[PATCH v2] powerpc/numa: Limit possible nodes to within num_possible_nodes

[PATCH v2] powerpc/numa: Limit possible nodes to within num_possible_nodes

[Srikar Dronamraju]

MAX_NUMNODES is a theoretical maximum number of nodes thats is supported
by the kernel. Device tree properties exposes the number of possible
nodes on the current platform. The kernel would detected this and would
use it for most of its resource allocations.  If the platform now
increases the nodes to over what was already exposed, then it may lead
to inconsistencies. Hence limit it to the already exposed nodes.

Suggested-by: Nathan Lynch <nathanl@linux.ibm.com>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

Changelog v1 -> v2:
v1: https://lore.kernel.org/linuxppc-dev/20200715120534.3673-1-srikar@linux.vnet.ibm.com/t/#u
	Use nr_node_ids instead of num_possible_nodes() When nodes are
	sparse like in PowerNV, nr_node_ids gets the right value unlike
	num_possible_nodes()

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
 arch/powerpc/mm/numa.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index e437a9ac4956..383359272270 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -221,7 +221,7 @@ static void initialize_distance_lookup_table(int nid,
 	}
 }
 
-/* Returns nid in the range [0..MAX_NUMNODES-1], or -1 if no useful numa
+/* Returns nid in the range [0..nr_node_ids], or -1 if no useful numa
  * info is found.
  */
 static int associativity_to_nid(const __be32 *associativity)
@@ -235,7 +235,7 @@ static int associativity_to_nid(const __be32 *associativity)
 		nid = of_read_number(&associativity[min_common_depth], 1);
 
 	/* POWER4 LPAR uses 0xffff as invalid node */
-	if (nid == 0xffff || nid >= MAX_NUMNODES)
+	if (nid == 0xffff || nid >= nr_node_ids)
 		nid = NUMA_NO_NODE;
 
 	if (nid > 0 &&
@@ -448,7 +448,7 @@ static int of_drconf_to_nid_single(struct drmem_lmb *lmb)
 		index = lmb->aa_index * aa.array_sz + min_common_depth - 1;
 		nid = of_read_number(&aa.arrays[index], 1);
 
-		if (nid == 0xffff || nid >= MAX_NUMNODES)
+		if (nid == 0xffff || nid >= nr_node_ids)
 			nid = default_nid;
 
 		if (nid > 0) {
-- 
2.17.1

Re: [PATCH v2] powerpc/numa: Limit possible nodes to within num_possible_nodes

[Michael Ellerman]

On Fri, 24 Jul 2020 16:28:09 +0530, Srikar Dronamraju wrote:
> MAX_NUMNODES is a theoretical maximum number of nodes thats is supported
> by the kernel. Device tree properties exposes the number of possible
> nodes on the current platform. The kernel would detected this and would
> use it for most of its resource allocations.  If the platform now
> increases the nodes to over what was already exposed, then it may lead
> to inconsistencies. Hence limit it to the already exposed nodes.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/numa: Limit possible nodes to within num_possible_nodes
      https://git.kernel.org/powerpc/c/dbce456280857f329af9069af5e48a9b6ebad146

cheers