Merge tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull non-MM updates from Andrew Morton:

 - "panic: sys_info: Refactor and fix a potential issue" (Andy Shevchenko)
   fixes a build issue and does some cleanup in ib/sys_info.c

 - "Implement mul_u64_u64_div_u64_roundup()" (David Laight)
   enhances the 64-bit math code on behalf of a PWM driver and beefs up
   the test module for these library functions

 - "scripts/gdb/symbols: make BPF debug info available to GDB" (Ilya Leoshkevich)
   makes BPF symbol names, sizes, and line numbers available to the GDB
   debugger

 - "Enable hung_task and lockup cases to dump system info on demand" (Feng Tang)
   adds a sysctl which can be used to cause additional info dumping when
   the hung-task and lockup detectors fire

 - "lib/base64: add generic encoder/decoder, migrate users" (Kuan-Wei Chiu)
   adds a general base64 encoder/decoder to lib/ and migrates several
   users away from their private implementations

 - "rbree: inline rb_first() and rb_last()" (Eric Dumazet)
   makes TCP a little faster

 - "liveupdate: Rework KHO for in-kernel users" (Pasha Tatashin)
   reworks the KEXEC Handover interfaces in preparation for Live Update
   Orchestrator (LUO), and possibly for other future clients

 - "kho: simplify state machine and enable dynamic updates" (Pasha Tatashin)
   increases the flexibility of KEXEC Handover. Also preparation for LUO

 - "Live Update Orchestrator" (Pasha Tatashin)
   is a major new feature targeted at cloud environments. Quoting the
   cover letter:

      This series introduces the Live Update Orchestrator, a kernel
      subsystem designed to facilitate live kernel updates using a
      kexec-based reboot. This capability is critical for cloud
      environments, allowing hypervisors to be updated with minimal
      downtime for running virtual machines. LUO achieves this by
      preserving the state of selected resources, such as memory,
      devices and their dependencies, across the kernel transition.

      As a key feature, this series includes support for preserving
      memfd file descriptors, which allows critical in-memory data, such
      as guest RAM or any other large memory region, to be maintained in
      RAM across the kexec reboot.

   Mike Rappaport merits a mention here, for his extensive review and
   testing work.

 - "kexec: reorganize kexec and kdump sysfs" (Sourabh Jain)
   moves the kexec and kdump sysfs entries from /sys/kernel/ to
   /sys/kernel/kexec/ and adds back-compatibility symlinks which can
   hopefully be removed one day

 - "kho: fixes for vmalloc restoration" (Mike Rapoport)
   fixes a BUG which was being hit during KHO restoration of vmalloc()
   regions

* tag 'mm-nonmm-stable-2025-12-06-11-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (139 commits)
  calibrate: update header inclusion
  Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()"
  vmcoreinfo: track and log recoverable hardware errors
  kho: fix restoring of contiguous ranges of order-0 pages
  kho: kho_restore_vmalloc: fix initialization of pages array
  MAINTAINERS: TPM DEVICE DRIVER: update the W-tag
  init: replace simple_strtoul with kstrtoul to improve lpj_setup
  KHO: fix boot failure due to kmemleak access to non-PRESENT pages
  Documentation/ABI: new kexec and kdump sysfs interface
  Documentation/ABI: mark old kexec sysfs deprecated
  kexec: move sysfs entries to /sys/kernel/kexec
  test_kho: always print restore status
  kho: free chunks using free_page() instead of kfree()
  selftests/liveupdate: add kexec test for multiple and empty sessions
  selftests/liveupdate: add simple kexec-based selftest for LUO
  selftests/liveupdate: add userspace API selftests
  docs: add documentation for memfd preservation via LUO
  mm: memfd_luo: allow preserving memfd
  liveupdate: luo_file: add private argument to store runtime state
  mm: shmem: export some functions to internal.h
  ...

