linux-stable.git/arch/s390/kernel/setup.c, branch linux-rolling-stable

mm, arch: consolidate hugetlb CMA reservation

2026-01-27T04:02:19+00:00

Every architecture that supports hugetlb_cma command line parameter
reserves CMA areas for hugetlb during setup_arch().

This obfuscates the ordering of hugetlb CMA initialization with respect to
the rest initialization of the core MM.

Introduce arch_hugetlb_cma_order() callback to allow architectures report
the desired order-per-bit of CMA areas and provide a week implementation
of arch_hugetlb_cma_order() for architectures that don't support hugetlb
with CMA.

Use this callback in hugetlb_cma_reserve() instead if passing the order as
parameter and call hugetlb_cma_reserve() from mm_core_init_early() rather
than have it spread over architecture specific code.

Link: https://lkml.kernel.org/r/20260111082105.290734-28-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) 
Cc: Alexander Gordeev 
Cc: Alex Shi 
Cc: Andreas Larsson 
Cc: "Borislav Petkov (AMD)" 
Cc: Catalin Marinas 
Cc: David Hildenbrand 
Cc: David S. Miller 
Cc: Dinh Nguyen 
Cc: Geert Uytterhoeven 
Cc: Guo Ren 
Cc: Heiko Carstens 
Cc: Helge Deller 
Cc: Huacai Chen 
Cc: Ingo Molnar 
Cc: Johannes Berg 
Cc: John Paul Adrian Glaubitz 
Cc: Jonathan Corbet 
Cc: Klara Modin 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes 
Cc: Magnus Lindholm 
Cc: Matt Turner 
Cc: Max Filippov 
Cc: Michael Ellerman 
Cc: Michal Hocko 
Cc: Michal Simek 
Cc: Muchun Song 
Cc: Oscar Salvador 
Cc: Palmer Dabbelt 
Cc: Pratyush Yadav 
Cc: Richard Weinberger 
Cc: "Ritesh Harjani (IBM)" 
Cc: Russell King 
Cc: Stafford Horne 
Cc: Suren Baghdasaryan 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Vasily Gorbik 
Cc: Vineet Gupta 
Cc: Vlastimil Babka 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

s390: Rename head64.S to head.S

2025-11-25T14:28:07+00:00

All the code is 64 bit, therefore remove the superfluous suffix.

Reviewed-by: Jens Remus 
Signed-off-by: Heiko Carstens

s390: Remove KMSG_COMPONENT macro

2025-11-24T10:45:21+00:00

The KMSG_COMPONENT macro is a leftover of the s390 specific "kernel
message catalog" which never made it upstream.

Remove the macro in order to get rid of a pointless indirection. Replace
all users with the string it defines. In almost all cases this leads to a
simple replacement like this:

 - #define KMSG_COMPONENT "appldata"
 - #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 + #define pr_fmt(fmt) "appldata: " fmt

Except for some special cases this is just mechanical/scripted work.

Acked-by: Thomas Richter 
Signed-off-by: Heiko Carstens

s390: Remove compat support

2025-11-17T10:10:38+00:00

There shouldn't be any 31 bit code around anymore that matters.
Remove the compat layer support required to run 31 bit code.

Reason for removal is code simplification and reduced test effort.

Note that this comes without any deprecation warnings added to config
options, or kernel messages, since most likely those would be ignored
anyway.

If it turns out there is still a reason to keep the compat layer this
can be reverted at any time in the future.

Reviewed-by: Arnd Bergmann 
Signed-off-by: Heiko Carstens

s390: Remove superfluous newlines from inline assemblies

2025-09-29T11:52:08+00:00

Remove superfluous newlines from inline assemblies. Compilers use the
number of lines of inline assemblies as heuristic for the complexity
and inline decisions. Therefore inline assemblies should only contain
as many lines as required.

A lot of inline assemblies contain a superfluous newline for the last
line. Remove such newlines to improve compiler inlining decisions.

