+dnl Set drive interface used by the guestfs_add_drive{,_ro} calls
+dnl ('-drive ...,if=...' option to qemu).
+dnl
+dnl NB. We will change the default in future to virtio, but at the
+dnl moment this causes a performance problem, RHBZ#509383.
+AC_ARG_WITH([drive-if],
+ [AS_HELP_STRING([--with-drive-if],
+ [set default driver (ide|scsi|virtio) @<:@default=ide@:>@])],
+ [],
+ [with_drive_if=ide])
+AC_DEFINE_UNQUOTED([DRIVE_IF],["$with_drive_if"],[Default drive interface.])
+