+ one is chosen dynamically.
+
+config BLK_DEV_UBD
+ bool "Virtual block device"
+ depends on UML
+ ---help---
+ The User-Mode Linux port includes a driver called UBD which will let
+ you access arbitrary files on the host computer as block devices.
+ Unless you know that you do not need such virtual block devices say
+ Y here.
+
+config BLK_DEV_UBD_SYNC
+ bool "Always do synchronous disk IO for UBD"
+ depends on BLK_DEV_UBD
+ ---help---
+ Writes to the virtual block device are not immediately written to the
+ host's disk; this may cause problems if, for example, the User-Mode
+ Linux 'Virtual Machine' uses a journalling filesystem and the host
+ computer crashes.
+
+ Synchronous operation (i.e. always writing data to the host's disk
+ immediately) is configurable on a per-UBD basis by using a special
+ kernel command line option. Alternatively, you can say Y here to
+ turn on synchronous operation by default for all block devices.
+
+ If you're running a journalling file system (like reiserfs, for
+ example) in your virtual machine, you will want to say Y here. If
+ you care for the safety of the data in your virtual machine, Y is a
+ wise choice too. In all other cases (for example, if you're just
+ playing around with User-Mode Linux) you can choose N.
+
+config BLK_DEV_COW_COMMON
+ bool
+ default BLK_DEV_UBD
+
+config MMAPPER
+ tristate "Example IO memory driver (BROKEN)"
+ depends on UML && BROKEN
+ ---help---
+ The User-Mode Linux port can provide support for IO Memory
+ emulation with this option. This allows a host file to be
+ specified as an I/O region on the kernel command line. That file
+ will be mapped into UML's kernel address space where a driver can
+ locate it and do whatever it wants with the memory, including
+ providing an interface to it for UML processes to use.
+
+ For more information, see
+ <http://user-mode-linux.sourceforge.net/iomem.html>.
+
+ If you'd like to be able to provide a simulated IO port space for
+ User-Mode Linux processes, say Y. If unsure, say N.