On Wed, Jul 08, 2020 at 09:21:25AM +0200, David Hildenbrand wrote:

On 08.07.20 07:27, Mike Rapoport wrote:

quoted

On Tue, Jul 07, 2020 at 03:05:48PM -0700, Dan Williams wrote:

quoted

On Tue, Jul 7, 2020 at 11:01 AM Mike Rapoport [off-list ref] wrote:

quoted

On Tue, Jul 07, 2020 at 02:26:08PM +0200, David Hildenbrand wrote:

quoted

On 07.07.20 14:13, Mike Rapoport wrote:

quoted

On Tue, Jul 07, 2020 at 01:54:54PM +0200, Michal Hocko wrote:

quoted

On Tue 07-07-20 13:59:15, Jia He wrote:

quoted

This exports memory_add_physaddr_to_nid() for module driver to use.

memory_add_physaddr_to_nid() is a fallback option to get the nid in case
NUMA_NO_NID is detected.

Suggested-by: David Hildenbrand <redacted>
Signed-off-by: Jia He <redacted>
---
 arch/arm64/mm/numa.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
index aafcee3e3f7e..7eeb31740248 100644
--- a/arch/arm64/mm/numa.c
+++ b/arch/arm64/mm/numa.c

@@ -464,10 +464,11 @@ void __init arm64_numa_init(void)

 /*
  * We hope that we will be hotplugging memory on nodes we already know about,
- * such that acpi_get_node() succeeds and we never fall back to this...
+ * such that acpi_get_node() succeeds. But when SRAT is not present, the node
+ * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback option.
  */
 int memory_add_physaddr_to_nid(u64 addr)
 {
- pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
  return 0;
 }
+EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);

Does it make sense to export a noop function? Wouldn't make more sense
to simply make it static inline somewhere in a header? I haven't checked
whether there is an easy way to do that sanely bu this just hit my eyes.

We'll need to either add a CONFIG_ option or arch specific callback to
make both non-empty (x86, powerpc, ia64) and empty (arm64, sh)
implementations coexist ...

Note: I have a similar dummy (return 0) patch for s390x lying around here.

Then we'll call it a tie - 3:3 ;-)

So I'd be happy to jump on the train of people wanting to export the
ARM stub for this (and add a new ARM stub for phys_to_target_node()),
but Will did have a plausibly better idea that I have been meaning to
circle back to:

http://lore.kernel.org/r/20200325111039.GA32109@willie-the-truck (local)

...i.e. iterate over node data to do the lookup. This would seem to
work generically for multiple archs unless I am missing something?

IIRC, only memory assigned to/onlined to a ZONE is represented in the
pgdat node span. E.g., not offline memory blocks.

Esp., when hotplugging + onlining consecutive memory, there won't really
be any intersections in most cases if I am not wrong. It would not be
"intersection" but rather "closest fit".

With overlapping nodes it's even more unclear. Which one to pick?

quoted

I think it would work on arm64, power and, most propbably on s390

With only a single dummy node I guess it should work (searching when
there is only a single node does not make too much sense).

quoted

(David?), but not on x86. x86 does not have reserved memory in pgdat,
it's never memblock_add()'ed (see e820__memblock_setup()).

Can you enlighten me why that is relevant for the memory hotplug path?
(or is it just a general comment to make the function as accurate as
possible for all addresses?)

phys_to_target_node() on x86 falls back to numa_reserved_meminfo which
holds memory that is never listed in a node.

-- 
Thanks,

David / dhildenb

-- 
Sincerely yours,
Mike.

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