Suggested-by: Juergen Christ 
Signed-off-by: Heiko Carstens 
Reviewed-by: Alexander Gordeev 
Reviewed-by: Juergen Christ 
Signed-off-by: Alexander Gordeev

Merge tag 's390-6.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2025-08-08T03:56:55+00:00

Pull more s390 updates from Alexander Gordeev:

 - Support MMIO read/write tracing

 - Enable THP swapping and THP migration

 - Unmask SLCF bit ("stateless command filtering") introduced with CEX8
   cards, so that user space applications like lszcrypt could evaluate
   and list this feature

 - Fix the value of high_memory variable, so it considers possible
   tailing offline memory blocks

 - Make vmem_pte_alloc() consistent and always allocate memory of
   PAGE_SIZE for page tables. This ensures a page table occupies the
   whole page, as the rest of the code assumes

 - Fix kernel image end address in the decompressor debug output

 - Fix a typo in debug_sprintf_format_fn() comment

* tag 's390-6.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  s390/debug: Fix typo in debug_sprintf_format_fn() comment
  s390/boot: Fix startup debugging log
  s390/mm: Allocate page table with PAGE_SIZE granularity
  s390/mm: Enable THP_SWAP and THP_MIGRATION
  s390: Support CONFIG_TRACE_MMIO_ACCESS
  s390/mm: Set high_memory at the end of the identity mapping
  s390/ap: Unmask SLCF bit in card and queue ap functions sysfs

s390/mm: Set high_memory at the end of the identity mapping

2025-07-31T16:59:26+00:00

The value of high_memory variable is set by set_high_memory() function
to a value returned by memblock_end_of_DRAM(). The latter function
returns by default the upper bound of the last online memory block,
not the upper bound of the directly mapped memory region. As result,
in case the end of memory happens to be offline, high_memory variable
is set to a value that is short on the last offline memory blocks size:

RANGE                                  SIZE   STATE REMOVABLE   BLOCK
0x0000000000000000-0x000000ffffffffff    1T  online       yes   0-511
0x0000010000000000-0x0000011fffffffff  128G offline           512-575

Memory block size:         2G
Total online memory:       1T
Total offline memory:    128G

crash> p/x vm_layout
$1 = {
  kaslr_offset = 0x3453e918000,
  kaslr_offset_phys = 0xa534218000,
  identity_base = 0x0,
  identity_size = 0x12000000000
}
crash> p/x high_memory
$2 = 0x10000000000

In the past the value of high_memory was derived from max_low_pfn,
which in turn was derived from the identity_size. Since identity_size
accommodates the whole memory size - including tailing offline blocks,
the offlined blocks did not impose any problem. But since commit
e120d1bc12da ("arch, mm: set high_memory in free_area_init()") the
value of high_memory is derived from the last memblock online region,
and that is where the problem comes from.

The value of high_memory is used by several drivers and by external
tools (e.g. crash tool aborts while loading a dump).

Similarily to ARM, use the override path provided by set_high_memory()
function and set the value of high_memory at the end of the identity
mapping early. That forces set_high_memory() to leave in high_memory
the correct value, even when the end of available memory is offline.

Fixes: e120d1bc12da ("arch, mm: set high_memory in free_area_init()")
Tested-by: Mikhail Zaslonko 
Reviewed-by: Heiko Carstens 
Reviewed-by: Gerald Schaefer 
Signed-off-by: Alexander Gordeev

Add a new optional ",cma" suffix to the crashkernel= command line option

2025-07-20T02:08:22+00:00

Patch series "kdump: crashkernel reservation from CMA", v5.

This series implements a way to reserve additional crash kernel memory
using CMA.

