MdePkg/Library/BaseLib/Ia32/Mwait.c

   1 /** @file
   2   AsmMwait function
   3
   4   Copyright (c) 2006 - 2008, Intel Corporation. All rights reserved.<BR>
   5   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   Executes an MWAIT instruction.
  17
  18   Executes an MWAIT instruction with the register state specified by Eax and
  19   Ecx. Returns Eax. This function is only available on IA-32 and x64.
  20
  21   @param  RegisterEax The value to load into EAX or RAX before executing the MONITOR
  22                       instruction.
  23   @param  RegisterEcx The value to load into ECX or RCX before executing the MONITOR
  24                       instruction.
  25
  26   @return RegisterEax
  27
  28 **/
  29 UINTN
  30 EFIAPI
  31 AsmMwait (
  32   IN      UINTN                     RegisterEax,
  33   IN      UINTN                     RegisterEcx
  34   )
  35 {
  36   _asm {
  37     mov     eax, RegisterEax
  38     mov     ecx, RegisterEcx
  39     _emit   0x0f              // mwait
  40     _emit   0x01
  41     _emit   0xC9
  42   }
  43 }
  44