user/sven/linux.git/include/linux/vmalloc.h, branch v6.1.152

mm: move page table sync declarations to linux/pgtable.h

2025-09-09T16:54:17Z

commit 7cc183f2e67d19b03ee5c13a6664b8c6cc37ff9d upstream. During our internal testing, we started observing intermittent boot failures when the machine uses 4-level paging and has a large amount of persistent memory: BUG: unable to handle page fault for address: ffffe70000000034 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI RIP: 0010:__init_single_page+0x9/0x6d Call Trace: __init_zone_device_page+0x17/0x5d memmap_init_zone_device+0x154/0x1bb pagemap_range+0x2e0/0x40f memremap_pages+0x10b/0x2f0 devm_memremap_pages+0x1e/0x60 dev_dax_probe+0xce/0x2ec [device_dax] dax_bus_probe+0x6d/0xc9 [... snip ...] It turns out that the kernel panics while initializing vmemmap (struct page array) when the vmemmap region spans two PGD entries, because the new PGD entry is only installed in init_mm.pgd, but not in the page tables of other tasks. And looking at __populate_section_memmap(): if (vmemmap_can_optimize(altmap, pgmap)) // does not sync top level page tables r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap); else // sync top level page tables in x86 r = vmemmap_populate(start, end, nid, altmap); In the normal path, vmemmap_populate() in arch/x86/mm/init_64.c synchronizes the top level page table (See commit 9b861528a801 ("x86-64, mem: Update all PGDs for direct mapping and vmemmap mapping changes")) so that all tasks in the system can see the new vmemmap area. However, when vmemmap_can_optimize() returns true, the optimized path skips synchronization of top-level page tables. This is because vmemmap_populate_compound_pages() is implemented in core MM code, which does not handle synchronization of the top-level page tables. Instead, the core MM has historically relied on each architecture to perform this synchronization manually. We're not the first party to encounter a crash caused by not-sync'd top level page tables: earlier this year, Gwan-gyeong Mun attempted to address the issue [1] [2] after hitting a kernel panic when x86 code accessed the vmemmap area before the corresponding top-level entries were synced. At that time, the issue was believed to be triggered only when struct page was enlarged for debugging purposes, and the patch did not get further updates. It turns out that current approach of relying on each arch to handle the page table sync manually is fragile because 1) it's easy to forget to sync the top level page table, and 2) it's also easy to overlook that the kernel should not access the vmemmap and direct mapping areas before the sync. # The solution: Make page table sync more code robust and harder to miss To address this, Dave Hansen suggested [3] [4] introducing {pgd,p4d}_populate_kernel() for updating kernel portion of the page tables and allow each architecture to explicitly perform synchronization when installing top-level entries. With this approach, we no longer need to worry about missing the sync step, reducing the risk of future regressions. The new interface reuses existing ARCH_PAGE_TABLE_SYNC_MASK, PGTBL_P*D_MODIFIED and arch_sync_kernel_mappings() facility used by vmalloc and ioremap to synchronize page tables. pgd_populate_kernel() looks like this: static inline void pgd_populate_kernel(unsigned long addr, pgd_t *pgd, p4d_t *p4d) { pgd_populate(&init_mm, pgd, p4d); if (ARCH_PAGE_TABLE_SYNC_MASK & PGTBL_PGD_MODIFIED) arch_sync_kernel_mappings(addr, addr); } It is worth noting that vmalloc() and apply_to_range() carefully synchronizes page tables by calling p*d_alloc_track() and arch_sync_kernel_mappings(), and thus they are not affected by this patch series. This series was hugely inspired by Dave Hansen's suggestion and hence added Suggested-by: Dave Hansen. Cc stable because lack of this series opens the door to intermittent boot failures. This patch (of 3): Move ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() to linux/pgtable.h so that they can be used outside of vmalloc and ioremap. Link: https://lkml.kernel.org/r/20250818020206.4517-1-harry.yoo@oracle.com Link: https://lkml.kernel.org/r/20250818020206.4517-2-harry.yoo@oracle.com Link: https://lore.kernel.org/linux-mm/20250220064105.808339-1-gwan-gyeong.mun@intel.com [1] Link: https://lore.kernel.org/linux-mm/20250311114420.240341-1-gwan-gyeong.mun@intel.com [2] Link: https://lore.kernel.org/linux-mm/d1da214c-53d3-45ac-a8b6-51821c5416e4@intel.com [3] Link: https://lore.kernel.org/linux-mm/4d800744-7b88-41aa-9979-b245e8bf794b@intel.com [4] Fixes: 8d400913c231 ("x86/vmemmap: handle unpopulated sub-pmd ranges") Signed-off-by: Harry Yoo Acked-by: Kiryl Shutsemau Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: "Uladzislau Rezki (Sony)" Reviewed-by: Lorenzo Stoakes Acked-by: David Hildenbrand Cc: Alexander Potapenko Cc: Alistair Popple Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Andy Lutomirski Cc: "Aneesh Kumar K.V" Cc: Anshuman Khandual Cc: Ard Biesheuvel Cc: Arnd Bergmann Cc: bibo mao Cc: Borislav Betkov Cc: Christoph Lameter (Ampere) Cc: Dennis Zhou Cc: Dev Jain Cc: Dmitriy Vyukov Cc: Gwan-gyeong Mun Cc: Ingo Molnar Cc: Jane Chu Cc: Joao Martins Cc: Joerg Roedel Cc: John Hubbard Cc: Kevin Brodsky Cc: Liam Howlett Cc: Michal Hocko Cc: Oscar Salvador Cc: Peter Xu Cc: Peter Zijlstra Cc: Qi Zheng Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Tejun Heo Cc: Thomas Gleinxer Cc: Thomas Huth Cc: Vincenzo Frascino Cc: Vlastimil Babka Cc: Dave Hansen Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

