Re: [PATCH 07/10] target/arm: SCR_EL3.RW should be treated as 1 if EL2 doesn't support AArch32

[Peter Maydell <peter.maydell@linaro.org>]

On Thu, 6 Mar 2025 at 22:54, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 3/6/25 08:39, Peter Maydell wrote:
> > +/* Return the effective value of SCR_EL3.RW */
> > +static inline bool arm_scr_rw_eff(CPUARMState *env)
> > +{
> > +    /*
> > +     * SCR_EL3.RW has an effective value of 1 if:
> > +     *  - we are NS and EL2 is implemented but doesn't support AArch32
> > +     *  - we are S and EL2 is enabled (in which case it must be AArch64)
> > +     */
> > +    ARMCPU *cpu = env_archcpu(env);
> > +    bool ns_and_no_aarch32_el2 = arm_feature(env, ARM_FEATURE_EL2) &&
> > +        (env->cp15.scr_el3 & SCR_NS) &&
> > +        !cpu_isar_feature(aa64_aa32_el1, cpu);
> > +    bool s_and_el2_enabled =
> > +        (env->cp15.scr_el3 & (SCR_NS | SCR_EEL2)) == SCR_EEL2;
> > +
> > +    return ns_and_no_aarch32_el2 || s_and_el2_enabled ||
> > +        (env->cp15.scr_el3 & SCR_RW);
> > +}
>
> The computation here can be simplified.
>
>      if (env->cp15.scr_el3 & SCR_RW) {
>          return true;
>      }
>      if (env->cp15.scr_el3 & SCR_NS) {
>          return arm_feature(env, ARM_FEATURE_EL2) &&
>                 !cpu_isar_feature(aa64_aa32_el1, cpu);
>      } else {
>          return env->cp15.scr_el3 & SCR_EEL2;
>      }

Yes, but at the cost of moving it quite a long
way from how the condition is specified in the Arm ARM...

-- PMM