PSL_IOPL
tf->tf_rflags |= PSL_IOPL;
tf->tf_rflags &= ~PSL_IOPL;
iopl = (rflags & PSL_IOPL) >> 12;
#define PSL_USERSTATIC (PSL_MBO | PSL_MBZ | PSL_I | PSL_IOPL | PSL_NT | PSL_VM | PSL_VIF | PSL_VIP)
tf->tf_eflags |= PSL_IOPL;
tf->tf_eflags &= ~PSL_IOPL;
#define PSL_USERSTATIC (PSL_MBO | PSL_MBZ | PSL_I | PSL_IOPL | PSL_NT | PSL_VM | PSL_VIF | PSL_VIP)