Re: [Xen-devel] [PATCH] xen: Port the array_index_nospec() infrastructure from Linux

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.07.18 at 14:37, <andrew.cooper3@xxxxxxxxxx> wrote:
> This is as the infrastructure appeared in Linux 4.17, adapted slightly for
> Xen.  The architecture independent array_index_mask_nospec() is ported for
> ARMs benefit, as it currently lacks the optimised version.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

with one question though:

> --- a/xen/include/xen/compiler.h
> +++ b/xen/include/xen/compiler.h
> @@ -81,6 +81,10 @@
>  #pragma GCC visibility push(hidden)
>  #endif
>  
> +/* Make the optimizer believe the variable can be manipulated arbitrarily. 
> */
> +#define OPTIMIZER_HIDE_VAR(var)                 \
> +    __asm__ ("" : "=g" (var) : "0" (var))

Why not a simple "+g" output?

Also I think you want to add blanks inside the parentheses.

Jan



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