Re: [kvm-unit-tests PATCH v3 6/9] s390x: smp: Loop if secondary cpu returns into cpu setup again

David Hildenbrand
2020-01-20T12:08:10Z

On 20.01.20 12:27, Cornelia Huck wrote:
> On Fri, 17 Jan 2020 05:46:37 -0500
> Janosch Frank <frankja@linux.ibm.com> wrote:
>
>> Up to now a secondary cpu could have returned from the function it was
>> executing and ending up somewhere in cstart64.S. This was mostly
>> circumvented by an endless loop in the function that it executed.
>>
>> Let's add a loop to the end of the cpu setup, so we don't have to rely
>> on added loops in the tests.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> ---
>> s390x/cstart64.S | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/s390x/cstart64.S b/s390x/cstart64.S
>> index 9af6bb3..5fd8d2f 100644
>> --- a/s390x/cstart64.S
>> +++ b/s390x/cstart64.S
>> @@ -162,6 +162,8 @@ smp_cpu_setup_state:
>> /* We should only go once through cpu setup and not for every restart */
>> stg %r14, GEN_LC_RESTART_NEW_PSW + 8
>> br %r14
>> + /* If the function returns, just loop here */
>> +0: j 0
>
> Would it make sense to e.g. load a disabled wait psw instead? Or does
> that mess things up elsewhere?

I think we can keep it like that for now (simpler than loading a PSW).
Overall, I don't care about burning CPU cycles here :)

--
Thanks,

David / dhildenb