KHO currently restricts the maximum order of a restored page to the
maximum order supported by the buddy allocator. While this works fine for
much of the data passed across kexec, it is possible to have pages larger
than MAX_PAGE_ORDER.
For one, it is possible to get a larger order when using
kho_preserve_pages() if the number of pages is large enough, since it
tries to combine multiple aligned 0-order preservations into one higher
order preservation.
For another, upcoming support for hugepages can have gigantic hugepages
being preserved over KHO.
There is no real reason for this limit. The KHO preservation machinery
can handle any page order. Remove this artificial restriction on max page
order.
Link: https://lkml.kernel.org/r/20260309123410.382308-2-pratyush@kernel.org
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The KHO restoration machinery is not capable of dealing with preservations
that span multiple NUMA nodes. kho_preserve_folio() guarantees the
preservation will only span one NUMA node since folios can't span multiple
nodes.
This leaves kho_preserve_pages(). While semantically kho_preserve_pages()
only deals with 0-order pages, so all preservations should be single page
only, in practice it combines preservations to higher orders for
efficiency. This can result in a preservation spanning multiple nodes.
Break up the preservations into a smaller order if that happens.
Link: https://lkml.kernel.org/r/20260309123410.382308-1-pratyush@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Make KHO Stateless", v9.
This series transitions KHO from an xarray-based metadata tracking system
with serialization to a radix tree data structure that can be passed
directly to the next kernel.
The key motivations for this change are to:
- Eliminate the need for data serialization before kexec.
- Remove the KHO finalize state.
- Pass preservation metadata more directly to the next kernel via the FDT.
The new approach uses a radix tree to mark preserved pages. A page's
physical address and its order are encoded into a single value. The tree
is composed of multiple levels of page-sized tables, with leaf nodes being
bitmaps where each set bit represents a preserved page. The physical
address of the radix tree's root is passed in the FDT, allowing the next
kernel to reconstruct the preserved memory map.
This series is broken down into the following patches:
1. kho: Adopt radix tree for preserved memory tracking:
Replaces the xarray-based tracker with the new radix tree
implementation and increments the ABI version.
2. kho: Remove finalize state and clients:
Removes the now-obsolete kho_finalize() function and its usage
from client code and debugfs.
This patch (of 2):
Introduce a radix tree implementation for tracking preserved memory pages
and switch the KHO memory tracking mechanism to use it. This lays the
groundwork for a stateless KHO implementation that eliminates the need for
serialization and the associated "finalize" state.
This patch introduces the core radix tree data structures and constants to
the KHO ABI. It adds the radix tree node and leaf structures, along with
documentation for the radix tree key encoding scheme that combines a
page's physical address and order.
To support broader use by other kernel subsystems, such as hugetlb
preservation, the core radix tree manipulation functions are exported as a
public API.
The xarray-based memory tracking is replaced with this new radix tree
implementation. The core KHO preservation and unpreservation functions
are wired up to use the radix tree helpers. On boot, the second kernel
restores the preserved memory map by walking the radix tree whose root
physical address is passed via the FDT.
The ABI `compatible` version is bumped to "kho-v2" to reflect the
structural changes in the preserved memory map and sub-FDT property names.
This includes renaming "fdt" to "preserved-data" to better reflect that
preserved state may use formats other than FDT.
[ran.xiaokai@zte.com.cn: fix child node parsing for debugfs in/sub_fdts]
Link: https://lkml.kernel.org/r/20260309033530.244508-1-ranxiaokai627@163.com
Link: https://lkml.kernel.org/r/20260206021428.3386442-1-jasonmiu@google.com
Link: https://lkml.kernel.org/r/20260206021428.3386442-2-jasonmiu@google.com
Signed-off-by: Jason Miu <jasonmiu@google.com>
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit 8f1081892d ("kho: simplify page initialization in
kho_restore_page()") cleaned up the page initialization logic by moving
the folio and 0-order-page paths into separate functions. It missed
moving the alloc tag initialization.
