+ * We need to make sure the read-modify-write
+ * of Status below isn't perturbed by an interrupt
+ * or cross-TC access, so we need to do at least a DMT,
+ * protected by an interrupt-inhibit. But setting IXMT
+ * also creates a few-cycle window where an IPI could
+ * be queued and not be detected before potentially
+ * returning to a WAIT or user-mode loop. It must be
+ * replayed.
+ *
+ * We're in the middle of a context switch, and
+ * we can't dispatch it directly without trashing
+ * some registers, so we'll try to detect this unlikely
+ * case and program a software interrupt in the VPE,
+ * as would be done for a cross-VPE IPI. To accomodate
+ * the handling of that case, we're doing a DVPE instead
+ * of just a DMT here to protect against other threads.
+ * This is a lot of cruft to cover a tiny window.
+ * If you can find a better design, implement it!
+ *