[RFC PATCH] powerpc/numa: initialize distance lookup table from drconf path

Node distance will not get initialized in certain cases as
dynamic-reconfiguration path does not initialize the lookup table.

There is an assumption about the associativity list in
initialize_distance_lookup_table(). Associativity list has two forms:

a) [cpu,memory]@x/ibm,associativity has following
   format:

    <N> <N integers>

b) ibm,dynamic-reconfiguration-memory/ibm,associativity-lookup-arrays

   <M> <N> <M*N integers>
   M = the number of associativity lists
   N = the number of entries per associativity list

Fix initialize_distance_lookup_table() so that it does not assume
"case a". And update the caller to skip the length field before
sending the associativity list.

Call initialize_distance_lookup_table() from drconf path with
appropriate associativity list.

Reported-by: Bharata B Rao <redacted>
Signed-off-by: Nikunj A Dadhania <redacted>
---
 arch/powerpc/mm/numa.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 5e80621..8b9502a 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c

@@ -225,7 +225,7 @@ static void initialize_distance_lookup_table(int nid,
 	for (i = 0; i < distance_ref_points_depth; i++) {
 		const __be32 *entry;
 
-		entry = &associativity[be32_to_cpu(distance_ref_points[i])];
+		entry = &associativity[be32_to_cpu(distance_ref_points[i]) - 1];
 		distance_lookup_table[nid][i] = of_read_number(entry, 1);
 	}
 }

@@ -248,8 +248,12 @@ static int associativity_to_nid(const __be32 *associativity)
 		nid = -1;
 
 	if (nid > 0 &&
-	    of_read_number(associativity, 1) >= distance_ref_points_depth)
-		initialize_distance_lookup_table(nid, associativity);
+		of_read_number(associativity, 1) >= distance_ref_points_depth) {
+		/*
+		 * Skip the length field and send start of associativity array
+		 */
+		initialize_distance_lookup_table(nid, associativity + 1);
+	}
 
 out:
 	return nid;

@@ -507,6 +511,12 @@ static int of_drconf_to_nid_single(struct of_drconf_cell *drmem,
 
 		if (nid == 0xffff || nid >= MAX_NUMNODES)
 			nid = default_nid;
+
+		if (nid > 0) {
+			index = drmem->aa_index * aa->array_sz;
+			initialize_distance_lookup_table(nid,
+							&aa->arrays[index]);
+		}
 	}
 
 	return nid;

-- 
1.8.3.1

Reworded commit log:

From: Nikunj A Dadhania <redacted>

powerpc/numa: initialize distance lookup table from drconf path

In some situations, a NUMA guest that supports
ibm,dynamic-memory-reconfiguration node will end up having flat NUMA
distances between nodes. This is because of two problems in the
current code.

1) Different representations of associativity lists.

   There is an assumption about the associativity list in
   initialize_distance_lookup_table(). Associativity list has two forms:

   a) [cpu,memory]@x/ibm,associativity has following
      format:
           <N> <N integers>

   b) ibm,dynamic-reconfiguration-memory/ibm,associativity-lookup-arrays

           <M> <N> <M associativity lists each having N integers>
           M = the number of associativity lists
           N = the number of entries per associativity list

   Fix initialize_distance_lookup_table() so that it does not assume
   "case a". And update the caller to skip the length field before
   sending the associativity list.

2) Distance table not getting updated from drconf path.

   Node distance table will not get initialized in certain cases as
   ibm,dynamic-reconfiguration-memory path does not initialize the
   lookup table.

   Call initialize_distance_lookup_table() from drconf path with
   appropriate associativity list.

