On Fri, Sep 22, 2017 at 08:07:06AM +0200, Cédric Le Goater wrote: > On 09/22/2017 08:00 AM, Nikunj A Dadhania wrote: > > David Gibson <da...@gibson.dropbear.id.au> writes: > > > >>>>> > >>>>> As smp_thread defaults to 1 in vl.c, similarly smp_cores also has the > >>>>> default value of 1 in vl.c. In powernv, we were setting nr-cores like > >>>>> this: > >>>>> > >>>>> object_property_set_int(chip, smp_cores, "nr-cores", > >>>>> &error_fatal); > >>>>> > >>>>> Even when there were multiple cpus (-smp 4), when the guest boots up, we > >>>>> just get one core (i.e. smp_cores was 1) with single thread(smp_threads > >>>>> was 1), which is wrong as per the command-line that was provided. > >>>> > >>>> Right, so, -smp 4 defaults to 4 sockets, each with 1 core of 1 > >>>> thread. If you can't supply 4 sockets you should error, but you > >>>> shouldn't go and change the number of cores per socket. > >>> > >>> OK, that makes sense now. And I do see that smp_cpus is 4 in the above > >>> case. Now looking more into it, i see that powernv has something called > >>> "num_chips", isnt this same as sockets ? Do we need num_chips separately? > >> > >> Ah, yes, I see. It's probably still reasonable to keep num_chips as > >> an internal variable, rather than using (smp_cpus / smp_cores / > >> smp_threads) everywhere. But we shouldn't have it as a direct > >> user-settable property, instead setting it from the -smp command line > >> option. > > > > Something like the below works till num_chips=2, after that guest does > > not boot up. This might be some limitation within the OS, Cedric might > > have some clue. > > Some controllers might need some more tweaking, PSI, LPC, to elect a > master one.
Uh.. why?
> Anyhow I don't think we want to deduce the number of chips
> from the number of cpus. These two figures are very different.
How so? It's not totally perfect, but making a single chip correspond
to a "socket" in qemu's (somewhat x86 centric) terminology is still a
pretty good match.
--
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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