan: fix swappiness=max and clean up per-node proactive reclaim" (Ridong Chen) Resolve reclaim behavior bugs and clean up function parameters across memory reclaim paths It fixes swappiness=max in both standard reclaim and MGLRU so unswappable anonymous memory no longer falls back to evicting page cache, ensures reclaim_store() returns accurate error codes instead of collapsing all failures into -EAGAIN, and removes the obsolete gfp_mask parameter from __node_reclaim(). - "mm: mincore: misc cleanups" (Kefeng Wang) Clean up and simplifies the mincore code. Most importantly, it removes the historical special behavior that always reports VM_PFNMAP pages as non-resident. - "mm/huge_memory: drop dead split helper variants" (Kiryl Shutsemau) Two trivial cleanups in the folio split API - "mm/damon: fix uninitialized DAMOS field and kunit exec expectation bugs" (SJ Park) Resolve minor operational and testing bugs in DAMON identified by Sashiko. It initializes the damos->last_applied field to prevent occasional efficiency degradation and fixes invalid memory accesses in DAMON KUnit tests during test failure handling. - "cleanup for stable_page_flags()" (Jinjiang Tu) Clean up and refactor stable_page_flags() used by /proc/kpageflags without altering functionality. It uses BIT_ULL() to prevent shift-overflow warnings on 64-bit flag bits, converts folio-specific flag checks to standard folio_test_*() helpers, and removes redundant CONFIG_PAGE_IDLE_FLAG handling. - "Batch unmap of uffd-wp file folios" (Dev Jain) Extend batched folio unmapping support to file folios within userfaultfd write-protect (uffd-wp) VMAs by adding batching capabilities to pte_install_uffd_wp_if_needed(). This removes special-case restrictions on uffd-wp VMAs in try_to_unmap_one(), significantly simplifying the function's control flow and complexity. - "mm/early_ioremap: clarify and clean up early_ioremap_reset()" (Sang-Heon Jeon) Clarify and clean up the architecture-specific usage of __late_set_fixmap() and __late_clear_fixmap() after early_ioremap_reset() It adds explicit documentation regarding when early_ioremap_reset() must be called and removes redundant macro definitions and reset calls in the RISC-V and ARM64 architectures. - "mm: fix reclaim storms in defrag_mode" (Johannes Weiner) Address severe performance regressions, swap storms, and spurious OOMs caused by vm.defrag_mode=1 under high memory pressure in Meta production It updates the page allocator slowpath so non-movable allocation requests actively trigger direct reclaim and direct compaction at pageblock_order scale, allowing them to claim whole pageblocks rather than spinning unproductively. - "zram: lockmap tweaks" (Sebastian Siewior) Optimize and fix lockdep tracking for zram devices by consolidating per-entry lockmaps and isolate lock classes across multiple instances This reduces memory overhead by replacing per-entry lockdep_map instances with a single map per struct zram, and assigns a dynamic lock_class_key to each instance to prevent false deadlock reports when different zram devices are backed by distinct filesystems. * tag 'mm-stable-2026-08-18-18-39' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (501 commits) selftests/mm: thuge-gen: fix test_shmget() for PAGE_SIZE check selftests/mm: unpoison pages in memory-failure teardown mm/shmem: downgrade final i_blocks check in shmem_evict_inode() to pr_warn() mm/khugepaged: replace mutex_lock/mutex_unlock usage with guard macro mm/zsmalloc: fix release order of locks in zs_page_migrate() Documentation: zram: remove sections numbering ksm: stop iterating VMAs when ksm_test_exit returns true mm: fold userfaultfd_rwp() to false without CONFIG_ARCH_HAS_PTE_PROTNONE mm/migrate: report RCU-tasks quiescent states in migrate_pages_batch() zram: use a custom key for each zram object zram: