On Fri, 2016-06-24 at 13:18 -0700, Aaron Larson wrote:
> Call gen_pause for all "or rx,rx,rx" encodings other nop. This
> provides a reasonable implementation for yield, and a better
> approximation for mdoio, mdoom, and miso. The choice to pause for
> all
> encodings !=0 leverages the PowerISA admonition that the reserved
> encodings might change program priority, providing a slight "future
> proofing".
>
> Signed-off-by: Aaron Larson <alar...@ddci.com>
Acked-by: Benjamin Herrenschmidt <b...@kerne.crashing.org>
> ---
> target-ppc/translate.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index 2f1c591..c4559b6 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -1471,7 +1471,7 @@ static void gen_or(DisasContext *ctx)
> } else if (unlikely(Rc(ctx->opcode) != 0)) {
> gen_set_Rc0(ctx, cpu_gpr[rs]);
> #if defined(TARGET_PPC64)
> - } else {
> + } else if (rs != 0) { /* 0 is nop */
> int prio = 0;
>
> switch (rs) {
> @@ -1514,7 +1514,6 @@ static void gen_or(DisasContext *ctx)
> break;
> #endif
> default:
> - /* nop */
> break;
> }
> if (prio) {
> @@ -1524,13 +1523,15 @@ static void gen_or(DisasContext *ctx)
> tcg_gen_ori_tl(t0, t0, ((uint64_t)prio) << 50);
> gen_store_spr(SPR_PPR, t0);
> tcg_temp_free(t0);
> - /* Pause us out of TCG otherwise spin loops with smt_low
> - * eat too much CPU and the kernel hangs
> - */
> + }
> #if !defined(CONFIG_USER_ONLY)
> - gen_pause(ctx);
> + /* Pause out of TCG otherwise spin loops with smt_low eat
> too much
> + * CPU and the kernel hangs. This applies to all encodings
> other
> + * than no-op, e.g., miso(rs=26), yield(27), mdoio(29),
> mdoom(30),
> + * and all currently undefined.
> + */
> + gen_pause(ctx);
> #endif
> - }
> #endif
> }
> }
