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Fri, 29 May 2026 13:27:29 -0400 (EDT) From: "Kiryl Shutsemau (Meta)" To: akpm@linux-foundation.org, rppt@kernel.org, peterx@redhat.com, david@kernel.org Cc: ljs@kernel.org, surenb@google.com, vbabka@kernel.org, Liam.Howlett@oracle.com, ziy@nvidia.com, corbet@lwn.net, skhan@linuxfoundation.org, seanjc@google.com, pbonzini@redhat.com, jthoughton@google.com, aarcange@redhat.com, sj@kernel.org, usama.arif@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org, kernel-team@meta.com, kas@kernel.org Subject: [PATCH v6 01/15] mm: decouple protnone helpers from CONFIG_NUMA_BALANCING Date: Fri, 29 May 2026 18:26:30 +0100 Message-ID: <20260529172716.357179-2-kas@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260529172716.357179-1-kas@kernel.org> References: <20260529172716.357179-1-kas@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 3B95A120003 X-Stat-Signature: no5n7ui4cmtuijkxwbxuhymwfkqrfx3k X-HE-Tag: 1780075654-739416 X-HE-Meta: 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 YxCGX+dj z6PsLgaG3/WsZRKp5G7DL4zx2MzvmdnstYqW5frvm/+5Le1JkJAPw+o1xsW+Qzl2hX31gx8umG0fAjbSSAIiQP9ZTeaXGhF6PN3Ol2D6ZuXZlAjfCG5ENUMZ1lcLZgQBl+FQFQOJ3Grb3lmN9X/9/8ui0np5rAxr0vKxtizhglqif3darOdTH6289NqFfQqKHIVaCYJ90GgezK5wXh+xpq2tmFYeN02OFVobGlUN65++IYjhcJLC10QzsCOuuOqnQ0hiYm8EucvyfsrvWLC+OMRT1ctFhVZa4iPpgk1IqROvuRSHQj/wCiD6wxFVPZngQOi9kHShbCqGsVzwkDZvsAYhZcg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: pte_protnone() and pmd_protnone() detect present-but-inaccessible page table entries. This capability is useful beyond NUMA balancing -- for example, userfaultfd working set tracking uses protnone PTEs to track page access without unmapping pages. Introduce CONFIG_ARCH_HAS_PTE_PROTNONE to decouple the protnone PTE infrastructure from CONFIG_NUMA_BALANCING. The six architectures that support protnone PTEs (x86_64, arm64, powerpc, s390, riscv, loongarch) now select this option, and CONFIG_NUMA_BALANCING depends on it. No functional change -- the same set of architectures continues to have working protnone support, but the infrastructure is now available independently of NUMA balancing. Signed-off-by: Kiryl Shutsemau (Meta) Assisted-by: Claude:claude-opus-4-6 Acked-by: SeongJae Park Acked-by: Mike Rapoport (Microsoft) --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/pgtable.h | 7 ++--- arch/loongarch/Kconfig | 1 + arch/loongarch/include/asm/pgtable.h | 4 +-- arch/powerpc/include/asm/book3s/64/pgtable.h | 8 ++--- arch/powerpc/platforms/Kconfig.cputype | 1 + arch/riscv/Kconfig | 1 + arch/riscv/include/asm/pgtable.h | 7 ++--- arch/s390/Kconfig | 1 + arch/s390/include/asm/pgtable.h | 4 +-- arch/x86/Kconfig | 1 + arch/x86/include/asm/pgtable.h | 8 ++--- include/linux/pgtable.h | 32 ++++++++++++++------ init/Kconfig | 8 +++++ mm/debug_vm_pgtable.c | 4 +-- 15 files changed, 52 insertions(+), 36 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index fe60738e5943..319470b3b1bb 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -78,6 +78,7 @@ config ARM64 select ARCH_SUPPORTS_CFI select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 + select ARCH_HAS_PTE_PROTNONE select ARCH_SUPPORTS_NUMA_BALANCING select ARCH_SUPPORTS_PAGE_TABLE_CHECK select ARCH_SUPPORTS_PER_VMA_LOCK diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 4dfa42b7d053..873f4ea2e288 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -553,10 +553,7 @@ static inline pte_t pte_swp_clear_uffd_wp(pte_t