[PATCH] powerpc/pseries: Fix numa FORM2 parsing fallback code

In case the FORM2 distance table from firmware is not the expected size,
there is fallback code that just populates the lookup table as local vs
remote.

However it then continues on to use the distance table. Fix.

Cc: Aneesh Kumar K.V <redacted>
Fixes: 1c6b5a7e7405 ("powerpc/pseries: Add support for FORM2 associativity")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/mm/numa.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 6f14c8fb6359..0789cde7f658 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c

@@ -380,6 +380,7 @@ static void initialize_form2_numa_distance_lookup_table(void)
 	const __be32 *numa_lookup_index;
 	int numa_dist_table_length;
 	int max_numa_index, distance_index;
+	bool good = true;
 
 	if (firmware_has_feature(FW_FEATURE_OPAL))
 		root = of_find_node_by_path("/ibm,opal");

@@ -407,30 +408,26 @@ static void initialize_form2_numa_distance_lookup_table(void)
 
 	if (numa_dist_table_length != max_numa_index * max_numa_index) {
 		WARN(1, "Wrong NUMA distance information\n");
-		/* consider everybody else just remote. */
-		for (i = 0;  i < max_numa_index; i++) {
-			for (j = 0; j < max_numa_index; j++) {
-				int nodeA = numa_id_index_table[i];
-				int nodeB = numa_id_index_table[j];
-
-				if (nodeA == nodeB)
-					numa_distance_table[nodeA][nodeB] = LOCAL_DISTANCE;
-				else
-					numa_distance_table[nodeA][nodeB] = REMOTE_DISTANCE;
-			}
-		}
+		good = false;
 	}
-
 	distance_index = 0;
 	for (i = 0;  i < max_numa_index; i++) {
 		for (j = 0; j < max_numa_index; j++) {
 			int nodeA = numa_id_index_table[i];
 			int nodeB = numa_id_index_table[j];
-
-			numa_distance_table[nodeA][nodeB] = numa_dist_table[distance_index++];
-			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, numa_distance_table[nodeA][nodeB]);
+			int dist;
+
+			if (good)
+				dist = numa_dist_table[distance_index++];
+			else if (nodeA == nodeB)
+				dist = LOCAL_DISTANCE;
+			else
+				dist = REMOTE_DISTANCE;
+			numa_distance_table[nodeA][nodeB] = dist;
+			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, dist);
 		}
 	}
+
 	of_node_put(root);
 }
 

-- 
2.23.0

Nicholas Piggin [off-list ref] writes:

In case the FORM2 distance table from firmware is not the expected size,
there is fallback code that just populates the lookup table as local vs
remote.

However it then continues on to use the distance table. Fix.

Reviewed-by: Aneesh Kumar K.V <redacted>

Nicholas Piggin [off-list ref] writes:

numa_dist_table is a pointer, so couldn't we just set it to NULL if the
info it's pointing at is invalid?

ie.		numa_dist_table = NULL;

 	}
-
 	distance_index = 0;
 	for (i = 0;  i < max_numa_index; i++) {
 		for (j = 0; j < max_numa_index; j++) {
 			int nodeA = numa_id_index_table[i];
 			int nodeB = numa_id_index_table[j];
-
-			numa_distance_table[nodeA][nodeB] = numa_dist_table[distance_index++];
-			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, numa_distance_table[nodeA][nodeB]);
+			int dist;
+
+			if (good)

			if (numa_dist_table)

+				dist = numa_dist_table[distance_index++];
+			else if (nodeA == nodeB)
+				dist = LOCAL_DISTANCE;
+			else
+				dist = REMOTE_DISTANCE;
+			numa_distance_table[nodeA][nodeB] = dist;
+			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, dist);
 		}
 	}
+
 	of_node_put(root);
 }

But maybe before we do that we can rename it, because it is really easy
to confuse numa_dist_table and numa_distance_table if you don't look
closely.

cheers

Excerpts from Michael Ellerman's message of November 8, 2021 3:20 pm:

Nicholas Piggin [off-list ref] writes:

quoted

In case the FORM2 distance table from firmware is not the expected size,
there is fallback code that just populates the lookup table as local vs
remote.

However it then continues on to use the distance table. Fix.

Cc: Aneesh Kumar K.V <redacted>
Fixes: 1c6b5a7e7405 ("powerpc/pseries: Add support for FORM2 associativity")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/mm/numa.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 6f14c8fb6359..0789cde7f658 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c

@@ -380,6 +380,7 @@ static void initialize_form2_numa_distance_lookup_table(void)
 	const __be32 *numa_lookup_index;
 	int numa_dist_table_length;
 	int max_numa_index, distance_index;
+	bool good = true;

numa_dist_table is a pointer, so couldn't we just set it to NULL if the
info it's pointing at is invalid?

