https://bugzilla.kernel.org/show_bug.cgi?id=49531
--- Comment #4 from Igor Murzov e-mail@date.by 2012-10-25 19:58:36 --- I use xorg-server-1.12.3 and i'm not switching GPUs while X is running. I've tried to power down unused GPU and then kernel crashed. Switching GPUs while X is running doesn't work:
[ 6514.980755] vga_switcheroo: client 0 refused switch