Re: [Xen-devel] [PATCH 09/10] xen: arm: weaken SMP barriers to inner shareable.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Fri, 28 Jun 2013, Ian Campbell wrote:
> Since all processors are in the inner-shareable domain and we map everything
> that way this is sufficient.
> 
> The non-SMP barriers remain full system. Although in principal they could
> become outer shareable barriers for some hardware this would require us to
> know which class a given device is. Given the small number of device drivers
> in Xen itself its probably not worth worrying over, although maybe someone
> will benchmark at some point.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>


>  xen/include/asm-arm/system.h |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/include/asm-arm/system.h b/xen/include/asm-arm/system.h
> index 68efba9..7c3e42d 100644
> --- a/xen/include/asm-arm/system.h
> +++ b/xen/include/asm-arm/system.h
> @@ -20,9 +20,9 @@
>  #define rmb()           dsb("sy")
>  #define wmb()           dsb("sy")
>  
> -#define smp_mb()        dmb("sy")
> -#define smp_rmb()       dmb("sy")
> -#define smp_wmb()       dmb("sy")
> +#define smp_mb()        dmb("ish")
> +#define smp_rmb()       dmb("ish")
> +#define smp_wmb()       dmb("ish")
>  
>  #define xchg(ptr,x) \
>          ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
> -- 
> 1.7.2.5
> 

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