[PATCH v5 1/5] powerpc/sstep: Emulate prefixed instructions only when CPU_FTR_ARCH_31 is set

[Sandipan Das]

On 11/10/20 10:39 am, Ravi Bangoria wrote:
> From: Balamuruhan S <bala24 at linux.ibm.com>
> 
> Unconditional emulation of prefixed instructions will allow
> emulation of them on Power10 predecessors which might cause
> issues. Restrict that.
> 
> Fixes: 3920742b92f5 ("powerpc sstep: Add support for prefixed fixed-point arithmetic")
> Fixes: 50b80a12e4cc ("powerpc sstep: Add support for prefixed load/stores")
> Signed-off-by: Balamuruhan S <bala24 at linux.ibm.com>
> Signed-off-by: Ravi Bangoria <ravi.bangoria at linux.ibm.com>
> ---
>  arch/powerpc/lib/sstep.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index e9dcaba9a4f8..e6242744c71b 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -1346,6 +1346,9 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
>  	switch (opcode) {
>  #ifdef __powerpc64__
>  	case 1:
> +		if (!cpu_has_feature(CPU_FTR_ARCH_31))
> +			return -1;
> +
>  		prefix_r = GET_PREFIX_R(word);
>  		ra = GET_PREFIX_RA(suffix);
>  		rd = (suffix >> 21) & 0x1f;
> @@ -2733,6 +2736,9 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
>  		}
>  		break;
>  	case 1: /* Prefixed instructions */
> +		if (!cpu_has_feature(CPU_FTR_ARCH_31))
> +			return -1;
> +
>  		prefix_r = GET_PREFIX_R(word);
>  		ra = GET_PREFIX_RA(suffix);
>  		op->update_reg = ra;
> 

LGTM

Reviewed-by: Sandipan Das <sandipan at linux.ibm.com>