linux-kernel - Re: [PATCH v2 2/4] arm64: vdso32: drop test for -march=armv8-a

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Date:   Tue, 19 Oct 2021 17:43:51 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, llvm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 2/4] arm64: vdso32: drop test for -march=armv8-a

On Tue, Oct 19, 2021 at 03:36:44PM -0700, Nick Desaulniers wrote:
> As Arnd points out:
>   gcc-4.8 already supported -march=armv8, and we require gcc-5.1 now, so
>   both this #if/#else construct and the corresponding
>   "cc32-option,-march=armv8-a" check should be obsolete now.
> 
> Link: https://lore.kernel.org/lkml/CAK8P3a3UBEJ0Py2ycz=rHfgog8g3mCOeQOwO0Gmp-iz6Uxkapg@mail.gmail.com/
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Reviewed-by: Nathan Chancellor <nathan@...nel.org>

> ---
>  arch/arm64/include/asm/vdso/compat_barrier.h | 7 -------
>  arch/arm64/kernel/vdso32/Makefile            | 8 +-------
>  2 files changed, 1 insertion(+), 14 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/vdso/compat_barrier.h b/arch/arm64/include/asm/vdso/compat_barrier.h
> index fb60a88b5ed4..3ac35f4a667c 100644
> --- a/arch/arm64/include/asm/vdso/compat_barrier.h
> +++ b/arch/arm64/include/asm/vdso/compat_barrier.h
> @@ -20,16 +20,9 @@
>  
>  #define dmb(option) __asm__ __volatile__ ("dmb " #option : : : "memory")
>  
> -#if __LINUX_ARM_ARCH__ >= 8
>  #define aarch32_smp_mb()	dmb(ish)
>  #define aarch32_smp_rmb()	dmb(ishld)
>  #define aarch32_smp_wmb()	dmb(ishst)
> -#else
> -#define aarch32_smp_mb()	dmb(ish)
> -#define aarch32_smp_rmb()	aarch32_smp_mb()
> -#define aarch32_smp_wmb()	dmb(ishst)
> -#endif
> -
>  
>  #undef smp_mb
>  #undef smp_rmb
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index 89299a26638b..1407516e041e 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -65,13 +65,7 @@ endif
>  # From arm vDSO Makefile
>  VDSO_CAFLAGS += -fPIC -fno-builtin -fno-stack-protector
>  VDSO_CAFLAGS += -DDISABLE_BRANCH_PROFILING
> -
> -
> -# Try to compile for ARMv8. If the compiler is too old and doesn't support it,
> -# fall back to v7. There is no easy way to check for what architecture the code
> -# is being compiled, so define a macro specifying that (see arch/arm/Makefile).
> -VDSO_CAFLAGS += $(call cc32-option,-march=armv8-a -D__LINUX_ARM_ARCH__=8,\
> -                                   -march=armv7-a -D__LINUX_ARM_ARCH__=7)
> +VDSO_CAFLAGS += -march=armv8-a
>  
>  VDSO_CFLAGS := $(VDSO_CAFLAGS)
>  VDSO_CFLAGS += -DENABLE_COMPAT_VDSO=1
> -- 
> 2.33.0.1079.g6e70778dc9-goog
> 
>