Reza Arbab [off-list ref] writes:

On Wed, Oct 26, 2016 at 09:34:18AM +1100, Balbir Singh wrote:

quoted

I still believe we need your changes, I was wondering if we've tested
it against normal memory nodes and checked if any memblock
allocations end up there. Michael showed me some memblock
allocations on node 1 of a two node machine with movable_node

The movable_node option is x86-only. Both of those nodes contain normal 
memory, so allocations on both are allowed.

quoted

quoted

Longer; if you use "movable_node", x86 can identify these nodes at 
boot. They call memblock_mark_hotplug() while parsing the SRAT. Then, 
when the zones are initialized, those markings are used to determine 
ZONE_MOVABLE.

We have no analog of this SRAT information, so our movable nodes can 
only be created post boot, by hotplugging and explicitly onlining 
with online_movable.

Is this true for all of system memory as well or only for nodes
hotplugged later?

As far as I know, power has nothing like the SRAT that tells us, at 
boot, which memory is hotpluggable.

On pseries we have the ibm,dynamic-memory device tree property, which
can contain ranges of memory that are not yet "assigned to the
partition" - ie. can be hotplugged later.

So in general that statement is not true.

But I think you're focused on bare-metal, in which case you might be
right. But that doesn't mean we couldn't have a similar property, if
skiboot/hostboot knew what the ranges of memory were going to be.

cheers