MdePkg/Library/BaseLib/Ia32/WriteMsr64.c

   1 /** @file
   2   AsmWriteMsr64 function
   3
   4   Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9
  10
  11
  12 /**
  13   Writes a 64-bit value to a Machine Specific Register(MSR), and returns the
  14   value.
  15
  16   Writes the 64-bit value specified by Value to the MSR specified by Index. The
  17   64-bit value written to the MSR is returned. No parameter checking is
  18   performed on Index or Value, and some of these may cause CPU exceptions. The
  19   caller must either guarantee that Index and Value are valid, or the caller
  20   must establish proper exception handlers. This function is only available on
  21   IA-32 and x64.
  22
  23   @param  Index The 32-bit MSR index to write.
  24   @param  Value The 64-bit value to write to the MSR.
  25
  26   @return Value
  27
  28 **/
  29 UINT64
  30 EFIAPI
  31 AsmWriteMsr64 (
  32   IN UINT32  Index,
  33   IN UINT64  Value
  34   )
  35 {
  36   _asm {
  37     mov     edx, dword ptr [Value + 4]
  38     mov     eax, dword ptr [Value + 0]
  39     mov     ecx, Index
  40     wrmsr
  41   }
  42 }
  43