Re: [Qemu-devel] [PATCH] ppc/pnv: fix cores per chip for multiple cpus

[Nikunj A Dadhania]

Nikunj A Dadhania <address@hidden> writes:

>> >> 
>>> >> I think the current approach is the simplest and less intrusive, as we
>>> >> are handling a case where user has not bothered to provide a detailed
>>> >> topology, the best we can do is create single threaded cores equal to
>>> >> number of cores.
>>> >
>>> > No, sorry.  Having smp_cores not correspond to the number of cores per
>>> > chip in all cases is just not ok.  Add an error message if the
>>> > topology isn't workable for powernv by all means.  But users having to
>>> > use a longer command line is better than breaking basic assumptions
>>> > about what numbers reflect what topology.
>>> 
>>> Sorry to ask again, as I am still not convinced, we do similar
>>> adjustment in spapr where the user did not provide the number of cores,
>>> but qemu assumes them as single threaded cores and created
>>> cores(boot_cores_nr) that were not same as smp_cores ?
>>
>> What?  boot_cores_nr has absolutely nothing to do with adjusting the
>> topology, and it certainly doesn't assume they're single threaded.
>
> When we start a TCG guest and user provides following commandline,
> e.g. "-smp 4", smt_threads is set to 1 by default in vl.c.

I meant smp_threads here.

> So the guest boots with 4 cores, each having 1 thread.
>
> Regards
> Nikunj