[PATCH V12 0/5] riscv: mm: Add soft-dirty and uffd-wp support

[PATCH V12 0/5] riscv: mm: Add soft-dirty and uffd-wp support

[Chunyan Zhang]

This patchset adds support for Svrsw60t59b [1] extension which is ratified now,
also add soft dirty and userfaultfd write protect tracking for RISC-V.

The patches 1 and 2 add macros to allow architectures to define their own checks
if the soft-dirty / uffd_wp PTE bits are available, in other words for RISC-V,
the Svrsw60t59b extension is supported on which device the kernel is running.

This patchset has been tested with kselftest mm suite in which soft-dirty, 
madv_populate, test_unmerge_uffd_wp, and uffd-unit-tests run and pass,
and no regressions are observed in any of the other tests.

This patchset applies on top of v6.17-rc6.

[1] https://github.com/riscv-non-isa/riscv-iommu/pull/543

V12:
- Rename the macro API to pgtable_supports_soft_dirty/uffd_wp();
- Add changes for setting VM_SOFTDIRTY flags conditionally;
- Drop changes to show_smap_vma_flags();
- Drop CONFIG_MEM_SOFT_DIRTY compile condition of clear_soft_dirty() and clear_soft_dirty_pmd();
- Fix typos;
- Add uffd_supports_wp_marker() and drop some ifdef CONFIG_PTE_MARKER_UFFD_WP.

V11: https://lore.kernel.org/all/20250911095602.1130290-1-zhangchunyan@iscas.ac.cn/
- Rename the macro API to pgtable_*_supported() since we also have PMD support;
- Change the default implementations of two macros, make CONFIG_MEM_SOFT_DIRTY or
  CONFIG_HAVE_ARCH_USERFAULTFD_WP part of the macros;
- Correct the order of insertion of RISCV_ISA_EXT_SVRSW60T59B;
- Rephrase some comments.

V10: https://lore.kernel.org/all/20250909095611.803898-1-zhangchunyan@iscas.ac.cn/
- Fixed the issue reported by kernel test irobot <lkp@intel.com>.

V9: https://lore.kernel.org/all/20250905103651.489197-1-zhangchunyan@iscas.ac.cn/
- Add pte_soft_dirty/uffd_wp_available() API to allow dynamically checking
  if the PTE bit is available for the platform on which the kernel is running.

V8: https://lore.kernel.org/all/20250619065232.1786470-1-zhangchunyan@iscas.ac.cn/)
- Rebase on v6.16-rc1;
- Add dependencies to MMU && 64BIT for RISCV_ISA_SVRSW60T59B;
- Use 'Svrsw60t59b' instead of 'SVRSW60T59B' in Kconfig help paragraph;
- Add Alex's Reviewed-by tag in patch 1.

V7: https://lore.kernel.org/all/20250409095320.224100-1-zhangchunyan@iscas.ac.cn/
- Add Svrsw60t59b [1] extension support;
- Have soft-dirty and uffd-wp depending on the Svrsw60t59b extension to
  avoid crashes for the hardware which don't have this extension.

V6: https://lore.kernel.org/all/20250408084301.68186-1-zhangchunyan@iscas.ac.cn/
- Changes to use bits 59-60 which are supported by extension Svrsw60t59b
  for soft dirty and userfaultfd write protect tracking.

V5: https://lore.kernel.org/all/20241113095833.1805746-1-zhangchunyan@iscas.ac.cn/
- Fixed typos and corrected some words in Kconfig and commit message;
- Removed pte_wrprotect() from pte_swp_mkuffd_wp(), this is a copy-paste
  error;
- Added Alex's Reviewed-by tag in patch 2.

V4: https://lore.kernel.org/all/20240830011101.3189522-1-zhangchunyan@iscas.ac.cn/
- Added bit(4) descriptions into "Format of swap PTE".

V3: https://lore.kernel.org/all/20240805095243.44809-1-zhangchunyan@iscas.ac.cn/
- Fixed the issue reported by kernel test irobot <lkp@intel.com>.

V2: https://lore.kernel.org/all/20240731040444.3384790-1-zhangchunyan@iscas.ac.cn/
- Add uffd-wp supported;
- Make soft-dirty uffd-wp and devmap mutually exclusive which all use
  the same PTE bit;
- Add test results of CRIU in the cover-letter.

Chunyan Zhang (5):
  mm: softdirty: Add pgtable_supports_soft_dirty()
  mm: userfaultfd: Add pgtable_supports_uffd_wp()
  riscv: Add RISC-V Svrsw60t59b extension support
  riscv: mm: Add soft-dirty page tracking support
  riscv: mm: Add userfaultfd write-protect support

 arch/riscv/Kconfig                    |  16 +++
 arch/riscv/include/asm/hwcap.h        |   1 +
 arch/riscv/include/asm/pgtable-bits.h |  37 +++++++
 arch/riscv/include/asm/pgtable.h      | 143 +++++++++++++++++++++++++-
 arch/riscv/kernel/cpufeature.c        |   1 +
 fs/proc/task_mmu.c                    |  15 ++-
 fs/userfaultfd.c                      |  22 ++--
 include/asm-generic/pgtable_uffd.h    |  17 +++
 include/linux/mm.h                    |   3 +
 include/linux/mm_inline.h             |  10 +-
 include/linux/pgtable.h               |  12 +++
 include/linux/userfaultfd_k.h         |  27 +++--
 mm/debug_vm_pgtable.c                 |  10 +-
 mm/huge_memory.c                      |  13 +--
 mm/internal.h                         |   2 +-
 mm/memory.c                           |   6 +-
 mm/mmap.c                             |   6 +-
 mm/mremap.c                           |  13 +--
 mm/userfaultfd.c                      |  10 +-
 mm/vma.c                              |   6 +-
 mm/vma_exec.c                         |   5 +-
 21 files changed, 306 insertions(+), 69 deletions(-)

-- 
2.34.1

[PATCH V12 1/5] mm: softdirty: Add pgtable_supports_soft_dirty()

[Chunyan Zhang]

Some platforms can customize the PTE PMD entry soft-dirty bit making it
unavailable even if the architecture provides the resource.

Add an API which architectures can define their specific implementations
to detect if soft-dirty bit is available on which device the kernel is
running.

Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
---
 fs/proc/task_mmu.c      | 15 ++++++---------
 include/linux/mm.h      |  3 +++
 include/linux/pgtable.h | 12 ++++++++++++
 mm/debug_vm_pgtable.c   | 10 +++++-----
 mm/huge_memory.c        | 13 +++++++------
 mm/internal.h           |  2 +-
 mm/mmap.c               |  6 ++++--
 mm/mremap.c             | 13 +++++++------
 mm/userfaultfd.c        | 10 ++++------
 mm/vma.c                |  6 ++++--
 mm/vma_exec.c           |  5 ++++-
 11 files changed, 57 insertions(+), 38 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 29cca0e6d0ff..ebce4e1b3b32 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1510,8 +1510,6 @@ struct clear_refs_private {
 	enum clear_refs_types type;
 };
 
