use of setjmp/longjmp in x86 emulator.

[Gleb Natapov <gleb@redhat.com>]

I am looking at improving KVM x86 emulator. Current code does not
handle some special cases correctly (code execution from ROM, ins/outs
to/from MMIO) and many exception conditions during instruction emulation
are not handled correctly. There is a lot of code in emulator that is
there only for exception propagation. Using setjmp/longjmp will be very
beneficial here as exception condition during instruction execution
maps very naturally to setjmp/longjmp, so my question is what about
adding setjmp/longjmp implementation to the kernel, or alternatively,
if there is a fear that it can be abused, add it locally to emulator.c?
Note that instruction emulation is always done in process context.

--
			Gleb.