Re: [Xen-devel] [PATCH 4/4] xen/public: arm: rework the macro set_xen_guest_handle_raw

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.11.15 at 16:55, <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> Honestly I would be OK with having a typeof in the public headers to
> avoid this code, which is much harder to follow. Why don't we do
> something like the following:
> 
> 
> diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
> index 9a96401..e676ffb 100644
> --- a/xen/include/public/arch-arm.h
> +++ b/xen/include/public/arch-arm.h
> @@ -189,11 +189,12 @@
>  #define __XEN_GUEST_HANDLE(name)        __guest_handle_64_ ## name
>  #define XEN_GUEST_HANDLE(name)          __XEN_GUEST_HANDLE(name)
>  #define XEN_GUEST_HANDLE_PARAM(name)    __guest_handle_ ## name
> +#define barrier()     __asm__ __volatile__("": : :"memory")
>  #define set_xen_guest_handle_raw(hnd, val)                  \
>      do {                                                    \
> -        typeof(&(hnd)) _sxghr_tmp = &(hnd);                 \
> -        _sxghr_tmp->q = 0;                                  \
> -        _sxghr_tmp->p = val;                                \
> +        *((uint64_aligned_t *)&(hnd)) = 0;                  \
> +        barrier();                                          \
> +        (hnd).p = val;                                      \
>      } while ( 0 )

Because __asm__ again is an extension?

Jan


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