The Kernel command line option
kgdb wait for a debugger connection during booting of a kernel. You
can only use this option if you compiled a kgdb I/O driver into the
kernel and you specified the I/O driver configuration as a kernel
command line option. The kgdbwait parameter should always follow the
configuration parameter for the kgdb I/O driver in the kernel
command line else the I/O driver will not be configured prior to
asking the kernel to use it to wait.
The kernel will stop and wait as early as the I/O driver and architecture allows when you use this option. If you build the kgdb I/O driver as a loadable kernel module kgdbwait will not do anything.