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>

1 files changed, 61 insertions, 1 deletions

diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 908699fb61c9..2d13f90476bd 100644
--- a/arch/powerpc/mm/numa.c
+++ b/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 */