usercopy: Handle vm_map_ram() areas

2022-06-13T16:54:52Z

vmalloc does not allocate a vm_struct for vm_map_ram() areas. That causes us to deny usercopies from those areas. This affects XFS which uses vm_map_ram() for its directories. Fix this by calling find_vmap_area() instead of find_vm_area(). Fixes: 0aef499f3172 ("mm/usercopy: Detect vmalloc overruns") Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Uladzislau Rezki (Sony) Tested-by: Zorro Lang Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20220612213227.3881769-2-willy@infradead.org

vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP

2022-04-19T19:08:57Z

Huge page backed vmalloc memory could benefit performance in many cases. However, some users of vmalloc may not be ready to handle huge pages for various reasons: hardware constraints, potential pages split, etc. VM_NO_HUGE_VMAP was introduced to allow vmalloc users to opt-out huge pages. However, it is not easy to track down all the users that require the opt-out, as the allocation are passed different stacks and may cause issues in different layers. To address this issue, replace VM_NO_HUGE_VMAP with an opt-in flag, VM_ALLOW_HUGE_VMAP, so that users that benefit from huge pages could ask specificially. Also, remove vmalloc_no_huge() and add opt-in helper vmalloc_huge(). Fixes: fac54e2bfb5b ("x86/Kconfig: Select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP") Link: https://lore.kernel.org/netdev/14444103-d51b-0fb3-ee63-c3f182f0b546@molgen.mpg.de/" Reviewed-by: Christoph Hellwig Signed-off-by: Song Liu Reviewed-by: Rik van Riel Signed-off-by: Linus Torvalds

kasan, vmalloc, arm64: mark vmalloc mappings as pgprot_tagged

2022-03-25T02:06:47Z

HW_TAGS KASAN relies on ARM Memory Tagging Extension (MTE). With MTE, a memory region must be mapped as MT_NORMAL_TAGGED to allow setting memory tags via MTE-specific instructions. Add proper protection bits to vmalloc() allocations. These allocations are always backed by page_alloc pages, so the tags will actually be getting set on the corresponding physical memory. Link: https://lkml.kernel.org/r/983fc33542db2f6b1e77b34ca23448d4640bbb9e.1643047180.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Co-developed-by: Vincenzo Frascino Signed-off-by: Vincenzo Frascino Acked-by: Marco Elver Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Catalin Marinas Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Mark Rutland Cc: Peter Collingbourne Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan, vmalloc: drop outdated VM_KASAN comment

