Re: [PATCH v8 16/29] arm64: Share arm64 headers with s390

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] build: fragile cross-architecture coupling via text extraction
--

commit 7c91cae0fde64b5f320fb846c975eb58dd534362
Author: Steffen Eiden <seiden@linux.ibm.com>

arm64: Share arm64 headers with s390

This commit prepares arm64 headers to be shared with s390 by adding
ifdef markers and comments. A preprocessor symbol is added to the arm64
Makefile to keep the code active on arm64 while s390 can extract it.

> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 6b005c8fef706..12cbad460258f 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -45,6 +45,11 @@ KBUILD_CFLAGS	+= $(CC_FLAGS_NO_FPU) \
>  KBUILD_CFLAGS	+= $(call cc-disable-warning, psabi)
>  KBUILD_AFLAGS	+= $(compat_vdso)
>  
> +# Enable all code shared to s390
> +KBUILD_CFLAGS	+= -DARM64_S390_COMMON

[Severity: Low]
Does adding a global define purely to wrap code for an s390 extraction
script create a fragile build coupling? This couples the s390 build to 
the exact formatting and macro placement in arm64 headers.

> +KBUILD_AFLAGS	+= -DARM64_S390_COMMON
> +KBUILD_CPPFLAGS	+= -DARM64_S390_COMMON
> +

[ ... ]

> diff --git a/arch/arm64/include/asm/brk-imm.h b/arch/arm64/include/asm/brk-imm.h
> index beb42c62b6acc..dd2d153dc0d81 100644
> --- a/arch/arm64/include/asm/brk-imm.h
> +++ b/arch/arm64/include/asm/brk-imm.h
> @@ -2,6 +2,7 @@
>  /*
>   * Copyright (C) 2012 ARM Ltd.
>   */
> +/* Whole file is shared with s390 */

[Severity: Low]
Is it robust to rely on an informal textual comment to drive cross-architecture
sharing instead of moving the file to an architecture-neutral location like
asm-generic? Normal refactoring by arm64 maintainers could trivially break
the s390 build if they remove or modify these marker comments.

>  
>  #ifndef __ASM_BRK_IMM_H
>  #define __ASM_BRK_IMM_H

[ ... ]

> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index a34a9417ff4da..09f04a5686a18 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -47,6 +47,7 @@ void kvm_skip_instr32(struct kvm_vcpu *vcpu);
>  int kvm_inject_dabt_excl_atomic(struct kvm_vcpu *vcpu, u64 addr);
>  int kvm_inject_serror_esr(struct kvm_vcpu *vcpu, u64 esr);
>  
> +#ifdef ARM64_S390_COMMON
>  void kvm_inject_undefined(struct kvm_vcpu *vcpu);

[Severity: Low]
Could this genuinely shared component be factored into a common include
directory like include/kvm or include/linux instead of being spliced via
build-time regex parsing? Adding s390-specific extraction guards into
arm64 headers requires arm64 maintainers to accommodate s390 build scripts
when modifying ifdef boundaries.

>  void kvm_inject_sync(struct kvm_vcpu *vcpu, u64 esr);
>  int kvm_inject_sea(struct kvm_vcpu *vcpu, bool iabt, u64 addr);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260918133107.1042730-1-seiden@linux.ibm.com?part=16