1 files changed, 516 insertions, 0 deletions

diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
new file mode 100644
index 000000000000..4f6ba63b4310
--- /dev/null
+++ b/mm/memfd_luo.c
@@ -0,0 +1,516 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2025, Google LLC.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ *
+ * Copyright (C) 2025 Amazon.com Inc. or its affiliates.
+ * Pratyush Yadav <ptyadav@amazon.de>
+ */
+
+/**
+ * DOC: Memfd Preservation via LUO
+ *
+ * Overview
+ * ========
+ *
+ * Memory file descriptors (memfd) can be preserved over a kexec using the Live
+ * Update Orchestrator (LUO) file preservation. This allows userspace to
+ * transfer its memory contents to the next kernel after a kexec.
+ *
+ * The preservation is not intended to be transparent. Only select properties of
+ * the file are preserved. All others are reset to default. The preserved
+ * properties are described below.
+ *
+ * .. note::
+ *    The LUO API is not stabilized yet, so the preserved properties of a memfd
+ *    are also not stable and are subject to backwards incompatible changes.
+ *
+ * .. note::
+ *    Currently a memfd backed by Hugetlb is not supported. Memfds created
+ *    with ``MFD_HUGETLB`` will be rejected.
+ *
+ * Preserved Properties
+ * ====================
+ *
+ * The following properties of the memfd are preserved across kexec:
+ *
+ * File Contents
+ *   All data stored in the file is preserved.
+ *
+ * File Size
+ *   The size of the file is preserved. Holes in the file are filled by
+ *   allocating pages for them during preservation.
+ *
+ * File Position
+ *   The current file position is preserved, allowing applications to continue
+ *   reading/writing from their last position.
+ *
+ * File Status Flags
+ *   memfds are always opened with ``O_RDWR`` and ``O_LARGEFILE``. This property
+ *   is maintained.
+ *
+ * Non-Preserved Properties
+ * ========================
+ *
+ * All properties which are not preserved must be assumed to be reset to
+ * default. This section describes some of those properties which may be more of
+ * note.
+ *
+ * ``FD_CLOEXEC`` flag
+ *   A memfd can be created with the ``MFD_CLOEXEC`` flag that sets the
+ *   ``FD_CLOEXEC`` on the file. This flag is not preserved and must be set
+ *   again after restore via ``fcntl()``.
+ *
+ * Seals
+ *   File seals are not preserved. The file is unsealed on restore and if
+ *   needed, must be sealed again via ``fcntl()``.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/bits.h>
+#include <linux/err.h>
+#include <linux/file.h>
+#include <linux/io.h>
+#include <linux/kexec_handover.h>
+#include <linux/kho/abi/memfd.h>
+#include <linux/liveupdate.h>
+#include <linux/shmem_fs.h>
+#include <linux/vmalloc.h>
+#include "internal.h"
+
+static int memfd_luo_preserve_folios(struct file *file,
+				     struct kho_vmalloc *kho_vmalloc,
+				     struct memfd_luo_folio_ser **out_folios_ser,
+				     u64 *nr_foliosp)
+{
+	struct inode *inode = file_inode(file);
+	struct memfd_luo_folio_ser *folios_ser;
+	unsigned int max_folios;
+	long i, size, nr_pinned;
+	struct folio **folios;
+	int err = -EINVAL;
+	pgoff_t offset;
+	u64 nr_folios;
+
+	size = i_size_read(inode);
+	/*
