kexec: fix i386 EFI boot using efifb

Problem:
	kexec fails under i386 EFI boot for hardware that does not
have a VGA bios or PC bios present. The EFI bootloader properly set
the initial screen_info boot params but kexec assumes an
orig_video_isVGA type of 1. This causes the kexec'd kernel assume the
presence of both VGA bios and normal PC BIOS and starts probing which
then panics somewhere I can't see because I have no console output
nor serial ports.

Solution:
	For EFI, efifb is a linear VGA framebuffer and can handle the
kexec kernel switch, kexec just has to setup the kernel boot params
properly. The below patch fixes this issue and allow a i386 EFI
booted kernel with no VGA bios/PC bios to kexec to another kernel.

Questions:
	Why is kexec assuming i386 x86 == VGA bios in the first
place. The existing kernel has a perfectly good screen_info stucture
that is an exported symbol by the kernel and could be accessed by
kexec. Since kexec is just pretending to be a boot loader, why does
it ignore information that the real bootloader (which knows a lot
more about the hardware) has passed? The below patch just hacks in a
trap for efifb and will fail in the future as other x86 hardware
without VGA bios/PC bios become available.

Signed-off-by: Scott D Davilla <davilla@4pi.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

0 files changed, 0 insertions, 0 deletions