[PATCH] x86_64: Avoid broadcasting NMI IPIs

On some i386/x86_64 systems, sending an NMI IPI as a broadcast will
reset the system.  This seems to be a BIOS bug which affects machines
where one or more cpus are not under OS control.  It occurs on HT
systems with a version of the OS that is not compiled without HT
support.  It also occurs when a system is booted with max_cpus=n where
2 <= n < cpus known to the BIOS.  The fix is to always send NMI IPI as
a mask instead of as a broadcast.
Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/genapic_flat.c

@@ -78,22 +78,29 @@ static void flat_send_IPI_mask(cpumask_t cpumask, int vector)
 
 static void flat_send_IPI_allbutself(int vector)
 {
-#ifndef CONFIG_HOTPLUG_CPU
-	if (((num_online_cpus()) - 1) >= 1)
-		__send_IPI_shortcut(APIC_DEST_ALLBUT, vector,APIC_DEST_LOGICAL);
+#ifdef	CONFIG_HOTPLUG_CPU
+	int hotplug = 1;
 #else
-	cpumask_t allbutme = cpu_online_map;
+	int hotplug = 0;
+#endif
+	if (hotplug || vector == NMI_VECTOR) {
+		cpumask_t allbutme = cpu_online_map;
 
-	cpu_clear(smp_processor_id(), allbutme);
+		cpu_clear(smp_processor_id(), allbutme);
 
-	if (!cpus_empty(allbutme))
-		flat_send_IPI_mask(allbutme, vector);
-#endif
+		if (!cpus_empty(allbutme))
+			flat_send_IPI_mask(allbutme, vector);
+	} else if (num_online_cpus() > 1) {
+		__send_IPI_shortcut(APIC_DEST_ALLBUT, vector,APIC_DEST_LOGICAL);
+	}
 }
 
 static void flat_send_IPI_all(int vector)
 {
-	__send_IPI_shortcut(APIC_DEST_ALLINC, vector, APIC_DEST_LOGICAL);
+	if (vector == NMI_VECTOR)
+		flat_send_IPI_mask(cpu_online_map, vector);
+	else
+		__send_IPI_shortcut(APIC_DEST_ALLINC, vector, APIC_DEST_LOGICAL);
 }
 
 static int flat_apic_id_registered(void)

include/asm-i386/mach-default/mach_ipi.h

 #ifndef __ASM_MACH_IPI_H
 #define __ASM_MACH_IPI_H
 
+/* Avoid include hell */
+#define NMI_VECTOR 0x02
+
 void send_IPI_mask_bitmask(cpumask_t mask, int vector);
 void __send_IPI_shortcut(unsigned int shortcut, int vector);
 
@@ -13,7 +16,7 @@ static inline void send_IPI_mask(cpumask_t mask, int vector)
 
 static inline void __local_send_IPI_allbutself(int vector)
 {
-	if (no_broadcast) {
+	if (no_broadcast || vector == NMI_VECTOR) {
 		cpumask_t mask = cpu_online_map;
 
 		cpu_clear(smp_processor_id(), mask);
@@ -24,7 +27,7 @@ static inline void __local_send_IPI_allbutself(int vector)
 
 static inline void __local_send_IPI_all(int vector)
 {
-	if (no_broadcast)
+	if (no_broadcast || vector == NMI_VECTOR)
 		send_IPI_mask(cpu_online_map, vector);
 	else
 		__send_IPI_shortcut(APIC_DEST_ALLINC, vector);