next-20250912: riscv: s390: mm/kasan/shadow.c 'kasan_populate_vmalloc_pte' pgtable.h:247:41: error: statement with no effect [-Werror=unused-value]

[Naresh Kamboju]

The following build warnings / errors noticed on the riscv and s390
with allyesconfig build on the Linux next-20250912 tag.

Regression Analysis:
- New regression? yes
- Reproducibility? yes

Build regression: next-20250912 mm/kasan/shadow.c
'kasan_populate_vmalloc_pte' pgtable.h error statement with no effect
[-Werror=unused-value]

Reported-by: Linux Kernel Functional Testing <lkft at linaro.org>

$ git log --oneline next-20250911..next-20250912 --  mm/kasan/shadow.c
  aed53ec0b797a mm: introduce local state for lazy_mmu sections
  307f2dc9b308e kasan: introduce ARCH_DEFER_KASAN and unify static key
across modes

## Test log
In file included from include/linux/kasan.h:37,
                 from mm/kasan/shadow.c:14:
mm/kasan/shadow.c: In function 'kasan_populate_vmalloc_pte':
include/linux/pgtable.h:247:41: error: statement with no effect
[-Werror=unused-value]
  247 | #define arch_enter_lazy_mmu_mode()      (LAZY_MMU_DEFAULT)
      |                                         ^
mm/kasan/shadow.c:322:9: note: in expansion of macro 'arch_enter_lazy_mmu_mode'
  322 |         arch_enter_lazy_mmu_mode();
      |         ^~~~~~~~~~~~~~~~~~~~~~~~
mm/kasan/shadow.c: In function 'kasan_depopulate_vmalloc_pte':
include/linux/pgtable.h:247:41: error: statement with no effect
[-Werror=unused-value]
  247 | #define arch_enter_lazy_mmu_mode()      (LAZY_MMU_DEFAULT)
      |                                         ^
mm/kasan/shadow.c:497:9: note: in expansion of macro 'arch_enter_lazy_mmu_mode'
  497 |         arch_enter_lazy_mmu_mode();
      |         ^~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

## Source
* Kernel version: 6.17.0-rc5
* Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
* Git describe: 6.17.0-rc5-next-20250912
* Git commit: 590b221ed4256fd6c34d3dea77aa5bd6e741bbc1
* Architectures: riscv, s390
* Toolchains: gcc (Debian 13.3.0-16) 13.3.0
* Kconfigs: allyesconfig

## Build
* Build log: https://qa-reports.linaro.org/api/testruns/29863344/log_file/
* Build details:
https://regressions.linaro.org/lkft/linux-next-master/next-20250912/log-parser-build-gcc/gcc-compiler-include_linux_pgtable_h-error-statement-with-no-effect/
* Build plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/builds/32aTGVWBLzkF7PsIq9FBtLK3T4W
* Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/32aTGVWBLzkF7PsIq9FBtLK3T4W/
* Kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/32aTGVWBLzkF7PsIq9FBtLK3T4W/config

## Steps to reproduce
 $ tuxmake --runtime podman --target-arch riscv --toolchain gcc-13
--kconfig allyesconfig


--
Linaro LKFT