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 // Include common header file for this module.
  17 //
  18
  19
  20 /**
  21   Writes a 64-bit value to a Machine Specific Register(MSR), and returns the
  22   value.
  23
  24   Writes the 64-bit value specified by Value to the MSR specified by Index. The
  25   64-bit value written to the MSR is returned. No parameter checking is
  26   performed on Index or Value, and some of these may cause CPU exceptions. The
  27   caller must either guarantee that Index and Value are valid, or the caller
  28   must establish proper exception handlers. This function is only available on
  29   IA-32 and X64.
  30
  31   @param  Index The 32-bit MSR index to write.
  32   @param  Value The 64-bit value to write to the MSR.
  33
  34   @return Value
  35
  36 **/
  37 UINT64
  38 EFIAPI
  39 AsmWriteMsr64 (
  40   IN UINT32  Index,
  41   IN UINT64  Value
  42   )
  43 {
  44   _asm {
  45     mov     edx, dword ptr [Value + 4]
  46     mov     eax, dword ptr [Value + 0]
  47     mov     ecx, Index
  48     wrmsr
  49   }
  50 }
  51