move lockmap to be per-zram instead per table selftests/mm: fix gup_longterm EINVAL error message mm: page_alloc: fix non-movable reclaim storm in defrag_mode mm: page_alloc: move capture_control to the page allocator mm: compaction: support non-movable compaction for pageblock requests mm: page_alloc: __GFP_FS lockdep annotation for direct compaction hugetlb: evaluate subpool free state while locked mm/damon: remove trailing semicolons after function definitions mm/damon/ops-common: prevent migration fallback to non-target nodes mm/damon: update outdated comment about DAMOS filter handling ... 2026-08-20T21:46:50+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-08-20T21:46:50+00:00 urn:sha1:caf325ab81be0bc22adf75248ecd22f52f01ad21 Pull LoongArch updates from Huacai Chen: - Add DIRECT_MAP_PHYSMEM_END definition - Expand module virtual address space to 2GB - Use current_stack_pointer in current_pt_regs() - BPF JIT enhancements such as kptr_xchg and timed may_goto - Some bug fixes and other small changes * tag 'loongarch-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson: selftests/bpf: Enable kptr_xchg_inline test on LoongArch LoongArch: BPF: Add arch_bpf_stack_walk() implementation LoongArch: BPF: Add timed may_goto implementation LoongArch: BPF: Resolve per-CPU addrs for internal-only MOV LoongArch: BPF: Advertise JIT support for kptr xchg inline LoongArch: BPF: Align value-returning atomics with LKMM LoongArch: BPF: Split unconditional branch JA paths statically LoongArch: BPF: Remove dead move_imm() call in BPF_NEG path LoongArch: BPF: Remove redundant zext jumping in move_imm() LoongArch: BPF: Implement branchless conditional move for TCC LoongArch: BPF: Refactor jump offset calculation in tail call LoongArch: BPF: Move arena register slot below TCC context LoongArch: BPF: Optimize redundant TCC loads in epilogue LoongArch: Use current_stack_pointer in current_pt_regs() LoongArch: Use generic cmp_int() instead of custom cmp_3way() LoongArch: Expand module virtual address space to 2GB LoongArch: Add DIRECT_MAP_PHYSMEM_END definition LoongArch: Fix acpi_package_ids[] array overflow 2026-08-18T22:00:56+00:00 Linus Torvalds torvalds@linux-foundation.org 2026-08-18T22:00:56+00:00 urn:sha1:3424d8c18a7da1010d03391a22e728b857d0d5c5 Pull generic entry code updates from Thomas Gleixner: - Make syscall user dispatching configurable Not all architectures can makes use of syscall user dispatching. Allow them to disable the feature completely. - Consolidate stack randomization for the generic entry code and the architectures using it. Stack randomization on syscall entry was sprinkled throughout the architecture specific low level entry code and in some cases at the wrong points, e.g. before establishing state, which violates the non-instrumentable constraints of that code. Clean this up by integrating stack randomization into the generic entry code helpers so that it is invoked at the earliest possible point right after establishing state and converting all generic entry code using architecture over. - Clean up the syscall number handling in the generic entry code. It works correctly for architectures which have a separate return value storage in pt_regs, but fails to distinguish the case where user space handed in -1 as syscall number from the case where the entry code rejects it by returning -1 to the callers. Aside of that the return value functionality of those interfaces is not really intuitive. Fix this by separating the decision to reject a syscall (user dispatch, ptrace, seccomp ...) from the potential modification of the syscall number through these mechanisms. This solves most of the problems for architectures which do not have a separate return value storage in pt_regs except for the case where a tracepoint has a BPF script or a probe attached which