[Xen-ia64-devel] A patch to fix mis-setting ed bit for itlb entry.

["Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>]

Hi, Isaku 
    When debugging  a windows BSOD issue,  we found it is 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, so 
just purge the corresponding entry in hash vTLB and let guest OS to determin 
how to set ED bit for itlb mapping once found it. 
Xiantao

Signed-off-by : Xiantao Zhang <xiantao.zhang@xxxxxxxxx>

diff -r e97216802360 xen/arch/ia64/vmx/vtlb.c
--- a/xen/arch/ia64/vmx/vtlb.c  Fri Dec 12 10:43:39 2008 +0900
+++ b/xen/arch/ia64/vmx/vtlb.c  Sun Jan 04 10:43:19 2009 +0800
@@ -678,11 +678,20 @@ thash_data_t *vtlb_lookup(VCPU *v, u64 v
         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 (is_data == ISIDE_TLB && !cch->ed) {
+      /*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;
 }

Attachment: fix_itlb_ed.patch
Description: fix_itlb_ed.patch

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