Merge tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:

 - "Add folio_mk_pte()" from Matthew Wilcox simplifies the act of
   creating a pte which addresses the first page in a folio and reduces
   the amount of plumbing which architecture must implement to provide
   this.

 - "Misc folio patches for 6.16" from Matthew Wilcox is a shower of
   largely unrelated folio infrastructure changes which clean things up
   and better prepare us for future work.

 - "memory,x86,acpi: hotplug memory alignment advisement" from Gregory
   Price adds early-init code to prevent x86 from leaving physical
   memory unused when physical address regions are not aligned to memory
   block size.

 - "mm/compaction: allow more aggressive proactive compaction" from
   Michal Clapinski provides some tuning of the (sadly, hard-coded (more
   sadly, not auto-tuned)) thresholds for our invokation of proactive
   compaction. In a simple test case, the reduction of a guest VM's
   memory consumption was dramatic.

 - "Minor cleanups and improvements to swap freeing code" from Kemeng
   Shi provides some code cleaups and a small efficiency improvement to
   this part of our swap handling code.

 - "ptrace: introduce PTRACE_SET_SYSCALL_INFO API" from Dmitry Levin
   adds the ability for a ptracer to modify syscalls arguments. At this
   time we can alter only "system call information that are used by
   strace system call tampering, namely, syscall number, syscall
   arguments, and syscall return value.

   This series should have been incorporated into mm.git's "non-MM"
   branch, but I goofed.

 - "fs/proc: extend the PAGEMAP_SCAN ioctl to report guard regions" from
   Andrei Vagin extends the info returned by the PAGEMAP_SCAN ioctl
   against /proc/pid/pagemap. This permits CRIU to more efficiently get
   at the info about guard regions.

 - "Fix parameter passed to page_mapcount_is_type()" from Gavin Shan
   implements that fix. No runtime effect is expected because
   validate_page_before_insert() happens to fix up this error.

 - "kernel/events/uprobes: uprobe_write_opcode() rewrite" from David
   Hildenbrand basically brings uprobe text poking into the current
   decade. Remove a bunch of hand-rolled implementation in favor of
   using more current facilities.

 - "mm/ptdump: Drop assumption that pxd_val() is u64" from Anshuman
   Khandual provides enhancements and generalizations to the pte dumping
   code. This might be needed when 128-bit Page Table Descriptors are
   enabled for ARM.

 - "Always call constructor for kernel page tables" from Kevin Brodsky
   ensures that the ctor/dtor is always called for kernel pgtables, as
   it already is for user pgtables.

   This permits the addition of more functionality such as "insert hooks
   to protect page tables". This change does result in various
   architectures performing unnecesary work, but this is fixed up where
   it is anticipated to occur.

 - "Rust support for mm_struct, vm_area_struct, and mmap" from Alice
   Ryhl adds plumbing to permit Rust access to core MM structures.

 - "fix incorrectly disallowed anonymous VMA merges" from Lorenzo
   Stoakes takes advantage of some VMA merging opportunities which we've
   been missing for 15 years.

 - "mm/madvise: batch tlb flushes for MADV_DONTNEED and MADV_FREE" from
   SeongJae Park optimizes process_madvise()'s TLB flushing.

   Instead of flushing each address range in the provided iovec, we
   batch the flushing across all the iovec entries. The syscall's cost
   was approximately halved with a microbenchmark which was designed to
   load this particular operation.

 - "Track node vacancy to reduce worst case allocation counts" from
   Sidhartha Kumar makes the maple tree smarter about its node
   preallocation.

   stress-ng mmap performance increased by single-digit percentages and
   the amount of unnecessarily preallocated memory was dramaticelly
   reduced.

 - "mm/gup: Minor fix, cleanup and improvements" from Baoquan He removes
   a few unnecessary things which Baoquan noted when reading the code.

 - ""Enhance sysfs handling for memory hotplug in weighted interleave"
   from Rakie Kim "enhances the weighted interleave policy in the memory
   management subsystem by improving sysfs handling, fixing memory
   leaks, and introducing dynamic sysfs updates for memory hotplug
   support". Fixes things on error paths which we are unlikely to hit.

