diff -uNr xen-unstable.hg-pristine/tools/firmware/rombios/rombios.c xen-unstable.hg/tools/firmware/rombios/rombios.c
--- xen-unstable.hg-pristine/tools/firmware/rombios/rombios.c	2007-03-13 02:17:37.000000000 +0100
+++ xen-unstable.hg/tools/firmware/rombios/rombios.c	2007-03-13 12:12:50.000000000 +0100
@@ -4360,6 +4360,11 @@
           regs.u.r8.dl = inb_cmos(0x34);
           regs.u.r8.dh = inb_cmos(0x35);
 
+#ifdef HVMASSIST
+          // Don't report highest 64kb block, or shared_page & friends will get exposed as regular RAM
+          regs.u.r16.dx -= 1;
+#endif
+
           // Set configured memory equal to extended memory
           regs.u.r16.ax = regs.u.r16.cx;
           regs.u.r16.bx = regs.u.r16.dx;