+	 * If the file has zero size, then the folios and nr_folios properties
+	 * are not set.
+	 */
+	if (!size) {
+		*nr_foliosp = 0;
+		*out_folios_ser = NULL;
+		memset(kho_vmalloc, 0, sizeof(*kho_vmalloc));
+		return 0;
+	}
+
+	/*
+	 * Guess the number of folios based on inode size. Real number might end
+	 * up being smaller if there are higher order folios.
+	 */
+	max_folios = PAGE_ALIGN(size) / PAGE_SIZE;
+	folios = kvmalloc_array(max_folios, sizeof(*folios), GFP_KERNEL);
+	if (!folios)
+		return -ENOMEM;
+
+	/*
+	 * Pin the folios so they don't move around behind our back. This also
+	 * ensures none of the folios are in CMA -- which ensures they don't
+	 * fall in KHO scratch memory. It also moves swapped out folios back to
+	 * memory.
+	 *
+	 * A side effect of doing this is that it allocates a folio for all
+	 * indices in the file. This might waste memory on sparse memfds. If
+	 * that is really a problem in the future, we can have a
+	 * memfd_pin_folios() variant that does not allocate a page on empty
+	 * slots.
+	 */
+	nr_pinned = memfd_pin_folios(file, 0, size - 1, folios, max_folios,
+				     &offset);
+	if (nr_pinned < 0) {
+		err = nr_pinned;
+		pr_err("failed to pin folios: %d\n", err);
+		goto err_free_folios;
+	}
+	nr_folios = nr_pinned;
+
+	folios_ser = vcalloc(nr_folios, sizeof(*folios_ser));
+	if (!folios_ser) {
+		err = -ENOMEM;
+		goto err_unpin;
+	}
+
+	for (i = 0; i < nr_folios; i++) {
+		struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+		struct folio *folio = folios[i];
+		unsigned int flags = 0;
+
+		err = kho_preserve_folio(folio);
+		if (err)
+			goto err_unpreserve;
+
+		if (folio_test_dirty(folio))
+			flags |= MEMFD_LUO_FOLIO_DIRTY;
+		if (folio_test_uptodate(folio))
+			flags |= MEMFD_LUO_FOLIO_UPTODATE;
+
+		pfolio->pfn = folio_pfn(folio);
+		pfolio->flags = flags;
+		pfolio->index = folio->index;
+	}
+
+	err = kho_preserve_vmalloc(folios_ser, kho_vmalloc);
+	if (err)
+		goto err_unpreserve;
+
+	kvfree(folios);
+	*nr_foliosp = nr_folios;
+	*out_folios_ser = folios_ser;
+
+	/*
+	 * Note: folios_ser is purposely not freed here. It is preserved
+	 * memory (via KHO). In the 'unpreserve' path, we use the vmap pointer
+	 * that is passed via private_data.
+	 */
+	return 0;
+
+err_unpreserve:
+	for (i = i - 1; i >= 0; i--)
+		kho_unpreserve_folio(folios[i]);
+	vfree(folios_ser);
+err_unpin:
+	unpin_folios(folios, nr_folios);
+err_free_folios:
+	kvfree(folios);
+
+	return err;
+}
+
+static void memfd_luo_unpreserve_folios(struct kho_vmalloc *kho_vmalloc,
+					struct memfd_luo_folio_ser *folios_ser,
+					u64 nr_folios)
+{
+	long i;
+
+	if (!nr_folios)
+		return;
+
+	kho_unpreserve_vmalloc(kho_vmalloc);
+
+	for (i = 0; i < nr_folios; i++) {
+		const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+		struct folio *folio;
+
+		if (!pfolio->pfn)
+			continue;
+
+		folio = pfn_folio(pfolio->pfn);
+
+		kho_unpreserve_folio(folio);
+		unpin_folio(folio);
+	}
+
+	vfree(folios_ser);
+}
+
+static int memfd_luo_preserve(struct liveupdate_file_op_args *args)
+{
+	struct inode *inode = file_inode(args->file);
+	struct memfd_luo_folio_ser *folios_ser;
+	struct memfd_luo_ser *ser;
+	u64 nr_folios;
+	int err = 0;
+
+	inode_lock(inode);
+	shmem_freeze(inode, true);
