kernel arguments

[kalpana]

root=/dev/vda ro vdso=0 showopts vga=normal console=tty1 console=ttyS0,115200 3

Under KVM the above parameters are fed to the kernel?

I get the root part. and the VGA part.

But I don't know what

vdso=0
showopts
and what the 3 is doing after the serial configuration. I have another that has 2 instead.


Obviously I googled these but I can't find the correct term for what I'm looking for, as its inconsistently referred to as kernel arguments, command line, args, boot arguments etc. Sometimes its the same thing sometimes not. I found man pages with vdso defined but I am none the wiser at all.
I have read various sources for console= but none of them have a 2 or 3 after them, and its hard to know if its part of the console parameter or something else. I thought it may be pipe messages to that device after we reach a certain run level or something.