pte) } #endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ -#ifdef CONFIG_NUMA_BALANCING -/* - * See the comment in include/linux/pgtable.h - */ +#ifdef CONFIG_ARCH_HAS_PTE_PROTNONE static inline int pte_protnone(pte_t pte) { /* @@ -575,7 +572,7 @@ static inline int pmd_protnone(pmd_t pmd) { return pte_protnone(pmd_pte(pmd)); } -#endif +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ #define pmd_present(pmd) pte_present(pmd_pte(pmd)) #define pmd_dirty(pmd) pte_dirty(pmd_pte(pmd)) diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig index 606597da46b8..c085f5067b3b 100644 --- a/arch/loongarch/Kconfig +++ b/arch/loongarch/Kconfig @@ -67,6 +67,7 @@ config LOONGARCH select ARCH_SUPPORTS_LTO_CLANG select ARCH_SUPPORTS_LTO_CLANG_THIN select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS + select ARCH_HAS_PTE_PROTNONE if 64BIT select ARCH_SUPPORTS_NUMA_BALANCING if NUMA select ARCH_SUPPORTS_PER_VMA_LOCK select ARCH_SUPPORTS_RT diff --git a/arch/loongarch/include/asm/pgtable.h b/arch/loongarch/include/asm/pgtable.h index 2a0b63ae421f..d295447a2763 100644 --- a/arch/loongarch/include/asm/pgtable.h +++ b/arch/loongarch/include/asm/pgtable.h @@ -619,7 +619,7 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ -#ifdef CONFIG_NUMA_BALANCING +#ifdef CONFIG_ARCH_HAS_PTE_PROTNONE static inline long pte_protnone(pte_t pte) { return (pte_val(pte) & _PAGE_PROTNONE); @@ -629,7 +629,7 @@ static inline long pmd_protnone(pmd_t pmd) { return (pmd_val(pmd) & _PAGE_PROTNONE); } -#endif /* CONFIG_NUMA_BALANCING */ +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ #define pmd_leaf(pmd) ((pmd_val(pmd) & _PAGE_HUGE) != 0) #define pud_leaf(pud) ((pud_val(pud) & _PAGE_HUGE) != 0) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index e67e64ac6e8c..53a0c5892548 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -490,13 +490,13 @@ static inline pte_t pte_clear_soft_dirty(pte_t pte) } #endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */ -#ifdef CONFIG_NUMA_BALANCING +#ifdef CONFIG_ARCH_HAS_PTE_PROTNONE static inline int pte_protnone(pte_t pte) { return (pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE | _PAGE_RWX)) == cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE); } -#endif /* CONFIG_NUMA_BALANCING */ +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ static inline bool pte_hw_valid(pte_t pte) { @@ -1067,12 +1067,12 @@ static inline pte_t *pmdp_ptep(pmd_t *pmd) #endif #endif /* CONFIG_HAVE_ARCH_SOFT_DIRTY */ -#ifdef CONFIG_NUMA_BALANCING +#ifdef CONFIG_ARCH_HAS_PTE_PROTNONE static inline int pmd_protnone(pmd_t pmd) { return pte_protnone(pmd_pte(pmd)); } -#endif /* CONFIG_NUMA_BALANCING */ +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ #define pmd_write(pmd) pte_write(pmd_pte(pmd)) diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype index bac02c83bb3e..36b64a24cf30 100644 --- a/arch/powerpc/platforms/Kconfig.cputype +++ b/arch/powerpc/platforms/Kconfig.cputype @@ -87,6 +87,7 @@ config PPC_BOOK3S_64 select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION select ARCH_ENABLE_SPLIT_PMD_PTLOCK select ARCH_SUPPORTS_HUGETLBFS + select ARCH_HAS_PTE_PROTNONE select ARCH_SUPPORTS_NUMA_BALANCING select HAVE_MOVE_PMD select HAVE_MOVE_PUD diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index c5754942cf85..e2c5776d18cf 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -71,6 +71,7 @@ config RISCV select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS if 64BIT && MMU select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU select ARCH_SUPPORTS_PER_VMA_LOCK if MMU + select ARCH_HAS_PTE_PROTNONE if MMU select ARCH_SUPPORTS_RT select ARCH_SUPPORTS_SHADOW_CALL_STACK if HAVE_SHADOW_CALL_STACK select ARCH_SUPPORTS_SCHED_MC if SMP diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index a1a7c6520a09..48a127323b21 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -524,10 +524,7 @@ static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) PAGE_SIZE) #endif -#ifdef CONFIG_NUMA_BALANCING -/* - * See the comment in include/asm-generic/pgtable.h - */ +#ifdef CONFIG_ARCH_HAS_PTE_PROTNONE static inline int pte_protnone(pte_t pte) { return (pte_val(pte) & (_PAGE_PRESENT | _PAGE_PROT_NONE)) == _PAGE_PROT_NONE; @@ -537,7 +534,7 @@ static inline int pmd_protnone(pmd_t pmd) { return pte_protnone(pmd_pte(pmd)); } -#endif +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ /* Modify page protection bits */ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot) diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index ecbcbb781e40..bc5bef08454b 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -151,6 +151,7 @@ config S390 select ARCH_SUPPORTS_HUGETLBFS select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && CC_IS_CLANG select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS + select ARCH_HAS_PTE_PROTNONE select ARCH_SUPPORTS_NUMA_BALANCING select ARCH_SUPPORTS_PAGE_TABLE_CHECK select ARCH_SUPPORTS_PER_VMA_LOCK diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h index 2c6cee8241e0..97241dea5573 100644 --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -842,7 +842,7 @@ static inline int pte_same(pte_t a, pte_t b) return pte_val(a) == pte_val(b); } -#ifdef CONFIG_NUMA_BALANCING +#ifdef CONFIG_ARCH_HAS_PTE_PROTNONE static inline int pte_protnone(pte_t pte) { return pte_present(pte) && !(pte_val(pte) & _PAGE_READ); @@ -853,7 +853,7 @@ static inline int pmd_protnone(pmd_t pmd) /* pmd_leaf(pmd) implies pmd_present(pmd) */ return pmd_leaf(pmd) && !(pmd_val(pmd) & _SEGMENT_ENTRY_READ); } -#endif +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ static inline bool pte_swp_exclusive(pte_t pte) { diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f3f7cb01d69d..9da1119e8ff6 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -123,6 +123,7 @@ config X86 select ARCH_SUPPORTS_DEBUG_PAGEALLOC select ARCH_SUPPORTS_HUGETLBFS select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64 + select ARCH_HAS_PTE_PROTNONE if X86_64 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096 select ARCH_SUPPORTS_CFI if X86_64 diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 2187e9cfcefa..c7f014cbf0a9 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -985,11 +985,7 @@ static inline int pmd_present(pmd_t pmd) return pmd_flags(pmd) & (_PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_PSE); } -#ifdef CONFIG_NUMA_BALANCING -/* - * These work without NUMA balancing but the kernel does not care. See the - * comment in include/linux/pgtable.h - */ +#ifdef CONFIG_ARCH_HAS_PTE_PROTNONE static inline int pte_protnone(pte_t pte) { return (pte_flags(pte) & (_PAGE_PROTNONE | _PAGE_PRESENT)) @@ -1001,7 +997,7 @@ static inline int pmd_protnone(pmd_t pmd) return (pmd_flags(pmd) & (_PAGE_PROTNONE | _PAGE_PRESENT)) == _PAGE_PROTNONE; } -#endif /* CONFIG_NUMA_BALANCING */ +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ static inline int pmd_none(pmd_t pmd) { diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index cdd68ed3ae1a..b6516a11adfa 