* + liveupdate-kho-move-to-kernel-liveupdate.patch added to mm-nonmm-unstable branch
@ 2025-10-09 2:15 Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2025-10-09 2:15 UTC (permalink / raw)
To: mm-commits, tj, rppt, rdunlap, pratyush, ojeda, masahiroy, jgg,
jgg, graf, corbet, brauner, pasha.tatashin, akpm
The patch titled
Subject: liveupdate: kho: move to kernel/liveupdate
has been added to the -mm mm-nonmm-unstable branch. Its filename is
liveupdate-kho-move-to-kernel-liveupdate.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/liveupdate-kho-move-to-kernel-liveupdate.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: liveupdate: kho: move to kernel/liveupdate
Date: Tue, 7 Oct 2025 03:30:59 +0000
Move KHO to kernel/liveupdate/ in preparation of placing all Live Update
core kernel related files to the same place.
Link: https://lkml.kernel.org/r/20251007033100.836886-7-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
Documentation/core-api/kho/concepts.rst | 2
MAINTAINERS | 2
init/Kconfig | 2
kernel/Kconfig.kexec | 25
kernel/Makefile | 3
kernel/kexec_handover.c | 1510 ------------------
kernel/kexec_handover_debug.c | 216 --
kernel/kexec_handover_internal.h | 45
kernel/liveupdate/Kconfig | 30
kernel/liveupdate/Makefile | 4
kernel/liveupdate/kexec_handover.c | 1510 ++++++++++++++++++
kernel/liveupdate/kexec_handover_debug.c | 216 ++
kernel/liveupdate/kexec_handover_internal.h | 45
13 files changed, 1810 insertions(+), 1800 deletions(-)
--- a/Documentation/core-api/kho/concepts.rst~liveupdate-kho-move-to-kernel-liveupdate
+++ a/Documentation/core-api/kho/concepts.rst
@@ -70,5 +70,5 @@ in the FDT. That state is called the KHO
Public API
==========
-.. kernel-doc:: kernel/kexec_handover.c
+.. kernel-doc:: kernel/liveupdate/kexec_handover.c
:export:
--- a/init/Kconfig~liveupdate-kho-move-to-kernel-liveupdate
+++ a/init/Kconfig
@@ -2138,6 +2138,8 @@ config TRACEPOINTS
source "kernel/Kconfig.kexec"
+source "kernel/liveupdate/Kconfig"
+
endmenu # General setup
source "arch/Kconfig"
--- a/kernel/Kconfig.kexec~liveupdate-kho-move-to-kernel-liveupdate
+++ a/kernel/Kconfig.kexec
@@ -94,31 +94,6 @@ config KEXEC_JUMP
Jump between original kernel and kexeced kernel and invoke
code in physical address mode via KEXEC
-config KEXEC_HANDOVER
- bool "kexec handover"
- depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
- depends on !DEFERRED_STRUCT_PAGE_INIT
- select MEMBLOCK_KHO_SCRATCH
- select KEXEC_FILE
- select DEBUG_FS
- select LIBFDT
- select CMA
- help
- Allow kexec to hand over state across kernels by generating and
- passing additional metadata to the target kernel. This is useful
- to keep data or state alive across the kexec. For this to work,
- both source and target kernels need to have this option enabled.
-
-config KEXEC_HANDOVER_DEBUGFS
- bool "kexec handover debugfs interface"
- depends on KEXEC_HANDOVER
- depends on DEBUG_FS
- help
- Allow to control kexec handover device tree via debugfs
- interface, i.e. finalize the state or aborting the finalization.
- Also, enables inspecting the KHO fdt trees with the debugfs binary
- blobs.
-
config CRASH_DUMP
bool "kernel crash dumps"
default ARCH_DEFAULT_CRASH_DUMP
diff --git a/kernel/kexec_handover.c a/kernel/kexec_handover.c
deleted file mode 100644
--- a/kernel/kexec_handover.c
+++ /dev/null
@@ -1,1510 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover.c - kexec handover metadata processing
- * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
- * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
- * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include <linux/cma.h>
-#include <linux/count_zeros.h>
-#include <linux/kexec.h>
-#include <linux/kexec_handover.h>
-#include <linux/libfdt.h>
-#include <linux/list.h>
-#include <linux/memblock.h>
-#include <linux/page-isolation.h>
-#include <linux/vmalloc.h>
-
-#include <asm/early_ioremap.h>
-
-/*
- * KHO is tightly coupled with mm init and needs access to some of mm
- * internal APIs.
- */
-#include "../mm/internal.h"
-#include "kexec_internal.h"
-#include "kexec_handover_internal.h"
-
-#define KHO_FDT_COMPATIBLE "kho-v1"
-#define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
-#define PROP_SUB_FDT "fdt"
-
-#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
-
-/*
- * KHO uses page->private, which is an unsigned long, to store page metadata.
- * Use it to store both the magic and the order.
- */
-union kho_page_info {
- unsigned long page_private;
- struct {
- unsigned int order;
- unsigned int magic;
- };
-};
-
-static_assert(sizeof(union kho_page_info) == sizeof(((struct page *)0)->private));
-
-static bool kho_enable __ro_after_init;
-
-bool kho_is_enabled(void)
-{
- return kho_enable;
-}
-EXPORT_SYMBOL_GPL(kho_is_enabled);
-
-static int __init kho_parse_enable(char *p)
-{
- return kstrtobool(p, &kho_enable);
-}
-early_param("kho", kho_parse_enable);
-
-/*
- * Keep track of memory that is to be preserved across KHO.
- *
- * The serializing side uses two levels of xarrays to manage chunks of per-order
- * 512 byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order of a
- * 1TB system would fit inside a single 512 byte bitmap. For order 0 allocations
- * each bitmap will cover 16M of address space. Thus, for 16G of memory at most
- * 512K of bitmap memory will be needed for order 0.
- *
- * This approach is fully incremental, as the serialization progresses folios
- * can continue be aggregated to the tracker. The final step, immediately prior
- * to kexec would serialize the xarray information into a linked list for the
- * successor kernel to parse.
- */
-
-#define PRESERVE_BITS (512 * 8)
-
-struct kho_mem_phys_bits {
- DECLARE_BITMAP(preserve, PRESERVE_BITS);
-};
-
-struct kho_mem_phys {
- /*
- * Points to kho_mem_phys_bits, a sparse bitmap array. Each bit is sized
- * to order.
- */
- struct xarray phys_bits;
-};
-
-struct kho_mem_track {
- /* Points to kho_mem_phys, each order gets its own bitmap tree */
- struct xarray orders;
-};
-
-struct khoser_mem_chunk;
-
-struct kho_sub_fdt {
- struct list_head l;
- const char *name;
- void *fdt;
-};
-
-struct kho_out {
- void *fdt;
- bool finalized;
- struct mutex lock; /* protects KHO FDT finalization */
-
- struct list_head sub_fdts;
- struct mutex fdts_lock;
-
- struct kho_mem_track track;
- /* First chunk of serialized preserved memory map */
- struct khoser_mem_chunk *preserved_mem_map;
-
- struct kho_debugfs dbg;
-};
-
-static struct kho_out kho_out = {
- .lock = __MUTEX_INITIALIZER(kho_out.lock),
- .track = {
- .orders = XARRAY_INIT(kho_out.track.orders, 0),
- },
- .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts),
- .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock),
- .finalized = false,
-};
-
-static void *xa_load_or_alloc(struct xarray *xa, unsigned long index, size_t sz)
-{
- void *elm, *res;
-
- elm = xa_load(xa, index);
- if (elm)
- return elm;
-
- elm = kzalloc(sz, GFP_KERNEL);
- if (!elm)
- return ERR_PTR(-ENOMEM);
-
- res = xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
- if (xa_is_err(res))
- res = ERR_PTR(xa_err(res));
-
- if (res) {
- kfree(elm);
- return res;
- }
-
- return elm;
-}
-
-static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn,
- unsigned int order)
-{
- struct kho_mem_phys_bits *bits;
- struct kho_mem_phys *physxa;
- const unsigned long pfn_high = pfn >> order;
-
- physxa = xa_load(&track->orders, order);
- if (!physxa)
- return;
-
- bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
- if (!bits)
- return;
-
- clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
-}
-
-static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
- unsigned long end_pfn)
-{
- unsigned int order;
-
- while (pfn < end_pfn) {
- order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
- __kho_unpreserve_order(track, pfn, order);
-
- pfn += 1 << order;
- }
-}
-
-static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
- unsigned int order)
-{
- struct kho_mem_phys_bits *bits;
- struct kho_mem_phys *physxa, *new_physxa;
- const unsigned long pfn_high = pfn >> order;
-
- might_sleep();
-
- if (kho_out.finalized)
- return -EBUSY;
-
- physxa = xa_load(&track->orders, order);
- if (!physxa) {
- int err;
-
- new_physxa = kzalloc(sizeof(*physxa), GFP_KERNEL);
- if (!new_physxa)
- return -ENOMEM;
-
- xa_init(&new_physxa->phys_bits);
- physxa = xa_cmpxchg(&track->orders, order, NULL, new_physxa,
- GFP_KERNEL);
-
- err = xa_err(physxa);
- if (err || physxa) {
- xa_destroy(&new_physxa->phys_bits);
- kfree(new_physxa);
-
- if (err)
- return err;
- } else {
- physxa = new_physxa;
- }
- }
-
- bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS,
- sizeof(*bits));
- if (IS_ERR(bits))
- return PTR_ERR(bits);
-
- set_bit(pfn_high % PRESERVE_BITS, bits->preserve);
-
- return 0;
-}
-
-static struct page *kho_restore_page(phys_addr_t phys)
-{
- struct page *page = pfn_to_online_page(PHYS_PFN(phys));
- union kho_page_info info;
- unsigned int nr_pages;
-
- if (!page)
- return NULL;
-
- info.page_private = page->private;
- /*
- * deserialize_bitmap() only sets the magic on the head page. This magic
- * check also implicitly makes sure phys is order-aligned since for
- * non-order-aligned phys addresses, magic will never be set.
- */
- if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER))
- return NULL;
- nr_pages = (1 << info.order);
-
- /* Clear private to make sure later restores on this page error out. */
- page->private = 0;
- /* Head page gets refcount of 1. */
- set_page_count(page, 1);
-
- /* For higher order folios, tail pages get a page count of zero. */
- for (unsigned int i = 1; i < nr_pages; i++)
- set_page_count(page + i, 0);
-
- if (info.order > 0)
- prep_compound_page(page, info.order);
-
- adjust_managed_page_count(page, nr_pages);
- return page;
-}
-
-/**
- * kho_restore_folio - recreates the folio from the preserved memory.
- * @phys: physical address of the folio.
- *
- * Return: pointer to the struct folio on success, NULL on failure.
- */
-struct folio *kho_restore_folio(phys_addr_t phys)
-{
- struct page *page = kho_restore_page(phys);
-
- return page ? page_folio(page) : NULL;
-}
-EXPORT_SYMBOL_GPL(kho_restore_folio);
-
-/**
- * kho_restore_pages - restore list of contiguous order 0 pages.
- * @phys: physical address of the first page.
- * @nr_pages: number of pages.
- *
- * Restore a contiguous list of order 0 pages that was preserved with
- * kho_preserve_pages().
- *
- * Return: 0 on success, error code on failure
- */
-struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages)
-{
- const unsigned long start_pfn = PHYS_PFN(phys);
- const unsigned long end_pfn = start_pfn + nr_pages;
- unsigned long pfn = start_pfn;
-
- while (pfn < end_pfn) {
- const unsigned int order =
- min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
- struct page *page = kho_restore_page(PFN_PHYS(pfn));
-
- if (!page)
- return NULL;
- split_page(page, order);
- pfn += 1 << order;
- }
-
- return pfn_to_page(start_pfn);
-}
-EXPORT_SYMBOL_GPL(kho_restore_pages);
-
-/* Serialize and deserialize struct kho_mem_phys across kexec
- *
- * Record all the bitmaps in a linked list of pages for the next kernel to
- * process. Each chunk holds bitmaps of the same order and each block of bitmaps
- * starts at a given physical address. This allows the bitmaps to be sparse. The
- * xarray is used to store them in a tree while building up the data structure,
- * but the KHO successor kernel only needs to process them once in order.
- *
- * All of this memory is normal kmalloc() memory and is not marked for
- * preservation. The successor kernel will remain isolated to the scratch space
- * until it completes processing this list. Once processed all the memory
- * storing these ranges will be marked as free.
- */
-
-struct khoser_mem_bitmap_ptr {
- phys_addr_t phys_start;
- DECLARE_KHOSER_PTR(bitmap, struct kho_mem_phys_bits *);
-};
-
-struct khoser_mem_chunk_hdr {
- DECLARE_KHOSER_PTR(next, struct khoser_mem_chunk *);
- unsigned int order;
- unsigned int num_elms;
-};
-
-#define KHOSER_BITMAP_SIZE \
- ((PAGE_SIZE - sizeof(struct khoser_mem_chunk_hdr)) / \
- sizeof(struct khoser_mem_bitmap_ptr))
-
-struct khoser_mem_chunk {
- struct khoser_mem_chunk_hdr hdr;
- struct khoser_mem_bitmap_ptr bitmaps[KHOSER_BITMAP_SIZE];
-};
-
-static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE);
-
-static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk,
- unsigned long order)
-{
- struct khoser_mem_chunk *chunk;
-
- chunk = kzalloc(PAGE_SIZE, GFP_KERNEL);
- if (!chunk)
- return NULL;
- chunk->hdr.order = order;
- if (cur_chunk)
- KHOSER_STORE_PTR(cur_chunk->hdr.next, chunk);
- return chunk;
-}
-
-static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
-{
- struct khoser_mem_chunk *chunk = first_chunk;
-
- while (chunk) {
- struct khoser_mem_chunk *tmp = chunk;
-
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- kfree(tmp);
- }
-}
-
-static int kho_mem_serialize(struct kho_out *kho_out)
-{
- struct khoser_mem_chunk *first_chunk = NULL;
- struct khoser_mem_chunk *chunk = NULL;
- struct kho_mem_phys *physxa;
- unsigned long order;
-
- xa_for_each(&kho_out->track.orders, order, physxa) {
- struct kho_mem_phys_bits *bits;
- unsigned long phys;
-
- chunk = new_chunk(chunk, order);
- if (!chunk)
- goto err_free;
-
- if (!first_chunk)
- first_chunk = chunk;
-
- xa_for_each(&physxa->phys_bits, phys, bits) {
- struct khoser_mem_bitmap_ptr *elm;
-
- if (chunk->hdr.num_elms == ARRAY_SIZE(chunk->bitmaps)) {
- chunk = new_chunk(chunk, order);
- if (!chunk)
- goto err_free;
- }
-
- elm = &chunk->bitmaps[chunk->hdr.num_elms];
- chunk->hdr.num_elms++;
- elm->phys_start = (phys * PRESERVE_BITS)
- << (order + PAGE_SHIFT);
- KHOSER_STORE_PTR(elm->bitmap, bits);
- }
- }
-
- kho_out->preserved_mem_map = first_chunk;
-
- return 0;
-
-err_free:
- kho_mem_ser_free(first_chunk);
- return -ENOMEM;
-}
-
-static void __init deserialize_bitmap(unsigned int order,
- struct khoser_mem_bitmap_ptr *elm)
-{
- struct kho_mem_phys_bits *bitmap = KHOSER_LOAD_PTR(elm->bitmap);
- unsigned long bit;
-
- for_each_set_bit(bit, bitmap->preserve, PRESERVE_BITS) {
- int sz = 1 << (order + PAGE_SHIFT);
- phys_addr_t phys =
- elm->phys_start + (bit << (order + PAGE_SHIFT));
- struct page *page = phys_to_page(phys);
- union kho_page_info info;
-
- memblock_reserve(phys, sz);
- memblock_reserved_mark_noinit(phys, sz);
- info.magic = KHO_PAGE_MAGIC;
- info.order = order;
- page->private = info.page_private;
- }
-}
-
-static void __init kho_mem_deserialize(const void *fdt)
-{
- struct khoser_mem_chunk *chunk;
- const phys_addr_t *mem;
- int len;
-
- mem = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
-
- if (!mem || len != sizeof(*mem)) {
- pr_err("failed to get preserved memory bitmaps\n");
- return;
- }
-
- chunk = *mem ? phys_to_virt(*mem) : NULL;
- while (chunk) {
- unsigned int i;
-
- for (i = 0; i != chunk->hdr.num_elms; i++)
- deserialize_bitmap(chunk->hdr.order,
- &chunk->bitmaps[i]);
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- }
-}
-
-/*
- * With KHO enabled, memory can become fragmented because KHO regions may
- * be anywhere in physical address space. The scratch regions give us a
- * safe zones that we will never see KHO allocations from. This is where we
- * can later safely load our new kexec images into and then use the scratch
- * area for early allocations that happen before page allocator is
- * initialized.
- */
-struct kho_scratch *kho_scratch;
-unsigned int kho_scratch_cnt;
-
-/*
- * The scratch areas are scaled by default as percent of memory allocated from
- * memblock. A user can override the scale with command line parameter:
- *
- * kho_scratch=N%
- *
- * It is also possible to explicitly define size for a lowmem, a global and
- * per-node scratch areas:
- *
- * kho_scratch=l[KMG],n[KMG],m[KMG]
- *
- * The explicit size definition takes precedence over scale definition.
- */
-static unsigned int scratch_scale __initdata = 200;
-static phys_addr_t scratch_size_global __initdata;
-static phys_addr_t scratch_size_pernode __initdata;
-static phys_addr_t scratch_size_lowmem __initdata;
-
-static int __init kho_parse_scratch_size(char *p)
-{
- size_t len;
- unsigned long sizes[3];
- size_t total_size = 0;
- int i;
-
- if (!p)
- return -EINVAL;
-
- len = strlen(p);
- if (!len)
- return -EINVAL;
-
- /* parse nn% */
- if (p[len - 1] == '%') {
- /* unsigned int max is 4,294,967,295, 10 chars */
- char s_scale[11] = {};
- int ret = 0;
-
- if (len > ARRAY_SIZE(s_scale))
- return -EINVAL;
-
- memcpy(s_scale, p, len - 1);
- ret = kstrtouint(s_scale, 10, &scratch_scale);
- if (!ret)
- pr_notice("scratch scale is %d%%\n", scratch_scale);
- return ret;
- }
-
- /* parse ll[KMG],mm[KMG],nn[KMG] */
- for (i = 0; i < ARRAY_SIZE(sizes); i++) {
- char *endp = p;
-
- if (i > 0) {
- if (*p != ',')
- return -EINVAL;
- p += 1;
- }
-
- sizes[i] = memparse(p, &endp);
- if (endp == p)
- return -EINVAL;
- p = endp;
- total_size += sizes[i];
- }
-
- if (!total_size)
- return -EINVAL;
-
- /* The string should be fully consumed by now. */
- if (*p)
- return -EINVAL;
-
- scratch_size_lowmem = sizes[0];
- scratch_size_global = sizes[1];
- scratch_size_pernode = sizes[2];
- scratch_scale = 0;
-
- pr_notice("scratch areas: lowmem: %lluMiB global: %lluMiB pernode: %lldMiB\n",
- (u64)(scratch_size_lowmem >> 20),
- (u64)(scratch_size_global >> 20),
- (u64)(scratch_size_pernode >> 20));
-
- return 0;
-}
-early_param("kho_scratch", kho_parse_scratch_size);
-
-static void __init scratch_size_update(void)
-{
- phys_addr_t size;
-
- if (!scratch_scale)
- return;
-
- size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
- NUMA_NO_NODE);
- size = size * scratch_scale / 100;
- scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-
- size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
- NUMA_NO_NODE);
- size = size * scratch_scale / 100 - scratch_size_lowmem;
- scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-}
-
-static phys_addr_t __init scratch_size_node(int nid)
-{
- phys_addr_t size;
-
- if (scratch_scale) {
- size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
- nid);
- size = size * scratch_scale / 100;
- } else {
- size = scratch_size_pernode;
- }
-
- return round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-}
-
-/**
- * kho_reserve_scratch - Reserve a contiguous chunk of memory for kexec
- *
- * With KHO we can preserve arbitrary pages in the system. To ensure we still
- * have a large contiguous region of memory when we search the physical address
- * space for target memory, let's make sure we always have a large CMA region
- * active. This CMA region will only be used for movable pages which are not a
- * problem for us during KHO because we can just move them somewhere else.
- */
-static void __init kho_reserve_scratch(void)
-{
- phys_addr_t addr, size;
- int nid, i = 0;
-
- if (!kho_enable)
- return;
-
- scratch_size_update();
-
- /* FIXME: deal with node hot-plug/remove */
- kho_scratch_cnt = num_online_nodes() + 2;
- size = kho_scratch_cnt * sizeof(*kho_scratch);
- kho_scratch = memblock_alloc(size, PAGE_SIZE);
- if (!kho_scratch)
- goto err_disable_kho;
-
- /*
- * reserve scratch area in low memory for lowmem allocations in the
- * next kernel
- */
- size = scratch_size_lowmem;
- addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0,
- ARCH_LOW_ADDRESS_LIMIT);
- if (!addr)
- goto err_free_scratch_desc;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
-
- /* reserve large contiguous area for allocations without nid */
- size = scratch_size_global;
- addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES);
- if (!addr)
- goto err_free_scratch_areas;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
-
- for_each_online_node(nid) {
- size = scratch_size_node(nid);
- addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
- 0, MEMBLOCK_ALLOC_ACCESSIBLE,
- nid, true);
- if (!addr)
- goto err_free_scratch_areas;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
- }
-
- return;
-
-err_free_scratch_areas:
- for (i--; i >= 0; i--)
- memblock_phys_free(kho_scratch[i].addr, kho_scratch[i].size);
-err_free_scratch_desc:
- memblock_free(kho_scratch, kho_scratch_cnt * sizeof(*kho_scratch));
-err_disable_kho:
- pr_warn("Failed to reserve scratch area, disabling kexec handover\n");
- kho_enable = false;
-}
-
-/**
- * kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
- * @name: name of the sub tree.
- * @fdt: the sub tree blob.
- *
- * Creates a new child node named @name in KHO root FDT and records
- * the physical address of @fdt. The pages of @fdt must also be preserved
- * by KHO for the new kernel to retrieve it after kexec.
- *
- * A debugfs blob entry is also created at
- * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured with
- * CONFIG_KEXEC_HANDOVER_DEBUGFS
- *
- * Return: 0 on success, error code on failure
- */
-int kho_add_subtree(const char *name, void *fdt)
-{
- struct kho_sub_fdt *sub_fdt;
- int err;
-
- sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL);
- if (!sub_fdt)
- return -ENOMEM;
-
- INIT_LIST_HEAD(&sub_fdt->l);
- sub_fdt->name = name;
- sub_fdt->fdt = fdt;
-
- mutex_lock(&kho_out.fdts_lock);
- list_add_tail(&sub_fdt->l, &kho_out.sub_fdts);
- err = kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false);
- mutex_unlock(&kho_out.fdts_lock);
-
- return err;
-}
-EXPORT_SYMBOL_GPL(kho_add_subtree);
-
-void kho_remove_subtree(void *fdt)
-{
- struct kho_sub_fdt *sub_fdt;
-
- mutex_lock(&kho_out.fdts_lock);
- list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) {
- if (sub_fdt->fdt == fdt) {
- list_del(&sub_fdt->l);
- kfree(sub_fdt);
- kho_debugfs_fdt_remove(&kho_out.dbg, fdt);
- break;
- }
- }
- mutex_unlock(&kho_out.fdts_lock);
-
-}
-EXPORT_SYMBOL_GPL(kho_remove_subtree);
-
-/**
- * kho_preserve_folio - preserve a folio across kexec.
- * @folio: folio to preserve.
- *
- * Instructs KHO to preserve the whole folio across kexec. The order
- * will be preserved as well.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_folio(struct folio *folio)
-{
- const unsigned long pfn = folio_pfn(folio);
- const unsigned int order = folio_order(folio);
- struct kho_mem_track *track = &kho_out.track;
-
- return __kho_preserve_order(track, pfn, order);
-}
-EXPORT_SYMBOL_GPL(kho_preserve_folio);
-
-/**
- * kho_unpreserve_folio - unpreserve a folio.
- * @folio: folio to unpreserve.
- *
- * Instructs KHO to unpreserve a folio that was preserved by
- * kho_preserve_folio() before. The provided @folio (pfn and order)
- * must exactly match a previously preserved folio.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_unpreserve_folio(struct folio *folio)
-{
- const unsigned long pfn = folio_pfn(folio);
- const unsigned int order = folio_order(folio);
- struct kho_mem_track *track = &kho_out.track;
-
- if (kho_out.finalized)
- return -EBUSY;
-
- __kho_unpreserve_order(track, pfn, order);
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
-
-/**
- * kho_preserve_pages - preserve contiguous pages across kexec
- * @page: first page in the list.
- * @nr_pages: number of pages.
- *
- * Preserve a contiguous list of order 0 pages. Must be restored using
- * kho_restore_pages() to ensure the pages are restored properly as order 0.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_pages(struct page *page, unsigned int nr_pages)
-{
- struct kho_mem_track *track = &kho_out.track;
- const unsigned long start_pfn = page_to_pfn(page);
- const unsigned long end_pfn = start_pfn + nr_pages;
- unsigned long pfn = start_pfn;
- unsigned long failed_pfn = 0;
- int err = 0;
-
- while (pfn < end_pfn) {
- const unsigned int order =
- min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
- err = __kho_preserve_order(track, pfn, order);
- if (err) {
- failed_pfn = pfn;
- break;
- }
-
- pfn += 1 << order;
- }
-
- if (err)
- __kho_unpreserve(track, start_pfn, failed_pfn);
-
- return err;
-}
-EXPORT_SYMBOL_GPL(kho_preserve_pages);
-
-/**
- * kho_unpreserve_pages - unpreserve contiguous pages.
- * @page: first page in the list.
- * @nr_pages: number of pages.
- *
- * Instructs KHO to unpreserve @nr_pages contigious pages starting from @page.
- * This call must exactly match a granularity at which memory was originally
- * preserved by kho_preserve_pages, call with the same @page and
- * @nr_pages). Unpreserving arbitrary sub-ranges of larger preserved blocks is
- * not supported.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
-{
- struct kho_mem_track *track = &kho_out.track;
- const unsigned long start_pfn = page_to_pfn(page);
- const unsigned long end_pfn = start_pfn + nr_pages;
-
- if (kho_out.finalized)
- return -EBUSY;
-
- __kho_unpreserve(track, start_pfn, end_pfn);
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_unpreserve_pages);
-
-struct kho_vmalloc_hdr {
- DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *);
-};
-
-#define KHO_VMALLOC_SIZE \
- ((PAGE_SIZE - sizeof(struct kho_vmalloc_hdr)) / \
- sizeof(phys_addr_t))
-
-struct kho_vmalloc_chunk {
- struct kho_vmalloc_hdr hdr;
- phys_addr_t phys[KHO_VMALLOC_SIZE];
-};
-
-static_assert(sizeof(struct kho_vmalloc_chunk) == PAGE_SIZE);
-
-/* vmalloc flags KHO supports */
-#define KHO_VMALLOC_SUPPORTED_FLAGS (VM_ALLOC | VM_ALLOW_HUGE_VMAP)
-
-/* KHO internal flags for vmalloc preservations */
-#define KHO_VMALLOC_ALLOC 0x0001
-#define KHO_VMALLOC_HUGE_VMAP 0x0002
-
-static unsigned short vmalloc_flags_to_kho(unsigned int vm_flags)
-{
- unsigned short kho_flags = 0;
-
- if (vm_flags & VM_ALLOC)
- kho_flags |= KHO_VMALLOC_ALLOC;
- if (vm_flags & VM_ALLOW_HUGE_VMAP)
- kho_flags |= KHO_VMALLOC_HUGE_VMAP;
-
- return kho_flags;
-}
-
-static unsigned int kho_flags_to_vmalloc(unsigned short kho_flags)
-{
- unsigned int vm_flags = 0;
-
- if (kho_flags & KHO_VMALLOC_ALLOC)
- vm_flags |= VM_ALLOC;
- if (kho_flags & KHO_VMALLOC_HUGE_VMAP)
- vm_flags |= VM_ALLOW_HUGE_VMAP;
-
- return vm_flags;
-}
-
-static struct kho_vmalloc_chunk *new_vmalloc_chunk(struct kho_vmalloc_chunk *cur)
-{
- struct kho_vmalloc_chunk *chunk;
- int err;
-
- chunk = (struct kho_vmalloc_chunk *)get_zeroed_page(GFP_KERNEL);
- if (!chunk)
- return NULL;
-
- err = kho_preserve_pages(virt_to_page(chunk), 1);
- if (err)
- goto err_free;
- if (cur)
- KHOSER_STORE_PTR(cur->hdr.next, chunk);
- return chunk;
-
-err_free:
- free_page((unsigned long)chunk);
- return NULL;
-}
-
-static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk)
-{
- struct kho_mem_track *track = &kho_out.track;
- unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
-
- __kho_unpreserve(track, pfn, pfn + 1);
-
- for (int i = 0; chunk->phys[i]; i++) {
- pfn = PHYS_PFN(chunk->phys[i]);
- __kho_unpreserve(track, pfn, pfn + 1);
- }
-}
-
-static void kho_vmalloc_free_chunks(struct kho_vmalloc *kho_vmalloc)
-{
- struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(kho_vmalloc->first);
-
- while (chunk) {
- struct kho_vmalloc_chunk *tmp = chunk;
-
- kho_vmalloc_unpreserve_chunk(chunk);
-
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- free_page((unsigned long)tmp);
- }
-}
-
-/**
- * kho_preserve_vmalloc - preserve memory allocated with vmalloc() across kexec
- * @ptr: pointer to the area in vmalloc address space
- * @preservation: placeholder for preservation metadata
- *
- * Instructs KHO to preserve the area in vmalloc address space at @ptr. The
- * physical pages mapped at @ptr will be preserved and on successful return
- * @preservation will hold the physical address of a structure that describes
- * the preservation.
- *
- * NOTE: The memory allocated with vmalloc_node() variants cannot be reliably
- * restored on the same node
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
-{
- struct kho_vmalloc_chunk *chunk;
- struct vm_struct *vm = find_vm_area(ptr);
- unsigned int order, flags, nr_contig_pages;
- unsigned int idx = 0;
- int err;
-
- if (!vm)
- return -EINVAL;
-
- if (vm->flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
- return -EOPNOTSUPP;
-
- flags = vmalloc_flags_to_kho(vm->flags);
- order = get_vm_area_page_order(vm);
-
- chunk = new_vmalloc_chunk(NULL);
- if (!chunk)
- return -ENOMEM;
- KHOSER_STORE_PTR(preservation->first, chunk);
-
- nr_contig_pages = (1 << order);
- for (int i = 0; i < vm->nr_pages; i += nr_contig_pages) {
- phys_addr_t phys = page_to_phys(vm->pages[i]);
-
- err = kho_preserve_pages(vm->pages[i], nr_contig_pages);
- if (err)
- goto err_free;
-
- chunk->phys[idx++] = phys;
- if (idx == ARRAY_SIZE(chunk->phys)) {
- chunk = new_vmalloc_chunk(chunk);
- if (!chunk)
- goto err_free;
- idx = 0;
- }
- }
-
- preservation->total_pages = vm->nr_pages;
- preservation->flags = flags;
- preservation->order = order;
-
- return 0;
-
-err_free:
- kho_vmalloc_free_chunks(preservation);
- return err;
-}
-EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
-
-/**
- * kho_restore_vmalloc - recreates and populates an area in vmalloc address
- * space from the preserved memory.
- * @preservation: preservation metadata.
- *
- * Recreates an area in vmalloc address space and populates it with memory that
- * was preserved using kho_preserve_vmalloc().
- *
- * Return: pointer to the area in the vmalloc address space, NULL on failure.
- */
-void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
-{
- struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(preservation->first);
- unsigned int align, order, shift, vm_flags;
- unsigned long total_pages, contig_pages;
- unsigned long addr, size;
- struct vm_struct *area;
- struct page **pages;
- unsigned int idx = 0;
- int err;
-
- vm_flags = kho_flags_to_vmalloc(preservation->flags);
- if (vm_flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
- return NULL;
-
- total_pages = preservation->total_pages;
- pages = kvmalloc_array(total_pages, sizeof(*pages), GFP_KERNEL);
- if (!pages)
- return NULL;
- order = preservation->order;
- contig_pages = (1 << order);
- shift = PAGE_SHIFT + order;
- align = 1 << shift;
-
- while (chunk) {
- struct page *page;
-
- for (int i = 0; chunk->phys[i]; i++) {
- phys_addr_t phys = chunk->phys[i];
-
- if (idx + contig_pages > total_pages)
- goto err_free_pages_array;
-
- page = kho_restore_pages(phys, contig_pages);
- if (!page)
- goto err_free_pages_array;
-
- for (int j = 0; j < contig_pages; j++)
- pages[idx++] = page;
-
- phys += contig_pages * PAGE_SIZE;
- }
-
- page = kho_restore_pages(virt_to_phys(chunk), 1);
- if (!page)
- goto err_free_pages_array;
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- __free_page(page);
- }
-
- if (idx != total_pages)
- goto err_free_pages_array;
-
- area = __get_vm_area_node(total_pages * PAGE_SIZE, align, shift,
- vm_flags, VMALLOC_START, VMALLOC_END,
- NUMA_NO_NODE, GFP_KERNEL,
- __builtin_return_address(0));
- if (!area)
- goto err_free_pages_array;
-
- addr = (unsigned long)area->addr;
- size = get_vm_area_size(area);
- err = vmap_pages_range(addr, addr + size, PAGE_KERNEL, pages, shift);
- if (err)
- goto err_free_vm_area;
-
- area->nr_pages = total_pages;
- area->pages = pages;
-
- return area->addr;
-
-err_free_vm_area:
- free_vm_area(area);
-err_free_pages_array:
- kvfree(pages);
- return NULL;
-}
-EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
-
-static int __kho_abort(void)
-{
- if (kho_out.preserved_mem_map) {
- kho_mem_ser_free(kho_out.preserved_mem_map);
- kho_out.preserved_mem_map = NULL;
- }
-
- return 0;
-}
-
-int kho_abort(void)
-{
- int ret = 0;
-
- if (!kho_enable)
- return -EOPNOTSUPP;
-
- guard(mutex)(&kho_out.lock);
- if (!kho_out.finalized)
- return -ENOENT;
-
- ret = __kho_abort();
- if (ret)
- return ret;
-
- kho_out.finalized = false;
-
- kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt);
-
- return 0;
-}
-
-static int __kho_finalize(void)
-{
- int err = 0;
- u64 *preserved_mem_map;
- void *root = kho_out.fdt;
- struct kho_sub_fdt *fdt;
-
- err |= fdt_create(root, PAGE_SIZE);
- err |= fdt_finish_reservemap(root);
- err |= fdt_begin_node(root, "");
- err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
- /**
- * Reserve the preserved-memory-map property in the root FDT, so
- * that all property definitions will precede subnodes created by
- * KHO callers.
- */
- err |= fdt_property_placeholder(root, PROP_PRESERVED_MEMORY_MAP,
- sizeof(*preserved_mem_map),
- (void **)&preserved_mem_map);
- if (err)
- goto abort;
-
- err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
- if (err)
- goto abort;
-
- err = kho_mem_serialize(&kho_out);
- if (err)
- goto abort;
-
- *preserved_mem_map = (u64)virt_to_phys(kho_out.preserved_mem_map);
-
- mutex_lock(&kho_out.fdts_lock);
- list_for_each_entry(fdt, &kho_out.sub_fdts, l) {
- phys_addr_t phys = virt_to_phys(fdt->fdt);
-
- err |= fdt_begin_node(root, fdt->name);
- err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
- err |= fdt_end_node(root);
- };
- mutex_unlock(&kho_out.fdts_lock);
-
- err |= fdt_end_node(root);
- err |= fdt_finish(root);
-
-abort:
- if (err) {
- pr_err("Failed to convert KHO state tree: %d\n", err);
- __kho_abort();
- }
-
- return err;
-}
-
-int kho_finalize(void)
-{
- int ret;
-
- if (!kho_enable)
- return -EOPNOTSUPP;
-
- guard(mutex)(&kho_out.lock);
- if (kho_out.finalized)
- return -EEXIST;
-
- ret = __kho_finalize();
- if (ret)
- return ret;
-
- kho_out.finalized = true;
-
- return kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
- kho_out.fdt, true);
-}
-
-bool kho_finalized(void)
-{
- guard(mutex)(&kho_out.lock);
- return kho_out.finalized;
-}
-
-struct kho_in {
- phys_addr_t fdt_phys;
- phys_addr_t scratch_phys;
- struct kho_debugfs dbg;
-};
-
-static struct kho_in kho_in = {
-};
-
-static const void *kho_get_fdt(void)
-{
- return kho_in.fdt_phys ? phys_to_virt(kho_in.fdt_phys) : NULL;
-}
-
-/**
- * is_kho_boot - check if current kernel was booted via KHO-enabled
- * kexec
- *
- * This function checks if the current kernel was loaded through a kexec
- * operation with KHO enabled, by verifying that a valid KHO FDT
- * was passed.
- *
- * Note: This function returns reliable results only after
- * kho_populate() has been called during early boot. Before that,
- * it may return false even if KHO data is present.
- *
- * Return: true if booted via KHO-enabled kexec, false otherwise
- */
-bool is_kho_boot(void)
-{
- return !!kho_get_fdt();
-}
-EXPORT_SYMBOL_GPL(is_kho_boot);
-
-/**
- * kho_retrieve_subtree - retrieve a preserved sub FDT by its name.
- * @name: the name of the sub FDT passed to kho_add_subtree().
- * @phys: if found, the physical address of the sub FDT is stored in @phys.
- *
- * Retrieve a preserved sub FDT named @name and store its physical
- * address in @phys.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
-{
- const void *fdt = kho_get_fdt();
- const u64 *val;
- int offset, len;
-
- if (!fdt)
- return -ENOENT;
-
- if (!phys)
- return -EINVAL;
-
- offset = fdt_subnode_offset(fdt, 0, name);
- if (offset < 0)
- return -ENOENT;
-
- val = fdt_getprop(fdt, offset, PROP_SUB_FDT, &len);
- if (!val || len != sizeof(*val))
- return -EINVAL;
-
- *phys = (phys_addr_t)*val;
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
-
-static __init int kho_init(void)
-{
- int err = 0;
- const void *fdt = kho_get_fdt();
- struct page *fdt_page;
-
- if (!kho_enable)
- return 0;
-
- fdt_page = alloc_page(GFP_KERNEL);
- if (!fdt_page) {
- err = -ENOMEM;
- goto err_free_scratch;
- }
- kho_out.fdt = page_to_virt(fdt_page);
-
- err = kho_debugfs_init();
- if (err)
- goto err_free_fdt;
-
- err = kho_out_debugfs_init(&kho_out.dbg);
- if (err)
- goto err_free_fdt;
-
- if (fdt) {
- kho_in_debugfs_init(&kho_in.dbg, fdt);
- return 0;
- }
-
- for (int i = 0; i < kho_scratch_cnt; i++) {
- unsigned long base_pfn = PHYS_PFN(kho_scratch[i].addr);
- unsigned long count = kho_scratch[i].size >> PAGE_SHIFT;
- unsigned long pfn;
-
- for (pfn = base_pfn; pfn < base_pfn + count;
- pfn += pageblock_nr_pages)
- init_cma_reserved_pageblock(pfn_to_page(pfn));
- }
-
- return 0;
-
-err_free_fdt:
- put_page(fdt_page);
- kho_out.fdt = NULL;
-err_free_scratch:
- for (int i = 0; i < kho_scratch_cnt; i++) {
- void *start = __va(kho_scratch[i].addr);
- void *end = start + kho_scratch[i].size;
-
- free_reserved_area(start, end, -1, "");
- }
- kho_enable = false;
- return err;
-}
-fs_initcall(kho_init);
-
-static void __init kho_release_scratch(void)
-{
- phys_addr_t start, end;
- u64 i;
-
- memmap_init_kho_scratch_pages();
-
- /*
- * Mark scratch mem as CMA before we return it. That way we
- * ensure that no kernel allocations happen on it. That means
- * we can reuse it as scratch memory again later.
