Re: [PATCH] x86/asm: Simplify __smp_mb() definition

[Peter Zijlstra]

On Wed, May 12, 2021 at 11:33:10AM +0200, Borislav Petkov wrote:
> From: Borislav Petkov <bp@xxxxxxx>
> 
> Drop the bitness ifdeffery in favor of using the rSP register
> specification for 32 and 64 bit depending on the build.
> 
> No functional changes.
> 
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> ---
>  arch/x86/include/asm/barrier.h | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
> index 4819d5e5a335..3ba772a69cc8 100644
> --- a/arch/x86/include/asm/barrier.h
> +++ b/arch/x86/include/asm/barrier.h
> @@ -54,11 +54,8 @@ static inline unsigned long array_index_mask_nospec(unsigned long index,
>  #define dma_rmb()	barrier()
>  #define dma_wmb()	barrier()
>  
> -#ifdef CONFIG_X86_32
> -#define __smp_mb()	asm volatile("lock; addl $0,-4(%%esp)" ::: "memory", "cc")
> -#else
> -#define __smp_mb()	asm volatile("lock; addl $0,-4(%%rsp)" ::: "memory", "cc")
> -#endif
> +#define __smp_mb()	asm volatile("lock; addl $0,-4(%%" _ASM_SP ")" ::: "memory", "cc")
> +
>  #define __smp_rmb()	dma_rmb()
>  #define __smp_wmb()	barrier()
>  #define __smp_store_mb(var, value) do { (void)xchg(&var, value); } while (0)

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>