Yeah probably could just do that.

quoted

 
 	if (firmware_has_feature(FW_FEATURE_OPAL))
 		root = of_find_node_by_path("/ibm,opal");

@@ -407,30 +408,26 @@ static void initialize_form2_numa_distance_lookup_table(void)
 
 	if (numa_dist_table_length != max_numa_index * max_numa_index) {
 		WARN(1, "Wrong NUMA distance information\n");
-		/* consider everybody else just remote. */
-		for (i = 0;  i < max_numa_index; i++) {
-			for (j = 0; j < max_numa_index; j++) {
-				int nodeA = numa_id_index_table[i];
-				int nodeB = numa_id_index_table[j];
-
-				if (nodeA == nodeB)
-					numa_distance_table[nodeA][nodeB] = LOCAL_DISTANCE;
-				else
-					numa_distance_table[nodeA][nodeB] = REMOTE_DISTANCE;
-			}
-		}
+		good = false;

ie.		numa_dist_table = NULL;

quoted

 	}
-
 	distance_index = 0;
 	for (i = 0;  i < max_numa_index; i++) {
 		for (j = 0; j < max_numa_index; j++) {
 			int nodeA = numa_id_index_table[i];
 			int nodeB = numa_id_index_table[j];
-
-			numa_distance_table[nodeA][nodeB] = numa_dist_table[distance_index++];
-			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, numa_distance_table[nodeA][nodeB]);
+			int dist;
+
+			if (good)

			if (numa_dist_table)

quoted

+				dist = numa_dist_table[distance_index++];
+			else if (nodeA == nodeB)
+				dist = LOCAL_DISTANCE;
+			else
+				dist = REMOTE_DISTANCE;
+			numa_distance_table[nodeA][nodeB] = dist;
+			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, dist);
 		}
 	}
+
 	of_node_put(root);
 }

But maybe before we do that we can rename it, because it is really easy
to confuse numa_dist_table and numa_distance_table if you don't look
closely.

Maybe dt_form2_distances?

Thanks,
Nick

Nicholas Piggin [off-list ref] writes:

Excerpts from Michael Ellerman's message of November 8, 2021 3:20 pm:

quoted

Nicholas Piggin [off-list ref] writes:

quoted

In case the FORM2 distance table from firmware is not the expected size,
there is fallback code that just populates the lookup table as local vs
remote.

However it then continues on to use the distance table. Fix.

Cc: Aneesh Kumar K.V <redacted>
Fixes: 1c6b5a7e7405 ("powerpc/pseries: Add support for FORM2 associativity")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/mm/numa.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 6f14c8fb6359..0789cde7f658 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c

@@ -380,6 +380,7 @@ static void initialize_form2_numa_distance_lookup_table(void)
 	const __be32 *numa_lookup_index;
 	int numa_dist_table_length;
 	int max_numa_index, distance_index;
+	bool good = true;

numa_dist_table is a pointer, so couldn't we just set it to NULL if the
info it's pointing at is invalid?

Yeah probably could just do that.

quoted

quoted

 
 	if (firmware_has_feature(FW_FEATURE_OPAL))
 		root = of_find_node_by_path("/ibm,opal");

@@ -407,30 +408,26 @@ static void initialize_form2_numa_distance_lookup_table(void)
 
 	if (numa_dist_table_length != max_numa_index * max_numa_index) {
 		WARN(1, "Wrong NUMA distance information\n");
-		/* consider everybody else just remote. */
-		for (i = 0;  i < max_numa_index; i++) {
-			for (j = 0; j < max_numa_index; j++) {
-				int nodeA = numa_id_index_table[i];
-				int nodeB = numa_id_index_table[j];
-
-				if (nodeA == nodeB)
-					numa_distance_table[nodeA][nodeB] = LOCAL_DISTANCE;
-				else
-					numa_distance_table[nodeA][nodeB] = REMOTE_DISTANCE;
-			}
-		}
+		good = false;

ie.		numa_dist_table = NULL;

quoted

 	}
-
 	distance_index = 0;
 	for (i = 0;  i < max_numa_index; i++) {
 		for (j = 0; j < max_numa_index; j++) {
 			int nodeA = numa_id_index_table[i];
 			int nodeB = numa_id_index_table[j];
-
-			numa_distance_table[nodeA][nodeB] = numa_dist_table[distance_index++];
-			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, numa_distance_table[nodeA][nodeB]);
+			int dist;
+
+			if (good)

			if (numa_dist_table)

quoted

+				dist = numa_dist_table[distance_index++];
+			else if (nodeA == nodeB)
+				dist = LOCAL_DISTANCE;
+			else
+				dist = REMOTE_DISTANCE;
+			numa_distance_table[nodeA][nodeB] = dist;
+			pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, dist);
 		}
 	}
+
 	of_node_put(root);
 }

But maybe before we do that we can rename it, because it is really easy
to confuse numa_dist_table and numa_distance_table if you don't look
closely.

Maybe dt_form2_distances?

Or just "form2_distances", it's only a local so the fact that it's from
the dt is clear enough I think.

cheers