- */
- __for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
- MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
- ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
- ulong end_pfn = pageblock_align(PFN_UP(end));
- ulong pfn;
-
- for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
- init_pageblock_migratetype(pfn_to_page(pfn),
- MIGRATE_CMA, false);
- }
-}
-
-void __init kho_memory_init(void)
-{
- struct folio *folio;
-
- if (kho_in.scratch_phys) {
- kho_scratch = phys_to_virt(kho_in.scratch_phys);
- kho_release_scratch();
-
- kho_mem_deserialize(kho_get_fdt());
- folio = kho_restore_folio(kho_in.fdt_phys);
- if (!folio)
- pr_warn("failed to restore folio for KHO fdt\n");
- } else {
- kho_reserve_scratch();
- }
-}
-
-void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
- phys_addr_t scratch_phys, u64 scratch_len)
-{
- void *fdt = NULL;
- struct kho_scratch *scratch = NULL;
- int err = 0;
- unsigned int scratch_cnt = scratch_len / sizeof(*kho_scratch);
-
- /* Validate the input FDT */
- fdt = early_memremap(fdt_phys, fdt_len);
- if (!fdt) {
- pr_warn("setup: failed to memremap FDT (0x%llx)\n", fdt_phys);
- err = -EFAULT;
- goto out;
- }
- err = fdt_check_header(fdt);
- if (err) {
- pr_warn("setup: handover FDT (0x%llx) is invalid: %d\n",
- fdt_phys, err);
- err = -EINVAL;
- goto out;
- }
- err = fdt_node_check_compatible(fdt, 0, KHO_FDT_COMPATIBLE);
- if (err) {
- pr_warn("setup: handover FDT (0x%llx) is incompatible with '%s': %d\n",
- fdt_phys, KHO_FDT_COMPATIBLE, err);
- err = -EINVAL;
- goto out;
- }
-
- scratch = early_memremap(scratch_phys, scratch_len);
- if (!scratch) {
- pr_warn("setup: failed to memremap scratch (phys=0x%llx, len=%lld)\n",
- scratch_phys, scratch_len);
- err = -EFAULT;
- goto out;
- }
-
- /*
- * We pass a safe contiguous blocks of memory to use for early boot
- * purporses from the previous kernel so that we can resize the
- * memblock array as needed.
- */
- for (int i = 0; i < scratch_cnt; i++) {
- struct kho_scratch *area = &scratch[i];
- u64 size = area->size;
-
- memblock_add(area->addr, size);
- err = memblock_mark_kho_scratch(area->addr, size);
- if (WARN_ON(err)) {
- pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %d",
- &area->addr, &size, err);
- goto out;
- }
- pr_debug("Marked 0x%pa+0x%pa as scratch", &area->addr, &size);
- }
-
- memblock_reserve(scratch_phys, scratch_len);
-
- /*
- * Now that we have a viable region of scratch memory, let's tell
- * the memblocks allocator to only use that for any allocations.
- * That way we ensure that nothing scribbles over in use data while
- * we initialize the page tables which we will need to ingest all
- * memory reservations from the previous kernel.
- */
- memblock_set_kho_scratch_only();
-
- kho_in.fdt_phys = fdt_phys;
- kho_in.scratch_phys = scratch_phys;
- kho_scratch_cnt = scratch_cnt;
- pr_info("found kexec handover data. Will skip init for some devices\n");
-
-out:
- if (fdt)
- early_memunmap(fdt, fdt_len);
- if (scratch)
- early_memunmap(scratch, scratch_len);
- if (err)
- pr_warn("disabling KHO revival: %d\n", err);
-}
-
-/* Helper functions for kexec_file_load */
-
-int kho_fill_kimage(struct kimage *image)
-{
- ssize_t scratch_size;
- int err = 0;
- struct kexec_buf scratch;
-
- if (!kho_out.finalized)
- return 0;
-
- image->kho.fdt = virt_to_phys(kho_out.fdt);
-
- scratch_size = sizeof(*kho_scratch) * kho_scratch_cnt;
- scratch = (struct kexec_buf){
- .image = image,
- .buffer = kho_scratch,
- .bufsz = scratch_size,
- .mem = KEXEC_BUF_MEM_UNKNOWN,
- .memsz = scratch_size,
- .buf_align = SZ_64K, /* Makes it easier to map */
- .buf_max = ULONG_MAX,
- .top_down = true,
- };
- err = kexec_add_buffer(&scratch);
- if (err)
- return err;
- image->kho.scratch = &image->segment[image->nr_segments - 1];
-
- return 0;
-}
-
-static int kho_walk_scratch(struct kexec_buf *kbuf,
- int (*func)(struct resource *, void *))
-{
- int ret = 0;
- int i;
-
- for (i = 0; i < kho_scratch_cnt; i++) {
- struct resource res = {
- .start = kho_scratch[i].addr,
- .end = kho_scratch[i].addr + kho_scratch[i].size - 1,
- };
-
- /* Try to fit the kimage into our KHO scratch region */
- ret = func(&res, kbuf);
- if (ret)
- break;
- }
-
- return ret;
-}
-
-int kho_locate_mem_hole(struct kexec_buf *kbuf,
- int (*func)(struct resource *, void *))
-{
- int ret;
-
- if (!kho_enable || kbuf->image->type == KEXEC_TYPE_CRASH)
- return 1;
-
- ret = kho_walk_scratch(kbuf, func);
-
- return ret == 1 ? 0 : -EADDRNOTAVAIL;
-}
diff --git a/kernel/kexec_handover_debug.c a/kernel/kexec_handover_debug.c
deleted file mode 100644
--- a/kernel/kexec_handover_debug.c
+++ /dev/null
@@ -1,216 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover.c - kexec handover metadata processing
- * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
- * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
- * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
- * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include <linux/init.h>
-#include <linux/io.h>
-#include <linux/libfdt.h>
-#include <linux/mm.h>
-#include "kexec_handover_internal.h"
-
-static struct dentry *debugfs_root;
-
-struct fdt_debugfs {
- struct list_head list;
- struct debugfs_blob_wrapper wrapper;
- struct dentry *file;
-};
-
-static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
- const char *name, const void *fdt)
-{
- struct fdt_debugfs *f;
- struct dentry *file;
-
- f = kmalloc(sizeof(*f), GFP_KERNEL);
- if (!f)
- return -ENOMEM;
-
- f->wrapper.data = (void *)fdt;
- f->wrapper.size = fdt_totalsize(fdt);
-
- file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
- if (IS_ERR(file)) {
- kfree(f);
- return PTR_ERR(file);
- }
-
- f->file = file;
- list_add(&f->list, list);
-
- return 0;
-}
-
-int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root)
-{
- struct dentry *dir;
-
- if (root)
- dir = dbg->dir;
- else
- dir = dbg->sub_fdt_dir;
-
- return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
-}
-
-void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt)
-{
- struct fdt_debugfs *ff;
-
- list_for_each_entry(ff, &dbg->fdt_list, list) {
- if (ff->wrapper.data == fdt) {
- debugfs_remove(ff->file);
- list_del(&ff->list);
- kfree(ff);
- break;
- }
- }
-}
-
-static int kho_out_finalize_get(void *data, u64 *val)
-{
- *val = kho_finalized();
-
- return 0;
-}
-
-static int kho_out_finalize_set(void *data, u64 _val)
-{
- return (!!_val) ? kho_finalize() : kho_abort();
-}
-
-DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
- kho_out_finalize_set, "%llu\n");
-
-static int scratch_phys_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_phys);
-
-static int scratch_len_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].size);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_len);
-
-__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
-{
- struct dentry *dir, *sub_fdt_dir;
- int err, child;
-
- INIT_LIST_HEAD(&dbg->fdt_list);
-
- dir = debugfs_create_dir("in", debugfs_root);
- if (IS_ERR(dir)) {
- err = PTR_ERR(dir);
- goto err_out;
- }
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
- if (IS_ERR(sub_fdt_dir)) {
- err = PTR_ERR(sub_fdt_dir);
- goto err_rmdir;
- }
-
- err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt);
- if (err)
- goto err_rmdir;
-
- fdt_for_each_subnode(child, fdt, 0) {
- int len = 0;
- const char *name = fdt_get_name(fdt, child, NULL);
- const u64 *fdt_phys;
-
- fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
- if (!fdt_phys)
- continue;
- if (len != sizeof(*fdt_phys)) {
- pr_warn("node %s prop fdt has invalid length: %d\n",
- name, len);
- continue;
- }
- err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
- phys_to_virt(*fdt_phys));
- if (err) {
- pr_warn("failed to add fdt %s to debugfs: %d\n", name,
- err);
- continue;
- }
- }
-
- dbg->dir = dir;
- dbg->sub_fdt_dir = sub_fdt_dir;
-
- return;
-err_rmdir:
- debugfs_remove_recursive(dir);
-err_out:
- /*
- * Failure to create /sys/kernel/debug/kho/in does not prevent
- * reviving state from KHO and setting up KHO for the next
- * kexec.
- */
- if (err)
- pr_err("failed exposing handover FDT in debugfs: %d\n", err);
-}
-
-__init int kho_out_debugfs_init(struct kho_debugfs *dbg)
-{
- struct dentry *dir, *f, *sub_fdt_dir;
-
- INIT_LIST_HEAD(&dbg->fdt_list);
-
- dir = debugfs_create_dir("out", debugfs_root);
- if (IS_ERR(dir))
- return -ENOMEM;
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
- if (IS_ERR(sub_fdt_dir))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
- &scratch_phys_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_len", 0400, dir, NULL,
- &scratch_len_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("finalize", 0600, dir, NULL,
- &kho_out_finalize_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- dbg->dir = dir;
- dbg->sub_fdt_dir = sub_fdt_dir;
- return 0;
-
-err_rmdir:
- debugfs_remove_recursive(dir);
- return -ENOENT;
-}
-
-__init int kho_debugfs_init(void)
-{
- debugfs_root = debugfs_create_dir("kho", NULL);
- if (IS_ERR(debugfs_root))
- return -ENOENT;
- return 0;
-}
diff --git a/kernel/kexec_handover_internal.h a/kernel/kexec_handover_internal.h
deleted file mode 100644
--- a/kernel/kexec_handover_internal.h
+++ /dev/null
@@ -1,45 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
-#define LINUX_KEXEC_HANDOVER_INTERNAL_H
-
-#include <linux/kexec_handover.h>
-#include <linux/list.h>
-#include <linux/types.h>
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
-#include <linux/debugfs.h>
-
-struct kho_debugfs {
- struct dentry *dir;
- struct dentry *sub_fdt_dir;
- struct list_head fdt_list;
-};
-
-#else
-struct kho_debugfs {};
-#endif
-
-extern struct kho_scratch *kho_scratch;
-extern unsigned int kho_scratch_cnt;
-
-bool kho_finalized(void);
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
-int kho_debugfs_init(void);
-void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
-int kho_out_debugfs_init(struct kho_debugfs *dbg);
-int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root);
-void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt);
-#else
-static inline int kho_debugfs_init(void) { return 0; }
-static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
- const void *fdt) { }
-static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
-static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root) { return 0; }
-static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg,
- void *fdt) { }
-#endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */
-
-#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
diff --git a/kernel/liveupdate/Kconfig a/kernel/liveupdate/Kconfig
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/Kconfig
@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menu "Live Update"
+
+config KEXEC_HANDOVER
+ bool "kexec handover"
+ depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
+ depends on !DEFERRED_STRUCT_PAGE_INIT
+ select MEMBLOCK_KHO_SCRATCH
+ select KEXEC_FILE
+ select DEBUG_FS
+ select LIBFDT
+ select CMA
+ help
+ Allow kexec to hand over state across kernels by generating and
+ passing additional metadata to the target kernel. This is useful
+ to keep data or state alive across the kexec. For this to work,
+ both source and target kernels need to have this option enabled.
+
+config KEXEC_HANDOVER_DEBUGFS
+ bool "kexec handover debugfs interface"
+ depends on KEXEC_HANDOVER
+ depends on DEBUG_FS
+ help
+ Allow to control kexec handover device tree via debugfs
+ interface, i.e. finalize the state or aborting the finalization.
+ Also, enables inspecting the KHO fdt trees with the debugfs binary
+ blobs.
+
+endmenu
diff --git a/kernel/liveupdate/kexec_handover.c a/kernel/liveupdate/kexec_handover.c
new file mode 100664
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover.c
@@ -0,0 +1,1510 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover.c - kexec handover metadata processing
+ * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
+ * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
+ * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include <linux/cma.h>
+#include <linux/count_zeros.h>
+#include <linux/kexec.h>
+#include <linux/kexec_handover.h>
+#include <linux/libfdt.h>
+#include <linux/list.h>
+#include <linux/memblock.h>
+#include <linux/page-isolation.h>
+#include <linux/vmalloc.h>
+
+#include <asm/early_ioremap.h>
+
+/*
+ * KHO is tightly coupled with mm init and needs access to some of mm
+ * internal APIs.
+ */
+#include "../../mm/internal.h"
+#include "../kexec_internal.h"
+#include "kexec_handover_internal.h"
+
+#define KHO_FDT_COMPATIBLE "kho-v1"
+#define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
+#define PROP_SUB_FDT "fdt"
+
+#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
+
+/*
+ * KHO uses page->private, which is an unsigned long, to store page metadata.
+ * Use it to store both the magic and the order.
+ */
+union kho_page_info {
+ unsigned long page_private;
+ struct {
+ unsigned int order;
+ unsigned int magic;
+ };
+};
+
+static_assert(sizeof(union kho_page_info) == sizeof(((struct page *)0)->private));
+
+static bool kho_enable __ro_after_init;
+
+bool kho_is_enabled(void)
+{
+ return kho_enable;
+}
+EXPORT_SYMBOL_GPL(kho_is_enabled);
+
+static int __init kho_parse_enable(char *p)
+{
+ return kstrtobool(p, &kho_enable);
+}
+early_param("kho", kho_parse_enable);
+
+/*
+ * Keep track of memory that is to be preserved across KHO.
+ *
+ * The serializing side uses two levels of xarrays to manage chunks of per-order
+ * 512 byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order of a
+ * 1TB system would fit inside a single 512 byte bitmap. For order 0 allocations
+ * each bitmap will cover 16M of address space. Thus, for 16G of memory at most
+ * 512K of bitmap memory will be needed for order 0.
+ *
+ * This approach is fully incremental, as the serialization progresses folios
+ * can continue be aggregated to the tracker. The final step, immediately prior
+ * to kexec would serialize the xarray information into a linked list for the
+ * successor kernel to parse.
+ */
+
+#define PRESERVE_BITS (512 * 8)
+
+struct kho_mem_phys_bits {
+ DECLARE_BITMAP(preserve, PRESERVE_BITS);
+};
+
+struct kho_mem_phys {
+ /*
+ * Points to kho_mem_phys_bits, a sparse bitmap array. Each bit is sized
+ * to order.
+ */
+ struct xarray phys_bits;
+};
+
+struct kho_mem_track {
+ /* Points to kho_mem_phys, each order gets its own bitmap tree */
+ struct xarray orders;
+};
+
+struct khoser_mem_chunk;
+
+struct kho_sub_fdt {
+ struct list_head l;
+ const char *name;
+ void *fdt;
+};
+
+struct kho_out {
+ void *fdt;
+ bool finalized;
+ struct mutex lock; /* protects KHO FDT finalization */
+
+ struct list_head sub_fdts;
+ struct mutex fdts_lock;
+
+ struct kho_mem_track track;
+ /* First chunk of serialized preserved memory map */
+ struct khoser_mem_chunk *preserved_mem_map;
+
+ struct kho_debugfs dbg;
+};
+
+static struct kho_out kho_out = {
+ .lock = __MUTEX_INITIALIZER(kho_out.lock),
+ .track = {
+ .orders = XARRAY_INIT(kho_out.track.orders, 0),
+ },
+ .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts),
+ .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock),
+ .finalized = false,
+};
+
+static void *xa_load_or_alloc(struct xarray *xa, unsigned long index, size_t sz)
+{
+ void *elm, *res;
+
+ elm = xa_load(xa, index);
+ if (elm)
+ return elm;
+
+ elm = kzalloc(sz, GFP_KERNEL);
+ if (!elm)
+ return ERR_PTR(-ENOMEM);
+
+ res = xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
+ if (xa_is_err(res))
+ res = ERR_PTR(xa_err(res));
+
+ if (res) {
+ kfree(elm);
+ return res;
+ }
+
+ return elm;
+}
+
+static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn,
+ unsigned int order)
+{
+ struct kho_mem_phys_bits *bits;
+ struct kho_mem_phys *physxa;
+ const unsigned long pfn_high = pfn >> order;
+
+ physxa = xa_load(&track->orders, order);
+ if (!physxa)
+ return;
+
+ bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
+ if (!bits)
+ return;
+
+ clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+}
+
+static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
+ unsigned long end_pfn)
+{
+ unsigned int order;
+
+ while (pfn < end_pfn) {
+ order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+
+ __kho_unpreserve_order(track, pfn, order);
+
+ pfn += 1 << order;
+ }
+}
+
+static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
+ unsigned int order)
+{
+ struct kho_mem_phys_bits *bits;
+ struct kho_mem_phys *physxa, *new_physxa;
+ const unsigned long pfn_high = pfn >> order;
+
+ might_sleep();
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ physxa = xa_load(&track->orders, order);
+ if (!physxa) {
+ int err;
+
+ new_physxa = kzalloc(sizeof(*physxa), GFP_KERNEL);
+ if (!new_physxa)
+ return -ENOMEM;
+
+ xa_init(&new_physxa->phys_bits);
+ physxa = xa_cmpxchg(&track->orders, order, NULL, new_physxa,
+ GFP_KERNEL);
+
+ err = xa_err(physxa);
+ if (err || physxa) {
+ xa_destroy(&new_physxa->phys_bits);
+ kfree(new_physxa);
+
+ if (err)
+ return err;
+ } else {
+ physxa = new_physxa;
+ }
+ }
+
+ bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS,
+ sizeof(*bits));
+ if (IS_ERR(bits))
+ return PTR_ERR(bits);
+
+ set_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+
+ return 0;
+}
+
+static struct page *kho_restore_page(phys_addr_t phys)
+{
+ struct page *page = pfn_to_online_page(PHYS_PFN(phys));
+ union kho_page_info info;
+ unsigned int nr_pages;
+
+ if (!page)
+ return NULL;
+
+ info.page_private = page->private;
+ /*
+ * deserialize_bitmap() only sets the magic on the head page. This magic
+ * check also implicitly makes sure phys is order-aligned since for
+ * non-order-aligned phys addresses, magic will never be set.
+ */
+ if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER))
+ return NULL;
+ nr_pages = (1 << info.order);
+
+ /* Clear private to make sure later restores on this page error out. */
+ page->private = 0;
+ /* Head page gets refcount of 1. */
+ set_page_count(page, 1);
+
+ /* For higher order folios, tail pages get a page count of zero. */
+ for (unsigned int i = 1; i < nr_pages; i++)
+ set_page_count(page + i, 0);
+
+ if (info.order > 0)
+ prep_compound_page(page, info.order);
+
+ adjust_managed_page_count(page, nr_pages);
+ return page;
+}
+
+/**
+ * kho_restore_folio - recreates the folio from the preserved memory.
+ * @phys: physical address of the folio.
+ *
+ * Return: pointer to the struct folio on success, NULL on failure.
+ */
+struct folio *kho_restore_folio(phys_addr_t phys)
+{
+ struct page *page = kho_restore_page(phys);
+
+ return page ? page_folio(page) : NULL;
+}
+EXPORT_SYMBOL_GPL(kho_restore_folio);
+
+/**
+ * kho_restore_pages - restore list of contiguous order 0 pages.
+ * @phys: physical address of the first page.
+ * @nr_pages: number of pages.
+ *
+ * Restore a contiguous list of order 0 pages that was preserved with
+ * kho_preserve_pages().
+ *
+ * Return: 0 on success, error code on failure
+ */
+struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages)
+{
+ const unsigned long start_pfn = PHYS_PFN(phys);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+ unsigned long pfn = start_pfn;
+
+ while (pfn < end_pfn) {
+ const unsigned int order =
+ min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+ struct page *page = kho_restore_page(PFN_PHYS(pfn));
+
+ if (!page)
+ return NULL;
+ split_page(page, order);
+ pfn += 1 << order;
+ }
+
+ return pfn_to_page(start_pfn);
+}
+EXPORT_SYMBOL_GPL(kho_restore_pages);
+
+/* Serialize and deserialize struct kho_mem_phys across kexec
+ *
+ * Record all the bitmaps in a linked list of pages for the next kernel to
+ * process. Each chunk holds bitmaps of the same order and each block of bitmaps
+ * starts at a given physical address. This allows the bitmaps to be sparse. The
+ * xarray is used to store them in a tree while building up the data structure,
+ * but the KHO successor kernel only needs to process them once in order.
+ *
+ * All of this memory is normal kmalloc() memory and is not marked for
+ * preservation. The successor kernel will remain isolated to the scratch space
+ * until it completes processing this list. Once processed all the memory
+ * storing these ranges will be marked as free.
+ */
+
+struct khoser_mem_bitmap_ptr {
+ phys_addr_t phys_start;
+ DECLARE_KHOSER_PTR(bitmap, struct kho_mem_phys_bits *);
+};
+
+struct khoser_mem_chunk_hdr {
+ DECLARE_KHOSER_PTR(next, struct khoser_mem_chunk *);
+ unsigned int order;
+ unsigned int num_elms;
+};
+
+#define KHOSER_BITMAP_SIZE \
+ ((PAGE_SIZE - sizeof(struct khoser_mem_chunk_hdr)) / \
+ sizeof(struct khoser_mem_bitmap_ptr))
+
+struct khoser_mem_chunk {
+ struct khoser_mem_chunk_hdr hdr;
+ struct khoser_mem_bitmap_ptr bitmaps[KHOSER_BITMAP_SIZE];
+};
+
+static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE);
+
+static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk,
+ unsigned long order)
+{
+ struct khoser_mem_chunk *chunk;
+
+ chunk = kzalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!chunk)
+ return NULL;
+ chunk->hdr.order = order;
+ if (cur_chunk)
+ KHOSER_STORE_PTR(cur_chunk->hdr.next, chunk);
+ return chunk;
+}
+
+static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
+{
+ struct khoser_mem_chunk *chunk = first_chunk;
+
+ while (chunk) {
+ struct khoser_mem_chunk *tmp = chunk;
+
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ kfree(tmp);
+ }
+}
+
+static int kho_mem_serialize(struct kho_out *kho_out)
+{
+ struct khoser_mem_chunk *first_chunk = NULL;
+ struct khoser_mem_chunk *chunk = NULL;
+ struct kho_mem_phys *physxa;
+ unsigned long order;
+
+ xa_for_each(&kho_out->track.orders, order, physxa) {
+ struct kho_mem_phys_bits *bits;
+ unsigned long phys;
+
+ chunk = new_chunk(chunk, order);
+ if (!chunk)
+ goto err_free;
+
+ if (!first_chunk)
+ first_chunk = chunk;
+
+ xa_for_each(&physxa->phys_bits, phys, bits) {
+ struct khoser_mem_bitmap_ptr *elm;
+
+ if (chunk->hdr.num_elms == ARRAY_SIZE(chunk->bitmaps)) {
+ chunk = new_chunk(chunk, order);
+ if (!chunk)
+ goto err_free;
+ }
+
+ elm = &chunk->bitmaps[chunk->hdr.num_elms];
+ chunk->hdr.num_elms++;
+ elm->phys_start = (phys * PRESERVE_BITS)
+ << (order + PAGE_SHIFT);
+ KHOSER_STORE_PTR(elm->bitmap, bits);
+ }
+ }
+
+ kho_out->preserved_mem_map = first_chunk;
+
+ return 0;
+
+err_free:
+ kho_mem_ser_free(first_chunk);
+ return -ENOMEM;
+}
+
+static void __init deserialize_bitmap(unsigned int order,
+ struct khoser_mem_bitmap_ptr *elm)
+{
+ struct kho_mem_phys_bits *bitmap = KHOSER_LOAD_PTR(elm->bitmap);
+ unsigned long bit;
+
+ for_each_set_bit(bit, bitmap->preserve, PRESERVE_BITS) {
+ int sz = 1 << (order + PAGE_SHIFT);
+ phys_addr_t phys =
+ elm->phys_start + (bit << (order + PAGE_SHIFT));
+ struct page *page = phys_to_page(phys);
+ union kho_page_info info;
+
+ memblock_reserve(phys, sz);
+ memblock_reserved_mark_noinit(phys, sz);
+ info.magic = KHO_PAGE_MAGIC;
+ info.order = order;
+ page->private = info.page_private;
+ }
+}
+
+static void __init kho_mem_deserialize(const void *fdt)
+{
+ struct khoser_mem_chunk *chunk;
+ const phys_addr_t *mem;
+ int len;
+
+ mem = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
+
+ if (!mem || len != sizeof(*mem)) {
+ pr_err("failed to get preserved memory bitmaps\n");
+ return;
+ }
+
+ chunk = *mem ? phys_to_virt(*mem) : NULL;
+ while (chunk) {
+ unsigned int i;
+
+ for (i = 0; i != chunk->hdr.num_elms; i++)
+ deserialize_bitmap(chunk->hdr.order,
+ &chunk->bitmaps[i]);
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ }
+}
+
+/*
+ * With KHO enabled, memory can become fragmented because KHO regions may
+ * be anywhere in physical address space. The scratch regions give us a
+ * safe zones that we will never see KHO allocations from. This is where we
+ * can later safely load our new kexec images into and then use the scratch
+ * area for early allocations that happen before page allocator is
+ * initialized.
+ */
+struct kho_scratch *kho_scratch;
+unsigned int kho_scratch_cnt;
+
+/*
+ * The scratch areas are scaled by default as percent of memory allocated from
+ * memblock. A user can override the scale with command line parameter:
+ *
+ * kho_scratch=N%
+ *
+ * It is also possible to explicitly define size for a lowmem, a global and
+ * per-node scratch areas:
+ *
+ * kho_scratch=l[KMG],n[KMG],m[KMG]
+ *
+ * The explicit size definition takes precedence over scale definition.
+ */
+static unsigned int scratch_scale __initdata = 200;
+static phys_addr_t scratch_size_global __initdata;
+static phys_addr_t scratch_size_pernode __initdata;
+static phys_addr_t scratch_size_lowmem __initdata;
+
+static int __init kho_parse_scratch_size(char *p)
+{
+ size_t len;
+ unsigned long sizes[3];
+ size_t total_size = 0;
+ int i;
+
+ if (!p)
+ return -EINVAL;
+
+ len = strlen(p);
+ if (!len)
+ return -EINVAL;
+
+ /* parse nn% */
+ if (p[len - 1] == '%') {
+ /* unsigned int max is 4,294,967,295, 10 chars */
+ char s_scale[11] = {};
+ int ret = 0;
+
+ if (len > ARRAY_SIZE(s_scale))
+ return -EINVAL;
+
+ memcpy(s_scale, p, len - 1);
+ ret = kstrtouint(s_scale, 10, &scratch_scale);
+ if (!ret)
+ pr_notice("scratch scale is %d%%\n", scratch_scale);
+ return ret;
+ }
+
+ /* parse ll[KMG],mm[KMG],nn[KMG] */
+ for (i = 0; i < ARRAY_SIZE(sizes); i++) {
+ char *endp = p;
+
+ if (i > 0) {
+ if (*p != ',')
+ return -EINVAL;
+ p += 1;
+ }
+
+ sizes[i] = memparse(p, &endp);
+ if (endp == p)
+ return -EINVAL;
+ p = endp;
+ total_size += sizes[i];
+ }
+
+ if (!total_size)
+ return -EINVAL;
+
+ /* The string should be fully consumed by now. */
+ if (*p)
+ return -EINVAL;
+
+ scratch_size_lowmem = sizes[0];
+ scratch_size_global = sizes[1];
+ scratch_size_pernode = sizes[2];
+ scratch_scale = 0;
+
+ pr_notice("scratch areas: lowmem: %lluMiB global: %lluMiB pernode: %lldMiB\n",
+ (u64)(scratch_size_lowmem >> 20),
+ (u64)(scratch_size_global >> 20),
+ (u64)(scratch_size_pernode >> 20));
+
+ return 0;
+}
+early_param("kho_scratch", kho_parse_scratch_size);
+
+static void __init scratch_size_update(void)
+{
+ phys_addr_t size;
+
+ if (!scratch_scale)
+ return;
+
+ size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
+ NUMA_NO_NODE);
+ size = size * scratch_scale / 100;
+ scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+
+ size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+ NUMA_NO_NODE);
+ size = size * scratch_scale / 100 - scratch_size_lowmem;
+ scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+}
+
+static phys_addr_t __init scratch_size_node(int nid)
+{
+ phys_addr_t size;
+
+ if (scratch_scale) {
+ size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+ nid);
+ size = size * scratch_scale / 100;
+ } else {
+ size = scratch_size_pernode;
+ }
+
+ return round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+}
+
+/**
+ * kho_reserve_scratch - Reserve a contiguous chunk of memory for kexec
+ *
+ * With KHO we can preserve arbitrary pages in the system. To ensure we still
+ * have a large contiguous region of memory when we search the physical address
+ * space for target memory, let's make sure we always have a large CMA region
+ * active. This CMA region will only be used for movable pages which are not a
+ * problem for us during KHO because we can just move them somewhere else.
+ */
+static void __init kho_reserve_scratch(void)
+{
+ phys_addr_t addr, size;
+ int nid, i = 0;
+
+ if (!kho_enable)
+ return;
+
+ scratch_size_update();
+
+ /* FIXME: deal with node hot-plug/remove */
+ kho_scratch_cnt = num_online_nodes() + 2;
+ size = kho_scratch_cnt * sizeof(*kho_scratch);
+ kho_scratch = memblock_alloc(size, PAGE_SIZE);
+ if (!kho_scratch)
+ goto err_disable_kho;
+
+ /*
+ * reserve scratch area in low memory for lowmem allocations in the
+ * next kernel
+ */
+ size = scratch_size_lowmem;
+ addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0,
+ ARCH_LOW_ADDRESS_LIMIT);
+ if (!addr)
+ goto err_free_scratch_desc;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+
+ /* reserve large contiguous area for allocations without nid */
+ size = scratch_size_global;
+ addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES);
+ if (!addr)
+ goto err_free_scratch_areas;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+
+ for_each_online_node(nid) {
+ size = scratch_size_node(nid);
+ addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
+ 0, MEMBLOCK_ALLOC_ACCESSIBLE,
+ nid, true);
+ if (!addr)
+ goto err_free_scratch_areas;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+ }
+
+ return;
+
+err_free_scratch_areas:
+ for (i--; i >= 0; i--)
+ memblock_phys_free(kho_scratch[i].addr, kho_scratch[i].size);
+err_free_scratch_desc:
+ memblock_free(kho_scratch, kho_scratch_cnt * sizeof(*kho_scratch));
+err_disable_kho:
+ pr_warn("Failed to reserve scratch area, disabling kexec handover\n");
+ kho_enable = false;
+}
+
+/**
+ * kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
+ * @name: name of the sub tree.
+ * @fdt: the sub tree blob.
+ *
+ * Creates a new child node named @name in KHO root FDT and records
+ * the physical address of @fdt. The pages of @fdt must also be preserved
+ * by KHO for the new kernel to retrieve it after kexec.
+ *
+ * A debugfs blob entry is also created at
+ * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured with
+ * CONFIG_KEXEC_HANDOVER_DEBUGFS
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_add_subtree(const char *name, void *fdt)
+{
+ struct kho_sub_fdt *sub_fdt;
+ int err;
+
+ sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL);
+ if (!sub_fdt)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&sub_fdt->l);
+ sub_fdt->name = name;
+ sub_fdt->fdt = fdt;
+
+ mutex_lock(&kho_out.fdts_lock);
+ list_add_tail(&sub_fdt->l, &kho_out.sub_fdts);
+ err = kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false);
+ mutex_unlock(&kho_out.fdts_lock);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(kho_add_subtree);
+
+void kho_remove_subtree(void *fdt)
+{
+ struct kho_sub_fdt *sub_fdt;
+
+ mutex_lock(&kho_out.fdts_lock);
+ list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) {
+ if (sub_fdt->fdt == fdt) {
+ list_del(&sub_fdt->l);
+ kfree(sub_fdt);
+ kho_debugfs_fdt_remove(&kho_out.dbg, fdt);
+ break;
+ }
+ }
+ mutex_unlock(&kho_out.fdts_lock);
+
+}
+EXPORT_SYMBOL_GPL(kho_remove_subtree);
+
+/**
+ * kho_preserve_folio - preserve a folio across kexec.
+ * @folio: folio to preserve.
+ *
+ * Instructs KHO to preserve the whole folio across kexec. The order
+ * will be preserved as well.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_folio(struct folio *folio)
+{
+ const unsigned long pfn = folio_pfn(folio);
+ const unsigned int order = folio_order(folio);
+ struct kho_mem_track *track = &kho_out.track;
+
+ return __kho_preserve_order(track, pfn, order);
+}
+EXPORT_SYMBOL_GPL(kho_preserve_folio);
+
+/**
+ * kho_unpreserve_folio - unpreserve a folio.
+ * @folio: folio to unpreserve.
+ *
+ * Instructs KHO to unpreserve a folio that was preserved by
+ * kho_preserve_folio() before. The provided @folio (pfn and order)
+ * must exactly match a previously preserved folio.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_folio(struct folio *folio)
+{
+ const unsigned long pfn = folio_pfn(folio);
+ const unsigned int order = folio_order(folio);
+ struct kho_mem_track *track = &kho_out.track;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve_order(track, pfn, order);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
+
+/**
+ * kho_preserve_pages - preserve contiguous pages across kexec
+ * @page: first page in the list.
+ * @nr_pages: number of pages.
+ *
+ * Preserve a contiguous list of order 0 pages. Must be restored using
+ * kho_restore_pages() to ensure the pages are restored properly as order 0.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_pages(struct page *page, unsigned int nr_pages)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ const unsigned long start_pfn = page_to_pfn(page);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+ unsigned long pfn = start_pfn;
+ unsigned long failed_pfn = 0;
+ int err = 0;
+
+ while (pfn < end_pfn) {
+ const unsigned int order =
+ min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+
+ err = __kho_preserve_order(track, pfn, order);
+ if (err) {
+ failed_pfn = pfn;
+ break;
+ }
+
+ pfn += 1 << order;
+ }
+
+ if (err)
+ __kho_unpreserve(track, start_pfn, failed_pfn);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(kho_preserve_pages);
+
+/**
+ * kho_unpreserve_pages - unpreserve contiguous pages.
+ * @page: first page in the list.
+ * @nr_pages: number of pages.
+ *
+ * Instructs KHO to unpreserve @nr_pages contigious pages starting from @page.
+ * This call must exactly match a granularity at which memory was originally
+ * preserved by kho_preserve_pages, call with the same @page and
+ * @nr_pages). Unpreserving arbitrary sub-ranges of larger preserved blocks is
+ * not supported.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ const unsigned long start_pfn = page_to_pfn(page);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve(track, start_pfn, end_pfn);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_pages);
+
+struct kho_vmalloc_hdr {
+ DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *);
+};
+
+#define KHO_VMALLOC_SIZE \
+ ((PAGE_SIZE - sizeof(struct kho_vmalloc_hdr)) / \
+ sizeof(phys_addr_t))
+
+struct kho_vmalloc_chunk {
+ struct kho_vmalloc_hdr hdr;
+ phys_addr_t phys[KHO_VMALLOC_SIZE];
+};
+
+static_assert(sizeof(struct kho_vmalloc_chunk) == PAGE_SIZE);
+
+/* vmalloc flags KHO supports */
+#define KHO_VMALLOC_SUPPORTED_FLAGS (VM_ALLOC | VM_ALLOW_HUGE_VMAP)
+
+/* KHO internal flags for vmalloc preservations */
+#define KHO_VMALLOC_ALLOC 0x0001
+#define KHO_VMALLOC_HUGE_VMAP 0x0002
+
+static unsigned short vmalloc_flags_to_kho(unsigned int vm_flags)
+{
+ unsigned short kho_flags = 0;
+
+ if (vm_flags & VM_ALLOC)
+ kho_flags |= KHO_VMALLOC_ALLOC;
+ if (vm_flags & VM_ALLOW_HUGE_VMAP)
+ kho_flags |= KHO_VMALLOC_HUGE_VMAP;
+
+ return kho_flags;
+}
+
+static unsigned int kho_flags_to_vmalloc(unsigned short kho_flags)
+{
+ unsigned int vm_flags = 0;
+
+ if (kho_flags & KHO_VMALLOC_ALLOC)
+ vm_flags |= VM_ALLOC;
+ if (kho_flags & KHO_VMALLOC_HUGE_VMAP)
+ vm_flags |= VM_ALLOW_HUGE_VMAP;
+
+ return vm_flags;
+}
+
+static struct kho_vmalloc_chunk *new_vmalloc_chunk(struct kho_vmalloc_chunk *cur)
+{
+ struct kho_vmalloc_chunk *chunk;
+ int err;
+
+ chunk = (struct kho_vmalloc_chunk *)get_zeroed_page(GFP_KERNEL);
+ if (!chunk)
+ return NULL;
+
+ err = kho_preserve_pages(virt_to_page(chunk), 1);
+ if (err)
+ goto err_free;
+ if (cur)
+ KHOSER_STORE_PTR(cur->hdr.next, chunk);
+ return chunk;
+
+err_free:
+ free_page((unsigned long)chunk);
+ return NULL;
+}
+
+static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
+
+ __kho_unpreserve(track, pfn, pfn + 1);
+
+ for (int i = 0; chunk->phys[i]; i++) {
+ pfn = PHYS_PFN(chunk->phys[i]);
+ __kho_unpreserve(track, pfn, pfn + 1);
+ }
+}
+
+static void kho_vmalloc_free_chunks(struct kho_vmalloc *kho_vmalloc)
+{
+ struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(kho_vmalloc->first);
+
+ while (chunk) {
+ struct kho_vmalloc_chunk *tmp = chunk;
+
+ kho_vmalloc_unpreserve_chunk(chunk);
+
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ free_page((unsigned long)tmp);
+ }
+}
+
+/**
+ * kho_preserve_vmalloc - preserve memory allocated with vmalloc() across kexec
+ * @ptr: pointer to the area in vmalloc address space
+ * @preservation: placeholder for preservation metadata
+ *
+ * Instructs KHO to preserve the area in vmalloc address space at @ptr. The
+ * physical pages mapped at @ptr will be preserved and on successful return
+ * @preservation will hold the physical address of a structure that describes
+ * the preservation.
+ *
+ * NOTE: The memory allocated with vmalloc_node() variants cannot be reliably
+ * restored on the same node
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
+{
+ struct kho_vmalloc_chunk *chunk;
+ struct vm_struct *vm = find_vm_area(ptr);
+ unsigned int order, flags, nr_contig_pages;
+ unsigned int idx = 0;
+ int err;
+
+ if (!vm)
+ return -EINVAL;
+
+ if (vm->flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
+ return -EOPNOTSUPP;
+
+ flags = vmalloc_flags_to_kho(vm->flags);
+ order = get_vm_area_page_order(vm);
+
+ chunk = new_vmalloc_chunk(NULL);
+ if (!chunk)
+ return -ENOMEM;
+ KHOSER_STORE_PTR(preservation->first, chunk);
+
+ nr_contig_pages = (1 << order);
+ for (int i = 0; i < vm->nr_pages; i += nr_contig_pages) {
+ phys_addr_t phys = page_to_phys(vm->pages[i]);
+
+ err = kho_preserve_pages(vm->pages[i], nr_contig_pages);
+ if (err)
+ goto err_free;
+
+ chunk->phys[idx++] = phys;
+ if (idx == ARRAY_SIZE(chunk->phys)) {
+ chunk = new_vmalloc_chunk(chunk);
+ if (!chunk)
+ goto err_free;
+ idx = 0;
+ }
+ }
+
+ preservation->total_pages = vm->nr_pages;
+ preservation->flags = flags;
+ preservation->order = order;
+
+ return 0;
+
+err_free:
+ kho_vmalloc_free_chunks(preservation);
+ return err;
+}
+EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
+
+/**
+ * kho_restore_vmalloc - recreates and populates an area in vmalloc address
+ * space from the preserved memory.
+ * @preservation: preservation metadata.
+ *
+ * Recreates an area in vmalloc address space and populates it with memory that
+ * was preserved using kho_preserve_vmalloc().
