Re: [PATCH v3 08/20] target/arm: Remove CPSR_RESERVED

[Richard Henderson]

On 2/7/20 5:36 PM, Peter Maydell wrote:
>> -    return cpsr_read(env) & ~(CPSR_EXEC | CPSR_RESERVED);
>> +    /*
>> +     * We store the ARMv8 PSTATE.SS bit in env->uncached_cpsr.
>> +     * This is convenient for populating SPSR_ELx, but must be
>> +     * hidden from aarch32 mode, where it is not visible.
>> +     *
>> +     * TODO: ARMv8.4-DIT -- need to move SS somewhere else.
>> +     */
>> +    return cpsr_read(env) & ~(CPSR_EXEC | PSTATE_SS);
> 
> So previously we were masking out [23:21], and now we only mask
> out [21]. Is this OK because we've now masked everywhere that
> might have been able to write non-zero to [23:22] ?

Yes.

On the chance that I've missed one, we'll now call anything that fails to do so
a bug there, and not here.  ;-)

> (regarding the TODO comment, I guess the obvious place would
> be env->pstate.)

That was my thought too.  That env->pstate & PSTATE_SS would be where we leave
that bit all of the time, even when the rest of pstate is inactive in aa32 mode.


r~