Re: [Qemu-devel] [PATCH v5 02/33] target-arm: add arm_is_secure() function

[Sergey Fedorov <serge.fdrv@gmail.com>]

On 06.10.2014 07:56, Peter Maydell wrote:
> On 30 September 2014 22:49, Greg Bellows <greg.bellows@linaro.org> wrote:
>> From: Fabian Aggeler <aggelerf@ethz.ch>
>>
>> arm_is_secure() function allows to determine CPU security state
>> if the CPU implements Security Extensions/EL3.
>> arm_is_secure_below_el3() returns true if CPU is in secure state
>> below EL3.
>>
>> Signed-off-by: Sergey Fedorov <s.fedorov@samsung.com>
>> Signed-off-by: Fabian Aggeler <aggelerf@ethz.ch>
>> Signed-off-by: Greg Bellows <greg.bellows@linaro.org>
>> ---
>>  target-arm/cpu.h | 38 ++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 38 insertions(+)
>>
>> diff --git a/target-arm/cpu.h b/target-arm/cpu.h
>> index 81fffd2..10afef0 100644
>> --- a/target-arm/cpu.h
>> +++ b/target-arm/cpu.h
>> @@ -753,6 +753,44 @@ static inline int arm_feature(CPUARMState *env, int feature)
>>      return (env->features & (1ULL << feature)) != 0;
>>  }
>>
>> +
>> +/* Return true if exception level below EL3 is in secure state */
>> +static inline bool arm_is_secure_below_el3(CPUARMState *env)
>> +{
>> +#if !defined(CONFIG_USER_ONLY)
>> +    if (arm_feature(env, ARM_FEATURE_EL3)) {
>> +        return !(env->cp15.scr_el3 & SCR_NS);
>> +    } else if (arm_feature(env, ARM_FEATURE_EL2)) {
>> +        return false;
>> +    } else {
>> +        /* IMPDEF: QEMU defaults to non-secure */
>> +        return false;
> I would be happy to fold both these identical 'return false'
> cases together and have a comment that it's only IMPDEF
> if EL2 isn't implemented.
>
>> +    }
>> +#else
>> +    return false;
>> +#endif
>> +}
>> +
>> +/* Return true if the processor is in secure state */
>> +static inline bool arm_is_secure(CPUARMState *env)
>> +{
>> +#if !defined(CONFIG_USER_ONLY)
>> +    if (arm_feature(env, ARM_FEATURE_EL3)) {
>> +        if (env->aarch64 && extract32(env->pstate, 2, 2) == 3) {
>> +            /* CPU currently in Aarch64 state and EL3 */
> Nit: "AArch64" with two capital 'A's (here and elsewhere).
>
>> +            return true;
>> +        } else if (!env->aarch64 &&
>> +                (env->uncached_cpsr & CPSR_M) == ARM_CPU_MODE_MON) {
>> +            /* CPU currently in Aarch32 state and monitor mode */
>> +            return true;
>> +        }
>> +    }
>> +    return arm_is_secure_below_el3(env);
>> +#else
>> +    return false;
>> +#endif
>> +}
> I checked your git tree and we don't actually use
> arm_is_secure_below_el3() anywhere except in
> arm_is_secure(), do we? That suggests to me we should
> just fold the two functions together.
>
> Can these functions live in internals.h rather than cpu.h?
> (The difference is that internals.h is restricted to only
> target-arm/ code whereas cpu.h is auto-included for a much
> wider set of files.)

Probably arm_is_secure() would be used by ARM GIC emulation until there
is no better way to determine memory transaction NS tag.

>
> thanks
> -- PMM