+ *
+ * Return: pointer to the area in the vmalloc address space, NULL on failure.
+ */
+void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
+{
+ struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(preservation->first);
+ unsigned int align, order, shift, vm_flags;
+ unsigned long total_pages, contig_pages;
+ unsigned long addr, size;
+ struct vm_struct *area;
+ struct page **pages;
+ unsigned int idx = 0;
+ int err;
+
+ vm_flags = kho_flags_to_vmalloc(preservation->flags);
+ if (vm_flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
+ return NULL;
+
+ total_pages = preservation->total_pages;
+ pages = kvmalloc_array(total_pages, sizeof(*pages), GFP_KERNEL);
+ if (!pages)
+ return NULL;
+ order = preservation->order;
+ contig_pages = (1 << order);
+ shift = PAGE_SHIFT + order;
+ align = 1 << shift;
+
+ while (chunk) {
+ struct page *page;
+
+ for (int i = 0; chunk->phys[i]; i++) {
+ phys_addr_t phys = chunk->phys[i];
+
+ if (idx + contig_pages > total_pages)
+ goto err_free_pages_array;
+
+ page = kho_restore_pages(phys, contig_pages);
+ if (!page)
+ goto err_free_pages_array;
+
+ for (int j = 0; j < contig_pages; j++)
+ pages[idx++] = page;
+
+ phys += contig_pages * PAGE_SIZE;
+ }
+
+ page = kho_restore_pages(virt_to_phys(chunk), 1);
+ if (!page)
+ goto err_free_pages_array;
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ __free_page(page);
+ }
+
+ if (idx != total_pages)
+ goto err_free_pages_array;
+
+ area = __get_vm_area_node(total_pages * PAGE_SIZE, align, shift,
+ vm_flags, VMALLOC_START, VMALLOC_END,
+ NUMA_NO_NODE, GFP_KERNEL,
+ __builtin_return_address(0));
+ if (!area)
+ goto err_free_pages_array;
+
+ addr = (unsigned long)area->addr;
+ size = get_vm_area_size(area);
+ err = vmap_pages_range(addr, addr + size, PAGE_KERNEL, pages, shift);
+ if (err)
+ goto err_free_vm_area;
+
+ area->nr_pages = total_pages;
+ area->pages = pages;
+
+ return area->addr;
+
+err_free_vm_area:
+ free_vm_area(area);
+err_free_pages_array:
+ kvfree(pages);
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
+
+static int __kho_abort(void)
+{
+ if (kho_out.preserved_mem_map) {
+ kho_mem_ser_free(kho_out.preserved_mem_map);
+ kho_out.preserved_mem_map = NULL;
+ }
+
+ return 0;
+}
+
+int kho_abort(void)
+{
+ int ret = 0;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ guard(mutex)(&kho_out.lock);
+ if (!kho_out.finalized)
+ return -ENOENT;
+
+ ret = __kho_abort();
+ if (ret)
+ return ret;
+
+ kho_out.finalized = false;
+
+ kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt);
+
+ return 0;
+}
+
+static int __kho_finalize(void)
+{
+ int err = 0;
+ u64 *preserved_mem_map;
+ void *root = kho_out.fdt;
+ struct kho_sub_fdt *fdt;
+
+ err |= fdt_create(root, PAGE_SIZE);
+ err |= fdt_finish_reservemap(root);
+ err |= fdt_begin_node(root, "");
+ err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
+ /*
+ * Reserve the preserved-memory-map property in the root FDT, so
+ * that all property definitions will precede subnodes created by
+ * KHO callers.
+ */
+ err |= fdt_property_placeholder(root, PROP_PRESERVED_MEMORY_MAP,
+ sizeof(*preserved_mem_map),
+ (void **)&preserved_mem_map);
+ if (err)
+ goto abort;
+
+ err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
+ if (err)
+ goto abort;
+
+ err = kho_mem_serialize(&kho_out);
+ if (err)
+ goto abort;
+
+ *preserved_mem_map = (u64)virt_to_phys(kho_out.preserved_mem_map);
+
+ mutex_lock(&kho_out.fdts_lock);
+ list_for_each_entry(fdt, &kho_out.sub_fdts, l) {
+ phys_addr_t phys = virt_to_phys(fdt->fdt);
+
+ err |= fdt_begin_node(root, fdt->name);
+ err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
+ err |= fdt_end_node(root);
+ };
+ mutex_unlock(&kho_out.fdts_lock);
+
+ err |= fdt_end_node(root);
+ err |= fdt_finish(root);
+
+abort:
+ if (err) {
+ pr_err("Failed to convert KHO state tree: %d\n", err);
+ __kho_abort();
+ }
+
+ return err;
+}
+
+int kho_finalize(void)
+{
+ int ret;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ guard(mutex)(&kho_out.lock);
+ if (kho_out.finalized)
+ return -EEXIST;
+
+ ret = __kho_finalize();
+ if (ret)
+ return ret;
+
+ kho_out.finalized = true;
+
+ return kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
+ kho_out.fdt, true);
+}
+
+bool kho_finalized(void)
+{
+ guard(mutex)(&kho_out.lock);
+ return kho_out.finalized;
+}
+
+struct kho_in {
+ phys_addr_t fdt_phys;
+ phys_addr_t scratch_phys;
+ struct kho_debugfs dbg;
+};
+
+static struct kho_in kho_in = {
+};
+
+static const void *kho_get_fdt(void)
+{
+ return kho_in.fdt_phys ? phys_to_virt(kho_in.fdt_phys) : NULL;
+}
+
+/**
+ * is_kho_boot - check if current kernel was booted via KHO-enabled
+ * kexec
+ *
+ * This function checks if the current kernel was loaded through a kexec
+ * operation with KHO enabled, by verifying that a valid KHO FDT
+ * was passed.
+ *
+ * Note: This function returns reliable results only after
+ * kho_populate() has been called during early boot. Before that,
+ * it may return false even if KHO data is present.
+ *
+ * Return: true if booted via KHO-enabled kexec, false otherwise
+ */
+bool is_kho_boot(void)
+{
+ return !!kho_get_fdt();
+}
+EXPORT_SYMBOL_GPL(is_kho_boot);
+
+/**
+ * kho_retrieve_subtree - retrieve a preserved sub FDT by its name.
+ * @name: the name of the sub FDT passed to kho_add_subtree().
+ * @phys: if found, the physical address of the sub FDT is stored in @phys.
+ *
+ * Retrieve a preserved sub FDT named @name and store its physical
+ * address in @phys.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
+{
+ const void *fdt = kho_get_fdt();
+ const u64 *val;
+ int offset, len;
+
+ if (!fdt)
+ return -ENOENT;
+
+ if (!phys)
+ return -EINVAL;
+
+ offset = fdt_subnode_offset(fdt, 0, name);
+ if (offset < 0)
+ return -ENOENT;
+
+ val = fdt_getprop(fdt, offset, PROP_SUB_FDT, &len);
+ if (!val || len != sizeof(*val))
+ return -EINVAL;
+
+ *phys = (phys_addr_t)*val;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
+
+static __init int kho_init(void)
+{
+ int err = 0;
+ const void *fdt = kho_get_fdt();
+ struct page *fdt_page;
+
+ if (!kho_enable)
+ return 0;
+
+ fdt_page = alloc_page(GFP_KERNEL);
+ if (!fdt_page) {
+ err = -ENOMEM;
+ goto err_free_scratch;
+ }
+ kho_out.fdt = page_to_virt(fdt_page);
+
+ err = kho_debugfs_init();
+ if (err)
+ goto err_free_fdt;
+
+ err = kho_out_debugfs_init(&kho_out.dbg);
+ if (err)
+ goto err_free_fdt;
+
+ if (fdt) {
+ kho_in_debugfs_init(&kho_in.dbg, fdt);
+ return 0;
+ }
+
+ for (int i = 0; i < kho_scratch_cnt; i++) {
+ unsigned long base_pfn = PHYS_PFN(kho_scratch[i].addr);
+ unsigned long count = kho_scratch[i].size >> PAGE_SHIFT;
+ unsigned long pfn;
+
+ for (pfn = base_pfn; pfn < base_pfn + count;
+ pfn += pageblock_nr_pages)
+ init_cma_reserved_pageblock(pfn_to_page(pfn));
+ }
+
+ return 0;
+
+err_free_fdt:
+ put_page(fdt_page);
+ kho_out.fdt = NULL;
+err_free_scratch:
+ for (int i = 0; i < kho_scratch_cnt; i++) {
+ void *start = __va(kho_scratch[i].addr);
+ void *end = start + kho_scratch[i].size;
+
+ free_reserved_area(start, end, -1, "");
+ }
+ kho_enable = false;
+ return err;
+}
+fs_initcall(kho_init);
+
+static void __init kho_release_scratch(void)
+{
+ phys_addr_t start, end;
+ u64 i;
+
+ memmap_init_kho_scratch_pages();
+
+ /*
+ * Mark scratch mem as CMA before we return it. That way we
+ * ensure that no kernel allocations happen on it. That means
+ * we can reuse it as scratch memory again later.
+ */
+ __for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
+ MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
+ ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
+ ulong end_pfn = pageblock_align(PFN_UP(end));
+ ulong pfn;
+
+ for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
+ init_pageblock_migratetype(pfn_to_page(pfn),
+ MIGRATE_CMA, false);
+ }
+}
+
+void __init kho_memory_init(void)
+{
+ struct folio *folio;
+
+ if (kho_in.scratch_phys) {
+ kho_scratch = phys_to_virt(kho_in.scratch_phys);
+ kho_release_scratch();
+
+ kho_mem_deserialize(kho_get_fdt());
+ folio = kho_restore_folio(kho_in.fdt_phys);
+ if (!folio)
+ pr_warn("failed to restore folio for KHO fdt\n");
+ } else {
+ kho_reserve_scratch();
+ }
+}
+
+void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
+ phys_addr_t scratch_phys, u64 scratch_len)
+{
+ void *fdt = NULL;
+ struct kho_scratch *scratch = NULL;
+ int err = 0;
+ unsigned int scratch_cnt = scratch_len / sizeof(*kho_scratch);
+
+ /* Validate the input FDT */
+ fdt = early_memremap(fdt_phys, fdt_len);
+ if (!fdt) {
+ pr_warn("setup: failed to memremap FDT (0x%llx)\n", fdt_phys);
+ err = -EFAULT;
+ goto out;
+ }
+ err = fdt_check_header(fdt);
+ if (err) {
+ pr_warn("setup: handover FDT (0x%llx) is invalid: %d\n",
+ fdt_phys, err);
+ err = -EINVAL;
+ goto out;
+ }
+ err = fdt_node_check_compatible(fdt, 0, KHO_FDT_COMPATIBLE);
+ if (err) {
+ pr_warn("setup: handover FDT (0x%llx) is incompatible with '%s': %d\n",
+ fdt_phys, KHO_FDT_COMPATIBLE, err);
+ err = -EINVAL;
+ goto out;
+ }
+
+ scratch = early_memremap(scratch_phys, scratch_len);
+ if (!scratch) {
+ pr_warn("setup: failed to memremap scratch (phys=0x%llx, len=%lld)\n",
+ scratch_phys, scratch_len);
+ err = -EFAULT;
+ goto out;
+ }
+
+ /*
+ * We pass a safe contiguous blocks of memory to use for early boot
+ * purporses from the previous kernel so that we can resize the
+ * memblock array as needed.
+ */
+ for (int i = 0; i < scratch_cnt; i++) {
+ struct kho_scratch *area = &scratch[i];
+ u64 size = area->size;
+
+ memblock_add(area->addr, size);
+ err = memblock_mark_kho_scratch(area->addr, size);
+ if (WARN_ON(err)) {
+ pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %d",
+ &area->addr, &size, err);
+ goto out;
+ }
+ pr_debug("Marked 0x%pa+0x%pa as scratch", &area->addr, &size);
+ }
+
+ memblock_reserve(scratch_phys, scratch_len);
+
+ /*
+ * Now that we have a viable region of scratch memory, let's tell
+ * the memblocks allocator to only use that for any allocations.
+ * That way we ensure that nothing scribbles over in use data while
+ * we initialize the page tables which we will need to ingest all
+ * memory reservations from the previous kernel.
+ */
+ memblock_set_kho_scratch_only();
+
+ kho_in.fdt_phys = fdt_phys;
+ kho_in.scratch_phys = scratch_phys;
+ kho_scratch_cnt = scratch_cnt;
+ pr_info("found kexec handover data. Will skip init for some devices\n");
+
+out:
+ if (fdt)
+ early_memunmap(fdt, fdt_len);
+ if (scratch)
+ early_memunmap(scratch, scratch_len);
+ if (err)
+ pr_warn("disabling KHO revival: %d\n", err);
+}
+
+/* Helper functions for kexec_file_load */
+
+int kho_fill_kimage(struct kimage *image)
+{
+ ssize_t scratch_size;
+ int err = 0;
+ struct kexec_buf scratch;
+
+ if (!kho_out.finalized)
+ return 0;
+
+ image->kho.fdt = virt_to_phys(kho_out.fdt);
+
+ scratch_size = sizeof(*kho_scratch) * kho_scratch_cnt;
+ scratch = (struct kexec_buf){
+ .image = image,
+ .buffer = kho_scratch,
+ .bufsz = scratch_size,
+ .mem = KEXEC_BUF_MEM_UNKNOWN,
+ .memsz = scratch_size,
+ .buf_align = SZ_64K, /* Makes it easier to map */
+ .buf_max = ULONG_MAX,
+ .top_down = true,
+ };
+ err = kexec_add_buffer(&scratch);
+ if (err)
+ return err;
+ image->kho.scratch = &image->segment[image->nr_segments - 1];
+
+ return 0;
+}
+
+static int kho_walk_scratch(struct kexec_buf *kbuf,
+ int (*func)(struct resource *, void *))
+{
+ int ret = 0;
+ int i;
+
+ for (i = 0; i < kho_scratch_cnt; i++) {
+ struct resource res = {
+ .start = kho_scratch[i].addr,
+ .end = kho_scratch[i].addr + kho_scratch[i].size - 1,
+ };
+
+ /* Try to fit the kimage into our KHO scratch region */
+ ret = func(&res, kbuf);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+int kho_locate_mem_hole(struct kexec_buf *kbuf,
+ int (*func)(struct resource *, void *))
+{
+ int ret;
+
+ if (!kho_enable || kbuf->image->type == KEXEC_TYPE_CRASH)
+ return 1;
+
+ ret = kho_walk_scratch(kbuf, func);
+
+ return ret == 1 ? 0 : -EADDRNOTAVAIL;
+}
diff --git a/kernel/liveupdate/kexec_handover_debug.c a/kernel/liveupdate/kexec_handover_debug.c
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_debug.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover.c - kexec handover metadata processing
+ * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
+ * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
+ * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/libfdt.h>
+#include <linux/mm.h>
+#include "kexec_handover_internal.h"
+
+static struct dentry *debugfs_root;
+
+struct fdt_debugfs {
+ struct list_head list;
+ struct debugfs_blob_wrapper wrapper;
+ struct dentry *file;
+};
+
+static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
+ const char *name, const void *fdt)
+{
+ struct fdt_debugfs *f;
+ struct dentry *file;
+
+ f = kmalloc(sizeof(*f), GFP_KERNEL);
+ if (!f)
+ return -ENOMEM;
+
+ f->wrapper.data = (void *)fdt;
+ f->wrapper.size = fdt_totalsize(fdt);
+
+ file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
+ if (IS_ERR(file)) {
+ kfree(f);
+ return PTR_ERR(file);
+ }
+
+ f->file = file;
+ list_add(&f->list, list);
+
+ return 0;
+}
+
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root)
+{
+ struct dentry *dir;
+
+ if (root)
+ dir = dbg->dir;
+ else
+ dir = dbg->sub_fdt_dir;
+
+ return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
+}
+
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt)
+{
+ struct fdt_debugfs *ff;
+
+ list_for_each_entry(ff, &dbg->fdt_list, list) {
+ if (ff->wrapper.data == fdt) {
+ debugfs_remove(ff->file);
+ list_del(&ff->list);
+ kfree(ff);
+ break;
+ }
+ }
+}
+
+static int kho_out_finalize_get(void *data, u64 *val)
+{
+ *val = kho_finalized();
+
+ return 0;
+}
+
+static int kho_out_finalize_set(void *data, u64 _val)
+{
+ return (!!_val) ? kho_finalize() : kho_abort();
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
+ kho_out_finalize_set, "%llu\n");
+
+static int scratch_phys_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_phys);
+
+static int scratch_len_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].size);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_len);
+
+__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
+{
+ struct dentry *dir, *sub_fdt_dir;
+ int err, child;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("in", debugfs_root);
+ if (IS_ERR(dir)) {
+ err = PTR_ERR(dir);
+ goto err_out;
+ }
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir)) {
+ err = PTR_ERR(sub_fdt_dir);
+ goto err_rmdir;
+ }
+
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt);
+ if (err)
+ goto err_rmdir;
+
+ fdt_for_each_subnode(child, fdt, 0) {
+ int len = 0;
+ const char *name = fdt_get_name(fdt, child, NULL);
+ const u64 *fdt_phys;
+
+ fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
+ if (!fdt_phys)
+ continue;
+ if (len != sizeof(*fdt_phys)) {
+ pr_warn("node %s prop fdt has invalid length: %d\n",
+ name, len);
+ continue;
+ }
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
+ phys_to_virt(*fdt_phys));
+ if (err) {
+ pr_warn("failed to add fdt %s to debugfs: %d\n", name,
+ err);
+ continue;
+ }
+ }
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+
+ return;
+err_rmdir:
+ debugfs_remove_recursive(dir);
+err_out:
+ /*
+ * Failure to create /sys/kernel/debug/kho/in does not prevent
+ * reviving state from KHO and setting up KHO for the next
+ * kexec.
+ */
+ if (err)
+ pr_err("failed exposing handover FDT in debugfs: %d\n", err);
+}
+
+__init int kho_out_debugfs_init(struct kho_debugfs *dbg)
+{
+ struct dentry *dir, *f, *sub_fdt_dir;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("out", debugfs_root);
+ if (IS_ERR(dir))
+ return -ENOMEM;
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
+ &scratch_phys_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_len", 0400, dir, NULL,
+ &scratch_len_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("finalize", 0600, dir, NULL,
+ &kho_out_finalize_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+ return 0;
+
+err_rmdir:
+ debugfs_remove_recursive(dir);
+ return -ENOENT;
+}
+
+__init int kho_debugfs_init(void)
+{
+ debugfs_root = debugfs_create_dir("kho", NULL);
+ if (IS_ERR(debugfs_root))
+ return -ENOENT;
+ return 0;
+}
diff --git a/kernel/liveupdate/kexec_handover_internal.h a/kernel/liveupdate/kexec_handover_internal.h
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_internal.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
+#define LINUX_KEXEC_HANDOVER_INTERNAL_H
+
+#include <linux/kexec_handover.h>
+#include <linux/list.h>
+#include <linux/types.h>
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
+#include <linux/debugfs.h>
+
+struct kho_debugfs {
+ struct dentry *dir;
+ struct dentry *sub_fdt_dir;
+ struct list_head fdt_list;
+};
+
+#else
+struct kho_debugfs {};
+#endif
+
+extern struct kho_scratch *kho_scratch;
+extern unsigned int kho_scratch_cnt;
+
+bool kho_finalized(void);
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
+int kho_debugfs_init(void);
+void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
+int kho_out_debugfs_init(struct kho_debugfs *dbg);
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root);
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt);
+#else
+static inline int kho_debugfs_init(void) { return 0; }
+static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
+ const void *fdt) { }
+static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
+static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root) { return 0; }
+static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg,
+ void *fdt) { }
+#endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */
+
+#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
diff --git a/kernel/liveupdate/Makefile a/kernel/liveupdate/Makefile
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS) += kexec_handover_debug.o
--- a/kernel/Makefile~liveupdate-kho-move-to-kernel-liveupdate
+++ a/kernel/Makefile
@@ -52,6 +52,7 @@ obj-y += printk/
obj-y += irq/
obj-y += rcu/
obj-y += livepatch/
+obj-y += liveupdate/
obj-y += dma/
obj-y += entry/
obj-y += unwind/
@@ -82,8 +83,6 @@ obj-$(CONFIG_CRASH_DUMP_KUNIT_TEST) += c
obj-$(CONFIG_KEXEC) += kexec.o
obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
-obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
-obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS) += kexec_handover_debug.o
obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup/
--- a/MAINTAINERS~liveupdate-kho-move-to-kernel-liveupdate
+++ a/MAINTAINERS
@@ -13761,7 +13761,7 @@ S: Maintained
F: Documentation/admin-guide/mm/kho.rst
F: Documentation/core-api/kho/*
F: include/linux/kexec_handover.h
-F: kernel/kexec_handover*
+F: kernel/liveupdate/kexec_handover*
F: tools/testing/selftests/kho/
KEYS-ENCRYPTED
_
Patches currently in -mm which might be from pasha.tatashin@soleen.com are
kho-allow-to-drive-kho-from-within-kernel.patch
kho-make-debugfs-interface-optional.patch
kho-add-interfaces-to-unpreserve-folios-and-page-ranes.patch
kho-dont-unpreserve-memory-during-abort.patch
liveupdate-kho-move-to-kernel-liveupdate.patch
kho-move-kho-debugfs-directory-to-liveupdate.patch
^ permalink raw reply [flat|nested] 3+ messages in thread
* + liveupdate-kho-move-to-kernel-liveupdate.patch added to mm-nonmm-unstable branch
@ 2025-10-26 4:06 Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2025-10-26 4:06 UTC (permalink / raw)
To: mm-commits, tj, rppt, rdunlap, pratyush, ojeda, masahiroy, jgg,
jgg, graf, corbet, brauner, pasha.tatashin, akpm
The patch titled
Subject: liveupdate: kho: move to kernel/liveupdate
has been added to the -mm mm-nonmm-unstable branch. Its filename is
liveupdate-kho-move-to-kernel-liveupdate.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/liveupdate-kho-move-to-kernel-liveupdate.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: liveupdate: kho: move to kernel/liveupdate
Date: Fri, 24 Oct 2025 12:10:00 -0400
Move KHO to kernel/liveupdate/ in preparation of placing all Live Update
core kernel related files to the same place.
Link: https://lkml.kernel.org/r/20251024161002.747372-7-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
Documentation/core-api/kho/concepts.rst | 2
MAINTAINERS | 2
init/Kconfig | 2
kernel/Kconfig.kexec | 34
kernel/Makefile | 4
kernel/kexec_handover.c | 1527 ------------------
kernel/kexec_handover_debug.c | 25
kernel/kexec_handover_debugfs.c | 219 --
kernel/kexec_handover_internal.h | 54
kernel/liveupdate/Kconfig | 39
kernel/liveupdate/Makefile | 5
kernel/liveupdate/kexec_handover.c | 1527 ++++++++++++++++++
kernel/liveupdate/kexec_handover_debug.c | 25
kernel/liveupdate/kexec_handover_debugfs.c | 219 ++
kernel/liveupdate/kexec_handover_internal.h | 54
15 files changed, 1874 insertions(+), 1864 deletions(-)
--- a/Documentation/core-api/kho/concepts.rst~liveupdate-kho-move-to-kernel-liveupdate
+++ a/Documentation/core-api/kho/concepts.rst
@@ -70,5 +70,5 @@ in the FDT. That state is called the KHO
Public API
==========
-.. kernel-doc:: kernel/kexec_handover.c
+.. kernel-doc:: kernel/liveupdate/kexec_handover.c
:export:
--- a/init/Kconfig~liveupdate-kho-move-to-kernel-liveupdate
+++ a/init/Kconfig
@@ -2156,6 +2156,8 @@ config TRACEPOINTS
source "kernel/Kconfig.kexec"
+source "kernel/liveupdate/Kconfig"
+
endmenu # General setup
source "arch/Kconfig"
--- a/kernel/Kconfig.kexec~liveupdate-kho-move-to-kernel-liveupdate
+++ a/kernel/Kconfig.kexec
@@ -94,40 +94,6 @@ config KEXEC_JUMP
Jump between original kernel and kexeced kernel and invoke
code in physical address mode via KEXEC
-config KEXEC_HANDOVER
- bool "kexec handover"
- depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
- depends on !DEFERRED_STRUCT_PAGE_INIT
- select MEMBLOCK_KHO_SCRATCH
- select KEXEC_FILE
- select DEBUG_FS
- select LIBFDT
- select CMA
- help
- Allow kexec to hand over state across kernels by generating and
- passing additional metadata to the target kernel. This is useful
- to keep data or state alive across the kexec. For this to work,
- both source and target kernels need to have this option enabled.
-
-config KEXEC_HANDOVER_DEBUG
- bool "Enable Kexec Handover debug checks"
- depends on KEXEC_HANDOVER_DEBUGFS
- help
- This option enables extra sanity checks for the Kexec Handover
- subsystem. Since, KHO performance is crucial in live update
- scenarios and the extra code might be adding overhead it is
- only optionally enabled.
-
-config KEXEC_HANDOVER_DEBUGFS
- bool "kexec handover debugfs interface"
- depends on KEXEC_HANDOVER
- depends on DEBUG_FS
- help
- Allow to control kexec handover device tree via debugfs
- interface, i.e. finalize the state or aborting the finalization.
- Also, enables inspecting the KHO fdt trees with the debugfs binary
- blobs.
-
config CRASH_DUMP
bool "kernel crash dumps"
default ARCH_DEFAULT_CRASH_DUMP
diff --git a/kernel/kexec_handover.c a/kernel/kexec_handover.c
deleted file mode 100644
--- a/kernel/kexec_handover.c
+++ /dev/null
@@ -1,1527 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover.c - kexec handover metadata processing
- * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
- * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
- * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include <linux/cleanup.h>
-#include <linux/cma.h>
-#include <linux/count_zeros.h>
-#include <linux/kexec.h>
-#include <linux/kexec_handover.h>
-#include <linux/libfdt.h>
-#include <linux/list.h>
-#include <linux/memblock.h>
-#include <linux/page-isolation.h>
-#include <linux/vmalloc.h>
-
-#include <asm/early_ioremap.h>
-
-#include "kexec_handover_internal.h"
-/*
- * KHO is tightly coupled with mm init and needs access to some of mm
- * internal APIs.
- */
-#include "../mm/internal.h"
-#include "kexec_internal.h"
-#include "kexec_handover_internal.h"
-
-#define KHO_FDT_COMPATIBLE "kho-v1"
-#define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
-#define PROP_SUB_FDT "fdt"
-
-#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
-
-/*
- * KHO uses page->private, which is an unsigned long, to store page metadata.
- * Use it to store both the magic and the order.
- */
-union kho_page_info {
- unsigned long page_private;
- struct {
- unsigned int order;
- unsigned int magic;
- };
-};
-
-static_assert(sizeof(union kho_page_info) == sizeof(((struct page *)0)->private));
-
-static bool kho_enable __ro_after_init;
-
-bool kho_is_enabled(void)
-{
- return kho_enable;
-}
-EXPORT_SYMBOL_GPL(kho_is_enabled);
-
-static int __init kho_parse_enable(char *p)
-{
- return kstrtobool(p, &kho_enable);
-}
-early_param("kho", kho_parse_enable);
-
-/*
- * Keep track of memory that is to be preserved across KHO.
- *
- * The serializing side uses two levels of xarrays to manage chunks of per-order
- * PAGE_SIZE byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order
- * of a 8TB system would fit inside a single 4096 byte bitmap. For order 0
- * allocations each bitmap will cover 128M of address space. Thus, for 16G of
- * memory at most 512K of bitmap memory will be needed for order 0.
- *
- * This approach is fully incremental, as the serialization progresses folios
- * can continue be aggregated to the tracker. The final step, immediately prior
- * to kexec would serialize the xarray information into a linked list for the
- * successor kernel to parse.
- */
-
-#define PRESERVE_BITS (PAGE_SIZE * 8)
-
-struct kho_mem_phys_bits {
- DECLARE_BITMAP(preserve, PRESERVE_BITS);
-};
-
-static_assert(sizeof(struct kho_mem_phys_bits) == PAGE_SIZE);
-
-struct kho_mem_phys {
- /*
- * Points to kho_mem_phys_bits, a sparse bitmap array. Each bit is sized
- * to order.
- */
- struct xarray phys_bits;
-};
-
-struct kho_mem_track {
- /* Points to kho_mem_phys, each order gets its own bitmap tree */
- struct xarray orders;
-};
-
-struct khoser_mem_chunk;
-
-struct kho_sub_fdt {
- struct list_head l;
- const char *name;
- void *fdt;
-};
-
-struct kho_out {
- void *fdt;
- bool finalized;
- struct mutex lock; /* protects KHO FDT finalization */
-
- struct list_head sub_fdts;
- struct mutex fdts_lock;
-
- struct kho_mem_track track;
- /* First chunk of serialized preserved memory map */
- struct khoser_mem_chunk *preserved_mem_map;
-
- struct kho_debugfs dbg;
-};
-
-static struct kho_out kho_out = {
- .lock = __MUTEX_INITIALIZER(kho_out.lock),
- .track = {
- .orders = XARRAY_INIT(kho_out.track.orders, 0),
- },
- .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts),
- .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock),
- .finalized = false,
-};
-
-static void *xa_load_or_alloc(struct xarray *xa, unsigned long index)
-{
- void *res = xa_load(xa, index);
-
- if (res)
- return res;
-
- void *elm __free(free_page) = (void *)get_zeroed_page(GFP_KERNEL);
-
- if (!elm)
- return ERR_PTR(-ENOMEM);
-
- if (WARN_ON(kho_scratch_overlap(virt_to_phys(elm), PAGE_SIZE)))
- return ERR_PTR(-EINVAL);
-
- res = xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
- if (xa_is_err(res))
- return ERR_PTR(xa_err(res));
- else if (res)
- return res;
-
- return no_free_ptr(elm);
-}
-
-static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn,
- unsigned int order)
-{
- struct kho_mem_phys_bits *bits;
- struct kho_mem_phys *physxa;
- const unsigned long pfn_high = pfn >> order;
-
- physxa = xa_load(&track->orders, order);
- if (!physxa)
- return;
-
- bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
- if (!bits)
- return;
-
- clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
-}
-
-static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
- unsigned long end_pfn)
-{
- unsigned int order;
-
- while (pfn < end_pfn) {
- order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
- __kho_unpreserve_order(track, pfn, order);
-
- pfn += 1 << order;
- }
-}
-
-static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
- unsigned int order)
-{
- struct kho_mem_phys_bits *bits;
- struct kho_mem_phys *physxa, *new_physxa;
- const unsigned long pfn_high = pfn >> order;
-
- might_sleep();
-
- if (kho_out.finalized)
- return -EBUSY;
-
- physxa = xa_load(&track->orders, order);
- if (!physxa) {
- int err;
-
- new_physxa = kzalloc(sizeof(*physxa), GFP_KERNEL);
- if (!new_physxa)
- return -ENOMEM;
-
- xa_init(&new_physxa->phys_bits);
- physxa = xa_cmpxchg(&track->orders, order, NULL, new_physxa,
- GFP_KERNEL);
-
- err = xa_err(physxa);
- if (err || physxa) {
- xa_destroy(&new_physxa->phys_bits);
- kfree(new_physxa);
-
- if (err)
- return err;
- } else {
- physxa = new_physxa;
- }
- }
-
- bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
- if (IS_ERR(bits))
- return PTR_ERR(bits);
-
- set_bit(pfn_high % PRESERVE_BITS, bits->preserve);
-
- return 0;
-}
-
-static struct page *kho_restore_page(phys_addr_t phys)
-{
- struct page *page = pfn_to_online_page(PHYS_PFN(phys));
- union kho_page_info info;
- unsigned int nr_pages;
-
- if (!page)
- return NULL;
-
- info.page_private = page->private;
- /*
- * deserialize_bitmap() only sets the magic on the head page. This magic
- * check also implicitly makes sure phys is order-aligned since for
- * non-order-aligned phys addresses, magic will never be set.
- */
- if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER))
- return NULL;
- nr_pages = (1 << info.order);
-
- /* Clear private to make sure later restores on this page error out. */
- page->private = 0;
- /* Head page gets refcount of 1. */
- set_page_count(page, 1);
-
- /* For higher order folios, tail pages get a page count of zero. */
- for (unsigned int i = 1; i < nr_pages; i++)
- set_page_count(page + i, 0);
-
- if (info.order > 0)
- prep_compound_page(page, info.order);
-
- adjust_managed_page_count(page, nr_pages);
- return page;
-}
-
-/**
- * kho_restore_folio - recreates the folio from the preserved memory.
- * @phys: physical address of the folio.
- *
- * Return: pointer to the struct folio on success, NULL on failure.
- */
-struct folio *kho_restore_folio(phys_addr_t phys)
-{
- struct page *page = kho_restore_page(phys);
-
- return page ? page_folio(page) : NULL;
-}
-EXPORT_SYMBOL_GPL(kho_restore_folio);
-
-/**
- * kho_restore_pages - restore list of contiguous order 0 pages.
- * @phys: physical address of the first page.
- * @nr_pages: number of pages.
- *
- * Restore a contiguous list of order 0 pages that was preserved with
- * kho_preserve_pages().
- *
- * Return: 0 on success, error code on failure
- */
-struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages)
-{
- const unsigned long start_pfn = PHYS_PFN(phys);
- const unsigned long end_pfn = start_pfn + nr_pages;
- unsigned long pfn = start_pfn;
-
- while (pfn < end_pfn) {
- const unsigned int order =
- min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
- struct page *page = kho_restore_page(PFN_PHYS(pfn));
-
- if (!page)
- return NULL;
- split_page(page, order);
- pfn += 1 << order;
- }
-
- return pfn_to_page(start_pfn);
-}
-EXPORT_SYMBOL_GPL(kho_restore_pages);
-
-/* Serialize and deserialize struct kho_mem_phys across kexec
- *
- * Record all the bitmaps in a linked list of pages for the next kernel to
- * process. Each chunk holds bitmaps of the same order and each block of bitmaps
- * starts at a given physical address. This allows the bitmaps to be sparse. The
- * xarray is used to store them in a tree while building up the data structure,
- * but the KHO successor kernel only needs to process them once in order.
- *
- * All of this memory is normal kmalloc() memory and is not marked for
- * preservation. The successor kernel will remain isolated to the scratch space
- * until it completes processing this list. Once processed all the memory
- * storing these ranges will be marked as free.
- */
-
-struct khoser_mem_bitmap_ptr {
- phys_addr_t phys_start;
- DECLARE_KHOSER_PTR(bitmap, struct kho_mem_phys_bits *);
-};
-
-struct khoser_mem_chunk_hdr {
- DECLARE_KHOSER_PTR(next, struct khoser_mem_chunk *);
- unsigned int order;
- unsigned int num_elms;
-};
-
-#define KHOSER_BITMAP_SIZE \
- ((PAGE_SIZE - sizeof(struct khoser_mem_chunk_hdr)) / \
- sizeof(struct khoser_mem_bitmap_ptr))
-
-struct khoser_mem_chunk {
- struct khoser_mem_chunk_hdr hdr;
- struct khoser_mem_bitmap_ptr bitmaps[KHOSER_BITMAP_SIZE];
-};
-
-static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE);
-
-static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk,
- unsigned long order)
-{
- struct khoser_mem_chunk *chunk __free(free_page) = NULL;
-
- chunk = (void *)get_zeroed_page(GFP_KERNEL);
- if (!chunk)
- return ERR_PTR(-ENOMEM);
-
- if (WARN_ON(kho_scratch_overlap(virt_to_phys(chunk), PAGE_SIZE)))
- return ERR_PTR(-EINVAL);
-
- chunk->hdr.order = order;
- if (cur_chunk)
- KHOSER_STORE_PTR(cur_chunk->hdr.next, chunk);
- return no_free_ptr(chunk);
-}
-
-static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
-{
- struct khoser_mem_chunk *chunk = first_chunk;
-
- while (chunk) {
- struct khoser_mem_chunk *tmp = chunk;
-
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- kfree(tmp);
- }
-}
-
-static int kho_mem_serialize(struct kho_out *kho_out)
-{
- struct khoser_mem_chunk *first_chunk = NULL;
- struct khoser_mem_chunk *chunk = NULL;
- struct kho_mem_phys *physxa;
- unsigned long order;
- int err = -ENOMEM;
-
- xa_for_each(&kho_out->track.orders, order, physxa) {
- struct kho_mem_phys_bits *bits;
- unsigned long phys;
-
- chunk = new_chunk(chunk, order);
- if (IS_ERR(chunk)) {
- err = PTR_ERR(chunk);
- goto err_free;
- }
-
- if (!first_chunk)
- first_chunk = chunk;
-
- xa_for_each(&physxa->phys_bits, phys, bits) {
- struct khoser_mem_bitmap_ptr *elm;
-
- if (chunk->hdr.num_elms == ARRAY_SIZE(chunk->bitmaps)) {
- chunk = new_chunk(chunk, order);
- if (IS_ERR(chunk)) {
- err = PTR_ERR(chunk);
- goto err_free;
- }
- }
-
- elm = &chunk->bitmaps[chunk->hdr.num_elms];
- chunk->hdr.num_elms++;
- elm->phys_start = (phys * PRESERVE_BITS)
- << (order + PAGE_SHIFT);
- KHOSER_STORE_PTR(elm->bitmap, bits);
- }
- }
-
- kho_out->preserved_mem_map = first_chunk;
-
- return 0;
-
-err_free:
- kho_mem_ser_free(first_chunk);
- return err;
-}
-
-static void __init deserialize_bitmap(unsigned int order,
- struct khoser_mem_bitmap_ptr *elm)
-{
- struct kho_mem_phys_bits *bitmap = KHOSER_LOAD_PTR(elm->bitmap);
- unsigned long bit;
-
- for_each_set_bit(bit, bitmap->preserve, PRESERVE_BITS) {
- int sz = 1 << (order + PAGE_SHIFT);
- phys_addr_t phys =
- elm->phys_start + (bit << (order + PAGE_SHIFT));
- struct page *page = phys_to_page(phys);
- union kho_page_info info;
-
- memblock_reserve(phys, sz);
- memblock_reserved_mark_noinit(phys, sz);
- info.magic = KHO_PAGE_MAGIC;
- info.order = order;
- page->private = info.page_private;
- }
-}
-
-static void __init kho_mem_deserialize(const void *fdt)
-{
- struct khoser_mem_chunk *chunk;
- const phys_addr_t *mem;
- int len;
-
- mem = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
-
- if (!mem || len != sizeof(*mem)) {
- pr_err("failed to get preserved memory bitmaps\n");
- return;
- }
-
- chunk = *mem ? phys_to_virt(*mem) : NULL;
- while (chunk) {
- unsigned int i;
-
- for (i = 0; i != chunk->hdr.num_elms; i++)
- deserialize_bitmap(chunk->hdr.order,
- &chunk->bitmaps[i]);
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- }
-}
-
-/*
- * With KHO enabled, memory can become fragmented because KHO regions may
- * be anywhere in physical address space. The scratch regions give us a
- * safe zones that we will never see KHO allocations from. This is where we
- * can later safely load our new kexec images into and then use the scratch
- * area for early allocations that happen before page allocator is
- * initialized.
- */
-struct kho_scratch *kho_scratch;
-unsigned int kho_scratch_cnt;
-
-/*
- * The scratch areas are scaled by default as percent of memory allocated from
- * memblock. A user can override the scale with command line parameter:
- *
- * kho_scratch=N%
- *
- * It is also possible to explicitly define size for a lowmem, a global and
- * per-node scratch areas:
- *
- * kho_scratch=l[KMG],n[KMG],m[KMG]
- *
- * The explicit size definition takes precedence over scale definition.
