[PATCH 1/2] powerpc/hotplug: Ensure enough nodes avail for operations

[Michael Bringmann]

powerpc/hotplug: On systems like PowerPC which allow 'hot-add' of CPU or memory
resources, it may occur that the new resources are to be inserted into nodes
that were not used for these resources at bootup.  In the kernel, any node that
is used must be defined and initialized at boot.  In order to meet both
needs, this patch adds a new kernel command line option (numnodes=<int>)
for use by the PowerPC architecture-specific code that defines the maximum
number of nodes that the kernel will ever need in its current hardware
environment.  The boot code that initializes nodes for PowerPC will read
this value and use it to ensure that all of the desired nodes are setup
in the 'node_possible_map', and elsewhere.

Signed-off-by: Michael Bringmann <mwb at linux.vnet.ibm.com>
---
---
 arch/powerpc/mm/numa.c |   31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 371792e..11b04a3 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -60,10 +60,27 @@
 static int n_mem_addr_cells, n_mem_size_cells;
 static int form1_affinity;
 
+#define TOPOLOGY_DEF_NUM_NODES	0
 #define MAX_DISTANCE_REF_POINTS 4
 static int distance_ref_points_depth;
 static const __be32 *distance_ref_points;
 static int distance_lookup_table[MAX_NUMNODES][MAX_DISTANCE_REF_POINTS];
+static int topology_num_nodes = TOPOLOGY_DEF_NUM_NODES;
+
+/*
+ * Topology-related early parameters
+ */
+static int __init early_num_nodes(char *p)
+{
+	if (!p)
+		return 1;
+
+	topology_num_nodes = memparse(p, &p);
+	dbg("topology num nodes = 0x%d\n", topology_num_nodes);
+
+	return 0;
+}
+early_param("numnodes", early_num_nodes);
 
 /*
  * Allocate node_to_cpumask_map based on number of available nodes
@@ -892,6 +909,18 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
 	NODE_DATA(nid)->node_spanned_pages = spanned_pages;
 }
 
+static void __init setup_min_nodes(void)
+{
+	int i, l = topology_num_nodes;
+
+	for (i = 0; i < l; i++) {
+		if (!node_possible(i)) {
+			setup_node_data(i, 0, 0);
+			node_set(i, node_possible_map);
+		}
+	}
+}
+
 void __init initmem_init(void)
 {
 	int nid, cpu;
@@ -911,6 +940,8 @@ void __init initmem_init(void)
 	 */
 	nodes_and(node_possible_map, node_possible_map, node_online_map);
 
+	setup_min_nodes();
+
 	for_each_online_node(nid) {
 		unsigned long start_pfn, end_pfn;