linux/arch/x86/kernel/fpu, branch master

Merge tag 'mm-stable-2026-04-13-21-45' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-04-15T19:59:16Z

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 ...

mm/pkeys: remove unused tsk parameter from arch_set_user_pkey_access()

2026-04-05T20:52:57Z

The tsk parameter in arch_set_user_pkey_access() is never used in the function implementations across all architectures (arm64, powerpc, x86). Link: https://lkml.kernel.org/r/20260219063506.545148-1-sgsu.park@samsung.com Signed-off-by: Seongsu Park Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Ingo Molnar Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Thomas Gleixner Cc: Will Deacon Signed-off-by: Andrew Morton

x86/fpu: Correct misspelled xfeaures_to_write local var

2026-04-04T12:11:46Z

It happens. Fix it. No functional changes. Signed-off-by: Borislav Petkov (AMD) Link: https://patch.msgid.link/20260404120048.14765-1-bp@kernel.org

x86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]=1

2026-01-10T06:17:16Z

When loading guest XSAVE state via KVM_SET_XSAVE, and when updating XFD in response to a guest WRMSR, clear XFD-disabled features in the saved (or to be restored) XSTATE_BV to ensure KVM doesn't attempt to load state for features that are disabled via the guest's XFD. Because the kernel executes XRSTOR with the guest's XFD, saving XSTATE_BV[i]=1 with XFD[i]=1 will cause XRSTOR to #NM and panic the kernel. E.g. if fpu_update_guest_xfd() sets XFD without clearing XSTATE_BV: ------------[ cut here ]------------ WARNING: arch/x86/kernel/traps.c:1524 at exc_device_not_available+0x101/0x110, CPU#29: amx_test/848 Modules linked in: kvm_intel kvm irqbypass CPU: 29 UID: 1000 PID: 848 Comm: amx_test Not tainted 6.19.0-rc2-ffa07f7fd437-x86_amx_nm_xfd_non_init-vm #171 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:exc_device_not_available+0x101/0x110 Call Trace: asm_exc_device_not_available+0x1a/0x20 RIP: 0010:restore_fpregs_from_fpstate+0x36/0x90 switch_fpu_return+0x4a/0xb0 kvm_arch_vcpu_ioctl_run+0x1245/0x1e40 [kvm] kvm_vcpu_ioctl+0x2c3/0x8f0 [kvm] __x64_sys_ioctl+0x8f/0xd0 do_syscall_64+0x62/0x940 entry_SYSCALL_64_after_hwframe+0x4b/0x53 ---[ end trace 0000000000000000 ]--- This can happen if the guest executes WRMSR(MSR_IA32_XFD) to set XFD[18] = 1, and a host IRQ triggers kernel_fpu_begin() prior to the vmexit handler's call to fpu_update_guest_xfd(). and if userspace stuffs XSTATE_BV[i]=1 via KVM_SET_XSAVE: ------------[ cut here ]------------ WARNING: arch/x86/kernel/traps.c:1524 at exc_device_not_available+0x101/0x110, CPU#14: amx_test/867 Modules linked in: kvm_intel kvm irqbypass CPU: 14 UID: 1000 PID: 867 Comm: amx_test Not tainted 6.19.0-rc2-2dace9faccd6-x86_amx_nm_xfd_non_init-vm #168 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:exc_device_not_available+0x101/0x110 Call Trace: asm_exc_device_not_available+0x1a/0x20 RIP: 0010:restore_fpregs_from_fpstate+0x36/0x90 fpu_swap_kvm_fpstate+0x6b/0x120 kvm_load_guest_fpu+0x30/0x80 [kvm] kvm_arch_vcpu_ioctl_run+0x85/0x1e40 [kvm] kvm_vcpu_ioctl+0x2c3/0x8f0 [kvm] __x64_sys_ioctl+0x8f/0xd0 do_syscall_64+0x62/0x940 entry_SYSCALL_64_after_hwframe+0x4b/0x53 ---[ end trace 0000000000000000 ]--- The new behavior is consistent with the AMX architecture. Per Intel's SDM, XSAVE saves XSTATE_BV as '0' for components that are disabled via XFD (and non-compacted XSAVE saves the initial configuration of the state component): If XSAVE, XSAVEC, XSAVEOPT, or XSAVES is saving the state component i, the instruction does not generate #NM when XCR0[i] = IA32_XFD[i] = 1; instead, it operates as if XINUSE[i] = 0 (and the state component was in its initial state): it saves bit i of XSTATE_BV field of the XSAVE header as 0; in addition, XSAVE saves the initial configuration of the state component (the other instructions do not save state component i). Alternatively, KVM could always do XRSTOR with XFD=0, e.g. by using a constant XFD based on the set of enabled features when XSAVEing for a struct fpu_guest. However, having XSTATE_BV[i]=1 for XFD-disabled features can only happen in the above interrupt case, or in similar scenarios involving preemption on preemptible kernels, because fpu_swap_kvm_fpstate()'s call to save_fpregs_to_fpstate() saves the outgoing FPU state with the current XFD; and that is (on all but the first WRMSR to XFD) the guest XFD. Therefore, XFD can only go out of sync with XSTATE_BV in the above interrupt case, or in similar scenarios involving preemption on preemptible kernels, and it we can consider it (de facto) part of KVM ABI that KVM_GET_XSAVE returns XSTATE_BV[i]=0 for XFD-disabled features. Reported-by: Paolo Bonzini Cc: stable@vger.kernel.org Fixes: 820a6ee944e7 ("kvm: x86: Add emulation for IA32_XFD", 2022-01-14) Signed-off-by: Sean Christopherson [Move clearing of XSTATE_BV from fpu_copy_uabi_to_guest_fpstate to kvm_vcpu_ioctl_x86_set_xsave. - Paolo] Reviewed-by: Binbin Wu Signed-off-by: Paolo Bonzini

