Re: [PATCH] target/s390x: Add a CONFIG switch to disable legacy CPUs

[Thomas Huth <thuth@redhat.com>]

On 14/06/2024 10.17, Christian Borntraeger wrote:
> 
> 
> Am 14.06.24 um 09:15 schrieb Thomas Huth:
>> On 14/06/2024 08.07, Christian Borntraeger wrote:
>>>
>>>
>>> Am 13.06.24 um 19:07 schrieb Thomas Huth:
>>>> Old CPU models are not officially supported anymore by IBM, and for
>>>> downstream builds of QEMU, we would like to be able to disable these
>>>> CPUs in the build. Thus add a CONFIG switch that can be used to
>>>> disable these CPUs (and old machine types that use them by default).
>>>>
>>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>>> ---
>>>>   If you're interested, the PDF that can be downloaded from
>>>>   https://www.ibm.com/support/pages/ibm-mainframe-life-cycle-history
>>>>   shows the supported CPUs in a nice diagram
>>>
>>> z13 is still supported so the patch needs to be fixed at least.
>>
>> Oh, drat, I misread the diagram, indeed. 'should have looked at the table 
>> instead :-/
>>
>>> Furthermore, z14 has the IBC/VAL cabability to behave like a z13,
>>> same for z15. (we do support VAL to N-2)
>>
>> Hmm, so if z13 is still supported, and also has the possibility to do N-2, 
>> I assume the z114/196 and z12 should still be considered as non-legacy, too?
> 
> Yes. z9 and older is no longer relevant (only for people that collect old 
> HW) but the upstream kernel has an minimum requirement for z10 so maybe we 
> still want to support that for testing purposes.

Ok, fair point, kernel support is a good hint, too.

> For upstream I prefer to keep the full list but I would be ok to hide those 
> ancient things behind a config switch.

That's what this patch is trying to do - by default, all CPUs are still 
enabled, you have actively disable the switch to get rid of the old ones.

  Thomas