- */
-static unsigned int scratch_scale __initdata = 200;
-static phys_addr_t scratch_size_global __initdata;
-static phys_addr_t scratch_size_pernode __initdata;
-static phys_addr_t scratch_size_lowmem __initdata;
-
-static int __init kho_parse_scratch_size(char *p)
-{
- size_t len;
- unsigned long sizes[3];
- size_t total_size = 0;
- int i;
-
- if (!p)
- return -EINVAL;
-
- len = strlen(p);
- if (!len)
- return -EINVAL;
-
- /* parse nn% */
- if (p[len - 1] == '%') {
- /* unsigned int max is 4,294,967,295, 10 chars */
- char s_scale[11] = {};
- int ret = 0;
-
- if (len > ARRAY_SIZE(s_scale))
- return -EINVAL;
-
- memcpy(s_scale, p, len - 1);
- ret = kstrtouint(s_scale, 10, &scratch_scale);
- if (!ret)
- pr_notice("scratch scale is %d%%\n", scratch_scale);
- return ret;
- }
-
- /* parse ll[KMG],mm[KMG],nn[KMG] */
- for (i = 0; i < ARRAY_SIZE(sizes); i++) {
- char *endp = p;
-
- if (i > 0) {
- if (*p != ',')
- return -EINVAL;
- p += 1;
- }
-
- sizes[i] = memparse(p, &endp);
- if (endp == p)
- return -EINVAL;
- p = endp;
- total_size += sizes[i];
- }
-
- if (!total_size)
- return -EINVAL;
-
- /* The string should be fully consumed by now. */
- if (*p)
- return -EINVAL;
-
- scratch_size_lowmem = sizes[0];
- scratch_size_global = sizes[1];
- scratch_size_pernode = sizes[2];
- scratch_scale = 0;
-
- pr_notice("scratch areas: lowmem: %lluMiB global: %lluMiB pernode: %lldMiB\n",
- (u64)(scratch_size_lowmem >> 20),
- (u64)(scratch_size_global >> 20),
- (u64)(scratch_size_pernode >> 20));
-
- return 0;
-}
-early_param("kho_scratch", kho_parse_scratch_size);
-
-static void __init scratch_size_update(void)
-{
- phys_addr_t size;
-
- if (!scratch_scale)
- return;
-
- size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
- NUMA_NO_NODE);
- size = size * scratch_scale / 100;
- scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-
- size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
- NUMA_NO_NODE);
- size = size * scratch_scale / 100 - scratch_size_lowmem;
- scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-}
-
-static phys_addr_t __init scratch_size_node(int nid)
-{
- phys_addr_t size;
-
- if (scratch_scale) {
- size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
- nid);
- size = size * scratch_scale / 100;
- } else {
- size = scratch_size_pernode;
- }
-
- return round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-}
-
-/**
- * kho_reserve_scratch - Reserve a contiguous chunk of memory for kexec
- *
- * With KHO we can preserve arbitrary pages in the system. To ensure we still
- * have a large contiguous region of memory when we search the physical address
- * space for target memory, let's make sure we always have a large CMA region
- * active. This CMA region will only be used for movable pages which are not a
- * problem for us during KHO because we can just move them somewhere else.
- */
-static void __init kho_reserve_scratch(void)
-{
- phys_addr_t addr, size;
- int nid, i = 0;
-
- if (!kho_enable)
- return;
-
- scratch_size_update();
-
- /* FIXME: deal with node hot-plug/remove */
- kho_scratch_cnt = num_online_nodes() + 2;
- size = kho_scratch_cnt * sizeof(*kho_scratch);
- kho_scratch = memblock_alloc(size, PAGE_SIZE);
- if (!kho_scratch)
- goto err_disable_kho;
-
- /*
- * reserve scratch area in low memory for lowmem allocations in the
- * next kernel
- */
- size = scratch_size_lowmem;
- addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0,
- ARCH_LOW_ADDRESS_LIMIT);
- if (!addr)
- goto err_free_scratch_desc;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
-
- /* reserve large contiguous area for allocations without nid */
- size = scratch_size_global;
- addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES);
- if (!addr)
- goto err_free_scratch_areas;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
-
- for_each_online_node(nid) {
- size = scratch_size_node(nid);
- addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
- 0, MEMBLOCK_ALLOC_ACCESSIBLE,
- nid, true);
- if (!addr)
- goto err_free_scratch_areas;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
- }
-
- return;
-
-err_free_scratch_areas:
- for (i--; i >= 0; i--)
- memblock_phys_free(kho_scratch[i].addr, kho_scratch[i].size);
-err_free_scratch_desc:
- memblock_free(kho_scratch, kho_scratch_cnt * sizeof(*kho_scratch));
-err_disable_kho:
- pr_warn("Failed to reserve scratch area, disabling kexec handover\n");
- kho_enable = false;
-}
-
-/**
- * kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
- * @name: name of the sub tree.
- * @fdt: the sub tree blob.
- *
- * Creates a new child node named @name in KHO root FDT and records
- * the physical address of @fdt. The pages of @fdt must also be preserved
- * by KHO for the new kernel to retrieve it after kexec.
- *
- * A debugfs blob entry is also created at
- * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured with
- * CONFIG_KEXEC_HANDOVER_DEBUGFS
- *
- * Return: 0 on success, error code on failure
- */
-int kho_add_subtree(const char *name, void *fdt)
-{
- struct kho_sub_fdt *sub_fdt;
-
- sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL);
- if (!sub_fdt)
- return -ENOMEM;
-
- INIT_LIST_HEAD(&sub_fdt->l);
- sub_fdt->name = name;
- sub_fdt->fdt = fdt;
-
- guard(mutex)(&kho_out.fdts_lock);
- list_add_tail(&sub_fdt->l, &kho_out.sub_fdts);
- WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false));
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_add_subtree);
-
-void kho_remove_subtree(void *fdt)
-{
- struct kho_sub_fdt *sub_fdt;
-
- guard(mutex)(&kho_out.fdts_lock);
- list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) {
- if (sub_fdt->fdt == fdt) {
- list_del(&sub_fdt->l);
- kfree(sub_fdt);
- kho_debugfs_fdt_remove(&kho_out.dbg, fdt);
- break;
- }
- }
-}
-EXPORT_SYMBOL_GPL(kho_remove_subtree);
-
-/**
- * kho_preserve_folio - preserve a folio across kexec.
- * @folio: folio to preserve.
- *
- * Instructs KHO to preserve the whole folio across kexec. The order
- * will be preserved as well.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_folio(struct folio *folio)
-{
- const unsigned long pfn = folio_pfn(folio);
- const unsigned int order = folio_order(folio);
- struct kho_mem_track *track = &kho_out.track;
-
- if (WARN_ON(kho_scratch_overlap(pfn << PAGE_SHIFT, PAGE_SIZE << order)))
- return -EINVAL;
-
- return __kho_preserve_order(track, pfn, order);
-}
-EXPORT_SYMBOL_GPL(kho_preserve_folio);
-
-/**
- * kho_unpreserve_folio - unpreserve a folio.
- * @folio: folio to unpreserve.
- *
- * Instructs KHO to unpreserve a folio that was preserved by
- * kho_preserve_folio() before. The provided @folio (pfn and order)
- * must exactly match a previously preserved folio.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_unpreserve_folio(struct folio *folio)
-{
- const unsigned long pfn = folio_pfn(folio);
- const unsigned int order = folio_order(folio);
- struct kho_mem_track *track = &kho_out.track;
-
- if (kho_out.finalized)
- return -EBUSY;
-
- __kho_unpreserve_order(track, pfn, order);
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
-
-/**
- * kho_preserve_pages - preserve contiguous pages across kexec
- * @page: first page in the list.
- * @nr_pages: number of pages.
- *
- * Preserve a contiguous list of order 0 pages. Must be restored using
- * kho_restore_pages() to ensure the pages are restored properly as order 0.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_pages(struct page *page, unsigned int nr_pages)
-{
- struct kho_mem_track *track = &kho_out.track;
- const unsigned long start_pfn = page_to_pfn(page);
- const unsigned long end_pfn = start_pfn + nr_pages;
- unsigned long pfn = start_pfn;
- unsigned long failed_pfn = 0;
- int err = 0;
-
- if (WARN_ON(kho_scratch_overlap(start_pfn << PAGE_SHIFT,
- nr_pages << PAGE_SHIFT))) {
- return -EINVAL;
- }
-
- while (pfn < end_pfn) {
- const unsigned int order =
- min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
- err = __kho_preserve_order(track, pfn, order);
- if (err) {
- failed_pfn = pfn;
- break;
- }
-
- pfn += 1 << order;
- }
-
- if (err)
- __kho_unpreserve(track, start_pfn, failed_pfn);
-
- return err;
-}
-EXPORT_SYMBOL_GPL(kho_preserve_pages);
-
-/**
- * kho_unpreserve_pages - unpreserve contiguous pages.
- * @page: first page in the list.
- * @nr_pages: number of pages.
- *
- * Instructs KHO to unpreserve @nr_pages contiguous pages starting from @page.
- * This must be called with the same @page and @nr_pages as the corresponding
- * kho_preserve_pages() call. Unpreserving arbitrary sub-ranges of larger
- * preserved blocks is not supported.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
-{
- struct kho_mem_track *track = &kho_out.track;
- const unsigned long start_pfn = page_to_pfn(page);
- const unsigned long end_pfn = start_pfn + nr_pages;
-
- if (kho_out.finalized)
- return -EBUSY;
-
- __kho_unpreserve(track, start_pfn, end_pfn);
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_unpreserve_pages);
-
-struct kho_vmalloc_hdr {
- DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *);
-};
-
-#define KHO_VMALLOC_SIZE \
- ((PAGE_SIZE - sizeof(struct kho_vmalloc_hdr)) / \
- sizeof(phys_addr_t))
-
-struct kho_vmalloc_chunk {
- struct kho_vmalloc_hdr hdr;
- phys_addr_t phys[KHO_VMALLOC_SIZE];
-};
-
-static_assert(sizeof(struct kho_vmalloc_chunk) == PAGE_SIZE);
-
-/* vmalloc flags KHO supports */
-#define KHO_VMALLOC_SUPPORTED_FLAGS (VM_ALLOC | VM_ALLOW_HUGE_VMAP)
-
-/* KHO internal flags for vmalloc preservations */
-#define KHO_VMALLOC_ALLOC 0x0001
-#define KHO_VMALLOC_HUGE_VMAP 0x0002
-
-static unsigned short vmalloc_flags_to_kho(unsigned int vm_flags)
-{
- unsigned short kho_flags = 0;
-
- if (vm_flags & VM_ALLOC)
- kho_flags |= KHO_VMALLOC_ALLOC;
- if (vm_flags & VM_ALLOW_HUGE_VMAP)
- kho_flags |= KHO_VMALLOC_HUGE_VMAP;
-
- return kho_flags;
-}
-
-static unsigned int kho_flags_to_vmalloc(unsigned short kho_flags)
-{
- unsigned int vm_flags = 0;
-
- if (kho_flags & KHO_VMALLOC_ALLOC)
- vm_flags |= VM_ALLOC;
- if (kho_flags & KHO_VMALLOC_HUGE_VMAP)
- vm_flags |= VM_ALLOW_HUGE_VMAP;
-
- return vm_flags;
-}
-
-static struct kho_vmalloc_chunk *new_vmalloc_chunk(struct kho_vmalloc_chunk *cur)
-{
- struct kho_vmalloc_chunk *chunk;
- int err;
-
- chunk = (struct kho_vmalloc_chunk *)get_zeroed_page(GFP_KERNEL);
- if (!chunk)
- return NULL;
-
- err = kho_preserve_pages(virt_to_page(chunk), 1);
- if (err)
- goto err_free;
- if (cur)
- KHOSER_STORE_PTR(cur->hdr.next, chunk);
- return chunk;
-
-err_free:
- free_page((unsigned long)chunk);
- return NULL;
-}
-
-static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk)
-{
- struct kho_mem_track *track = &kho_out.track;
- unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
-
- __kho_unpreserve(track, pfn, pfn + 1);
-
- for (int i = 0; chunk->phys[i]; i++) {
- pfn = PHYS_PFN(chunk->phys[i]);
- __kho_unpreserve(track, pfn, pfn + 1);
- }
-}
-
-static void kho_vmalloc_free_chunks(struct kho_vmalloc *kho_vmalloc)
-{
- struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(kho_vmalloc->first);
-
- while (chunk) {
- struct kho_vmalloc_chunk *tmp = chunk;
-
- kho_vmalloc_unpreserve_chunk(chunk);
-
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- free_page((unsigned long)tmp);
- }
-}
-
-/**
- * kho_preserve_vmalloc - preserve memory allocated with vmalloc() across kexec
- * @ptr: pointer to the area in vmalloc address space
- * @preservation: placeholder for preservation metadata
- *
- * Instructs KHO to preserve the area in vmalloc address space at @ptr. The
- * physical pages mapped at @ptr will be preserved and on successful return
- * @preservation will hold the physical address of a structure that describes
- * the preservation.
- *
- * NOTE: The memory allocated with vmalloc_node() variants cannot be reliably
- * restored on the same node
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
-{
- struct kho_vmalloc_chunk *chunk;
- struct vm_struct *vm = find_vm_area(ptr);
- unsigned int order, flags, nr_contig_pages;
- unsigned int idx = 0;
- int err;
-
- if (!vm)
- return -EINVAL;
-
- if (vm->flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
- return -EOPNOTSUPP;
-
- flags = vmalloc_flags_to_kho(vm->flags);
- order = get_vm_area_page_order(vm);
-
- chunk = new_vmalloc_chunk(NULL);
- if (!chunk)
- return -ENOMEM;
- KHOSER_STORE_PTR(preservation->first, chunk);
-
- nr_contig_pages = (1 << order);
- for (int i = 0; i < vm->nr_pages; i += nr_contig_pages) {
- phys_addr_t phys = page_to_phys(vm->pages[i]);
-
- err = kho_preserve_pages(vm->pages[i], nr_contig_pages);
- if (err)
- goto err_free;
-
- chunk->phys[idx++] = phys;
- if (idx == ARRAY_SIZE(chunk->phys)) {
- chunk = new_vmalloc_chunk(chunk);
- if (!chunk)
- goto err_free;
- idx = 0;
- }
- }
-
- preservation->total_pages = vm->nr_pages;
- preservation->flags = flags;
- preservation->order = order;
-
- return 0;
-
-err_free:
- kho_vmalloc_free_chunks(preservation);
- return err;
-}
-EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
-
-/**
- * kho_restore_vmalloc - recreates and populates an area in vmalloc address
- * space from the preserved memory.
- * @preservation: preservation metadata.
- *
- * Recreates an area in vmalloc address space and populates it with memory that
- * was preserved using kho_preserve_vmalloc().
- *
- * Return: pointer to the area in the vmalloc address space, NULL on failure.
- */
-void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
-{
- struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(preservation->first);
- unsigned int align, order, shift, vm_flags;
- unsigned long total_pages, contig_pages;
- unsigned long addr, size;
- struct vm_struct *area;
- struct page **pages;
- unsigned int idx = 0;
- int err;
-
- vm_flags = kho_flags_to_vmalloc(preservation->flags);
- if (vm_flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
- return NULL;
-
- total_pages = preservation->total_pages;
- pages = kvmalloc_array(total_pages, sizeof(*pages), GFP_KERNEL);
- if (!pages)
- return NULL;
- order = preservation->order;
- contig_pages = (1 << order);
- shift = PAGE_SHIFT + order;
- align = 1 << shift;
-
- while (chunk) {
- struct page *page;
-
- for (int i = 0; chunk->phys[i]; i++) {
- phys_addr_t phys = chunk->phys[i];
-
- if (idx + contig_pages > total_pages)
- goto err_free_pages_array;
-
- page = kho_restore_pages(phys, contig_pages);
- if (!page)
- goto err_free_pages_array;
-
- for (int j = 0; j < contig_pages; j++)
- pages[idx++] = page;
-
- phys += contig_pages * PAGE_SIZE;
- }
-
- page = kho_restore_pages(virt_to_phys(chunk), 1);
- if (!page)
- goto err_free_pages_array;
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- __free_page(page);
- }
-
- if (idx != total_pages)
- goto err_free_pages_array;
-
- area = __get_vm_area_node(total_pages * PAGE_SIZE, align, shift,
- vm_flags, VMALLOC_START, VMALLOC_END,
- NUMA_NO_NODE, GFP_KERNEL,
- __builtin_return_address(0));
- if (!area)
- goto err_free_pages_array;
-
- addr = (unsigned long)area->addr;
- size = get_vm_area_size(area);
- err = vmap_pages_range(addr, addr + size, PAGE_KERNEL, pages, shift);
- if (err)
- goto err_free_vm_area;
-
- area->nr_pages = total_pages;
- area->pages = pages;
-
- return area->addr;
-
-err_free_vm_area:
- free_vm_area(area);
-err_free_pages_array:
- kvfree(pages);
- return NULL;
-}
-EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
-
-static int __kho_abort(void)
-{
- if (kho_out.preserved_mem_map) {
- kho_mem_ser_free(kho_out.preserved_mem_map);
- kho_out.preserved_mem_map = NULL;
- }
-
- return 0;
-}
-
-int kho_abort(void)
-{
- int ret = 0;
-
- if (!kho_enable)
- return -EOPNOTSUPP;
-
- guard(mutex)(&kho_out.lock);
- if (!kho_out.finalized)
- return -ENOENT;
-
- ret = __kho_abort();
- if (ret)
- return ret;
-
- kho_out.finalized = false;
-
- kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt);
-
- return 0;
-}
-
-static int __kho_finalize(void)
-{
- int err = 0;
- u64 *preserved_mem_map;
- void *root = kho_out.fdt;
- struct kho_sub_fdt *fdt;
-
- err |= fdt_create(root, PAGE_SIZE);
- err |= fdt_finish_reservemap(root);
- err |= fdt_begin_node(root, "");
- err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
- /**
- * Reserve the preserved-memory-map property in the root FDT, so
- * that all property definitions will precede subnodes created by
- * KHO callers.
- */
- err |= fdt_property_placeholder(root, PROP_PRESERVED_MEMORY_MAP,
- sizeof(*preserved_mem_map),
- (void **)&preserved_mem_map);
- if (err)
- goto abort;
-
- err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
- if (err)
- goto abort;
-
- err = kho_mem_serialize(&kho_out);
- if (err)
- goto abort;
-
- *preserved_mem_map = (u64)virt_to_phys(kho_out.preserved_mem_map);
-
- mutex_lock(&kho_out.fdts_lock);
- list_for_each_entry(fdt, &kho_out.sub_fdts, l) {
- phys_addr_t phys = virt_to_phys(fdt->fdt);
-
- err |= fdt_begin_node(root, fdt->name);
- err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
- err |= fdt_end_node(root);
- }
- mutex_unlock(&kho_out.fdts_lock);
-
- err |= fdt_end_node(root);
- err |= fdt_finish(root);
-
-abort:
- if (err) {
- pr_err("Failed to convert KHO state tree: %d\n", err);
- __kho_abort();
- }
-
- return err;
-}
-
-int kho_finalize(void)
-{
- int ret;
-
- if (!kho_enable)
- return -EOPNOTSUPP;
-
- guard(mutex)(&kho_out.lock);
- if (kho_out.finalized)
- return -EEXIST;
-
- ret = __kho_finalize();
- if (ret)
- return ret;
-
- kho_out.finalized = true;
-
- WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
- kho_out.fdt, true));
-
- return 0;
-}
-
-bool kho_finalized(void)
-{
- guard(mutex)(&kho_out.lock);
- return kho_out.finalized;
-}
-
-struct kho_in {
- phys_addr_t fdt_phys;
- phys_addr_t scratch_phys;
- struct kho_debugfs dbg;
-};
-
-static struct kho_in kho_in = {
-};
-
-static const void *kho_get_fdt(void)
-{
- return kho_in.fdt_phys ? phys_to_virt(kho_in.fdt_phys) : NULL;
-}
-
-/**
- * is_kho_boot - check if current kernel was booted via KHO-enabled
- * kexec
- *
- * This function checks if the current kernel was loaded through a kexec
- * operation with KHO enabled, by verifying that a valid KHO FDT
- * was passed.
- *
- * Note: This function returns reliable results only after
- * kho_populate() has been called during early boot. Before that,
- * it may return false even if KHO data is present.
- *
- * Return: true if booted via KHO-enabled kexec, false otherwise
- */
-bool is_kho_boot(void)
-{
- return !!kho_get_fdt();
-}
-EXPORT_SYMBOL_GPL(is_kho_boot);
-
-/**
- * kho_retrieve_subtree - retrieve a preserved sub FDT by its name.
- * @name: the name of the sub FDT passed to kho_add_subtree().
- * @phys: if found, the physical address of the sub FDT is stored in @phys.
- *
- * Retrieve a preserved sub FDT named @name and store its physical
- * address in @phys.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
-{
- const void *fdt = kho_get_fdt();
- const u64 *val;
- int offset, len;
-
- if (!fdt)
- return -ENOENT;
-
- if (!phys)
- return -EINVAL;
-
- offset = fdt_subnode_offset(fdt, 0, name);
- if (offset < 0)
- return -ENOENT;
-
- val = fdt_getprop(fdt, offset, PROP_SUB_FDT, &len);
- if (!val || len != sizeof(*val))
- return -EINVAL;
-
- *phys = (phys_addr_t)*val;
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
-
-static __init int kho_init(void)
-{
- int err = 0;
- const void *fdt = kho_get_fdt();
- struct page *fdt_page;
-
- if (!kho_enable)
- return 0;
-
- fdt_page = alloc_page(GFP_KERNEL);
- if (!fdt_page) {
- err = -ENOMEM;
- goto err_free_scratch;
- }
- kho_out.fdt = page_to_virt(fdt_page);
-
- err = kho_debugfs_init();
- if (err)
- goto err_free_fdt;
-
- err = kho_out_debugfs_init(&kho_out.dbg);
- if (err)
- goto err_free_fdt;
-
- if (fdt) {
- kho_in_debugfs_init(&kho_in.dbg, fdt);
- return 0;
- }
-
- for (int i = 0; i < kho_scratch_cnt; i++) {
- unsigned long base_pfn = PHYS_PFN(kho_scratch[i].addr);
- unsigned long count = kho_scratch[i].size >> PAGE_SHIFT;
- unsigned long pfn;
-
- for (pfn = base_pfn; pfn < base_pfn + count;
- pfn += pageblock_nr_pages)
- init_cma_reserved_pageblock(pfn_to_page(pfn));
- }
-
- return 0;
-
-err_free_fdt:
- put_page(fdt_page);
- kho_out.fdt = NULL;
-err_free_scratch:
- for (int i = 0; i < kho_scratch_cnt; i++) {
- void *start = __va(kho_scratch[i].addr);
- void *end = start + kho_scratch[i].size;
-
- free_reserved_area(start, end, -1, "");
- }
- kho_enable = false;
- return err;
-}
-fs_initcall(kho_init);
-
-static void __init kho_release_scratch(void)
-{
- phys_addr_t start, end;
- u64 i;
-
- memmap_init_kho_scratch_pages();
-
- /*
- * Mark scratch mem as CMA before we return it. That way we
- * ensure that no kernel allocations happen on it. That means
- * we can reuse it as scratch memory again later.
- */
- __for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
- MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
- ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
- ulong end_pfn = pageblock_align(PFN_UP(end));
- ulong pfn;
-
- for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
- init_pageblock_migratetype(pfn_to_page(pfn),
- MIGRATE_CMA, false);
- }
-}
-
-void __init kho_memory_init(void)
-{
- struct folio *folio;
-
- if (kho_in.scratch_phys) {
- kho_scratch = phys_to_virt(kho_in.scratch_phys);
- kho_release_scratch();
-
- kho_mem_deserialize(kho_get_fdt());
- folio = kho_restore_folio(kho_in.fdt_phys);
- if (!folio)
- pr_warn("failed to restore folio for KHO fdt\n");
- } else {
- kho_reserve_scratch();
- }
-}
-
-void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
- phys_addr_t scratch_phys, u64 scratch_len)
-{
- void *fdt = NULL;
- struct kho_scratch *scratch = NULL;
- int err = 0;
- unsigned int scratch_cnt = scratch_len / sizeof(*kho_scratch);
-
- /* Validate the input FDT */
- fdt = early_memremap(fdt_phys, fdt_len);
- if (!fdt) {
- pr_warn("setup: failed to memremap FDT (0x%llx)\n", fdt_phys);
- err = -EFAULT;
- goto out;
- }
- err = fdt_check_header(fdt);
- if (err) {
- pr_warn("setup: handover FDT (0x%llx) is invalid: %d\n",
- fdt_phys, err);
- err = -EINVAL;
- goto out;
- }
- err = fdt_node_check_compatible(fdt, 0, KHO_FDT_COMPATIBLE);
- if (err) {
- pr_warn("setup: handover FDT (0x%llx) is incompatible with '%s': %d\n",
- fdt_phys, KHO_FDT_COMPATIBLE, err);
- err = -EINVAL;
- goto out;
- }
-
- scratch = early_memremap(scratch_phys, scratch_len);
- if (!scratch) {
- pr_warn("setup: failed to memremap scratch (phys=0x%llx, len=%lld)\n",
- scratch_phys, scratch_len);
- err = -EFAULT;
- goto out;
- }
-
- /*
- * We pass a safe contiguous blocks of memory to use for early boot
- * purporses from the previous kernel so that we can resize the
- * memblock array as needed.
- */
- for (int i = 0; i < scratch_cnt; i++) {
- struct kho_scratch *area = &scratch[i];
- u64 size = area->size;
-
- memblock_add(area->addr, size);
- err = memblock_mark_kho_scratch(area->addr, size);
- if (WARN_ON(err)) {
- pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %d",
- &area->addr, &size, err);
- goto out;
- }
- pr_debug("Marked 0x%pa+0x%pa as scratch", &area->addr, &size);
- }
-
- memblock_reserve(scratch_phys, scratch_len);
-
- /*
- * Now that we have a viable region of scratch memory, let's tell
- * the memblocks allocator to only use that for any allocations.
- * That way we ensure that nothing scribbles over in use data while
- * we initialize the page tables which we will need to ingest all
- * memory reservations from the previous kernel.
- */
- memblock_set_kho_scratch_only();
-
- kho_in.fdt_phys = fdt_phys;
- kho_in.scratch_phys = scratch_phys;
- kho_scratch_cnt = scratch_cnt;
- pr_info("found kexec handover data. Will skip init for some devices\n");
-
-out:
- if (fdt)
- early_memunmap(fdt, fdt_len);
- if (scratch)
- early_memunmap(scratch, scratch_len);
- if (err)
- pr_warn("disabling KHO revival: %d\n", err);
-}
-
-/* Helper functions for kexec_file_load */
-
-int kho_fill_kimage(struct kimage *image)
-{
- ssize_t scratch_size;
- int err = 0;
- struct kexec_buf scratch;
-
- if (!kho_out.finalized)
- return 0;
-
- image->kho.fdt = virt_to_phys(kho_out.fdt);
-
- scratch_size = sizeof(*kho_scratch) * kho_scratch_cnt;
- scratch = (struct kexec_buf){
- .image = image,
- .buffer = kho_scratch,
- .bufsz = scratch_size,
- .mem = KEXEC_BUF_MEM_UNKNOWN,
- .memsz = scratch_size,
- .buf_align = SZ_64K, /* Makes it easier to map */
- .buf_max = ULONG_MAX,
- .top_down = true,
- };
- err = kexec_add_buffer(&scratch);
- if (err)
- return err;
- image->kho.scratch = &image->segment[image->nr_segments - 1];
-
- return 0;
-}
-
-static int kho_walk_scratch(struct kexec_buf *kbuf,
- int (*func)(struct resource *, void *))
-{
- int ret = 0;
- int i;
-
- for (i = 0; i < kho_scratch_cnt; i++) {
- struct resource res = {
- .start = kho_scratch[i].addr,
- .end = kho_scratch[i].addr + kho_scratch[i].size - 1,
- };
-
- /* Try to fit the kimage into our KHO scratch region */
- ret = func(&res, kbuf);
- if (ret)
- break;
- }
-
- return ret;
-}
-
-int kho_locate_mem_hole(struct kexec_buf *kbuf,
- int (*func)(struct resource *, void *))
-{
- int ret;
-
- if (!kho_enable || kbuf->image->type == KEXEC_TYPE_CRASH)
- return 1;
-
- ret = kho_walk_scratch(kbuf, func);
-
- return ret == 1 ? 0 : -EADDRNOTAVAIL;
-}
diff --git a/kernel/kexec_handover_debug.c a/kernel/kexec_handover_debug.c
deleted file mode 100644
--- a/kernel/kexec_handover_debug.c
+++ /dev/null
@@ -1,25 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover_debug.c - kexec handover optional debug functionality
- * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include "kexec_handover_internal.h"
-
-bool kho_scratch_overlap(phys_addr_t phys, size_t size)
-{
- phys_addr_t scratch_start, scratch_end;
- unsigned int i;
-
- for (i = 0; i < kho_scratch_cnt; i++) {
- scratch_start = kho_scratch[i].addr;
- scratch_end = kho_scratch[i].addr + kho_scratch[i].size;
-
- if (phys < scratch_end && (phys + size) > scratch_start)
- return true;
- }
-
- return false;
-}
diff --git a/kernel/kexec_handover_debugfs.c a/kernel/kexec_handover_debugfs.c
deleted file mode 100644
--- a/kernel/kexec_handover_debugfs.c
+++ /dev/null
@@ -1,219 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover_debugfs.c - kexec handover debugfs interfaces
- * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
- * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
- * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
- * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include <linux/init.h>
-#include <linux/io.h>
-#include <linux/libfdt.h>
-#include <linux/mm.h>
-#include "kexec_handover_internal.h"
-
-static struct dentry *debugfs_root;
-
-struct fdt_debugfs {
- struct list_head list;
- struct debugfs_blob_wrapper wrapper;
- struct dentry *file;
-};
-
-static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
- const char *name, const void *fdt)
-{
- struct fdt_debugfs *f;
- struct dentry *file;
-
- f = kmalloc(sizeof(*f), GFP_KERNEL);
- if (!f)
- return -ENOMEM;
-
- f->wrapper.data = (void *)fdt;
- f->wrapper.size = fdt_totalsize(fdt);
-
- file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
- if (IS_ERR(file)) {
- kfree(f);
- return PTR_ERR(file);
- }
-
- f->file = file;
- list_add(&f->list, list);
-
- return 0;
-}
-
-int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root)
-{
- struct dentry *dir;
-
- if (root)
- dir = dbg->dir;
- else
- dir = dbg->sub_fdt_dir;
-
- return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
-}
-
-void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt)
-{
- struct fdt_debugfs *ff;
-
- list_for_each_entry(ff, &dbg->fdt_list, list) {
- if (ff->wrapper.data == fdt) {
- debugfs_remove(ff->file);
- list_del(&ff->list);
- kfree(ff);
- break;
- }
- }
-}
-
-static int kho_out_finalize_get(void *data, u64 *val)
-{
- *val = kho_finalized();
-
- return 0;
-}
-
-static int kho_out_finalize_set(void *data, u64 val)
-{
- if (val)
- return kho_finalize();
- else
- return kho_abort();
-}
-
-DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
- kho_out_finalize_set, "%llu\n");
-
-static int scratch_phys_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_phys);
-
-static int scratch_len_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].size);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_len);
-
-__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
-{
- struct dentry *dir, *sub_fdt_dir;
- int err, child;
-
- INIT_LIST_HEAD(&dbg->fdt_list);
-
- dir = debugfs_create_dir("in", debugfs_root);
- if (IS_ERR(dir)) {
- err = PTR_ERR(dir);
- goto err_out;
- }
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
- if (IS_ERR(sub_fdt_dir)) {
- err = PTR_ERR(sub_fdt_dir);
- goto err_rmdir;
- }
-
- err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt);
- if (err)
- goto err_rmdir;
-
- fdt_for_each_subnode(child, fdt, 0) {
- int len = 0;
- const char *name = fdt_get_name(fdt, child, NULL);
- const u64 *fdt_phys;
-
- fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
- if (!fdt_phys)
- continue;
- if (len != sizeof(*fdt_phys)) {
- pr_warn("node %s prop fdt has invalid length: %d\n",
- name, len);
- continue;
- }
- err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
- phys_to_virt(*fdt_phys));
- if (err) {
- pr_warn("failed to add fdt %s to debugfs: %d\n", name,
- err);
- continue;
- }
- }
-
- dbg->dir = dir;
- dbg->sub_fdt_dir = sub_fdt_dir;
-
- return;
-err_rmdir:
- debugfs_remove_recursive(dir);
-err_out:
- /*
- * Failure to create /sys/kernel/debug/kho/in does not prevent
- * reviving state from KHO and setting up KHO for the next
- * kexec.
- */
- if (err)
- pr_err("failed exposing handover FDT in debugfs: %d\n", err);
-}
-
-__init int kho_out_debugfs_init(struct kho_debugfs *dbg)
-{
- struct dentry *dir, *f, *sub_fdt_dir;
-
- INIT_LIST_HEAD(&dbg->fdt_list);
-
- dir = debugfs_create_dir("out", debugfs_root);
- if (IS_ERR(dir))
- return -ENOMEM;
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
- if (IS_ERR(sub_fdt_dir))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
- &scratch_phys_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_len", 0400, dir, NULL,
- &scratch_len_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("finalize", 0600, dir, NULL,
- &kho_out_finalize_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- dbg->dir = dir;
- dbg->sub_fdt_dir = sub_fdt_dir;
- return 0;
-
-err_rmdir:
- debugfs_remove_recursive(dir);
- return -ENOENT;
-}
-
-__init int kho_debugfs_init(void)
-{
- debugfs_root = debugfs_create_dir("kho", NULL);
- if (IS_ERR(debugfs_root))
- return -ENOENT;
- return 0;
-}
diff --git a/kernel/kexec_handover_internal.h a/kernel/kexec_handover_internal.h
deleted file mode 100644
--- a/kernel/kexec_handover_internal.h
+++ /dev/null
@@ -1,54 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
-#define LINUX_KEXEC_HANDOVER_INTERNAL_H
-
-#include <linux/kexec_handover.h>
-#include <linux/list.h>
-#include <linux/types.h>
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
-#include <linux/debugfs.h>
-
-struct kho_debugfs {
- struct dentry *dir;
- struct dentry *sub_fdt_dir;
- struct list_head fdt_list;
-};
-
-#else
-struct kho_debugfs {};
-#endif
-
-extern struct kho_scratch *kho_scratch;
-extern unsigned int kho_scratch_cnt;
-
-bool kho_finalized(void);
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
-int kho_debugfs_init(void);
-void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
-int kho_out_debugfs_init(struct kho_debugfs *dbg);
-int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root);
-void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt);
-#else
-static inline int kho_debugfs_init(void) { return 0; }
-static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
- const void *fdt) { }
-static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
-static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root) { return 0; }
-static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg,
- void *fdt) { }
-#endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
-bool kho_scratch_overlap(phys_addr_t phys, size_t size);
-#else
-static inline bool kho_scratch_overlap(phys_addr_t phys, size_t size)
-{
- return false;
-}
-#endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
-
-#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
diff --git a/kernel/liveupdate/Kconfig a/kernel/liveupdate/Kconfig
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/Kconfig
@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menu "Live Update and Kexec HandOver"
+
+config KEXEC_HANDOVER
+ bool "kexec handover"
+ depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
+ depends on !DEFERRED_STRUCT_PAGE_INIT
+ select MEMBLOCK_KHO_SCRATCH
+ select KEXEC_FILE
+ select DEBUG_FS
+ select LIBFDT
+ select CMA
+ help
+ Allow kexec to hand over state across kernels by generating and
+ passing additional metadata to the target kernel. This is useful
+ to keep data or state alive across the kexec. For this to work,
+ both source and target kernels need to have this option enabled.
+
+config KEXEC_HANDOVER_DEBUG
+ bool "Enable Kexec Handover debug checks"
+ depends on KEXEC_HANDOVER_DEBUGFS
+ help
+ This option enables extra sanity checks for the Kexec Handover
+ subsystem. Since, KHO performance is crucial in live update
+ scenarios and the extra code might be adding overhead it is
+ only optionally enabled.
+
+config KEXEC_HANDOVER_DEBUGFS
+ bool "kexec handover debugfs interface"
+ depends on KEXEC_HANDOVER
+ depends on DEBUG_FS
+ help
+ Allow to control kexec handover device tree via debugfs
+ interface, i.e. finalize the state or aborting the finalization.
+ Also, enables inspecting the KHO fdt trees with the debugfs binary
+ blobs.
+
+endmenu
diff --git a/kernel/liveupdate/kexec_handover.c a/kernel/liveupdate/kexec_handover.c
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover.c
@@ -0,0 +1,1527 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover.c - kexec handover metadata processing
+ * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
+ * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
+ * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include <linux/cleanup.h>
+#include <linux/cma.h>
+#include <linux/count_zeros.h>
+#include <linux/kexec.h>
+#include <linux/kexec_handover.h>
+#include <linux/libfdt.h>
+#include <linux/list.h>
+#include <linux/memblock.h>
+#include <linux/page-isolation.h>
+#include <linux/vmalloc.h>
+
+#include <asm/early_ioremap.h>
+
+#include "kexec_handover_internal.h"
+/*
+ * KHO is tightly coupled with mm init and needs access to some of mm
+ * internal APIs.
+ */
+#include "../../mm/internal.h"
+#include "../kexec_internal.h"
+#include "kexec_handover_internal.h"
+
+#define KHO_FDT_COMPATIBLE "kho-v1"
+#define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
+#define PROP_SUB_FDT "fdt"
+
+#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
+
+/*
+ * KHO uses page->private, which is an unsigned long, to store page metadata.
+ * Use it to store both the magic and the order.
+ */
+union kho_page_info {
+ unsigned long page_private;
+ struct {
+ unsigned int order;
+ unsigned int magic;
+ };
+};
+
+static_assert(sizeof(union kho_page_info) == sizeof(((struct page *)0)->private));
+
+static bool kho_enable __ro_after_init;
+
+bool kho_is_enabled(void)
+{
+ return kho_enable;
+}
+EXPORT_SYMBOL_GPL(kho_is_enabled);
+
+static int __init kho_parse_enable(char *p)
+{
+ return kstrtobool(p, &kho_enable);
+}
+early_param("kho", kho_parse_enable);
+
+/*
+ * Keep track of memory that is to be preserved across KHO.
+ *
+ * The serializing side uses two levels of xarrays to manage chunks of per-order
+ * PAGE_SIZE byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order
+ * of a 8TB system would fit inside a single 4096 byte bitmap. For order 0
+ * allocations each bitmap will cover 128M of address space. Thus, for 16G of
+ * memory at most 512K of bitmap memory will be needed for order 0.
+ *
+ * This approach is fully incremental, as the serialization progresses folios
+ * can continue be aggregated to the tracker. The final step, immediately prior
+ * to kexec would serialize the xarray information into a linked list for the
+ * successor kernel to parse.
+ */
+
+#define PRESERVE_BITS (PAGE_SIZE * 8)
+
+struct kho_mem_phys_bits {
+ DECLARE_BITMAP(preserve, PRESERVE_BITS);
+};
+
+static_assert(sizeof(struct kho_mem_phys_bits) == PAGE_SIZE);
+
+struct kho_mem_phys {
+ /*
+ * Points to kho_mem_phys_bits, a sparse bitmap array. Each bit is sized
+ * to order.