-#ifdef CONFIG_MEM_SOFT_DIRTY
-
 static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
 {
 	struct folio *folio;
@@ -1531,6 +1529,8 @@ static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr,
 static inline void clear_soft_dirty(struct vm_area_struct *vma,
 		unsigned long addr, pte_t *pte)
 {
+	if (!pgtable_supports_soft_dirty())
+		return;
 	/*
 	 * The soft-dirty tracker uses #PF-s to catch writes
 	 * to pages, so write-protect the pte as well. See the
@@ -1553,19 +1553,16 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
 		set_pte_at(vma->vm_mm, addr, pte, ptent);
 	}
 }
-#else
-static inline void clear_soft_dirty(struct vm_area_struct *vma,
-		unsigned long addr, pte_t *pte)
-{
-}
-#endif
 
-#if defined(CONFIG_MEM_SOFT_DIRTY) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
 static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
 		unsigned long addr, pmd_t *pmdp)
 {
 	pmd_t old, pmd = *pmdp;
 
+	if (!pgtable_supports_soft_dirty())
+		return;
+
 	if (pmd_present(pmd)) {
 		/* See comment in change_huge_pmd() */
 		old = pmdp_invalidate(vma, addr, pmdp);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1ae97a0b8ec7..260b6c7c88fa 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -718,6 +718,7 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 static inline void vm_flags_init(struct vm_area_struct *vma,
 				 vm_flags_t flags)
 {
+	VM_WARN_ON_ONCE(!pgtable_supports_soft_dirty() && (flags & VM_SOFTDIRTY));
 	ACCESS_PRIVATE(vma, __vm_flags) = flags;
 }
 
@@ -736,6 +737,7 @@ static inline void vm_flags_reset(struct vm_area_struct *vma,
 static inline void vm_flags_reset_once(struct vm_area_struct *vma,
 				       vm_flags_t flags)
 {
+	VM_WARN_ON_ONCE(!pgtable_supports_soft_dirty() && (flags & VM_SOFTDIRTY));
 	vma_assert_write_locked(vma);
 	WRITE_ONCE(ACCESS_PRIVATE(vma, __vm_flags), flags);
 }
@@ -743,6 +745,7 @@ static inline void vm_flags_reset_once(struct vm_area_struct *vma,
 static inline void vm_flags_set(struct vm_area_struct *vma,
 				vm_flags_t flags)
 {
+	VM_WARN_ON_ONCE(!pgtable_supports_soft_dirty() && (flags & VM_SOFTDIRTY));
 	vma_start_write(vma);
 	ACCESS_PRIVATE(vma, __vm_flags) |= flags;
 }
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 2b80fd456c8b..18269214ee5c 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1553,6 +1553,18 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
 #define arch_start_context_switch(prev)	do {} while (0)
 #endif
 
+/*
+ * Some platforms can customize the PTE soft-dirty bit making it unavailable
+ * even if the architecture provides the resource.
+ * Adding this API allows architectures to add their own checks for the
+ * devices on which the kernel is running.
+ * Note: When overriding it, please make sure the CONFIG_MEM_SOFT_DIRTY
+ * is part of this macro.
+ */
+#ifndef pgtable_supports_soft_dirty
+#define pgtable_supports_soft_dirty()	IS_ENABLED(CONFIG_MEM_SOFT_DIRTY)
+#endif
+
 #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
 #ifndef CONFIG_ARCH_ENABLE_THP_MIGRATION
 static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 830107b6dd08..6a5b226bda28 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -690,7 +690,7 @@ static void __init pte_soft_dirty_tests(struct pgtable_debug_args *args)
 {
 	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot);
 
-	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
+	if (!pgtable_supports_soft_dirty())
 		return;
 
 	pr_debug("Validating PTE soft dirty\n");
@@ -702,7 +702,7 @@ static void __init pte_swap_soft_dirty_tests(struct pgtable_debug_args *args)
 {
 	pte_t pte;
 
-	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
+	if (!pgtable_supports_soft_dirty())
 		return;
 
 	pr_debug("Validating PTE swap soft dirty\n");
@@ -718,7 +718,7 @@ static void __init pmd_soft_dirty_tests(struct pgtable_debug_args *args)
 {
 	pmd_t pmd;
 
-	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
+	if (!pgtable_supports_soft_dirty())
 		return;
 
 	if (!has_transparent_hugepage())
@@ -734,8 +734,8 @@ static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args)
 {
 	pmd_t pmd;
 
-	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) ||
-		!IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION))
+	if (!pgtable_supports_soft_dirty() ||
+	    !IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION))
 		return;
 
 	if (!has_transparent_hugepage())
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9c38a95e9f09..7424b1b5aa1e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2271,12 +2271,13 @@ static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
 
 static pmd_t move_soft_dirty_pmd(pmd_t pmd)
 {
-#ifdef CONFIG_MEM_SOFT_DIRTY
-	if (unlikely(is_pmd_migration_entry(pmd)))
-		pmd = pmd_swp_mksoft_dirty(pmd);
-	else if (pmd_present(pmd))
-		pmd = pmd_mksoft_dirty(pmd);
-#endif
+	if (pgtable_supports_soft_dirty()) {
+		if (unlikely(is_pmd_migration_entry(pmd)))
+			pmd = pmd_swp_mksoft_dirty(pmd);
+		else if (pmd_present(pmd))
+			pmd = pmd_mksoft_dirty(pmd);
+	}
+
 	return pmd;
 }
 
diff --git a/mm/internal.h b/mm/internal.h
index 45b725c3dc03..805140b2ce8b 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1538,7 +1538,7 @@ static inline bool vma_soft_dirty_enabled(struct vm_area_struct *vma)
 	 * VM_SOFTDIRTY is defined as 0x0, then !(vm_flags & VM_SOFTDIRTY)
 	 * will be constantly true.
 	 */
-	if (!IS_ENABLED(CONFIG_MEM_SOFT_DIRTY))
+	if (!pgtable_supports_soft_dirty())
 		return false;
 
 	/*
diff --git a/mm/mmap.c b/mm/mmap.c
index 7306253cc3b5..e091532e5e0b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1451,8 +1451,10 @@ static struct vm_area_struct *__install_special_mapping(
 		return ERR_PTR(-ENOMEM);
 
 	vma_set_range(vma, addr, addr + len, 0);
-	vm_flags_init(vma, (vm_flags | mm->def_flags |
-		      VM_DONTEXPAND | VM_SOFTDIRTY) & ~VM_LOCKED_MASK);
+	vm_flags |= mm->def_flags | VM_DONTEXPAND;
+	if (pgtable_supports_soft_dirty())
+		vm_flags |= VM_SOFTDIRTY;
+	vm_flags_init(vma, vm_flags & ~VM_LOCKED_MASK);
 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 
 	vma->vm_ops = ops;
diff --git a/mm/mremap.c b/mm/mremap.c
index 35de0a7b910e..35a135cd149a 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -162,12 +162,13 @@ static pte_t move_soft_dirty_pte(pte_t pte)
 	 * Set soft dirty bit so we can notice
 	 * in userspace the ptes were moved.
 	 */
-#ifdef CONFIG_MEM_SOFT_DIRTY
-	if (pte_present(pte))
-		pte = pte_mksoft_dirty(pte);
-	else if (is_swap_pte(pte))
-		pte = pte_swp_mksoft_dirty(pte);
-#endif
+	if (pgtable_supports_soft_dirty()) {
+		if (pte_present(pte))
+			pte = pte_mksoft_dirty(pte);
+		else if (is_swap_pte(pte))
+			pte = pte_swp_mksoft_dirty(pte);
+	}
+
 	return pte;
 }
 
