Re: [PATCH 1/3] target/arm: Add support for FEAT_SSBS, Speculative Store Bypass Safe

[Richard Henderson]

On 2/15/21 1:58 PM, Rebecca Cran wrote:
> @@ -960,6 +960,12 @@ static void cpsr_write_from_spsr_elx(CPUARMState *env,
>          val |= CPSR_DIT;
>      }
>  
> +    /* Move SSBS to the correct location for CPSR */
> +    if (val & PSTATE_SSBS) {
> +        val &= ~PSTATE_SSBS;
> +        val |= CPSR_SSBS;
> +    }

Incorrect.  SPSR_ELx leaves this at the same position as CPSR: bit 23.

>          }
> +
> +        if (cpu_isar_feature(aa32_ssbs, env_archcpu(env))) {
> +            if (env->cp15.sctlr_el[new_el] & SCTLR_DSSBS_32) {
> +                env->uncached_cpsr |= CPSR_SSBS;
> +            } else {
> +                env->uncached_cpsr &= ~CPSR_SSBS;
> +            }
> +        }

Hoist this so that it can be shared with the HYP branch (hsctlr is mapped to
sctlr_el[2] and HYP maps to el=2).

> @@ -9809,6 +9846,13 @@ static uint32_t cpsr_read_for_spsr_elx(CPUARMState 
> *env)
>          ret &= ~CPSR_DIT;
>          ret |= PSTATE_DIT;
>      }
> +
> +    /* Move SSBS to the correct location for SPSR_ELx */
> +    if (ret & CPSR_SSBS) {
> +        ret &= ~CPSR_SSBS;
> +        ret |= PSTATE_SSBS;
> +    }

Incorrect, like in cpsr_write_from_spsr_elx.

> diff --git a/target/arm/translate-a64.c b/target/arm/translate-a64.c
> index 1c4b8d02f3b8..2372d55ea18b 100644
> --- a/target/arm/translate-a64.c
> +++ b/target/arm/translate-a64.c
> @@ -1712,6 +1712,18 @@ static void handle_msr_i(DisasContext *s, uint32_t 
> insn,
>          /* There's no need to rebuild hflags because DIT is a nop */
>          break;
>  
> +    case 0x19: /* SSBS */
> +        if (!dc_isar_feature(aa64_ssbs, s)) {
> +            goto do_unallocated;
> +        }
> +        if (crm & 1) {
> +            set_pstate_bits(PSTATE_SSBS);
> +        } else {
> +            clear_pstate_bits(PSTATE_SSBS);
> +        }
> +        /* Don't need to rebuild hflags since SSBS is a nop */
> +        break;

Put this above DIT (0x1a) to keep the numbers in order.


r~