Hi, pte_t currently describes both a software PTE value and an element stored in a PTE table. Consequently, pte_t * can point either to a software PTE value, often a stack copy, or to a PTE-table slot. The compiler cannot distinguish these cases. A value pointer can therefore be passed to an interface that expects table storage, while table storage can be read by direct dereference instead of the architecture accessor.
This series begins a staged conversion at the PTE level. It introduces hw_pte_t as the element type for PTE-table storage and converts generic MM to use hw_pte_t *. Software PTE values remain pte_t. Interfaces that intentionally return a value through pte_t *, such as install_pte, remain value interfaces; the relevant parameters are named ptentp to make that distinction explicit. The generic definition aliases hw_pte_t to pte_t unless an architecture selects ARCH_HAS_HW_PTE_T, which enables a distinct generic wrapper named __hw_pte_t. Some architectures define pgtable_t in headers parsed before the generic hw_pte_t typedef is visible. The structure tag allows those headers to define pgtable_t as struct __hw_pte_t * without creating an include-order dependency. This is required when converting s390, m68k, powerpc and sparc. No architecture selects ARCH_HAS_HW_PTE_T in this series, so the representation and behavior of every architecture are preserved. ptep_get() keeps its existing READ_ONCE() semantics and converts the stored element through __pte_from_hw(). An architecture can later select the option and convert its PTE interfaces to make the distinction compiler-enforced. Architecture PTE implementations and most architecture code are deliberately left for those later opt-in conversions. Here, hw_pte_t identifies PTE-table storage rather than table lifetime: complete PTE tables use hw_pte_t whether or not they are currently linked into a page-table hierarchy, while software PTE values use pte_t. The distinction between complete but unlinked tables and hardware-reachable tables was raised during discussion and remains an important point for review. PMD, PUD, P4D and PGD storage are deliberately out of scope. They can be converted in later series after the PTE boundary is agreed, avoiding the PMD-specific cases that made an all-level conversion difficult to review. Most mechanical pointer conversions were generated with the Coccinelle script included below, then audited and fixed by hand. This series does not add a second ptep_get_once() accessor and does not remove or replace STRICT_MM_TYPECHECKS. The design discussion is available at [1]; while the original idea came from [2]. I've the patches here [3] for arm64 conversion which I used to find usages in generic code which I missed during development. [1] https://lore.kernel.org/all/[email protected]/ [2] https://lore.kernel.org/all/[email protected] [3] https://lore.kernel.org/all/[email protected] Testing: Testing was performed with and without the series on both x86_64 and arm64. KUnit and the MM kselftests produced matching before-and-after results problems or regressions. Fastpath performance testing was also completed on arm64. No regression was found. Thanks, Usama --- Changes in v3: - Retitle the series - Moved hw_pte_val() adding helper to generic series - Link to v2: https://patch.msgid.link/[email protected] Changes in v2: - Name the generic wrapper structure __hw_pte_t so architectures can forward-declare it before the generic typedef is visible. - Use software PTE value terminology consistently - Fold the prerequisite header includes into the generic storage conversion - Explain why the NOMMU stub converts the stored entry without ptep_get(). - Rebase onto mm-new and rerun the Coccinelle conversion. - Link