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index aefdf3a812a1..6ff7d4cd8b9a 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1065,9 +1065,8 @@ static int move_present_pte(struct mm_struct *mm,
 
 	orig_dst_pte = folio_mk_pte(src_folio, dst_vma->vm_page_prot);
 	/* Set soft dirty bit so userspace can notice the pte was moved */
-#ifdef CONFIG_MEM_SOFT_DIRTY
-	orig_dst_pte = pte_mksoft_dirty(orig_dst_pte);
-#endif
+	if (pgtable_supports_soft_dirty())
+		orig_dst_pte = pte_mksoft_dirty(orig_dst_pte);
 	if (pte_dirty(orig_src_pte))
 		orig_dst_pte = pte_mkdirty(orig_dst_pte);
 	orig_dst_pte = pte_mkwrite(orig_dst_pte, dst_vma);
@@ -1134,9 +1133,8 @@ static int move_swap_pte(struct mm_struct *mm, struct vm_area_struct *dst_vma,
 	}
 
 	orig_src_pte = ptep_get_and_clear(mm, src_addr, src_pte);
-#ifdef CONFIG_MEM_SOFT_DIRTY
-	orig_src_pte = pte_swp_mksoft_dirty(orig_src_pte);
-#endif
+	if (pgtable_supports_soft_dirty())
+		orig_src_pte = pte_swp_mksoft_dirty(orig_src_pte);
 	set_pte_at(mm, dst_addr, dst_pte, orig_src_pte);
 	double_pt_unlock(dst_ptl, src_ptl);
 
diff --git a/mm/vma.c b/mm/vma.c
index 3b12c7579831..a2292a7253b8 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -2551,7 +2551,8 @@ static void __mmap_complete(struct mmap_state *map, struct vm_area_struct *vma)
 	 * then new mapped in-place (which must be aimed as
 	 * a completely new data area).
 	 */
-	vm_flags_set(vma, VM_SOFTDIRTY);
+	if (pgtable_supports_soft_dirty())
+		vm_flags_set(vma, VM_SOFTDIRTY);
 
 	vma_set_page_prot(vma);
 }
@@ -2818,7 +2819,8 @@ int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
 	mm->data_vm += len >> PAGE_SHIFT;
 	if (vm_flags & VM_LOCKED)
 		mm->locked_vm += (len >> PAGE_SHIFT);
-	vm_flags_set(vma, VM_SOFTDIRTY);
+	if (pgtable_supports_soft_dirty())
+		vm_flags_set(vma, VM_SOFTDIRTY);
 	return 0;
 
 mas_store_fail:
diff --git a/mm/vma_exec.c b/mm/vma_exec.c
index 922ee51747a6..a822fb73f4e2 100644
--- a/mm/vma_exec.c
+++ b/mm/vma_exec.c
@@ -107,6 +107,7 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift)
 int create_init_stack_vma(struct mm_struct *mm, struct vm_area_struct **vmap,
 			  unsigned long *top_mem_p)
 {
+	unsigned long flags  = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 	int err;
 	struct vm_area_struct *vma = vm_area_alloc(mm);
 
@@ -137,7 +138,9 @@ int create_init_stack_vma(struct mm_struct *mm, struct vm_area_struct **vmap,
 	BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 	vma->vm_end = STACK_TOP_MAX;
 	vma->vm_start = vma->vm_end - PAGE_SIZE;
-	vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP);
+	if (pgtable_supports_soft_dirty())
+		flags |= VM_SOFTDIRTY;
+	vm_flags_init(vma, flags);
 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 
 	err = insert_vm_struct(mm, vma);
-- 
2.34.1

[PATCH V12 2/5] mm: userfaultfd: Add pgtable_supports_uffd_wp()

[Chunyan Zhang]

Some platforms can customize the PTE/PMD entry uffd-wp bit making
it unavailable even if the architecture provides the resource.
This patch adds a macro API that allows architectures to define their
specific implementations to check if the uffd-wp bit is available
on which device the kernel is running.

Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
---
 fs/userfaultfd.c                   | 22 +++++++++++-----------
 include/asm-generic/pgtable_uffd.h | 17 +++++++++++++++++
 include/linux/mm_inline.h          | 10 ++++++++--
 include/linux/userfaultfd_k.h      | 27 +++++++++++++--------------
 mm/memory.c                        |  6 ++++--
 5 files changed, 53 insertions(+), 29 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 54c6cc7fe9c6..e41736ffa202 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1270,9 +1270,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 	if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
 		vm_flags |= VM_UFFD_MISSING;
 	if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
-		goto out;
-#endif
+		if (!pgtable_supports_uffd_wp())
+			goto out;
+
 		vm_flags |= VM_UFFD_WP;
 	}
 	if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MINOR) {
@@ -1980,14 +1980,14 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx,
 	uffdio_api.features &=
 		~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM);
 #endif
-#ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
-	uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
-#endif
-#ifndef CONFIG_PTE_MARKER_UFFD_WP
-	uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
-	uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
-	uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
-#endif
+	if (!pgtable_supports_uffd_wp())
+		uffdio_api.features &= ~UFFD_FEATURE_PAGEFAULT_FLAG_WP;
+
+	if (!uffd_supports_wp_marker()) {
+		uffdio_api.features &= ~UFFD_FEATURE_WP_HUGETLBFS_SHMEM;
+		uffdio_api.features &= ~UFFD_FEATURE_WP_UNPOPULATED;
+		uffdio_api.features &= ~UFFD_FEATURE_WP_ASYNC;
+	}
 
 	ret = -EINVAL;
 	if (features & ~uffdio_api.features)
diff --git a/include/asm-generic/pgtable_uffd.h b/include/asm-generic/pgtable_uffd.h
index 828966d4c281..200da65262a8 100644
--- a/include/asm-generic/pgtable_uffd.h
+++ b/include/asm-generic/pgtable_uffd.h
@@ -1,6 +1,23 @@
 #ifndef _ASM_GENERIC_PGTABLE_UFFD_H
 #define _ASM_GENERIC_PGTABLE_UFFD_H
 
+/*
+ * Some platforms can customize the uffd-wp bit, making it unavailable
+ * even if the architecture provides the resource.
+ * Adding this API allows architectures to add their own checks for the
+ * devices on which the kernel is running.
+ * Note: When overriding it, please make sure the
+ * CONFIG_HAVE_ARCH_USERFAULTFD_WP is part of this macro.
+ */
+#ifndef pgtable_supports_uffd_wp
+#define pgtable_supports_uffd_wp()	IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP)
+#endif
+
+static __always_inline bool uffd_supports_wp_marker(void)
+{
+	return pgtable_supports_uffd_wp() && IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP);
+}
+
 #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
 static __always_inline int pte_uffd_wp(pte_t pte)
 {
diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index 89b518ff097e..d6526a7f034b 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -570,9 +570,15 @@ static inline bool
 pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
 			      pte_t *pte, pte_t pteval)
 {
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
 	bool arm_uffd_pte = false;
 
+	/*
+	 * Some platforms can customize the PTE uffd-wp bit, making it unavailable
+	 * even if the architecture allows providing the PTE resource.
+	 */
+	if (!uffd_supports_wp_marker())
+		return false;
+
 	/* The current status of the pte should be "cleared" before calling */
 	WARN_ON_ONCE(!pte_none(ptep_get(pte)));
 
