From: Bill Burns <bburns@redhat.com>
Date: Tue, 18 Dec 2007 15:56:08 -0500
Subject: [xen] improve checking in vcpu_destroy_pagetables
Message-id: 20071218205608.15371.86736.sendpatchset@localhost.localdomain
O-Subject: [RHEL5.2 PATCH 3/3] Improve checking in vcpu_destroy_pagetables
Bugzilla: 227614

x86, 32-on-64: Improve checking in vcpu_destroy_pagetables(). It *is*
possible for 64-bit guest to have matching guest_table and
guest_table_user.
Original patch by John Levon <levon@movementarian.org>
Signed-off-by: Keir Fraser <keir.fraser@eu.citrix.com>
xen-unstable changeset: 16401:f62e6c697eeb68a7a62f4beb87e85a68b91b3c6a
xen-unstable date: Tue Nov 20 15:34:25 2007 +0000

Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: "Stephen C. Tweedie" <sct@redhat.com>
Acked-by: Chris Lalancette <clalance@redhat.com>

diff --git a/arch/x86/domain.c b/arch/x86/domain.c
index 215d4f2..46ea2a0 100644
--- a/arch/x86/domain.c
+++ b/arch/x86/domain.c
@@ -1681,10 +1681,6 @@ static void vcpu_destroy_pagetables(struct vcpu *v)
             put_page(mfn_to_page(pfn));
         else
             put_page_and_type(mfn_to_page(pfn));
-#ifdef __x86_64__
-        if ( pfn == pagetable_get_pfn(v->arch.guest_table_user) )
-            v->arch.guest_table_user = pagetable_null();
-#endif
         v->arch.guest_table = pagetable_null();
     }
 
@@ -1693,10 +1689,13 @@ static void vcpu_destroy_pagetables(struct vcpu *v)
     pfn = pagetable_get_pfn(v->arch.guest_table_user);
     if ( pfn != 0 )
     {
-        if ( paging_mode_refcounts(d) )
-            put_page(mfn_to_page(pfn));
-        else
-            put_page_and_type(mfn_to_page(pfn));
+        if ( !is_pv_32bit_vcpu(v) )
+        {
+            if ( paging_mode_refcounts(d) )
+                put_page(mfn_to_page(pfn));
+            else
+                put_page_and_type(mfn_to_page(pfn));
+        }
         v->arch.guest_table_user = pagetable_null();
     }
 #endif