On 18/03/2016 11:06, Thomas Huth wrote:
> On 18.03.2016 11:01, Laurent Vivier wrote:
...
>>>> + /* doc says it is invalid, real proc stops when it comes to
>>>> + * overwrite the register.
>>>> + * In all the cases, the register must stay untouched
>>>> + */
>>>> + report("Don't overwrite Rb", regs[1] == (uint64_t)addr);
>>>
>>> Huh, how can this KVM unit test ever finish successfully if real
>>> processor stops? Should this last test maybe be optional and only be
>>> triggered if this kvm-unit-test is run with certain parameters?
>>
>> Well, my bad, I've not been accurate: the processor doesn't stop, but
>> the processing of the instruction is stopped. Only registers until Rb
>> (not included) are updated, and then the processor continue with the
>> next instruction. So we have just to test Rb is not modified. I'll
>> update the comment.
>
> Ok, now I've got it, I think. Maybe you should also check the
> "is_invalid" variable here? And it would also be interesting to see
> whether regs[0] (i.e. r31) has been changed or not?
In fact, I've tested this with kvm PR and HV, on POWER8 and ppc970, and
there is never an illegal exception. It's why I don't check that.
Checking regs[1] is correct in the case of the doc (illegal instruction)
and of the real processor (it doesn't update it).
Checking regs[0] can be tricky: in the case of the doc (illegal) it
should not be updated, in the case of the real processor it is updated.
I'd like this test checks only if TCG behaves like a real processor,
it's why I prefer to check this result against the result of a real
processor than against the result described in the doc.
Laurent
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