@@ -601,7 +607,7 @@ pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
 			   make_pte_marker(PTE_MARKER_UFFD_WP));
 		return true;
 	}
-#endif
+
 	return false;
 }
 
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index c0e716aec26a..c19435863076 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -228,15 +228,14 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma,
 	if (wp_async && (vm_flags == VM_UFFD_WP))
 		return true;
 
-#ifndef CONFIG_PTE_MARKER_UFFD_WP
 	/*
 	 * If user requested uffd-wp but not enabled pte markers for
 	 * uffd-wp, then shmem & hugetlbfs are not supported but only
 	 * anonymous.
 	 */
-	if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
+	if (!uffd_supports_wp_marker() && (vm_flags & VM_UFFD_WP) &&
+	    !vma_is_anonymous(vma))
 		return false;
-#endif
 
 	/* By default, allow any of anon|shmem|hugetlb */
 	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
@@ -436,28 +435,26 @@ static inline bool userfaultfd_wp_use_markers(struct vm_area_struct *vma)
 
 static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
 {
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
+	if (!uffd_supports_wp_marker())
+		return false;
+
 	return is_pte_marker_entry(entry) &&
-	    (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
-#else
-	return false;
-#endif
+	       (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
 }
 
 static inline bool pte_marker_uffd_wp(pte_t pte)
 {
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
 	swp_entry_t entry;
 
+	if (!uffd_supports_wp_marker())
+		return false;
+
 	if (!is_swap_pte(pte))
 		return false;
 
 	entry = pte_to_swp_entry(pte);
 
 	return pte_marker_entry_uffd_wp(entry);
-#else
-	return false;
-#endif
 }
 
 /*
@@ -466,7 +463,9 @@ static inline bool pte_marker_uffd_wp(pte_t pte)
  */
 static inline bool pte_swp_uffd_wp_any(pte_t pte)
 {
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
+	if (!uffd_supports_wp_marker())
+		return false;
+
 	if (!is_swap_pte(pte))
 		return false;
 
@@ -475,7 +474,7 @@ static inline bool pte_swp_uffd_wp_any(pte_t pte)
 
 	if (pte_marker_uffd_wp(pte))
 		return true;
-#endif
+
 	return false;
 }
 
diff --git a/mm/memory.c b/mm/memory.c
index 0ba4f6b71847..607e14177412 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1465,7 +1465,9 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
 {
 	bool was_installed = false;
 
-#ifdef CONFIG_PTE_MARKER_UFFD_WP
+	if (!uffd_supports_wp_marker())
+		return false;
+
 	/* Zap on anonymous always means dropping everything */
 	if (vma_is_anonymous(vma))
 		return false;
@@ -1482,7 +1484,7 @@ zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
 		pte++;
 		addr += PAGE_SIZE;
 	}
-#endif
+
 	return was_installed;
 }
 
-- 
2.34.1

[PATCH V12 3/5] riscv: Add RISC-V Svrsw60t59b extension support

[Chunyan Zhang]

The Svrsw60t59b extension allows to free the PTE reserved bits 60
and 59 for software to use.

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
---
 arch/riscv/Kconfig             | 14 ++++++++++++++
 arch/riscv/include/asm/hwcap.h |  1 +
 arch/riscv/kernel/cpufeature.c |  1 +
 3 files changed, 16 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 51dcd8eaa243..e1b6a95952c4 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -862,6 +862,20 @@ config RISCV_ISA_ZICBOP
 
 	  If you don't know what to do here, say Y.
 
+config RISCV_ISA_SVRSW60T59B
+	bool "Svrsw60t59b extension support for using PTE bits 60 and 59"
+	depends on MMU && 64BIT
+	depends on RISCV_ALTERNATIVE
+	default y
+	help
+	  Adds support to dynamically detect the presence of the Svrsw60t59b
+	  extension and enable its usage.
+
+	  The Svrsw60t59b extension allows to free the PTE reserved bits 60
+	  and 59 for software to use.
+
+	  If you don't know what to do here, say Y.
+
 config TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI
 	def_bool y
 	# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index affd63e11b0a..f98fcb5c17d5 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -106,6 +106,7 @@
 #define RISCV_ISA_EXT_ZAAMO		97
 #define RISCV_ISA_EXT_ZALRSC		98
 #define RISCV_ISA_EXT_ZICBOP		99
+#define RISCV_ISA_EXT_SVRSW60T59B	100
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 743d53415572..2ba71d2d3fa3 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -539,6 +539,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
 	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
 	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
+	__RISCV_ISA_EXT_DATA(svrsw60t59b, RISCV_ISA_EXT_SVRSW60T59B),
 	__RISCV_ISA_EXT_DATA(svvptc, RISCV_ISA_EXT_SVVPTC),
 };
 
-- 
2.34.1

[PATCH V12 4/5] riscv: mm: Add soft-dirty page tracking support

[Chunyan Zhang]

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.

Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
---
 arch/riscv/Kconfig                    |  1 +
 arch/riscv/include/asm/pgtable-bits.h | 19 +++++++
 arch/riscv/include/asm/pgtable.h      | 75 ++++++++++++++++++++++++++-
 3 files changed, 93 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index e1b6a95952c4..db3337300c4c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -141,6 +141,7 @@ config RISCV
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
 	select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET
 	select HAVE_ARCH_SECCOMP_FILTER
+	select HAVE_ARCH_SOFT_DIRTY if 64BIT && MMU && RISCV_ISA_SVRSW60T59B
 	select HAVE_ARCH_THREAD_STRUCT_WHITELIST
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT && MMU
diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index 179bd4afece4..f3bac2bbc157 100644
--- a/arch/riscv/include/asm/pgtable-bits.h
+++ b/arch/riscv/include/asm/pgtable-bits.h
@@ -19,6 +19,25 @@
 #define _PAGE_SOFT      (3 << 8)    /* Reserved for software */
 
 #define _PAGE_SPECIAL   (1 << 8)    /* RSW: 0x1 */
+
+#ifdef CONFIG_MEM_SOFT_DIRTY
+
+/* ext_svrsw60t59b: bit 59 for soft-dirty tracking */
+#define _PAGE_SOFT_DIRTY						\
+	((riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B)) ?	\
+	 (1UL << 59) : 0)
+/*
+ * Bit 3 is always zero for swap entry computation, so we
+ * can borrow it for swap page soft-dirty tracking.
+ */
+#define _PAGE_SWP_SOFT_DIRTY						\
+	((riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B)) ?	\
+	 _PAGE_EXEC : 0)
+#else
+#define _PAGE_SOFT_DIRTY	0
+#define _PAGE_SWP_SOFT_DIRTY	0
+#endif /* CONFIG_MEM_SOFT_DIRTY */
+
 #define _PAGE_TABLE     _PAGE_PRESENT
 
 /*
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 91697fbf1f90..28057afaee33 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -427,7 +427,7 @@ static inline pte_t pte_mkwrite_novma(pte_t pte)
 
 static inline pte_t pte_mkdirty(pte_t pte)
 {
-	return __pte(pte_val(pte) | _PAGE_DIRTY);
+	return __pte(pte_val(pte) | _PAGE_DIRTY | _PAGE_SOFT_DIRTY);
 }
 
 static inline pte_t pte_mkclean(pte_t pte)
@@ -455,6 +455,42 @@ static inline pte_t pte_mkhuge(pte_t pte)
 	return pte;
 }
 