 - "mm/damon: auto-tune DAMOS for NUMA setups including tiered memory"
   from SeongJae Park introduces new DAMOS quota goal metrics which
   eliminate the manual tuning which is required when utilizing DAMON
   for memory tiering.

 - "mm/vmalloc.c: code cleanup and improvements" from Baoquan He
   provides cleanups and small efficiency improvements which Baoquan
   found via code inspection.

 - "vmscan: enforce mems_effective during demotion" from Gregory Price
   changes reclaim to respect cpuset.mems_effective during demotion when
   possible. because presently, reclaim explicitly ignores
   cpuset.mems_effective when demoting, which may cause the cpuset
   settings to violated.

   This is useful for isolating workloads on a multi-tenant system from
   certain classes of memory more consistently.

 - "Clean up split_huge_pmd_locked() and remove unnecessary folio
   pointers" from Gavin Guo provides minor cleanups and efficiency gains
   in in the huge page splitting and migrating code.

 - "Use kmem_cache for memcg alloc" from Huan Yang creates a slab cache
   for `struct mem_cgroup', yielding improved memory utilization.

 - "add max arg to swappiness in memory.reclaim and lru_gen" from
   Zhongkun He adds a new "max" argument to the "swappiness=" argument
   for memory.reclaim MGLRU's lru_gen.

   This directs proactive reclaim to reclaim from only anon folios
   rather than file-backed folios.

 - "kexec: introduce Kexec HandOver (KHO)" from Mike Rapoport is the
   first step on the path to permitting the kernel to maintain existing
   VMs while replacing the host kernel via file-based kexec. At this
   time only memblock's reserve_mem is preserved.

 - "mm: Introduce for_each_valid_pfn()" from David Woodhouse provides
   and uses a smarter way of looping over a pfn range. By skipping
   ranges of invalid pfns.

 - "sched/numa: Skip VMA scanning on memory pinned to one NUMA node via
   cpuset.mems" from Libo Chen removes a lot of pointless VMA scanning
   when a task is pinned a single NUMA mode.

   Dramatic performance benefits were seen in some real world cases.

 - "JFS: Implement migrate_folio for jfs_metapage_aops" from Shivank
   Garg addresses a warning which occurs during memory compaction when
   using JFS.

 - "move all VMA allocation, freeing and duplication logic to mm" from
   Lorenzo Stoakes moves some VMA code from kernel/fork.c into the more
   appropriate mm/vma.c.

 - "mm, swap: clean up swap cache mapping helper" from Kairui Song
   provides code consolidation and cleanups related to the folio_index()
   function.

 - "mm/gup: Cleanup memfd_pin_folios()" from Vishal Moola does that.

 - "memcg: Fix test_memcg_min/low test failures" from Waiman Long
   addresses some bogus failures which are being reported by the
   test_memcontrol selftest.

 - "eliminate mmap() retry merge, add .mmap_prepare hook" from Lorenzo
   Stoakes commences the deprecation of file_operations.mmap() in favor
   of the new file_operations.mmap_prepare().

   The latter is more restrictive and prevents drivers from messing with
   things in ways which, amongst other problems, may defeat VMA merging.

 - "memcg: decouple memcg and objcg stocks"" from Shakeel Butt decouples
   the per-cpu memcg charge cache from the objcg's one.

   This is a step along the way to making memcg and objcg charging
   NMI-safe, which is a BPF requirement.

 - "mm/damon: minor fixups and improvements for code, tests, and
   documents" from SeongJae Park is yet another batch of miscellaneous
   DAMON changes. Fix and improve minor problems in code, tests and
   documents.

 - "memcg: make memcg stats irq safe" from Shakeel Butt converts memcg
   stats to be irq safe. Another step along the way to making memcg
   charging and stats updates NMI-safe, a BPF requirement.

 - "Let unmap_hugepage_range() and several related functions take folio
   instead of page" from Fan Ni provides folio conversions in the
   hugetlb code.