2022-03-25T02:06:47Z

The comment about VM_KASAN in include/linux/vmalloc.c is outdated. VM_KASAN is currently only used to mark vm_areas allocated for kernel modules when CONFIG_KASAN_VMALLOC is disabled. Drop the comment. Link: https://lkml.kernel.org/r/780395afea83a147b3b5acc36cf2e38f7f8479f9.1643047180.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Alexander Potapenko Acked-by: Marco Elver Cc: Andrey Ryabinin Cc: Catalin Marinas Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Mark Rutland Cc: Peter Collingbourne Cc: Vincenzo Frascino Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2022-03-24T18:58:57Z

Pull kvm updates from Paolo Bonzini: "ARM: - Proper emulation of the OSLock feature of the debug architecture - Scalibility improvements for the MMU lock when dirty logging is on - New VMID allocator, which will eventually help with SVA in VMs - Better support for PMUs in heterogenous systems - PSCI 1.1 support, enabling support for SYSTEM_RESET2 - Implement CONFIG_DEBUG_LIST at EL2 - Make CONFIG_ARM64_ERRATUM_2077057 default y - Reduce the overhead of VM exit when no interrupt is pending - Remove traces of 32bit ARM host support from the documentation - Updated vgic selftests - Various cleanups, doc updates and spelling fixes RISC-V: - Prevent KVM_COMPAT from being selected - Optimize __kvm_riscv_switch_to() implementation - RISC-V SBI v0.3 support s390: - memop selftest - fix SCK locking - adapter interruptions virtualization for secure guests - add Claudio Imbrenda as maintainer - first step to do proper storage key checking x86: - Continue switching kvm_x86_ops to static_call(); introduce static_call_cond() and __static_call_ret0 when applicable. - Cleanup unused arguments in several functions - Synthesize AMD 0x80000021 leaf - Fixes and optimization for Hyper-V sparse-bank hypercalls - Implement Hyper-V's enlightened MSR bitmap for nested SVM - Remove MMU auditing - Eager splitting of page tables (new aka "TDP" MMU only) when dirty page tracking is enabled - Cleanup the implementation of the guest PGD cache - Preparation for the implementation of Intel IPI virtualization - Fix some segment descriptor checks in the emulator - Allow AMD AVIC support on systems with physical APIC ID above 255 - Better API to disable virtualization quirks - Fixes and optimizations for the zapping of page tables: - Zap roots in two passes, avoiding RCU read-side critical sections that last too long for very large guests backed by 4 KiB SPTEs. - Zap invalid and defunct roots asynchronously via concurrency-managed work queue. - Allowing yielding when zapping TDP MMU roots in response to the root's last reference being put. - Batch more TLB flushes with an RCU trick. Whoever frees the paging structure now holds RCU as a proxy for all vCPUs running in the guest, i.e. to prolongs the grace period on their behalf. It then kicks the the vCPUs out of guest mode before doing rcu_read_unlock(). Generic: - Introduce __vcalloc and use it for very large allocations that need memcg accounting" * tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (246 commits) KVM: use kvcalloc for array allocations KVM: x86: Introduce KVM_CAP_DISABLE_QUIRKS2 kvm: x86: Require const tsc for RT KVM: x86: synthesize CPUID leaf 0x80000021h if useful KVM: x86: add support for CPUID leaf 0x80000021 KVM: x86: do not use KVM_X86_OP_OPTIONAL_RET0 for get_mt_mask Revert "KVM: x86/mmu: Zap only TDP MMU leafs in kvm_zap_gfn_range()" kvm: x86/mmu: Flush TLB before zap_gfn_range releases RCU KVM: arm64: fix typos in comments KVM: arm64: Generalise VM features into a set of flags KVM: s390: selftests: Add error memop tests KVM: s390: selftests: Add more copy memop tests KVM: s390: selftests: Add named stages for memop test KVM: s390: selftests: Add macro as abstraction for MEM_OP KVM: s390: selftests: Split memop tests KVM: s390x: fix SCK locking RISC-V: KVM: Implement SBI HSM suspend call RISC-V: KVM: Add common kvm_riscv_vcpu_wfi() function RISC-V: Add SBI HSM suspend related defines RISC-V: KVM: Implement SBI v0.3 SRST extension ...