+#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
+#define pgtable_supports_soft_dirty()				\
+	(IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) &&			\
+	 riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B))
+
+static inline bool pte_soft_dirty(pte_t pte)
+{
+	return !!(pte_val(pte) & _PAGE_SOFT_DIRTY);
+}
+
+static inline pte_t pte_mksoft_dirty(pte_t pte)
+{
+	return __pte(pte_val(pte) | _PAGE_SOFT_DIRTY);
+}
+
+static inline pte_t pte_clear_soft_dirty(pte_t pte)
+{
+	return __pte(pte_val(pte) & ~(_PAGE_SOFT_DIRTY));
+}
+
+static inline bool pte_swp_soft_dirty(pte_t pte)
+{
+	return !!(pte_val(pte) & _PAGE_SWP_SOFT_DIRTY);
+}
+
+static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
+{
+	return __pte(pte_val(pte) | _PAGE_SWP_SOFT_DIRTY);
+}
+
+static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
+{
+	return __pte(pte_val(pte) & ~(_PAGE_SWP_SOFT_DIRTY));
+}
+#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
+
 #ifdef CONFIG_RISCV_ISA_SVNAPOT
 #define pte_leaf_size(pte)	(pte_napot(pte) ?				\
 					napot_cont_size(napot_cont_order(pte)) :\
@@ -802,6 +838,40 @@ static inline pud_t pud_mkspecial(pud_t pud)
 }
 #endif
 
+#ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
+static inline bool pmd_soft_dirty(pmd_t pmd)
+{
+	return pte_soft_dirty(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
+{
+	return pte_pmd(pte_mksoft_dirty(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
+{
+	return pte_pmd(pte_clear_soft_dirty(pmd_pte(pmd)));
+}
+
+#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
+static inline bool pmd_swp_soft_dirty(pmd_t pmd)
+{
+	return pte_swp_soft_dirty(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd)
+{
+	return pte_pmd(pte_swp_mksoft_dirty(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd)
+{
+	return pte_pmd(pte_swp_clear_soft_dirty(pmd_pte(pmd)));
+}
+#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */
+#endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */
+
 static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 				pmd_t *pmdp, pmd_t pmd)
 {
@@ -983,7 +1053,8 @@ static inline pud_t pud_modify(pud_t pud, pgprot_t newprot)
  *
  * Format of swap PTE:
  *	bit            0:	_PAGE_PRESENT (zero)
- *	bit       1 to 3:       _PAGE_LEAF (zero)
+ *	bit       1 to 2:	(zero)
+ *	bit            3:	_PAGE_SWP_SOFT_DIRTY
  *	bit            5:	_PAGE_PROT_NONE (zero)
  *	bit            6:	exclusive marker
  *	bits      7 to 11:	swap type
-- 
2.34.1

[PATCH V12 5/5] riscv: mm: Add userfaultfd write-protect support

[Chunyan Zhang]

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.

Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
---
 arch/riscv/Kconfig                    |  1 +
 arch/riscv/include/asm/pgtable-bits.h | 18 +++++++
 arch/riscv/include/asm/pgtable.h      | 68 +++++++++++++++++++++++++++
 3 files changed, 87 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index db3337300c4c..637edec03b2d 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -147,6 +147,7 @@ config RISCV
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if 64BIT && MMU
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if 64BIT && MMU
 	select HAVE_ARCH_USERFAULTFD_MINOR if 64BIT && USERFAULTFD
+	select HAVE_ARCH_USERFAULTFD_WP if 64BIT && MMU && USERFAULTFD && RISCV_ISA_SVRSW60T59B
 	select HAVE_ARCH_VMAP_STACK if MMU && 64BIT
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_CONTEXT_TRACKING_USER
diff --git a/arch/riscv/include/asm/pgtable-bits.h b/arch/riscv/include/asm/pgtable-bits.h
index f3bac2bbc157..b422d9691e60 100644
--- a/arch/riscv/include/asm/pgtable-bits.h
+++ b/arch/riscv/include/asm/pgtable-bits.h
@@ -38,6 +38,24 @@
 #define _PAGE_SWP_SOFT_DIRTY	0
 #endif /* CONFIG_MEM_SOFT_DIRTY */
 
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+
+/* ext_svrsw60t59b: Bit(60) for uffd-wp tracking */
+#define _PAGE_UFFD_WP							\
+	((riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B)) ?	\
+	 (1UL << 60) : 0)
+/*
+ * Bit 4 is not involved into swap entry computation, so we
+ * can borrow it for swap page uffd-wp tracking.
+ */
+#define _PAGE_SWP_UFFD_WP						\
+	((riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B)) ?	\
+	 _PAGE_USER : 0)
+#else
+#define _PAGE_UFFD_WP		0
+#define _PAGE_SWP_UFFD_WP	0
+#endif
+
 #define _PAGE_TABLE     _PAGE_PRESENT
 
 /*
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 28057afaee33..0d9ae32ae29e 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -416,6 +416,41 @@ static inline pte_t pte_wrprotect(pte_t pte)
 	return __pte(pte_val(pte) & ~(_PAGE_WRITE));
 }
 
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+#define pgtable_supports_uffd_wp()	\
+	riscv_has_extension_unlikely(RISCV_ISA_EXT_SVRSW60T59B)
+
+static inline bool pte_uffd_wp(pte_t pte)
+{
+	return !!(pte_val(pte) & _PAGE_UFFD_WP);
+}
+
+static inline pte_t pte_mkuffd_wp(pte_t pte)
+{
+	return pte_wrprotect(__pte(pte_val(pte) | _PAGE_UFFD_WP));
+}
+
+static inline pte_t pte_clear_uffd_wp(pte_t pte)
+{
+	return __pte(pte_val(pte) & ~(_PAGE_UFFD_WP));
+}
+
+static inline bool pte_swp_uffd_wp(pte_t pte)
+{
+	return !!(pte_val(pte) & _PAGE_SWP_UFFD_WP);
+}
+
+static inline pte_t pte_swp_mkuffd_wp(pte_t pte)
+{
+	return __pte(pte_val(pte) | _PAGE_SWP_UFFD_WP);
+}
+
+static inline pte_t pte_swp_clear_uffd_wp(pte_t pte)
+{
+	return __pte(pte_val(pte) & ~(_PAGE_SWP_UFFD_WP));
+}
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+
 /* static inline pte_t pte_mkread(pte_t pte) */
 
 static inline pte_t pte_mkwrite_novma(pte_t pte)
@@ -838,6 +873,38 @@ static inline pud_t pud_mkspecial(pud_t pud)
 }
 #endif
 
