Setting up hypervisor_callback and testing

[Ivan Kelly <ivan@ivankelly.net>]

im setting up my hypervisor callback with:
hypervisor_set_callbacks(CS_SELECTOR, (unsigned long)hypervisor_callback,
			 CS_SELECTOR, (unsigned long)failsafe_callback);
hypervisor_callback and failsafe_callback are as yet very simple assembly
funcations that just shutdown the domain.
<SNIP>
_hypervisor_callback:
        call    _hypervisor_shutdown
        ret

_failsafe_callback:
        call    _hypervisor_shutdown
        ret
</SNIP>

Im trying to test it with:
<SNIP>
_xen_cb_test:
        call    _hypervisor_save_kernel_stack
        mov     esi, _hypervisor_shared_info
        mov     1(esi), 0
        push    0
        push    __HYPERVISOR_xen_version
        call    _xen_op
        add     esp, 4*2
        ret
</SNIP>

The callback doesn't seem to be getting called at all. At the moment im only
trying to get very basic callback stuff working, so i've left out the save and
iret stuff. Could anyone point out where im going wrong?
Regards
Ivan Kelly