Index: stable/10/sys/amd64/amd64/machdep.c
===================================================================
--- stable/10/sys/amd64/amd64/machdep.c
+++ stable/10/sys/amd64/amd64/machdep.c
@@ -1590,13 +1590,15 @@
 		Maxmem = atop(physmem_tunable);
 
 	/*
-	 * By default enable the memory test on real hardware, and disable
-	 * it if we appear to be running in a VM.  This avoids touching all
-	 * pages unnecessarily, which doesn't matter on real hardware but is
-	 * bad for shared VM hosts.  Use a general name so that
-	 * one could eventually do more with the code than just disable it.
+	 * The boot memory test is disabled by default, as it takes a
+	 * significant amount of time on large-memory systems, and is
+	 * unfriendly to virtual machines as it unnecessarily touches all
+	 * pages.
+	 *
+	 * A general name is used as the code may be extended to support
+	 * additional tests beyond the current "page present" test.
 	 */
-	memtest = (vm_guest > VM_GUEST_NO) ? 0 : 1;
+	memtest = 0;
 	TUNABLE_ULONG_FETCH("hw.memtest.tests", &memtest);
 
 	/*