+#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP
+static inline bool pmd_uffd_wp(pmd_t pmd)
+{
+	return pte_uffd_wp(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_mkuffd_wp(pmd_t pmd)
+{
+	return pte_pmd(pte_mkuffd_wp(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_clear_uffd_wp(pmd_t pmd)
+{
+	return pte_pmd(pte_clear_uffd_wp(pmd_pte(pmd)));
+}
+
+static inline bool pmd_swp_uffd_wp(pmd_t pmd)
+{
+	return pte_swp_uffd_wp(pmd_pte(pmd));
+}
+
+static inline pmd_t pmd_swp_mkuffd_wp(pmd_t pmd)
+{
+	return pte_pmd(pte_swp_mkuffd_wp(pmd_pte(pmd)));
+}
+
+static inline pmd_t pmd_swp_clear_uffd_wp(pmd_t pmd)
+{
+	return pte_pmd(pte_swp_clear_uffd_wp(pmd_pte(pmd)));
+}
+#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */
+
 #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
 static inline bool pmd_soft_dirty(pmd_t pmd)
 {
@@ -1055,6 +1122,7 @@ static inline pud_t pud_modify(pud_t pud, pgprot_t newprot)
  *	bit            0:	_PAGE_PRESENT (zero)
  *	bit       1 to 2:	(zero)
  *	bit            3:	_PAGE_SWP_SOFT_DIRTY
+ *	bit            4:	_PAGE_SWP_UFFD_WP
  *	bit            5:	_PAGE_PROT_NONE (zero)
  *	bit            6:	exclusive marker
  *	bits      7 to 11:	swap type
-- 
2.34.1

Re: [PATCH V12 0/5] riscv: mm: Add soft-dirty and uffd-wp support

[David Hildenbrand]

On 15.09.25 12:13, Chunyan Zhang wrote:
> This patchset adds support for Svrsw60t59b [1] extension which is ratified now,
> also add soft dirty and userfaultfd write protect tracking for RISC-V.
> 
> The patches 1 and 2 add macros to allow architectures to define their own checks
> if the soft-dirty / uffd_wp PTE bits are available, in other words for RISC-V,
> the Svrsw60t59b extension is supported on which device the kernel is running.
> 
> This patchset has been tested with kselftest mm suite in which soft-dirty,
> madv_populate, test_unmerge_uffd_wp, and uffd-unit-tests run and pass,
> and no regressions are observed in any of the other tests.
> 
> This patchset applies on top of v6.17-rc6.

What are the plans for this series? It fails to apply on top of 
mm-unstable / mm-new, so likely merge conflicts when merging through 
another tree.

Likely best to base this on mm-new and route it through the MM tree?


-- 
Cheers

David / dhildenb

Re: [PATCH V12 1/5] mm: softdirty: Add pgtable_supports_soft_dirty()

[David Hildenbrand]

On 15.09.25 12:13, Chunyan Zhang wrote:
> Some platforms can customize the PTE PMD entry soft-dirty bit making it
> unavailable even if the architecture provides the resource.
> 
> Add an API which architectures can define their specific implementations
> to detect if soft-dirty bit is available on which device the kernel is
> running.

You should probably mention that we are removing "ifdef 
CONFIG_MEM_SOFT_DIRTY" in favor of pgtable_supports_soft_dirty() checks 
that defaults to IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) if not overriden by 
the arch -> no change in behavior expected.

Then you should mention that we make sure to never set VM_SOFTDIRTY if 
!pgtable_supports_soft_dirty(), so we will never run into VM_SOFTDIRTY 
checks.

> 
> Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
> ---
>   fs/proc/task_mmu.c      | 15 ++++++---------
>   include/linux/mm.h      |  3 +++
>   include/linux/pgtable.h | 12 ++++++++++++
>   mm/debug_vm_pgtable.c   | 10 +++++-----
>   mm/huge_memory.c        | 13 +++++++------
>   mm/internal.h           |  2 +-
>   mm/mmap.c               |  6 ++++--
>   mm/mremap.c             | 13 +++++++------
>   mm/userfaultfd.c        | 10 ++++------
>   mm/vma.c                |  6 ++++--
>   mm/vma_exec.c           |  5 ++++-
>   11 files changed, 57 insertions(+), 38 deletions(-)
> 

Good! All relevant CONFIG_MEM_SOFT_DIRTY occurrences seem to be gone 
now, which is nice.

Nothing jumped at me, hoping this makes cross-compilers happy.

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers

David / dhildenb

Re: [PATCH V12 2/5] mm: userfaultfd: Add pgtable_supports_uffd_wp()

[David Hildenbrand]

On 15.09.25 12:13, Chunyan Zhang wrote:
> Some platforms can customize the PTE/PMD entry uffd-wp bit making
> it unavailable even if the architecture provides the resource.
> This patch adds a macro API that allows architectures to define their
> specific implementations to check if the uffd-wp bit is available
> on which device the kernel is running.
> 

Similar to my reply to #1, you should probably summarize what you do 
regarding ifdef and "No functional change expected".

> Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
> ---

[...]

LGTM, one not below, thanks!

Acked-by: David Hildenbrand <david@redhat.com>

> +/*
> + * Some platforms can customize the uffd-wp bit, making it unavailable
> + * even if the architecture provides the resource.
> + * Adding this API allows architectures to add their own checks for the
> + * devices on which the kernel is running.
> + * Note: When overriding it, please make sure the
> + * CONFIG_HAVE_ARCH_USERFAULTFD_WP is part of this macro.
> + */
> +#ifndef pgtable_supports_uffd_wp
> +#define pgtable_supports_uffd_wp()	IS_ENABLED(CONFIG_HAVE_ARCH_USERFAULTFD_WP)
> +#endif
> +
> +static __always_inline bool uffd_supports_wp_marker(void)
> +{
> +	return pgtable_supports_uffd_wp() && IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP);
> +}

Likely a simple "inline" should do the trick?

> +
>   #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_WP
>   static __always_inline int pte_uffd_wp(pte_t pte)
>   {
> diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
> index 89b518ff097e..d6526a7f034b 100644
> --- a/include/linux/mm_inline.h
> +++ b/include/linux/mm_inline.h
> @@ -570,9 +570,15 @@ static inline bool
>   pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
>   			      pte_t *pte, pte_t pteval)
>   {


-- 
Cheers

David / dhildenb

Re: [PATCH V12 3/5] riscv: Add RISC-V Svrsw60t59b extension support

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 2538 bytes --]

On Mon, Sep 15, 2025 at 06:13:41PM +0800, Chunyan Zhang wrote:
> The Svrsw60t59b extension allows to free the PTE reserved bits 60
> and 59 for software to use.
> 
> Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
> ---
>  arch/riscv/Kconfig             | 14 ++++++++++++++
>  arch/riscv/include/asm/hwcap.h |  1 +
>  arch/riscv/kernel/cpufeature.c |  1 +
>  3 files changed, 16 insertions(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 51dcd8eaa243..e1b6a95952c4 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -862,6 +862,20 @@ config RISCV_ISA_ZICBOP
>  
>  	  If you don't know what to do here, say Y.
>  
> +config RISCV_ISA_SVRSW60T59B
> +	bool "Svrsw60t59b extension support for using PTE bits 60 and 59"
> +	depends on MMU && 64BIT
> +	depends on RISCV_ALTERNATIVE
> +	default y
> +	help
> +	  Adds support to dynamically detect the presence of the Svrsw60t59b
> +	  extension and enable its usage.
> +
> +	  The Svrsw60t59b extension allows to free the PTE reserved bits 60
> +	  and 59 for software to use.
> +
> +	  If you don't know what to do here, say Y.
> +
>  config TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI
>  	def_bool y
>  	# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index affd63e11b0a..f98fcb5c17d5 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -106,6 +106,7 @@
>  #define RISCV_ISA_EXT_ZAAMO		97
>  #define RISCV_ISA_EXT_ZALRSC		98
>  #define RISCV_ISA_EXT_ZICBOP		99
> +#define RISCV_ISA_EXT_SVRSW60T59B	100
>  
>  #define RISCV_ISA_EXT_XLINUXENVCFG	127
>  
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 743d53415572..2ba71d2d3fa3 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -539,6 +539,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
>  	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
>  	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
> +	__RISCV_ISA_EXT_DATA(svrsw60t59b, RISCV_ISA_EXT_SVRSW60T59B),
>  	__RISCV_ISA_EXT_DATA(svvptc, RISCV_ISA_EXT_SVVPTC),