* tag 'mm-stable-2025-05-31-14-50' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (285 commits)
  mm: pcp: increase pcp->free_count threshold to trigger free_high
  mm/hugetlb: convert use of struct page to folio in __unmap_hugepage_range()
  mm/hugetlb: refactor __unmap_hugepage_range() to take folio instead of page
  mm/hugetlb: refactor unmap_hugepage_range() to take folio instead of page
  mm/hugetlb: pass folio instead of page to unmap_ref_private()
  memcg: objcg stock trylock without irq disabling
  memcg: no stock lock for cpu hot-unplug
  memcg: make __mod_memcg_lruvec_state re-entrant safe against irqs
  memcg: make count_memcg_events re-entrant safe against irqs
  memcg: make mod_memcg_state re-entrant safe against irqs
  memcg: move preempt disable to callers of memcg_rstat_updated
  memcg: memcg_rstat_updated re-entrant safe against irqs
  mm: khugepaged: decouple SHMEM and file folios' collapse
  selftests/eventfd: correct test name and improve messages
  alloc_tag: check mem_profiling_support in alloc_tag_init
  Docs/damon: update titles and brief introductions to explain DAMOS
  selftests/damon/_damon_sysfs: read tried regions directories in order
  mm/damon/tests/core-kunit: add a test for damos_set_filters_default_reject()
  mm/damon/paddr: remove unused variable, folio_list, in damon_pa_stat()
  mm/damon/sysfs-schemes: fix wrong comment on damons_sysfs_quota_goal_metric_strs
  ...

8 files changed, 317 insertions, 0 deletions

diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index e9789bd381d8..7a4ca18ca6e2 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -115,6 +115,7 @@ more memory-management documentation in Documentation/mm/index.rst.
    pin_user_pages
    boot-time-mm
    gfp_mask-from-fs-io
+   kho/index
 
