Re: [Qemu-devel] [PATCH v1] numa: s390x has no NUMA

[David Hildenbrand]

On 26.02.2018 10:20, Christian Borntraeger wrote:
> 
> 
> On 02/23/2018 06:36 PM, David Hildenbrand wrote:
>> Right now it is possible to crash QEMU for s390x by providing e.g.
>>     -numa node,nodeid=0,cpus=0-1
>>
>> Problem is, that numa.c uses mc->cpu_index_to_instance_props as an
>> indicator whether NUMA is supported by a machine type. We don't
>> implement NUMA on s390x (and that concept also doesn't really exist).
>> We need mc->cpu_index_to_instance_props for query-cpus.
> 
> Looks like we assert because of 
> machine->possible_cpus == 0.
> 
> Later during boot this is created in s390_possible_cpu_arch_ids. (via 
> s390_init_cpus). What we (in the future) actually could provide is a 
> cpu topology.
> 
> So something like this also fixes the bug

Yes, but I decided to not go this way because we don't support NUMA as
of now. -numa has to bail out (just as it did before I implemented
proper query-cpus support).

What you propose is something for future support - one we have cpu
topology information exposed.


-- 

Thanks,

David / dhildenb