overwrite both the syscall number and the return value. But that's a problem which cannot be solved in the generic code, that only can be addressed by separating the storage model in the affected architectures. * tag 'core-entry-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits) entry, treewide: Make syscall_enter_from_user_mode[_work]() indicate syscall execution entry: Make return type of syscall_trace_enter() bool entry: Rework trace_syscall_enter() entry: Rework syscall_audit_enter() syscall_user_dispatch: Introduce ARCH_SUPPORTS_SYSCALL_USER_DISPATCH entry: Fix seccomp bypass after ptrace with TSYNC x86/entry: Simplify the syscall number logic x86/entry: Get rid of the sys_ni_syscall() indirection x86/entry: Make syscall functions static ptrace, treewide: Rename ptrace_report_syscall_entry() to ptrace_report_syscall_permit_entry() seccomp, treewide: Rename and convert __secure_computing() to return boolean entry: Use syscall number instead of rereading it entry: Remove syscall_enter_from_user_mode() x86/syscall: Use [syscall_]enter_from_user_mode_randomize_stack() s390/syscall: Use enter_from_user_mode_randomize_stack() riscv/syscall: Use syscall_enter_from_user_mode_randomize_stack() powerpc/syscall: Use syscall_enter_from_user_mode_randomize_stack() loongarch/syscall: Use syscall_enter_from_user_mode_randomize_stack() entry: Provide [syscall_]enter_from_user_mode_randomize_stack() randomize_kstack: Provide add_random_kstack_offset_irqsoff() ... 2026-08-17T14:07:40+00:00 George Guo guodongtai@kylinos.cn 2026-08-17T14:07:40+00:00 urn:sha1:1db6d003e93d033fca25bcfbef73e2780a7e46d7 Add support for the internal-only BPF_MOV instruction that resolves the absolute addresses of the per-CPU data from their per-CPU offsets. This instruction is used only for internal inlining optimizations between the BPF verifier and the JITs (e.g. inlining bpf_get_smp_processor_id() and per-CPU map lookups). LoongArch keeps the per-CPU offset of the current CPU in $r21 register (a.k.a. __my_cpu_offset), so resolving a per-CPU address only requires adding $r21 to the source register holding the per-CPU offset. Advertise the capability via bpf_jit_supports_percpu_insn(). Acked-by: Tiezhu Yang <yangtiezhu@loongson.cn> Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: George Guo <guodongtai@kylinos.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> 2026-08-17T14:07:39+00:00 Chenguang Zhao zhaochenguang@kylinos.cn 2026-08-17T14:07:39+00:00 urn:sha1:576412d98297bd0b3b837c20643ab2e1ba54766f Per the Linux Kernel Memory Model, value-returning atomic RMW operations must provide sequentially consistent ordering (a full memory barrier). On LoongArch, plain AMO instructions and bare ll/sc loops do not satisfy this requirement by themselves. Update emit_atomic_rmw() to emit barrier-carrying instructions for all value-returning BPF atomics: - BPF_FETCH (ADD/AND/OR/XOR): use am*_db.{b,h,w,d} - BPF_XCHG: use amswap_db.{b,h,w,d} - BPF_CMPXCHG: emit dbar 0x700 after the ll/sc loop, matching __WEAK_LLSC_MB in cmpxchg.h Add the corresponding instruction encodings and emit helpers to inst.h. Non-value-returning RMW ops (plain BPF_ADD, BPF_AND, etc.) are left as weakly ordered, consistent with LKMM. Acked-by: Hengqi Chen <hengqi.chen@gmail.com> Acked-by: Tiezhu Yang <yangtiezhu@loongson.cn> Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Chenguang Zhao <zhaochenguang@kylinos.