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[Xen-devel] about fixup_page_fault

I guess I may miss sth important, but I don't understand below
code at end of fixup_page_fault:

    if ( paging_mode_enabled(d) )
        int ret = paging_fault(addr, regs);
        if ( ret == EXCRET_fault_fixed )
            trace_trap_two_addr(TRC_PV_PAGING_FIXUP, regs->eip, addr);
        return ret;

Shouldn't a check upon guest_mode(regs) is required, since the
fault may be triggered by xen itself? For example, a null pointer
deference by xen code (not passed from guest) may not get chance
to reach "fatal page fault" and instead a guest page fault could be
injected per my reading...

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