From: Chris Lalancette <clalance@redhat.com>
Date: Thu, 5 Mar 2009 14:21:20 +0100
Subject: [xen] ia64: fix windows 2003 BSOD
Message-id: 49AFD1D0.20002@redhat.com
O-Subject: [RHEL5.4 PATCH]: Fix ia64 Xen windows 2003 BSOD
Bugzilla: 479923
RH-Acked-by: Rik van Riel <riel@redhat.com>

All,
     This patch fixes a windows BSOD issue caused by mis-setting pte's ED bit
for itlb entry.  For hash vTLB, it uses unified tlb and doesn't differentiate
itc and dtc in its implementation, so itlb_miss handler may reference dtlb entry
in hash vTLB.
     But it may result in issues, because dtlb's ED bit may be different with
itlb's setting.  Since the case is very rare, just purge the corresponding entry
in hash vTLB and let the guest OS determine how to set ED bit for itlb mapping
once found it.
     Tested by the reporter to fix the BSOD issue in the Windows 2003 guest.  A
backport of xen-unstable c/s 18992, this should resolve BZ 479923.  Please
review and ACK.

--
Chris Lalancette

diff --git a/arch/ia64/vmx/vtlb.c b/arch/ia64/vmx/vtlb.c
index c03c5aa..8329bbe 100644
--- a/arch/ia64/vmx/vtlb.c
+++ b/arch/ia64/vmx/vtlb.c
@@ -673,11 +673,20 @@ thash_data_t *vtlb_lookup(VCPU *v, u64 va,int is_data)
         cch = vtlb_thash(hcb->pta, va, vrr.rrval, &tag);
         do {
             if (cch->etag == tag && cch->ps == ps)
-                return cch;
+                goto found;
             cch = cch->next;
         } while(cch);
     }
     return NULL;
+found:
+    if (unlikely(!cch->ed && is_data == ISIDE_TLB)) {
+        /*The case is very rare, and it may lead to incorrect setting
+          for itlb's ed bit! Purge it from hash vTLB and let guest os
+          determin the ed bit of the itlb entry.*/
+        vtlb_purge(v, va, ps);
+        cch = NULL;
+    }
+    return cch;
 }