Do it now to keep the two paths cleanly separated. While at it, touch up
the comments to be a tiny bit shorter (mainly so it doesn't end up
splitting into a multiline comment). This is purely a cosmetic change and
there should be no change in behaviour.
Link: https://lkml.kernel.org/r/20260213085914.2778107-1-pratyush@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
LUO keeps track of successful retrieve attempts on a LUO file. It does so
to avoid multiple retrievals of the same file. Multiple retrievals cause
problems because once the file is retrieved, the serialized data
structures are likely freed and the file is likely in a very different
state from what the code expects.
The retrieve boolean in struct luo_file keeps track of this, and is passed
to the finish callback so it knows what work was already done and what it
has left to do.
All this works well when retrieve succeeds. When it fails,
luo_retrieve_file() returns the error immediately, without ever storing
anywhere that a retrieve was attempted or what its error code was. This
results in an errored LIVEUPDATE_SESSION_RETRIEVE_FD ioctl to userspace,
but nothing prevents it from trying this again.
The retry is problematic for much of the same reasons listed above. The
file is likely in a very different state than what the retrieve logic
normally expects, and it might even have freed some serialization data
structures. Attempting to access them or free them again is going to
break things.
For example, if memfd managed to restore 8 of its 10 folios, but fails on
the 9th, a subsequent retrieve attempt will try to call
kho_restore_folio() on the first folio again, and that will fail with a
warning since it is an invalid operation.
Apart from the retry, finish() also breaks. Since on failure the
retrieved bool in luo_file is never touched, the finish() call on session
close will tell the file handler that retrieve was never attempted, and it
will try to access or free the data structures that might not exist, much
in the same way as the retry attempt.
There is no sane way of attempting the retrieve again. Remember the error
retrieve returned and directly return it on a retry. Also pass this
status code to finish() so it can make the right decision on the work it
needs to do.
This is done by changing the bool to an integer. A value of 0 means
retrieve was never attempted, a positive value means it succeeded, and a
negative value means it failed and the error code is the value.
Link: https://lkml.kernel.org/r/20260216132221.987987-1-pratyush@kernel.org
Fixes: 7c722a7f44 ("liveupdate: luo_file: implement file systems callbacks")
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This was done entirely with mindless brute force, using
git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'
to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.
Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.
For the same reason the 'flex' versions will be done as a separate
conversion.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
Pull more non-MM updates from Andrew Morton:
- "two fixes in kho_populate()" fixes a couple of not-major issues in
the kexec handover code (Ran Xiaokai)
- misc singletons
* tag 'mm-nonmm-stable-2026-02-18-19-56' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
lib/group_cpus: handle const qualifier from clusters allocation type
kho: remove unnecessary WARN_ON(err) in kho_populate()
kho: fix missing early_memunmap() call in kho_populate()
scripts/gdb: implement x86_page_ops in mm.py
objpool: fix the overestimation of object pooling metadata size
selftests/memfd: use IPC semaphore instead of SIGSTOP/SIGCONT
delayacct: fix build regression on accounting tool
Pull non-MM updates from Andrew Morton:
- "ocfs2: give ocfs2 the ability to reclaim suballocator free bg" saves
disk space by teaching ocfs2 to reclaim suballocator block group
space (Heming Zhao)
- "Add ARRAY_END(), and use it to fix off-by-one bugs" adds the
ARRAY_END() macro and uses it in various places (Alejandro Colomar)
- "vmcoreinfo: support VMCOREINFO_BYTES larger than PAGE_SIZE" makes
the vmcore code future-safe, if VMCOREINFO_BYTES ever exceeds the
page size (Pnina Feder)
- "kallsyms: Prevent invalid access when showing module buildid" cleans
