Re: [Xen-devel] [PATCH 06/12] xen/arm64: sysreg: Implement the 32-bit helpers using the 64-bit helpers

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 27 Mar 2019, Julien Grall wrote:
> Clang is pickier than GCC for the register size in asm statement. It
> expects the register size to match the value size.
> 
> The instructions msr/mrs are expecting a 64-bit register. This means the
> implementation of the 32-bit helpers is not correct. The easiest
> solution is to implement the 32-bit helpers using the 64-bit helpers.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  xen/include/asm-arm/arm64/sysregs.h | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
> 
> diff --git a/xen/include/asm-arm/arm64/sysregs.h 
> b/xen/include/asm-arm/arm64/sysregs.h
> index 08585a969e..c60029d38f 100644
> --- a/xen/include/asm-arm/arm64/sysregs.h
> +++ b/xen/include/asm-arm/arm64/sysregs.h
> @@ -59,14 +59,9 @@
>  
>  /* Access to system registers */
>  
> -#define READ_SYSREG32(name) ({                          \
> -    uint32_t _r;                                        \
> -    asm volatile("mrs  %0, "__stringify(name) : "=r" (_r));         \
> -    _r; })
> -#define WRITE_SYSREG32(v, name) do {                    \
> -    uint32_t _r = v;                                    \
> -    asm volatile("msr "__stringify(name)", %0" : : "r" (_r));       \
> -} while (0)
> +#define READ_SYSREG32(name) ((uint32_t)READ_SYSREG64(name))
> +
> +#define WRITE_SYSREG32(v, name) WRITE_SYSREG64((uint64_t)v, name)
>  
>  #define WRITE_SYSREG64(v, name) do {                    \
>      uint64_t _r = v;                                    \
> -- 
> 2.11.0
> 

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