+ */
+ struct xarray phys_bits;
+};
+
+struct kho_mem_track {
+ /* Points to kho_mem_phys, each order gets its own bitmap tree */
+ struct xarray orders;
+};
+
+struct khoser_mem_chunk;
+
+struct kho_sub_fdt {
+ struct list_head l;
+ const char *name;
+ void *fdt;
+};
+
+struct kho_out {
+ void *fdt;
+ bool finalized;
+ struct mutex lock; /* protects KHO FDT finalization */
+
+ struct list_head sub_fdts;
+ struct mutex fdts_lock;
+
+ struct kho_mem_track track;
+ /* First chunk of serialized preserved memory map */
+ struct khoser_mem_chunk *preserved_mem_map;
+
+ struct kho_debugfs dbg;
+};
+
+static struct kho_out kho_out = {
+ .lock = __MUTEX_INITIALIZER(kho_out.lock),
+ .track = {
+ .orders = XARRAY_INIT(kho_out.track.orders, 0),
+ },
+ .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts),
+ .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock),
+ .finalized = false,
+};
+
+static void *xa_load_or_alloc(struct xarray *xa, unsigned long index)
+{
+ void *res = xa_load(xa, index);
+
+ if (res)
+ return res;
+
+ void *elm __free(free_page) = (void *)get_zeroed_page(GFP_KERNEL);
+
+ if (!elm)
+ return ERR_PTR(-ENOMEM);
+
+ if (WARN_ON(kho_scratch_overlap(virt_to_phys(elm), PAGE_SIZE)))
+ return ERR_PTR(-EINVAL);
+
+ res = xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
+ if (xa_is_err(res))
+ return ERR_PTR(xa_err(res));
+ else if (res)
+ return res;
+
+ return no_free_ptr(elm);
+}
+
+static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn,
+ unsigned int order)
+{
+ struct kho_mem_phys_bits *bits;
+ struct kho_mem_phys *physxa;
+ const unsigned long pfn_high = pfn >> order;
+
+ physxa = xa_load(&track->orders, order);
+ if (!physxa)
+ return;
+
+ bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
+ if (!bits)
+ return;
+
+ clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+}
+
+static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
+ unsigned long end_pfn)
+{
+ unsigned int order;
+
+ while (pfn < end_pfn) {
+ order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+
+ __kho_unpreserve_order(track, pfn, order);
+
+ pfn += 1 << order;
+ }
+}
+
+static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
+ unsigned int order)
+{
+ struct kho_mem_phys_bits *bits;
+ struct kho_mem_phys *physxa, *new_physxa;
+ const unsigned long pfn_high = pfn >> order;
+
+ might_sleep();
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ physxa = xa_load(&track->orders, order);
+ if (!physxa) {
+ int err;
+
+ new_physxa = kzalloc(sizeof(*physxa), GFP_KERNEL);
+ if (!new_physxa)
+ return -ENOMEM;
+
+ xa_init(&new_physxa->phys_bits);
+ physxa = xa_cmpxchg(&track->orders, order, NULL, new_physxa,
+ GFP_KERNEL);
+
+ err = xa_err(physxa);
+ if (err || physxa) {
+ xa_destroy(&new_physxa->phys_bits);
+ kfree(new_physxa);
+
+ if (err)
+ return err;
+ } else {
+ physxa = new_physxa;
+ }
+ }
+
+ bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
+ if (IS_ERR(bits))
+ return PTR_ERR(bits);
+
+ set_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+
+ return 0;
+}
+
+static struct page *kho_restore_page(phys_addr_t phys)
+{
+ struct page *page = pfn_to_online_page(PHYS_PFN(phys));
+ union kho_page_info info;
+ unsigned int nr_pages;
+
+ if (!page)
+ return NULL;
+
+ info.page_private = page->private;
+ /*
+ * deserialize_bitmap() only sets the magic on the head page. This magic
+ * check also implicitly makes sure phys is order-aligned since for
+ * non-order-aligned phys addresses, magic will never be set.
+ */
+ if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER))
+ return NULL;
+ nr_pages = (1 << info.order);
+
+ /* Clear private to make sure later restores on this page error out. */
+ page->private = 0;
+ /* Head page gets refcount of 1. */
+ set_page_count(page, 1);
+
+ /* For higher order folios, tail pages get a page count of zero. */
+ for (unsigned int i = 1; i < nr_pages; i++)
+ set_page_count(page + i, 0);
+
+ if (info.order > 0)
+ prep_compound_page(page, info.order);
+
+ adjust_managed_page_count(page, nr_pages);
+ return page;
+}
+
+/**
+ * kho_restore_folio - recreates the folio from the preserved memory.
+ * @phys: physical address of the folio.
+ *
+ * Return: pointer to the struct folio on success, NULL on failure.
+ */
+struct folio *kho_restore_folio(phys_addr_t phys)
+{
+ struct page *page = kho_restore_page(phys);
+
+ return page ? page_folio(page) : NULL;
+}
+EXPORT_SYMBOL_GPL(kho_restore_folio);
+
+/**
+ * kho_restore_pages - restore list of contiguous order 0 pages.
+ * @phys: physical address of the first page.
+ * @nr_pages: number of pages.
+ *
+ * Restore a contiguous list of order 0 pages that was preserved with
+ * kho_preserve_pages().
+ *
+ * Return: 0 on success, error code on failure
+ */
+struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages)
+{
+ const unsigned long start_pfn = PHYS_PFN(phys);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+ unsigned long pfn = start_pfn;
+
+ while (pfn < end_pfn) {
+ const unsigned int order =
+ min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+ struct page *page = kho_restore_page(PFN_PHYS(pfn));
+
+ if (!page)
+ return NULL;
+ split_page(page, order);
+ pfn += 1 << order;
+ }
+
+ return pfn_to_page(start_pfn);
+}
+EXPORT_SYMBOL_GPL(kho_restore_pages);
+
+/* Serialize and deserialize struct kho_mem_phys across kexec
+ *
+ * Record all the bitmaps in a linked list of pages for the next kernel to
+ * process. Each chunk holds bitmaps of the same order and each block of bitmaps
+ * starts at a given physical address. This allows the bitmaps to be sparse. The
+ * xarray is used to store them in a tree while building up the data structure,
+ * but the KHO successor kernel only needs to process them once in order.
+ *
+ * All of this memory is normal kmalloc() memory and is not marked for
+ * preservation. The successor kernel will remain isolated to the scratch space
+ * until it completes processing this list. Once processed all the memory
+ * storing these ranges will be marked as free.
+ */
+
+struct khoser_mem_bitmap_ptr {
+ phys_addr_t phys_start;
+ DECLARE_KHOSER_PTR(bitmap, struct kho_mem_phys_bits *);
+};
+
+struct khoser_mem_chunk_hdr {
+ DECLARE_KHOSER_PTR(next, struct khoser_mem_chunk *);
+ unsigned int order;
+ unsigned int num_elms;
+};
+
+#define KHOSER_BITMAP_SIZE \
+ ((PAGE_SIZE - sizeof(struct khoser_mem_chunk_hdr)) / \
+ sizeof(struct khoser_mem_bitmap_ptr))
+
+struct khoser_mem_chunk {
+ struct khoser_mem_chunk_hdr hdr;
+ struct khoser_mem_bitmap_ptr bitmaps[KHOSER_BITMAP_SIZE];
+};
+
+static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE);
+
+static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk,
+ unsigned long order)
+{
+ struct khoser_mem_chunk *chunk __free(free_page) = NULL;
+
+ chunk = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!chunk)
+ return ERR_PTR(-ENOMEM);
+
+ if (WARN_ON(kho_scratch_overlap(virt_to_phys(chunk), PAGE_SIZE)))
+ return ERR_PTR(-EINVAL);
+
+ chunk->hdr.order = order;
+ if (cur_chunk)
+ KHOSER_STORE_PTR(cur_chunk->hdr.next, chunk);
+ return no_free_ptr(chunk);
+}
+
+static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
+{
+ struct khoser_mem_chunk *chunk = first_chunk;
+
+ while (chunk) {
+ struct khoser_mem_chunk *tmp = chunk;
+
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ kfree(tmp);
+ }
+}
+
+static int kho_mem_serialize(struct kho_out *kho_out)
+{
+ struct khoser_mem_chunk *first_chunk = NULL;
+ struct khoser_mem_chunk *chunk = NULL;
+ struct kho_mem_phys *physxa;
+ unsigned long order;
+ int err = -ENOMEM;
+
+ xa_for_each(&kho_out->track.orders, order, physxa) {
+ struct kho_mem_phys_bits *bits;
+ unsigned long phys;
+
+ chunk = new_chunk(chunk, order);
+ if (IS_ERR(chunk)) {
+ err = PTR_ERR(chunk);
+ goto err_free;
+ }
+
+ if (!first_chunk)
+ first_chunk = chunk;
+
+ xa_for_each(&physxa->phys_bits, phys, bits) {
+ struct khoser_mem_bitmap_ptr *elm;
+
+ if (chunk->hdr.num_elms == ARRAY_SIZE(chunk->bitmaps)) {
+ chunk = new_chunk(chunk, order);
+ if (IS_ERR(chunk)) {
+ err = PTR_ERR(chunk);
+ goto err_free;
+ }
+ }
+
+ elm = &chunk->bitmaps[chunk->hdr.num_elms];
+ chunk->hdr.num_elms++;
+ elm->phys_start = (phys * PRESERVE_BITS)
+ << (order + PAGE_SHIFT);
+ KHOSER_STORE_PTR(elm->bitmap, bits);
+ }
+ }
+
+ kho_out->preserved_mem_map = first_chunk;
+
+ return 0;
+
+err_free:
+ kho_mem_ser_free(first_chunk);
+ return err;
+}
+
+static void __init deserialize_bitmap(unsigned int order,
+ struct khoser_mem_bitmap_ptr *elm)
+{
+ struct kho_mem_phys_bits *bitmap = KHOSER_LOAD_PTR(elm->bitmap);
+ unsigned long bit;
+
+ for_each_set_bit(bit, bitmap->preserve, PRESERVE_BITS) {
+ int sz = 1 << (order + PAGE_SHIFT);
+ phys_addr_t phys =
+ elm->phys_start + (bit << (order + PAGE_SHIFT));
+ struct page *page = phys_to_page(phys);
+ union kho_page_info info;
+
+ memblock_reserve(phys, sz);
+ memblock_reserved_mark_noinit(phys, sz);
+ info.magic = KHO_PAGE_MAGIC;
+ info.order = order;
+ page->private = info.page_private;
+ }
+}
+
+static void __init kho_mem_deserialize(const void *fdt)
+{
+ struct khoser_mem_chunk *chunk;
+ const phys_addr_t *mem;
+ int len;
+
+ mem = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
+
+ if (!mem || len != sizeof(*mem)) {
+ pr_err("failed to get preserved memory bitmaps\n");
+ return;
+ }
+
+ chunk = *mem ? phys_to_virt(*mem) : NULL;
+ while (chunk) {
+ unsigned int i;
+
+ for (i = 0; i != chunk->hdr.num_elms; i++)
+ deserialize_bitmap(chunk->hdr.order,
+ &chunk->bitmaps[i]);
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ }
+}
+
+/*
+ * With KHO enabled, memory can become fragmented because KHO regions may
+ * be anywhere in physical address space. The scratch regions give us a
+ * safe zones that we will never see KHO allocations from. This is where we
+ * can later safely load our new kexec images into and then use the scratch
+ * area for early allocations that happen before page allocator is
+ * initialized.
+ */
+struct kho_scratch *kho_scratch;
+unsigned int kho_scratch_cnt;
+
+/*
+ * The scratch areas are scaled by default as percent of memory allocated from
+ * memblock. A user can override the scale with command line parameter:
+ *
+ * kho_scratch=N%
+ *
+ * It is also possible to explicitly define size for a lowmem, a global and
+ * per-node scratch areas:
+ *
+ * kho_scratch=l[KMG],n[KMG],m[KMG]
+ *
+ * The explicit size definition takes precedence over scale definition.
+ */
+static unsigned int scratch_scale __initdata = 200;
+static phys_addr_t scratch_size_global __initdata;
+static phys_addr_t scratch_size_pernode __initdata;
+static phys_addr_t scratch_size_lowmem __initdata;
+
+static int __init kho_parse_scratch_size(char *p)
+{
+ size_t len;
+ unsigned long sizes[3];
+ size_t total_size = 0;
+ int i;
+
+ if (!p)
+ return -EINVAL;
+
+ len = strlen(p);
+ if (!len)
+ return -EINVAL;
+
+ /* parse nn% */
+ if (p[len - 1] == '%') {
+ /* unsigned int max is 4,294,967,295, 10 chars */
+ char s_scale[11] = {};
+ int ret = 0;
+
+ if (len > ARRAY_SIZE(s_scale))
+ return -EINVAL;
+
+ memcpy(s_scale, p, len - 1);
+ ret = kstrtouint(s_scale, 10, &scratch_scale);
+ if (!ret)
+ pr_notice("scratch scale is %d%%\n", scratch_scale);
+ return ret;
+ }
+
+ /* parse ll[KMG],mm[KMG],nn[KMG] */
+ for (i = 0; i < ARRAY_SIZE(sizes); i++) {
+ char *endp = p;
+
+ if (i > 0) {
+ if (*p != ',')
+ return -EINVAL;
+ p += 1;
+ }
+
+ sizes[i] = memparse(p, &endp);
+ if (endp == p)
+ return -EINVAL;
+ p = endp;
+ total_size += sizes[i];
+ }
+
+ if (!total_size)
+ return -EINVAL;
+
+ /* The string should be fully consumed by now. */
+ if (*p)
+ return -EINVAL;
+
+ scratch_size_lowmem = sizes[0];
+ scratch_size_global = sizes[1];
+ scratch_size_pernode = sizes[2];
+ scratch_scale = 0;
+
+ pr_notice("scratch areas: lowmem: %lluMiB global: %lluMiB pernode: %lldMiB\n",
+ (u64)(scratch_size_lowmem >> 20),
+ (u64)(scratch_size_global >> 20),
+ (u64)(scratch_size_pernode >> 20));
+
+ return 0;
+}
+early_param("kho_scratch", kho_parse_scratch_size);
+
+static void __init scratch_size_update(void)
+{
+ phys_addr_t size;
+
+ if (!scratch_scale)
+ return;
+
+ size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
+ NUMA_NO_NODE);
+ size = size * scratch_scale / 100;
+ scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+
+ size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+ NUMA_NO_NODE);
+ size = size * scratch_scale / 100 - scratch_size_lowmem;
+ scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+}
+
+static phys_addr_t __init scratch_size_node(int nid)
+{
+ phys_addr_t size;
+
+ if (scratch_scale) {
+ size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+ nid);
+ size = size * scratch_scale / 100;
+ } else {
+ size = scratch_size_pernode;
+ }
+
+ return round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+}
+
+/**
+ * kho_reserve_scratch - Reserve a contiguous chunk of memory for kexec
+ *
+ * With KHO we can preserve arbitrary pages in the system. To ensure we still
+ * have a large contiguous region of memory when we search the physical address
+ * space for target memory, let's make sure we always have a large CMA region
+ * active. This CMA region will only be used for movable pages which are not a
+ * problem for us during KHO because we can just move them somewhere else.
+ */
+static void __init kho_reserve_scratch(void)
+{
+ phys_addr_t addr, size;
+ int nid, i = 0;
+
+ if (!kho_enable)
+ return;
+
+ scratch_size_update();
+
+ /* FIXME: deal with node hot-plug/remove */
+ kho_scratch_cnt = num_online_nodes() + 2;
+ size = kho_scratch_cnt * sizeof(*kho_scratch);
+ kho_scratch = memblock_alloc(size, PAGE_SIZE);
+ if (!kho_scratch)
+ goto err_disable_kho;
+
+ /*
+ * reserve scratch area in low memory for lowmem allocations in the
+ * next kernel
+ */
+ size = scratch_size_lowmem;
+ addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0,
+ ARCH_LOW_ADDRESS_LIMIT);
+ if (!addr)
+ goto err_free_scratch_desc;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+
+ /* reserve large contiguous area for allocations without nid */
+ size = scratch_size_global;
+ addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES);
+ if (!addr)
+ goto err_free_scratch_areas;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+
+ for_each_online_node(nid) {
+ size = scratch_size_node(nid);
+ addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
+ 0, MEMBLOCK_ALLOC_ACCESSIBLE,
+ nid, true);
+ if (!addr)
+ goto err_free_scratch_areas;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+ }
+
+ return;
+
+err_free_scratch_areas:
+ for (i--; i >= 0; i--)
+ memblock_phys_free(kho_scratch[i].addr, kho_scratch[i].size);
+err_free_scratch_desc:
+ memblock_free(kho_scratch, kho_scratch_cnt * sizeof(*kho_scratch));
+err_disable_kho:
+ pr_warn("Failed to reserve scratch area, disabling kexec handover\n");
+ kho_enable = false;
+}
+
+/**
+ * kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
+ * @name: name of the sub tree.
+ * @fdt: the sub tree blob.
+ *
+ * Creates a new child node named @name in KHO root FDT and records
+ * the physical address of @fdt. The pages of @fdt must also be preserved
+ * by KHO for the new kernel to retrieve it after kexec.
+ *
+ * A debugfs blob entry is also created at
+ * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured with
+ * CONFIG_KEXEC_HANDOVER_DEBUGFS
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_add_subtree(const char *name, void *fdt)
+{
+ struct kho_sub_fdt *sub_fdt;
+
+ sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL);
+ if (!sub_fdt)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&sub_fdt->l);
+ sub_fdt->name = name;
+ sub_fdt->fdt = fdt;
+
+ guard(mutex)(&kho_out.fdts_lock);
+ list_add_tail(&sub_fdt->l, &kho_out.sub_fdts);
+ WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false));
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_add_subtree);
+
+void kho_remove_subtree(void *fdt)
+{
+ struct kho_sub_fdt *sub_fdt;
+
+ guard(mutex)(&kho_out.fdts_lock);
+ list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) {
+ if (sub_fdt->fdt == fdt) {
+ list_del(&sub_fdt->l);
+ kfree(sub_fdt);
+ kho_debugfs_fdt_remove(&kho_out.dbg, fdt);
+ break;
+ }
+ }
+}
+EXPORT_SYMBOL_GPL(kho_remove_subtree);
+
+/**
+ * kho_preserve_folio - preserve a folio across kexec.
+ * @folio: folio to preserve.
+ *
+ * Instructs KHO to preserve the whole folio across kexec. The order
+ * will be preserved as well.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_folio(struct folio *folio)
+{
+ const unsigned long pfn = folio_pfn(folio);
+ const unsigned int order = folio_order(folio);
+ struct kho_mem_track *track = &kho_out.track;
+
+ if (WARN_ON(kho_scratch_overlap(pfn << PAGE_SHIFT, PAGE_SIZE << order)))
+ return -EINVAL;
+
+ return __kho_preserve_order(track, pfn, order);
+}
+EXPORT_SYMBOL_GPL(kho_preserve_folio);
+
+/**
+ * kho_unpreserve_folio - unpreserve a folio.
+ * @folio: folio to unpreserve.
+ *
+ * Instructs KHO to unpreserve a folio that was preserved by
+ * kho_preserve_folio() before. The provided @folio (pfn and order)
+ * must exactly match a previously preserved folio.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_folio(struct folio *folio)
+{
+ const unsigned long pfn = folio_pfn(folio);
+ const unsigned int order = folio_order(folio);
+ struct kho_mem_track *track = &kho_out.track;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve_order(track, pfn, order);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
+
+/**
+ * kho_preserve_pages - preserve contiguous pages across kexec
+ * @page: first page in the list.
+ * @nr_pages: number of pages.
+ *
+ * Preserve a contiguous list of order 0 pages. Must be restored using
+ * kho_restore_pages() to ensure the pages are restored properly as order 0.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_pages(struct page *page, unsigned int nr_pages)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ const unsigned long start_pfn = page_to_pfn(page);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+ unsigned long pfn = start_pfn;
+ unsigned long failed_pfn = 0;
+ int err = 0;
+
+ if (WARN_ON(kho_scratch_overlap(start_pfn << PAGE_SHIFT,
+ nr_pages << PAGE_SHIFT))) {
+ return -EINVAL;
+ }
+
+ while (pfn < end_pfn) {
+ const unsigned int order =
+ min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+
+ err = __kho_preserve_order(track, pfn, order);
+ if (err) {
+ failed_pfn = pfn;
+ break;
+ }
+
+ pfn += 1 << order;
+ }
+
+ if (err)
+ __kho_unpreserve(track, start_pfn, failed_pfn);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(kho_preserve_pages);
+
+/**
+ * kho_unpreserve_pages - unpreserve contiguous pages.
+ * @page: first page in the list.
+ * @nr_pages: number of pages.
+ *
+ * Instructs KHO to unpreserve @nr_pages contiguous pages starting from @page.
+ * This must be called with the same @page and @nr_pages as the corresponding
+ * kho_preserve_pages() call. Unpreserving arbitrary sub-ranges of larger
+ * preserved blocks is not supported.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ const unsigned long start_pfn = page_to_pfn(page);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve(track, start_pfn, end_pfn);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_pages);
+
+struct kho_vmalloc_hdr {
+ DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *);
+};
+
+#define KHO_VMALLOC_SIZE \
+ ((PAGE_SIZE - sizeof(struct kho_vmalloc_hdr)) / \
+ sizeof(phys_addr_t))
+
+struct kho_vmalloc_chunk {
+ struct kho_vmalloc_hdr hdr;
+ phys_addr_t phys[KHO_VMALLOC_SIZE];
+};
+
+static_assert(sizeof(struct kho_vmalloc_chunk) == PAGE_SIZE);
+
+/* vmalloc flags KHO supports */
+#define KHO_VMALLOC_SUPPORTED_FLAGS (VM_ALLOC | VM_ALLOW_HUGE_VMAP)
+
+/* KHO internal flags for vmalloc preservations */
+#define KHO_VMALLOC_ALLOC 0x0001
+#define KHO_VMALLOC_HUGE_VMAP 0x0002
+
+static unsigned short vmalloc_flags_to_kho(unsigned int vm_flags)
+{
+ unsigned short kho_flags = 0;
+
+ if (vm_flags & VM_ALLOC)
+ kho_flags |= KHO_VMALLOC_ALLOC;
+ if (vm_flags & VM_ALLOW_HUGE_VMAP)
+ kho_flags |= KHO_VMALLOC_HUGE_VMAP;
+
+ return kho_flags;
+}
+
+static unsigned int kho_flags_to_vmalloc(unsigned short kho_flags)
+{
+ unsigned int vm_flags = 0;
+
+ if (kho_flags & KHO_VMALLOC_ALLOC)
+ vm_flags |= VM_ALLOC;
+ if (kho_flags & KHO_VMALLOC_HUGE_VMAP)
+ vm_flags |= VM_ALLOW_HUGE_VMAP;
+
+ return vm_flags;
+}
+
+static struct kho_vmalloc_chunk *new_vmalloc_chunk(struct kho_vmalloc_chunk *cur)
+{
+ struct kho_vmalloc_chunk *chunk;
+ int err;
+
+ chunk = (struct kho_vmalloc_chunk *)get_zeroed_page(GFP_KERNEL);
+ if (!chunk)
+ return NULL;
+
+ err = kho_preserve_pages(virt_to_page(chunk), 1);
+ if (err)
+ goto err_free;
+ if (cur)
+ KHOSER_STORE_PTR(cur->hdr.next, chunk);
+ return chunk;
+
+err_free:
+ free_page((unsigned long)chunk);
+ return NULL;
+}
+
+static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
+
+ __kho_unpreserve(track, pfn, pfn + 1);
+
+ for (int i = 0; chunk->phys[i]; i++) {
+ pfn = PHYS_PFN(chunk->phys[i]);
+ __kho_unpreserve(track, pfn, pfn + 1);
+ }
+}
+
+static void kho_vmalloc_free_chunks(struct kho_vmalloc *kho_vmalloc)
+{
+ struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(kho_vmalloc->first);
+
+ while (chunk) {
+ struct kho_vmalloc_chunk *tmp = chunk;
+
+ kho_vmalloc_unpreserve_chunk(chunk);
+
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ free_page((unsigned long)tmp);
+ }
+}
+
+/**
+ * kho_preserve_vmalloc - preserve memory allocated with vmalloc() across kexec
+ * @ptr: pointer to the area in vmalloc address space
+ * @preservation: placeholder for preservation metadata
+ *
+ * Instructs KHO to preserve the area in vmalloc address space at @ptr. The
+ * physical pages mapped at @ptr will be preserved and on successful return
+ * @preservation will hold the physical address of a structure that describes
+ * the preservation.
+ *
+ * NOTE: The memory allocated with vmalloc_node() variants cannot be reliably
+ * restored on the same node
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
+{
+ struct kho_vmalloc_chunk *chunk;
+ struct vm_struct *vm = find_vm_area(ptr);
+ unsigned int order, flags, nr_contig_pages;
+ unsigned int idx = 0;
+ int err;
+
+ if (!vm)
+ return -EINVAL;
+
+ if (vm->flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
+ return -EOPNOTSUPP;
+
+ flags = vmalloc_flags_to_kho(vm->flags);
+ order = get_vm_area_page_order(vm);
+
+ chunk = new_vmalloc_chunk(NULL);
+ if (!chunk)
+ return -ENOMEM;
+ KHOSER_STORE_PTR(preservation->first, chunk);
+
+ nr_contig_pages = (1 << order);
+ for (int i = 0; i < vm->nr_pages; i += nr_contig_pages) {
+ phys_addr_t phys = page_to_phys(vm->pages[i]);
+
+ err = kho_preserve_pages(vm->pages[i], nr_contig_pages);
+ if (err)
+ goto err_free;
+
+ chunk->phys[idx++] = phys;
+ if (idx == ARRAY_SIZE(chunk->phys)) {
+ chunk = new_vmalloc_chunk(chunk);
+ if (!chunk)
+ goto err_free;
+ idx = 0;
+ }
+ }
+
+ preservation->total_pages = vm->nr_pages;
+ preservation->flags = flags;
+ preservation->order = order;
+
+ return 0;
+
+err_free:
+ kho_vmalloc_free_chunks(preservation);
+ return err;
+}
+EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
+
+/**
+ * kho_restore_vmalloc - recreates and populates an area in vmalloc address
+ * space from the preserved memory.
+ * @preservation: preservation metadata.
+ *
+ * Recreates an area in vmalloc address space and populates it with memory that
+ * was preserved using kho_preserve_vmalloc().
+ *
+ * Return: pointer to the area in the vmalloc address space, NULL on failure.
+ */
+void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
+{
+ struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(preservation->first);
+ unsigned int align, order, shift, vm_flags;
+ unsigned long total_pages, contig_pages;
+ unsigned long addr, size;
+ struct vm_struct *area;
+ struct page **pages;
+ unsigned int idx = 0;
+ int err;
+
+ vm_flags = kho_flags_to_vmalloc(preservation->flags);
+ if (vm_flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
+ return NULL;
+
+ total_pages = preservation->total_pages;
+ pages = kvmalloc_array(total_pages, sizeof(*pages), GFP_KERNEL);
+ if (!pages)
+ return NULL;
+ order = preservation->order;
+ contig_pages = (1 << order);
+ shift = PAGE_SHIFT + order;
+ align = 1 << shift;
+
+ while (chunk) {
+ struct page *page;
+
+ for (int i = 0; chunk->phys[i]; i++) {
+ phys_addr_t phys = chunk->phys[i];
+
+ if (idx + contig_pages > total_pages)
+ goto err_free_pages_array;
+
+ page = kho_restore_pages(phys, contig_pages);
+ if (!page)
+ goto err_free_pages_array;
+
+ for (int j = 0; j < contig_pages; j++)
+ pages[idx++] = page;
+
+ phys += contig_pages * PAGE_SIZE;
+ }
+
+ page = kho_restore_pages(virt_to_phys(chunk), 1);
+ if (!page)
+ goto err_free_pages_array;
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ __free_page(page);
+ }
+
+ if (idx != total_pages)
+ goto err_free_pages_array;
+
+ area = __get_vm_area_node(total_pages * PAGE_SIZE, align, shift,
+ vm_flags, VMALLOC_START, VMALLOC_END,
+ NUMA_NO_NODE, GFP_KERNEL,
+ __builtin_return_address(0));
+ if (!area)
+ goto err_free_pages_array;
+
+ addr = (unsigned long)area->addr;
+ size = get_vm_area_size(area);
+ err = vmap_pages_range(addr, addr + size, PAGE_KERNEL, pages, shift);
+ if (err)
+ goto err_free_vm_area;
+
+ area->nr_pages = total_pages;
+ area->pages = pages;
+
+ return area->addr;
+
+err_free_vm_area:
+ free_vm_area(area);
+err_free_pages_array:
+ kvfree(pages);
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
+
+static int __kho_abort(void)
+{
+ if (kho_out.preserved_mem_map) {
+ kho_mem_ser_free(kho_out.preserved_mem_map);
+ kho_out.preserved_mem_map = NULL;
+ }
+
+ return 0;
+}
+
+int kho_abort(void)
+{
+ int ret = 0;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ guard(mutex)(&kho_out.lock);
+ if (!kho_out.finalized)
+ return -ENOENT;
+
+ ret = __kho_abort();
+ if (ret)
+ return ret;
+
+ kho_out.finalized = false;
+
+ kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt);
+
+ return 0;
+}
+
+static int __kho_finalize(void)
+{
+ int err = 0;
+ u64 *preserved_mem_map;
+ void *root = kho_out.fdt;
+ struct kho_sub_fdt *fdt;
+
+ err |= fdt_create(root, PAGE_SIZE);
+ err |= fdt_finish_reservemap(root);
+ err |= fdt_begin_node(root, "");
+ err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
+ /**
+ * Reserve the preserved-memory-map property in the root FDT, so
+ * that all property definitions will precede subnodes created by
+ * KHO callers.
+ */
+ err |= fdt_property_placeholder(root, PROP_PRESERVED_MEMORY_MAP,
+ sizeof(*preserved_mem_map),
+ (void **)&preserved_mem_map);
+ if (err)
+ goto abort;
+
+ err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
+ if (err)
+ goto abort;
+
+ err = kho_mem_serialize(&kho_out);
+ if (err)
+ goto abort;
+
+ *preserved_mem_map = (u64)virt_to_phys(kho_out.preserved_mem_map);
+
+ mutex_lock(&kho_out.fdts_lock);
+ list_for_each_entry(fdt, &kho_out.sub_fdts, l) {
+ phys_addr_t phys = virt_to_phys(fdt->fdt);
+
+ err |= fdt_begin_node(root, fdt->name);
+ err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
+ err |= fdt_end_node(root);
+ }
+ mutex_unlock(&kho_out.fdts_lock);
+
+ err |= fdt_end_node(root);
+ err |= fdt_finish(root);
+
+abort:
+ if (err) {
+ pr_err("Failed to convert KHO state tree: %d\n", err);
+ __kho_abort();
+ }
+
+ return err;
+}
+
+int kho_finalize(void)
+{
+ int ret;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ guard(mutex)(&kho_out.lock);
+ if (kho_out.finalized)
+ return -EEXIST;
+
+ ret = __kho_finalize();
+ if (ret)
+ return ret;
+
+ kho_out.finalized = true;
+
+ WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
+ kho_out.fdt, true));
+
+ return 0;
+}
+
+bool kho_finalized(void)
+{
+ guard(mutex)(&kho_out.lock);
+ return kho_out.finalized;
+}
+
+struct kho_in {
+ phys_addr_t fdt_phys;
+ phys_addr_t scratch_phys;
+ struct kho_debugfs dbg;
+};
+
+static struct kho_in kho_in = {
+};
+
+static const void *kho_get_fdt(void)
+{
+ return kho_in.fdt_phys ? phys_to_virt(kho_in.fdt_phys) : NULL;
+}
+
+/**
+ * is_kho_boot - check if current kernel was booted via KHO-enabled
+ * kexec
+ *
+ * This function checks if the current kernel was loaded through a kexec
+ * operation with KHO enabled, by verifying that a valid KHO FDT
+ * was passed.
+ *
+ * Note: This function returns reliable results only after
+ * kho_populate() has been called during early boot. Before that,
+ * it may return false even if KHO data is present.
+ *
+ * Return: true if booted via KHO-enabled kexec, false otherwise
+ */
+bool is_kho_boot(void)
+{
+ return !!kho_get_fdt();
+}
+EXPORT_SYMBOL_GPL(is_kho_boot);
+
+/**
+ * kho_retrieve_subtree - retrieve a preserved sub FDT by its name.
+ * @name: the name of the sub FDT passed to kho_add_subtree().
+ * @phys: if found, the physical address of the sub FDT is stored in @phys.
+ *
+ * Retrieve a preserved sub FDT named @name and store its physical
+ * address in @phys.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
+{
+ const void *fdt = kho_get_fdt();
+ const u64 *val;
+ int offset, len;
+
+ if (!fdt)
+ return -ENOENT;
+
+ if (!phys)
+ return -EINVAL;
+
+ offset = fdt_subnode_offset(fdt, 0, name);
+ if (offset < 0)
+ return -ENOENT;
+
+ val = fdt_getprop(fdt, offset, PROP_SUB_FDT, &len);
+ if (!val || len != sizeof(*val))
+ return -EINVAL;
+
+ *phys = (phys_addr_t)*val;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
+
+static __init int kho_init(void)
+{
+ int err = 0;
+ const void *fdt = kho_get_fdt();
+ struct page *fdt_page;
+
+ if (!kho_enable)
+ return 0;
+
+ fdt_page = alloc_page(GFP_KERNEL);
+ if (!fdt_page) {
+ err = -ENOMEM;
+ goto err_free_scratch;
+ }
+ kho_out.fdt = page_to_virt(fdt_page);
+
+ err = kho_debugfs_init();
+ if (err)
+ goto err_free_fdt;
+
+ err = kho_out_debugfs_init(&kho_out.dbg);
+ if (err)
+ goto err_free_fdt;
+
+ if (fdt) {
+ kho_in_debugfs_init(&kho_in.dbg, fdt);
+ return 0;
+ }
+
+ for (int i = 0; i < kho_scratch_cnt; i++) {
+ unsigned long base_pfn = PHYS_PFN(kho_scratch[i].addr);
+ unsigned long count = kho_scratch[i].size >> PAGE_SHIFT;
+ unsigned long pfn;
+
+ for (pfn = base_pfn; pfn < base_pfn + count;
+ pfn += pageblock_nr_pages)
+ init_cma_reserved_pageblock(pfn_to_page(pfn));
+ }
+
+ return 0;
+
+err_free_fdt:
+ put_page(fdt_page);
+ kho_out.fdt = NULL;
+err_free_scratch:
+ for (int i = 0; i < kho_scratch_cnt; i++) {
+ void *start = __va(kho_scratch[i].addr);
+ void *end = start + kho_scratch[i].size;
+
+ free_reserved_area(start, end, -1, "");
+ }
+ kho_enable = false;
+ return err;
+}
+fs_initcall(kho_init);
+
+static void __init kho_release_scratch(void)
+{
+ phys_addr_t start, end;
+ u64 i;
+
+ memmap_init_kho_scratch_pages();
+
+ /*
+ * Mark scratch mem as CMA before we return it. That way we
+ * ensure that no kernel allocations happen on it. That means
+ * we can reuse it as scratch memory again later.
+ */
+ __for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
+ MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
+ ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
+ ulong end_pfn = pageblock_align(PFN_UP(end));
+ ulong pfn;
+
+ for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
+ init_pageblock_migratetype(pfn_to_page(pfn),
+ MIGRATE_CMA, false);
+ }
+}
+
+void __init kho_memory_init(void)
+{
+ struct folio *folio;
+
+ if (kho_in.scratch_phys) {
+ kho_scratch = phys_to_virt(kho_in.scratch_phys);
+ kho_release_scratch();
+
+ kho_mem_deserialize(kho_get_fdt());
+ folio = kho_restore_folio(kho_in.fdt_phys);
+ if (!folio)
+ pr_warn("failed to restore folio for KHO fdt\n");
+ } else {
+ kho_reserve_scratch();
+ }
+}
+
+void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
+ phys_addr_t scratch_phys, u64 scratch_len)
+{
+ void *fdt = NULL;
+ struct kho_scratch *scratch = NULL;
+ int err = 0;
+ unsigned int scratch_cnt = scratch_len / sizeof(*kho_scratch);
+
+ /* Validate the input FDT */
+ fdt = early_memremap(fdt_phys, fdt_len);
+ if (!fdt) {
+ pr_warn("setup: failed to memremap FDT (0x%llx)\n", fdt_phys);
+ err = -EFAULT;
+ goto out;
+ }
+ err = fdt_check_header(fdt);
+ if (err) {
+ pr_warn("setup: handover FDT (0x%llx) is invalid: %d\n",
+ fdt_phys, err);
+ err = -EINVAL;
+ goto out;
+ }
+ err = fdt_node_check_compatible(fdt, 0, KHO_FDT_COMPATIBLE);
+ if (err) {
+ pr_warn("setup: handover FDT (0x%llx) is incompatible with '%s': %d\n",
+ fdt_phys, KHO_FDT_COMPATIBLE, err);
+ err = -EINVAL;
+ goto out;
+ }
+
+ scratch = early_memremap(scratch_phys, scratch_len);
+ if (!scratch) {
+ pr_warn("setup: failed to memremap scratch (phys=0x%llx, len=%lld)\n",
+ scratch_phys, scratch_len);
+ err = -EFAULT;
+ goto out;
+ }
+
+ /*
+ * We pass a safe contiguous blocks of memory to use for early boot
+ * purporses from the previous kernel so that we can resize the
+ * memblock array as needed.
+ */
+ for (int i = 0; i < scratch_cnt; i++) {
+ struct kho_scratch *area = &scratch[i];
+ u64 size = area->size;
+
+ memblock_add(area->addr, size);
+ err = memblock_mark_kho_scratch(area->addr, size);
+ if (WARN_ON(err)) {
+ pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %d",
+ &area->addr, &size, err);
+ goto out;
+ }
+ pr_debug("Marked 0x%pa+0x%pa as scratch", &area->addr, &size);
+ }
+
+ memblock_reserve(scratch_phys, scratch_len);
+
+ /*
+ * Now that we have a viable region of scratch memory, let's tell
+ * the memblocks allocator to only use that for any allocations.
+ * That way we ensure that nothing scribbles over in use data while
+ * we initialize the page tables which we will need to ingest all
+ * memory reservations from the previous kernel.
+ */
+ memblock_set_kho_scratch_only();
+
+ kho_in.fdt_phys = fdt_phys;
+ kho_in.scratch_phys = scratch_phys;
+ kho_scratch_cnt = scratch_cnt;
+ pr_info("found kexec handover data. Will skip init for some devices\n");
+
+out:
+ if (fdt)
+ early_memunmap(fdt, fdt_len);
+ if (scratch)
+ early_memunmap(scratch, scratch_len);
+ if (err)
+ pr_warn("disabling KHO revival: %d\n", err);
+}
+
+/* Helper functions for kexec_file_load */
+
+int kho_fill_kimage(struct kimage *image)
+{
+ ssize_t scratch_size;
+ int err = 0;
+ struct kexec_buf scratch;
+
+ if (!kho_out.finalized)
+ return 0;
+
+ image->kho.fdt = virt_to_phys(kho_out.fdt);
+
+ scratch_size = sizeof(*kho_scratch) * kho_scratch_cnt;
+ scratch = (struct kexec_buf){
+ .image = image,
+ .buffer = kho_scratch,
+ .bufsz = scratch_size,
+ .mem = KEXEC_BUF_MEM_UNKNOWN,
+ .memsz = scratch_size,
+ .buf_align = SZ_64K, /* Makes it easier to map */
+ .buf_max = ULONG_MAX,
+ .top_down = true,
+ };
+ err = kexec_add_buffer(&scratch);
+ if (err)
+ return err;
+ image->kho.scratch = &image->segment[image->nr_segments - 1];
+
+ return 0;
+}
+
+static int kho_walk_scratch(struct kexec_buf *kbuf,
+ int (*func)(struct resource *, void *))
+{
+ int ret = 0;
+ int i;
+
+ for (i = 0; i < kho_scratch_cnt; i++) {
+ struct resource res = {
+ .start = kho_scratch[i].addr,
+ .end = kho_scratch[i].addr + kho_scratch[i].size - 1,
+ };
+
+ /* Try to fit the kimage into our KHO scratch region */
+ ret = func(&res, kbuf);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+int kho_locate_mem_hole(struct kexec_buf *kbuf,
+ int (*func)(struct resource *, void *))
+{
+ int ret;
+
+ if (!kho_enable || kbuf->image->type == KEXEC_TYPE_CRASH)
+ return 1;
+
+ ret = kho_walk_scratch(kbuf, func);
+
+ return ret == 1 ? 0 : -EADDRNOTAVAIL;
+}
diff --git a/kernel/liveupdate/kexec_handover_debug.c a/kernel/liveupdate/kexec_handover_debug.c
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_debug.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover_debug.c - kexec handover optional debug functionality
+ * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include "kexec_handover_internal.h"
+
+bool kho_scratch_overlap(phys_addr_t phys, size_t size)
+{
+ phys_addr_t scratch_start, scratch_end;
+ unsigned int i;
+
+ for (i = 0; i < kho_scratch_cnt; i++) {
+ scratch_start = kho_scratch[i].addr;
+ scratch_end = kho_scratch[i].addr + kho_scratch[i].size;
+
+ if (phys < scratch_end && (phys + size) > scratch_start)
+ return true;
+ }
+
+ return false;
+}
diff --git a/kernel/liveupdate/kexec_handover_debugfs.c a/kernel/liveupdate/kexec_handover_debugfs.c
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_debugfs.c
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover_debugfs.c - kexec handover debugfs interfaces
+ * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
+ * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
+ * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/libfdt.h>
+#include <linux/mm.h>
+#include "kexec_handover_internal.h"
+
+static struct dentry *debugfs_root;
+
+struct fdt_debugfs {
+ struct list_head list;
+ struct debugfs_blob_wrapper wrapper;
+ struct dentry *file;
+};
+
+static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
+ const char *name, const void *fdt)
+{
+ struct fdt_debugfs *f;
+ struct dentry *file;
+
+ f = kmalloc(sizeof(*f), GFP_KERNEL);
+ if (!f)
+ return -ENOMEM;
+
+ f->wrapper.data = (void *)fdt;
+ f->wrapper.size = fdt_totalsize(fdt);
+
+ file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
+ if (IS_ERR(file)) {
+ kfree(f);
+ return PTR_ERR(file);
+ }
+
+ f->file = file;
+ list_add(&f->list, list);
+
+ return 0;
+}
+
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root)
+{
+ struct dentry *dir;
+
+ if (root)
+ dir = dbg->dir;
+ else
+ dir = dbg->sub_fdt_dir;
+
+ return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
+}
+
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt)
+{
+ struct fdt_debugfs *ff;
+
+ list_for_each_entry(ff, &dbg->fdt_list, list) {
+ if (ff->wrapper.data == fdt) {
+ debugfs_remove(ff->file);
+ list_del(&ff->list);
+ kfree(ff);
+ break;
+ }
+ }
+}
+
+static int kho_out_finalize_get(void *data, u64 *val)
+{
+ *val = kho_finalized();
+
+ return 0;
+}
+
+static int kho_out_finalize_set(void *data, u64 val)
+{
+ if (val)
+ return kho_finalize();
+ else
+ return kho_abort();
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
+ kho_out_finalize_set, "%llu\n");
+
+static int scratch_phys_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_phys);
+
+static int scratch_len_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].size);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_len);
+
+__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
+{
+ struct dentry *dir, *sub_fdt_dir;
+ int err, child;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("in", debugfs_root);
+ if (IS_ERR(dir)) {
+ err = PTR_ERR(dir);
+ goto err_out;
+ }
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir)) {
+ err = PTR_ERR(sub_fdt_dir);
+ goto err_rmdir;
+ }
+
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt);
+ if (err)
+ goto err_rmdir;
+
+ fdt_for_each_subnode(child, fdt, 0) {
+ int len = 0;
+ const char *name = fdt_get_name(fdt, child, NULL);
+ const u64 *fdt_phys;
+
+ fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
+ if (!fdt_phys)
+ continue;
+ if (len != sizeof(*fdt_phys)) {
+ pr_warn("node %s prop fdt has invalid length: %d\n",
+ name, len);
+ continue;
+ }
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
+ phys_to_virt(*fdt_phys));
+ if (err) {
+ pr_warn("failed to add fdt %s to debugfs: %d\n", name,
+ err);
+ continue;
+ }
+ }
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+
+ return;
+err_rmdir:
+ debugfs_remove_recursive(dir);
+err_out:
+ /*
+ * Failure to create /sys/kernel/debug/kho/in does not prevent
+ * reviving state from KHO and setting up KHO for the next
+ * kexec.
