Index: xen-3.3.1-testing/xen/arch/x86/hvm/hvm.c
===================================================================
--- xen-3.3.1-testing.orig/xen/arch/x86/hvm/hvm.c	2009-02-12 09:23:34.000000000 -0700
+++ xen-3.3.1-testing/xen/arch/x86/hvm/hvm.c	2009-02-12 09:29:19.000000000 -0700
@@ -544,7 +544,25 @@
     if ( hvm_funcs.load_cpu_ctxt(v, &ctxt) < 0 )
         return -EINVAL;
 
+
+    /* Older Xen versions used to save the segment arbytes directly 
+     * from the VMCS on Intel hosts.  Detect this and rearrange them
+     * into the struct segment_register format. */
+
+#define UNFOLD_ARBYTES(_r)                          \
+    if ( (_r & 0xf000) && !(_r & 0x0f00) )          \
+        _r = ((_r & 0xff) | ((_r >> 4) & 0xf00))
+    UNFOLD_ARBYTES(ctxt.cs_arbytes);
+    UNFOLD_ARBYTES(ctxt.ds_arbytes);
+    UNFOLD_ARBYTES(ctxt.es_arbytes);
+    UNFOLD_ARBYTES(ctxt.fs_arbytes);
+    UNFOLD_ARBYTES(ctxt.gs_arbytes);
+    UNFOLD_ARBYTES(ctxt.ss_arbytes);
+    UNFOLD_ARBYTES(ctxt.tr_arbytes);
+    UNFOLD_ARBYTES(ctxt.ldtr_arbytes);
+#undef UNFOLD_ARBYTES
     seg.limit = ctxt.idtr_limit;
+
     seg.base = ctxt.idtr_base;
     hvm_set_segment_register(v, x86_seg_idtr, &seg);