1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 394d177d721..00f5962d82d 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -108,6 +108,16 @@ extern void native_apic_icr_write(u32 low, u32 id);
 extern u64 native_apic_icr_read(void);
 
 #ifdef CONFIG_X86_X2APIC
+/*
+ * Make previous memory operations globally visible before
+ * sending the IPI through x2apic wrmsr. We need a serializing instruction or
+ * mfence for this.
+ */
+static inline void x2apic_wrmsr_fence(void)
+{
+        asm volatile("mfence" : : : "memory");
+}
+
 static inline void native_apic_msr_write(u32 reg, u32 v)
 {
         if (reg == APIC_DFR || reg == APIC_ID || reg == APIC_LDR ||
@@ -184,6 +194,9 @@ static inline int x2apic_enabled(void)
 {
         return 0;
 }
+
+#define x2apic  0
+
 #endif
 
 extern int get_physical_broadcast(void);