Re: [Qemu-devel] [Qemu-ppc] [PATCH] pseries: do not allow memory-less/cpu-less NUMA node

[Greg Kurz <groug@kaod.org>]

On Fri, 30 Aug 2019 17:34:13 +0100
Daniel P. Berrangé <berrange@redhat.com> wrote:

> On Fri, Aug 30, 2019 at 06:13:45PM +0200, Laurent Vivier wrote:
> > When we hotplug a CPU on memory-less/cpu-less node, the linux kernel
> > crashes.
> > 
> > This happens because linux kernel needs to know the NUMA topology at
> > start to be able to initialize the distance lookup table.
> > 
> > On pseries, the topology is provided by the firmware via the existing
> > CPUs and memory information. Thus a node without memory and CPU cannot be
> > discovered by the kernel.
> > 
> > To avoid the kernel crash, do not allow to start pseries with empty
> > nodes.
> 
> This describes one possible guest OS. Is there any reasonable chance
> that a non-Linux guest might be able to handle this situation correctly,
> or do you expect any guest to have the same restriction ?
> 

I can try to grab an AIX image and give a try, but anyway this looks like
a very big hammer to me... :-\

> > Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> > ---
> >  hw/ppc/spapr.c | 33 +++++++++++++++++++++++++++++++++
> >  1 file changed, 33 insertions(+)
> 
> Regards,
> Daniel