mm/vmalloc: fix comments about vmap_area struct

2022-03-22T22:57:05Z

The vmap_area_root should be in the "busy" tree and the free_vmap_area_root should be in the "free" tree. Link: https://lkml.kernel.org/r/20220305011510.33596-1-libang.linuxer@gmail.com Fixes: 688fcbfc06e4 ("mm/vmalloc: modify struct vmap_area to reduce its size") Signed-off-by: Bang Li Reviewed-by: Uladzislau Rezki (Sony) Cc: Pengfei Li Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: vmalloc: introduce array allocation functions

2022-03-08T14:30:17Z

Linux has dozens of occurrences of vmalloc(array_size()) and vzalloc(array_size()). Allow to simplify the code by providing vmalloc_array and vcalloc, as well as the underscored variants that let the caller specify the GFP flags. Acked-by: Michal Hocko Signed-off-by: Paolo Bonzini

mm: defer kmemleak object creation of module_alloc()

2022-01-15T14:30:25Z

Yongqiang reports a kmemleak panic when module insmod/rmmod with KASAN enabled(without KASAN_VMALLOC) on x86[1]. When the module area allocates memory, it's kmemleak_object is created successfully, but the KASAN shadow memory of module allocation is not ready, so when kmemleak scan the module's pointer, it will panic due to no shadow memory with KASAN check. module_alloc __vmalloc_node_range kmemleak_vmalloc kmemleak_scan update_checksum kasan_module_alloc kmemleak_ignore Note, there is no problem if KASAN_VMALLOC enabled, the modules area entire shadow memory is preallocated. Thus, the bug only exits on ARCH which supports dynamic allocation of module area per module load, for now, only x86/arm64/s390 are involved. Add a VM_DEFER_KMEMLEAK flags, defer vmalloc'ed object register of kmemleak in module_alloc() to fix this issue. [1] https://lore.kernel.org/all/6d41e2b9-4692-5ec4-b1cd-cbe29ae89739@huawei.com/ [wangkefeng.wang@huawei.com: fix build] Link: https://lkml.kernel.org/r/20211125080307.27225-1-wangkefeng.wang@huawei.com [akpm@linux-foundation.org: simplify ifdefs, per Andrey] Link: https://lkml.kernel.org/r/CA+fCnZcnwJHUQq34VuRxpdoY6_XbJCDJ-jopksS5Eia4PijPzw@mail.gmail.com Link: https://lkml.kernel.org/r/20211124142034.192078-1-wangkefeng.wang@huawei.com Fixes: 793213a82de4 ("s390/kasan: dynamic shadow mem allocation for modules") Fixes: 39d114ddc682 ("arm64: add KASAN support") Fixes: bebf56a1b176 ("kasan: enable instrumentation of global variables") Signed-off-by: Kefeng Wang Reported-by: Yongqiang Liu Cc: Andrey Konovalov Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Catalin Marinas Cc: Will Deacon Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: Alexander Gordeev Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: Alexander Potapenko Cc: Kefeng Wang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/vmalloc: don't allow VM_NO_GUARD on vmap()

2021-11-06T20:30:36Z

The vmalloc guard pages are added on top of each allocation, thereby isolating any two allocations from one another. The top guard of the lower allocation is the bottom guard guard of the higher allocation etc. Therefore VM_NO_GUARD is dangerous; it breaks the basic premise of isolating separate allocations. There are only two in-tree users of this flag, neither of which use it through the exported interface. Ensure it stays this way. Link: https://lkml.kernel.org/r/YUMfdA36fuyZ+/xt@hirez.programming.kicks-ass.net Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Christoph Hellwig Reviewed-by: David Hildenbrand Acked-by: Will Deacon Acked-by: Kees Cook Cc: Andrey Konovalov Cc: Mel Gorman Cc: Uladzislau Rezki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds