kernel/arch/riscv/include/asm/pgtable-bits.h, branch linux-rolling-stable

riscv: mm: add userfaultfd write-protect support

2025-11-24T23:08:55Z

The Svrsw60t59b extension allows to free the PTE reserved bits 60 and 59 for software, this patch uses bit 60 for uffd-wp tracking Additionally for tracking the uffd-wp state as a PTE swap bit, we borrow bit 4 which is not involved into swap entry computation. Link: https://lkml.kernel.org/r/20251113072806.795029-6-zhangchunyan@iscas.ac.cn Signed-off-by: Chunyan Zhang Cc: Albert Ou Cc: Alexandre Ghiti Cc: Alexandre Ghiti Cc: Al Viro Cc: Andrew Jones Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Christian Brauner Cc: Conor Dooley Cc: Conor Dooley Cc: David Hildenbrand Cc: Deepak Gupta Cc: Jan Kara Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Peter Xu Cc: Rob Herring Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Yuanchu Xie Signed-off-by: Andrew Morton

riscv: mm: add soft-dirty page tracking support

2025-11-24T23:08:55Z

The Svrsw60t59b extension allows to free the PTE reserved bits 60 and 59 for software, this patch uses bit 59 for soft-dirty. To add swap PTE soft-dirty tracking, we borrow bit 3 which is available for swap PTEs on RISC-V systems. Link: https://lkml.kernel.org/r/20251113072806.795029-5-zhangchunyan@iscas.ac.cn Signed-off-by: Chunyan Zhang Reviewed-by: Deepak Gupta Cc: Albert Ou Cc: Alexandre Ghiti Cc: Alexandre Ghiti Cc: Al Viro Cc: Andrew Jones Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Christian Brauner Cc: Conor Dooley Cc: Conor Dooley Cc: David Hildenbrand Cc: Jan Kara Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Peter Xu Cc: Rob Herring Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Yuanchu Xie Signed-off-by: Andrew Morton

mm: remove devmap related functions and page table bits

2025-07-10T05:42:18Z

Now that DAX and all other reference counts to ZONE_DEVICE pages are managed normally there is no need for the special devmap PTE/PMD/PUD page table bits. So drop all references to these, freeing up a software defined page table bit on architectures supporting it. Link: https://lkml.kernel.org/r/6389398c32cc9daa3dfcaa9f79c7972525d310ce.1750323463.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple Acked-by: Will Deacon # arm64 Acked-by: David Hildenbrand Suggested-by: Chunyan Zhang Reviewed-by: Björn Töpel Reviewed-by: Jason Gunthorpe Cc: Balbir Singh Cc: Björn Töpel Cc: Christoph Hellwig Cc: Dan Williams Cc: Deepak Gupta Cc: Gerald Schaefer Cc: Inki Dae Cc: John Groves Cc: John Hubbard Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

riscv: mm: Add support for ZONE_DEVICE

2024-06-26T15:42:46Z

ZONE_DEVICE pages need DEVMAP PTEs support to function (ARCH_HAS_PTE_DEVMAP). Claim another RSW (reserved for software) bit in the PTE for DEVMAP mark, add the corresponding helpers, and enable ARCH_HAS_PTE_DEVMAP for riscv64. Reviewed-by: Alexandre Ghiti Signed-off-by: Björn Töpel Link: https://lore.kernel.org/r/20240605114100.315918-11-bjorn@kernel.org Signed-off-by: Palmer Dabbelt

riscv: Improve PTDUMP to show RSW with non-zero value

2023-11-05T17:41:53Z

RSW field can be used to encode 2 bits of software defined information. Currently, PTDUMP only prints "RSW" when its value is 1 or 3. To fix this issue and improve the debugging experience with PTDUMP, we redefine _PAGE_SPECIAL to its original value and use _PAGE_SOFT as the RSW mask, allow it to print the RSW with any non-zero value. This patch also removes the val from the struct prot_bits as it is no longer needed. Signed-off-by: Yu Chien Peter Lin Reviewed-by: Alexandre Ghiti Tested-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20230921025022.3989723-2-peterlin@andestech.com Signed-off-by: Palmer Dabbelt

riscv/mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE

2023-02-03T06:33:09Z

Let's support __HAVE_ARCH_PTE_SWP_EXCLUSIVE by stealing one bit from the offset. This reduces the maximum swap space per file: on 32bit to 16 GiB (was 32 GiB). Note that this bit does not conflict with swap PMDs and could also be used in swap PMD context later. While at it, mask the type in __swp_entry(). Link: https://lkml.kernel.org/r/20230113171026.582290-20-david@redhat.com Signed-off-by: David Hildenbrand Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Signed-off-by: Andrew Morton