x86/fpu: Fix FPU state core dump truncation on CPUs with no extended xfeatures

2025-12-10T07:44:34Z

Zero can be a valid value of num_records. For example, on Intel Atom x6425RE, only x87 and SSE are supported (features 0, 1), and fpu_user_cfg.max_features is 3. The for_each_extended_xfeature() loop only iterates feature 2, which is not enabled, so num_records = 0. This is valid and should not cause core dump failure. The issue is that dump_xsave_layout_desc() returns 0 for both genuine errors (dump_emit() failure) and valid cases (no extended features). Use negative return values for errors and only abort on genuine failures. Fixes: ba386777a30b ("x86/elf: Add a new FPU buffer layout info to x86 core files") Signed-off-by: Yongxin Liu Signed-off-by: Ingo Molnar Link: https://patch.msgid.link/20251210000219.4094353-2-yongxin.liu@windriver.com

x86: Restrict KVM-induced symbol exports to KVM modules where obvious/possible

2025-11-12T23:29:38Z

Extend KVM's export macro framework to provide EXPORT_SYMBOL_FOR_KVM(), and use the helper macro to export symbols for KVM throughout x86 if and only if KVM will build one or more modules, and only for those modules. To avoid unnecessary exports when CONFIG_KVM=m but kvm.ko will not be built (because no vendor modules are selected), let arch code #define EXPORT_SYMBOL_FOR_KVM to suppress/override the exports. Note, the set of symbols to restrict to KVM was generated by manual search and audit; any "misses" are due to human error, not some grand plan. Signed-off-by: Sean Christopherson Signed-off-by: Dave Hansen Acked-by: Kai Huang Tested-by: Kai Huang Link: https://patch.msgid.link/20251112173944.1380633-5-seanjc%40google.com

