Index: /trunk/src/VBox/Runtime/common/asm/ASMRdMsrEx.asm
===================================================================
--- /trunk/src/VBox/Runtime/common/asm/ASMRdMsrEx.asm	(revision 49847)
+++ /trunk/src/VBox/Runtime/common/asm/ASMRdMsrEx.asm	(revision 49848)
@@ -45,5 +45,5 @@
         [pushreg rdi]
 [endprolog]
-        and     ecx, 0ffffffffh         ; serious paranoia
+        and     ecx, ecx                ; serious paranoia
         mov     rdi, rdx
         xor     eax, eax
@@ -51,4 +51,7 @@
         rdmsr
         pop     rdi
+        and     eax, eax                ; paranoia
+        shl     rdx, 32
+        or      rax, rdx
         ret
 endproc_frame
@@ -59,4 +62,7 @@
         xor     edx, edx
         rdmsr
+        and     eax, eax                ; paranoia
+        shl     rdx, 32
+        or      rax, rdx
         ret
 %elifdef RT_ARCH_X86
Index: /trunk/src/VBox/Runtime/common/asm/ASMWrMsrEx.asm
===================================================================
--- /trunk/src/VBox/Runtime/common/asm/ASMWrMsrEx.asm	(revision 49847)
+++ /trunk/src/VBox/Runtime/common/asm/ASMWrMsrEx.asm	(revision 49848)
@@ -45,5 +45,5 @@
         [pushreg rdi]
 [endprolog]
-        and     ecx, 0ffffffffh         ; serious paranoia
+        and     ecx, ecx                ; serious paranoia
         mov     rdi, rdx
         mov     eax, r8d