diff -ur a/linux-2.6-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64 b/linux-2.6-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64
--- a/linux-2.6-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64	2005-08-29 16:07:31.498779744 +0800
+++ b/linux-2.6-xen-sparse/arch/xen/configs/xen0_defconfig_x86_64	2005-08-29 16:05:39.164857096 +0800
@@ -195,6 +195,7 @@
 # CONFIG_BLK_DEV_CRYPTOLOOP is not set
 # CONFIG_BLK_DEV_NBD is not set
 # CONFIG_BLK_DEV_SX8 is not set
+# CONFIG_BLK_DEV_UB is not set
 CONFIG_BLK_DEV_RAM=y
 CONFIG_BLK_DEV_RAM_COUNT=16
 CONFIG_BLK_DEV_RAM_SIZE=16384