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> 2026-08-17T14:07:23+00:00 Tiezhu Yang yangtiezhu@loongson.cn 2026-08-17T14:07:23+00:00 urn:sha1:434308885db42e7cc929e8466ac9eb7f69a999e0 The current implementation handles combined bpf2bpf and tail calls by checking at runtime whether REG_TCC holds a scalar count or a pointer address via a conditional jump. This adds branch prediction overhead in the hot path of tail call execution. To implement branchless conditional move, use an unsigned comparison (sltui) combined with mask instructions (maskeqz/masknez) to achieve branchless classification and blending of incoming scalar counts and kernel pointers in REG_TCC. This optimization refactors the inner logic of the helper function, unifies the offset decrement at the function entry, and removes all runtime branching from the prologue hot path completely. Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> 2026-08-17T14:07:14+00:00 Tiezhu Yang yangtiezhu@loongson.cn 2026-08-17T14:07:14+00:00 urn:sha1:29479b14315de24616cc1fad86cbd392c36f557a The current implementation of current_pt_regs() relies on the compiler __builtin_frame_address(0). This introduces an unnecessary dependency on the frame pointer register, which forces the compiler to generate redundant prologue and epilogue code, create a larger stack frame, and perform redundant memory operations to preserve the frame pointer even in functions where it is otherwise unnecessary. Optimize this by switching to current_stack_pointer, which explicitly maps to the hardware stack pointer register. This allows the compiler to compute the stack alignment directly from the natively maintained "$sp" register, completely eliminating the overhead of preserving and restoring the frame pointer on the stack memory. As a prominent example, this optimization improves the hot-path function copy_thread(). A disassembly comparison of copy_thread() illustrates the elimination of the frame pointer, the reduction of stack frame size from 48 bytes down to 32 bytes, and a more compact epilogue path: Before: 00000000000004f0 <copy_thread>: 4f0: 02ff4063 addi.d $sp, $sp, -48 4f4: 29c08076 st.d $fp, $sp, 32 4f8: 29c06077 st.d $s0, $sp, 24 4fc: 29c0a061 st.d $ra, $sp, 40 500: 02c0c076 addi.d $fp, $sp, 48 ... 54c: 1400006e lu12i.w $t2, 3 ... 55c: 03bffdce ori $t2, $t2, 0xfff 560: 00153ace or $t2, $fp, $t2 564: 02fb05cd addi.d $t1, $t2, -319 ... 628: 28c0a061 ld.d $ra, $sp, 40 62c: 28c08076 ld.d $fp, $sp, 32 630: 28c06077 ld.d $s0, $sp, 24 634: 00150004 move $a0, $zero 638: 02c0c063 addi.d $sp, $sp, 48 63c: 4c000020 ret After: 00000000000004f0 <copy_thread>: 4f0: 02ff8063 addi.d $sp, $sp, -32 4f4: 29c04077 st.d $s0, $sp, 16 4f8: 29c06061 st.d $ra, $sp, 24 [ prologue st.d and addi.d for $fp are completely eliminated ] ... 544: 1400006e lu12i.w $t2, 3 ... 554: 03bffdce ori $t2, $t2, 0xfff 558: 0015386e or $t2, $sp, $t2 55c: 02fb05cd addi.d $t1, $t2, -319 ... 620: 28c06061 ld.d $ra, $sp, 24 624: 28c04077 ld.d $s0, $sp, 16 628: 00150004 move $a0, $zero [ epilogue ld.d for $fp is eliminated; exit path is shortened ] 62c: 02c08063 addi.d $sp, $sp, 32 630: 4c000020 ret Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> 2026-08-17T14:07:14+00:00 Tiezhu Yang yangtiezhu@loongson.cn 2026-08-17T14:07:14+00:00 urn:sha1:18210a104bb97e28c26dc31fd9fc7b5c381fec62 The current 256MB module virtual address space is easily exhausted when loading massive graphics drivers such as amdgpu along with the large unstripped symbol tables, resulting in allocation failures of "execmem: unable to allocate memory". Thus, expand the module virtual address space to 2GB while keeping the current normal code model '-mcmodel=normal', rather than using the medium code model '-mcmodel=medium'. This approach avoids the extra performance overhead and larger binary size of forcing every function call into a 2-instruction sequence of 'pcaddu18i + jirl'. Given that individual module code segments rarely exceed 128MB, most jumps remain fast direct calls by using the bl instruction. For the long-distance jumps exceeding the +/-128MB limit, apply_r_larch_b26() emits PLT entries, while signed_imm_check() guarantees the run-time safety by rejecting any out-of-bound instruction offsets. There is still a risk