s390/topology: enable / disable topology dynamically

Add a new sysctl file /proc/sys/s390/topology which displays if
topology is on (1) or off (0) as specified by the "topology=" kernel
parameter.

This allows to change topology information during runtime and
configuring it via /etc/sysctl.conf instead of using the kernel line
parameter.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 74 insertions, 2 deletions

diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c
index a0ce9c83f589..ed0bdd220e1a 100644
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -8,6 +8,8 @@
 
 #include <linux/workqueue.h>
 #include <linux/bootmem.h>
+#include <linux/uaccess.h>
+#include <linux/sysctl.h>
 #include <linux/cpuset.h>
 #include <linux/device.h>
 #include <linux/export.h>
@@ -207,10 +209,8 @@ static void topology_update_polarization_simple(void)
 {
         int cpu;
 
-        mutex_lock(&smp_cpu_state_mutex);
         for_each_possible_cpu(cpu)
                 smp_cpu_set_polarization(cpu, POLARIZATION_HRZ);
-        mutex_unlock(&smp_cpu_state_mutex);
 }
 
 static int ptf(unsigned long fc)
@@ -278,6 +278,7 @@ static int __arch_update_cpu_topology(void)
         struct sysinfo_15_1_x *info = tl_info;
         int rc = 0;
 
+        mutex_lock(&smp_cpu_state_mutex);
         cpumask_clear(&cpus_with_topology);
         if (MACHINE_HAS_TOPOLOGY) {
                 rc = 1;
@@ -287,6 +288,7 @@ static int __arch_update_cpu_topology(void)
         update_cpu_masks();
         if (!MACHINE_HAS_TOPOLOGY)
                 topology_update_polarization_simple();
+        mutex_unlock(&smp_cpu_state_mutex);
         return rc;
 }
 
@@ -313,6 +315,11 @@ void topology_schedule_update(void)
         schedule_work(&topology_work);
 }
 
+static void topology_flush_work(void)
+{
+        flush_work(&topology_work);
+}
+
 static void topology_timer_fn(unsigned long ignored)
 {
         if (ptf(PTF_CHECK))
@@ -511,6 +518,11 @@ static inline int topology_get_mode(int enabled)
         return MACHINE_HAS_TOPOLOGY ? TOPOLOGY_MODE_HW : TOPOLOGY_MODE_PACKAGE;
 }
 
+static inline int topology_is_enabled(void)
+{
+        return topology_mode != TOPOLOGY_MODE_SINGLE;
+}
+
 static int __init topology_setup(char *str)
 {
         bool enabled;
@@ -524,12 +536,72 @@ static int __init topology_setup(char *str)
 }
 early_param("topology", topology_setup);
 
+static int topology_ctl_handler(struct ctl_table *ctl, int write,
+                                void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        unsigned int len;
+        int new_mode;
+        char buf[2];
+
+        if (!*lenp || *ppos) {
+                *lenp = 0;
+                return 0;
+        }
+        if (!write) {
+                strncpy(buf, topology_is_enabled() ? "1\n" : "0\n",
+                        ARRAY_SIZE(buf));
+                len = strnlen(buf, ARRAY_SIZE(buf));
+                if (len > *lenp)
+                        len = *lenp;
+                if (copy_to_user(buffer, buf, len))
+                        return -EFAULT;
+                goto out;
+        }
+        len = *lenp;
+        if (copy_from_user(buf, buffer, len > sizeof(buf) ? sizeof(buf) : len))
+                return -EFAULT;
+        if (buf[0] != '0' && buf[0] != '1')
+                return -EINVAL;
+        mutex_lock(&smp_cpu_state_mutex);
+        new_mode = topology_get_mode(buf[0] == '1');
+        if (topology_mode != new_mode) {
+                topology_mode = new_mode;
+                topology_schedule_update();
+        }
+        mutex_unlock(&smp_cpu_state_mutex);
+        topology_flush_work();
+out:
+        *lenp = len;
+        *ppos += len;
+        return 0;
+}
+
+static struct ctl_table topology_ctl_table[] = {
+        {
+                .procname       = "topology",
+                .mode           = 0644,
+                .proc_handler   = topology_ctl_handler,
+        },
+        { },
+};
+
+static struct ctl_table topology_dir_table[] = {
+        {
+                .procname       = "s390",
+                .maxlen         = 0,
+                .mode           = 0555,
+                .child          = topology_ctl_table,
+        },
+        { },
+};
+
 static int __init topology_init(void)
 {
         if (MACHINE_HAS_TOPOLOGY)
                 set_topology_timer();
         else
                 topology_update_polarization_simple();
+        register_sysctl_table(topology_dir_table);
         return device_create_file(cpu_subsys.dev_root, &dev_attr_dispatching);
 }
 device_initcall(topology_init);