Index: sys/x86/x86/identcpu.c
===================================================================
--- sys/x86/x86/identcpu.c
+++ sys/x86/x86/identcpu.c
@@ -1381,6 +1381,7 @@
 #endif
 {
 	u_int regs[4], cpu_stdext_disable;
+	uint64_t msr;
 #ifdef __i386__
 	u_char ccr3;
 #endif
@@ -1458,6 +1459,23 @@
 		do_cpuid(0x80000001, regs);
 		amd_feature = regs[3] & ~(cpu_feature & 0x0183f3ff);
 		amd_feature2 = regs[2];
+		if (cpu_vendor_id == CPU_VENDOR_AMD &&
+		    CPUID_TO_FAMILY(cpu_id) == 0x15 &&
+		    (amd_feature2 & AMDID2_TOPOLOGY) == 0) {
+			/*
+			 * See BIOS and Kernel Developer’s Guide (BKDG)
+			 * for AMD Family 15h Models 60h-6Fh Processors,
+			 * Publication # 50742.
+			 */
+			msr = rdmsr(0xc0011005);
+			msr |= (uint64_t)1 << 54;
+			wrmsr(0xc0011005, msr);
+
+			do_cpuid(0x80000001, regs);
+			amd_feature2 = regs[2];
+			if ((amd_feature2 & AMDID2_TOPOLOGY) != 0)
+				printf("Re-enabled topology extension\n");
+		}
 	}
 	if (cpu_exthigh >= 0x80000007) {
 		do_cpuid(0x80000007, regs);