Re: [RFC v3 PATCH 13/14] aarch64: Generate fences for aarch64

["Alex Bennée" <alex.bennee@linaro.org>]

Pranith Kumar <bobby.prani@gmail.com> writes:

> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
> ---
>  target-arm/translate-a64.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
> index ce8141a..fa24bf2 100644
> --- a/target-arm/translate-a64.c
> +++ b/target-arm/translate-a64.c
> @@ -1250,7 +1250,7 @@ static void handle_sync(DisasContext *s, uint32_t insn,
>          return;
>      case 4: /* DSB */
>      case 5: /* DMB */
> -        /* We don't emulate caches so barriers are no-ops */
> +        tcg_gen_mb(TCG_MO_ALL | TCG_BAR_SC);
>          return;
>      case 6: /* ISB */
>          /* We need to break the TB after this insn to execute
> @@ -1855,23 +1855,31 @@ static void disas_ldst_excl(DisasContext *s, uint32_t insn)
>      }
>      tcg_addr = read_cpu_reg_sp(s, rn, 1);
>
> -    /* Note that since TCG is single threaded load-acquire/store-release
> -     * semantics require no extra if (is_lasr) { ... } handling.
> -     */
> -
>      if (is_excl) {
>          if (!is_store) {
>              s->is_ldex = true;
>              gen_load_exclusive(s, rt, rt2, tcg_addr, size, is_pair);
> +            if (is_lasr) {
> +                tcg_gen_mb(TCG_MO_ALL | TCG_BAR_ACQ);
> +            }
>          } else {
> +            if (is_lasr) {
> +                tcg_gen_mb(TCG_MO_ALL | TCG_BAR_REL);
> +            }
>              gen_store_exclusive(s, rs, rt, rt2, tcg_addr, size, is_pair);
>          }
>      } else {
>          TCGv_i64 tcg_rt = cpu_reg(s, rt);
>          if (is_store) {
> +            if (is_lasr) {
> +                tcg_gen_mb(TCG_MO_ALL | TCG_BAR_REL);
> +            }
>              do_gpr_st(s, tcg_rt, tcg_addr, size);
>          } else {
>              do_gpr_ld(s, tcg_rt, tcg_addr, size, false, false);
> +            if (is_lasr) {
> +                tcg_gen_mb(TCG_MO_ALL | TCG_BAR_ACQ);
> +            }

See the private email I sent you with the litmus tests. I think you'll
need to confirm this is working as expected.

>          }
>      }
>  }


--
Alex Bennée