kernel/linux.git/mm/mprotect.c, branch linux-7.1.y

mm/mprotect: special-case small folios when applying permissions

2026-04-18T07:10:55+00:00

The common order-0 case is important enough to want its own branch, and avoids the hairy, large loop logic that the CPU does not seem to handle particularly well. While at it, encourage the compiler to inline batch PTE logic and resolve constant branches by adding __always_inline strategically. Link: https://lore.kernel.org/20260402141628.3367596-3-pfalcato@suse.de Signed-off-by: Pedro Falcato Suggested-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes (Oracle) Tested-by: Luke Yang Reviewed-by: Vlastimil Babka (SUSE) Cc: Dev Jain Cc: Jann Horn Cc: Jiri Hladky Cc: Liam Howlett Cc: Davidlohr Bueso Signed-off-by: Andrew Morton

mm/mprotect: move softleaf code out of the main function

2026-04-18T07:10:55+00:00

Patch series "mm/mprotect: micro-optimization work", v3. Micro-optimize the change_protection functionality and the change_pte_range() routine. This set of functions works in an incredibly tight loop, and even small inefficiencies are incredibly evident when spun hundreds, thousands or hundreds of thousands of times. There was an attempt to keep the batching functionality as much as possible, which introduced some part of the slowness, but not all of it. Removing it for !arm64 architectures would speed mprotect() up even further, but could easily pessimize cases where large folios are mapped (which is not as rare as it seems, particularly when it comes to the page cache these days). The micro-benchmark used for the tests was [0] (usable using google/benchmark and g++ -O2 -lbenchmark repro.cpp) This resulted in the following (first entry is baseline): --------------------------------------------------------- Benchmark Time CPU Iterations --------------------------------------------------------- mprotect_bench 85967 ns 85967 ns 6935 mprotect_bench 70684 ns 70684 ns 9887 After the patchset we can observe an ~18% speedup in mprotect. Wonderful for the elusive mprotect-based workloads! Testing & more ideas welcome. I suspect there is plenty of improvement possible but it would require more time than what I have on my hands right now. The entire inlined function (which inlines into change_protection()) is gigantic - I'm not surprised this is so finnicky. Note: per my profiling, the next _big_ bottleneck here is modify_prot_start_ptes, exactly on the xchg() done by x86. ptep_get_and_clear() is _expensive_. I don't think there's a properly safe way to go about it since we do depend on the D bit quite a lot. This might not be such an issue on other architectures. Luke Yang reported [1]: : On average, we see improvements ranging from a minimum of 5% to a : maximum of 55%, with most improvements showing around a 25% speed up in : the libmicro/mprot_tw4m micro benchmark. This patch (of 2): Move softleaf change_pte_range code into a separate function. This makes the change_pte_range() function a good bit smaller, and lessens cognitive load when reading through the function. Link: https://lore.kernel.org/20260402141628.3367596-1-pfalcato@suse.de Link: https://lore.kernel.org/20260402141628.3367596-2-pfalcato@suse.de Link: https://lore.kernel.org/all/aY8-XuFZ7zCvXulB@luyang-thinkpadp1gen7.toromso.csb/ Link: https://gist.github.com/heatd/1450d273005aba91fa5744f44dfcd933 [0] Link: https://lore.kernel.org/CAL2CeBxT4jtJ+LxYb6=BNxNMGinpgD_HYH5gGxOP-45Q2OncqQ@mail.gmail.com [1] Signed-off-by: Pedro Falcato Reviewed-by: Lorenzo Stoakes (Oracle) Acked-by: David Hildenbrand (Arm) Tested-by: Luke Yang Reviewed-by: Vlastimil Babka (SUSE) Cc: Dev Jain Cc: Jann Horn Cc: Jiri Hladky Cc: Liam Howlett Cc: Davidlohr Bueso Signed-off-by: Andrew Morton

