diff --git a/sys/x86/include/specialreg.h b/sys/x86/include/specialreg.h
--- a/sys/x86/include/specialreg.h
+++ b/sys/x86/include/specialreg.h
@@ -1273,6 +1273,7 @@
 #define	MSR_VM_CR	0xc0010114	/* SVM: feature control */
 #define	MSR_VM_HSAVE_PA 0xc0010117	/* SVM: host save area address */
 #define	MSR_AMD_CPUID07	0xc0011002	/* CPUID 07 %ebx override */
+#define	MSR_AMD_CPUID01	0xc0011004	/* CPUID 01 %ecx override */
 #define	MSR_EXTFEATURES	0xc0011005	/* Extended CPUID Features override */
 #define	MSR_LS_CFG	0xc0011020
 #define	MSR_IC_CFG	0xc0011021	/* Instruction Cache Configuration */