+
+	/* Allocate the main serialization structure in preserved memory */
+	ser = kho_alloc_preserve(sizeof(*ser));
+	if (IS_ERR(ser)) {
+		err = PTR_ERR(ser);
+		goto err_unlock;
+	}
+
+	ser->pos = args->file->f_pos;
+	ser->size = i_size_read(inode);
+
+	err = memfd_luo_preserve_folios(args->file, &ser->folios,
+					&folios_ser, &nr_folios);
+	if (err)
+		goto err_free_ser;
+
+	ser->nr_folios = nr_folios;
+	inode_unlock(inode);
+
+	args->private_data = folios_ser;
+	args->serialized_data = virt_to_phys(ser);
+
+	return 0;
+
+err_free_ser:
+	kho_unpreserve_free(ser);
+err_unlock:
+	shmem_freeze(inode, false);
+	inode_unlock(inode);
+	return err;
+}
+
+static int memfd_luo_freeze(struct liveupdate_file_op_args *args)
+{
+	struct memfd_luo_ser *ser;
+
+	if (WARN_ON_ONCE(!args->serialized_data))
+		return -EINVAL;
+
+	ser = phys_to_virt(args->serialized_data);
+
+	/*
+	 * The pos might have changed since prepare. Everything else stays the
+	 * same.
+	 */
+	ser->pos = args->file->f_pos;
+
+	return 0;
+}
+
+static void memfd_luo_unpreserve(struct liveupdate_file_op_args *args)
+{
+	struct inode *inode = file_inode(args->file);
+	struct memfd_luo_ser *ser;
+
+	if (WARN_ON_ONCE(!args->serialized_data))
+		return;
+
+	inode_lock(inode);
+	shmem_freeze(inode, false);
+
+	ser = phys_to_virt(args->serialized_data);
+
+	memfd_luo_unpreserve_folios(&ser->folios, args->private_data,
+				    ser->nr_folios);
+
+	kho_unpreserve_free(ser);
+	inode_unlock(inode);
+}
+
+static void memfd_luo_discard_folios(const struct memfd_luo_folio_ser *folios_ser,
+				     u64 nr_folios)
+{
+	u64 i;
+
+	for (i = 0; i < nr_folios; i++) {
+		const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+		struct folio *folio;
+		phys_addr_t phys;
+
+		if (!pfolio->pfn)
+			continue;
+
+		phys = PFN_PHYS(pfolio->pfn);
+		folio = kho_restore_folio(phys);
+		if (!folio) {
+			pr_warn_ratelimited("Unable to restore folio at physical address: %llx\n",
+					    phys);
+			continue;
+		}
+
+		folio_put(folio);
+	}
+}
+
+static void memfd_luo_finish(struct liveupdate_file_op_args *args)
+{
+	struct memfd_luo_folio_ser *folios_ser;
+	struct memfd_luo_ser *ser;
+
+	if (args->retrieved)
+		return;
+
+	ser = phys_to_virt(args->serialized_data);
+	if (!ser)
+		return;
+
+	if (ser->nr_folios) {
+		folios_ser = kho_restore_vmalloc(&ser->folios);
+		if (!folios_ser)
+			goto out;
+
+		memfd_luo_discard_folios(folios_ser, ser->nr_folios);
+		vfree(folios_ser);
+	}
+
+out:
+	kho_restore_free(ser);
+}
+
+static int memfd_luo_retrieve_folios(struct file *file,
+				     struct memfd_luo_folio_ser *folios_ser,
+				     u64 nr_folios)
+{
+	struct inode *inode = file_inode(file);
+	struct address_space *mapping = inode->i_mapping;
+	struct folio *folio;
+	int err = -EIO;
+	long i;
+
+	for (i = 0; i < nr_folios; i++) {
+		const struct memfd_luo_folio_ser *pfolio = &folios_ser[i];
+		phys_addr_t phys;
+		u64 index;
+		int flags;
+
+		if (!pfolio->pfn)
+			continue;
+
+		phys = PFN_PHYS(pfolio->pfn);
+		folio = kho_restore_folio(phys);
+		if (!folio) {
+			pr_err("Unable to restore folio at physical address: %llx\n",
+			       phys);
+			goto put_folios;
+		}
+		index = pfolio->index;
+		flags = pfolio->flags;
+