Reported-by: Bharata B Rao <redacted>
Signed-off-by: Nikunj A Dadhania <redacted>
---
 arch/powerpc/mm/numa.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 5e80621..8b9502a 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c

@@ -225,7 +225,7 @@ static void initialize_distance_lookup_table(int nid,
 	for (i = 0; i < distance_ref_points_depth; i++) {
 		const __be32 *entry;
 
-		entry = &associativity[be32_to_cpu(distance_ref_points[i])];
+		entry = &associativity[be32_to_cpu(distance_ref_points[i]) - 1];
 		distance_lookup_table[nid][i] = of_read_number(entry, 1);
 	}
 }

@@ -248,8 +248,12 @@ static int associativity_to_nid(const __be32 *associativity)
 		nid = -1;
 
 	if (nid > 0 &&
-	    of_read_number(associativity, 1) >= distance_ref_points_depth)
-		initialize_distance_lookup_table(nid, associativity);
+		of_read_number(associativity, 1) >= distance_ref_points_depth) {
+		/*
+		 * Skip the length field and send start of associativity array
+		 */
+		initialize_distance_lookup_table(nid, associativity + 1);
+	}
 
 out:
 	return nid;

@@ -507,6 +511,12 @@ static int of_drconf_to_nid_single(struct of_drconf_cell *drmem,
 
 		if (nid == 0xffff || nid >= MAX_NUMNODES)
 			nid = default_nid;
+
+		if (nid > 0) {
+			index = drmem->aa_index * aa->array_sz;
+			initialize_distance_lookup_table(nid,
+							&aa->arrays[index]);
+		}
 	}
 
 	return nid;

-- 
1.8.3.1

Nikunj A Dadhania [off-list ref] writes:

Reworded commit log:

From: Nikunj A Dadhania <redacted>

powerpc/numa: initialize distance lookup table from drconf path

Ping ?

Regards
Nikunj

Hi Nikunj,

From: Nikunj A Dadhania <redacted>

powerpc/numa: initialize distance lookup table from drconf path

In some situations, a NUMA guest that supports
ibm,dynamic-memory-reconfiguration node will end up having flat NUMA
distances between nodes. This is because of two problems in the
current code.

Thanks for the patch. Have we tested that this doesn't regress the
non dynamic representation?

Regards,
Anton

Hi Anton,

Anton Blanchard [off-list ref] writes:

Hi Nikunj,

quoted

From: Nikunj A Dadhania <redacted>

powerpc/numa: initialize distance lookup table from drconf path

In some situations, a NUMA guest that supports
ibm,dynamic-memory-reconfiguration node will end up having flat NUMA
distances between nodes. This is because of two problems in the
current code.

Thanks for the patch. Have we tested that this doesn't regress the
non dynamic representation?

Yes, that is tested. And works as expected.

Regards
Nikunj

Hi Anton/Michael,

Nikunj A Dadhania [off-list ref] writes:

Hi Anton,

Anton Blanchard [off-list ref] writes:

quoted

Hi Nikunj,

quoted

From: Nikunj A Dadhania <redacted>

powerpc/numa: initialize distance lookup table from drconf path

In some situations, a NUMA guest that supports
ibm,dynamic-memory-reconfiguration node will end up having flat NUMA
distances between nodes. This is because of two problems in the
current code.

Thanks for the patch. Have we tested that this doesn't regress the
non dynamic representation?

Yes, that is tested. And works as expected.

If the patch looks fine, can this be pushed upstream ?

Regards,
Nikunj

Hi Nikunj,

quoted

Thanks for the patch. Have we tested that this doesn't regress the
non dynamic representation?

Yes, that is tested. And works as expected.

Great, you can add:

Acked-by: Anton Blanchard <redacted>

Anton

On Thu, 2015-07-02 at 08:31 +1000, Anton Blanchard wrote:

Hi Nikunj,

quoted

quoted

Thanks for the patch. Have we tested that this doesn't regress the
non dynamic representation?

Yes, that is tested. And works as expected.

Great, you can add:

Acked-by: Anton Blanchard <redacted>

Hi Nikunj,

Please resend a non-RFC version, with the updated changelog and Anton's ack
included.

cheers