[Qemu-devel] Regression (?) due to c4177479 ('spapr: make sure RMA is in first mode of first memory node')

[Nishanth Aravamudan]

Hi Alexey,

Prior to the $SUBJECT commit, we could present memoryless node0s to
guests. Now, we indicate that we don't have the requisite 128M for the
RMA if node 0 has no memory. Note that a memoryless node0 is possible
under PowerVM (but not predictably present) so I was hoping to use KVM
to test relevant fixes for memoryless nodes.

I think this change is a misinterpretation of the PAPR standard, though.
Yes, the RMA must be in the first block of memory, but that isn't
necessarily on node 0. The topology of a PAPR-compliant guest does not
require a node 0 (and in fact, under PowerVM, Linux doesn't actually
require node 0 either, but it would under KVM).

Thoughts? I suppose it's fine to say that node 0 must be sufficiently
populated under KVM -- there's not really a reason to not have memory on
a given node (except maybe ballooning). I can keep the commit reverted
locally for testing purposes. Just wanted to see if the semantic change
was intentional.

Thanks,
Nish