+		/* Set up the folio for insertion. */
+		__folio_set_locked(folio);
+		__folio_set_swapbacked(folio);
+
+		err = mem_cgroup_charge(folio, NULL, mapping_gfp_mask(mapping));
+		if (err) {
+			pr_err("shmem: failed to charge folio index %ld: %d\n",
+			       i, err);
+			goto unlock_folio;
+		}
+
+		err = shmem_add_to_page_cache(folio, mapping, index, NULL,
+					      mapping_gfp_mask(mapping));
+		if (err) {
+			pr_err("shmem: failed to add to page cache folio index %ld: %d\n",
+			       i, err);
+			goto unlock_folio;
+		}
+
+		if (flags & MEMFD_LUO_FOLIO_UPTODATE)
+			folio_mark_uptodate(folio);
+		if (flags & MEMFD_LUO_FOLIO_DIRTY)
+			folio_mark_dirty(folio);
+
+		err = shmem_inode_acct_blocks(inode, 1);
+		if (err) {
+			pr_err("shmem: failed to account folio index %ld: %d\n",
+			       i, err);
+			goto unlock_folio;
+		}
+
+		shmem_recalc_inode(inode, 1, 0);
+		folio_add_lru(folio);
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+
+	return 0;
+
+unlock_folio:
+	folio_unlock(folio);
+	folio_put(folio);
+put_folios:
+	/*
+	 * Note: don't free the folios already added to the file. They will be
+	 * freed when the file is freed. Free the ones not added yet here.
+	 */
+	for (long j = i + 1; j < nr_folios; j++) {
+		const struct memfd_luo_folio_ser *pfolio = &folios_ser[j];
+
+		folio = kho_restore_folio(pfolio->pfn);
+		if (folio)
+			folio_put(folio);
+	}
+
+	return err;
+}
+
+static int memfd_luo_retrieve(struct liveupdate_file_op_args *args)
+{
+	struct memfd_luo_folio_ser *folios_ser;
+	struct memfd_luo_ser *ser;
+	struct file *file;
+	int err;
+
+	ser = phys_to_virt(args->serialized_data);
+	if (!ser)
+		return -EINVAL;
+
+	file = shmem_file_setup("", 0, VM_NORESERVE);
+
+	if (IS_ERR(file)) {
+		pr_err("failed to setup file: %pe\n", file);
+		return PTR_ERR(file);
+	}
+
+	vfs_setpos(file, ser->pos, MAX_LFS_FILESIZE);
+	file->f_inode->i_size = ser->size;
+
+	if (ser->nr_folios) {
+		folios_ser = kho_restore_vmalloc(&ser->folios);
+		if (!folios_ser) {
+			err = -EINVAL;
+			goto put_file;
+		}
+
+		err = memfd_luo_retrieve_folios(file, folios_ser, ser->nr_folios);
+		vfree(folios_ser);
+		if (err)
+			goto put_file;
+	}
+
+	args->file = file;
+	kho_restore_free(ser);
+
+	return 0;
+
+put_file:
+	fput(file);
+
+	return err;
+}
+
+static bool memfd_luo_can_preserve(struct liveupdate_file_handler *handler,
+				   struct file *file)
+{
+	struct inode *inode = file_inode(file);
+
+	return shmem_file(file) && !inode->i_nlink;
+}
+
+static const struct liveupdate_file_ops memfd_luo_file_ops = {
+	.freeze = memfd_luo_freeze,
+	.finish = memfd_luo_finish,
+	.retrieve = memfd_luo_retrieve,
+	.preserve = memfd_luo_preserve,
+	.unpreserve = memfd_luo_unpreserve,
+	.can_preserve = memfd_luo_can_preserve,
+	.owner = THIS_MODULE,
+};
+
+static struct liveupdate_file_handler memfd_luo_handler = {
+	.ops = &memfd_luo_file_ops,
+	.compatible = MEMFD_LUO_FH_COMPATIBLE,
+};
+
+static int __init memfd_luo_init(void)
+{
+	int err = liveupdate_register_file_handler(&memfd_luo_handler);
+
+	if (err && err != -EOPNOTSUPP) {
+		pr_err("Could not register luo filesystem handler: %pe\n",
+		       ERR_PTR(err));
+
+		return err;
+	}
+
+	return 0;
+}
+late_initcall(memfd_luo_init);