If this is not ACPI only, than you need to document this in the
extensions dt-binding.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

Re: [PATCH V12 2/5] mm: userfaultfd: Add pgtable_supports_uffd_wp()

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 554 bytes --]

On Mon, Sep 15, 2025 at 06:13:40PM +0800, Chunyan Zhang wrote:
> Some platforms can customize the PTE/PMD entry uffd-wp bit making
> it unavailable even if the architecture provides the resource.
> This patch adds a macro API that allows architectures to define their
> specific implementations to check if the uffd-wp bit is available
> on which device the kernel is running.
> 
> Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>

According to patchwork CI for riscv, this doesn't build for 32-bit
defconfigs or the no-mmu defconfigs.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

Re: [PATCH V12 2/5] mm: userfaultfd: Add pgtable_supports_uffd_wp()

[kernel test robot]

Hi Chunyan,

kernel test robot noticed the following build errors:

[auto build test ERROR on brauner-vfs/vfs.all]
[also build test ERROR on kees/for-next/execve linus/master v6.17-rc6]
[cannot apply to akpm-mm/mm-everything next-20250915]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Chunyan-Zhang/mm-softdirty-Add-pgtable_supports_soft_dirty/20250915-181826
base:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git vfs.all
patch link:    https://lore.kernel.org/r/20250915101343.1449546-3-zhangchunyan%40iscas.ac.cn
patch subject: [PATCH V12 2/5] mm: userfaultfd: Add pgtable_supports_uffd_wp()
config: riscv-randconfig-002-20250916 (https://download.01.org/0day-ci/archive/20250916/202509161304.mQnxOxhS-lkp@intel.com/config)
compiler: riscv32-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250916/202509161304.mQnxOxhS-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202509161304.mQnxOxhS-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/linux/mm_inline.h:10,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:441:9: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
     441 |  return is_pte_marker_entry(entry) &&
         |         ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:10: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
     442 |         (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |          ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:34: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
     442 |         (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |                                  ^~~~~~~~~~~~~~~~~~
   include/linux/userfaultfd_k.h:442:34: note: each undeclared identifier is reported only once for each function it appears in
   include/linux/userfaultfd_k.h: In function 'pte_marker_uffd_wp':
>> include/linux/userfaultfd_k.h:452:7: error: implicit declaration of function 'is_swap_pte'; did you mean 'is_swap_pmd'? [-Werror=implicit-function-declaration]
     452 |  if (!is_swap_pte(pte))
         |       ^~~~~~~~~~~
         |       is_swap_pmd
>> include/linux/userfaultfd_k.h:455:10: error: implicit declaration of function 'pte_to_swp_entry' [-Werror=implicit-function-declaration]
     455 |  entry = pte_to_swp_entry(pte);
         |          ^~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:455:10: error: incompatible types when assigning to type 'swp_entry_t' from type 'int'
   In file included from include/linux/mm_inline.h:11,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
   include/linux/swapops.h: At top level:
>> include/linux/swapops.h:124:19: error: static declaration of 'is_swap_pte' follows non-static declaration
     124 | static inline int is_swap_pte(pte_t pte)
         |                   ^~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
   include/linux/userfaultfd_k.h:452:7: note: previous implicit declaration of 'is_swap_pte' was here
     452 |  if (!is_swap_pte(pte))
         |       ^~~~~~~~~~~
   In file included from include/linux/mm_inline.h:11,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
>> include/linux/swapops.h:133:27: error: conflicting types for 'pte_to_swp_entry'
     133 | static inline swp_entry_t pte_to_swp_entry(pte_t pte)
         |                           ^~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
   include/linux/userfaultfd_k.h:455:10: note: previous implicit declaration of 'pte_to_swp_entry' was here
     455 |  entry = pte_to_swp_entry(pte);
         |          ^~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:11,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
>> include/linux/swapops.h:429:20: error: conflicting types for 'is_pte_marker_entry'
     429 | static inline bool is_pte_marker_entry(swp_entry_t entry)
         |                    ^~~~~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
   include/linux/userfaultfd_k.h:441:9: note: previous implicit declaration of 'is_pte_marker_entry' was here
     441 |  return is_pte_marker_entry(entry) &&
         |         ^~~~~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:11,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
>> include/linux/swapops.h:434:26: error: conflicting types for 'pte_marker_get'
     434 | static inline pte_marker pte_marker_get(swp_entry_t entry)
         |                          ^~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/internal.h:13,
                    from mm/page_frag_cache.c:21:
   include/linux/userfaultfd_k.h:442:10: note: previous implicit declaration of 'pte_marker_get' was here
     442 |         (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |          ^~~~~~~~~~~~~~
   cc1: some warnings being treated as errors
--
   In file included from include/linux/mm_inline.h:10,
                    from mm/mremap.c:12:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
>> include/linux/userfaultfd_k.h:441:9: error: implicit declaration of function 'is_pte_marker_entry' [-Werror=implicit-function-declaration]
     441 |  return is_pte_marker_entry(entry) &&
         |         ^~~~~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:10: error: implicit declaration of function 'pte_marker_get' [-Werror=implicit-function-declaration]
     442 |         (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |          ^~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:442:34: error: 'PTE_MARKER_UFFD_WP' undeclared (first use in this function)
     442 |         (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |                                  ^~~~~~~~~~~~~~~~~~
   include/linux/userfaultfd_k.h:442:34: note: each undeclared identifier is reported only once for each function it appears in
   include/linux/userfaultfd_k.h: In function 'pte_marker_uffd_wp':
>> include/linux/userfaultfd_k.h:452:7: error: implicit declaration of function 'is_swap_pte'; did you mean 'is_swap_pmd'? [-Werror=implicit-function-declaration]
     452 |  if (!is_swap_pte(pte))
         |       ^~~~~~~~~~~
         |       is_swap_pmd
>> include/linux/userfaultfd_k.h:455:10: error: implicit declaration of function 'pte_to_swp_entry' [-Werror=implicit-function-declaration]
     455 |  entry = pte_to_swp_entry(pte);
         |          ^~~~~~~~~~~~~~~~
>> include/linux/userfaultfd_k.h:455:10: error: incompatible types when assigning to type 'swp_entry_t' from type 'int'
   In file included from include/linux/mm_inline.h:11,
                    from mm/mremap.c:12:
   include/linux/swapops.h: At top level:
>> include/linux/swapops.h:124:19: error: static declaration of 'is_swap_pte' follows non-static declaration
     124 | static inline int is_swap_pte(pte_t pte)
         |                   ^~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/mremap.c:12:
   include/linux/userfaultfd_k.h:452:7: note: previous implicit declaration of 'is_swap_pte' was here
     452 |  if (!is_swap_pte(pte))
         |       ^~~~~~~~~~~
   In file included from include/linux/mm_inline.h:11,
                    from mm/mremap.c:12:
>> include/linux/swapops.h:133:27: error: conflicting types for 'pte_to_swp_entry'
     133 | static inline swp_entry_t pte_to_swp_entry(pte_t pte)
         |                           ^~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/mremap.c:12:
   include/linux/userfaultfd_k.h:455:10: note: previous implicit declaration of 'pte_to_swp_entry' was here
     455 |  entry = pte_to_swp_entry(pte);
         |          ^~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:11,
                    from mm/mremap.c:12:
>> include/linux/swapops.h:429:20: error: conflicting types for 'is_pte_marker_entry'
     429 | static inline bool is_pte_marker_entry(swp_entry_t entry)
         |                    ^~~~~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/mremap.c:12:
   include/linux/userfaultfd_k.h:441:9: note: previous implicit declaration of 'is_pte_marker_entry' was here
     441 |  return is_pte_marker_entry(entry) &&
         |         ^~~~~~~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:11,
                    from mm/mremap.c:12:
>> include/linux/swapops.h:434:26: error: conflicting types for 'pte_marker_get'
     434 | static inline pte_marker pte_marker_get(swp_entry_t entry)
         |                          ^~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/mremap.c:12:
   include/linux/userfaultfd_k.h:442:10: note: previous implicit declaration of 'pte_marker_get' was here
     442 |         (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
         |          ^~~~~~~~~~~~~~
   In file included from include/linux/mm_inline.h:10,
                    from mm/mremap.c:12:
   include/linux/userfaultfd_k.h: In function 'pte_marker_entry_uffd_wp':
   include/linux/userfaultfd_k.h:443:1: warning: control reaches end of non-void function [-Wreturn-type]
     443 | }
         | ^
   cc1: some warnings being treated as errors


