pygrub doesn't parse keyboard input while in boot menu. xen-3.0.2-3 no workaround found. start an xterm (or login to linux console) boot a xen guest with bootloader set to /usr/bin/pygrub: xm create -c guest1 hit 'a' during the boot process at the pygrub menu. no detectable effect on bot process. Expected to edit the kernel command line This prevents disabling selinux in guests or single-user mode startup in guests, which greatly hinders debugging.
Not so much "not parsing input" as "doesn't have everything implemented" ;-) I'll try to flesh out basic command line editing later, as it shouldn't be that bad to do.
This is done now