Re: [PATCH v7 2/5] mm: remove x86-only restriction of movable_node

Reza Arbab [off-list ref] writes:

In commit c5320926e370 ("mem-hotplug: introduce movable_node boot
option"), the memblock allocation direction is changed to bottom-up and
then back to top-down like this:

1. memblock_set_bottom_up(true), called by cmdline_parse_movable_node().
2. memblock_set_bottom_up(false), called by x86's numa_init().

Even though (1) occurs in generic mm code, it is wrapped by #ifdef
CONFIG_MOVABLE_NODE, which depends on X86_64.

This means that when we extend CONFIG_MOVABLE_NODE to non-x86 arches,
things will be unbalanced. (1) will happen for them, but (2) will not.

This toggle was added in the first place because x86 has a delay between
adding memblocks and marking them as hotpluggable. Since other arches do
this marking either immediately or not at all, they do not require the
bottom-up toggle.

So, resolve things by moving (1) from cmdline_parse_movable_node() to
x86's setup_arch(), immediately after the movable_node parameter has
been parsed.

Considering that we now can mark memblock hotpluggable, do we need to
enable the bottom up allocation for ppc64 also ?

Signed-off-by: Reza Arbab <redacted>
---
 Documentation/kernel-parameters.txt |  2 +-
 arch/x86/kernel/setup.c             | 24 ++++++++++++++++++++++++

-aneesh