associativity_to_nid() is skipping node 0 when initializing
the distance lookup table. This has no practical effect when
the associativity of node 0 is always zero, which seems to
be case for a long time. As such, this line got introduced in
commit 41eab6f88f24 from 2010 and never revisited.
However, QEMU is making an effort to allow user input to configure
NUMA topologies, and this behavior got exposed when testing
that work. With the existing code, this is what happens with a
4 node NUMA guest with distance = 80 to each other:
$ numactl -H
(...)
node distances:
node 0 1 2 3
0: 10 160 160 160
1: 160 10 80 80
2: 160 80 10 80
3: 160 80 80 10
With this patch, this is the result:
$ numactl -H
(...)
node distances:
node 0 1 2 3
0: 10 80 80 80
1: 80 10 80 80
2: 80 80 10 80
3: 80 80 80 10
Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com>
---
arch/powerpc/mm/numa.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 1f61fa2148b5..c11aabad1090 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -239,7 +239,7 @@ static int associativity_to_nid(const __be32 *associativity)
if (nid == 0xffff || nid >= nr_node_ids)
nid = NUMA_NO_NODE;
- if (nid > 0 &&
+ if (nid >= 0 &&
of_read_number(associativity, 1) >= distance_ref_points_depth) {
/*
* Skip the length field and send start of associativity array
--
2.26.2
