Re: [PATCH v19 01/21] s390x/cpu topology: add s390 specifics to CPU topology

[Pierre Morel <pmorel@linux.ibm.com>]

On 4/18/23 12:15, Thomas Huth wrote:
> On 18/04/2023 12.01, Pierre Morel wrote:
>>
>> On 4/18/23 10:53, Nina Schoetterl-Glausch wrote:
>>> On Mon, 2023-04-03 at 18:28 +0200, Pierre Morel wrote:
>>>> S390 adds two new SMP levels, drawers and books to the CPU
>>>> topology.
>>>> The S390 CPU have specific topology features like dedication
>>>> and entitlement to give to the guest indications on the host
>>>> vCPUs scheduling and help the guest take the best decisions
>>>> on the scheduling of threads on the vCPUs.
>>>>
>>>> Let us provide the SMP properties with books and drawers levels
>>>> and S390 CPU with dedication and entitlement,
>>>>
>>>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>>>> Reviewed-by: Thomas Huth <thuth@redhat.com>
>>>> ---
>>>>   MAINTAINERS                     |  5 ++++
>>>>   qapi/machine-common.json        | 22 ++++++++++++++
>>>>   qapi/machine-target.json        | 12 ++++++++
>>>>   qapi/machine.json               | 17 +++++++++--
>>>>   include/hw/boards.h             | 10 ++++++-
>>>>   include/hw/s390x/cpu-topology.h | 15 ++++++++++
>>> Is hw/s390x the right path for cpu-topology?
>>> I haven't understood the difference between hw/s390x and target/s390x
>>> but target/s390x feels more correct, I could be mistaken though.
>>
>> AFAIK target/s390 is for CPU emulation code while hw/s390 is for 
>> other emulation.
>>
>> So it depends how we classify the CPU topology, it is related to CPU 
>> but it is no emulation.
>
> Normally I'd say target/ is for everything what happens within a CPU 
> chip, and hw/ is for everything that happens outside of a CPU chip, 
> i.e. machine definitions and other devices.
> Now CPU topology is borderline - drawers and books are rather a 
> concept of the machine and not of the CPU, but things like dies and 
> threads rather happen within a CPU chip.
> So I don't mind too much either way, but I think it's certainly ok to 
> keep it in hw/s390x/ if you prefer that.
>
>  Thomas
>
Thanks for the clarification Thomas.

Pierre