x86/fpu: Ensure XFD state on signal delivery

2025-10-28T19:10:59Z

Sean reported [1] the following splat when running KVM tests: WARNING: CPU: 232 PID: 15391 at xfd_validate_state+0x65/0x70 Call Trace: fpu__clear_user_states+0x9c/0x100 arch_do_signal_or_restart+0x142/0x210 exit_to_user_mode_loop+0x55/0x100 do_syscall_64+0x205/0x2c0 entry_SYSCALL_64_after_hwframe+0x4b/0x53 Chao further identified [2] a reproducible scenario involving signal delivery: a non-AMX task is preempted by an AMX-enabled task which modifies the XFD MSR. When the non-AMX task resumes and reloads XSTATE with init values, a warning is triggered due to a mismatch between fpstate::xfd and the CPU's current XFD state. fpu__clear_user_states() does not currently re-synchronize the XFD state after such preemption. Invoke xfd_update_state() which detects and corrects the mismatch if there is a dynamic feature. This also benefits the sigreturn path, as fpu__restore_sig() may call fpu__clear_user_states() when the sigframe is inaccessible. [ dhansen: minor changelog munging ] Closes: https://lore.kernel.org/lkml/aDCo_SczQOUaB2rS@google.com [1] Fixes: 672365477ae8a ("x86/fpu: Update XFD state where required") Reported-by: Sean Christopherson Signed-off-by: Chang S. Bae Signed-off-by: Dave Hansen Reviewed-by: Chao Gao Tested-by: Chao Gao Link: https://lore.kernel.org/all/aDWbctO%2FRfTGiCg3@intel.com [2] Cc:stable@vger.kernel.org Link: https://patch.msgid.link/20250610001700.4097-1-chang.seok.bae%40intel.com

Merge tag 'kernel-6.18-rc1.clone3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2025-09-29T17:36:50Z

Pull copy_process updates from Christian Brauner: "This contains the changes to enable support for clone3() on nios2 which apparently is still a thing. The more exciting part of this is that it cleans up the inconsistency in how the 64-bit flag argument is passed from copy_process() into the various other copy_*() helpers" [ Fixed up rv ltl_monitor 32-bit support as per Sasha Levin in the merge ] * tag 'kernel-6.18-rc1.clone3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: nios2: implement architecture-specific portion of sys_clone3 arch: copy_thread: pass clone_flags as u64 copy_process: pass clone_flags as u64 across calltree copy_sighand: Handle architectures where sizeof(unsigned long) < sizeof(u64)

arch: copy_thread: pass clone_flags as u64

2025-09-01T13:31:34Z

With the introduction of clone3 in commit 7f192e3cd316 ("fork: add clone3") the effective bit width of clone_flags on all architectures was increased from 32-bit to 64-bit, with a new type of u64 for the flags. However, for most consumers of clone_flags the interface was not changed from the previous type of unsigned long. While this works fine as long as none of the new 64-bit flag bits (CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still undesirable in terms of the principle of least surprise. Thus, this commit fixes all relevant interfaces of the copy_thread function that is called from copy_process to consistently pass clone_flags as u64, so that no truncation to 32-bit integers occurs on 32-bit architectures. Signed-off-by: Simon Schuster Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-3-53fcf5577d57@siemens-energy.com Fixes: c5febea0956fd387 ("fork: Pass struct kernel_clone_args into copy_thread") Acked-by: Guo Ren (Alibaba Damo Academy) Acked-by: Andreas Larsson # sparc Acked-by: David Hildenbrand Acked-by: Geert Uytterhoeven # m68k Reviewed-by: Arnd Bergmann Signed-off-by: Christian Brauner

x86/fpu: Fix NULL dereference in avx512_status()

2025-08-11T20:28:07Z

Problem ------- With CONFIG_X86_DEBUG_FPU enabled, reading /proc/[kthread]/arch_status causes a warning and a NULL pointer dereference. This is because the AVX-512 timestamp code uses x86_task_fpu() but doesn't check it for NULL. CONFIG_X86_DEBUG_FPU addles that function for kernel threads (PF_KTHREAD specifically), making it return NULL. The point of the warning was to ensure that kernel threads only access task->fpu after going through kernel_fpu_begin()/_end(). Note: all kernel tasks exposed in /proc have a valid task->fpu. Solution -------- One option is to silence the warning and check for NULL from x86_task_fpu(). However, that warning is fairly fresh and seems like a defense against misuse of the FPU state in kernel threads. Instead, stop outputting AVX-512_elapsed_ms for kernel threads altogether. The data was garbage anyway because avx512_timestamp is only updated for user threads, not kernel threads. If anyone ever wants to track kernel thread AVX-512 use, they can come back later and do it properly, separate from this bug fix. [ dhansen: mostly rewrite changelog ] Fixes: 22aafe3bcb67 ("x86/fpu: Remove init_task FPU state dependencies, add debugging warning for PF_KTHREAD tasks") Co-developed-by: Sohil Mehta Signed-off-by: Sohil Mehta Signed-off-by: Fushuai Wang Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20250811185044.2227268-1-sohil.mehta%40intel.com