Re: [Qemu-arm] [PATCH v2 2/6] target-arm: Fix handling of SCR.SMD

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Thu, Feb 11, 2016 at 04:03:25PM +0000, Peter Maydell wrote:
> We weren't quite implementing the handling of SCR.SMD correctly.
> The condition governing whether the SMD bit should apply only
> for NS state is "is EL3 is AArch32", not "is the current EL AArch32".
> Fix the condition, and clarify the comment both to reflect this and
> to expand slightly on what's going on for the v7-no-Virtualization case.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Sergey Fedorov <serge.fdrv@gmail.com>

Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>



> ---
> The bit about forcing SMD to zero confused me, anyway, since I
> expected it to mean "in this function", not elsewhere...
> ---
>  target-arm/op_helper.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
> index bd48549..4c0980e 100644
> --- a/target-arm/op_helper.c
> +++ b/target-arm/op_helper.c
> @@ -614,12 +614,14 @@ void HELPER(pre_smc)(CPUARMState *env, uint32_t syndrome)
>      int cur_el = arm_current_el(env);
>      bool secure = arm_is_secure(env);
>      bool smd = env->cp15.scr_el3 & SCR_SMD;
> -    /* On ARMv8 AArch32, SMD only applies to NS state.
> -     * On ARMv7 SMD only applies to NS state and only if EL2 is available.
> -     * For ARMv7 non EL2, we force SMD to zero so we don't need to re-check
> -     * the EL2 condition here.
> +    /* On ARMv8 with EL3 AArch64, SMD applies to both S and NS state.
> +     * On ARMv8 with EL3 AArch32, or ARMv7 with the Virtualization
> +     *  extensions, SMD only applies to NS state.
> +     * On ARMv7 without the Virtualization extensions, the SMD bit
> +     * doesn't exist, but we forbid the guest to set it to 1 in scr_write(),
> +     * so we need not special case this here.
>       */
> -    bool undef = is_a64(env) ? smd : (!secure && smd);
> +    bool undef = arm_feature(env, ARM_FEATURE_AARCH64) ? smd : smd && !secure;
>  
>      if (arm_is_psci_call(cpu, EXCP_SMC)) {
>          /* If PSCI is enabled and this looks like a valid PSCI call then
> -- 
> 1.9.1
>