x86, NMI watchdog: disable NMIs on LVT0 in case NMI watchdog is not working

Impact: change NMI watchdog detection and disabling sequence

Currently, if the NMI watchdog fails using IOAPIC method, it'll only disable
interrupts on 8259 if the timer is passing thru it. This patch disables
NMI delivery on LINT0 if the NMI watchdog initial test fails, just for safety.
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/nmi.c

@@ -131,6 +131,11 @@ static void report_broken_nmi(int cpu, int *prev_nmi_count)
 	atomic_dec(&nmi_active);
 }
 
+static void __acpi_nmi_disable(void *__unused)
+{
+	apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
+}
+
 int __init check_nmi_watchdog(void)
 {
 	unsigned int *prev_nmi_count;
@@ -179,8 +184,12 @@ int __init check_nmi_watchdog(void)
 	kfree(prev_nmi_count);
 	return 0;
 error:
-	if (nmi_watchdog == NMI_IO_APIC && !timer_through_8259)
-		disable_8259A_irq(0);
+	if (nmi_watchdog == NMI_IO_APIC) {
+		if (!timer_through_8259)
+			disable_8259A_irq(0);
+		on_each_cpu(__acpi_nmi_disable, NULL, 1);
+	}
+
 #ifdef CONFIG_X86_32
 	timer_ack = 0;
 #endif
@@ -285,11 +294,6 @@ void acpi_nmi_enable(void)
 		on_each_cpu(__acpi_nmi_enable, NULL, 1);
 }
 
-static void __acpi_nmi_disable(void *__unused)
-{
-	apic_write(APIC_LVT0, APIC_DM_NMI | APIC_LVT_MASKED);
-}
-
 /*
  * Disable timer based NMIs on all CPUs:
  */