[XEN] Be sure to discard old PAE l2 shadows when guest l2e becomes null.

This fixes recent PAE live migrate failures.
Signed-off-by: Tim Deegan <Tim.Deegan@xensource.com>

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index d2e7b302ba494dcd919906adbef424a5fea04fb8..8a83d4de07dd11d0021fb1c726779869cba60969 100644 (file)
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -3488,6 +3488,9 @@ sh_update_cr3(struct vcpu *v)
                                        ? SH_type_l2h_shadow 
                                        : SH_type_l2_shadow);
             }
+            else
+                /* The guest is not present: clear out the shadow. */
+                sh_set_toplevel_shadow(v, i, _mfn(INVALID_MFN), 0); 
         }
     }
 #elif GUEST_PAGING_LEVELS == 4