In our "auto-movable" memory onlining policy, we want to make decisions
across memory blocks of a single memory device.  Examples of memory
devices include ACPI memory devices (in the simplest case a single DIMM)
and virtio-mem.  For now, we don't have a connection between a single
memory block device and the real memory device.  Each memory device
consists of 1..X memory block devices.

Let's logically group memory blocks belonging to the same memory device in
"memory groups".  Memory groups can span multiple physical ranges and a
memory group itself does not contain any information regarding physical
ranges, only properties (e.g., "max_pages") necessary for improved memory
onlining.

Introduce two memory group types:

1) Static memory group: E.g., a single ACPI memory device, consisting
   of 1..X memory resources.  A memory group consists of 1..Y memory
   blocks.  The whole group is added/removed in one go.  If any part
   cannot get offlined, the whole group cannot be removed.

2) Dynamic memory group: E.g., a single virtio-mem device.  Memory is
   dynamically added/removed in a fixed granularity, called a "unit",
   consisting of 1..X memory blocks.  A unit is added/removed in one go.
   If any part of a unit cannot get offlined, the whole unit cannot be
   removed.

In case of 1) we usually want either all memory managed by ZONE_MOVABLE or
none.  In case of 2) we usually want to have as many units as possible
managed by ZONE_MOVABLE.  We want a single unit to be of the same type.

For now, memory groups are an internal concept that is not exposed to user
space; we might want to change that in the future, though.

add_memory() users can specify a mgid instead of a nid when passing the
MHP_NID_IS_MGID flag.

Link: https://lkml.kernel.org/r/20210806124715.17090-4-david@redhat.comSigned-off-by: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hui Zhu <teawater@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Marek Kedzierski <mkedzier@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>