[Xen-devel] [PATCH 2 of 2 V4] x86/HVM: fixed _hvm_hw_fix_cpu()

[Razvan Cojocaru <rzvncj@xxxxxxxxx>]

Prevent the compiler from re-ordering the reads and writes.
Suggested by Jan Beulich.

Signed-off-by: Razvan Cojocaru <rzvncj@xxxxxxxxx>

diff -r 3a9979cf50f3 -r 550e437674c7 xen/include/public/arch-x86/hvm/save.h
--- a/xen/include/public/arch-x86/hvm/save.h    Wed Jan 23 17:27:20 2013 +0200
+++ b/xen/include/public/arch-x86/hvm/save.h    Wed Jan 23 17:44:20 2013 +0200
@@ -269,15 +269,20 @@ struct hvm_hw_cpu_compat {
 };
 
 static inline int _hvm_hw_fix_cpu(void *h) {
-    struct hvm_hw_cpu *new=h;
-    struct hvm_hw_cpu_compat *old=h;
+
+    union hvm_hw_cpu_union {
+        struct hvm_hw_cpu nat;
+        struct hvm_hw_cpu_compat cmp;
+    };
+
+    union hvm_hw_cpu_union *ucpu = (union hvm_hw_cpu_union *)h;;
 
     /* If we copy from the end backwards, we should
      * be able to do the modification in-place */
-    new->error_code=old->error_code;
-    new->pending_event=old->pending_event;
-    new->tsc=old->tsc;
-    new->msr_tsc_aux=0;
+    ucpu->nat.error_code = ucpu->cmp.error_code;
+    ucpu->nat.pending_event = ucpu->cmp.pending_event;
+    ucpu->nat.tsc = ucpu->cmp.tsc;
+    ucpu->nat.msr_tsc_aux = 0;
 
     return 0;
 }

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