linux-stable.git/arch/s390/lib/spinlock.c, branch linux-rolling-stable

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

s390/spinlock: Implement SPINLOCK_LOCKVAL with inline assembly

2025-03-18T16:13:04+00:00

Implement SPINLOCK_LOCKVAL with an inline assembly, which makes use of the
ALTERNATIVE macro, to read spinlock_lockval from lowcore. Provide an
alternative instruction with a different offset in case lowcore is
relocated.

This replaces sequences of two instructions with one instruction.

Before:
  10602a:       a7 78 00 00             lhi     %r7,0
  10602e:       a5 8e 00 00             llilh   %r8,0
  106032:       58 d0 83 ac             l       %r13,940(%r8)
  106036:       ba 7d b5 80             cs      %r7,%r13,1408(%r11)

After:
  10602a:       a7 88 00 00             lhi     %r8,0
  10602e:       e3 70 03 ac 00 58       ly      %r7,940
  106034:       ba 87 b5 80             cs      %r8,%r7,1408(%r11)

Kernel image size change:
add/remove: 756/750 grow/shrink: 646/3435 up/down: 30778/-46326 (-15548)

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

s390: Move s390 sysctls into their own file under arch/s390

2025-03-18T16:13:04+00:00

Move s390 sysctls (spin_retry and userprocess_debug) into their own
files under arch/s390. Create two new sysctl tables
(2390_{fault,spin}_sysctl_table) which will be initialized with
arch_initcall placing them after their original place in proc_root_init.

This is part of a greater effort to move ctl tables into their
respective subsystems which will reduce the merge conflicts in
kernel/sysctl.c.

Signed-off-by: joel granados 
Acked-by: Heiko Carstens 
Link: https://lore.kernel.org/r/20250306-jag-mv_ctltables-v2-6-71b243c8d3f8@kernel.org
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/spinlock: Use flag output constraint for arch_cmpxchg_niai8()

2024-11-28T13:14:34+00:00

Add a new variant of arch_cmpxchg_niai8() which makes use of the flag
output constraint, which allows the compiler to generate slightly better
code. Also rename arch_cmpxchg_niai8() to arch_try_cmpxchg_niai8() which
reflects the purpose of the function and makes it consistent with other
"try" variants.

Signed-off-by: Heiko Carstens

s390/spinlock: Use R constraint for arch_load_niai4()

2024-11-28T13:12:05+00:00

The load instruction used within arch_load_niai4() has a short displacement
and index register. Therefore use the R constraint to reflect this.
The used Q constraint does consider an index register.

Signed-off-by: Heiko Carstens

s390/spinlock: Use symbolic names in inline assemblies

2024-11-28T13:12:04+00:00

Improve readability and use symbolic names.

Signed-off-by: Heiko Carstens

s390/locking: Use arch_try_cmpxchg() instead of __atomic_cmpxchg_bool()

2024-11-12T13:01:29+00:00

Use arch_try_cmpxchg() instead of __atomic_cmpxchg_bool() everywhere.
This generates the same code like before, but uses the standard
cmpxchg() implementation instead of a custom __atomic_cmpxchg_bool().

Reviewed-by: Juergen Christ 
Signed-off-by: Heiko Carstens

s390/alternatives: Rework to allow for callbacks

2024-07-23T14:02:31+00:00

Rework alternatives to allow for callbacks. With this every
alternative entry has additional data encoded:

- When (aka context) an alternative is supposed to be applied

- The type of an alternative, which allows for type specific handling
  and callbacks

- Extra type specific payload (patch information), which can be passed
  to callbacks in order to decide if an alternative should be applied
  or not

With this only the "late" context is implemented, which means there is
no change to the previous behaviour. All code is just converted to the
more generic new infrastructure.

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

s390: Replace S390_lowcore by get_lowcore()

2024-06-18T15:01:33+00:00

Replace all S390_lowcore usages in arch/s390/ by get_lowcore().

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