vim +/is_pte_marker_entry +441 include/linux/userfaultfd_k.h

2bad466cc9d9b4c Peter Xu      2023-03-09  435  
1db9dbc2ef05205 Peter Xu      2022-05-12  436  static inline bool pte_marker_entry_uffd_wp(swp_entry_t entry)
1db9dbc2ef05205 Peter Xu      2022-05-12  437  {
564509f441b4695 Chunyan Zhang 2025-09-15  438  	if (!uffd_supports_wp_marker())
564509f441b4695 Chunyan Zhang 2025-09-15  439  		return false;
564509f441b4695 Chunyan Zhang 2025-09-15  440  
1db9dbc2ef05205 Peter Xu      2022-05-12 @441  	return is_pte_marker_entry(entry) &&
1db9dbc2ef05205 Peter Xu      2022-05-12 @442  	       (pte_marker_get(entry) & PTE_MARKER_UFFD_WP);
1db9dbc2ef05205 Peter Xu      2022-05-12  443  }
1db9dbc2ef05205 Peter Xu      2022-05-12  444  
1db9dbc2ef05205 Peter Xu      2022-05-12  445  static inline bool pte_marker_uffd_wp(pte_t pte)
1db9dbc2ef05205 Peter Xu      2022-05-12  446  {
1db9dbc2ef05205 Peter Xu      2022-05-12  447  	swp_entry_t entry;
1db9dbc2ef05205 Peter Xu      2022-05-12  448  
564509f441b4695 Chunyan Zhang 2025-09-15  449  	if (!uffd_supports_wp_marker())
564509f441b4695 Chunyan Zhang 2025-09-15  450  		return false;
564509f441b4695 Chunyan Zhang 2025-09-15  451  
1db9dbc2ef05205 Peter Xu      2022-05-12 @452  	if (!is_swap_pte(pte))
1db9dbc2ef05205 Peter Xu      2022-05-12  453  		return false;
1db9dbc2ef05205 Peter Xu      2022-05-12  454  
1db9dbc2ef05205 Peter Xu      2022-05-12 @455  	entry = pte_to_swp_entry(pte);
1db9dbc2ef05205 Peter Xu      2022-05-12  456  
1db9dbc2ef05205 Peter Xu      2022-05-12  457  	return pte_marker_entry_uffd_wp(entry);
1db9dbc2ef05205 Peter Xu      2022-05-12  458  }
1db9dbc2ef05205 Peter Xu      2022-05-12  459  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH V12 4/5] riscv: mm: Add soft-dirty page tracking support

[Deepak Gupta]

On Mon, Sep 15, 2025 at 06:13:42PM +0800, Chunyan Zhang wrote:
>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.
>
>Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>

Reviewed-by: Deepak Gupta <debug@rivosinc.com>
>---

Re: [PATCH V12 3/5] riscv: Add RISC-V Svrsw60t59b extension support

[Deepak Gupta]

On Mon, Sep 15, 2025 at 06:13:41PM +0800, Chunyan Zhang wrote:
>The Svrsw60t59b extension allows to free the PTE reserved bits 60
>and 59 for software to use.
>
>Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
>Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
>Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>

Same comment as Conor for dt-bindings.
Other than that

Reviewed-by: Deepak Gupta <debug@rivosinc.com>
>---
> arch/riscv/Kconfig             | 14 ++++++++++++++
> arch/riscv/include/asm/hwcap.h |  1 +
> arch/riscv/kernel/cpufeature.c |  1 +
> 3 files changed, 16 insertions(+)
>
>diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>index 51dcd8eaa243..e1b6a95952c4 100644
>--- a/arch/riscv/Kconfig
>+++ b/arch/riscv/Kconfig
>@@ -862,6 +862,20 @@ config RISCV_ISA_ZICBOP
>
> 	  If you don't know what to do here, say Y.
>
>+config RISCV_ISA_SVRSW60T59B
>+	bool "Svrsw60t59b extension support for using PTE bits 60 and 59"
>+	depends on MMU && 64BIT
>+	depends on RISCV_ALTERNATIVE
>+	default y
>+	help
>+	  Adds support to dynamically detect the presence of the Svrsw60t59b
>+	  extension and enable its usage.
>+
>+	  The Svrsw60t59b extension allows to free the PTE reserved bits 60
>+	  and 59 for software to use.
>+
>+	  If you don't know what to do here, say Y.
>+
> config TOOLCHAIN_NEEDS_EXPLICIT_ZICSR_ZIFENCEI
> 	def_bool y
> 	# https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=aed44286efa8ae8717a77d94b51ac3614e2ca6dc
>diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
>index affd63e11b0a..f98fcb5c17d5 100644
>--- a/arch/riscv/include/asm/hwcap.h
>+++ b/arch/riscv/include/asm/hwcap.h
>@@ -106,6 +106,7 @@
> #define RISCV_ISA_EXT_ZAAMO		97
> #define RISCV_ISA_EXT_ZALRSC		98
> #define RISCV_ISA_EXT_ZICBOP		99
>+#define RISCV_ISA_EXT_SVRSW60T59B	100
>
> #define RISCV_ISA_EXT_XLINUXENVCFG	127
>
>diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
>index 743d53415572..2ba71d2d3fa3 100644
>--- a/arch/riscv/kernel/cpufeature.c
>+++ b/arch/riscv/kernel/cpufeature.c
>@@ -539,6 +539,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
> 	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
> 	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
> 	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
>+	__RISCV_ISA_EXT_DATA(svrsw60t59b, RISCV_ISA_EXT_SVRSW60T59B),
> 	__RISCV_ISA_EXT_DATA(svvptc, RISCV_ISA_EXT_SVVPTC),
> };
>
>-- 
>2.34.1
>