vmcb_regptr
fieldp = vmcb_regptr(vmcb, ident, NULL);
fieldp = vmcb_regptr(vmcb, ident, &dirty);
fieldp = vmcb_regptr(vmcb, ident, &dirty);
uint64_t *vmcb_regptr(struct vmcb *vmcb, int ident, uint32_t *dirtyp);