Re: [PATCH v2 5/6] target/arm/helper: Check SCR_EL3.{NSE, NS} encoding for AT instructions

[Peter Maydell]

On Wed, 2 Aug 2023 at 18:02, Jean-Philippe Brucker
<jean-philippe@linaro.org> wrote:
>
> The AT instruction is UNDEFINED if the {NSE,NS} configuration is
> invalid. Add a function to check this on all AT instructions that apply
> to an EL lower than 3.
>
> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
>  target/arm/helper.c | 36 +++++++++++++++++++++++++-----------
>  1 file changed, 25 insertions(+), 11 deletions(-)
>
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index fbb03c364b..77dd80ad28 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -3616,6 +3616,20 @@ static void ats1h_write(CPUARMState *env, const 
> ARMCPRegInfo *ri,
>  #endif /* CONFIG_TCG */
>  }
>
> +static CPAccessResult at_e012_access(CPUARMState *env, const ARMCPRegInfo 
> *ri,
> +                                     bool isread)
> +{
> +    /*
> +     * R_NYXTL: instruction is UNDEFINED if it applies to an Exception level
> +     * lower than EL3 and the combination SCR_EL3.{NSE,NS} is reserved.
> +     */
> +    if (cpu_isar_feature(aa64_rme, env_archcpu(env)) &&
> +        (env->cp15.scr_el3 & (SCR_NSE | SCR_NS)) == SCR_NSE) {
> +        return CP_ACCESS_TRAP;
> +    }

The AArch64.AT() pseudocode and the text in the individual
AT insn descriptions ("When FEAT_RME is implemented, if the Effective
value of SCR_EL3.{NSE, NS} is a reserved value, this instruction is
UNDEFINED at EL3") say that this check needs an "arm_current_el(env) == 3"
condition too.

> +    return CP_ACCESS_OK;
> +}
> +
>  static CPAccessResult at_s1e2_access(CPUARMState *env, const ARMCPRegInfo 
> *ri,
>                                       bool isread)
>  {

thanks
-- PMM