Re: [PATCH v2] hw/arm/virt: Expose empty NUMA nodes through ACPI

[David Hildenbrand]

>>
>> Examples include exposing HBM or PMEM to the VM. Just like on real HW,
>> this memory is exposed via cpu-less, special nodes. In contrast to real
>> HW, the memory is hotplugged later (I don't think HW supports hotplug
>> like that yet, but it might just be a matter of time).
> 
> I suppose some of that maybe covered by GENERIC_AFFINITY entries in SRAT
> some by MEMORY entries. Or nodes created dynamically like with normal
> hotplug memory.
> 

I'm certainly no SRAT expert, but seems like under VMWare something
similar can happen:

https://lkml.kernel.org/r/BAE95F0C-FAA7-40C6-A0D6-5049B1207A27@vmware.com

"VM was powered on with 4 vCPUs (4 NUMA nodes) and 4GB memory.
ACPI SRAT reports 128 possible CPUs and 128 possible NUMA nodes."

Note that that discussion is about hotplugging CPUs to memory-less,
hotplugged nodes.

But there seems to be some way to expose possible NUMA nodes. Maybe
that's via GENERIC_AFFINITY.

-- 
Thanks,

David / dhildenb