[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>