up kallsyms code related to module buildid and fixes an invalid
access crash when printing backtraces (Petr Mladek)
- "Address page fault in ima_restore_measurement_list()" fixes a
kexec-related crash that can occur when booting the second-stage
kernel on x86 (Harshit Mogalapalli)
- "kho: ABI headers and Documentation updates" updates the kexec
handover ABI documentation (Mike Rapoport)
- "Align atomic storage" adds the __aligned attribute to atomic_t and
atomic64_t definitions to get natural alignment of both types on
csky, m68k, microblaze, nios2, openrisc and sh (Finn Thain)
- "kho: clean up page initialization logic" simplifies the page
initialization logic in kho_restore_page() (Pratyush Yadav)
- "Unload linux/kernel.h" moves several things out of kernel.h and into
more appropriate places (Yury Norov)
- "don't abuse task_struct.group_leader" removes the usage of
->group_leader when it is "obviously unnecessary" (Oleg Nesterov)
- "list private v2 & luo flb" adds some infrastructure improvements to
the live update orchestrator (Pasha Tatashin)
* tag 'mm-nonmm-stable-2026-02-12-10-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (107 commits)
watchdog/hardlockup: simplify perf event probe and remove per-cpu dependency
procfs: fix missing RCU protection when reading real_parent in do_task_stat()
watchdog/softlockup: fix sample ring index wrap in need_counting_irqs()
kcsan, compiler_types: avoid duplicate type issues in BPF Type Format
kho: fix doc for kho_restore_pages()
tests/liveupdate: add in-kernel liveupdate test
liveupdate: luo_flb: introduce File-Lifecycle-Bound global state
liveupdate: luo_file: Use private list
list: add kunit test for private list primitives
list: add primitives for private list manipulations
delayacct: fix uapi timespec64 definition
panic: add panic_force_cpu= parameter to redirect panic to a specific CPU
netclassid: use thread_group_leader(p) in update_classid_task()
RDMA/umem: don't abuse current->group_leader
drm/pan*: don't abuse current->group_leader
drm/amd: kill the outdated "Only the pthreads threading model is supported" checks
drm/amdgpu: don't abuse current->group_leader
android/binder: use same_thread_group(proc->tsk, current) in binder_mmap()
android/binder: don't abuse current->group_leader
kho: skip memoryless NUMA nodes when reserving scratch areas
...
Introduce a mechanism for managing global kernel state whose lifecycle is
tied to the preservation of one or more files. This is necessary for
subsystems where multiple preserved file descriptors depend on a single,
shared underlying resource.
An example is HugeTLB, where multiple file descriptors such as memfd and
guest_memfd may rely on the state of a single HugeTLB subsystem.
Preserving this state for each individual file would be redundant and
incorrect. The state should be preserved only once when the first file is
preserved, and restored/finished only once the last file is handled.
This patch introduces File-Lifecycle-Bound (FLB) objects to solve this
problem. An FLB is a global, reference-counted object with a defined set
of operations:
- A file handler (struct liveupdate_file_handler) declares a dependency
on one or more FLBs via a new registration function,
liveupdate_register_flb().
- When the first file depending on an FLB is preserved, the FLB's
.preserve() callback is invoked to save the shared global state. The
reference count is then incremented for each subsequent file.
- Conversely, when the last file is unpreserved (before reboot) or
finished (after reboot), the FLB's .unpreserve() or .finish() callback
is invoked to clean up the global resource.
The implementation includes:
- A new set of ABI definitions (luo_flb_ser, luo_flb_head_ser) and a
corresponding FDT node (luo-flb) to serialize the state of all active
FLBs and pass them via Kexec Handover.
- Core logic in luo_flb.c to manage FLB registration, reference
counting, and the invocation of lifecycle callbacks.
- An API (liveupdate_flb_get/_incoming/_outgoing) for other kernel
subsystems to safely access the live object managed by an FLB, both
before and after the live update.
This framework provides the necessary infrastructure for more complex
subsystems like IOMMU, VFIO, and KVM to integrate with the Live Update
Orchestrator.
