Re: [PATCH v1 2/9] s390x: toplogy: adding drawers and books to smp parsing

[Cornelia Huck]

On Fri, Jul 16 2021, Daniel P. Berrangé <berrange@redhat.com> wrote:

> On Fri, Jul 16, 2021 at 11:10:04AM +0200, Cornelia Huck wrote:
>> On Thu, Jul 15 2021, Markus Armbruster <armbru@redhat.com> wrote:
>> 
>> > Pierre Morel <pmorel@linux.ibm.com> writes:
>> >
>> >> On 7/15/21 8:16 AM, Markus Armbruster wrote:
>> >>> Pierre Morel <pmorel@linux.ibm.com> writes:
>> >>> 
>> >>>> Drawers and Books are levels 4 and 3 of the S390 CPU
>> >>>> topology.
>> >>>> We allow the user to define these levels and we will
>> >>>> store the values inside the S390CcwMachineState.
>> >>> 
>> >>> Double-checking: are these members specific to S390?
>> >>
>> >> Yes AFAIK
>> >
>> > Makes me wonder whether they should be conditional on TARGET_S390X.
>> >
>> > What happens when you specify them for another target?  Silently
>> > ignored, or error?
>> 
>> I'm wondering whether we should include them in the base machine state
>> and treat them as we treat 'dies' (i.e. the standard parser errors out
>> if they are set, and only the s390x parser supports them.)
>
> To repeat what i just wrote in my reply to patch 1, I think we ought to
> think  about a different approach to handling the usage constraints,
> which doesn't require full re-implementation of the smp_parse method
> each time.  There should be a way for each target to report topology
> constraints, such the the single smp_parse method can do the right
> thing, especially wrt error reporting for unsupported values.

That would mean that all possible fields would need to go into common
code, right?

I'm wondering whether there are more architecture/cpu specific values
lurking in the corner, it would get unwieldy if we need to go beyond the
existing fields and drawers/books.