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -2052,18 +2052,26 @@ static inline int pud_trans_unstable(pud_t *pud) return 0; } -#ifndef CONFIG_NUMA_BALANCING +#ifndef CONFIG_ARCH_HAS_PTE_PROTNONE /* - * In an inaccessible (PROT_NONE) VMA, pte_protnone() may indicate "yes". It is - * perfectly valid to indicate "no" in that case, which is why our default - * implementation defaults to "always no". + * In an inaccessible (PROT_NONE) VMA, pte_protnone() may indicate "yes". It + * is perfectly valid to indicate "no" in that case, which is why our + * default implementation defaults to "always no". * - * In an accessible VMA, however, pte_protnone() reliably indicates PROT_NONE - * page protection due to NUMA hinting. NUMA hinting faults only apply in - * accessible VMAs. + * In an accessible VMA, pte_protnone() reliably indicates a present + * PROT_NONE page protection. Today the kernel uses such PTEs for two + * purposes: NUMA hinting faults, and userfaultfd RWP tracking on + * VM_UFFD_RWP VMAs. The two are distinguished by the uffd PTE bit and + * the VMA flag; see include/linux/userfaultfd_k.h. * - * So, to reliably identify PROT_NONE PTEs that require a NUMA hinting fault, - * looking at the VMA accessibility is sufficient. + * So, to reliably identify PROT_NONE PTEs that require kernel handling, + * looking at the VMA accessibility (and the uffd bit on RWP VMAs) is + * sufficient. + * + * Architectures without CONFIG_ARCH_HAS_PTE_PROTNONE get the always-zero + * stubs below; PAGE_NONE references that survive to runtime fire the + * BUILD_BUG() fallback, since callers should have folded such paths to + * dead code via IS_ENABLED(CONFIG_ARCH_HAS_PTE_PROTNONE). */ static inline int pte_protnone(pte_t pte) { @@ -2074,7 +2082,11 @@ static inline int pmd_protnone(pmd_t pmd) { return 0; } -#endif /* CONFIG_NUMA_BALANCING */ + +#ifndef PAGE_NONE +#define PAGE_NONE ({ BUILD_BUG(); (pgprot_t){0}; }) +#endif +#endif /* CONFIG_ARCH_HAS_PTE_PROTNONE */ #endif /* CONFIG_MMU */ diff --git a/init/Kconfig b/init/Kconfig index 2937c4d308ae..58abb7f19206 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -944,6 +944,13 @@ config SCHED_PROXY_EXEC endmenu +# +# For architectures that support present-but-inaccessible (PROT_NONE) page +# table entries detectable via pte_protnone() / pmd_protnone(): +# +config ARCH_HAS_PTE_PROTNONE + bool + # # For architectures that want to enable the support for NUMA-affine scheduler # balancing logic: @@ -1010,6 +1017,7 @@ config ARCH_WANT_NUMA_VARIABLE_LOCALITY config NUMA_BALANCING bool "Memory placement aware NUMA scheduler" depends on ARCH_SUPPORTS_NUMA_BALANCING + depends on ARCH_HAS_PTE_PROTNONE depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY depends on SMP && NUMA_MIGRATION && !PREEMPT_RT help diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index 23dc3ee09561..5e9f3a35f924 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -672,7 +672,7 @@ static void __init pte_protnone_tests(struct pgtable_debug_args *args) { pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot_none); - if (!IS_ENABLED(CONFIG_NUMA_BALANCING)) + if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_PROTNONE)) return; pr_debug("Validating PTE protnone\n"); @@ -685,7 +685,7 @@ static void __init pmd_protnone_tests(struct pgtable_debug_args *args) { pmd_t pmd; - if (!IS_ENABLED(CONFIG_NUMA_BALANCING)) + if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_PROTNONE)) return; if (!has_transparent_hugepage()) -- 2.54.0