Link: https://lkml.kernel.org/r/20251218155752.3045808-5-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Gow <davidgow@google.com>
Cc: David Matlack <dmatlack@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Cc: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "liveupdate: fixes in error handling".
This series contains some fixes in LUO's error handling paths.
The first patch deals with failed freeze() attempts. The cleanup path
calls unfreeze, and that clears some data needed by later unpreserve
calls.
The second patch is a bit more involved. It deals with failed retrieve()
attempts. To do so properly, it reworks some of the error handling logic
in luo_file core.
Both these fixes are "theoretical" -- in the sense that I have not been
able to reproduce either of them in normal operation. The only supported
file type right now is memfd, and there is nothing userspace can do right
now to make it fail its retrieve or freeze. I need to make the retrieve
or freeze fail by artificially injecting errors. The injected errors
trigger a use-after-free and a double-free.
That said, once more complex file handlers are added or memfd preservation
is used in ways not currently expected or covered by the tests, we will be
able to see them on real systems.
This patch (of 2):
The unfreeze operation is supposed to undo the effects of the freeze
operation. serialized_data is not set by freeze, but by preserve.
Consequently, the unpreserve operation needs to access serialized_data to
undo the effects of the preserve operation. This includes freeing the
serialized data structures for example.
If a freeze callback fails, unfreeze is called for all frozen files. This
would clear serialized_data for them. Since live update has failed, it
can be expected that userspace aborts, releasing all sessions. When the
sessions are released, unpreserve will be called for all files. The
unfrozen files will see 0 in their serialized_data. This is not expected
by file handlers, and they might either fail, leaking data and state, or
might even crash or cause invalid memory access.
Do not clear serialized_data on unfreeze so it gets passed on to
unpreserve. There is no need to clear it on unpreserve since luo_file
will be freed immediately after.
Link: https://lkml.kernel.org/r/20260126230302.2936817-1-pratyush@kernel.org
Link: https://lkml.kernel.org/r/20260126230302.2936817-2-pratyush@kernel.org
Fixes: 7c722a7f44 ("liveupdate: luo_file: implement file systems callbacks")
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
kho_reserve_scratch() iterates over all online NUMA nodes to allocate
per-node scratch memory. On systems with memoryless NUMA nodes (nodes
that have CPUs but no memory), memblock_alloc_range_nid() fails because
there is no memory available on that node. This causes KHO initialization
to fail and kho_enable to be set to false.
Some ARM64 systems have NUMA topologies where certain nodes contain only
CPUs without any associated memory. These configurations are valid and
should not prevent KHO from functioning.
Fix this by only counting nodes that have memory (N_MEMORY state) and skip
memoryless nodes in the per-node scratch allocation loop.
Link: https://lkml.kernel.org/r/20260120175913.34368-1-epetron@amazon.de
Fixes: 3dc92c3114 ("kexec: add Kexec HandOver (KHO) generation helpers").
Signed-off-by: Evangelos Petrongonas <epetron@amazon.de>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When restoring a page (from kho_restore_pages()) or folio (from
kho_restore_folio()), KHO must initialize the struct page. The
initialization differs slightly depending on if a folio is requested or a
set of 0-order pages is requested.
Conceptually, it is quite simple to understand. When restoring 0-order
pages, each page gets a refcount of 1 and that's it. When restoring a
folio, head page gets a refcount of 1 and tail pages get 0.
kho_restore_page() tries to combine the two separate initialization flow
into one piece of code. While it works fine, it is more complicated to
read than it needs to be. Make the code simpler by splitting the two
initalization paths into two separate functions. This improves
readability by clearly showing how each type must be initialized.
Link: https://lkml.kernel.org/r/20260116112217.915803-3-pratyush@kernel.org
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "kho: clean up page initialization logic", v2.
This series simplifies the page initialization logic in
kho_restore_page(). It was originally only a single patch [0], but on
Pasha's suggestion, I added another patch to use unsigned long for
nr_pages.
