Implement call32 mechanism using SMIs.

Add support for jumping into 32bit mode using a System Management Mode
(SMM) handler.  When available, this allows SeaBIOS to transition to
32bit mode even when called in vm86 mode.  It will also prevent the
clobbering of the segment registers.

Currently, the SMM mode is only supported in QEMU when running in TCG
mode.  Also, QEMU v2.1 (or later) is needed for it to work when in
vm86 mode.

Signed-off-by: Kevin O'Connor <>
4 files changed