Currently, all the memory for the crash kernel is not usable by the 1st
(production) kernel.  It is also unmapped so that it can't be corrupted by
the fault that will eventually trigger the crash.  This makes sense for
the memory actually used by the kexec-loaded crash kernel image and initrd
and the data prepared during the load (vmcoreinfo, ...).  However, the
reserved space needs to be much larger than that to provide enough
run-time memory for the crash kernel and the kdump userspace.  Estimating
the amount of memory to reserve is difficult.  Being too careful makes
kdump likely to end in OOM, being too generous takes even more memory from
the production system.  Also, the reservation only allows reserving a
single contiguous block (or two with the "low" suffix).  I've seen systems
where this fails because the physical memory is fragmented.

By reserving additional crashkernel memory from CMA, the main crashkernel
reservation can be just large enough to fit the kernel and initrd image,
minimizing the memory taken away from the production system.  Most of the
run-time memory for the crash kernel will be memory previously available
to userspace in the production system.  As this memory is no longer
wasted, the reservation can be done with a generous margin, making kdump
more reliable.  Kernel memory that we need to preserve for dumping is
normally not allocated from CMA, unless it is explicitly allocated as
movable.  Currently this is only the case for memory ballooning and zswap.
Such movable memory will be missing from the vmcore.  User data is
typically not dumped by makedumpfile.  When dumping of user data is
intended this new CMA reservation cannot be used.

There are five patches in this series:

The first adds a new ",cma" suffix to the recenly introduced generic
crashkernel parsing code.  parse_crashkernel() takes one more argument to
store the cma reservation size.

The second patch implements reserve_crashkernel_cma() which performs the
reservation.  If the requested size is not available in a single range,
multiple smaller ranges will be reserved.

The third patch updates Documentation/, explicitly mentioning the
potential DMA corruption of the CMA-reserved memory.

The fourth patch adds a short delay before booting the kdump kernel,
allowing pending DMA transfers to finish.

The fifth patch enables the functionality for x86 as a proof of
concept. There are just three things every arch needs to do:
- call reserve_crashkernel_cma()
- include the CMA-reserved ranges in the physical memory map
- exclude the CMA-reserved ranges from the memory available
  through /proc/vmcore by excluding them from the vmcoreinfo
  PT_LOAD ranges.

Adding other architectures is easy and I can do that as soon as this
series is merged.

With this series applied, specifying
	crashkernel=100M craskhernel=1G,cma
on the command line will make a standard crashkernel reservation
of 100M, where kexec will load the kernel and initrd.

An additional 1G will be reserved from CMA, still usable by the production
system.  The crash kernel will have 1.1G memory available.  The 100M can
be reliably predicted based on the size of the kernel and initrd.

The new cma suffix is completely optional. When no
crashkernel=size,cma is specified, everything works as before.


This patch (of 5):

Add a new cma_size parameter to parse_crashkernel().  When not NULL, call
__parse_crashkernel to parse the CMA reservation size from
"crashkernel=size,cma" and store it in cma_size.

Set cma_size to NULL in all calls to parse_crashkernel().

Link: https://lkml.kernel.org/r/aEqnxxfLZMllMC8I@dwarf.suse.cz
Link: https://lkml.kernel.org/r/aEqoQckgoTQNULnh@dwarf.suse.cz
Signed-off-by: Jiri Bohac 
Cc: Baoquan He 
Cc: Dave Young 
Cc: Donald Dutile 
Cc: Michal Hocko 
Cc: Philipp Rudo 
Cc: Pingfan Liu 
Cc: Tao Liu 
Cc: Vivek Goyal 
Cc: David Hildenbrand 
Signed-off-by: Andrew Morton

s390/lowcore: Remove unused machine_flags

2025-03-31T10:20:39+00:00

The machine_flags member in struct lowcore is not used anymore.
Remove it.

Reviewed-by: Sven Schnelle 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/bear: Convert cpu_has_bear() to cpu feature function

2025-03-04T16:18:07+00:00

Get rid of the cpu_has_bear jump label and convert cpu_has_bear() to a cpu
feature function using test_facility() and with that use a static branch.

Reviewed-by: Vasily Gorbik 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik