--- xnu/xnu-1699.22.81/iokit/Kernel/IOBufferMemoryDescriptor.cpp
+++ xnu/xnu-1504.9.26/iokit/Kernel/IOBufferMemoryDescriptor.cpp
@@ -103,6 +103,16 @@
     // Grab IOMD bits from the Buffer MD options
     iomdOptions  |= (options & kIOBufferDescriptorMemoryFlags);
 
+#if 0
+    // workarounds-
+    if ((options & kIOMemoryPhysicallyContiguous) || ((capacity == 0x1000) && (inTask == kernel_task))
+      && !physicalMask)
+    {
+	highestMask = physicalMask = 0xFFFFF000;
+    }
+    //-
+#endif
+
     if (physicalMask && (alignment <= 1))
     {
 	alignment   = ((physicalMask ^ (-1ULL)) & (physicalMask - 1));