Cédric Le Goater <c...@kaod.org> writes: > 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. Otherwise, I see that multiple chips are created with >> single core having single thread. >> >> ppc/pnv: Use num_chips for multiple sockets >> >> When the user does not provide the cpu topology, e.g. "-smp 4", machine >> fails to >> initialize 4 cpus. QEMU assumes smp_threads and smp_cores both as 1. >> Make sure >> that we initialize multiple chips for this. > > -smp 4 would give a machine with 4 sockets with 1 core > -smp 4,cores=4 would give a machine with 1 socket with 4 cores > > correct ?
Yes Regards Nikunj