Technically speaking, the patches aren't related and can be applied
independently, but bundling them together since patch 2 relies on 1 and it
is easier to manage them this way.
This patch (of 2):
With 4k pages, a 32-bit nr_pages can span up to 16 TiB. While it is a
lot, there exist systems with terabytes of RAM. gup is also moving to
using long for nr_pages. Use unsigned long and make KHO future-proof.
Link: https://lkml.kernel.org/r/20260116112217.915803-1-pratyush@kernel.org
Link: https://lkml.kernel.org/r/20260116112217.915803-2-pratyush@kernel.org
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The `struct kho_vmalloc` defines the in-memory layout for preserving
vmalloc regions across kexec. This layout is a contract between kernels
and part of the KHO ABI.
To reflect this relationship, the related structs and helper macros are
relocated to the ABI header, `include/linux/kho/abi/kexec_handover.h`.
This move places the structure's definition under the protection of the
KHO_FDT_COMPATIBLE version string.
The structure and its components are now also documented within the ABI
header to describe the contract and prevent ABI breaks.
[rppt@kernel.org: update comment, per Pratyush]
Link: https://lkml.kernel.org/r/aW_Mqp6HcqLwQImS@kernel.org
Link: https://lkml.kernel.org/r/20260105165839.285270-6-rppt@kernel.org
Signed-off-by: Jason Miu <jasonmiu@google.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Introduce the `include/linux/kho/abi/kexec_handover.h` header file, which
defines the stable ABI for the KHO mechanism. This header specifies how
preserved data is passed between kernels using an FDT.
The ABI contract includes the FDT structure, node properties, and the
"kho-v1" compatible string. By centralizing these definitions, this
header serves as the foundational agreement for inter-kernel communication
of preserved states, ensuring forward compatibility and preventing
misinterpretation of data across kexec transitions.
Since the ABI definitions are now centralized in the header files, the
YAML files that previously described the FDT interfaces are redundant.
These redundant files have therefore been removed.
Link: https://lkml.kernel.org/r/20260105165839.285270-5-rppt@kernel.org
Signed-off-by: Jason Miu <jasonmiu@google.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Decouple memfd preservation support from the core Live Update Orchestrator
configuration.
Previously, enabling CONFIG_LIVEUPDATE forced a dependency on CONFIG_SHMEM
and unconditionally compiled memfd_luo.o. However, Live Update may be
used for purposes that do not require memfd-backed memory preservation.
Introduce CONFIG_LIVEUPDATE_MEMFD to gate memfd_luo.o. This moves the
SHMEM and MEMFD_CREATE dependencies to the specific feature that needs
them, allowing the base LIVEUPDATE option to be selected independently of
shared memory support.
Link: https://lkml.kernel.org/r/20251230161402.1542099-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Memblock pages (including reserved memory) should have their allocation
tags initialized to CODETAG_EMPTY via clear_page_tag_ref() before being
released to the page allocator. When kho restores pages through
kho_restore_page(), missing this call causes mismatched
allocation/deallocation tracking and below warning message:
alloc_tag was not set
WARNING: include/linux/alloc_tag.h:164 at ___free_pages+0xb8/0x260, CPU#1: swapper/0/1
RIP: 0010:___free_pages+0xb8/0x260
kho_restore_vmalloc+0x187/0x2e0
kho_test_init+0x3c4/0xa30
do_one_initcall+0x62/0x2b0
kernel_init_freeable+0x25b/0x480
kernel_init+0x1a/0x1c0
ret_from_fork+0x2d1/0x360
Add missing clear_page_tag_ref() annotation in kho_restore_page() to
fix this.
Link: https://lkml.kernel.org/r/20260122132740.176468-1-ranxiaokai627@163.com
Fixes: fc33e4b44b ("kexec: enable KHO support for memory preservation")
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
If the previous kernel enabled KHO but did not call kho_finalize() (e.g.,
CONFIG_LIVEUPDATE=n or userspace skipped the finalization step), the
'preserved-memory-map' property in the FDT remains empty/zero.
