linux.git/arch/s390/include/asm/processor.h, branch v6.16

s390/processor: Use bitop functions for cpu flag helper functions

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

Use bitop functions to implement cpu flag helper functions. This way
it is guaranteed that bits cannot get lost if modified in different
contexts on a cpu.

E.g. if process context is interrupted in the middle of a
read-modify-write sequence while modifying cpu flags, and within
interrupt context cpu flags are also modified, bits can get lost.

There is currently no code which is doing this, however upcoming code
could potentially run into this problem.

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

s390: Use inline qualifier for all EX_TABLE and ALTERNATIVE inline assemblies

2025-03-18T16:13:51+00:00

Use asm_inline for all inline assemblies which make use of the EX_TABLE or
ALTERNATIVE macros.

These macros expand to many lines and the compiler assumes the number of
lines within an inline assembly is the same as the number of instructions
within an inline assembly. This has an effect on inlining and loop
unrolling decisions.

In order to avoid incorrect assumptions use asm_inline, which tells the
compiler that an inline assembly has the smallest possible size.

In order to avoid confusion when asm_inline should be used or not, since a
couple of inline assemblies are quite large: the rule is to always use
asm_inline whenever the EX_TABLE or ALTERNATIVE macro is used. In specific
cases there may be reasons to not follow this guideline, but that should
be documented with the corresponding code.

Using the inline qualifier everywhere has only a small effect on the kernel
image size:

add/remove: 0/10 grow/shrink: 19/8 up/down: 1492/-1858 (-366)

The only location where this seems to matter is load_unaligned_zeropad()
from word-at-a-time.h where the compiler inlines more functions within the
dcache code, which is indeed code where performance matters.

Suggested-by: Juergen Christ 
Reviewed-by: Juergen Christ 
Signed-off-by: Heiko Carstens 
Signed-off-by: Vasily Gorbik

s390/stackleak: Use exrl instead of ex in __stackleak_poison()

2025-01-13T08:50:17+00:00

exrl is present in all machines currently supported, therefore prefer
it over ex. This saves one instruction and doesn't need an additional
register to hold the address of the target instruction.

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

s390/mm/fault: Handle guest-related program interrupts in KVM

2024-10-29T10:49:18+00:00

Any program interrupt that happens in the host during the execution of
a KVM guest will now short circuit the fault handler and return to KVM
immediately. Guest fault handling (including pfault) will happen
entirely inside KVM.

When sie64a() returns zero, current->thread.gmap_int_code will contain
the program interrupt number that caused the exit, or zero if the exit
was not caused by a host program interrupt.

KVM will now take care of handling all guest faults in vcpu_post_run().

Since gmap faults will not be visible by the rest of the kernel, remove
GMAP_FAULT, the linux fault handlers for secure execution faults, the
exception table entries for the sie instruction, the nop padding after
the sie instruction, and all other references to guest faults from the
s390 code.

Signed-off-by: Claudio Imbrenda 
Co-developed-by: Heiko Carstens 
Link: https://lore.kernel.org/r/20241022120601.167009-6-imbrenda@linux.ibm.com
Signed-off-by: Heiko Carstens

s390/smp: Add cpu capacities

2024-08-29T20:56:35+00:00

Linux scheduler allows architectures to assign capacity values to
individual CPUs. This hints scheduler the performance difference between
CPUs and allows more efficient task distribution them. Implement
helper methods to set and get CPU capacities for s390. This is
particularly helpful in vertical polarization configurations of LPARs.
On vertical polarization an LPARs CPUs can get different polarization
values depending on the CEC configuration. CPUs with different
polarization values can perform different from each other, using CPU
capacities this can be reflected to linux scheduler.

Acked-by: Vasily Gorbik 
Signed-off-by: Mete Durlu 
Signed-off-by: Vasily Gorbik

s390/entry: Move SIE indicator flag to thread info

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

CIF_SIE indicates if a thread is running in SIE context. This is the
state of a thread and not the CPU. Therefore move this indicator to
thread info.

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

s390/nospec: Push down alternative handling

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

The nospec implementation is deeply integrated into the alternatives
code: only for nospec an alternative facility list is implemented and
used by the alternative code, while it is modified by nospec specific
needs.

Push down the nospec alternative handling into the nospec by
introducing a new alternative type and a specific nospec callback to
decide if alternatives should be applied.

Also introduce a new global nobp variable which together with facility
82 can be used to decide if nobp is enabled or not.

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

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: Move CIF flags to struct pcpu

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

To allow testing flags for offline CPUs, move the CIF flags
to struct pcpu. To avoid having to calculate the array index
for each access, add a pointer to the pcpu member for the current
cpu to lowcore.

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