[PATCH] x86: Add abilty to enable/disable nmi watchdog with sysctl

Adds a new /proc/sys/kernel/nmi call that will enable/disable the nmi
watchdog.

Signed-off-by:  Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>

6 files changed, 114 insertions, 0 deletions

diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index acd3fdea2a21..28065d0b71a9 100644
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -846,6 +846,58 @@ static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
         return 0;
 }
 
+/*
+ * proc handler for /proc/sys/kernel/nmi_watchdog
+ */
+int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
+                        void __user *buffer, size_t *length, loff_t *ppos)
+{
+        int old_state;
+
+        nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
+        old_state = nmi_watchdog_enabled;
+        proc_dointvec(table, write, file, buffer, length, ppos);
+        if (!!old_state == !!nmi_watchdog_enabled)
+                return 0;
+
+        if (atomic_read(&nmi_active) < 0) {
+                printk(KERN_WARNING "NMI watchdog is permanently disabled\n");
+                return -EINVAL;
+        }
+
+        if (nmi_watchdog == NMI_DEFAULT) {
+                if (nmi_known_cpu() > 0)
+                        nmi_watchdog = NMI_LOCAL_APIC;
+                else
+                        nmi_watchdog = NMI_IO_APIC;
+        }
+
+        if (nmi_watchdog == NMI_LOCAL_APIC)
+        {
+                if (nmi_watchdog_enabled)
+                        enable_lapic_nmi_watchdog();
+                else
+                        disable_lapic_nmi_watchdog();
+        } else if (nmi_watchdog == NMI_IO_APIC) {
+                /* FIXME
+                 * for some reason these functions don't work
+                 */
+                printk("Can not enable/disable NMI on IO APIC\n");
+                return -EINVAL;
+#if 0
+                if (nmi_watchdog_enabled)
+                        enable_timer_nmi_watchdog();
+                else
+                        disable_timer_nmi_watchdog();
+#endif
+        } else {
+                printk( KERN_WARNING
+                        "NMI watchdog doesn't know what hardware to touch\n");
+                return -EIO;
+        }
+        return 0;
+}
+
 #endif
 
 EXPORT_SYMBOL(nmi_active);
diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index 9d175dcf3a2d..3a17411a9a19 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -750,6 +750,54 @@ static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
         return 0;
 }
 
+/*
+ * proc handler for /proc/sys/kernel/nmi
+ */
+int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
+                        void __user *buffer, size_t *length, loff_t *ppos)
+{
+        int old_state;
+
+        nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
+        old_state = nmi_watchdog_enabled;
+        proc_dointvec(table, write, file, buffer, length, ppos);
+        if (!!old_state == !!nmi_watchdog_enabled)
+                return 0;
+
+        if (atomic_read(&nmi_active) < 0) {
+                printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
+                return -EINVAL;
+        }
+
+        /* if nmi_watchdog is not set yet, then set it */
+        nmi_watchdog_default();
+
+        if (nmi_watchdog == NMI_LOCAL_APIC)
+        {
+                if (nmi_watchdog_enabled)
+                        enable_lapic_nmi_watchdog();
+                else
+                        disable_lapic_nmi_watchdog();
+        } else if (nmi_watchdog == NMI_IO_APIC) {
+                /* FIXME
+                 * for some reason these functions don't work
+                 */
+                printk("Can not enable/disable NMI on IO APIC\n");
+                return -EIO;
+#if 0
+                if (nmi_watchdog_enabled)
+                        enable_timer_nmi_watchdog();
+                else
+                        disable_timer_nmi_watchdog();
+#endif
+        } else {
+                printk(KERN_WARNING
+                        "NMI watchdog doesn't know what hardware to touch\n");
+                return -EIO;
+        }
+        return 0;
+}
+
 #endif
 
 EXPORT_SYMBOL(nmi_active);
diff --git a/include/asm-i386/nmi.h b/include/asm-i386/nmi.h
index 34d6bf063b6e..13b5d8311bf7 100644
--- a/include/asm-i386/nmi.h
+++ b/include/asm-i386/nmi.h
@@ -14,6 +14,7 @@
  */
 int do_nmi_callback(struct pt_regs *regs, int cpu);
 
+extern int nmi_watchdog_enabled;
 extern int avail_to_resrv_perfctr_nmi_bit(unsigned int);
 extern int avail_to_resrv_perfctr_nmi(unsigned int);
 extern int reserve_perfctr_nmi(unsigned int);
diff --git a/include/asm-x86_64/nmi.h b/include/asm-x86_64/nmi.h
index 8818c39d34e0..2c23b0df87d2 100644
--- a/include/asm-x86_64/nmi.h
+++ b/include/asm-x86_64/nmi.h
@@ -43,6 +43,7 @@ extern void die_nmi(char *str, struct pt_regs *regs);
 
 extern int panic_on_timeout;
 extern int unknown_nmi_panic;
+extern int nmi_watchdog_enabled;
 
 extern int check_nmi_watchdog(void);
 extern int avail_to_resrv_perfctr_nmi_bit(unsigned int);
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 736ed917a4f8..ecb79ba52ae1 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -150,6 +150,7 @@ enum
         KERN_IA64_UNALIGNED=72, /* int: ia64 unaligned userland trap enable */
         KERN_COMPAT_LOG=73,     /* int: print compat layer  messages */
         KERN_MAX_LOCK_DEPTH=74,
+        KERN_NMI_WATCHDOG=75, /* int: enable/disable nmi watchdog */
 };
 
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 83f168361624..040de6bd74dd 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -76,6 +76,9 @@ extern int compat_log;
 
 #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86)
 int unknown_nmi_panic;
+int nmi_watchdog_enabled;
+extern int proc_nmi_enabled(struct ctl_table *, int , struct file *,
+                        void __user *, size_t *, loff_t *);
 #endif
 
 /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */
@@ -628,6 +631,14 @@ static ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = &proc_dointvec,
         },
+        {
+                .ctl_name       = KERN_NMI_WATCHDOG,
+                .procname       = "nmi_watchdog",
+                .data           = &nmi_watchdog_enabled,
+                .maxlen         = sizeof (int),
+                .mode           = 0644,
+                .proc_handler   = &proc_nmi_enabled,
+        },
 #endif
 #if defined(CONFIG_X86)
         {