Previously, kho_populate() would succeed regardless of the memory map's
state, reserving the incoming scratch regions in memblock. However,
kho_memory_init() would later fail to deserialize the empty map. By that
time, the scratch regions were already registered, leading to partial
initialization and subsequent list corruption (freeing scratch area twice)
during kho_init().
Move the validation of the preserved memory map earlier into
kho_populate(). If the memory map is empty/NULL:
1. Abort kho_populate() immediately with -ENOENT.
2. Do not register or reserve the incoming scratch memory, allowing the new
kernel to reclaim those pages as standard free memory.
3. Leave the global 'kho_in' state uninitialized.
Consequently, kho_memory_init() sees no active KHO context
(kho_in.mem_chunks_phys is 0) and falls back to kho_reserve_scratch(),
allocating fresh scratch memory as if it were a standard cold boot.
Link: https://lkml.kernel.org/r/20251223140140.2090337-1-pasha.tatashin@soleen.com
Fixes: de51999e68 ("kho: allow memory preservation state updates after finalization")
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reported-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Closes: https://lore.kernel.org/all/20251218215613.GA17304@ranerica-svr.sc.intel.com
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Tested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The new memfd code fails to link without SHMEM:
aarch64-linux-ld: mm/memfd_luo.o: in function `memfd_luo_retrieve_folios':
memfd_luo.c:(.text.memfd_luo_retrieve_folios+0xdc): undefined reference to `shmem_add_to_page_cache'
memfd_luo.c:(.text.memfd_luo_retrieve_folios+0x11c): undefined reference to `shmem_inode_acct_blocks'
memfd_luo.c:(.text.memfd_luo_retrieve_folios+0x134): undefined reference to `shmem_recalc_inode'
Add a Kconfig dependency to disallow that configuration.
Link: https://lkml.kernel.org/r/20251204100203.1034394-1-arnd@kernel.org
Fixes: b3749f174d ("mm: memfd_luo: allow preserving memfd")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The kernel test robot reported a Smatch warning:
kernel/liveupdate/luo_core.c:402 luo_ioctl() warn: unsigned 'nr' is
never less than zero.
This occurs because 'nr' is unsigned and LIVEUPDATE_CMD_BASE is currently
defined as 0, making the check (nr < LIVEUPDATE_CMD_BASE) always false.
Remove the explicit lower bound check. The logic remains correct because
'nr' is unsigned; if nr is less than LIVEUPDATE_CMD_BASE, the expression
(nr - LIVEUPDATE_CMD_BASE) will wrap around to a large positive value.
This will inevitably be larger than ARRAY_SIZE(luo_ioctl_ops) and be
caught by the upper bound check.
Link: https://lkml.kernel.org/r/20251130010919.1488230-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202511280300.6pvBmXUS-lkp@intel.com/
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When contiguous ranges of order-0 pages are restored, kho_restore_page()
calls prep_compound_page() with the first page in the range and order as
parameters and then kho_restore_pages() calls split_page() to make sure
all pages in the range are order-0.
However, since split_page() is not intended to split compound pages and
with VM_DEBUG enabled it will trigger a VM_BUG_ON_PAGE().
Update kho_restore_page() so that it will use prep_compound_page() when it
restores a folio and make sure it properly sets page count for both large
folios and ranges of order-0 pages.
Link: https://lkml.kernel.org/r/20251125110917.843744-3-rppt@kernel.org
Fixes: a667300bd5 ("kho: add support for preserving vmalloc allocations")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reported-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "kho: fixes for vmalloc restoration".
Pratyush reported off-list that when kho_restore_vmalloc() is used to
restore a vmalloc_huge() allocation it hits VM_BUG_ON() when we
reconstruct the struct pages in kho_restore_pages().
These patches fix the issue.
