powerpc/pseries: Add /proc interface to control topology updates

There are instances in which we do not want topology updates to occur.
In order to allow this a /proc interface (/proc/powerpc/topology_updates)
is introduced so that topology updates can be enabled and disabled.

This patch also adds a prrn_is_enabled() call so that PRRN events are
handled in the kernel only if topology updating is enabled.
Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/topology.h

@@ -71,6 +71,7 @@ static inline void sysfs_remove_device_from_node(struct device *dev,
 #if defined(CONFIG_NUMA) && defined(CONFIG_PPC_SPLPAR)
 extern int start_topology_update(void);
 extern int stop_topology_update(void);
+extern int prrn_is_enabled(void);
 #else
 static inline int start_topology_update(void)
 {
@@ -80,6 +81,10 @@ static inline int stop_topology_update(void)
 {
 	return 0;
 }
+static inline int prrn_is_enabled(void)
+{
+	return 0;
+}
 #endif /* CONFIG_NUMA && CONFIG_PPC_SPLPAR */
 
 #include <asm-generic/topology.h>

arch/powerpc/kernel/rtasd.c

@@ -29,6 +29,7 @@
 #include <asm/nvram.h>
 #include <linux/atomic.h>
 #include <asm/machdep.h>
+#include <asm/topology.h>
 
 
 static DEFINE_SPINLOCK(rtasd_log_lock);
@@ -292,11 +293,13 @@ void prrn_schedule_update(u32 scope)
 
 static void handle_rtas_event(const struct rtas_error_log *log)
 {
-	if (log->type == RTAS_TYPE_PRRN)
+	if (log->type == RTAS_TYPE_PRRN) {
 		/* For PRRN Events the extended log length is used to denote
 		 * the scope for calling rtas update-nodes.
 		 */
-		prrn_schedule_update(log->extended_log_length);
+		if (prrn_is_enabled())
+			prrn_schedule_update(log->extended_log_length);
+	}
 
 	return;
 }

arch/powerpc/mm/numa.c

@@ -23,6 +23,9 @@
 #include <linux/cpuset.h>
 #include <linux/node.h>
 #include <linux/stop_machine.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/uaccess.h>
 #include <asm/sparsemem.h>
 #include <asm/prom.h>
 #include <asm/smp.h>
@@ -1585,7 +1588,6 @@ int start_topology_update(void)
 
 	return rc;
 }
-__initcall(start_topology_update);
 
 /*
  * Disable polling for VPHN associativity changes.
@@ -1604,4 +1606,62 @@ int stop_topology_update(void)
 
 	return rc;
 }
+
+int prrn_is_enabled(void)
+{
+	return prrn_enabled;
+}
+
+static int topology_read(struct seq_file *file, void *v)
+{
+	if (vphn_enabled || prrn_enabled)
+		seq_puts(file, "on\n");
+	else
+		seq_puts(file, "off\n");
+
+	return 0;
+}
+
+static int topology_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, topology_read, NULL);
+}
+
+static ssize_t topology_write(struct file *file, const char __user *buf,
+			      size_t count, loff_t *off)
+{
+	char kbuf[4]; /* "on" or "off" plus null. */
+	int read_len;
+
+	read_len = count < 3 ? count : 3;
+	if (copy_from_user(kbuf, buf, read_len))
+		return -EINVAL;
+
+	kbuf[read_len] = '\0';
+
+	if (!strncmp(kbuf, "on", 2))
+		start_topology_update();
+	else if (!strncmp(kbuf, "off", 3))
+		stop_topology_update();
+	else
+		return -EINVAL;
+
+	return count;
+}
+
+static const struct file_operations topology_ops = {
+	.read = seq_read,
+	.write = topology_write,
+	.open = topology_open,
+	.release = single_release
+};
+
+static int topology_update_init(void)
+{
+	start_topology_update();
+	proc_create("powerpc/topology_updates", 644, NULL, &topology_ops);
+
+	return 0;
+}
+device_initcall(topology_update_init);
 #endif /* CONFIG_PPC_SPLPAR */