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

[David Gibson <david@gibson.dropbear.id.au>]

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On Mon, Sep 11, 2017 at 10:40:10AM +0530, Nikunj A Dadhania wrote:
> David Gibson <david@gibson.dropbear.id.au> writes:
> 
> > On Wed, Sep 06, 2017 at 01:57:48PM +0530, Nikunj A Dadhania wrote:
> >> When the user does not provide the cpu topology, e.g. "-smp 4", machine fails to
> >> initialize 4 cpus. Compute the chip per cores depending on the number of chips
> >> and smt threads.
> >> 
> >> Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
> >
> > I don't understand why simply treating smp_cores as cores per chip is wrong.
> 
> We do not have SMT support and when "-smp 4" is passed, smp_cores is
> always set to 1. So only once core with one thread finally show up in
> the guest. Moreover, I see spapr too doing similar thing in
> spapr_init_cpus() with boot_cores_nr.

I'm ok with adding an error if smp_threads > 1, since that won't
work.  Breaking the identity that smp_cores is the number of cores per
socket (which should correspond to one chip) is not ok, though.

I think you're misinterpreting the boot_cores_nr stuff - that's just
about translating the number of initially online vcpus into a number
of initially online cores.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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