This patch (of 2):
In case a preserved vmalloc allocation was using huge pages, all pages in
the array of pages added to vm_struct during kho_restore_vmalloc() are
wrongly set to the same page.
Fix the indexing when assigning pages to that array.
Link: https://lkml.kernel.org/r/20251125110917.843744-1-rppt@kernel.org
Link: https://lkml.kernel.org/r/20251125110917.843744-2-rppt@kernel.org
Fixes: a667300bd5 ("kho: add support for preserving vmalloc allocations")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When booting with debug_pagealloc=on while having:
CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT=y
CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=n
the system fails to boot due to page faults during kmemleak scanning.
This occurs because:
With debug_pagealloc is enabled, __free_pages() invokes
debug_pagealloc_unmap_pages(), clearing the _PAGE_PRESENT bit for freed
pages in the kernel page table. KHO scratch areas are allocated from
memblock and noted by kmemleak. But these areas don't remain reserved but
released later to the page allocator using init_cma_reserved_pageblock().
This causes subsequent kmemleak scans access non-PRESENT pages, leading to
fatal page faults.
Mark scratch areas with kmemleak_ignore_phys() after they are allocated
from memblock to exclude them from kmemleak scanning before they are
released to buddy allocator to fix this.
[ran.xiaokai@zte.com.cn: add comment]
Link: https://lkml.kernel.org/r/20251127122700.103927-1-ranxiaokai627@163.com
Link: https://lkml.kernel.org/r/20251122182929.92634-1-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, kho_preserve_* and kho_unpreserve_* return -EBUSY if KHO is
finalized. This enforces a rigid "freeze" on the KHO memory state.
With the introduction of re-entrant finalization, this restriction is no
longer necessary. Users should be allowed to modify the preservation set
(e.g., adding new pages or freeing old ones) even after an initial
finalization.
The intended workflow for updates is now:
1. Modify state (preserve/unpreserve).
2. Call kho_finalize() again to refresh the serialized metadata.
Remove the kho_out.finalized checks to enable this dynamic behavior.
This also allows to convert kho_unpreserve_* functions to void, as they do
not return any error anymore.
Link: https://lkml.kernel.org/r/20251114190002.3311679-13-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Coiby Xu <coxu@redhat.com>
Cc: Dave Vasilevsky <dave@vasilevsky.ca>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Kees Cook <kees@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, kho_fill_kimage() checks kho_out.finalized and returns early if
KHO is not yet finalized. This enforces a strict ordering where userspace
must finalize KHO *before* loading the kexec image.
This is restrictive, as standard workflows often involve loading the
target kernel early in the lifecycle and finalizing the state (FDT) only
immediately before the reboot.
Since the KHO FDT resides at a physical address allocated during boot
(kho_init), its location is stable. We can attach this stable address to
the kimage regardless of whether the content has been finalized yet.
Relax the check to only require kho_enable, allowing kexec_file_load to
proceed at any time.
Link: https://lkml.kernel.org/r/20251114190002.3311679-12-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Coiby Xu <coxu@redhat.com>
Cc: Dave Vasilevsky <dave@vasilevsky.ca>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Kees Cook <kees@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, sub-FDTs were tracked in a list (kho_out.sub_fdts) and the
final FDT is constructed entirely from scratch during kho_finalize().
We can maintain the FDT dynamically:
1. Initialize a valid, empty FDT in kho_init().
2. Use fdt_add_subnode and fdt_setprop in kho_add_subtree to
update the FDT immediately when a subsystem registers.
3. Use fdt_del_node in kho_remove_subtree to remove entries.
This removes the need for the intermediate sub_fdts list and the
reconstruction logic in kho_finalize(). kho_finalize() now only needs to
trigger memory map serialization.
Link: https://lkml.kernel.org/r/20251114190002.3311679-11-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Baoquan He <bhe@redhat.com>
Cc: Coiby Xu <coxu@redhat.com>
Cc: Dave Vasilevsky <dave@vasilevsky.ca>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Kees Cook <kees@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
