From c6f11553c067d7d9ed2dcffe1e01780441d4e6e2 Mon Sep 17 00:00:00 2001 From: "Kiryl Shutsemau (Meta)" Date: Wed, 8 Jul 2026 12:14:02 +0100 Subject: mm: decouple protnone helpers from CONFIG_NUMA_BALANCING Patch series "userfaultfd: working set tracking for VM guest memory", v10. This series adds userfaultfd support for tracking the working set of VM guest memory, so a VMM can identify hot pages and reclaim cold ones to tiered or remote storage. This patch (of 15): 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. Link: https://lore.kernel.org/20260708111417.173443-1-kirill@shutemov.name Link: https://lore.kernel.org/20260708111417.173443-2-kirill@shutemov.name Signed-off-by: Kiryl Shutsemau (Meta) Assisted-by: Claude:claude-opus-4-6 Acked-by: SeongJae Park Acked-by: Mike Rapoport (Microsoft) Cc: Andrea Arcangeli Cc: David Hildenbrand Cc: James Houghton Cc: Jonathan Corbet Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Paolo Bonzini Cc: Peter Xu Cc: Sean Christopherson Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton --- init/Kconfig | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'init/Kconfig') diff --git a/init/Kconfig b/init/Kconfig index 10f2013b5321..c24f345f794b 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -947,6 +947,13 @@ 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: @@ -1013,6 +1020,7 @@ 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 -- cgit v1.2.3 From e474ac24a79211f83e214d856630829f77363459 Mon Sep 17 00:00:00 2001 From: Leon Hwang Date: Wed, 15 Jul 2026 21:12:58 +0800 Subject: mm/mseal: fix mseal documentation for 32-bit kernels MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit mseal.o is built only for 64-bit kernels, so 32-bit kernels fall back to sys_ni_syscall() and return -ENOSYS rather than -EPERM. Drop architecture description in mseal.rst, since the arch feature doc has the latest state of mseal for each architecture. Fix the CONFIG_MSEAL_SYSTEM_MAPPINGS typo in init/Kconfig. Link: https://lore.kernel.org/20260715131258.55499-1-leon.hwang@linux.dev Signed-off-by: Leon Hwang Acked-by: Lance Yang Cc: Alice Ryhl Cc: Anand Moon Cc: Doug Anderson Cc: Gary Guo Cc: Jann Horn Cc: Jonathan Corbet Cc: Leon Hwang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Miguel Ojeda Cc: Nathan Chancellor Cc: Pedro Falcato Cc: Peter Zijlstra Cc: Randy Dunlap Cc: Thomas Weißschuh Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- Documentation/userspace-api/mseal.rst | 14 ++++++-------- init/Kconfig | 2 +- 2 files changed, 7 insertions(+), 9 deletions(-) (limited to 'init/Kconfig') diff --git a/Documentation/userspace-api/mseal.rst b/Documentation/userspace-api/mseal.rst index ea9b11a0bd89..c039d782f9f5 100644 --- a/Documentation/userspace-api/mseal.rst +++ b/Documentation/userspace-api/mseal.rst @@ -50,8 +50,8 @@ mseal syscall signature * The start address (``addr``) is not allocated. * The end address (``addr`` + ``len``) is not allocated. * A gap (unallocated memory) between start and end address. - - **-EPERM**: - * sealing is supported only on 64-bit CPUs, 32-bit is not supported. + - **-ENOSYS**: + * The kernel does not implement ``mseal()``. **Note about error return**: - For above error cases, users can expect the given memory range is @@ -62,7 +62,8 @@ mseal syscall signature memory range could happen. However, those cases should be rare. **Architecture support**: - mseal only works on 64-bit CPUs, not 32-bit CPUs. + mseal is built only for 64-bit kernels. 32-bit kernels return + ``-ENOSYS``. **Idempotent**: users can call mseal multiple times. mseal on an already sealed memory @@ -131,11 +132,11 @@ Use cases - Chrome browser: protect some security sensitive data structures. - System mappings: - The system mappings are created by the kernel and includes vdso, vvar, + The system mappings are created by the kernel and include vdso, vvar, vvar_vclock, vectors (arm compat-mode), sigpage (arm compat-mode), uprobes. Those system mappings are readonly only or execute only, memory sealing can - protect them from ever changing to writable or unmmap/remapped as different + protect them from ever changing to writable or unmapped/remapped as different attributes. This is useful to mitigate memory corruption issues where a corrupted pointer is passed to a memory management system. @@ -143,9 +144,6 @@ Use cases the CONFIG_MSEAL_SYSTEM_MAPPINGS seals all system mappings of this architecture. - The following architectures currently support this feature: x86-64, arm64, - loongarch and s390. - WARNING: This feature breaks programs which rely on relocating or unmapping system mappings. Known broken software at the time of writing includes CHECKPOINT_RESTORE, UML, gVisor, rr. Therefore diff --git a/init/Kconfig b/init/Kconfig index c24f345f794b..13cb6fdd9c37 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2123,7 +2123,7 @@ config ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS from a kernel perspective. After the architecture enables this, a distribution can set - CONFIG_MSEAL_SYSTEM_MAPPING to manage access to the feature. + CONFIG_MSEAL_SYSTEM_MAPPINGS to manage access to the feature. For complete descriptions of memory sealing, please see Documentation/userspace-api/mseal.rst -- cgit v1.2.3