x86: Stop MCEs and NMIs during code patching

When a machine check or NMI occurs while multiple byte code is patched
the CPU could theoretically see an inconsistent instruction and crash.
Prevent this by temporarily disabling MCEs and returning early in the
NMI handler.

Based on discussion with Mathieu Desnoyers.

Cc: Mathieu Desnoyers <compudj@krystal.dyndns.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-x86_64/nmi.h b/include/asm-x86_64/nmi.h
index d0a7f53b1497..5fb3c0de5ccc 100644
--- a/include/asm-x86_64/nmi.h
+++ b/include/asm-x86_64/nmi.h
@@ -88,5 +88,7 @@ unsigned lapic_adjust_nmi_hz(unsigned hz);
 int lapic_watchdog_ok(void);
 void disable_lapic_nmi_watchdog(void);
 void enable_lapic_nmi_watchdog(void);
+void stop_nmi(void);
+void restart_nmi(void);
 
 #endif /* ASM_NMI_H */