I don't think we can use swapgs.  The problem with swapgs is that it's
    a swap, not a load, which means it can only be used at the syscall
    interface and can't be used at the interrupt or exception interface.

					-Matt
					Matthew Dillon 
					<dillon@backplane.com>

You can check the stack frame for the RIP and if it is alreday in the
kernel, you can skip the swapgs. Given that you have to do more work for
traps from userland anyway, that's a relatively cheap change.

Joerg