kernel/arch/s390/mm/pfault.c, branch linux-rolling-lts

s390/pfault: Fix virtual vs physical address confusion

2026-03-19T15:08:34Z

commit d879ac6756b662a085a743e76023c768c3241579 upstream. When Linux is running as guest, runs a user space process and the user space process accesses a page that the host has paged out, the guest gets a pfault interrupt and schedules a different process. Without this mechanism the host would have to suspend the whole virtual CPU until the page has been paged in. To setup the pfault interrupt the real address of parameter list should be passed to DIAGNOSE 0x258, but a virtual address is passed instead. That has a performance impact, since the pfault setup never succeeds, the interrupt is never delivered to a guest and the whole virtual CPU is suspended as result. Cc: stable@vger.kernel.org Fixes: c98d2ecae08f ("s390/mm: Uncouple physical vs virtual address spaces") Reported-by: Claudio Imbrenda Reviewed-by: Heiko Carstens Signed-off-by: Alexander Gordeev Signed-off-by: Vasily Gorbik Signed-off-by: Greg Kroah-Hartman

s390/asm-offsets: Remove ASM_OFFSETS_C

2025-03-31T10:20:39Z

Remove ASM_OFFSETS_C which is used as guard in thread_info.h to decide if asm-offsets can be included or not. There is no reason to include asm-offsets.h in thread_info.h anymore. Remove the define and the not needed include. Explicitly include asm-offsets.h in all header files which require it, and where it used to be included implicitly via thread_info.h. This reduces header dependencies. 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

2025-03-18T16:13:51Z

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/pfault: use consistent comment style

2023-07-29T12:57:18Z

Use consistent comment style within the whole pfault C code. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/pfault: cleanup inline assemblies

2023-07-29T12:57:18Z

Cleanup the pfault inline assemblies: - Use symbolic names for operands - Add extra linebreaks, and whitespace to improve readability In addition, change __pfault_init() to return -EOPNOTSUPP in case of an exception, and don't return a made up valid diag 258 return value (aka "8"). This allows to simplify the inline assembly, and makes debugging easier, in case something is broken. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/pfault: use early_param() instead if __setup()

2023-07-29T12:57:18Z

early_param() is the standard way of defining early kernel command line parameters. Use that instead of the old __setup() variant. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/pfault: remove not needed packed and aligned attributes

2023-07-29T12:57:18Z

struct pfault_refbk is naturally packed and aligned; remove not needed packed and aligned attributes. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/pfault: use UL instead of ULL

2023-07-29T12:57:18Z

Remove another leftover of the 31 bit area: replace the not needed "unsigned long long" suffix with "unsigned long", and stay consistent with the rest of the code. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens

s390/mm: move pfault code to own C file

2023-07-29T12:57:18Z

The pfault code has nothing to do with regular fault handling. Therefore move it to an own C file. Also add an own pfault header file. This way changes to setup.h don't cause a recompile of the pfault code and vice versa. Reviewed-by: Sven Schnelle Signed-off-by: Heiko Carstens