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

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

s390: Convert MACHINE_IS_[LPAR|VM|KVM], etc, machine_is_[lpar|vm|kvm]()

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

Move machine type detection to the decompressor and use static branches
to implement and use machine_is_[lpar|vm|kvm]() instead of a runtime check
via MACHINE_IS_[LPAR|VM|KVM].

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

s390/lowcore: Convert relocated lowcore alternative to machine feature

2025-03-04T16:18:05+00:00

Convert the explicit relocated lowcore alternative type to a more
generic machine feature. This only reduces the number of alternative
types, but has no impact on code generation.

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

s390/cpufeature: Convert MACHINE_HAS_EDAT2 to cpu_has_edat2()

2025-03-04T16:18:05+00:00

Convert MACHINE_HAS_... to cpu_has_...() which uses test_facility() instead
of testing the machine_flags lowcore member if the feature is present.

test_facility() generates better code since it results in a static branch
without accessing memory. The branch is patched via alternatives by the
decompressor depending on the availability of the required facility.

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

Merge tag 's390-6.14-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2025-01-30T18:48:17+00:00

Pull more s390 updates from Alexander Gordeev:

 - The rework that uncoupled physical and virtual address spaces
   inadvertently prevented KASAN shadow mappings from using large pages.
   Restore large page mappings for KASAN shadows

 - Add decompressor routine physmem_alloc() that may fail, unlike
   physmem_alloc_or_die(). This allows callers to implement fallback
   paths

 - Allow falling back from large pages to smaller pages (1MB or 4KB) if
   the allocation of 2GB pages in the decompressor can not be fulfilled

 - Add to the decompressor boot print support of "%%" format string,
   width and padding hadnling, length modifiers and decimal conversion
   specifiers

 - Add to the decompressor message severity levels similar to kernel
   ones. Support command-line options that control console output
   verbosity

 - Replaces boot_printk() calls with appropriate loglevel- specific
   helpers such as boot_emerg(), boot_warn(), and boot_debug().

 - Collect all boot messages into a ring buffer independent of the
   current log level. This is particularly useful for early crash
   analysis

 - If 'earlyprintk' command line parameter is not specified, store
   decompressor boot messages in a ring buffer to be printed later by
   the kernel, once the console driver is registered

 - Add 'bootdebug' command line parameter to enable printing of
   decompressor debug messages when needed. That parameters allows
   message suppressing and filtering

 - Dump boot messages on a decompressor crash, but only if 'bootdebug'
   command line parameter is enabled

 - When CONFIG_PRINTK_TIME is enabled, add timestamps to boot messages
   in the same format as regular printk()

 - Dump physical memory tracking information on boot: online ranges,
   reserved areas and vmem allocations

 - Dump virtual memory layout and randomization details

 - Improve decompression error reporting and dump the message ring
   buffer in case the boot failed and system halted

 - Add an exception handler which handles exceptions when FPU control
   register is attempted to be set to an invalid value. Remove '.fixup'
   section as result of this change

 - Use 'A', 'O', and 'R' inline assembly format flags, which allows
   recent Clang compilers to generate better FPU code

 - Rework uaccess code so it reads better and generates more efficient
   code

 - Cleanup futex inline assembly code

 - Disable KMSAN instrumention for futex inline assemblies, which
   contain dereferenced user pointers. Otherwise, shadows for the user
   pointers would be accessed

 - PFs which are not initially configured but in standby create only a
   single-function PCI domain. If they are configured later on, sibling
   PFs and their child VFs will not be added to their PCI domain
   breaking SR-IOV expectations.

   Fix that by allowing initially configured but in standby PFs create
   multi-function PCI domains

 - Add '-std=gnu11' to decompressor and purgatory CFLAGS to avoid
   compile errors caused by kernel's own definitions of 'bool', 'false',
   and 'true' conflicting with the C23 reserved keywords

 - Fix sclp subsystem failure when a sclp console is not present

 - Fix misuse of non-NULL terminated strings in vmlogrdr driver

 - Various other small improvements, cleanups and fixes

* tag 's390-6.14-2' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (53 commits)
  s390/vmlogrdr: Use array instead of string initializer
  s390/vmlogrdr: Use internal_name for error messages
  s390/sclp: Initialize sclp subsystem via arch_cpu_finalize_init()
  s390/tools: Use array instead of string initializer
  s390/vmem: Fix null-pointer-arithmetic warning in vmem_map_init()
  s390: Add '-std=gnu11' to decompressor and purgatory CFLAGS
  s390/bitops: Use correct constraint for arch_test_bit() inline assembly
  s390/pci: Fix SR-IOV for PFs initially in standby
  s390/futex: Avoid KMSAN instrumention for user pointers
  s390/uaccess: Rename get_put_user_noinstr_attributes to uaccess_kmsan_or_inline
  s390/futex: Cleanup futex_atomic_cmpxchg_inatomic()
  s390/futex: Generate futex atomic op functions
  s390/uaccess: Remove INLINE_COPY_FROM_USER and INLINE_COPY_TO_USER
  s390/uaccess: Use asm goto for put_user()/get_user()
  s390/uaccess: Remove usage of the oac specifier
  s390/uaccess: Replace EX_TABLE_UA_LOAD_MEM exception handling
  s390/uaccess: Cleanup noinstr __put_user()/__get_user() inline assembly constraints
  s390/uaccess: Remove __put_user_fn()/__get_user_fn() wrappers
  s390/uaccess: Move put_user() / __put_user() close to put_user() asm code
  s390/uaccess: Use asm goto for __mvc_kernel_nofault()
  ...