MdePkg/Library/BaseLib/Ia32/Mwait.c

   1 /** @file
   2   AsmMwait 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   Executes an MWAIT instruction.
  20
  21   Executes an MWAIT instruction with the register state specified by Eax and
  22   Ecx. Returns Eax. This function is only available on IA-32 and X64.
  23
  24   @param  Eax The value to load into EAX or RAX before executing the MONITOR
  25               instruction.
  26   @param  Ecx The value to load into ECX or RCX before executing the MONITOR
  27               instruction.
  28
  29   @return Eax
  30
  31 **/
  32 UINTN
  33 EFIAPI
  34 AsmMwait (
  35   IN      UINTN                     RegisterEax,
  36   IN      UINTN                     RegisterEcx
  37   )
  38 {
  39   _asm {
  40     mov     eax, RegisterEax
  41     mov     ecx, RegisterEcx
  42     _emit   0x0f              // mwait
  43     _emit   0x01
  44     _emit   0xC9
  45   }
  46 }
  47