Index: sys/x86/x86/identcpu.c
===================================================================
--- sys/x86/x86/identcpu.c
+++ sys/x86/x86/identcpu.c
@@ -1304,6 +1304,22 @@
 	if (cpu_feature2 & CPUID2_HV) {
 		vm_guest = VM_GUEST_VM;
 		do_cpuid(0x40000000, regs);
+
+		if (regs[0] == 0) {
+			/*
+			 * At least some versions of KVM return 0 in
+			 * %eax rather than a valid hv_high value.
+			 * Check to see if the vendor string is
+			 * different from the leaf 0 string and
+			 * overwrite the returned %eax to 0x4000000 in
+			 * that case.
+			 */
+			if (regs[1] != ((u_int *)&cpu_vendor)[0] ||
+			    regs[2] != ((u_int *)&cpu_vendor)[1] ||
+			    regs[3] != ((u_int *)&cpu_vendor)[2])
+				regs[0] = 0x40000000;
+		}
+			
 		if (regs[0] >= 0x40000000) {
 			hv_high = regs[0];
 			((u_int *)&hv_vendor)[0] = regs[1];