1 files changed, 10 insertions, 6 deletions

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 23f6ac05d04c..613b3d284a89 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -84,6 +84,11 @@ EXPORT_SYMBOL_GPL(used_vectors);
 static int ignore_nmis;
 
 int unknown_nmi_panic;
+/*
+ * Prevent NMI reason port (0x61) being accessed simultaneously, can
+ * only be used in NMI handler.
+ */
+static DEFINE_RAW_SPINLOCK(nmi_reason_lock);
 
 static inline void conditional_sti(struct pt_regs *regs)
 {
@@ -392,7 +397,6 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 {
         unsigned char reason = 0;
-        int cpu;
 
         /*
          * CPU-specific NMI must be processed before non-CPU-specific
@@ -402,13 +406,12 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
         if (notify_die(DIE_NMI, "nmi", regs, 0, 2, SIGINT) == NOTIFY_STOP)
                 return;
 
-        cpu = smp_processor_id();
-
-        /* Only the BSP gets external NMIs from the system. */
-        if (!cpu)
-                reason = get_nmi_reason();
+        /* Non-CPU-specific NMI: NMI sources can be processed on any CPU */
+        raw_spin_lock(&nmi_reason_lock);
+        reason = get_nmi_reason();
 
         if (!(reason & NMI_REASON_MASK)) {
+                raw_spin_unlock(&nmi_reason_lock);
                 unknown_nmi_error(reason, regs);
 
                 return;
@@ -426,6 +429,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
          */
         reassert_nmi();
 #endif
+        raw_spin_unlock(&nmi_reason_lock);
 }
 
 dotraplinkage notrace __kprobes void