+ */
+ if (err)
+ pr_err("failed exposing handover FDT in debugfs: %d\n", err);
+}
+
+__init int kho_out_debugfs_init(struct kho_debugfs *dbg)
+{
+ struct dentry *dir, *f, *sub_fdt_dir;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("out", debugfs_root);
+ if (IS_ERR(dir))
+ return -ENOMEM;
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
+ &scratch_phys_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_len", 0400, dir, NULL,
+ &scratch_len_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("finalize", 0600, dir, NULL,
+ &kho_out_finalize_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+ return 0;
+
+err_rmdir:
+ debugfs_remove_recursive(dir);
+ return -ENOENT;
+}
+
+__init int kho_debugfs_init(void)
+{
+ debugfs_root = debugfs_create_dir("kho", NULL);
+ if (IS_ERR(debugfs_root))
+ return -ENOENT;
+ return 0;
+}
diff --git a/kernel/liveupdate/kexec_handover_internal.h a/kernel/liveupdate/kexec_handover_internal.h
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_internal.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
+#define LINUX_KEXEC_HANDOVER_INTERNAL_H
+
+#include <linux/kexec_handover.h>
+#include <linux/list.h>
+#include <linux/types.h>
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
+#include <linux/debugfs.h>
+
+struct kho_debugfs {
+ struct dentry *dir;
+ struct dentry *sub_fdt_dir;
+ struct list_head fdt_list;
+};
+
+#else
+struct kho_debugfs {};
+#endif
+
+extern struct kho_scratch *kho_scratch;
+extern unsigned int kho_scratch_cnt;
+
+bool kho_finalized(void);
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
+int kho_debugfs_init(void);
+void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
+int kho_out_debugfs_init(struct kho_debugfs *dbg);
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root);
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt);
+#else
+static inline int kho_debugfs_init(void) { return 0; }
+static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
+ const void *fdt) { }
+static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
+static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root) { return 0; }
+static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg,
+ void *fdt) { }
+#endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
+bool kho_scratch_overlap(phys_addr_t phys, size_t size);
+#else
+static inline bool kho_scratch_overlap(phys_addr_t phys, size_t size)
+{
+ return false;
+}
+#endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
+
+#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
diff --git a/kernel/liveupdate/Makefile a/kernel/liveupdate/Makefile
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS) += kexec_handover_debugfs.o
--- a/kernel/Makefile~liveupdate-kho-move-to-kernel-liveupdate
+++ a/kernel/Makefile
@@ -52,6 +52,7 @@ obj-y += printk/
obj-y += irq/
obj-y += rcu/
obj-y += livepatch/
+obj-y += liveupdate/
obj-y += dma/
obj-y += entry/
obj-y += unwind/
@@ -82,9 +83,6 @@ obj-$(CONFIG_CRASH_DUMP_KUNIT_TEST) += c
obj-$(CONFIG_KEXEC) += kexec.o
obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
-obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
-obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
-obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS) += kexec_handover_debugfs.o
obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup/
--- a/MAINTAINERS~liveupdate-kho-move-to-kernel-liveupdate
+++ a/MAINTAINERS
@@ -13781,7 +13781,7 @@ S: Maintained
F: Documentation/admin-guide/mm/kho.rst
F: Documentation/core-api/kho/*
F: include/linux/kexec_handover.h
-F: kernel/kexec_handover*
+F: kernel/liveupdate/kexec_handover*
F: tools/testing/selftests/kho/
KEYS-ENCRYPTED
_
Patches currently in -mm which might be from pasha.tatashin@soleen.com are
liveupdate-kho-warn-and-fail-on-metadata-or-preserved-memory-in-scratch-area.patch
liveupdate-kho-increase-metadata-bitmap-size-to-page_size.patch
liveupdate-kho-allocate-metadata-directly-from-the-buddy-allocator.patch
kho-allow-to-drive-kho-from-within-kernel.patch
kho-make-debugfs-interface-optional.patch
kho-add-interfaces-to-unpreserve-folios-and-page-ranges.patch
kho-dont-unpreserve-memory-during-abort.patch
liveupdate-kho-move-to-kernel-liveupdate.patch
liveupdate-kho-move-kho-debugfs-directory-to-liveupdate.patch
memblock-unpreserve-memory-in-case-of-error.patch
^ permalink raw reply [flat|nested] 3+ messages in thread
* + liveupdate-kho-move-to-kernel-liveupdate.patch added to mm-nonmm-unstable branch
@ 2025-11-04 3:26 Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2025-11-04 3:26 UTC (permalink / raw)
To: mm-commits, yanjun.zhu, tj, rppt, rdunlap, pratyush, ojeda,
masahiroy, jgg, jgg, horms, graf, corbet, changyuanl, brauner,
pasha.tatashin, akpm
The patch titled
Subject: liveupdate: kho: move to kernel/liveupdate
has been added to the -mm mm-nonmm-unstable branch. Its filename is
liveupdate-kho-move-to-kernel-liveupdate.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/liveupdate-kho-move-to-kernel-liveupdate.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Pasha Tatashin <pasha.tatashin@soleen.com>
Subject: liveupdate: kho: move to kernel/liveupdate
Date: Sat, 1 Nov 2025 10:23:23 -0400
Move KHO to kernel/liveupdate/ in preparation of placing all Live Update
core kernel related files to the same place.
Link: https://lkml.kernel.org/r/20251101142325.1326536-8-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Simon Horman <horms@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zhu Yanjun <yanjun.zhu@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
Documentation/core-api/kho/concepts.rst | 2
MAINTAINERS | 2
init/Kconfig | 2
kernel/Kconfig.kexec | 34
kernel/Makefile | 4
kernel/kexec_handover.c | 1548 ------------------
kernel/kexec_handover_debug.c | 25
kernel/kexec_handover_debugfs.c | 219 --
kernel/kexec_handover_internal.h | 56
kernel/liveupdate/Kconfig | 39
kernel/liveupdate/Makefile | 5
kernel/liveupdate/kexec_handover.c | 1548 ++++++++++++++++++
kernel/liveupdate/kexec_handover_debug.c | 25
kernel/liveupdate/kexec_handover_debugfs.c | 219 ++
kernel/liveupdate/kexec_handover_internal.h | 56
15 files changed, 1897 insertions(+), 1887 deletions(-)
--- a/Documentation/core-api/kho/concepts.rst~liveupdate-kho-move-to-kernel-liveupdate
+++ a/Documentation/core-api/kho/concepts.rst
@@ -70,5 +70,5 @@ in the FDT. That state is called the KHO
Public API
==========
-.. kernel-doc:: kernel/kexec_handover.c
+.. kernel-doc:: kernel/liveupdate/kexec_handover.c
:export:
--- a/init/Kconfig~liveupdate-kho-move-to-kernel-liveupdate
+++ a/init/Kconfig
@@ -2156,6 +2156,8 @@ config TRACEPOINTS
source "kernel/Kconfig.kexec"
+source "kernel/liveupdate/Kconfig"
+
endmenu # General setup
source "arch/Kconfig"
--- a/kernel/Kconfig.kexec~liveupdate-kho-move-to-kernel-liveupdate
+++ a/kernel/Kconfig.kexec
@@ -94,40 +94,6 @@ config KEXEC_JUMP
Jump between original kernel and kexeced kernel and invoke
code in physical address mode via KEXEC
-config KEXEC_HANDOVER
- bool "kexec handover"
- depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
- depends on !DEFERRED_STRUCT_PAGE_INIT
- select MEMBLOCK_KHO_SCRATCH
- select KEXEC_FILE
- select LIBFDT
- select CMA
- help
- Allow kexec to hand over state across kernels by generating and
- passing additional metadata to the target kernel. This is useful
- to keep data or state alive across the kexec. For this to work,
- both source and target kernels need to have this option enabled.
-
-config KEXEC_HANDOVER_DEBUG
- bool "Enable Kexec Handover debug checks"
- depends on KEXEC_HANDOVER
- help
- This option enables extra sanity checks for the Kexec Handover
- subsystem. Since, KHO performance is crucial in live update
- scenarios and the extra code might be adding overhead it is
- only optionally enabled.
-
-config KEXEC_HANDOVER_DEBUGFS
- bool "kexec handover debugfs interface"
- default KEXEC_HANDOVER
- depends on KEXEC_HANDOVER
- select DEBUG_FS
- help
- Allow to control kexec handover device tree via debugfs
- interface, i.e. finalize the state or aborting the finalization.
- Also, enables inspecting the KHO fdt trees with the debugfs binary
- blobs.
-
config CRASH_DUMP
bool "kernel crash dumps"
default ARCH_DEFAULT_CRASH_DUMP
diff --git a/kernel/kexec_handover.c a/kernel/kexec_handover.c
deleted file mode 100644
--- a/kernel/kexec_handover.c
+++ /dev/null
@@ -1,1548 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover.c - kexec handover metadata processing
- * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
- * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
- * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include <linux/cleanup.h>
-#include <linux/cma.h>
-#include <linux/count_zeros.h>
-#include <linux/kexec.h>
-#include <linux/kexec_handover.h>
-#include <linux/libfdt.h>
-#include <linux/list.h>
-#include <linux/memblock.h>
-#include <linux/page-isolation.h>
-#include <linux/vmalloc.h>
-
-#include <asm/early_ioremap.h>
-
-#include "kexec_handover_internal.h"
-/*
- * KHO is tightly coupled with mm init and needs access to some of mm
- * internal APIs.
- */
-#include "../mm/internal.h"
-#include "kexec_internal.h"
-#include "kexec_handover_internal.h"
-
-#define KHO_FDT_COMPATIBLE "kho-v1"
-#define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
-#define PROP_SUB_FDT "fdt"
-
-#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
-
-/*
- * KHO uses page->private, which is an unsigned long, to store page metadata.
- * Use it to store both the magic and the order.
- */
-union kho_page_info {
- unsigned long page_private;
- struct {
- unsigned int order;
- unsigned int magic;
- };
-};
-
-static_assert(sizeof(union kho_page_info) == sizeof(((struct page *)0)->private));
-
-static bool kho_enable __ro_after_init;
-
-bool kho_is_enabled(void)
-{
- return kho_enable;
-}
-EXPORT_SYMBOL_GPL(kho_is_enabled);
-
-static int __init kho_parse_enable(char *p)
-{
- return kstrtobool(p, &kho_enable);
-}
-early_param("kho", kho_parse_enable);
-
-/*
- * Keep track of memory that is to be preserved across KHO.
- *
- * The serializing side uses two levels of xarrays to manage chunks of per-order
- * PAGE_SIZE byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order
- * of a 8TB system would fit inside a single 4096 byte bitmap. For order 0
- * allocations each bitmap will cover 128M of address space. Thus, for 16G of
- * memory at most 512K of bitmap memory will be needed for order 0.
- *
- * This approach is fully incremental, as the serialization progresses folios
- * can continue be aggregated to the tracker. The final step, immediately prior
- * to kexec would serialize the xarray information into a linked list for the
- * successor kernel to parse.
- */
-
-#define PRESERVE_BITS (PAGE_SIZE * 8)
-
-struct kho_mem_phys_bits {
- DECLARE_BITMAP(preserve, PRESERVE_BITS);
-};
-
-static_assert(sizeof(struct kho_mem_phys_bits) == PAGE_SIZE);
-
-struct kho_mem_phys {
- /*
- * Points to kho_mem_phys_bits, a sparse bitmap array. Each bit is sized
- * to order.
- */
- struct xarray phys_bits;
-};
-
-struct kho_mem_track {
- /* Points to kho_mem_phys, each order gets its own bitmap tree */
- struct xarray orders;
-};
-
-struct khoser_mem_chunk;
-
-struct kho_sub_fdt {
- struct list_head l;
- const char *name;
- void *fdt;
-};
-
-struct kho_out {
- void *fdt;
- bool finalized;
- struct mutex lock; /* protects KHO FDT finalization */
-
- struct list_head sub_fdts;
- struct mutex fdts_lock;
-
- struct kho_mem_track track;
- /* First chunk of serialized preserved memory map */
- struct khoser_mem_chunk *preserved_mem_map;
-
- struct kho_debugfs dbg;
-};
-
-static struct kho_out kho_out = {
- .lock = __MUTEX_INITIALIZER(kho_out.lock),
- .track = {
- .orders = XARRAY_INIT(kho_out.track.orders, 0),
- },
- .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts),
- .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock),
- .finalized = false,
-};
-
-static void *xa_load_or_alloc(struct xarray *xa, unsigned long index)
-{
- void *res = xa_load(xa, index);
-
- if (res)
- return res;
-
- void *elm __free(free_page) = (void *)get_zeroed_page(GFP_KERNEL);
-
- if (!elm)
- return ERR_PTR(-ENOMEM);
-
- if (WARN_ON(kho_scratch_overlap(virt_to_phys(elm), PAGE_SIZE)))
- return ERR_PTR(-EINVAL);
-
- res = xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
- if (xa_is_err(res))
- return ERR_PTR(xa_err(res));
- else if (res)
- return res;
-
- return no_free_ptr(elm);
-}
-
-static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn,
- unsigned int order)
-{
- struct kho_mem_phys_bits *bits;
- struct kho_mem_phys *physxa;
- const unsigned long pfn_high = pfn >> order;
-
- physxa = xa_load(&track->orders, order);
- if (WARN_ON_ONCE(!physxa))
- return;
-
- bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
- if (WARN_ON_ONCE(!bits))
- return;
-
- clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
-}
-
-static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
- unsigned long end_pfn)
-{
- unsigned int order;
-
- while (pfn < end_pfn) {
- order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
- __kho_unpreserve_order(track, pfn, order);
-
- pfn += 1 << order;
- }
-}
-
-static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
- unsigned int order)
-{
- struct kho_mem_phys_bits *bits;
- struct kho_mem_phys *physxa, *new_physxa;
- const unsigned long pfn_high = pfn >> order;
-
- might_sleep();
-
- if (kho_out.finalized)
- return -EBUSY;
-
- physxa = xa_load(&track->orders, order);
- if (!physxa) {
- int err;
-
- new_physxa = kzalloc(sizeof(*physxa), GFP_KERNEL);
- if (!new_physxa)
- return -ENOMEM;
-
- xa_init(&new_physxa->phys_bits);
- physxa = xa_cmpxchg(&track->orders, order, NULL, new_physxa,
- GFP_KERNEL);
-
- err = xa_err(physxa);
- if (err || physxa) {
- xa_destroy(&new_physxa->phys_bits);
- kfree(new_physxa);
-
- if (err)
- return err;
- } else {
- physxa = new_physxa;
- }
- }
-
- bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
- if (IS_ERR(bits))
- return PTR_ERR(bits);
-
- set_bit(pfn_high % PRESERVE_BITS, bits->preserve);
-
- return 0;
-}
-
-static struct page *kho_restore_page(phys_addr_t phys)
-{
- struct page *page = pfn_to_online_page(PHYS_PFN(phys));
- union kho_page_info info;
- unsigned int nr_pages;
-
- if (!page)
- return NULL;
-
- info.page_private = page->private;
- /*
- * deserialize_bitmap() only sets the magic on the head page. This magic
- * check also implicitly makes sure phys is order-aligned since for
- * non-order-aligned phys addresses, magic will never be set.
- */
- if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER))
- return NULL;
- nr_pages = (1 << info.order);
-
- /* Clear private to make sure later restores on this page error out. */
- page->private = 0;
- /* Head page gets refcount of 1. */
- set_page_count(page, 1);
-
- /* For higher order folios, tail pages get a page count of zero. */
- for (unsigned int i = 1; i < nr_pages; i++)
- set_page_count(page + i, 0);
-
- if (info.order > 0)
- prep_compound_page(page, info.order);
-
- adjust_managed_page_count(page, nr_pages);
- return page;
-}
-
-/**
- * kho_restore_folio - recreates the folio from the preserved memory.
- * @phys: physical address of the folio.
- *
- * Return: pointer to the struct folio on success, NULL on failure.
- */
-struct folio *kho_restore_folio(phys_addr_t phys)
-{
- struct page *page = kho_restore_page(phys);
-
- return page ? page_folio(page) : NULL;
-}
-EXPORT_SYMBOL_GPL(kho_restore_folio);
-
-/**
- * kho_restore_pages - restore list of contiguous order 0 pages.
- * @phys: physical address of the first page.
- * @nr_pages: number of pages.
- *
- * Restore a contiguous list of order 0 pages that was preserved with
- * kho_preserve_pages().
- *
- * Return: 0 on success, error code on failure
- */
-struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages)
-{
- const unsigned long start_pfn = PHYS_PFN(phys);
- const unsigned long end_pfn = start_pfn + nr_pages;
- unsigned long pfn = start_pfn;
-
- while (pfn < end_pfn) {
- const unsigned int order =
- min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
- struct page *page = kho_restore_page(PFN_PHYS(pfn));
-
- if (!page)
- return NULL;
- split_page(page, order);
- pfn += 1 << order;
- }
-
- return pfn_to_page(start_pfn);
-}
-EXPORT_SYMBOL_GPL(kho_restore_pages);
-
-/* Serialize and deserialize struct kho_mem_phys across kexec
- *
- * Record all the bitmaps in a linked list of pages for the next kernel to
- * process. Each chunk holds bitmaps of the same order and each block of bitmaps
- * starts at a given physical address. This allows the bitmaps to be sparse. The
- * xarray is used to store them in a tree while building up the data structure,
- * but the KHO successor kernel only needs to process them once in order.
- *
- * All of this memory is normal kmalloc() memory and is not marked for
- * preservation. The successor kernel will remain isolated to the scratch space
- * until it completes processing this list. Once processed all the memory
- * storing these ranges will be marked as free.
- */
-
-struct khoser_mem_bitmap_ptr {
- phys_addr_t phys_start;
- DECLARE_KHOSER_PTR(bitmap, struct kho_mem_phys_bits *);
-};
-
-struct khoser_mem_chunk_hdr {
- DECLARE_KHOSER_PTR(next, struct khoser_mem_chunk *);
- unsigned int order;
- unsigned int num_elms;
-};
-
-#define KHOSER_BITMAP_SIZE \
- ((PAGE_SIZE - sizeof(struct khoser_mem_chunk_hdr)) / \
- sizeof(struct khoser_mem_bitmap_ptr))
-
-struct khoser_mem_chunk {
- struct khoser_mem_chunk_hdr hdr;
- struct khoser_mem_bitmap_ptr bitmaps[KHOSER_BITMAP_SIZE];
-};
-
-static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE);
-
-static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk,
- unsigned long order)
-{
- struct khoser_mem_chunk *chunk __free(free_page) = NULL;
-
- chunk = (void *)get_zeroed_page(GFP_KERNEL);
- if (!chunk)
- return ERR_PTR(-ENOMEM);
-
- if (WARN_ON(kho_scratch_overlap(virt_to_phys(chunk), PAGE_SIZE)))
- return ERR_PTR(-EINVAL);
-
- chunk->hdr.order = order;
- if (cur_chunk)
- KHOSER_STORE_PTR(cur_chunk->hdr.next, chunk);
- return no_free_ptr(chunk);
-}
-
-static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
-{
- struct khoser_mem_chunk *chunk = first_chunk;
-
- while (chunk) {
- struct khoser_mem_chunk *tmp = chunk;
-
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- kfree(tmp);
- }
-}
-
-static int kho_mem_serialize(struct kho_out *kho_out)
-{
- struct khoser_mem_chunk *first_chunk = NULL;
- struct khoser_mem_chunk *chunk = NULL;
- struct kho_mem_phys *physxa;
- unsigned long order;
- int err = -ENOMEM;
-
- xa_for_each(&kho_out->track.orders, order, physxa) {
- struct kho_mem_phys_bits *bits;
- unsigned long phys;
-
- chunk = new_chunk(chunk, order);
- if (IS_ERR(chunk)) {
- err = PTR_ERR(chunk);
- goto err_free;
- }
-
- if (!first_chunk)
- first_chunk = chunk;
-
- xa_for_each(&physxa->phys_bits, phys, bits) {
- struct khoser_mem_bitmap_ptr *elm;
-
- if (chunk->hdr.num_elms == ARRAY_SIZE(chunk->bitmaps)) {
- chunk = new_chunk(chunk, order);
- if (IS_ERR(chunk)) {
- err = PTR_ERR(chunk);
- goto err_free;
- }
- }
-
- elm = &chunk->bitmaps[chunk->hdr.num_elms];
- chunk->hdr.num_elms++;
- elm->phys_start = (phys * PRESERVE_BITS)
- << (order + PAGE_SHIFT);
- KHOSER_STORE_PTR(elm->bitmap, bits);
- }
- }
-
- kho_out->preserved_mem_map = first_chunk;
-
- return 0;
-
-err_free:
- kho_mem_ser_free(first_chunk);
- return err;
-}
-
-static void __init deserialize_bitmap(unsigned int order,
- struct khoser_mem_bitmap_ptr *elm)
-{
- struct kho_mem_phys_bits *bitmap = KHOSER_LOAD_PTR(elm->bitmap);
- unsigned long bit;
-
- for_each_set_bit(bit, bitmap->preserve, PRESERVE_BITS) {
- int sz = 1 << (order + PAGE_SHIFT);
- phys_addr_t phys =
- elm->phys_start + (bit << (order + PAGE_SHIFT));
- struct page *page = phys_to_page(phys);
- union kho_page_info info;
-
- memblock_reserve(phys, sz);
- memblock_reserved_mark_noinit(phys, sz);
- info.magic = KHO_PAGE_MAGIC;
- info.order = order;
- page->private = info.page_private;
- }
-}
-
-static void __init kho_mem_deserialize(const void *fdt)
-{
- struct khoser_mem_chunk *chunk;
- const phys_addr_t *mem;
- int len;
-
- mem = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
-
- if (!mem || len != sizeof(*mem)) {
- pr_err("failed to get preserved memory bitmaps\n");
- return;
- }
-
- chunk = *mem ? phys_to_virt(*mem) : NULL;
- while (chunk) {
- unsigned int i;
-
- for (i = 0; i != chunk->hdr.num_elms; i++)
- deserialize_bitmap(chunk->hdr.order,
- &chunk->bitmaps[i]);
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- }
-}
-
-/*
- * With KHO enabled, memory can become fragmented because KHO regions may
- * be anywhere in physical address space. The scratch regions give us a
- * safe zones that we will never see KHO allocations from. This is where we
- * can later safely load our new kexec images into and then use the scratch
- * area for early allocations that happen before page allocator is
- * initialized.
- */
-struct kho_scratch *kho_scratch;
-unsigned int kho_scratch_cnt;
-
-/*
- * The scratch areas are scaled by default as percent of memory allocated from
- * memblock. A user can override the scale with command line parameter:
- *
- * kho_scratch=N%
- *
- * It is also possible to explicitly define size for a lowmem, a global and
- * per-node scratch areas:
- *
- * kho_scratch=l[KMG],n[KMG],m[KMG]
- *
- * The explicit size definition takes precedence over scale definition.
- */
-static unsigned int scratch_scale __initdata = 200;
-static phys_addr_t scratch_size_global __initdata;
-static phys_addr_t scratch_size_pernode __initdata;
-static phys_addr_t scratch_size_lowmem __initdata;
-
-static int __init kho_parse_scratch_size(char *p)
-{
- size_t len;
- unsigned long sizes[3];
- size_t total_size = 0;
- int i;
-
- if (!p)
- return -EINVAL;
-
- len = strlen(p);
- if (!len)
- return -EINVAL;
-
- /* parse nn% */
- if (p[len - 1] == '%') {
- /* unsigned int max is 4,294,967,295, 10 chars */
- char s_scale[11] = {};
- int ret = 0;
-
- if (len > ARRAY_SIZE(s_scale))
- return -EINVAL;
-
- memcpy(s_scale, p, len - 1);
- ret = kstrtouint(s_scale, 10, &scratch_scale);
- if (!ret)
- pr_notice("scratch scale is %d%%\n", scratch_scale);
- return ret;
- }
-
- /* parse ll[KMG],mm[KMG],nn[KMG] */
- for (i = 0; i < ARRAY_SIZE(sizes); i++) {
- char *endp = p;
-
- if (i > 0) {
- if (*p != ',')
- return -EINVAL;
- p += 1;
- }
-
- sizes[i] = memparse(p, &endp);
- if (endp == p)
- return -EINVAL;
- p = endp;
- total_size += sizes[i];
- }
-
- if (!total_size)
- return -EINVAL;
-
- /* The string should be fully consumed by now. */
- if (*p)
- return -EINVAL;
-
- scratch_size_lowmem = sizes[0];
- scratch_size_global = sizes[1];
- scratch_size_pernode = sizes[2];
- scratch_scale = 0;
-
- pr_notice("scratch areas: lowmem: %lluMiB global: %lluMiB pernode: %lldMiB\n",
- (u64)(scratch_size_lowmem >> 20),
- (u64)(scratch_size_global >> 20),
- (u64)(scratch_size_pernode >> 20));
-
- return 0;
-}
-early_param("kho_scratch", kho_parse_scratch_size);
-
-static void __init scratch_size_update(void)
-{
- phys_addr_t size;
-
- if (!scratch_scale)
- return;
-
- size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
- NUMA_NO_NODE);
- size = size * scratch_scale / 100;
- scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-
- size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
- NUMA_NO_NODE);
- size = size * scratch_scale / 100 - scratch_size_lowmem;
- scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-}
-
-static phys_addr_t __init scratch_size_node(int nid)
-{
- phys_addr_t size;
-
- if (scratch_scale) {
- size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
- nid);
- size = size * scratch_scale / 100;
- } else {
- size = scratch_size_pernode;
- }
-
- return round_up(size, CMA_MIN_ALIGNMENT_BYTES);
-}
-
-/**
- * kho_reserve_scratch - Reserve a contiguous chunk of memory for kexec
- *
- * With KHO we can preserve arbitrary pages in the system. To ensure we still
- * have a large contiguous region of memory when we search the physical address
- * space for target memory, let's make sure we always have a large CMA region
- * active. This CMA region will only be used for movable pages which are not a
- * problem for us during KHO because we can just move them somewhere else.
- */
-static void __init kho_reserve_scratch(void)
-{
- phys_addr_t addr, size;
- int nid, i = 0;
-
- if (!kho_enable)
- return;
-
- scratch_size_update();
-
- /* FIXME: deal with node hot-plug/remove */
- kho_scratch_cnt = num_online_nodes() + 2;
- size = kho_scratch_cnt * sizeof(*kho_scratch);
- kho_scratch = memblock_alloc(size, PAGE_SIZE);
- if (!kho_scratch)
- goto err_disable_kho;
-
- /*
- * reserve scratch area in low memory for lowmem allocations in the
- * next kernel
- */
- size = scratch_size_lowmem;
- addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0,
- ARCH_LOW_ADDRESS_LIMIT);
- if (!addr)
- goto err_free_scratch_desc;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
-
- /* reserve large contiguous area for allocations without nid */
- size = scratch_size_global;
- addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES);
- if (!addr)
- goto err_free_scratch_areas;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
-
- for_each_online_node(nid) {
- size = scratch_size_node(nid);
- addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
- 0, MEMBLOCK_ALLOC_ACCESSIBLE,
- nid, true);
- if (!addr)
- goto err_free_scratch_areas;
-
- kho_scratch[i].addr = addr;
- kho_scratch[i].size = size;
- i++;
- }
-
- return;
-
-err_free_scratch_areas:
- for (i--; i >= 0; i--)
- memblock_phys_free(kho_scratch[i].addr, kho_scratch[i].size);
-err_free_scratch_desc:
- memblock_free(kho_scratch, kho_scratch_cnt * sizeof(*kho_scratch));
-err_disable_kho:
- pr_warn("Failed to reserve scratch area, disabling kexec handover\n");
- kho_enable = false;
-}
-
-/**
- * kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
- * @name: name of the sub tree.
- * @fdt: the sub tree blob.
- *
- * Creates a new child node named @name in KHO root FDT and records
- * the physical address of @fdt. The pages of @fdt must also be preserved
- * by KHO for the new kernel to retrieve it after kexec.
- *
- * A debugfs blob entry is also created at
- * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured with
- * CONFIG_KEXEC_HANDOVER_DEBUGFS
- *
- * Return: 0 on success, error code on failure
- */
-int kho_add_subtree(const char *name, void *fdt)
-{
- struct kho_sub_fdt *sub_fdt;
-
- sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL);
- if (!sub_fdt)
- return -ENOMEM;
-
- INIT_LIST_HEAD(&sub_fdt->l);
- sub_fdt->name = name;
- sub_fdt->fdt = fdt;
-
- guard(mutex)(&kho_out.fdts_lock);
- list_add_tail(&sub_fdt->l, &kho_out.sub_fdts);
- WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false));
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_add_subtree);
-
-void kho_remove_subtree(void *fdt)
-{
- struct kho_sub_fdt *sub_fdt;
-
- guard(mutex)(&kho_out.fdts_lock);
- list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) {
- if (sub_fdt->fdt == fdt) {
- list_del(&sub_fdt->l);
- kfree(sub_fdt);
- kho_debugfs_fdt_remove(&kho_out.dbg, fdt);
- break;
- }
- }
-}
-EXPORT_SYMBOL_GPL(kho_remove_subtree);
-
-/**
- * kho_preserve_folio - preserve a folio across kexec.
- * @folio: folio to preserve.
- *
- * Instructs KHO to preserve the whole folio across kexec. The order
- * will be preserved as well.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_folio(struct folio *folio)
-{
- const unsigned long pfn = folio_pfn(folio);
- const unsigned int order = folio_order(folio);
- struct kho_mem_track *track = &kho_out.track;
-
- if (WARN_ON(kho_scratch_overlap(pfn << PAGE_SHIFT, PAGE_SIZE << order)))
- return -EINVAL;
-
- return __kho_preserve_order(track, pfn, order);
-}
-EXPORT_SYMBOL_GPL(kho_preserve_folio);
-
-/**
- * kho_unpreserve_folio - unpreserve a folio.
- * @folio: folio to unpreserve.
- *
- * Instructs KHO to unpreserve a folio that was preserved by
- * kho_preserve_folio() before. The provided @folio (pfn and order)
- * must exactly match a previously preserved folio.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_unpreserve_folio(struct folio *folio)
-{
- const unsigned long pfn = folio_pfn(folio);
- const unsigned int order = folio_order(folio);
- struct kho_mem_track *track = &kho_out.track;
-
- if (kho_out.finalized)
- return -EBUSY;
-
- __kho_unpreserve_order(track, pfn, order);
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
-
-/**
- * kho_preserve_pages - preserve contiguous pages across kexec
- * @page: first page in the list.
- * @nr_pages: number of pages.
- *
- * Preserve a contiguous list of order 0 pages. Must be restored using
- * kho_restore_pages() to ensure the pages are restored properly as order 0.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_pages(struct page *page, unsigned int nr_pages)
-{
- struct kho_mem_track *track = &kho_out.track;
- const unsigned long start_pfn = page_to_pfn(page);
- const unsigned long end_pfn = start_pfn + nr_pages;
- unsigned long pfn = start_pfn;
- unsigned long failed_pfn = 0;
- int err = 0;
-
- if (WARN_ON(kho_scratch_overlap(start_pfn << PAGE_SHIFT,
- nr_pages << PAGE_SHIFT))) {
- return -EINVAL;
- }
-
- while (pfn < end_pfn) {
- const unsigned int order =
- min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
-
- err = __kho_preserve_order(track, pfn, order);
- if (err) {
- failed_pfn = pfn;
- break;
- }
-
- pfn += 1 << order;
- }
-
- if (err)
- __kho_unpreserve(track, start_pfn, failed_pfn);
-
- return err;
-}
-EXPORT_SYMBOL_GPL(kho_preserve_pages);
-
-/**
- * kho_unpreserve_pages - unpreserve contiguous pages.
- * @page: first page in the list.
- * @nr_pages: number of pages.
- *
- * Instructs KHO to unpreserve @nr_pages contiguous pages starting from @page.
- * This must be called with the same @page and @nr_pages as the corresponding
- * kho_preserve_pages() call. Unpreserving arbitrary sub-ranges of larger
- * preserved blocks is not supported.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
-{
- struct kho_mem_track *track = &kho_out.track;
- const unsigned long start_pfn = page_to_pfn(page);
- const unsigned long end_pfn = start_pfn + nr_pages;
-
- if (kho_out.finalized)
- return -EBUSY;
-
- __kho_unpreserve(track, start_pfn, end_pfn);
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_unpreserve_pages);
-
-struct kho_vmalloc_hdr {
- DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *);
-};
-
-#define KHO_VMALLOC_SIZE \
- ((PAGE_SIZE - sizeof(struct kho_vmalloc_hdr)) / \
- sizeof(phys_addr_t))
-
-struct kho_vmalloc_chunk {
- struct kho_vmalloc_hdr hdr;
- phys_addr_t phys[KHO_VMALLOC_SIZE];
-};
-
-static_assert(sizeof(struct kho_vmalloc_chunk) == PAGE_SIZE);
-
-/* vmalloc flags KHO supports */
-#define KHO_VMALLOC_SUPPORTED_FLAGS (VM_ALLOC | VM_ALLOW_HUGE_VMAP)
-
-/* KHO internal flags for vmalloc preservations */
-#define KHO_VMALLOC_ALLOC 0x0001
-#define KHO_VMALLOC_HUGE_VMAP 0x0002
-
-static unsigned short vmalloc_flags_to_kho(unsigned int vm_flags)
-{
- unsigned short kho_flags = 0;
-
- if (vm_flags & VM_ALLOC)
- kho_flags |= KHO_VMALLOC_ALLOC;
- if (vm_flags & VM_ALLOW_HUGE_VMAP)
- kho_flags |= KHO_VMALLOC_HUGE_VMAP;
-
- return kho_flags;
-}
-
-static unsigned int kho_flags_to_vmalloc(unsigned short kho_flags)
-{
- unsigned int vm_flags = 0;
-
- if (kho_flags & KHO_VMALLOC_ALLOC)
- vm_flags |= VM_ALLOC;
- if (kho_flags & KHO_VMALLOC_HUGE_VMAP)
- vm_flags |= VM_ALLOW_HUGE_VMAP;
-
- return vm_flags;
-}
-
-static struct kho_vmalloc_chunk *new_vmalloc_chunk(struct kho_vmalloc_chunk *cur)
-{
- struct kho_vmalloc_chunk *chunk;
- int err;
-
- chunk = (struct kho_vmalloc_chunk *)get_zeroed_page(GFP_KERNEL);
- if (!chunk)
- return NULL;
-
- err = kho_preserve_pages(virt_to_page(chunk), 1);
- if (err)
- goto err_free;
- if (cur)
- KHOSER_STORE_PTR(cur->hdr.next, chunk);
- return chunk;
-
-err_free:
- free_page((unsigned long)chunk);
- return NULL;
-}
-
-static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk,
- unsigned short order)
-{
- struct kho_mem_track *track = &kho_out.track;
- unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
-
- __kho_unpreserve(track, pfn, pfn + 1);
-
- for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
- pfn = PHYS_PFN(chunk->phys[i]);
- __kho_unpreserve(track, pfn, pfn + (1 << order));
- }
-}
-
-static void kho_vmalloc_free_chunks(struct kho_vmalloc *kho_vmalloc)
-{
- struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(kho_vmalloc->first);
-
- while (chunk) {
- struct kho_vmalloc_chunk *tmp = chunk;
-
- kho_vmalloc_unpreserve_chunk(chunk, kho_vmalloc->order);
-
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- free_page((unsigned long)tmp);
- }
-}
-
-/**
- * kho_preserve_vmalloc - preserve memory allocated with vmalloc() across kexec
- * @ptr: pointer to the area in vmalloc address space
- * @preservation: placeholder for preservation metadata
- *
- * Instructs KHO to preserve the area in vmalloc address space at @ptr. The
- * physical pages mapped at @ptr will be preserved and on successful return
- * @preservation will hold the physical address of a structure that describes
- * the preservation.
- *
- * NOTE: The memory allocated with vmalloc_node() variants cannot be reliably
- * restored on the same node
- *
- * Return: 0 on success, error code on failure
- */
-int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
-{
- struct kho_vmalloc_chunk *chunk;
- struct vm_struct *vm = find_vm_area(ptr);
- unsigned int order, flags, nr_contig_pages;
- unsigned int idx = 0;
- int err;
-
- if (!vm)
- return -EINVAL;
-
- if (vm->flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
- return -EOPNOTSUPP;
-
- flags = vmalloc_flags_to_kho(vm->flags);
- order = get_vm_area_page_order(vm);
-
- chunk = new_vmalloc_chunk(NULL);
- if (!chunk)
- return -ENOMEM;
- KHOSER_STORE_PTR(preservation->first, chunk);
-
- nr_contig_pages = (1 << order);
- for (int i = 0; i < vm->nr_pages; i += nr_contig_pages) {
- phys_addr_t phys = page_to_phys(vm->pages[i]);
-
- err = kho_preserve_pages(vm->pages[i], nr_contig_pages);
- if (err)
- goto err_free;
-
- chunk->phys[idx++] = phys;
- if (idx == ARRAY_SIZE(chunk->phys)) {
- chunk = new_vmalloc_chunk(chunk);
- if (!chunk)
- goto err_free;
- idx = 0;
- }
- }
-
- preservation->total_pages = vm->nr_pages;
- preservation->flags = flags;
- preservation->order = order;
-
- return 0;
-
-err_free:
- kho_vmalloc_free_chunks(preservation);
- return err;
-}
-EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
-
-/**
- * kho_unpreserve_vmalloc - unpreserve memory allocated with vmalloc()
- * @preservation: preservation metadata returned by kho_preserve_vmalloc()
- *
- * Instructs KHO to unpreserve the area in vmalloc address space that was
- * previously preserved with kho_preserve_vmalloc().