mm: simplify VMA flag tests of excluded flags

2026-04-05T20:53:41+00:00

We have implemented flag mask comparisons of the form: if ((vm_flags & (VM_FOO|VM_BAR|VM_BAZ) == VM_FOO) { ... } Like-for-like in the code using a bitwise-and mask via vma_flags_and() and using vma_flags_same() to ensure the final result equals only the required flag value. This is fine but confusing, make things clearer by instead explicitly excluding undesired flags and including the desired one via tests of the form: if (vma_flags_test(&flags, VMA_FOO_BIT) && !vma_flags_test_any(&flags, VMA_BAR_BIT, VMA_BAZ_BIT)) { ... } Which makes it easier to understand what is going on. No functional change intended. Link: https://lkml.kernel.org/r/d395c5dd837a9864f5efcec42175910afbe3ce73.1774034900.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Suggested-by: Vlastimil Babka (SUSE) Acked-by: Vlastimil Babka (SUSE) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Al Viro Cc: Anton Ivanov Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Chengming Zhou Cc: Christian Borntraeger Cc: Christian Brauner Cc: David Hildenbrand Cc: Dinh Nguyen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Ingo Molnar Cc: Jan Kara Cc: Jann Horn Cc: Johannes Berg Cc: Kees Cook Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Ondrej Mosnacek Cc: Palmer Dabbelt Cc: Paul Moore Cc: Pedro Falcato Cc: Richard Weinberger Cc: Russell King Cc: Stephen Smalley Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: WANG Xuerui Cc: Will Deacon Cc: xu xin Signed-off-by: Andrew Morton

mm/vma: convert __mmap_region() to use vma_flags_t

2026-04-05T20:53:41+00:00

Update the mmap() implementation logic implemented in __mmap_region() and functions invoked by it. The mmap_region() function converts its input vm_flags_t parameter to a vma_flags_t value which it then passes to __mmap_region() which uses the vma_flags_t value consistently from then on. As part of the change, we convert map_deny_write_exec() to using vma_flags_t (it was incorrectly using unsigned long before), and place it in vma.h, as it is only used internal to mm. With this change, we eliminate the legacy is_shared_maywrite_vm_flags() helper function which is now no longer required. We are also able to update the MMAP_STATE() and VMG_MMAP_STATE() macros to use the vma_flags_t value. Finally, we update the VMA tests to reflect the change. Link: https://lkml.kernel.org/r/1fc33a404c962f02da778da100387cc19bd62153.1774034900.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Acked-by: Vlastimil Babka (SUSE) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Al Viro Cc: Anton Ivanov Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Chengming Zhou Cc: Christian Borntraeger Cc: Christian Brauner Cc: David Hildenbrand Cc: Dinh Nguyen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Ingo Molnar Cc: Jan Kara Cc: Jann Horn Cc: Johannes Berg Cc: Kees Cook Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Ondrej Mosnacek Cc: Palmer Dabbelt Cc: Paul Moore Cc: Pedro Falcato Cc: Richard Weinberger Cc: Russell King Cc: Stephen Smalley Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: WANG Xuerui Cc: Will Deacon Cc: xu xin Signed-off-by: Andrew Morton

mm/vma: convert vma_modify_flags[_uffd]() to use vma_flags_t

2026-04-05T20:53:41+00:00

Update the vma_modify_flags() and vma_modify_flags_uffd() functions to accept a vma_flags_t parameter rather than a vm_flags_t one, and propagate the changes as needed to implement this change. Also add vma_flags_reset_once() in replacement of vm_flags_reset_once(). We still need to be careful here because we need to avoid tearing, so maintain the assumption that the first system word set of flags are the only ones that require protection from tearing, and retain this functionality. We can copy the remainder of VMA flags above 64 bits normally. But hopefully by the time that happens, we will have replaced the logic that requires these WRITE_ONCE()'s with something else. We also replace instances of vm_flags_reset() with a simple write of VMA flags. We are no longer perform a number of checks, most notable of all the VMA flags asserts becase: 1. We might be operating on a VMA that is not yet added to the tree. 2. We might be operating on a VMA that is now detached. 3. Really in all but core code, you should be using vma_desc_xxx(). 4. Other VMA fields are manipulated with no such checks. 5. It'd be egregious to have to add variants of flag functions just to account for cases such as the above, especially when we don't do so for other VMA fields. Drivers are the problematic cases and why it was especially important (and also for debug as VMA locks were introduced), the mmap_prepare work is solving this generally. Additionally, we can fairly safely assume by this point the soft dirty flags are being set correctly, so it's reasonable to drop this also. Finally, update the VMA tests to reflect this. Link: https://lkml.kernel.org/r/51afbb2b8c3681003cc7926647e37335d793836e.1774034900.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Acked-by: Vlastimil Babka (SUSE) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Al Viro Cc: Anton Ivanov Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Chengming Zhou Cc: Christian Borntraeger Cc: Christian Brauner Cc: David Hildenbrand Cc: Dinh Nguyen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Ingo Molnar Cc: Jan Kara Cc: Jann Horn Cc: Johannes Berg Cc: Kees Cook Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Ondrej Mosnacek Cc: Palmer Dabbelt Cc: Paul Moore Cc: Pedro Falcato Cc: Richard Weinberger Cc: Russell King Cc: Stephen Smalley Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: WANG Xuerui Cc: Will Deacon Cc: xu xin Signed-off-by: Andrew Morton

