Index: /trunk/src/VBox/Devices/PC/DevIOAPIC_New.cpp
===================================================================
--- /trunk/src/VBox/Devices/PC/DevIOAPIC_New.cpp	(revision 61848)
+++ /trunk/src/VBox/Devices/PC/DevIOAPIC_New.cpp	(revision 61849)
@@ -467,6 +467,9 @@
     {
         /*
-         * Write the low or high 32-bit value into the specified 64-bit RTE register.
-         * Update only the valid, writable bits.
+         * Write the low or high 32-bit value into the specified 64-bit RTE register,
+         * update only the valid, writable bits.
+         *
+         * We need to preserve the read-only bits as it can have dire consequences
+         * otherwise, see @bugref{8386#c24}.
          */
         uint64_t const u64Rte = pThis->au64RedirTable[idxRte];