Re: [PATCH v4 3/5] powerpc/lib/sstep: Add bpermd instruction emulation

[Cyril Bur]

On Mon, 2017-07-31 at 10:58 +1000, Matt Brown wrote:
> This adds emulation for the bpermd instruction.
> Tested for correctness against the bpermd instruction on ppc64le.
> 
> Signed-off-by: Matt Brown <matthew.brown....@gmail.com>

Reviewed-by: Cyril Bur <cyril...@gmail.com>

> ---
> v4:
>       - change ifdef macro from __powerpc64__ to CONFIG_PPC64
> v2:
>       - fixed opcode
>       - added ifdef tags to do_bpermd func
>       - fixed bitshifting errors
> ---
>  arch/powerpc/lib/sstep.c | 24 +++++++++++++++++++++++-
>  1 file changed, 23 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index 2fd7377..c9fd613 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -640,6 +640,24 @@ static nokprobe_inline void do_popcnt(struct pt_regs 
> *regs, unsigned long v1,
>       regs->gpr[ra] = out;    /* popcntd */
>  }
>  
> +#ifdef CONFIG_PPC64
> +static nokprobe_inline void do_bpermd(struct pt_regs *regs, unsigned long v1,
> +                             unsigned long v2, int ra)
> +{
> +     unsigned char perm, idx;
> +     unsigned int i;
> +
> +     perm = 0;
> +     for (i = 0; i < 8; i++) {
> +             idx = (v1 >> (i * 8)) & 0xff;
> +             if (idx < 64)
> +                     if (v2 & PPC_BIT(idx))
> +                             perm |= 1 << i;
> +     }
> +     regs->gpr[ra] = perm;
> +}
> +#endif /* CONFIG_PPC64 */
> +
>  static nokprobe_inline int trap_compare(long v1, long v2)
>  {
>       int ret = 0;
> @@ -1229,7 +1247,11 @@ int analyse_instr(struct instruction_op *op, struct 
> pt_regs *regs,
>               case 124:       /* nor */
>                       regs->gpr[ra] = ~(regs->gpr[rd] | regs->gpr[rb]);
>                       goto logical_done;
> -
> +#ifdef CONFIG_PPC64
> +             case 252:       /* bpermd */
> +                     do_bpermd(regs, regs->gpr[rd], regs->gpr[rb], ra);
> +                     goto logical_done;
> +#endif
>               case 284:       /* xor */
>                       regs->gpr[ra] = ~(regs->gpr[rd] ^ regs->gpr[rb]);
>                       goto logical_done;