- *
- * Return: 0 on success, error code on failure
- */
-int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
-{
- if (kho_out.finalized)
- return -EBUSY;
-
- kho_vmalloc_free_chunks(preservation);
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_unpreserve_vmalloc);
-
-/**
- * kho_restore_vmalloc - recreates and populates an area in vmalloc address
- * space from the preserved memory.
- * @preservation: preservation metadata.
- *
- * Recreates an area in vmalloc address space and populates it with memory that
- * was preserved using kho_preserve_vmalloc().
- *
- * Return: pointer to the area in the vmalloc address space, NULL on failure.
- */
-void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
-{
- struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(preservation->first);
- unsigned int align, order, shift, vm_flags;
- unsigned long total_pages, contig_pages;
- unsigned long addr, size;
- struct vm_struct *area;
- struct page **pages;
- unsigned int idx = 0;
- int err;
-
- vm_flags = kho_flags_to_vmalloc(preservation->flags);
- if (vm_flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
- return NULL;
-
- total_pages = preservation->total_pages;
- pages = kvmalloc_array(total_pages, sizeof(*pages), GFP_KERNEL);
- if (!pages)
- return NULL;
- order = preservation->order;
- contig_pages = (1 << order);
- shift = PAGE_SHIFT + order;
- align = 1 << shift;
-
- while (chunk) {
- struct page *page;
-
- for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
- phys_addr_t phys = chunk->phys[i];
-
- if (idx + contig_pages > total_pages)
- goto err_free_pages_array;
-
- page = kho_restore_pages(phys, contig_pages);
- if (!page)
- goto err_free_pages_array;
-
- for (int j = 0; j < contig_pages; j++)
- pages[idx++] = page;
-
- phys += contig_pages * PAGE_SIZE;
- }
-
- page = kho_restore_pages(virt_to_phys(chunk), 1);
- if (!page)
- goto err_free_pages_array;
- chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
- __free_page(page);
- }
-
- if (idx != total_pages)
- goto err_free_pages_array;
-
- area = __get_vm_area_node(total_pages * PAGE_SIZE, align, shift,
- vm_flags, VMALLOC_START, VMALLOC_END,
- NUMA_NO_NODE, GFP_KERNEL,
- __builtin_return_address(0));
- if (!area)
- goto err_free_pages_array;
-
- addr = (unsigned long)area->addr;
- size = get_vm_area_size(area);
- err = vmap_pages_range(addr, addr + size, PAGE_KERNEL, pages, shift);
- if (err)
- goto err_free_vm_area;
-
- area->nr_pages = total_pages;
- area->pages = pages;
-
- return area->addr;
-
-err_free_vm_area:
- free_vm_area(area);
-err_free_pages_array:
- kvfree(pages);
- return NULL;
-}
-EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
-
-static int __kho_abort(void)
-{
- if (kho_out.preserved_mem_map) {
- kho_mem_ser_free(kho_out.preserved_mem_map);
- kho_out.preserved_mem_map = NULL;
- }
-
- return 0;
-}
-
-int kho_abort(void)
-{
- int ret = 0;
-
- if (!kho_enable)
- return -EOPNOTSUPP;
-
- guard(mutex)(&kho_out.lock);
- if (!kho_out.finalized)
- return -ENOENT;
-
- ret = __kho_abort();
- if (ret)
- return ret;
-
- kho_out.finalized = false;
-
- kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt);
-
- return 0;
-}
-
-static int __kho_finalize(void)
-{
- int err = 0;
- u64 *preserved_mem_map;
- void *root = kho_out.fdt;
- struct kho_sub_fdt *fdt;
-
- err |= fdt_create(root, PAGE_SIZE);
- err |= fdt_finish_reservemap(root);
- err |= fdt_begin_node(root, "");
- err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
- /**
- * Reserve the preserved-memory-map property in the root FDT, so
- * that all property definitions will precede subnodes created by
- * KHO callers.
- */
- err |= fdt_property_placeholder(root, PROP_PRESERVED_MEMORY_MAP,
- sizeof(*preserved_mem_map),
- (void **)&preserved_mem_map);
- if (err)
- goto abort;
-
- err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
- if (err)
- goto abort;
-
- err = kho_mem_serialize(&kho_out);
- if (err)
- goto abort;
-
- *preserved_mem_map = (u64)virt_to_phys(kho_out.preserved_mem_map);
-
- mutex_lock(&kho_out.fdts_lock);
- list_for_each_entry(fdt, &kho_out.sub_fdts, l) {
- phys_addr_t phys = virt_to_phys(fdt->fdt);
-
- err |= fdt_begin_node(root, fdt->name);
- err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
- err |= fdt_end_node(root);
- }
- mutex_unlock(&kho_out.fdts_lock);
-
- err |= fdt_end_node(root);
- err |= fdt_finish(root);
-
-abort:
- if (err) {
- pr_err("Failed to convert KHO state tree: %d\n", err);
- __kho_abort();
- }
-
- return err;
-}
-
-int kho_finalize(void)
-{
- int ret;
-
- if (!kho_enable)
- return -EOPNOTSUPP;
-
- guard(mutex)(&kho_out.lock);
- if (kho_out.finalized)
- return -EEXIST;
-
- ret = __kho_finalize();
- if (ret)
- return ret;
-
- kho_out.finalized = true;
-
- WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
- kho_out.fdt, true));
-
- return 0;
-}
-
-bool kho_finalized(void)
-{
- guard(mutex)(&kho_out.lock);
- return kho_out.finalized;
-}
-
-struct kho_in {
- phys_addr_t fdt_phys;
- phys_addr_t scratch_phys;
- struct kho_debugfs dbg;
-};
-
-static struct kho_in kho_in = {
-};
-
-static const void *kho_get_fdt(void)
-{
- return kho_in.fdt_phys ? phys_to_virt(kho_in.fdt_phys) : NULL;
-}
-
-/**
- * is_kho_boot - check if current kernel was booted via KHO-enabled
- * kexec
- *
- * This function checks if the current kernel was loaded through a kexec
- * operation with KHO enabled, by verifying that a valid KHO FDT
- * was passed.
- *
- * Note: This function returns reliable results only after
- * kho_populate() has been called during early boot. Before that,
- * it may return false even if KHO data is present.
- *
- * Return: true if booted via KHO-enabled kexec, false otherwise
- */
-bool is_kho_boot(void)
-{
- return !!kho_get_fdt();
-}
-EXPORT_SYMBOL_GPL(is_kho_boot);
-
-/**
- * kho_retrieve_subtree - retrieve a preserved sub FDT by its name.
- * @name: the name of the sub FDT passed to kho_add_subtree().
- * @phys: if found, the physical address of the sub FDT is stored in @phys.
- *
- * Retrieve a preserved sub FDT named @name and store its physical
- * address in @phys.
- *
- * Return: 0 on success, error code on failure
- */
-int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
-{
- const void *fdt = kho_get_fdt();
- const u64 *val;
- int offset, len;
-
- if (!fdt)
- return -ENOENT;
-
- if (!phys)
- return -EINVAL;
-
- offset = fdt_subnode_offset(fdt, 0, name);
- if (offset < 0)
- return -ENOENT;
-
- val = fdt_getprop(fdt, offset, PROP_SUB_FDT, &len);
- if (!val || len != sizeof(*val))
- return -EINVAL;
-
- *phys = (phys_addr_t)*val;
-
- return 0;
-}
-EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
-
-static __init int kho_init(void)
-{
- int err = 0;
- const void *fdt = kho_get_fdt();
- struct page *fdt_page;
-
- if (!kho_enable)
- return 0;
-
- fdt_page = alloc_page(GFP_KERNEL);
- if (!fdt_page) {
- err = -ENOMEM;
- goto err_free_scratch;
- }
- kho_out.fdt = page_to_virt(fdt_page);
-
- err = kho_debugfs_init();
- if (err)
- goto err_free_fdt;
-
- err = kho_out_debugfs_init(&kho_out.dbg);
- if (err)
- goto err_free_fdt;
-
- if (fdt) {
- kho_in_debugfs_init(&kho_in.dbg, fdt);
- return 0;
- }
-
- for (int i = 0; i < kho_scratch_cnt; i++) {
- unsigned long base_pfn = PHYS_PFN(kho_scratch[i].addr);
- unsigned long count = kho_scratch[i].size >> PAGE_SHIFT;
- unsigned long pfn;
-
- for (pfn = base_pfn; pfn < base_pfn + count;
- pfn += pageblock_nr_pages)
- init_cma_reserved_pageblock(pfn_to_page(pfn));
- }
-
- return 0;
-
-err_free_fdt:
- put_page(fdt_page);
- kho_out.fdt = NULL;
-err_free_scratch:
- for (int i = 0; i < kho_scratch_cnt; i++) {
- void *start = __va(kho_scratch[i].addr);
- void *end = start + kho_scratch[i].size;
-
- free_reserved_area(start, end, -1, "");
- }
- kho_enable = false;
- return err;
-}
-fs_initcall(kho_init);
-
-static void __init kho_release_scratch(void)
-{
- phys_addr_t start, end;
- u64 i;
-
- memmap_init_kho_scratch_pages();
-
- /*
- * Mark scratch mem as CMA before we return it. That way we
- * ensure that no kernel allocations happen on it. That means
- * we can reuse it as scratch memory again later.
- */
- __for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
- MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
- ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
- ulong end_pfn = pageblock_align(PFN_UP(end));
- ulong pfn;
-
- for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
- init_pageblock_migratetype(pfn_to_page(pfn),
- MIGRATE_CMA, false);
- }
-}
-
-void __init kho_memory_init(void)
-{
- struct folio *folio;
-
- if (kho_in.scratch_phys) {
- kho_scratch = phys_to_virt(kho_in.scratch_phys);
- kho_release_scratch();
-
- kho_mem_deserialize(kho_get_fdt());
- folio = kho_restore_folio(kho_in.fdt_phys);
- if (!folio)
- pr_warn("failed to restore folio for KHO fdt\n");
- } else {
- kho_reserve_scratch();
- }
-}
-
-void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
- phys_addr_t scratch_phys, u64 scratch_len)
-{
- void *fdt = NULL;
- struct kho_scratch *scratch = NULL;
- int err = 0;
- unsigned int scratch_cnt = scratch_len / sizeof(*kho_scratch);
-
- /* Validate the input FDT */
- fdt = early_memremap(fdt_phys, fdt_len);
- if (!fdt) {
- pr_warn("setup: failed to memremap FDT (0x%llx)\n", fdt_phys);
- err = -EFAULT;
- goto out;
- }
- err = fdt_check_header(fdt);
- if (err) {
- pr_warn("setup: handover FDT (0x%llx) is invalid: %d\n",
- fdt_phys, err);
- err = -EINVAL;
- goto out;
- }
- err = fdt_node_check_compatible(fdt, 0, KHO_FDT_COMPATIBLE);
- if (err) {
- pr_warn("setup: handover FDT (0x%llx) is incompatible with '%s': %d\n",
- fdt_phys, KHO_FDT_COMPATIBLE, err);
- err = -EINVAL;
- goto out;
- }
-
- scratch = early_memremap(scratch_phys, scratch_len);
- if (!scratch) {
- pr_warn("setup: failed to memremap scratch (phys=0x%llx, len=%lld)\n",
- scratch_phys, scratch_len);
- err = -EFAULT;
- goto out;
- }
-
- /*
- * We pass a safe contiguous blocks of memory to use for early boot
- * purporses from the previous kernel so that we can resize the
- * memblock array as needed.
- */
- for (int i = 0; i < scratch_cnt; i++) {
- struct kho_scratch *area = &scratch[i];
- u64 size = area->size;
-
- memblock_add(area->addr, size);
- err = memblock_mark_kho_scratch(area->addr, size);
- if (WARN_ON(err)) {
- pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %d",
- &area->addr, &size, err);
- goto out;
- }
- pr_debug("Marked 0x%pa+0x%pa as scratch", &area->addr, &size);
- }
-
- memblock_reserve(scratch_phys, scratch_len);
-
- /*
- * Now that we have a viable region of scratch memory, let's tell
- * the memblocks allocator to only use that for any allocations.
- * That way we ensure that nothing scribbles over in use data while
- * we initialize the page tables which we will need to ingest all
- * memory reservations from the previous kernel.
- */
- memblock_set_kho_scratch_only();
-
- kho_in.fdt_phys = fdt_phys;
- kho_in.scratch_phys = scratch_phys;
- kho_scratch_cnt = scratch_cnt;
- pr_info("found kexec handover data. Will skip init for some devices\n");
-
-out:
- if (fdt)
- early_memunmap(fdt, fdt_len);
- if (scratch)
- early_memunmap(scratch, scratch_len);
- if (err)
- pr_warn("disabling KHO revival: %d\n", err);
-}
-
-/* Helper functions for kexec_file_load */
-
-int kho_fill_kimage(struct kimage *image)
-{
- ssize_t scratch_size;
- int err = 0;
- struct kexec_buf scratch;
-
- if (!kho_out.finalized)
- return 0;
-
- image->kho.fdt = virt_to_phys(kho_out.fdt);
-
- scratch_size = sizeof(*kho_scratch) * kho_scratch_cnt;
- scratch = (struct kexec_buf){
- .image = image,
- .buffer = kho_scratch,
- .bufsz = scratch_size,
- .mem = KEXEC_BUF_MEM_UNKNOWN,
- .memsz = scratch_size,
- .buf_align = SZ_64K, /* Makes it easier to map */
- .buf_max = ULONG_MAX,
- .top_down = true,
- };
- err = kexec_add_buffer(&scratch);
- if (err)
- return err;
- image->kho.scratch = &image->segment[image->nr_segments - 1];
-
- return 0;
-}
-
-static int kho_walk_scratch(struct kexec_buf *kbuf,
- int (*func)(struct resource *, void *))
-{
- int ret = 0;
- int i;
-
- for (i = 0; i < kho_scratch_cnt; i++) {
- struct resource res = {
- .start = kho_scratch[i].addr,
- .end = kho_scratch[i].addr + kho_scratch[i].size - 1,
- };
-
- /* Try to fit the kimage into our KHO scratch region */
- ret = func(&res, kbuf);
- if (ret)
- break;
- }
-
- return ret;
-}
-
-int kho_locate_mem_hole(struct kexec_buf *kbuf,
- int (*func)(struct resource *, void *))
-{
- int ret;
-
- if (!kho_enable || kbuf->image->type == KEXEC_TYPE_CRASH)
- return 1;
-
- ret = kho_walk_scratch(kbuf, func);
-
- return ret == 1 ? 0 : -EADDRNOTAVAIL;
-}
diff --git a/kernel/kexec_handover_debug.c a/kernel/kexec_handover_debug.c
deleted file mode 100644
--- a/kernel/kexec_handover_debug.c
+++ /dev/null
@@ -1,25 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover_debug.c - kexec handover optional debug functionality
- * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include "kexec_handover_internal.h"
-
-bool kho_scratch_overlap(phys_addr_t phys, size_t size)
-{
- phys_addr_t scratch_start, scratch_end;
- unsigned int i;
-
- for (i = 0; i < kho_scratch_cnt; i++) {
- scratch_start = kho_scratch[i].addr;
- scratch_end = kho_scratch[i].addr + kho_scratch[i].size;
-
- if (phys < scratch_end && (phys + size) > scratch_start)
- return true;
- }
-
- return false;
-}
diff --git a/kernel/kexec_handover_debugfs.c a/kernel/kexec_handover_debugfs.c
deleted file mode 100644
--- a/kernel/kexec_handover_debugfs.c
+++ /dev/null
@@ -1,219 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * kexec_handover_debugfs.c - kexec handover debugfs interfaces
- * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
- * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
- * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
- * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
- */
-
-#define pr_fmt(fmt) "KHO: " fmt
-
-#include <linux/init.h>
-#include <linux/io.h>
-#include <linux/libfdt.h>
-#include <linux/mm.h>
-#include "kexec_handover_internal.h"
-
-static struct dentry *debugfs_root;
-
-struct fdt_debugfs {
- struct list_head list;
- struct debugfs_blob_wrapper wrapper;
- struct dentry *file;
-};
-
-static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
- const char *name, const void *fdt)
-{
- struct fdt_debugfs *f;
- struct dentry *file;
-
- f = kmalloc(sizeof(*f), GFP_KERNEL);
- if (!f)
- return -ENOMEM;
-
- f->wrapper.data = (void *)fdt;
- f->wrapper.size = fdt_totalsize(fdt);
-
- file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
- if (IS_ERR(file)) {
- kfree(f);
- return PTR_ERR(file);
- }
-
- f->file = file;
- list_add(&f->list, list);
-
- return 0;
-}
-
-int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root)
-{
- struct dentry *dir;
-
- if (root)
- dir = dbg->dir;
- else
- dir = dbg->sub_fdt_dir;
-
- return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
-}
-
-void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt)
-{
- struct fdt_debugfs *ff;
-
- list_for_each_entry(ff, &dbg->fdt_list, list) {
- if (ff->wrapper.data == fdt) {
- debugfs_remove(ff->file);
- list_del(&ff->list);
- kfree(ff);
- break;
- }
- }
-}
-
-static int kho_out_finalize_get(void *data, u64 *val)
-{
- *val = kho_finalized();
-
- return 0;
-}
-
-static int kho_out_finalize_set(void *data, u64 val)
-{
- if (val)
- return kho_finalize();
- else
- return kho_abort();
-}
-
-DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
- kho_out_finalize_set, "%llu\n");
-
-static int scratch_phys_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_phys);
-
-static int scratch_len_show(struct seq_file *m, void *v)
-{
- for (int i = 0; i < kho_scratch_cnt; i++)
- seq_printf(m, "0x%llx\n", kho_scratch[i].size);
-
- return 0;
-}
-DEFINE_SHOW_ATTRIBUTE(scratch_len);
-
-__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
-{
- struct dentry *dir, *sub_fdt_dir;
- int err, child;
-
- INIT_LIST_HEAD(&dbg->fdt_list);
-
- dir = debugfs_create_dir("in", debugfs_root);
- if (IS_ERR(dir)) {
- err = PTR_ERR(dir);
- goto err_out;
- }
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
- if (IS_ERR(sub_fdt_dir)) {
- err = PTR_ERR(sub_fdt_dir);
- goto err_rmdir;
- }
-
- err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt);
- if (err)
- goto err_rmdir;
-
- fdt_for_each_subnode(child, fdt, 0) {
- int len = 0;
- const char *name = fdt_get_name(fdt, child, NULL);
- const u64 *fdt_phys;
-
- fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
- if (!fdt_phys)
- continue;
- if (len != sizeof(*fdt_phys)) {
- pr_warn("node %s prop fdt has invalid length: %d\n",
- name, len);
- continue;
- }
- err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
- phys_to_virt(*fdt_phys));
- if (err) {
- pr_warn("failed to add fdt %s to debugfs: %d\n", name,
- err);
- continue;
- }
- }
-
- dbg->dir = dir;
- dbg->sub_fdt_dir = sub_fdt_dir;
-
- return;
-err_rmdir:
- debugfs_remove_recursive(dir);
-err_out:
- /*
- * Failure to create /sys/kernel/debug/kho/in does not prevent
- * reviving state from KHO and setting up KHO for the next
- * kexec.
- */
- if (err)
- pr_err("failed exposing handover FDT in debugfs: %d\n", err);
-}
-
-__init int kho_out_debugfs_init(struct kho_debugfs *dbg)
-{
- struct dentry *dir, *f, *sub_fdt_dir;
-
- INIT_LIST_HEAD(&dbg->fdt_list);
-
- dir = debugfs_create_dir("out", debugfs_root);
- if (IS_ERR(dir))
- return -ENOMEM;
-
- sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
- if (IS_ERR(sub_fdt_dir))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
- &scratch_phys_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("scratch_len", 0400, dir, NULL,
- &scratch_len_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- f = debugfs_create_file("finalize", 0600, dir, NULL,
- &kho_out_finalize_fops);
- if (IS_ERR(f))
- goto err_rmdir;
-
- dbg->dir = dir;
- dbg->sub_fdt_dir = sub_fdt_dir;
- return 0;
-
-err_rmdir:
- debugfs_remove_recursive(dir);
- return -ENOENT;
-}
-
-__init int kho_debugfs_init(void)
-{
- debugfs_root = debugfs_create_dir("kho", NULL);
- if (IS_ERR(debugfs_root))
- return -ENOENT;
- return 0;
-}
diff --git a/kernel/kexec_handover_internal.h a/kernel/kexec_handover_internal.h
deleted file mode 100644
--- a/kernel/kexec_handover_internal.h
+++ /dev/null
@@ -1,56 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
-#define LINUX_KEXEC_HANDOVER_INTERNAL_H
-
-#include <linux/kexec_handover.h>
-#include <linux/list.h>
-#include <linux/types.h>
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
-#include <linux/debugfs.h>
-
-struct kho_debugfs {
- struct dentry *dir;
- struct dentry *sub_fdt_dir;
- struct list_head fdt_list;
-};
-
-#else
-struct kho_debugfs {};
-#endif
-
-extern struct kho_scratch *kho_scratch;
-extern unsigned int kho_scratch_cnt;
-
-bool kho_finalized(void);
-int kho_finalize(void);
-int kho_abort(void);
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
-int kho_debugfs_init(void);
-void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
-int kho_out_debugfs_init(struct kho_debugfs *dbg);
-int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root);
-void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt);
-#else
-static inline int kho_debugfs_init(void) { return 0; }
-static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
- const void *fdt) { }
-static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
-static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
- const void *fdt, bool root) { return 0; }
-static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg,
- void *fdt) { }
-#endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */
-
-#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
-bool kho_scratch_overlap(phys_addr_t phys, size_t size);
-#else
-static inline bool kho_scratch_overlap(phys_addr_t phys, size_t size)
-{
- return false;
-}
-#endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
-
-#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
diff --git a/kernel/liveupdate/Kconfig a/kernel/liveupdate/Kconfig
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/Kconfig
@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+menu "Live Update and Kexec HandOver"
+
+config KEXEC_HANDOVER
+ bool "kexec handover"
+ depends on ARCH_SUPPORTS_KEXEC_HANDOVER && ARCH_SUPPORTS_KEXEC_FILE
+ depends on !DEFERRED_STRUCT_PAGE_INIT
+ select MEMBLOCK_KHO_SCRATCH
+ select KEXEC_FILE
+ select LIBFDT
+ select CMA
+ help
+ Allow kexec to hand over state across kernels by generating and
+ passing additional metadata to the target kernel. This is useful
+ to keep data or state alive across the kexec. For this to work,
+ both source and target kernels need to have this option enabled.
+
+config KEXEC_HANDOVER_DEBUG
+ bool "Enable Kexec Handover debug checks"
+ depends on KEXEC_HANDOVER
+ help
+ This option enables extra sanity checks for the Kexec Handover
+ subsystem. Since, KHO performance is crucial in live update
+ scenarios and the extra code might be adding overhead it is
+ only optionally enabled.
+
+config KEXEC_HANDOVER_DEBUGFS
+ bool "kexec handover debugfs interface"
+ default KEXEC_HANDOVER
+ depends on KEXEC_HANDOVER
+ select DEBUG_FS
+ help
+ Allow to control kexec handover device tree via debugfs
+ interface, i.e. finalize the state or aborting the finalization.
+ Also, enables inspecting the KHO fdt trees with the debugfs binary
+ blobs.
+
+endmenu
diff --git a/kernel/liveupdate/kexec_handover.c a/kernel/liveupdate/kexec_handover.c
new file mode 100664
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover.c
@@ -0,0 +1,1548 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover.c - kexec handover metadata processing
+ * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
+ * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
+ * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include <linux/cleanup.h>
+#include <linux/cma.h>
+#include <linux/count_zeros.h>
+#include <linux/kexec.h>
+#include <linux/kexec_handover.h>
+#include <linux/libfdt.h>
+#include <linux/list.h>
+#include <linux/memblock.h>
+#include <linux/page-isolation.h>
+#include <linux/vmalloc.h>
+
+#include <asm/early_ioremap.h>
+
+#include "kexec_handover_internal.h"
+/*
+ * KHO is tightly coupled with mm init and needs access to some of mm
+ * internal APIs.
+ */
+#include "../../mm/internal.h"
+#include "../kexec_internal.h"
+#include "kexec_handover_internal.h"
+
+#define KHO_FDT_COMPATIBLE "kho-v1"
+#define PROP_PRESERVED_MEMORY_MAP "preserved-memory-map"
+#define PROP_SUB_FDT "fdt"
+
+#define KHO_PAGE_MAGIC 0x4b484f50U /* ASCII for 'KHOP' */
+
+/*
+ * KHO uses page->private, which is an unsigned long, to store page metadata.
+ * Use it to store both the magic and the order.
+ */
+union kho_page_info {
+ unsigned long page_private;
+ struct {
+ unsigned int order;
+ unsigned int magic;
+ };
+};
+
+static_assert(sizeof(union kho_page_info) == sizeof(((struct page *)0)->private));
+
+static bool kho_enable __ro_after_init;
+
+bool kho_is_enabled(void)
+{
+ return kho_enable;
+}
+EXPORT_SYMBOL_GPL(kho_is_enabled);
+
+static int __init kho_parse_enable(char *p)
+{
+ return kstrtobool(p, &kho_enable);
+}
+early_param("kho", kho_parse_enable);
+
+/*
+ * Keep track of memory that is to be preserved across KHO.
+ *
+ * The serializing side uses two levels of xarrays to manage chunks of per-order
+ * PAGE_SIZE byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order
+ * of a 8TB system would fit inside a single 4096 byte bitmap. For order 0
+ * allocations each bitmap will cover 128M of address space. Thus, for 16G of
+ * memory at most 512K of bitmap memory will be needed for order 0.
+ *
+ * This approach is fully incremental, as the serialization progresses folios
+ * can continue be aggregated to the tracker. The final step, immediately prior
+ * to kexec would serialize the xarray information into a linked list for the
+ * successor kernel to parse.
+ */
+
+#define PRESERVE_BITS (PAGE_SIZE * 8)
+
+struct kho_mem_phys_bits {
+ DECLARE_BITMAP(preserve, PRESERVE_BITS);
+};
+
+static_assert(sizeof(struct kho_mem_phys_bits) == PAGE_SIZE);
+
+struct kho_mem_phys {
+ /*
+ * Points to kho_mem_phys_bits, a sparse bitmap array. Each bit is sized
+ * to order.
+ */
+ struct xarray phys_bits;
+};
+
+struct kho_mem_track {
+ /* Points to kho_mem_phys, each order gets its own bitmap tree */
+ struct xarray orders;
+};
+
+struct khoser_mem_chunk;
+
+struct kho_sub_fdt {
+ struct list_head l;
+ const char *name;
+ void *fdt;
+};
+
+struct kho_out {
+ void *fdt;
+ bool finalized;
+ struct mutex lock; /* protects KHO FDT finalization */
+
+ struct list_head sub_fdts;
+ struct mutex fdts_lock;
+
+ struct kho_mem_track track;
+ /* First chunk of serialized preserved memory map */
+ struct khoser_mem_chunk *preserved_mem_map;
+
+ struct kho_debugfs dbg;
+};
+
+static struct kho_out kho_out = {
+ .lock = __MUTEX_INITIALIZER(kho_out.lock),
+ .track = {
+ .orders = XARRAY_INIT(kho_out.track.orders, 0),
+ },
+ .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts),
+ .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock),
+ .finalized = false,
+};
+
+static void *xa_load_or_alloc(struct xarray *xa, unsigned long index)
+{
+ void *res = xa_load(xa, index);
+
+ if (res)
+ return res;
+
+ void *elm __free(free_page) = (void *)get_zeroed_page(GFP_KERNEL);
+
+ if (!elm)
+ return ERR_PTR(-ENOMEM);
+
+ if (WARN_ON(kho_scratch_overlap(virt_to_phys(elm), PAGE_SIZE)))
+ return ERR_PTR(-EINVAL);
+
+ res = xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
+ if (xa_is_err(res))
+ return ERR_PTR(xa_err(res));
+ else if (res)
+ return res;
+
+ return no_free_ptr(elm);
+}
+
+static void __kho_unpreserve_order(struct kho_mem_track *track, unsigned long pfn,
+ unsigned int order)
+{
+ struct kho_mem_phys_bits *bits;
+ struct kho_mem_phys *physxa;
+ const unsigned long pfn_high = pfn >> order;
+
+ physxa = xa_load(&track->orders, order);
+ if (WARN_ON_ONCE(!physxa))
+ return;
+
+ bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
+ if (WARN_ON_ONCE(!bits))
+ return;
+
+ clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+}
+
+static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
+ unsigned long end_pfn)
+{
+ unsigned int order;
+
+ while (pfn < end_pfn) {
+ order = min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+
+ __kho_unpreserve_order(track, pfn, order);
+
+ pfn += 1 << order;
+ }
+}
+
+static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
+ unsigned int order)
+{
+ struct kho_mem_phys_bits *bits;
+ struct kho_mem_phys *physxa, *new_physxa;
+ const unsigned long pfn_high = pfn >> order;
+
+ might_sleep();
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ physxa = xa_load(&track->orders, order);
+ if (!physxa) {
+ int err;
+
+ new_physxa = kzalloc(sizeof(*physxa), GFP_KERNEL);
+ if (!new_physxa)
+ return -ENOMEM;
+
+ xa_init(&new_physxa->phys_bits);
+ physxa = xa_cmpxchg(&track->orders, order, NULL, new_physxa,
+ GFP_KERNEL);
+
+ err = xa_err(physxa);
+ if (err || physxa) {
+ xa_destroy(&new_physxa->phys_bits);
+ kfree(new_physxa);
+
+ if (err)
+ return err;
+ } else {
+ physxa = new_physxa;
+ }
+ }
+
+ bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
+ if (IS_ERR(bits))
+ return PTR_ERR(bits);
+
+ set_bit(pfn_high % PRESERVE_BITS, bits->preserve);
+
+ return 0;
+}
+
+static struct page *kho_restore_page(phys_addr_t phys)
+{
+ struct page *page = pfn_to_online_page(PHYS_PFN(phys));
+ union kho_page_info info;
+ unsigned int nr_pages;
+
+ if (!page)
+ return NULL;
+
+ info.page_private = page->private;
+ /*
+ * deserialize_bitmap() only sets the magic on the head page. This magic
+ * check also implicitly makes sure phys is order-aligned since for
+ * non-order-aligned phys addresses, magic will never be set.
+ */
+ if (WARN_ON_ONCE(info.magic != KHO_PAGE_MAGIC || info.order > MAX_PAGE_ORDER))
+ return NULL;
+ nr_pages = (1 << info.order);
+
+ /* Clear private to make sure later restores on this page error out. */
+ page->private = 0;
+ /* Head page gets refcount of 1. */
+ set_page_count(page, 1);
+
+ /* For higher order folios, tail pages get a page count of zero. */
+ for (unsigned int i = 1; i < nr_pages; i++)
+ set_page_count(page + i, 0);
+
+ if (info.order > 0)
+ prep_compound_page(page, info.order);
+
+ adjust_managed_page_count(page, nr_pages);
+ return page;
+}
+
+/**
+ * kho_restore_folio - recreates the folio from the preserved memory.
+ * @phys: physical address of the folio.
+ *
+ * Return: pointer to the struct folio on success, NULL on failure.
+ */
+struct folio *kho_restore_folio(phys_addr_t phys)
+{
+ struct page *page = kho_restore_page(phys);
+
+ return page ? page_folio(page) : NULL;
+}
+EXPORT_SYMBOL_GPL(kho_restore_folio);
+
+/**
+ * kho_restore_pages - restore list of contiguous order 0 pages.
+ * @phys: physical address of the first page.
+ * @nr_pages: number of pages.
+ *
+ * Restore a contiguous list of order 0 pages that was preserved with
+ * kho_preserve_pages().
+ *
+ * Return: 0 on success, error code on failure
+ */
+struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages)
+{
+ const unsigned long start_pfn = PHYS_PFN(phys);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+ unsigned long pfn = start_pfn;
+
+ while (pfn < end_pfn) {
+ const unsigned int order =
+ min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+ struct page *page = kho_restore_page(PFN_PHYS(pfn));
+
+ if (!page)
+ return NULL;
+ split_page(page, order);
+ pfn += 1 << order;
+ }
+
+ return pfn_to_page(start_pfn);
+}
+EXPORT_SYMBOL_GPL(kho_restore_pages);
+
+/* Serialize and deserialize struct kho_mem_phys across kexec
+ *
+ * Record all the bitmaps in a linked list of pages for the next kernel to
+ * process. Each chunk holds bitmaps of the same order and each block of bitmaps
+ * starts at a given physical address. This allows the bitmaps to be sparse. The
+ * xarray is used to store them in a tree while building up the data structure,
+ * but the KHO successor kernel only needs to process them once in order.
+ *
+ * All of this memory is normal kmalloc() memory and is not marked for
+ * preservation. The successor kernel will remain isolated to the scratch space
+ * until it completes processing this list. Once processed all the memory
+ * storing these ranges will be marked as free.
+ */
+
+struct khoser_mem_bitmap_ptr {
+ phys_addr_t phys_start;
+ DECLARE_KHOSER_PTR(bitmap, struct kho_mem_phys_bits *);
+};
+
+struct khoser_mem_chunk_hdr {
+ DECLARE_KHOSER_PTR(next, struct khoser_mem_chunk *);
+ unsigned int order;
+ unsigned int num_elms;
+};
+
+#define KHOSER_BITMAP_SIZE \
+ ((PAGE_SIZE - sizeof(struct khoser_mem_chunk_hdr)) / \
+ sizeof(struct khoser_mem_bitmap_ptr))
+
+struct khoser_mem_chunk {
+ struct khoser_mem_chunk_hdr hdr;
+ struct khoser_mem_bitmap_ptr bitmaps[KHOSER_BITMAP_SIZE];
+};
+
+static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE);
+
+static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk,
+ unsigned long order)
+{
+ struct khoser_mem_chunk *chunk __free(free_page) = NULL;
+
+ chunk = (void *)get_zeroed_page(GFP_KERNEL);
+ if (!chunk)
+ return ERR_PTR(-ENOMEM);
+
+ if (WARN_ON(kho_scratch_overlap(virt_to_phys(chunk), PAGE_SIZE)))
+ return ERR_PTR(-EINVAL);
+
+ chunk->hdr.order = order;
+ if (cur_chunk)
+ KHOSER_STORE_PTR(cur_chunk->hdr.next, chunk);
+ return no_free_ptr(chunk);
+}
+
+static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
+{
+ struct khoser_mem_chunk *chunk = first_chunk;
+
+ while (chunk) {
+ struct khoser_mem_chunk *tmp = chunk;
+
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ kfree(tmp);
+ }
+}
+
+static int kho_mem_serialize(struct kho_out *kho_out)
+{
+ struct khoser_mem_chunk *first_chunk = NULL;
+ struct khoser_mem_chunk *chunk = NULL;
+ struct kho_mem_phys *physxa;
+ unsigned long order;
+ int err = -ENOMEM;
+
+ xa_for_each(&kho_out->track.orders, order, physxa) {
+ struct kho_mem_phys_bits *bits;
+ unsigned long phys;
+
+ chunk = new_chunk(chunk, order);
+ if (IS_ERR(chunk)) {
+ err = PTR_ERR(chunk);
+ goto err_free;
+ }
+
+ if (!first_chunk)
+ first_chunk = chunk;
+
+ xa_for_each(&physxa->phys_bits, phys, bits) {
+ struct khoser_mem_bitmap_ptr *elm;
+
+ if (chunk->hdr.num_elms == ARRAY_SIZE(chunk->bitmaps)) {
+ chunk = new_chunk(chunk, order);
+ if (IS_ERR(chunk)) {
+ err = PTR_ERR(chunk);
+ goto err_free;
+ }
+ }
+
+ elm = &chunk->bitmaps[chunk->hdr.num_elms];
+ chunk->hdr.num_elms++;
+ elm->phys_start = (phys * PRESERVE_BITS)
+ << (order + PAGE_SHIFT);
+ KHOSER_STORE_PTR(elm->bitmap, bits);
+ }
+ }
+
+ kho_out->preserved_mem_map = first_chunk;
+
+ return 0;
+
+err_free:
+ kho_mem_ser_free(first_chunk);
+ return err;
+}
+
+static void __init deserialize_bitmap(unsigned int order,
+ struct khoser_mem_bitmap_ptr *elm)
+{
+ struct kho_mem_phys_bits *bitmap = KHOSER_LOAD_PTR(elm->bitmap);
+ unsigned long bit;
+
+ for_each_set_bit(bit, bitmap->preserve, PRESERVE_BITS) {
+ int sz = 1 << (order + PAGE_SHIFT);
+ phys_addr_t phys =
+ elm->phys_start + (bit << (order + PAGE_SHIFT));
+ struct page *page = phys_to_page(phys);
+ union kho_page_info info;
+
+ memblock_reserve(phys, sz);
+ memblock_reserved_mark_noinit(phys, sz);
+ info.magic = KHO_PAGE_MAGIC;
+ info.order = order;
+ page->private = info.page_private;
+ }
+}
+
+static void __init kho_mem_deserialize(const void *fdt)
+{
+ struct khoser_mem_chunk *chunk;
+ const phys_addr_t *mem;
+ int len;
+
+ mem = fdt_getprop(fdt, 0, PROP_PRESERVED_MEMORY_MAP, &len);
+
+ if (!mem || len != sizeof(*mem)) {
+ pr_err("failed to get preserved memory bitmaps\n");
+ return;
+ }
+
+ chunk = *mem ? phys_to_virt(*mem) : NULL;
+ while (chunk) {
+ unsigned int i;
+
+ for (i = 0; i != chunk->hdr.num_elms; i++)
+ deserialize_bitmap(chunk->hdr.order,
+ &chunk->bitmaps[i]);
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ }
+}
+
+/*
+ * With KHO enabled, memory can become fragmented because KHO regions may
+ * be anywhere in physical address space. The scratch regions give us a
+ * safe zones that we will never see KHO allocations from. This is where we
+ * can later safely load our new kexec images into and then use the scratch
+ * area for early allocations that happen before page allocator is
+ * initialized.
+ */
+struct kho_scratch *kho_scratch;
+unsigned int kho_scratch_cnt;
+
+/*
+ * The scratch areas are scaled by default as percent of memory allocated from
+ * memblock. A user can override the scale with command line parameter:
+ *
+ * kho_scratch=N%
+ *
+ * It is also possible to explicitly define size for a lowmem, a global and
+ * per-node scratch areas:
+ *
+ * kho_scratch=l[KMG],n[KMG],m[KMG]
+ *
+ * The explicit size definition takes precedence over scale definition.
