[POWERPC] Fake NUMA emulation for PowerPC

Here's a dumb simple implementation of fake NUMA nodes for PowerPC.
Fake NUMA nodes can be specified using the following command line
option

numa=fake=<node range>

node range is of the format <range1>,<range2>,...<rangeN>

Each of the rangeX parameters is passed using memparse().  I find the
patch useful for fake NUMA emulation on my simple PowerPC machine.
I've tested it on a numa box with the following arguments

numa=fake=512M
numa=fake=512M,768M
numa=fake=256M,512M mem=512M
numa=fake=1G mem=768M
numa=fake=
without any numa= argument

The other side-effect introduced by this patch is that; in the case
where we don't have NUMA information, we now set a node online after
adding each LMB.  This node could very well be node 0, but in the case
that we enable fake NUMA nodes, when we cross node boundaries, we need
to set the new node online.

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/mm/numa.c

@@ -24,6 +24,8 @@
 
 static int numa_enabled = 1;
 
+static char *cmdline __initdata;
+
 static int numa_debug;
 #define dbg(args...) if (numa_debug) { printk(KERN_INFO args); }
 
@@ -39,6 +41,53 @@ static bootmem_data_t __initdata plat_node_bdata[MAX_NUMNODES];
 static int min_common_depth;
 static int n_mem_addr_cells, n_mem_size_cells;
 
+static int __cpuinit fake_numa_create_new_node(unsigned long end_pfn,
+						unsigned int *nid)
+{
+	unsigned long long mem;
+	char *p = cmdline;
+	static unsigned int fake_nid;
+	static unsigned long long curr_boundary;
+
+	/*
+	 * Modify node id, iff we started creating NUMA nodes
+	 * We want to continue from where we left of the last time
+	 */
+	if (fake_nid)
+		*nid = fake_nid;
+	/*
+	 * In case there are no more arguments to parse, the
+	 * node_id should be the same as the last fake node id
+	 * (we've handled this above).
+	 */
+	if (!p)
+		return 0;
+
+	mem = memparse(p, &p);
+	if (!mem)
+		return 0;
+
+	if (mem < curr_boundary)
+		return 0;
+
+	curr_boundary = mem;
+
+	if ((end_pfn << PAGE_SHIFT) > mem) {
+		/*
+		 * Skip commas and spaces
+		 */
+		while (*p == ',' || *p == ' ' || *p == '\t')
+			p++;
+
+		cmdline = p;
+		fake_nid++;
+		*nid = fake_nid;
+		dbg("created new fake_node with id %d\n", fake_nid);
+		return 1;
+	}
+	return 0;
+}
+
 static void __cpuinit map_cpu_to_node(int cpu, int node)
 {
 	numa_cpu_lookup_table[cpu] = node;
@@ -344,6 +393,9 @@ static void __init parse_drconf_memory(struct device_node *memory)
 			if (nid == 0xffff || nid >= MAX_NUMNODES)
 				nid = default_nid;
 		}
+
+		fake_numa_create_new_node(((start + lmb_size) >> PAGE_SHIFT),
+						&nid);
 		node_set_online(nid);
 
 		size = numa_enforce_memory_limit(start, lmb_size);
@@ -429,6 +481,8 @@ new_range:
 		nid = of_node_to_nid_single(memory);
 		if (nid < 0)
 			nid = default_nid;
+
+		fake_numa_create_new_node(((start + size) >> PAGE_SHIFT), &nid);
 		node_set_online(nid);
 
 		if (!(size = numa_enforce_memory_limit(start, size))) {
@@ -461,7 +515,7 @@ static void __init setup_nonnuma(void)
 	unsigned long top_of_ram = lmb_end_of_DRAM();
 	unsigned long total_ram = lmb_phys_mem_size();
 	unsigned long start_pfn, end_pfn;
-	unsigned int i;
+	unsigned int i, nid = 0;
 
 	printk(KERN_DEBUG "Top of RAM: 0x%lx, Total RAM: 0x%lx\n",
 	       top_of_ram, total_ram);
@@ -471,9 +525,11 @@ static void __init setup_nonnuma(void)
 	for (i = 0; i < lmb.memory.cnt; ++i) {
 		start_pfn = lmb.memory.region[i].base >> PAGE_SHIFT;
 		end_pfn = start_pfn + lmb_size_pages(&lmb.memory, i);
-		add_active_range(0, start_pfn, end_pfn);
+
+		fake_numa_create_new_node(end_pfn, &nid);
+		add_active_range(nid, start_pfn, end_pfn);
+		node_set_online(nid);
 	}
-	node_set_online(0);
 }
 
 void __init dump_numa_cpu_topology(void)
@@ -702,6 +758,10 @@ static int __init early_numa(char *p)
 	if (strstr(p, "debug"))
 		numa_debug = 1;
 
+	p = strstr(p, "fake=");
+	if (p)
+		cmdline = p + strlen("fake=");
+
 	return 0;
 }
 early_param("numa", early_numa);