[Xen-changelog] [xen-unstable] x86/HVM: fixed _hvm_hw_fix_cpu()

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Razvan Cojocaru <rzvncj@xxxxxxxxx>
# Date 1359036499 -3600
# Node ID e0b21f16be125ec67c288dc01c09d6312bc82a3c
# Parent  e7de3330b64cc66cd559d9b570a84a421cd99b44
x86/HVM: fixed _hvm_hw_fix_cpu()

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

Signed-off-by: Razvan Cojocaru <rzvncj@xxxxxxxxx>
Acked-by: Tim Deegan <tim@xxxxxxx>
Acked-by: Keir Fraser <keir@xxxxxxx>
Committed-by: Jan Beulich <jbeulich@xxxxxxxx>
---


diff -r e7de3330b64c -r e0b21f16be12 xen/include/public/arch-x86/hvm/save.h
--- a/xen/include/public/arch-x86/hvm/save.h    Thu Jan 24 14:49:14 2013 +0100
+++ b/xen/include/public/arch-x86/hvm/save.h    Thu Jan 24 15:08:19 2013 +0100
@@ -269,15 +269,18 @@ 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;
+    } *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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