mm: convert do_brk_flags() to use vma_flags_t

2026-04-05T20:53:40+00:00

In order to be able to do this, we need to change VM_DATA_DEFAULT_FLAGS and friends and update the architecture-specific definitions also. We then have to update some KSM logic to handle VMA flags, and introduce VMA_STACK_FLAGS to define the vma_flags_t equivalent of VM_STACK_FLAGS. We also introduce two helper functions for use during the time we are converting legacy flags to vma_flags_t values - vma_flags_to_legacy() and legacy_to_vma_flags(). This enables us to iteratively make changes to break these changes up into separate parts. We use these explicitly here to keep VM_STACK_FLAGS around for certain users which need to maintain the legacy vm_flags_t values for the time being. We are no longer able to rely on the simple VM_xxx being set to zero if the feature is not enabled, so in the case of VM_DROPPABLE we introduce VMA_DROPPABLE as the vma_flags_t equivalent, which is set to EMPTY_VMA_FLAGS if the droppable flag is not available. While we're here, we make the description of do_brk_flags() into a kdoc comment, as it almost was already. We use vma_flags_to_legacy() to not need to update the vm_get_page_prot() logic as this time. Note that in create_init_stack_vma() we have to replace the BUILD_BUG_ON() with a VM_WARN_ON_ONCE() as the tested values are no longer build time available. We also update mprotect_fixup() to use VMA flags where possible, though we have to live with a little duplication between vm_flags_t and vma_flags_t values for the time being until further conversions are made. While we're here, update VM_SPECIAL to be defined in terms of VMA_SPECIAL_FLAGS now we have vma_flags_to_legacy(). Finally, we update the VMA tests to reflect these changes. Link: https://lkml.kernel.org/r/d02e3e45d9a33d7904b149f5604904089fd640ae.1774034900.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Acked-by: Paul Moore [SELinux] Acked-by: Vlastimil Babka (SUSE) Cc: Albert Ou Cc: Alexander Gordeev Cc: Alexandre Ghiti Cc: Al Viro Cc: Anton Ivanov Cc: "Borislav Petkov (AMD)" Cc: Catalin Marinas Cc: Chengming Zhou Cc: Christian Borntraeger Cc: Christian Brauner Cc: David Hildenbrand Cc: Dinh Nguyen Cc: Heiko Carstens Cc: "H. Peter Anvin" Cc: Huacai Chen Cc: Ingo Molnar Cc: Jan Kara Cc: Jann Horn Cc: Johannes Berg Cc: Kees Cook Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Ondrej Mosnacek Cc: Palmer Dabbelt Cc: Pedro Falcato Cc: Richard Weinberger Cc: Russell King Cc: Stephen Smalley Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Bogendoerfer Cc: Vasily Gorbik Cc: Vineet Gupta Cc: WANG Xuerui Cc: Will Deacon Cc: xu xin Signed-off-by: Andrew Morton

