--- /usr/src/sys.old/kern/subr_param.c	2007-12-16 01:37:33.000000000 -0600
+++ kern/subr_param.c	2007-12-28 02:51:28.000000000 -0600
@@ -108,8 +108,29 @@
 void
 init_param1(void)
 {
+	char *envptr;
 
 	hz = HZ;
+	/* Neither QEMU or VMWare can keep up with guests running at
+	 * 1000 hz.  This leads to highly inaccurate timekeeping by
+	 * the guest.  To work around this, force 100 hz when we
+	 * detect that we are a guest of one of these two.
+	 */
+	envptr = getenv("hint.acpi.0.oem");
+	if (envptr) {
+		if (memcmp(envptr, "QEMU", 4) == 0)
+			hz = 100;
+		freeenv(envptr);
+		envptr = NULL;
+	}
+	envptr = getenv("smbios.system.maker");
+	if (envptr) {
+		if (memcmp(envptr, "VMware, Inc.", 12) == 0)
+			hz = 100;
+		freeenv(envptr);
+		envptr = NULL;
+	}
+		
 	TUNABLE_INT_FETCH("kern.hz", &hz);
 	tick = 1000000 / hz;