xen/blkback: Flesh out the description in the Kconfig.

	  block devices to other guests via a high-performance shared-memory

	  interface.

	  The corresponding Linux frontend driver is enabled by the

	  CONFIG_XEN_BLKDEV_FRONTEND configuration option.

	  The backend driver attaches itself to a any block device specified

	  in the XenBus configuration. There are no limits to what the block

	  device as long as it has a major and minor.

	  If you are compiling a kernel to run in a Xen block backend driver

	  domain (often this is domain 0) you should say Y here. To

	  compile this driver as a module, chose M here: the module

	  will be called xen-blkback.

config VIRTIO_BLK

	tristate "Virtio block driver (EXPERIMENTAL)"

	depends on EXPERIMENTAL && VIRTIO