All our useful entry points into the hypervisor are starting by saving x0 and x1 on the stack. Let's move those into the vectors by introducing macros that annotate whether a vector is valid or not, thus indicating whether we want to stash registers or not. The only drawback is that we now also stash registers for el2_error, but this should never happen, and we pop them back right at the start of the handling sequence. Acked-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>