kernel/linux.git/mm/pgtable-generic.c, branch v6.19.11

mm/huge_memory: add device-private THP support to PMD operations

2025-11-24T23:08:48+00:00

Extend core huge page management functions to handle device-private THP entries. This enables proper handling of large device-private folios in fundamental MM operations. The following functions have been updated: - copy_huge_pmd(): Handle device-private entries during fork/clone - zap_huge_pmd(): Properly free device-private THP during munmap - change_huge_pmd(): Support protection changes on device-private THP - __pte_offset_map(): Add device-private entry awareness Link: https://lkml.kernel.org/r/20251001065707.920170-4-balbirs@nvidia.com Signed-off-by: Matthew Brost Signed-off-by: Balbir Singh Acked-by: Zi Yan Cc: David Hildenbrand Cc: Joshua Hahn Cc: Rakie Kim Cc: Byungchul Park Cc: Gregory Price Cc: Ying Huang Cc: Alistair Popple Cc: Oscar Salvador Cc: Lorenzo Stoakes Cc: Baolin Wang Cc: "Liam R. Howlett" Cc: Nico Pache Cc: Ryan Roberts Cc: Dev Jain Cc: Barry Song Cc: Lyude Paul Cc: Danilo Krummrich Cc: David Airlie Cc: Simona Vetter Cc: Ralph Campbell Cc: Mika Penttilä Cc: Francois Dugast Signed-off-by: Andrew Morton

treewide: include linux/pgalloc.h instead of asm/pgalloc.h

2025-11-17T01:28:25+00:00

For now, including instead of is technically fine unless the .c file calls p*d_populate_kernel() helper functions. But it is a better practice to always include . Include instead of outside arch/. Link: https://lkml.kernel.org/r/20251024113047.119058-3-harry.yoo@oracle.com Signed-off-by: Harry Yoo Acked-by: David Hildenbrand Reviewed-by: Lorenzo Stoakes Reviewed-by: Mike Rapoport (Microsoft) Cc: Liam Howlett Cc: Michal Hocko Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: SeongJae Park Signed-off-by: Andrew Morton

iommu/sva: invalidate stale IOTLB entries for kernel address space

2025-11-17T01:28:18+00:00

Introduce a new IOMMU interface to flush IOTLB paging cache entries for the CPU kernel address space. This interface is invoked from the x86 architecture code that manages combined user and kernel page tables, specifically before any kernel page table page is freed and reused. This addresses the main issue with vfree() which is a common occurrence and can be triggered by unprivileged users. While this resolves the primary problem, it doesn't address some extremely rare case related to memory unplug of memory that was present as reserved memory at boot, which cannot be triggered by unprivileged users. The discussion can be found at the link below. Enable SVA on x86 architecture since the IOMMU can now receive notification to flush the paging cache before freeing the CPU kernel page table pages. Link: https://lkml.kernel.org/r/20251022082635.2462433-9-baolu.lu@linux.intel.com Link: https://lore.kernel.org/linux-iommu/04983c62-3b1d-40d4-93ae-34ca04b827e5@intel.com/ Co-developed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe Signed-off-by: Lu Baolu Suggested-by: Jann Horn Reviewed-by: Jason Gunthorpe Reviewed-by: Vasant Hegde Reviewed-by: Kevin Tian Cc: Alistair Popple Cc: Andy Lutomirski Cc: Borislav Betkov Cc: Dave Hansen Cc: David Hildenbrand Cc: Ingo Molnar Cc: Jean-Philippe Brucker Cc: Joerg Roedel Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport (Microsoft) Cc: Peter Zijlstra Cc: Robin Murohy Cc: Thomas Gleinxer Cc: "Uladzislau Rezki (Sony)" Cc: Vinicius Costa Gomes Cc: Vlastimil Babka Cc: Will Deacon Cc: Yi Lai Signed-off-by: Andrew Morton

mm: introduce deferred freeing for kernel page tables

2025-11-17T01:28:18+00:00

This introduces a conditional asynchronous mechanism, enabled by CONFIG_ASYNC_KERNEL_PGTABLE_FREE. When enabled, this mechanism defers the freeing of pages that are used as page tables for kernel address mappings. These pages are now queued to a work struct instead of being freed immediately. This deferred freeing allows for batch-freeing of page tables, providing a safe context for performing a single expensive operation (TLB flush) for a batch of kernel page tables instead of performing that expensive operation for each page table. Link: https://lkml.kernel.org/r/20251022082635.2462433-8-baolu.lu@linux.intel.com Signed-off-by: Dave Hansen Signed-off-by: Lu Baolu Reviewed-by: Jason Gunthorpe Reviewed-by: Kevin Tian Acked-by: David Hildenbrand Acked-by: Mike Rapoport (Microsoft) Cc: Alistair Popple Cc: Andy Lutomirski Cc: Borislav Betkov Cc: Ingo Molnar Cc: Jann Horn Cc: Jean-Philippe Brucker Cc: Joerg Roedel Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Peter Zijlstra Cc: Robin Murohy Cc: Thomas Gleinxer Cc: "Uladzislau Rezki (Sony)" Cc: Vasant Hegde Cc: Vinicius Costa Gomes Cc: Vlastimil Babka Cc: Will Deacon Cc: Yi Lai Signed-off-by: Andrew Morton

