MdePkg/Library/BaseLib/Ia32/WriteMsr64.c

   1 /** @file
   2   AsmWriteMsr64 function
   3
   4   Copyright (c) 2006 - 2007, Intel Corporation<BR>
   5   All rights reserved. This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15
  16
  17
  18 /**
  19   Writes a 64-bit value to a Machine Specific Register(MSR), and returns the
  20   value.
  21
  22   Writes the 64-bit value specified by Value to the MSR specified by Index. The
  23   64-bit value written to the MSR is returned. No parameter checking is
  24   performed on Index or Value, and some of these may cause CPU exceptions. The
  25   caller must either guarantee that Index and Value are valid, or the caller
  26   must establish proper exception handlers. This function is only available on
  27   IA-32 and X64.
  28
  29   @param  Index The 32-bit MSR index to write.
  30   @param  Value The 64-bit value to write to the MSR.
  31
  32   @return Value
  33
  34 **/
  35 UINT64
  36 EFIAPI
  37 AsmWriteMsr64 (
  38   IN UINT32  Index,
  39   IN UINT64  Value
  40   )
  41 {
  42   _asm {
  43     mov     edx, dword ptr [Value + 4]
  44     mov     eax, dword ptr [Value + 0]
  45     mov     ecx, Index
  46     wrmsr
  47   }
  48 }
  49