Re: [PATCH] powerpc: add PPC_FEATURE userspace bits for SCV and DARN instructions

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Sat, 2017-05-20 at 14:29 +1000, Nicholas Piggin wrote:
> Providing "scv" support to userspace requires kernel support, so it
> must be advertised as independently to the base ISA 3 instruction set.
> 
> The darn instruction relies on firmware enablement, so it has been
> decided to split this out from the core ISA 3 feature as well.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> ---
> These uapi changes have been agreed by powerpc toolchain and firmware
> teams. I believe this completes our anticipated requirements for user
> feature advertisement for ISA v3.0B.
> 
>  arch/powerpc/include/uapi/asm/cputable.h | 2 ++
>  arch/powerpc/kernel/cputable.c           | 3 ++-
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/uapi/asm/cputable.h b/arch/powerpc/include/uapi/asm/cputable.h
> index 3e7ce86d5c13..4d877144f377 100644
> --- a/arch/powerpc/include/uapi/asm/cputable.h
> +++ b/arch/powerpc/include/uapi/asm/cputable.h
> @@ -46,6 +46,8 @@
>  #define PPC_FEATURE2_HTM_NOSC		0x01000000
>  #define PPC_FEATURE2_ARCH_3_00		0x00800000 /* ISA 3.00 */
>  #define PPC_FEATURE2_HAS_IEEE128	0x00400000 /* VSX IEEE Binary Float 128-bit */
> +#define PPC_FEATURE2_DARN		0x00200000 /* darn random number insn */
> +#define PPC_FEATURE2_SCV		0x00100000 /* scv syscall */
>  
>  /*
>   * IMPORTANT!
> diff --git a/arch/powerpc/kernel/cputable.c b/arch/powerpc/kernel/cputable.c
> index 9b3e88b1a9c8..6f849832a669 100644
> --- a/arch/powerpc/kernel/cputable.c
> +++ b/arch/powerpc/kernel/cputable.c
> @@ -124,7 +124,8 @@ extern void __restore_cpu_e6500(void);
>  #define COMMON_USER_POWER9	COMMON_USER_POWER8
>  #define COMMON_USER2_POWER9	(COMMON_USER2_POWER8 | \
>  				 PPC_FEATURE2_ARCH_3_00 | \
> -				 PPC_FEATURE2_HAS_IEEE128)
> +				 PPC_FEATURE2_HAS_IEEE128 | \
> +				 PPC_FEATURE2_DARN )
>  
>  #ifdef CONFIG_PPC_BOOK3E_64
>  #define COMMON_USER_BOOKE	(COMMON_USER_PPC64 | PPC_FEATURE_BOOKE)