mm: remove redundant pXd_devmap calls

2025-07-10T05:42:17+00:00

DAX was the only thing that created pmd_devmap and pud_devmap entries however it no longer does as DAX pages are now refcounted normally and pXd_trans_huge() returns true for those. Therefore checking both pXd_devmap and pXd_trans_huge() is redundant and the former can be removed without changing behaviour as it will always be false. Link: https://lkml.kernel.org/r/d58f089dc16b7feb7c6728164f37dea65d64a0d3.1750323463.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple Cc: Balbir Singh Cc: Björn Töpel Cc: Björn Töpel Cc: Christoph Hellwig Cc: Chunyan Zhang Cc: Dan Williams Cc: David Hildenbrand Cc: Deepak Gupta Cc: Gerald Schaefer Cc: Inki Dae Cc: Jason Gunthorpe Cc: John Groves Cc: John Hubbard Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Will Deacon Signed-off-by: Andrew Morton

mm: add RCU annotation to pte_offset_map(_lock)

2024-12-19T03:04:43+00:00

RCU lock is taken by ___pte_offset_map() unless it returns NULL. Add this information to its inline callers to avoid sparse warning about context imbalance in pte_unmap(). Link: https://lkml.kernel.org/r/20241210000604.700710-1-oss@malat.biz Signed-off-by: Petr Malat Signed-off-by: Andrew Morton

mm: pgtable: remove pte_offset_map_nolock()

2024-11-06T00:56:29+00:00

Now no users are using the pte_offset_map_nolock(), remove it. Link: https://lkml.kernel.org/r/d04f9bbbcde048fb6ffa6f2bdbc6f9b22d5286f9.1727332572.git.zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Reviewed-by: Muchun Song Acked-by: David Hildenbrand Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Mike Rapoport (Microsoft) Cc: Peter Xu Cc: Ryan Roberts Cc: Vishal Moola (Oracle) Signed-off-by: Andrew Morton

mm: pgtable: introduce pte_offset_map_{ro|rw}_nolock()

2024-11-06T00:56:26+00:00

Patch series "introduce pte_offset_map_{ro|rw}_nolock()", v5. As proposed by David Hildenbrand [1], this series introduces the following two new helper functions to replace pte_offset_map_nolock(). 1. pte_offset_map_ro_nolock() 2. pte_offset_map_rw_nolock() As the name suggests, pte_offset_map_ro_nolock() is used for read-only case. In this case, only read-only operations will be performed on PTE page after the PTL is held. The RCU lock in pte_offset_map_nolock() will ensure that the PTE page will not be freed, and there is no need to worry about whether the pmd entry is modified. Therefore pte_offset_map_ro_nolock() is just a renamed version of pte_offset_map_nolock(). pte_offset_map_rw_nolock() is used for may-write case. In this case, the pte or pmd entry may be modified after the PTL is held, so we need to ensure that the pmd entry has not been modified concurrently. So in addition to the name change, it also outputs the pmdval when successful. The users should make sure the page table is stable like checking pte_same() or checking pmd_same() by using the output pmdval before performing the write operations. This series will convert all pte_offset_map_nolock() into the above two helper functions one by one, and finally completely delete it. This also a preparation for reclaiming the empty user PTE page table pages. This patch (of 13): Currently, the usage of pte_offset_map_nolock() can be divided into the following two cases: 1) After acquiring PTL, only read-only operations are performed on the PTE page. In this case, the RCU lock in pte_offset_map_nolock() will ensure that the PTE page will not be freed, and there is no need to worry about whether the pmd entry is modified. 2) After acquiring PTL, the pte or pmd entries may be modified. At this time, we need to ensure that the pmd entry has not been modified concurrently. To more clearing distinguish between these two cases, this commit introduces two new helper functions to replace pte_offset_map_nolock(). For 1), just rename it to pte_offset_map_ro_nolock(). For 2), in addition to changing the name to pte_offset_map_rw_nolock(), it also outputs the pmdval when successful. It is applicable for may-write cases where any modification operations to the page table may happen after the corresponding spinlock is held afterwards. But the users should make sure the page table is stable like checking pte_same() or checking pmd_same() by using the output pmdval before performing the write operations. Note: "RO" / "RW" expresses the intended semantics, not that the *kmap* will be read-only/read-write protected. Subsequent commits will convert pte_offset_map_nolock() into the above two functions one by one, and finally completely delete it. Link: https://lkml.kernel.org/r/cover.1727332572.git.zhengqi.arch@bytedance.com Link: https://lkml.kernel.org/r/5aeecfa131600a454b1f3a038a1a54282ca3b856.1727332572.git.zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Reviewed-by: Muchun Song Acked-by: David Hildenbrand Cc: Hugh Dickins Cc: Matthew Wilcox Cc: Mike Rapoport (Microsoft) Cc: Peter Xu Cc: Ryan Roberts Cc: Vishal Moola (Oracle) Signed-off-by: Andrew Morton