 Interfaces for kernel debugging
 ===============================
diff --git a/Documentation/core-api/kho/bindings/kho.yaml b/Documentation/core-api/kho/bindings/kho.yaml
new file mode 100644
index 000000000000..11e8ab7b219d
--- /dev/null
+++ b/Documentation/core-api/kho/bindings/kho.yaml
@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+title: Kexec HandOver (KHO) root tree
+
+maintainers:
+  - Mike Rapoport <rppt@kernel.org>
+  - Changyuan Lyu <changyuanl@google.com>
+
+description: |
+  System memory preserved by KHO across kexec.
+
+properties:
+  compatible:
+    enum:
+      - kho-v1
+
+  preserved-memory-map:
+    description: |
+      physical address (u64) of an in-memory structure describing all preserved
+      folios and memory ranges.
+
+patternProperties:
+  "$[0-9a-f_]+^":
+    $ref: sub-fdt.yaml#
+    description: physical address of a KHO user's own FDT.
+
+required:
+  - compatible
+  - preserved-memory-map
+
+additionalProperties: false
+
+examples:
+  - |
+    kho {
+        compatible = "kho-v1";
+        preserved-memory-map = <0xf0be16 0x1000000>;
+
+        memblock {
+                fdt = <0x80cc16 0x1000000>;
+        };
+    };
diff --git a/Documentation/core-api/kho/bindings/memblock/memblock.yaml b/Documentation/core-api/kho/bindings/memblock/memblock.yaml
new file mode 100644
index 000000000000..d388c28eb91d
--- /dev/null
+++ b/Documentation/core-api/kho/bindings/memblock/memblock.yaml
@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+title: Memblock reserved memory
+
+maintainers:
+  - Mike Rapoport <rppt@kernel.org>
+
+description: |
+  Memblock can serialize its current memory reservations created with
+  reserve_mem command line option across kexec through KHO.
+  The post-KHO kernel can then consume these reservations and they are
+  guaranteed to have the same physical address.
+
+properties:
+  compatible:
+    enum:
+      - reserve-mem-v1
+
+patternProperties:
+  "$[0-9a-f_]+^":
+    $ref: reserve-mem.yaml#
+    description: reserved memory regions
+
+required:
+  - compatible
+
+additionalProperties: false
+
+examples:
+  - |
+    memblock {
+      compatible = "memblock-v1";
+      n1 {
+        compatible = "reserve-mem-v1";
+        start = <0xc06b 0x4000000>;
+        size = <0x04 0x00>;
+      };
+    };
diff --git a/Documentation/core-api/kho/bindings/memblock/reserve-mem.yaml b/Documentation/core-api/kho/bindings/memblock/reserve-mem.yaml
new file mode 100644
index 000000000000..10282d3d1bcd
--- /dev/null
+++ b/Documentation/core-api/kho/bindings/memblock/reserve-mem.yaml
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+title: Memblock reserved memory regions
+
+maintainers:
+  - Mike Rapoport <rppt@kernel.org>
+
+description: |
+  Memblock can serialize its current memory reservations created with
+  reserve_mem command line option across kexec through KHO.
+  This object describes each such region.
+
+properties:
+  compatible:
+    enum:
+      - reserve-mem-v1
+
+  start:
+    description: |
+      physical address (u64) of the reserved memory region.
+
+  size:
+    description: |
+      size (u64) of the reserved memory region.
+
+required:
+  - compatible
+  - start
+  - size
+
+additionalProperties: false
+
+examples:
+  - |
+    n1 {
+      compatible = "reserve-mem-v1";
+      start = <0xc06b 0x4000000>;
+      size = <0x04 0x00>;
+    };
diff --git a/Documentation/core-api/kho/bindings/sub-fdt.yaml b/Documentation/core-api/kho/bindings/sub-fdt.yaml
new file mode 100644
index 000000000000..b9a3d2d24850
--- /dev/null
+++ b/Documentation/core-api/kho/bindings/sub-fdt.yaml
@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+title: KHO users' FDT address
+
+maintainers:
+  - Mike Rapoport <rppt@kernel.org>
+  - Changyuan Lyu <changyuanl@google.com>
+
+description: |
+  Physical address of an FDT blob registered by a KHO user.
+
+properties:
+  fdt:
+    description: |
+      physical address (u64) of an FDT blob.
+
+required:
+  - fdt
+
+additionalProperties: false
+
+examples:
+  - |
+    memblock {
+            fdt = <0x80cc16 0x1000000>;
+    };
diff --git a/Documentation/core-api/kho/concepts.rst b/Documentation/core-api/kho/concepts.rst
new file mode 100644
index 000000000000..36d5c05cfb30
--- /dev/null
+++ b/Documentation/core-api/kho/concepts.rst
@@ -0,0 +1,74 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+.. _kho-concepts:
+
+=======================
+Kexec Handover Concepts
+=======================
+
+Kexec HandOver (KHO) is a mechanism that allows Linux to preserve memory
+regions, which could contain serialized system states, across kexec.
+
+It introduces multiple concepts:
+
+KHO FDT
+=======
+
+Every KHO kexec carries a KHO specific flattened device tree (FDT) blob
+that describes preserved memory regions. These regions contain either
+serialized subsystem states, or in-memory data that shall not be touched
+across kexec. After KHO, subsystems can retrieve and restore preserved
+memory regions from KHO FDT.
+
+KHO only uses the FDT container format and libfdt library, but does not
+adhere to the same property semantics that normal device trees do: Properties
+are passed in native endianness and standardized properties like ``regs`` and
+``ranges`` do not exist, hence there are no ``#...-cells`` properties.
+
