The mem device provides direct memory access (needed e.g. for Xorg), but some
packages (Xorg, notably) are still using the iopl device.

diff --git a/i386/i386at/conf.c b/i386/i386at/conf.c
index d51b5ee..88e753c 100644
--- a/i386/i386at/conf.c
+++ b/i386/i386at/conf.c
@@ -135,6 +135,10 @@ struct dev_ops	dev_name_list[] =
 	  nodev,	nodev,		nodev,		memmmap,
 	  nodev,	nulldev,	nulldev,	0,
 	  nodev },
+	{ "iopl",	nulldev,	nulldev,	nodev,
+	  nodev,	nodev,		nodev,		memmmap,
+	  nodev,	nulldev,	nulldev,	0,
+	  nodev },
 #endif	/* MACH_HYP */
 
 #ifdef	MACH_KMSG