On Fri, Sep 04, 2015 at 10:44:57AM +0200, Thomas Huth wrote: > On 04/09/15 09:01, David Gibson wrote: > > On Thu, Aug 06, 2015 at 10:57:15AM +0530, Bharata B Rao wrote: > >> QEMU currently supports CPU topologies where there can be cores > >> which are not completely filled with all the threads as per the > >> specifed SMT mode. > >> > >> Restore support for such topologies (Eg -smp 15,cores=4,threads=4) > >> The last core will always have the deficit even when -device options are > >> used to cold-plug the cores. > >> > >> Signed-off-by: Bharata B Rao <bhar...@linux.vnet.ibm.com> > > > > Is there a reason to support these silly toplogies, or should we just > > error out if this is specified?
Only reason was to ensure that existing guest with such topologies continue to boot like before. > > FYI, I've recently submitted a patch that tries to catch such illegal > SMP configurations and simply errors out in that case: > > http://lists.nongnu.org/archive/html/qemu-devel/2015-07/msg04549.html > > It's not upstream yet, but already in Eduardo's x86 branch. I think this > will reject the bad topology from your example, too. It does reject -smp 15,cores=4,threads=4, but with -smp 15,cores=4,threads=4,maxcpus=16, the guest still boots with weird topology. [root@localhost ~]# lscpu Architecture: ppc64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Big Endian CPU(s): 16 On-line CPU(s) list: 0-14 Off-line CPU(s) list: 15 Thread(s) per core: 3 Core(s) per socket: 1 Socket(s): 4 NUMA node(s): 1 Model: IBM pSeries (emulated by qemu) L1d cache: 64K L1i cache: 32K NUMA node0 CPU(s): 0-14 [root@localhost ~]# ppc64_cpu --info Core 0: 0* 1* 2* 3* Core 1: 4* 5* 6* 7* Core 2: 8* 9* 10* 11* Core 3: 12* 13* 14* 15 Should such topologies also be prevented from booting ? Regards, Bharata.