that the distance between .init.text and .text of the same module exceeds 128MB. So we divide the 2GB virtual space to be two sub-regions: the first 256MB is for module text, and the rest is for module data. Cc: stable@vger.kernel.org Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> 2026-08-17T14:07:05+00:00 Han Gao gaohan@iscas.ac.cn 2026-08-17T14:07:05+00:00 urn:sha1:2677f97a67fdbc62a82ce1faa67791f54451d36f get_free_mem_region() and mhp_get_pluggable_range() bound their search to DIRECT_MAP_PHYSMEM_END. LoongArch does not define it, so the fallback in include/linux/mm.h applies: under CONFIG_SPARSEMEM_VMEMMAP it is (1ULL << MAX_PHYSMEM_BITS) - 1, a compile-time constant that does not adapt to the CPU's physical address space bits (cpu_pabits, probed from CPUCFG1). The vmemmap window only covers physical space below 2^(cpu_pabits+1) (i.e. VMEMMAP_SIZE), so on CPUs with fewer physical address bits than MAX_PHYSMEM_BITS the fallback allows get_free_mem_region() to return a ZONE_DEVICE region outside the vmemmap window; vmemmap_populate() then wraps the memmap range around and maps it into low memory, silently corrupting the page tables. The same search also picked the top-of- address-space region that crashed memmap_init_zone_device() with amdkfd on Loongson-3C6000 in 6.16 [1]; the commit 2969b42c8f99 ("LoongArch/mm: align vmemmap to maximal folio size") keeps that region in bounds on current Loongson-3C6000 configs, but CPUs with smaller cpu_pabits (e.g. the Loongson-2K series) are still affected. Define DIRECT_MAP_PHYSMEM_END as the vmemmap-covered physical range, (1ULL << (cpu_pabits + 1)) - 1, capped at (1ULL << MAX_PHYSMEM_BITS) - 1 under CONFIG_SPARSEMEM, similar to the commit f3336b48cf9d ("riscv: mm: Define DIRECT_MAP_PHYSMEM_END"). [1] https://lore.kernel.org/amd-gfx/20250814032153.227285-1-jeffbai@aosc.io/ Cc: stable@vger.kernel.org # v6.13+ Signed-off-by: Han Gao <gaohan@iscas.ac.cn> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn> 2026-08-05T02:18:36+00:00 Kiryl Shutsemau (Meta) kas@kernel.org 2026-07-08T11:14:02+00:00 urn:sha1:c6f11553c067d7d9ed2dcffe1e01780441d4e6e2 Patch series "userfaultfd: working set tracking for VM guest memory", v10. This series adds userfaultfd support for tracking the working set of VM guest memory, so a VMM can identify hot pages and reclaim cold ones to tiered or remote storage. This patch (of 15): pte_protnone() and pmd_protnone() detect present-but-inaccessible page table entries. This capability is useful beyond NUMA balancing -- for example, userfaultfd working set tracking uses protnone PTEs to track page access without unmapping pages. Introduce CONFIG_ARCH_HAS_PTE_PROTNONE to decouple the protnone PTE infrastructure from CONFIG_NUMA_BALANCING. The six architectures that support protnone PTEs (x86_64, arm64, powerpc, s390, riscv, loongarch) now select this option, and CONFIG_NUMA_BALANCING depends on it. No functional change -- the same set of architectures continues to have working protnone support, but the infrastructure is now available independently of NUMA balancing. Link: https://lore.kernel.org/20260708111417.173443-1-kirill@shutemov.name Link: https://lore.kernel.org/20260708111417.173443-2-kirill@shutemov.name Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org> Assisted-by: Claude:claude-opus-4-6 Acked-by: SeongJae Park <sj@kernel.org> Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: David Hildenbrand <david@kernel.org> Cc: James Houghton <jthoughton@google.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Liam Howlett <liam@infradead.org> Cc: Lorenzo Stoakes <ljs@kernel.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Peter Xu <peterx@redhat.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: Vlastimil Babka <vbabka@kernel.org> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>