+ */
+static unsigned int scratch_scale __initdata = 200;
+static phys_addr_t scratch_size_global __initdata;
+static phys_addr_t scratch_size_pernode __initdata;
+static phys_addr_t scratch_size_lowmem __initdata;
+
+static int __init kho_parse_scratch_size(char *p)
+{
+ size_t len;
+ unsigned long sizes[3];
+ size_t total_size = 0;
+ int i;
+
+ if (!p)
+ return -EINVAL;
+
+ len = strlen(p);
+ if (!len)
+ return -EINVAL;
+
+ /* parse nn% */
+ if (p[len - 1] == '%') {
+ /* unsigned int max is 4,294,967,295, 10 chars */
+ char s_scale[11] = {};
+ int ret = 0;
+
+ if (len > ARRAY_SIZE(s_scale))
+ return -EINVAL;
+
+ memcpy(s_scale, p, len - 1);
+ ret = kstrtouint(s_scale, 10, &scratch_scale);
+ if (!ret)
+ pr_notice("scratch scale is %d%%\n", scratch_scale);
+ return ret;
+ }
+
+ /* parse ll[KMG],mm[KMG],nn[KMG] */
+ for (i = 0; i < ARRAY_SIZE(sizes); i++) {
+ char *endp = p;
+
+ if (i > 0) {
+ if (*p != ',')
+ return -EINVAL;
+ p += 1;
+ }
+
+ sizes[i] = memparse(p, &endp);
+ if (endp == p)
+ return -EINVAL;
+ p = endp;
+ total_size += sizes[i];
+ }
+
+ if (!total_size)
+ return -EINVAL;
+
+ /* The string should be fully consumed by now. */
+ if (*p)
+ return -EINVAL;
+
+ scratch_size_lowmem = sizes[0];
+ scratch_size_global = sizes[1];
+ scratch_size_pernode = sizes[2];
+ scratch_scale = 0;
+
+ pr_notice("scratch areas: lowmem: %lluMiB global: %lluMiB pernode: %lldMiB\n",
+ (u64)(scratch_size_lowmem >> 20),
+ (u64)(scratch_size_global >> 20),
+ (u64)(scratch_size_pernode >> 20));
+
+ return 0;
+}
+early_param("kho_scratch", kho_parse_scratch_size);
+
+static void __init scratch_size_update(void)
+{
+ phys_addr_t size;
+
+ if (!scratch_scale)
+ return;
+
+ size = memblock_reserved_kern_size(ARCH_LOW_ADDRESS_LIMIT,
+ NUMA_NO_NODE);
+ size = size * scratch_scale / 100;
+ scratch_size_lowmem = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+
+ size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+ NUMA_NO_NODE);
+ size = size * scratch_scale / 100 - scratch_size_lowmem;
+ scratch_size_global = round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+}
+
+static phys_addr_t __init scratch_size_node(int nid)
+{
+ phys_addr_t size;
+
+ if (scratch_scale) {
+ size = memblock_reserved_kern_size(MEMBLOCK_ALLOC_ANYWHERE,
+ nid);
+ size = size * scratch_scale / 100;
+ } else {
+ size = scratch_size_pernode;
+ }
+
+ return round_up(size, CMA_MIN_ALIGNMENT_BYTES);
+}
+
+/**
+ * kho_reserve_scratch - Reserve a contiguous chunk of memory for kexec
+ *
+ * With KHO we can preserve arbitrary pages in the system. To ensure we still
+ * have a large contiguous region of memory when we search the physical address
+ * space for target memory, let's make sure we always have a large CMA region
+ * active. This CMA region will only be used for movable pages which are not a
+ * problem for us during KHO because we can just move them somewhere else.
+ */
+static void __init kho_reserve_scratch(void)
+{
+ phys_addr_t addr, size;
+ int nid, i = 0;
+
+ if (!kho_enable)
+ return;
+
+ scratch_size_update();
+
+ /* FIXME: deal with node hot-plug/remove */
+ kho_scratch_cnt = num_online_nodes() + 2;
+ size = kho_scratch_cnt * sizeof(*kho_scratch);
+ kho_scratch = memblock_alloc(size, PAGE_SIZE);
+ if (!kho_scratch)
+ goto err_disable_kho;
+
+ /*
+ * reserve scratch area in low memory for lowmem allocations in the
+ * next kernel
+ */
+ size = scratch_size_lowmem;
+ addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0,
+ ARCH_LOW_ADDRESS_LIMIT);
+ if (!addr)
+ goto err_free_scratch_desc;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+
+ /* reserve large contiguous area for allocations without nid */
+ size = scratch_size_global;
+ addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES);
+ if (!addr)
+ goto err_free_scratch_areas;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+
+ for_each_online_node(nid) {
+ size = scratch_size_node(nid);
+ addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
+ 0, MEMBLOCK_ALLOC_ACCESSIBLE,
+ nid, true);
+ if (!addr)
+ goto err_free_scratch_areas;
+
+ kho_scratch[i].addr = addr;
+ kho_scratch[i].size = size;
+ i++;
+ }
+
+ return;
+
+err_free_scratch_areas:
+ for (i--; i >= 0; i--)
+ memblock_phys_free(kho_scratch[i].addr, kho_scratch[i].size);
+err_free_scratch_desc:
+ memblock_free(kho_scratch, kho_scratch_cnt * sizeof(*kho_scratch));
+err_disable_kho:
+ pr_warn("Failed to reserve scratch area, disabling kexec handover\n");
+ kho_enable = false;
+}
+
+/**
+ * kho_add_subtree - record the physical address of a sub FDT in KHO root tree.
+ * @name: name of the sub tree.
+ * @fdt: the sub tree blob.
+ *
+ * Creates a new child node named @name in KHO root FDT and records
+ * the physical address of @fdt. The pages of @fdt must also be preserved
+ * by KHO for the new kernel to retrieve it after kexec.
+ *
+ * A debugfs blob entry is also created at
+ * ``/sys/kernel/debug/kho/out/sub_fdts/@name`` when kernel is configured with
+ * CONFIG_KEXEC_HANDOVER_DEBUGFS
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_add_subtree(const char *name, void *fdt)
+{
+ struct kho_sub_fdt *sub_fdt;
+
+ sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL);
+ if (!sub_fdt)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&sub_fdt->l);
+ sub_fdt->name = name;
+ sub_fdt->fdt = fdt;
+
+ guard(mutex)(&kho_out.fdts_lock);
+ list_add_tail(&sub_fdt->l, &kho_out.sub_fdts);
+ WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false));
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_add_subtree);
+
+void kho_remove_subtree(void *fdt)
+{
+ struct kho_sub_fdt *sub_fdt;
+
+ guard(mutex)(&kho_out.fdts_lock);
+ list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) {
+ if (sub_fdt->fdt == fdt) {
+ list_del(&sub_fdt->l);
+ kfree(sub_fdt);
+ kho_debugfs_fdt_remove(&kho_out.dbg, fdt);
+ break;
+ }
+ }
+}
+EXPORT_SYMBOL_GPL(kho_remove_subtree);
+
+/**
+ * kho_preserve_folio - preserve a folio across kexec.
+ * @folio: folio to preserve.
+ *
+ * Instructs KHO to preserve the whole folio across kexec. The order
+ * will be preserved as well.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_folio(struct folio *folio)
+{
+ const unsigned long pfn = folio_pfn(folio);
+ const unsigned int order = folio_order(folio);
+ struct kho_mem_track *track = &kho_out.track;
+
+ if (WARN_ON(kho_scratch_overlap(pfn << PAGE_SHIFT, PAGE_SIZE << order)))
+ return -EINVAL;
+
+ return __kho_preserve_order(track, pfn, order);
+}
+EXPORT_SYMBOL_GPL(kho_preserve_folio);
+
+/**
+ * kho_unpreserve_folio - unpreserve a folio.
+ * @folio: folio to unpreserve.
+ *
+ * Instructs KHO to unpreserve a folio that was preserved by
+ * kho_preserve_folio() before. The provided @folio (pfn and order)
+ * must exactly match a previously preserved folio.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_folio(struct folio *folio)
+{
+ const unsigned long pfn = folio_pfn(folio);
+ const unsigned int order = folio_order(folio);
+ struct kho_mem_track *track = &kho_out.track;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve_order(track, pfn, order);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
+
+/**
+ * kho_preserve_pages - preserve contiguous pages across kexec
+ * @page: first page in the list.
+ * @nr_pages: number of pages.
+ *
+ * Preserve a contiguous list of order 0 pages. Must be restored using
+ * kho_restore_pages() to ensure the pages are restored properly as order 0.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_pages(struct page *page, unsigned int nr_pages)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ const unsigned long start_pfn = page_to_pfn(page);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+ unsigned long pfn = start_pfn;
+ unsigned long failed_pfn = 0;
+ int err = 0;
+
+ if (WARN_ON(kho_scratch_overlap(start_pfn << PAGE_SHIFT,
+ nr_pages << PAGE_SHIFT))) {
+ return -EINVAL;
+ }
+
+ while (pfn < end_pfn) {
+ const unsigned int order =
+ min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
+
+ err = __kho_preserve_order(track, pfn, order);
+ if (err) {
+ failed_pfn = pfn;
+ break;
+ }
+
+ pfn += 1 << order;
+ }
+
+ if (err)
+ __kho_unpreserve(track, start_pfn, failed_pfn);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(kho_preserve_pages);
+
+/**
+ * kho_unpreserve_pages - unpreserve contiguous pages.
+ * @page: first page in the list.
+ * @nr_pages: number of pages.
+ *
+ * Instructs KHO to unpreserve @nr_pages contiguous pages starting from @page.
+ * This must be called with the same @page and @nr_pages as the corresponding
+ * kho_preserve_pages() call. Unpreserving arbitrary sub-ranges of larger
+ * preserved blocks is not supported.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ const unsigned long start_pfn = page_to_pfn(page);
+ const unsigned long end_pfn = start_pfn + nr_pages;
+
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ __kho_unpreserve(track, start_pfn, end_pfn);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_pages);
+
+struct kho_vmalloc_hdr {
+ DECLARE_KHOSER_PTR(next, struct kho_vmalloc_chunk *);
+};
+
+#define KHO_VMALLOC_SIZE \
+ ((PAGE_SIZE - sizeof(struct kho_vmalloc_hdr)) / \
+ sizeof(phys_addr_t))
+
+struct kho_vmalloc_chunk {
+ struct kho_vmalloc_hdr hdr;
+ phys_addr_t phys[KHO_VMALLOC_SIZE];
+};
+
+static_assert(sizeof(struct kho_vmalloc_chunk) == PAGE_SIZE);
+
+/* vmalloc flags KHO supports */
+#define KHO_VMALLOC_SUPPORTED_FLAGS (VM_ALLOC | VM_ALLOW_HUGE_VMAP)
+
+/* KHO internal flags for vmalloc preservations */
+#define KHO_VMALLOC_ALLOC 0x0001
+#define KHO_VMALLOC_HUGE_VMAP 0x0002
+
+static unsigned short vmalloc_flags_to_kho(unsigned int vm_flags)
+{
+ unsigned short kho_flags = 0;
+
+ if (vm_flags & VM_ALLOC)
+ kho_flags |= KHO_VMALLOC_ALLOC;
+ if (vm_flags & VM_ALLOW_HUGE_VMAP)
+ kho_flags |= KHO_VMALLOC_HUGE_VMAP;
+
+ return kho_flags;
+}
+
+static unsigned int kho_flags_to_vmalloc(unsigned short kho_flags)
+{
+ unsigned int vm_flags = 0;
+
+ if (kho_flags & KHO_VMALLOC_ALLOC)
+ vm_flags |= VM_ALLOC;
+ if (kho_flags & KHO_VMALLOC_HUGE_VMAP)
+ vm_flags |= VM_ALLOW_HUGE_VMAP;
+
+ return vm_flags;
+}
+
+static struct kho_vmalloc_chunk *new_vmalloc_chunk(struct kho_vmalloc_chunk *cur)
+{
+ struct kho_vmalloc_chunk *chunk;
+ int err;
+
+ chunk = (struct kho_vmalloc_chunk *)get_zeroed_page(GFP_KERNEL);
+ if (!chunk)
+ return NULL;
+
+ err = kho_preserve_pages(virt_to_page(chunk), 1);
+ if (err)
+ goto err_free;
+ if (cur)
+ KHOSER_STORE_PTR(cur->hdr.next, chunk);
+ return chunk;
+
+err_free:
+ free_page((unsigned long)chunk);
+ return NULL;
+}
+
+static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk,
+ unsigned short order)
+{
+ struct kho_mem_track *track = &kho_out.track;
+ unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
+
+ __kho_unpreserve(track, pfn, pfn + 1);
+
+ for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
+ pfn = PHYS_PFN(chunk->phys[i]);
+ __kho_unpreserve(track, pfn, pfn + (1 << order));
+ }
+}
+
+static void kho_vmalloc_free_chunks(struct kho_vmalloc *kho_vmalloc)
+{
+ struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(kho_vmalloc->first);
+
+ while (chunk) {
+ struct kho_vmalloc_chunk *tmp = chunk;
+
+ kho_vmalloc_unpreserve_chunk(chunk, kho_vmalloc->order);
+
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ free_page((unsigned long)tmp);
+ }
+}
+
+/**
+ * kho_preserve_vmalloc - preserve memory allocated with vmalloc() across kexec
+ * @ptr: pointer to the area in vmalloc address space
+ * @preservation: placeholder for preservation metadata
+ *
+ * Instructs KHO to preserve the area in vmalloc address space at @ptr. The
+ * physical pages mapped at @ptr will be preserved and on successful return
+ * @preservation will hold the physical address of a structure that describes
+ * the preservation.
+ *
+ * NOTE: The memory allocated with vmalloc_node() variants cannot be reliably
+ * restored on the same node
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation)
+{
+ struct kho_vmalloc_chunk *chunk;
+ struct vm_struct *vm = find_vm_area(ptr);
+ unsigned int order, flags, nr_contig_pages;
+ unsigned int idx = 0;
+ int err;
+
+ if (!vm)
+ return -EINVAL;
+
+ if (vm->flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
+ return -EOPNOTSUPP;
+
+ flags = vmalloc_flags_to_kho(vm->flags);
+ order = get_vm_area_page_order(vm);
+
+ chunk = new_vmalloc_chunk(NULL);
+ if (!chunk)
+ return -ENOMEM;
+ KHOSER_STORE_PTR(preservation->first, chunk);
+
+ nr_contig_pages = (1 << order);
+ for (int i = 0; i < vm->nr_pages; i += nr_contig_pages) {
+ phys_addr_t phys = page_to_phys(vm->pages[i]);
+
+ err = kho_preserve_pages(vm->pages[i], nr_contig_pages);
+ if (err)
+ goto err_free;
+
+ chunk->phys[idx++] = phys;
+ if (idx == ARRAY_SIZE(chunk->phys)) {
+ chunk = new_vmalloc_chunk(chunk);
+ if (!chunk)
+ goto err_free;
+ idx = 0;
+ }
+ }
+
+ preservation->total_pages = vm->nr_pages;
+ preservation->flags = flags;
+ preservation->order = order;
+
+ return 0;
+
+err_free:
+ kho_vmalloc_free_chunks(preservation);
+ return err;
+}
+EXPORT_SYMBOL_GPL(kho_preserve_vmalloc);
+
+/**
+ * kho_unpreserve_vmalloc - unpreserve memory allocated with vmalloc()
+ * @preservation: preservation metadata returned by kho_preserve_vmalloc()
+ *
+ * Instructs KHO to unpreserve the area in vmalloc address space that was
+ * previously preserved with kho_preserve_vmalloc().
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_unpreserve_vmalloc(struct kho_vmalloc *preservation)
+{
+ if (kho_out.finalized)
+ return -EBUSY;
+
+ kho_vmalloc_free_chunks(preservation);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_unpreserve_vmalloc);
+
+/**
+ * kho_restore_vmalloc - recreates and populates an area in vmalloc address
+ * space from the preserved memory.
+ * @preservation: preservation metadata.
+ *
+ * Recreates an area in vmalloc address space and populates it with memory that
+ * was preserved using kho_preserve_vmalloc().
+ *
+ * Return: pointer to the area in the vmalloc address space, NULL on failure.
+ */
+void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
+{
+ struct kho_vmalloc_chunk *chunk = KHOSER_LOAD_PTR(preservation->first);
+ unsigned int align, order, shift, vm_flags;
+ unsigned long total_pages, contig_pages;
+ unsigned long addr, size;
+ struct vm_struct *area;
+ struct page **pages;
+ unsigned int idx = 0;
+ int err;
+
+ vm_flags = kho_flags_to_vmalloc(preservation->flags);
+ if (vm_flags & ~KHO_VMALLOC_SUPPORTED_FLAGS)
+ return NULL;
+
+ total_pages = preservation->total_pages;
+ pages = kvmalloc_array(total_pages, sizeof(*pages), GFP_KERNEL);
+ if (!pages)
+ return NULL;
+ order = preservation->order;
+ contig_pages = (1 << order);
+ shift = PAGE_SHIFT + order;
+ align = 1 << shift;
+
+ while (chunk) {
+ struct page *page;
+
+ for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
+ phys_addr_t phys = chunk->phys[i];
+
+ if (idx + contig_pages > total_pages)
+ goto err_free_pages_array;
+
+ page = kho_restore_pages(phys, contig_pages);
+ if (!page)
+ goto err_free_pages_array;
+
+ for (int j = 0; j < contig_pages; j++)
+ pages[idx++] = page;
+
+ phys += contig_pages * PAGE_SIZE;
+ }
+
+ page = kho_restore_pages(virt_to_phys(chunk), 1);
+ if (!page)
+ goto err_free_pages_array;
+ chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
+ __free_page(page);
+ }
+
+ if (idx != total_pages)
+ goto err_free_pages_array;
+
+ area = __get_vm_area_node(total_pages * PAGE_SIZE, align, shift,
+ vm_flags, VMALLOC_START, VMALLOC_END,
+ NUMA_NO_NODE, GFP_KERNEL,
+ __builtin_return_address(0));
+ if (!area)
+ goto err_free_pages_array;
+
+ addr = (unsigned long)area->addr;
+ size = get_vm_area_size(area);
+ err = vmap_pages_range(addr, addr + size, PAGE_KERNEL, pages, shift);
+ if (err)
+ goto err_free_vm_area;
+
+ area->nr_pages = total_pages;
+ area->pages = pages;
+
+ return area->addr;
+
+err_free_vm_area:
+ free_vm_area(area);
+err_free_pages_array:
+ kvfree(pages);
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
+
+static int __kho_abort(void)
+{
+ if (kho_out.preserved_mem_map) {
+ kho_mem_ser_free(kho_out.preserved_mem_map);
+ kho_out.preserved_mem_map = NULL;
+ }
+
+ return 0;
+}
+
+int kho_abort(void)
+{
+ int ret = 0;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ guard(mutex)(&kho_out.lock);
+ if (!kho_out.finalized)
+ return -ENOENT;
+
+ ret = __kho_abort();
+ if (ret)
+ return ret;
+
+ kho_out.finalized = false;
+
+ kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt);
+
+ return 0;
+}
+
+static int __kho_finalize(void)
+{
+ int err = 0;
+ u64 *preserved_mem_map;
+ void *root = kho_out.fdt;
+ struct kho_sub_fdt *fdt;
+
+ err |= fdt_create(root, PAGE_SIZE);
+ err |= fdt_finish_reservemap(root);
+ err |= fdt_begin_node(root, "");
+ err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE);
+ /**
+ * Reserve the preserved-memory-map property in the root FDT, so
+ * that all property definitions will precede subnodes created by
+ * KHO callers.
+ */
+ err |= fdt_property_placeholder(root, PROP_PRESERVED_MEMORY_MAP,
+ sizeof(*preserved_mem_map),
+ (void **)&preserved_mem_map);
+ if (err)
+ goto abort;
+
+ err = kho_preserve_folio(virt_to_folio(kho_out.fdt));
+ if (err)
+ goto abort;
+
+ err = kho_mem_serialize(&kho_out);
+ if (err)
+ goto abort;
+
+ *preserved_mem_map = (u64)virt_to_phys(kho_out.preserved_mem_map);
+
+ mutex_lock(&kho_out.fdts_lock);
+ list_for_each_entry(fdt, &kho_out.sub_fdts, l) {
+ phys_addr_t phys = virt_to_phys(fdt->fdt);
+
+ err |= fdt_begin_node(root, fdt->name);
+ err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys));
+ err |= fdt_end_node(root);
+ }
+ mutex_unlock(&kho_out.fdts_lock);
+
+ err |= fdt_end_node(root);
+ err |= fdt_finish(root);
+
+abort:
+ if (err) {
+ pr_err("Failed to convert KHO state tree: %d\n", err);
+ __kho_abort();
+ }
+
+ return err;
+}
+
+int kho_finalize(void)
+{
+ int ret;
+
+ if (!kho_enable)
+ return -EOPNOTSUPP;
+
+ guard(mutex)(&kho_out.lock);
+ if (kho_out.finalized)
+ return -EEXIST;
+
+ ret = __kho_finalize();
+ if (ret)
+ return ret;
+
+ kho_out.finalized = true;
+
+ WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, "fdt",
+ kho_out.fdt, true));
+
+ return 0;
+}
+
+bool kho_finalized(void)
+{
+ guard(mutex)(&kho_out.lock);
+ return kho_out.finalized;
+}
+
+struct kho_in {
+ phys_addr_t fdt_phys;
+ phys_addr_t scratch_phys;
+ struct kho_debugfs dbg;
+};
+
+static struct kho_in kho_in = {
+};
+
+static const void *kho_get_fdt(void)
+{
+ return kho_in.fdt_phys ? phys_to_virt(kho_in.fdt_phys) : NULL;
+}
+
+/**
+ * is_kho_boot - check if current kernel was booted via KHO-enabled
+ * kexec
+ *
+ * This function checks if the current kernel was loaded through a kexec
+ * operation with KHO enabled, by verifying that a valid KHO FDT
+ * was passed.
+ *
+ * Note: This function returns reliable results only after
+ * kho_populate() has been called during early boot. Before that,
+ * it may return false even if KHO data is present.
+ *
+ * Return: true if booted via KHO-enabled kexec, false otherwise
+ */
+bool is_kho_boot(void)
+{
+ return !!kho_get_fdt();
+}
+EXPORT_SYMBOL_GPL(is_kho_boot);
+
+/**
+ * kho_retrieve_subtree - retrieve a preserved sub FDT by its name.
+ * @name: the name of the sub FDT passed to kho_add_subtree().
+ * @phys: if found, the physical address of the sub FDT is stored in @phys.
+ *
+ * Retrieve a preserved sub FDT named @name and store its physical
+ * address in @phys.
+ *
+ * Return: 0 on success, error code on failure
+ */
+int kho_retrieve_subtree(const char *name, phys_addr_t *phys)
+{
+ const void *fdt = kho_get_fdt();
+ const u64 *val;
+ int offset, len;
+
+ if (!fdt)
+ return -ENOENT;
+
+ if (!phys)
+ return -EINVAL;
+
+ offset = fdt_subnode_offset(fdt, 0, name);
+ if (offset < 0)
+ return -ENOENT;
+
+ val = fdt_getprop(fdt, offset, PROP_SUB_FDT, &len);
+ if (!val || len != sizeof(*val))
+ return -EINVAL;
+
+ *phys = (phys_addr_t)*val;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kho_retrieve_subtree);
+
+static __init int kho_init(void)
+{
+ int err = 0;
+ const void *fdt = kho_get_fdt();
+ struct page *fdt_page;
+
+ if (!kho_enable)
+ return 0;
+
+ fdt_page = alloc_page(GFP_KERNEL);
+ if (!fdt_page) {
+ err = -ENOMEM;
+ goto err_free_scratch;
+ }
+ kho_out.fdt = page_to_virt(fdt_page);
+
+ err = kho_debugfs_init();
+ if (err)
+ goto err_free_fdt;
+
+ err = kho_out_debugfs_init(&kho_out.dbg);
+ if (err)
+ goto err_free_fdt;
+
+ if (fdt) {
+ kho_in_debugfs_init(&kho_in.dbg, fdt);
+ return 0;
+ }
+
+ for (int i = 0; i < kho_scratch_cnt; i++) {
+ unsigned long base_pfn = PHYS_PFN(kho_scratch[i].addr);
+ unsigned long count = kho_scratch[i].size >> PAGE_SHIFT;
+ unsigned long pfn;
+
+ for (pfn = base_pfn; pfn < base_pfn + count;
+ pfn += pageblock_nr_pages)
+ init_cma_reserved_pageblock(pfn_to_page(pfn));
+ }
+
+ return 0;
+
+err_free_fdt:
+ put_page(fdt_page);
+ kho_out.fdt = NULL;
+err_free_scratch:
+ for (int i = 0; i < kho_scratch_cnt; i++) {
+ void *start = __va(kho_scratch[i].addr);
+ void *end = start + kho_scratch[i].size;
+
+ free_reserved_area(start, end, -1, "");
+ }
+ kho_enable = false;
+ return err;
+}
+fs_initcall(kho_init);
+
+static void __init kho_release_scratch(void)
+{
+ phys_addr_t start, end;
+ u64 i;
+
+ memmap_init_kho_scratch_pages();
+
+ /*
+ * Mark scratch mem as CMA before we return it. That way we
+ * ensure that no kernel allocations happen on it. That means
+ * we can reuse it as scratch memory again later.
+ */
+ __for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,
+ MEMBLOCK_KHO_SCRATCH, &start, &end, NULL) {
+ ulong start_pfn = pageblock_start_pfn(PFN_DOWN(start));
+ ulong end_pfn = pageblock_align(PFN_UP(end));
+ ulong pfn;
+
+ for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages)
+ init_pageblock_migratetype(pfn_to_page(pfn),
+ MIGRATE_CMA, false);
+ }
+}
+
+void __init kho_memory_init(void)
+{
+ struct folio *folio;
+
+ if (kho_in.scratch_phys) {
+ kho_scratch = phys_to_virt(kho_in.scratch_phys);
+ kho_release_scratch();
+
+ kho_mem_deserialize(kho_get_fdt());
+ folio = kho_restore_folio(kho_in.fdt_phys);
+ if (!folio)
+ pr_warn("failed to restore folio for KHO fdt\n");
+ } else {
+ kho_reserve_scratch();
+ }
+}
+
+void __init kho_populate(phys_addr_t fdt_phys, u64 fdt_len,
+ phys_addr_t scratch_phys, u64 scratch_len)
+{
+ void *fdt = NULL;
+ struct kho_scratch *scratch = NULL;
+ int err = 0;
+ unsigned int scratch_cnt = scratch_len / sizeof(*kho_scratch);
+
+ /* Validate the input FDT */
+ fdt = early_memremap(fdt_phys, fdt_len);
+ if (!fdt) {
+ pr_warn("setup: failed to memremap FDT (0x%llx)\n", fdt_phys);
+ err = -EFAULT;
+ goto out;
+ }
+ err = fdt_check_header(fdt);
+ if (err) {
+ pr_warn("setup: handover FDT (0x%llx) is invalid: %d\n",
+ fdt_phys, err);
+ err = -EINVAL;
+ goto out;
+ }
+ err = fdt_node_check_compatible(fdt, 0, KHO_FDT_COMPATIBLE);
+ if (err) {
+ pr_warn("setup: handover FDT (0x%llx) is incompatible with '%s': %d\n",
+ fdt_phys, KHO_FDT_COMPATIBLE, err);
+ err = -EINVAL;
+ goto out;
+ }
+
+ scratch = early_memremap(scratch_phys, scratch_len);
+ if (!scratch) {
+ pr_warn("setup: failed to memremap scratch (phys=0x%llx, len=%lld)\n",
+ scratch_phys, scratch_len);
+ err = -EFAULT;
+ goto out;
+ }
+
+ /*
+ * We pass a safe contiguous blocks of memory to use for early boot
+ * purporses from the previous kernel so that we can resize the
+ * memblock array as needed.
+ */
+ for (int i = 0; i < scratch_cnt; i++) {
+ struct kho_scratch *area = &scratch[i];
+ u64 size = area->size;
+
+ memblock_add(area->addr, size);
+ err = memblock_mark_kho_scratch(area->addr, size);
+ if (WARN_ON(err)) {
+ pr_warn("failed to mark the scratch region 0x%pa+0x%pa: %d",
+ &area->addr, &size, err);
+ goto out;
+ }
+ pr_debug("Marked 0x%pa+0x%pa as scratch", &area->addr, &size);
+ }
+
+ memblock_reserve(scratch_phys, scratch_len);
+
+ /*
+ * Now that we have a viable region of scratch memory, let's tell
+ * the memblocks allocator to only use that for any allocations.
+ * That way we ensure that nothing scribbles over in use data while
+ * we initialize the page tables which we will need to ingest all
+ * memory reservations from the previous kernel.
+ */
+ memblock_set_kho_scratch_only();
+
+ kho_in.fdt_phys = fdt_phys;
+ kho_in.scratch_phys = scratch_phys;
+ kho_scratch_cnt = scratch_cnt;
+ pr_info("found kexec handover data. Will skip init for some devices\n");
+
+out:
+ if (fdt)
+ early_memunmap(fdt, fdt_len);
+ if (scratch)
+ early_memunmap(scratch, scratch_len);
+ if (err)
+ pr_warn("disabling KHO revival: %d\n", err);
+}
+
+/* Helper functions for kexec_file_load */
+
+int kho_fill_kimage(struct kimage *image)
+{
+ ssize_t scratch_size;
+ int err = 0;
+ struct kexec_buf scratch;
+
+ if (!kho_out.finalized)
+ return 0;
+
+ image->kho.fdt = virt_to_phys(kho_out.fdt);
+
+ scratch_size = sizeof(*kho_scratch) * kho_scratch_cnt;
+ scratch = (struct kexec_buf){
+ .image = image,
+ .buffer = kho_scratch,
+ .bufsz = scratch_size,
+ .mem = KEXEC_BUF_MEM_UNKNOWN,
+ .memsz = scratch_size,
+ .buf_align = SZ_64K, /* Makes it easier to map */
+ .buf_max = ULONG_MAX,
+ .top_down = true,
+ };
+ err = kexec_add_buffer(&scratch);
+ if (err)
+ return err;
+ image->kho.scratch = &image->segment[image->nr_segments - 1];
+
+ return 0;
+}
+
+static int kho_walk_scratch(struct kexec_buf *kbuf,
+ int (*func)(struct resource *, void *))
+{
+ int ret = 0;
+ int i;
+
+ for (i = 0; i < kho_scratch_cnt; i++) {
+ struct resource res = {
+ .start = kho_scratch[i].addr,
+ .end = kho_scratch[i].addr + kho_scratch[i].size - 1,
+ };
+
+ /* Try to fit the kimage into our KHO scratch region */
+ ret = func(&res, kbuf);
+ if (ret)
+ break;
+ }
+
+ return ret;
+}
+
+int kho_locate_mem_hole(struct kexec_buf *kbuf,
+ int (*func)(struct resource *, void *))
+{
+ int ret;
+
+ if (!kho_enable || kbuf->image->type == KEXEC_TYPE_CRASH)
+ return 1;
+
+ ret = kho_walk_scratch(kbuf, func);
+
+ return ret == 1 ? 0 : -EADDRNOTAVAIL;
+}
diff --git a/kernel/liveupdate/kexec_handover_debug.c a/kernel/liveupdate/kexec_handover_debug.c
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_debug.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover_debug.c - kexec handover optional debug functionality
+ * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include "kexec_handover_internal.h"
+
+bool kho_scratch_overlap(phys_addr_t phys, size_t size)
+{
+ phys_addr_t scratch_start, scratch_end;
+ unsigned int i;
+
+ for (i = 0; i < kho_scratch_cnt; i++) {
+ scratch_start = kho_scratch[i].addr;
+ scratch_end = kho_scratch[i].addr + kho_scratch[i].size;
+
+ if (phys < scratch_end && (phys + size) > scratch_start)
+ return true;
+ }
+
+ return false;
+}
diff --git a/kernel/liveupdate/kexec_handover_debugfs.c a/kernel/liveupdate/kexec_handover_debugfs.c
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_debugfs.c
@@ -0,0 +1,219 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover_debugfs.c - kexec handover debugfs interfaces
+ * Copyright (C) 2023 Alexander Graf <graf@amazon.com>
+ * Copyright (C) 2025 Microsoft Corporation, Mike Rapoport <rppt@kernel.org>
+ * Copyright (C) 2025 Google LLC, Changyuan Lyu <changyuanl@google.com>
+ * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/libfdt.h>
+#include <linux/mm.h>
+#include "kexec_handover_internal.h"
+
+static struct dentry *debugfs_root;
+
+struct fdt_debugfs {
+ struct list_head list;
+ struct debugfs_blob_wrapper wrapper;
+ struct dentry *file;
+};
+
+static int __kho_debugfs_fdt_add(struct list_head *list, struct dentry *dir,
+ const char *name, const void *fdt)
+{
+ struct fdt_debugfs *f;
+ struct dentry *file;
+
+ f = kmalloc(sizeof(*f), GFP_KERNEL);
+ if (!f)
+ return -ENOMEM;
+
+ f->wrapper.data = (void *)fdt;
+ f->wrapper.size = fdt_totalsize(fdt);
+
+ file = debugfs_create_blob(name, 0400, dir, &f->wrapper);
+ if (IS_ERR(file)) {
+ kfree(f);
+ return PTR_ERR(file);
+ }
+
+ f->file = file;
+ list_add(&f->list, list);
+
+ return 0;
+}
+
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root)
+{
+ struct dentry *dir;
+
+ if (root)
+ dir = dbg->dir;
+ else
+ dir = dbg->sub_fdt_dir;
+
+ return __kho_debugfs_fdt_add(&dbg->fdt_list, dir, name, fdt);
+}
+
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt)
+{
+ struct fdt_debugfs *ff;
+
+ list_for_each_entry(ff, &dbg->fdt_list, list) {
+ if (ff->wrapper.data == fdt) {
+ debugfs_remove(ff->file);
+ list_del(&ff->list);
+ kfree(ff);
+ break;
+ }
+ }
+}
+
+static int kho_out_finalize_get(void *data, u64 *val)
+{
+ *val = kho_finalized();
+
+ return 0;
+}
+
+static int kho_out_finalize_set(void *data, u64 val)
+{
+ if (val)
+ return kho_finalize();
+ else
+ return kho_abort();
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
+ kho_out_finalize_set, "%llu\n");
+
+static int scratch_phys_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].addr);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_phys);
+
+static int scratch_len_show(struct seq_file *m, void *v)
+{
+ for (int i = 0; i < kho_scratch_cnt; i++)
+ seq_printf(m, "0x%llx\n", kho_scratch[i].size);
+
+ return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(scratch_len);
+
+__init void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt)
+{
+ struct dentry *dir, *sub_fdt_dir;
+ int err, child;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("in", debugfs_root);
+ if (IS_ERR(dir)) {
+ err = PTR_ERR(dir);
+ goto err_out;
+ }
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir)) {
+ err = PTR_ERR(sub_fdt_dir);
+ goto err_rmdir;
+ }
+
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, dir, "fdt", fdt);
+ if (err)
+ goto err_rmdir;
+
+ fdt_for_each_subnode(child, fdt, 0) {
+ int len = 0;
+ const char *name = fdt_get_name(fdt, child, NULL);
+ const u64 *fdt_phys;
+
+ fdt_phys = fdt_getprop(fdt, child, "fdt", &len);
+ if (!fdt_phys)
+ continue;
+ if (len != sizeof(*fdt_phys)) {
+ pr_warn("node %s prop fdt has invalid length: %d\n",
+ name, len);
+ continue;
+ }
+ err = __kho_debugfs_fdt_add(&dbg->fdt_list, sub_fdt_dir, name,
+ phys_to_virt(*fdt_phys));
+ if (err) {
+ pr_warn("failed to add fdt %s to debugfs: %d\n", name,
+ err);
+ continue;
+ }
+ }
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+
+ return;
+err_rmdir:
+ debugfs_remove_recursive(dir);
+err_out:
+ /*
+ * Failure to create /sys/kernel/debug/kho/in does not prevent
+ * reviving state from KHO and setting up KHO for the next
+ * kexec.
+ */
+ if (err)
+ pr_err("failed exposing handover FDT in debugfs: %d\n", err);
+}
+
+__init int kho_out_debugfs_init(struct kho_debugfs *dbg)
+{
+ struct dentry *dir, *f, *sub_fdt_dir;
+
+ INIT_LIST_HEAD(&dbg->fdt_list);
+
+ dir = debugfs_create_dir("out", debugfs_root);
+ if (IS_ERR(dir))
+ return -ENOMEM;
+
+ sub_fdt_dir = debugfs_create_dir("sub_fdts", dir);
+ if (IS_ERR(sub_fdt_dir))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_phys", 0400, dir, NULL,
+ &scratch_phys_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("scratch_len", 0400, dir, NULL,
+ &scratch_len_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ f = debugfs_create_file("finalize", 0600, dir, NULL,
+ &kho_out_finalize_fops);
+ if (IS_ERR(f))
+ goto err_rmdir;
+
+ dbg->dir = dir;
+ dbg->sub_fdt_dir = sub_fdt_dir;
+ return 0;
+
+err_rmdir:
+ debugfs_remove_recursive(dir);
+ return -ENOENT;
+}
+
+__init int kho_debugfs_init(void)
+{
+ debugfs_root = debugfs_create_dir("kho", NULL);
+ if (IS_ERR(debugfs_root))
+ return -ENOENT;
+ return 0;
+}
diff --git a/kernel/liveupdate/kexec_handover_internal.h a/kernel/liveupdate/kexec_handover_internal.h
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/kexec_handover_internal.h
@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
+#define LINUX_KEXEC_HANDOVER_INTERNAL_H
+
+#include <linux/kexec_handover.h>
+#include <linux/list.h>
+#include <linux/types.h>
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
+#include <linux/debugfs.h>
+
+struct kho_debugfs {
+ struct dentry *dir;
+ struct dentry *sub_fdt_dir;
+ struct list_head fdt_list;
+};
+
+#else
+struct kho_debugfs {};
+#endif
+
+extern struct kho_scratch *kho_scratch;
+extern unsigned int kho_scratch_cnt;
+
+bool kho_finalized(void);
+int kho_finalize(void);
+int kho_abort(void);
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
+int kho_debugfs_init(void);
+void kho_in_debugfs_init(struct kho_debugfs *dbg, const void *fdt);
+int kho_out_debugfs_init(struct kho_debugfs *dbg);
+int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root);
+void kho_debugfs_fdt_remove(struct kho_debugfs *dbg, void *fdt);
+#else
+static inline int kho_debugfs_init(void) { return 0; }
+static inline void kho_in_debugfs_init(struct kho_debugfs *dbg,
+ const void *fdt) { }
+static inline int kho_out_debugfs_init(struct kho_debugfs *dbg) { return 0; }
+static inline int kho_debugfs_fdt_add(struct kho_debugfs *dbg, const char *name,
+ const void *fdt, bool root) { return 0; }
+static inline void kho_debugfs_fdt_remove(struct kho_debugfs *dbg,
+ void *fdt) { }
+#endif /* CONFIG_KEXEC_HANDOVER_DEBUGFS */
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
+bool kho_scratch_overlap(phys_addr_t phys, size_t size);
+#else
+static inline bool kho_scratch_overlap(phys_addr_t phys, size_t size)
+{
+ return false;
+}
+#endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
+
+#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */
diff --git a/kernel/liveupdate/Makefile a/kernel/liveupdate/Makefile
new file mode 100644
--- /dev/null
+++ a/kernel/liveupdate/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS) += kexec_handover_debugfs.o
--- a/kernel/Makefile~liveupdate-kho-move-to-kernel-liveupdate
+++ a/kernel/Makefile
@@ -52,6 +52,7 @@ obj-y += printk/
obj-y += irq/
obj-y += rcu/
obj-y += livepatch/
+obj-y += liveupdate/
obj-y += dma/
obj-y += entry/
obj-y += unwind/
@@ -82,9 +83,6 @@ obj-$(CONFIG_CRASH_DUMP_KUNIT_TEST) += c
obj-$(CONFIG_KEXEC) += kexec.o
obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
-obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
-obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
-obj-$(CONFIG_KEXEC_HANDOVER_DEBUGFS) += kexec_handover_debugfs.o
obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
obj-$(CONFIG_COMPAT) += compat.o
obj-$(CONFIG_CGROUPS) += cgroup/
--- a/MAINTAINERS~liveupdate-kho-move-to-kernel-liveupdate
+++ a/MAINTAINERS
@@ -13796,7 +13796,7 @@ S: Maintained
F: Documentation/admin-guide/mm/kho.rst
F: Documentation/core-api/kho/*
F: include/linux/kexec_handover.h
-F: kernel/kexec_handover*
+F: kernel/liveupdate/kexec_handover*
F: tools/testing/selftests/kho/
KEYS-ENCRYPTED
_
Patches currently in -mm which might be from pasha.tatashin@soleen.com are
liveupdate-kho-warn-and-fail-on-metadata-or-preserved-memory-in-scratch-area.patch
liveupdate-kho-increase-metadata-bitmap-size-to-page_size.patch
liveupdate-kho-allocate-metadata-directly-from-the-buddy-allocator.patch
kho-make-debugfs-interface-optional.patch
kho-add-interfaces-to-unpreserve-folios-page-ranges-and-vmalloc.patch
memblock-unpreserve-memory-in-case-of-error.patch
test_kho-unpreserve-memory-in-case-of-error.patch
kho-dont-unpreserve-memory-during-abort.patch
liveupdate-kho-move-to-kernel-liveupdate.patch
maintainers-update-kho-maintainers.patch
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2025-11-04 3:26 + liveupdate-kho-move-to-kernel-liveupdate.patch added to mm-nonmm-unstable branch Andrew Morton
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2025-10-26 4:06 Andrew Morton
2025-10-09 2:15 Andrew Morton
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