+ /*
+ * Checking the C (changed) bit here is racy since there
+ * is no guarantee about when the hardware writes it back.
+ * If the HPTE is not writable then it is stable since the
+ * page can't be written to, and we would have done a tlbie
+ * (which forces the hardware to complete any writeback)
+ * when making the HPTE read-only.
+ * If vcpus are running then this call is racy anyway
+ * since the page could get dirtied subsequently, so we
+ * expect there to be a further call which would pick up
+ * any delayed C bit writeback.
+ * Otherwise we need to do the tlbie even if C==0 in
+ * order to pick up any delayed writeback of C.
+ */
+ if (!(hptep[1] & HPTE_R_C) &&
+ (!hpte_is_writable(hptep[1]) || vcpus_running(kvm)))