MdePkg/Library/BaseLib/Ia32/ReadMsr64.c

   1 /** @file
   2   AsmReadMsr64 function
   3
   4   Copyright (c) 2006 - 2021, Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9
  10 #include <Library/RegisterFilterLib.h>
  11
  12 /**
  13   Returns a 64-bit Machine Specific Register(MSR).
  14
  15   Reads and returns the 64-bit MSR specified by Index. No parameter checking is
  16   performed on Index, and some Index values may cause CPU exceptions. The
  17   caller must either guarantee that Index is valid, or the caller must set up
  18   exception handlers to catch the exceptions. This function is only available
  19   on IA-32 and x64.
  20
  21   @param  Index The 32-bit MSR index to read.
  22
  23   @return The value of the MSR identified by Index.
  24
  25 **/
  26 UINT64
  27 AsmReadMsr64Internal (
  28   IN UINT32  Index
  29   )
  30 {
  31   _asm {
  32     mov     ecx, Index
  33     rdmsr
  34   }
  35 }
  36
  37 /**
  38   Returns a 64-bit Machine Specific Register(MSR).
  39
  40   Reads and returns the 64-bit MSR specified by Index. No parameter checking is
  41   performed on Index, and some Index values may cause CPU exceptions. The
  42   caller must either guarantee that Index is valid, or the caller must set up
  43   exception handlers to catch the exceptions. This function is only available
  44   on IA-32 and x64.
  45
  46   @param  Index The 32-bit MSR index to read.
  47
  48   @return The value of the MSR identified by Index.
  49
  50 **/
  51 UINT64
  52 EFIAPI
  53 AsmReadMsr64 (
  54   IN UINT32  Index
  55   )
  56 {
  57   UINT64                            Value;
  58   BOOLEAN                           Flag;
  59
  60   Flag = FilterBeforeMsrRead (Index, &Value);
  61   if (Flag) {
  62     Value = AsmReadMsr64Internal (Index);
  63   }
  64   FilterAfterMsrRead (Index, &Value);
  65
  66   return Value;
  67 }