to v1: https://lore.kernel.org/all/[email protected] Changes in v1: - Add ARCH_HAS_HW_PTE_T so architectures can opt in to a distinct PTE-table storage type. - Define the distinct hw_pte_t wrapper and its conversion helpers in generic code instead of requiring each architecture to define them. - Read hw_pte_t through READ_ONCE() before converting it to pte_t. - Drop the previous mremap patch in favour of [a]. Apply [a] first if it is not already present. - Drop the previous two dead-code conversion patches; the affected code was cleaned up separately in [b] and [c]. - Link to RFC: https://lore.kernel.org/all/[email protected] [a] https://lore.kernel.org/linux-mm/[email protected]/ [b] https://lore.kernel.org/all/[email protected] [c] https://lore.kernel.org/all/[email protected] --- // SPDX-License-Identifier: GPL-2.0-only /// /// Rename raw PTE pointer types to hardware PTE pointer types. /// /// This is a mechanical type rename. It converts common declarations, /// function parameters, prototypes, return types and casts from "pte_t *" /// to "hw_pte_t *". Plain "pte_t" objects are intentionally left unchanged. /// Pointers named "ptentp" refer to temporary software PTE values and are /// intentionally ignored in all modes. /// Re-run in context mode afterwards to audit remaining raw pte_t pointers /// and cases that need hand conversion, such as trace macros and mixed /// declarations. /// /// Confidence: Moderate // Options: --no-includes --include-headers virtual patch virtual report virtual context @local_decl depends on patch@ identifier x != ptentp; @@ - pte_t *x; + hw_pte_t *x; @local_decl_init depends on patch@ identifier x != ptentp; expression e; @@ - pte_t *x = e; + hw_pte_t *x = e; @param_proto depends on patch@ identifier f; identifier x != ptentp; type R; @@ R f(..., - pte_t *x + hw_pte_t *x ,...); @param_proto_unnamed depends on patch@ identifier f; type R; @@ R f(..., - pte_t * + hw_pte_t * ,...); @param_def depends on patch@ identifier f; identifier x != ptentp; type R; @@ R f(..., - pte_t *x + hw_pte_t *x ,...) { ... } @ret_proto depends on patch@ identifier f; parameter list ps; @@ - pte_t * + hw_pte_t * f(ps); @ret_def depends on patch@ identifier f; parameter list ps; @@ - pte_t * + hw_pte_t * f(ps) { ... } @struct_member depends on patch@ identifier S; identifier x != ptentp; @@ struct S { ... - pte_t *x; + hw_pte_t *x; ... }; @union_member depends on patch@ identifier x != ptentp; @@ union { ... - pte_t *x; + hw_pte_t *x; ... }; @union_member_in_struct depends on patch@ identifier S; identifier x != ptentp; @@ struct S { ... union { ... - pte_t *x; + hw_pte_t *x; ... }; ... }; @fnptr_struct_member depends on patch@ identifier S,f; identifier x != ptentp; type R; @@ struct S { ... R (*f)(..., - pte_t *x + hw_pte_t *x ,...); ... }; @fnptr_typedef_pte_fn_t depends on patch@ identifier x != ptentp; @@ typedef int (*pte_fn_t)(..., - pte_t *x + hw_pte_t *x ,...); @cast depends on patch@ expression e; @@ - (pte_t *)e + (hw_pte_t *)e @remaining_decl depends on context || report@ identifier x != ptentp; position p; @@ * pte_t *x@p; @remaining_decl_init depends on context || report@ identifier x != ptentp; expression e; position p; @@ * pte_t *x@p = e; @remaining_param_proto depends on context || report@ identifier f; identifier x != ptentp; type R; position p; @@ R f(..., * pte_t *x@p ,...); @remaining_param_proto_unnamed depends on context || report@ identifier f; type R; position p; @@ R f(..., * pte_t *@p ,...); @remaining_param_def depends on context || report@ identifier f; identifier x != ptentp; type R; position p; @@ R f(..., * pte_t *x@p ,...) { ... } @remaining_ret_proto depends on context || report@ identifier f; parameter list ps; position p; @@ * pte_t *f@p(ps); @remaining_ret_def depends on context || report@ identifier f; parameter list ps; position p; @@ * pte_t *f@p(ps) { ... } @remaining_struct_member depends on context || report@ identifier S; identifier x != ptentp; position p; @@ struct S { ... * pte_t *x@p; ... }; @remaining_union_member depends on context || report@ identifier x != ptentp; position p; @@ union { ... * pte_t *x@p; ... }; @remaining_union_member_in_struct depends on context || report@ identifier S; identifier x != ptentp; position p; @@ struct S { ... union { ... * pte_t *x@p; ... }; ... }; @remaining_fnptr_struct_member depends on context || report@ identifier S,f; identifier x != ptentp; type R; position p; @@ struct S { ... R (*f)(..., * pte_t *x@p ,...); ... }; @remaining_fnptr_typedef_pte_fn_t depends on context || report@ identifier x != ptentp; position p; @@ typedef int (*pte_fn_t)(..., * pte_t *x@p ,...); --- To: Andrew Morton <[email protected]> To: David Hildenbrand <[email protected]> To: Lorenzo Stoakes <[email protected]> To: "Liam R. Howlett" <[email protected]> To: Vlastimil Babka <[email protected]> To: Mike Rapoport <[email protected]> To: Suren Baghdasaryan <[email protected]> To: Michal Hocko <[email protected]> To: Xu Xin <[email protected]> To: Chengming Zhou <[email protected]> To: Jann Horn <[email protected]> To: Muchun Song <[email protected]> To: Oscar Salvador <[email protected]> To: Pedro Falcato <[email protected]> To: Arnd Bergmann <[email protected]> To: Will Deacon <[email protected]> To: "Aneesh Kumar K.V" <[email protected]> To: Nick Piggin <[email protected]> To: Peter Zijlstra <[email protected]> To: Pasha Tatashin <[email protected]> To: Rik van Riel <[email protected]> To: Harry Yoo <[email protected]> To: Lance Yang <[email protected]> To: Chris Li <[email protected]> To: Kairui Song <[email protected]> To: Kemeng Shi <[email protected]> To: Nhat Pham <[email protected]> To: Baoquan He <[email protected]> To: Barry Song <[email protected]> To: Youngjun Park <[email protected]> To: Uladzislau Rezki <[email protected]> To: Steven Rostedt <[email protected]> To: Masami Hiramatsu <[email protected]> To: Mathieu Desnoyers <[email protected]> To: Alexei Starovoitov <[email protected]> To: Daniel Borkmann <[email protected]> To: Andrii Nakryiko <[email protected]> To: Eduard Zingerman <[email protected]> To: Kumar Kartikeya Dwivedi <[email protected]> To: Martin KaFai Lau <[email protected]> To: Song Liu <[email protected]> To: Yonghong Song <[email protected]> To: Jiri Olsa <[email protected]> To: Emil Tsalapatis <[email protected]> To: Ihor Solodrai <[email protected]> To: Ingo Molnar <[email protected]> To: Arnaldo Carvalho de Melo <[email protected]> To: Namhyung Kim <[email protected]> To: Mark Rutland <[email protected]> To: Alexander Shishkin <[email protected]> To: Ian Rogers <[email protected]> To: Adrian Hunter <[email protected]> To: James Clark <[email protected]> To: SJ Park <[email protected]> To: "Matthew Wilcox (Oracle)" <[email protected]> To: Jan Kara <[email protected]> To: Jason Gunthorpe <[email protected]> To: John Hubbard <[email protected]> To: Peter Xu <[email protected]> To: Leon Romanovsky <[email protected]> To: Zi Yan <[email protected]> To: Baolin Wang <[email protected]> To: Nico Pache <[email protected]> To: Ryan Roberts <[email protected]> To: Dev Jain <[email protected]> To: Usama Arif <[email protected]> To: Kiryl Shutsemau <[email protected]> To: Andrey Ryabinin <[email protected]> To: Alexander Potapenko <[email protected]> To: Andrey Konovalov <[email protected]> To: Dmitry Vyukov <[email protected]> To: Vincenzo Frascino <[email protected]> To: Miaohe Lin <[email protected]> To: Naoya Horiguchi <[email protected]> To: Matthew Brost <[email protected]> To: Joshua Hahn <[email protected]> To: Rakie Kim <[email protected]> To: Byungchul Park <[email protected]> To: Gregory Price <[email protected]> To: Ying Huang <[email protected]> To: Alistair Popple <[email protected]> To: Dennis Zhou <[email protected]> To: Tejun Heo <[email protected]> To: Christoph Lameter <[email protected]> To: Johannes Weiner <[email protected]> To: Qi Zheng <[email protected]> To: Shakeel Butt <[email protected]> To: Axel Rasmussen <[email protected]> To: Yuanchu Xie <[email protected]> To: Wei Xu <[email protected]> To: Jani Nikula <[email protected]> To: Joonas Lahtinen <[email protected]> To: Rodrigo Vivi <[email protected]> To: Tvrtko Ursulin <[email protected]> To: David Airlie <[email protected]> To: Simona Vetter <[email protected]> To: Juergen Gross <[email protected]> To: Stefano Stabellini <[email protected]> To: Oleksandr Tyshchenko <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: Muhammad Usama Anjum <[email protected]> --- Muhammad Usama Anjum (9): mm: introduce hw_pte_t for PTE table storage mm: rename pointers to software PTE values as ptentp mm: use hw_pte_t for generic PTE table storage mm: convert PTE table entries in ptep_get() mm: convert PTE table entry to pte mm: add hw_pte_val for HW PTE storage mm/kasan: use hw_pte_t for the early shadow PTE table drm/i915: use hw_pte_t for PTE range callbacks xen: use hw_pte_t for PTE range callbacks MAINTAINERS | 1 + drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c | 4 +-- drivers/gpu/drm/i915/i915_mm.c | 4 +-- drivers/xen/gntdev.c | 2 +- drivers/xen/privcmd.c | 2 +- drivers/xen/xenbus/xenbus_client.c | 2 +- drivers/xen/xlate_mmu.c | 4 +-- fs/hugetlbfs/inode.c | 3 +- fs/proc/task_mmu.c | 33 ++++++++++---------- include/asm-generic/hugetlb.h | 15 ++++----- include/asm-generic/pgalloc.h | 6 ++-- include/asm-generic/tlb.h | 5 +-- include/linux/hugetlb.h | 53 +++++++++++++++++-------------- include/linux/kasan.h | 2 +- include/linux/mm.h | 26 ++++++++-------- include/linux/page_table_check.h | 10 ++++-- include/linux/pagewalk.h | 10 +++--- include/linux/pgtable.h | 81 +++++++++++++++++++++++++----------------------- include/linux/pgtable_types.h | 23 ++++++++++++++ include/linux/rmap.h | 2 +- include/linux/swapops.h | 6 ++-- include/linux/vmalloc.h | 4 +-- include/trace/events/xen.h | 10 +++--- kernel/bpf/arena.c | 9 +++--- kernel/events/core.c | 3 +- mm/Kconfig | 3 ++ mm/damon/ops-common.c | 2 +- mm/damon/ops-common.h | 2 +- mm/damon/vaddr.c | 20 ++++++------ mm/debug_vm_pgtable.c | 2 +- mm/filemap.c | 4 +-- mm/gup.c | 9 +++--- mm/highmem.c | 15 ++++----- mm/hmm.c | 6 ++-- mm/huge_memory.c | 4 +-- mm/hugetlb.c | 60 ++++++++++++++++++----------------- mm/hugetlb_vmemmap.c | 13 ++++---- mm/internal.h | 16 +++++----- mm/kasan/init.c | 14 ++++----- mm/kasan/shadow.c | 6 ++-- mm/khugepaged.c | 50 ++++++++++++++++++------------ mm/ksm.c | 11 ++++--- mm/madvise.c | 18 ++++++----- mm/mapping_dirty_helpers.c | 4 +-- mm/memory-failure.c | 6 ++-- mm/memory.c | 78 +++++++++++++++++++++++----------------------- mm/mempolicy.c | 4 +-- mm/migrate.c | 4 +-- mm/migrate_device.c | 4 +-- mm/mincore.c | 4 +-- mm/mlock.c | 4 +-- mm/mprotect.c | 19 ++++++------ mm/mremap.c | 4 +-- mm/page_table_check.c | 4 +-- mm/pagewalk.c | 9 +++--- mm/percpu.c | 2 +- mm/pgtable-generic.c | 20 ++++++------ mm/ptdump.c | 4 +-- mm/rmap.c | 6 ++-- mm/sparse-vmemmap.c | 22 ++++++------- mm/swap_state.c | 3 +- mm/swapfile.c | 5 +-- mm/userfaultfd.c | 32 ++++++++++--------- mm/util.c | 2 +- mm/vmalloc.c | 11 ++++--- mm/vmscan.c | 6 ++-- 66 files changed, 457 insertions(+), 375 deletions(-) --- base-commit: ead700ca770c82167af32622cf8b68c9f87c3c7c change-id: 20260914-pte0-6c88f5592d79 Best regards, -- Usama