mm: fix race between __split_huge_pmd_locked() and GUP-fast

2024-05-07T17:37:00+00:00

__split_huge_pmd_locked() can be called for a present THP, devmap or (non-present) migration entry. It calls pmdp_invalidate() unconditionally on the pmdp and only determines if it is present or not based on the returned old pmd. This is a problem for the migration entry case because pmd_mkinvalid(), called by pmdp_invalidate() must only be called for a present pmd. On arm64 at least, pmd_mkinvalid() will mark the pmd such that any future call to pmd_present() will return true. And therefore any lockless pgtable walker could see the migration entry pmd in this state and start interpretting the fields as if it were present, leading to BadThings (TM). GUP-fast appears to be one such lockless pgtable walker. x86 does not suffer the above problem, but instead pmd_mkinvalid() will corrupt the offset field of the swap entry within the swap pte. See link below for discussion of that problem. Fix all of this by only calling pmdp_invalidate() for a present pmd. And for good measure let's add a warning to all implementations of pmdp_invalidate[_ad](). I've manually reviewed all other pmdp_invalidate[_ad]() call sites and believe all others to be conformant. This is a theoretical bug found during code review. I don't have any test case to trigger it in practice. Link: https://lkml.kernel.org/r/20240501143310.1381675-1-ryan.roberts@arm.com Link: https://lore.kernel.org/all/0dd7827a-6334-439a-8fd0-43c98e6af22b@arm.com/ Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path") Signed-off-by: Ryan Roberts Reviewed-by: Zi Yan Reviewed-by: Anshuman Khandual Acked-by: David Hildenbrand Cc: Andreas Larsson Cc: Andy Lutomirski Cc: Aneesh Kumar K.V Cc: Borislav Petkov (AMD) Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christophe Leroy Cc: Dave Hansen Cc: "David S. Miller" Cc: Ingo Molnar Cc: Jonathan Corbet Cc: Mark Rutland Cc: Naveen N. Rao Cc: Nicholas Piggin Cc: Peter Zijlstra Cc: Sven Schnelle Cc: Thomas Gleixner Cc: Will Deacon Cc: Signed-off-by: Andrew Morton

mm/pgtable: notes on pte_offset_map[_lock]()

2023-08-18T17:12:25+00:00

Add a block of comments on pte_offset_map_lock(), pte_offset_map() and pte_offset_map_nolock() to mm/pgtable-generic.c, to help explain them. Link: https://lkml.kernel.org/r/b791c3b0-25c6-a263-d785-d564344eb644@google.com Signed-off-by: Hugh Dickins Cc: Alexander Gordeev Cc: Alistair Popple Cc: Aneesh Kumar K.V Cc: Anshuman Khandual Cc: Axel Rasmussen Cc: Christian Borntraeger Cc: Christophe Leroy Cc: Christoph Hellwig Cc: Claudio Imbrenda Cc: David Hildenbrand Cc: "David S. Miller" Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Huang, Ying Cc: Ira Weiny Cc: Jann Horn Cc: Jason Gunthorpe Cc: Kirill A. Shutemov Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Mel Gorman Cc: Miaohe Lin Cc: Michael Ellerman Cc: Mike Kravetz Cc: Mike Rapoport (IBM) Cc: Minchan Kim Cc: Naoya Horiguchi Cc: Pavel Tatashin Cc: Peter Xu Cc: Peter Zijlstra Cc: Qi Zheng Cc: Ralph Campbell Cc: Russell King Cc: SeongJae Park Cc: Song Liu Cc: Steven Price Cc: Suren Baghdasaryan Cc: Thomas Hellström Cc: Vasily Gorbik Cc: Vishal Moola (Oracle) Cc: Vlastimil Babka Cc: Will Deacon Cc: Yang Shi Cc: Yu Zhao Cc: Zack Rusin Cc: Zi Yan Signed-off-by: Andrew Morton