x86_64: Fix to keep watchdog disabled by default for i386/x86_64

Fixed wrong expression which enabled watchdogs even if nmi_watchdog kernel
parameter wasn't set. This regression got slightly introduced with commit
b7471c6d.

Introduced NMI_DISABLED (-1) which allows to switch the value of NMI_DEFAULT
without breaking the APIC NMI watchdog code (again).

Fixes:
   https://bugzilla.novell.com/show_bug.cgi?id=298084
   http://bugzilla.kernel.org/show_bug.cgi?id=7839
And likely some more nmi_watchdog=0 related issues.
Signed-off-by: Daniel Gollub <dgollub@suse.de>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/kernel/apic.c

@@ -1085,7 +1085,7 @@ static int __init detect_init_APIC (void)
 	if (l & MSR_IA32_APICBASE_ENABLE)
 		mp_lapic_addr = l & MSR_IA32_APICBASE_BASE;
 
-	if (nmi_watchdog != NMI_NONE)
+	if (nmi_watchdog != NMI_NONE && nmi_watchdog != NMI_DISABLED)
 		nmi_watchdog = NMI_LOCAL_APIC;
 
 	printk(KERN_INFO "Found and enabled local APIC!\n");

arch/i386/kernel/nmi.c

@@ -77,7 +77,7 @@ static int __init check_nmi_watchdog(void)
 	unsigned int *prev_nmi_count;
 	int cpu;
 
-	if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
+	if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DISABLED))
 		return 0;
 
 	if (!atomic_read(&nmi_active))
@@ -424,7 +424,7 @@ int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
 	if (!!old_state == !!nmi_watchdog_enabled)
 		return 0;
 
-	if (atomic_read(&nmi_active) < 0) {
+	if (atomic_read(&nmi_active) < 0 || nmi_watchdog == NMI_DISABLED) {
 		printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
 		return -EIO;
 	}

arch/x86_64/kernel/nmi.c

@@ -85,7 +85,7 @@ int __init check_nmi_watchdog (void)
 	int *counts;
 	int cpu;
 
-	if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DEFAULT))
+	if ((nmi_watchdog == NMI_NONE) || (nmi_watchdog == NMI_DISABLED)) 
 		return 0;
 
 	if (!atomic_read(&nmi_active))
@@ -442,7 +442,7 @@ int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
 	if (!!old_state == !!nmi_watchdog_enabled)
 		return 0;
 
-	if (atomic_read(&nmi_active) < 0) {
+	if (atomic_read(&nmi_active) < 0 || nmi_watchdog == NMI_DISABLED) {
 		printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
 		return -EIO;
 	}

include/asm-i386/nmi.h

@@ -33,11 +33,12 @@ extern int nmi_watchdog_tick (struct pt_regs * regs, unsigned reason);
 
 extern atomic_t nmi_active;
 extern unsigned int nmi_watchdog;
-#define NMI_DEFAULT     -1
+#define NMI_DISABLED    -1
 #define NMI_NONE	0
 #define NMI_IO_APIC	1
 #define NMI_LOCAL_APIC	2
 #define NMI_INVALID	3
+#define NMI_DEFAULT	NMI_DISABLED
 
 struct ctl_table;
 struct file;

include/asm-x86_64/nmi.h

@@ -64,11 +64,12 @@ extern int setup_nmi_watchdog(char *);
 
 extern atomic_t nmi_active;
 extern unsigned int nmi_watchdog;
-#define NMI_DEFAULT	-1
+#define NMI_DISABLED    -1
 #define NMI_NONE	0
 #define NMI_IO_APIC	1
 #define NMI_LOCAL_APIC	2
 #define NMI_INVALID	3
+#define NMI_DEFAULT	NMI_DISABLED
 
 struct ctl_table;
 struct file;