[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>

1 files changed, 16 insertions, 9 deletions

diff --git a/arch/x86_64/kernel/genapic_flat.c b/arch/x86_64/kernel/genapic_flat.c
index c66ca7b1d31a..21c7066e236a 100644
--- a/arch/x86_64/kernel/genapic_flat.c
+++ b/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)