[Xen-changelog] [xen-unstable] [XEN] Fix PAE PDPT shadowing coherence.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 69f7e0ea2985e6a8bd013740e8d76ad94de8e07b
# Parent  46e853c34a2eb537bbac8f45ba6adda949d305f0
[XEN] Fix PAE PDPT shadowing coherence.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
 xen/arch/x86/mm.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff -r 46e853c34a2e -r 69f7e0ea2985 xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Tue Jun 20 14:45:46 2006 +0100
+++ b/xen/arch/x86/mm.c Tue Jun 20 17:04:13 2006 +0100
@@ -268,18 +268,20 @@ void share_xen_page_with_privileged_gues
 
 #if defined(CONFIG_X86_PAE)
 
-#if 1 /*def NDEBUG*/ /* KAF: Non-debug case is suspect: let's always use it. */
+#ifdef NDEBUG
 /* Only PDPTs above 4GB boundary need to be shadowed in low memory. */
 #define l3tab_needs_shadow(mfn) ((mfn) >= 0x100000)
 #else
 /*
- * In debug builds we aggressively shadow PDPTs to exercise code paths.
+ * In debug builds we shadow a selection of <4GB PDPTs to exercise code paths.
  * We cannot safely shadow the idle page table, nor shadow-mode page tables
- * (detected by lack of an owning domain). Always shadow PDPTs above 4GB.
+ * (detected by lack of an owning domain). As required for correctness, we
+ * always shadow PDPTs aboive 4GB.
  */
 #define l3tab_needs_shadow(mfn)                         \
     (((((mfn) << PAGE_SHIFT) != __pa(idle_pg_table)) && \
-      (page_get_owner(mfn_to_page(mfn)) != NULL)) ||    \
+      (page_get_owner(mfn_to_page(mfn)) != NULL) &&     \
+      ((mfn) & 1)) || /* odd MFNs are shadowed */       \
      ((mfn) >= 0x100000))
 #endif
 
@@ -305,6 +307,8 @@ static void __write_ptbase(unsigned long
     if ( !l3tab_needs_shadow(mfn) )
     {
         write_cr3(mfn << PAGE_SHIFT);
+        /* Cache is no longer in use or valid (/after/ write to %cr3). */
+        cache->high_mfn = 0;
         return;
     }
 

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