riscv: add RISC-V Svpbmt extension support

2022-05-12T04:36:33Z

Svpbmt (the S should be capitalized) is the "Supervisor-mode: page-based memory types" extension that specifies attributes for cacheability, idempotency and ordering. The relevant settings are done in special bits in PTEs: Here is the svpbmt PTE format: | 63 | 62-61 | 60-8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 N MT RSW D A G U X W R V ^ Of the Reserved bits [63:54] in a leaf PTE, the high bit is already allocated (as the N bit), so bits [62:61] are used as the MT (aka MemType) field. This field specifies one of three memory types that are close equivalents (or equivalent in effect) to the three main x86 and ARMv8 memory types - as shown in the following table. RISC-V Encoding & MemType RISC-V Description ---------- ------------------------------------------------ 00 - PMA Normal Cacheable, No change to implied PMA memory type 01 - NC Non-cacheable, idempotent, weakly-ordered Main Memory 10 - IO Non-cacheable, non-idempotent, strongly-ordered I/O memory 11 - Rsvd Reserved for future standard use As the extension will not be present on all implementations, implement a method to handle cpufeatures via alternatives to not incur runtime penalties on cpu variants not supporting specific extensions and patch relevant code parts at runtime. Co-developed-by: Wei Fu Signed-off-by: Wei Fu Co-developed-by: Liu Shaohua Signed-off-by: Liu Shaohua Co-developed-by: Guo Ren Signed-off-by: Guo Ren [moved to use the alternatives mechanism] Signed-off-by: Heiko Stuebner Reviewed-by: Philipp Tomsich Link: https://lore.kernel.org/r/20220511192921.2223629-10-heiko@sntech.de Signed-off-by: Palmer Dabbelt

riscv: Fix accessing pfn bits in PTEs for non-32bit variants

2022-05-12T04:36:32Z

On rv32 the PFN part of PTEs is defined to use bits [xlen-1:10] while on rv64 it is defined to use bits [53:10], leaving [63:54] as reserved. With upcoming optional extensions like svpbmt these previously reserved bits will get used so simply right-shifting the PTE to get the PFN won't be enough. So introduce a _PAGE_PFN_MASK constant to mask the correct bits for both rv32 and rv64 before shifting. Signed-off-by: Heiko Stuebner Reviewed-by: Philipp Tomsich Link: https://lore.kernel.org/r/20220511192921.2223629-9-heiko@sntech.de Signed-off-by: Palmer Dabbelt

riscv/mm: Adjust PAGE_PROT_NONE to comply with THP semantics

2022-01-07T23:54:24Z

This is a preparation for enabling THP migration. As the commit b65399f6111b("arm64/mm: Change THP helpers to comply with generic MM semantics") mentioned, pmd_present() and pmd_trans_huge() are expected to behave in the following manner: ------------------------------------------------------------------------- | PMD states | pmd_present | pmd_trans_huge | ------------------------------------------------------------------------- | Mapped | Yes | Yes | ------------------------------------------------------------------------- | Splitting | Yes | Yes | ------------------------------------------------------------------------- | Migration/Swap | No | No | ------------------------------------------------------------------------- At present the PROT_NONE bit reuses the READ bit could not comply with above semantics with two problems: 1. When splitting a PMD THP, PMD is first invalidated with pmdp_invalidate()->pmd_mkinvalid(), which clears the PRESENT bit and PROT_NONE bit/READ bit, if the PMD is read-only, then the PAGE_LEAF property is also cleared, which results in pmd_present() return false. 2. When migrating, the swap entry only clear the PRESENT bit and PROT_NONE bit/READ bit, the W/X bit may be set, so _PAGE_LEAF may be true which results in pmd_present() return true. Solution: Adjust PROT_NONE bit from READ to GLOBAL bit can satisfy the above rules: 1. GLOBAL bit has no other meanings, not like the R/W/X bit, which is also relative with _PAGE_LEAF property. 2. GLOBAL bit is at bit 5, making swap entry start from bit 6, bit 0-5 are zero, which means the PRESENT, PROT_NONE, and PAGE_LEAF are all false, then the pmd_present() and pmd_trans_huge() return false when in migration/swap. Signed-off-by: Nanyong Sun Signed-off-by: Palmer Dabbelt

riscv: mm: add _PAGE_LEAF macro

2021-05-22T17:19:29Z

In riscv, a page table entry is leaf when any bit of read, write, or execute bit is set. So add a macro:_PAGE_LEAF instead of (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC), which is frequently used to determine if it is a leaf page. This make code easier to read, without any functional change. Signed-off-by: Nanyong Sun Signed-off-by: Palmer Dabbelt