+KHO is still under development. The FDT schema is unstable and would change
+in the future.
+
+Scratch Regions
+===============
+
+To boot into kexec, we need to have a physically contiguous memory range that
+contains no handed over memory. Kexec then places the target kernel and initrd
+into that region. The new kernel exclusively uses this region for memory
+allocations before during boot up to the initialization of the page allocator.
+
+We guarantee that we always have such regions through the scratch regions: On
+first boot KHO allocates several physically contiguous memory regions. Since
+after kexec these regions will be used by early memory allocations, there is a
+scratch region per NUMA node plus a scratch region to satisfy allocations
+requests that do not require particular NUMA node assignment.
+By default, size of the scratch region is calculated based on amount of memory
+allocated during boot. The ``kho_scratch`` kernel command line option may be
+used to explicitly define size of the scratch regions.
+The scratch regions are declared as CMA when page allocator is initialized so
+that their memory can be used during system lifetime. CMA gives us the
+guarantee that no handover pages land in that region, because handover pages
+must be at a static physical memory location and CMA enforces that only
+movable pages can be located inside.
+
+After KHO kexec, we ignore the ``kho_scratch`` kernel command line option and
+instead reuse the exact same region that was originally allocated. This allows
+us to recursively execute any amount of KHO kexecs. Because we used this region
+for boot memory allocations and as target memory for kexec blobs, some parts
+of that memory region may be reserved. These reservations are irrelevant for
+the next KHO, because kexec can overwrite even the original kernel.
+
+.. _kho-finalization-phase:
+
+KHO finalization phase
+======================
+
+To enable user space based kexec file loader, the kernel needs to be able to
+provide the FDT that describes the current kernel's state before
+performing the actual kexec. The process of generating that FDT is
+called serialization. When the FDT is generated, some properties
+of the system may become immutable because they are already written down
+in the FDT. That state is called the KHO finalization phase.
+
+Public API
+==========
+.. kernel-doc:: kernel/kexec_handover.c
+   :export:
diff --git a/Documentation/core-api/kho/fdt.rst b/Documentation/core-api/kho/fdt.rst
new file mode 100644
index 000000000000..62505285d60d
--- /dev/null
+++ b/Documentation/core-api/kho/fdt.rst
@@ -0,0 +1,80 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+=======
+KHO FDT
+=======
+
+KHO uses the flattened device tree (FDT) container format and libfdt
+library to create and parse the data that is passed between the
+kernels. The properties in KHO FDT are stored in native format.
+It includes the physical address of an in-memory structure describing
+all preserved memory regions, as well as physical addresses of KHO users'
+own FDTs. Interpreting those sub FDTs is the responsibility of KHO users.
+
+KHO nodes and properties
+========================
+
+Property ``preserved-memory-map``
+---------------------------------
+
+KHO saves a special property named ``preserved-memory-map`` under the root node.
+This node contains the physical address of an in-memory structure for KHO to
+preserve memory regions across kexec.
+
+Property ``compatible``
+-----------------------
+
+The ``compatible`` property determines compatibility between the kernel
+that created the KHO FDT and the kernel that attempts to load it.
+If the kernel that loads the KHO FDT is not compatible with it, the entire
+KHO process will be bypassed.
+
+Property ``fdt``
+----------------
+
+Generally, a KHO user serialize its state into its own FDT and instructs
+KHO to preserve the underlying memory, such that after kexec, the new kernel
+can recover its state from the preserved FDT.
+
+A KHO user thus can create a node in KHO root tree and save the physical address
+of its own FDT in that node's property ``fdt`` .
+
+Examples
+========
+
+The following example demonstrates KHO FDT that preserves two memory
+regions created with ``reserve_mem`` kernel command line parameter::
+
+  /dts-v1/;
+
+  / {
+  	compatible = "kho-v1";
+
+	preserved-memory-map = <0x40be16 0x1000000>;
+
+  	memblock {
+		fdt = <0x1517 0x1000000>;
+  	};
+  };
+
+where the ``memblock`` node contains an FDT that is requested by the
+subsystem memblock for preservation. The FDT contains the following
+serialized data::
+
+  /dts-v1/;
+
+  / {
+  	compatible = "memblock-v1";
+
+  	n1 {
+  		compatible = "reserve-mem-v1";
+  		start = <0xc06b 0x4000000>;
+  		size = <0x04 0x00>;
+  	};
+
+  	n2 {
+  		compatible = "reserve-mem-v1";
+  		start = <0xc067 0x4000000>;
+  		size = <0x04 0x00>;
+  	};
+  };
diff --git a/Documentation/core-api/kho/index.rst b/Documentation/core-api/kho/index.rst
new file mode 100644
index 000000000000..0c63b0c5c143
--- /dev/null
+++ b/Documentation/core-api/kho/index.rst
@@ -0,0 +1,13 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+========================
+Kexec Handover Subsystem
+========================
+
+.. toctree::
+   :maxdepth: 1
+
+   concepts
+   fdt
+
+.. only::  subproject and html