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

2026-04-05T20:52:57+00:00

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

mm: introduce generic lazy_mmu helpers

2026-01-21T03:24:33+00:00

The implementation of the lazy MMU mode is currently entirely arch-specific; core code directly calls arch helpers: arch_{enter,leave}_lazy_mmu_mode(). We are about to introduce support for nested lazy MMU sections. As things stand we'd have to duplicate that logic in every arch implementing lazy_mmu - adding to a fair amount of logic already duplicated across lazy_mmu implementations. This patch therefore introduces a new generic layer that calls the existing arch_* helpers. Two pair of calls are introduced: * lazy_mmu_mode_enable() ... lazy_mmu_mode_disable() This is the standard case where the mode is enabled for a given block of code by surrounding it with enable() and disable() calls. * lazy_mmu_mode_pause() ... lazy_mmu_mode_resume() This is for situations where the mode is temporarily disabled by first calling pause() and then resume() (e.g. to prevent any batching from occurring in a critical section). The documentation in will be updated in a subsequent patch. No functional change should be introduced at this stage. The implementation of enable()/resume() and disable()/pause() is currently identical, but nesting support will change that. Most of the call sites have been updated using the following Coccinelle script: @@ @@ { ... - arch_enter_lazy_mmu_mode(); + lazy_mmu_mode_enable(); ... - arch_leave_lazy_mmu_mode(); + lazy_mmu_mode_disable(); ... } @@ @@ { ... - arch_leave_lazy_mmu_mode(); + lazy_mmu_mode_pause(); ... - arch_enter_lazy_mmu_mode(); + lazy_mmu_mode_resume(); ... } A couple of notes regarding x86: * Xen is currently the only case where explicit handling is required for lazy MMU when context-switching. This is purely an implementation detail and using the generic lazy_mmu_mode_* functions would cause trouble when nesting support is introduced, because the generic functions must be called from the current task. For that reason we still use arch_leave() and arch_enter() there. * x86 calls arch_flush_lazy_mmu_mode() unconditionally in a few places, but only defines it if PARAVIRT_XXL is selected, and we are removing the fallback in . Add a new fallback definition to to keep things building. Link: https://lkml.kernel.org/r/20251215150323.2218608-8-kevin.brodsky@arm.com Signed-off-by: Kevin Brodsky Acked-by: David Hildenbrand Reviewed-by: Anshuman Khandual Reviewed-by: Yeoreum Yun Cc: Alexander Gordeev Cc: Andreas Larsson Cc: Borislav Betkov Cc: Boris Ostrovsky Cc: Catalin Marinas Cc: Christophe Leroy Cc: David Hildenbrand (Red Hat) Cc: David S. Miller Cc: David Woodhouse Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Jann Horn Cc: Juegren Gross Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Mike Rapoport Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Ritesh Harjani (IBM) Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Thomas Gleinxer Cc: Venkat Rao Bagalkote Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton

mm: eliminate further swapops predicates

2025-11-24T23:08:52+00:00

Having converted so much of the code base to software leaf entries, we can mop up some remaining cases. We replace is_pfn_swap_entry(), pfn_swap_entry_to_page(), is_writable_device_private_entry(), is_device_exclusive_entry(), is_migration_entry(), is_writable_migration_entry(), is_readable_migration_entry(), swp_offset_pfn() and pfn_swap_entry_folio() with softleaf equivalents. No functional change intended. Link: https://lkml.kernel.org/r/956bc9c031604811c0070d2f4bf2f1373f230213.1762812360.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Cc: Alexander Gordeev Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christian Borntraeger Cc: Christian Brauner Cc: Claudio Imbrenda Cc: David Hildenbrand Cc: Dev Jain Cc: Gerald Schaefer Cc: Gregory Price Cc: Heiko Carstens Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Joshua Hahn Cc: Kairui Song Cc: Kemeng Shi Cc: Lance Yang Cc: Leon Romanovsky Cc: Liam Howlett Cc: Mathew Brost Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oscar Salvador Cc: Pasha Tatashin Cc: Peter Xu Cc: Rakie Kim Cc: Rik van Riel Cc: Ryan Roberts Cc: SeongJae Park Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: Wei Xu Cc: xu xin Cc: Yuanchu Xie Cc: Zi Yan Signed-off-by: Andrew Morton

mm: introduce pmd_is_huge() and use where appropriate

2025-11-24T23:08:51+00:00

The leaf entry PMD case is confusing as only migration entries and device private entries are valid at PMD level, not true swap entries. We repeatedly perform checks of the form is_swap_pmd() || pmd_trans_huge() which is itself confusing - it implies that leaf entries at PMD level exist and are different from huge entries. Address this confusion by introduced pmd_is_huge() which checks for either case. Sadly due to header dependency issues (huge_mm.h is included very early on in headers and cannot really rely on much else) we cannot use pmd_is_valid_softleaf() here. However since these are the only valid, handled cases the function is still achieving what it intends to do. We then replace all instances of is_swap_pmd() || pmd_trans_huge() with pmd_is_huge() invocations and adjust logic accordingly to accommodate this. No functional change intended. Link: https://lkml.kernel.org/r/00f79db3b15293cac8f7040a48d69c52d00117e4.1762812360.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes Cc: Alexander Gordeev Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christian Borntraeger Cc: Christian Brauner Cc: Claudio Imbrenda Cc: David Hildenbrand Cc: Dev Jain Cc: Gerald Schaefer Cc: Gregory Price Cc: Heiko Carstens Cc: "Huang, Ying" Cc: Hugh Dickins Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Joshua Hahn Cc: Kairui Song Cc: Kemeng Shi Cc: Lance Yang Cc: Leon Romanovsky Cc: Liam Howlett Cc: Mathew Brost Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oscar Salvador Cc: Pasha Tatashin Cc: Peter Xu Cc: Rakie Kim Cc: Rik van Riel Cc: Ryan Roberts Cc: SeongJae Park Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: Wei Xu Cc: xu xin Cc: Yuanchu Xie Cc: Zi Yan Signed-off-by: Andrew Morton