There's always a chance we're unable to read a guest instruction. The guest
could have its TLB mapped execute-, but not readable, something odd happens
and our TLB gets flushed. So it's a good idea to be prepared for that case
and have a fallback that allows us to fix things up in that case.

Add fixup code that keeps guest code from potentially crashing our host kernel.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>