Re: [kvm-unit-tests PATCH v6 07/10] s390x: css: msch, enable test

Pierre Morel
2020-05-15T07:11:59Z

On 2020-05-14 14:08, Cornelia Huck wrote:
> On Tue, 28 Apr 2020 10:27:36 +0200
> Pierre Morel <pmorel@linux.ibm.com> wrote:
>
>> On 2020-04-27 15:11, Janosch Frank wrote:
>>> On 4/24/20 12:45 PM, Pierre Morel wrote:
>
>>>> This is NOT a routine to really enable the channel, no retry is done,
>>>> in case of error, a report is made.
>>>
>>> Would we expect needing retries for the pong device?
>>
>> Yes it can be that we need to retry some instructions if we want them to
>> succeed.
>> This is the case for example if we develop a driver for an operating system.
>> When working with firmware, sometime, things do not work at the first
>> time. Mostly due to races in silicium, firmware or hypervisor or between
>> them all.
>>
>> Since our purpose is to detect such problems we do not retry
>> instructions but report the error.
>>
>> If we detect such problem we may in the future enhance the tests.
>
> I think I've seen retries needed on z/VM in the past; do you know if
> that still happens?
>

I did not try the tests under z/VM, nor direct on an LPAR, only under
QEMU/KVM.
Under QEMU/KVM, I did not encounter any need for retry, 100% of the
enabled succeeded on first try.

Regards,
Pierre

--
Pierre Morel
IBM Lab Boeblingen