MdePkg/Library/BaseLib/Ia32/Mwait.c

   1 /** @file
   2   AsmMwait 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   Executes an MWAIT instruction.
  11
  12   Executes an MWAIT instruction with the register state specified by Eax and
  13   Ecx. Returns Eax. This function is only available on IA-32 and x64.
  14
  15   @param  RegisterEax The value to load into EAX or RAX before executing the MONITOR
  16                       instruction.
  17   @param  RegisterEcx The value to load into ECX or RCX before executing the MONITOR
  18                       instruction.
  19
  20   @return RegisterEax
  21
  22 **/
  23 UINTN
  24 EFIAPI
  25 AsmMwait (
  26   IN      UINTN                     RegisterEax,
  27   IN      UINTN                     RegisterEcx
  28   )
  29 {
  30   _asm {
  31     mov     eax, RegisterEax
  32     mov     ecx, RegisterEcx
  33     _emit   0x0f              // mwait
  34     _emit   0x01
  35     _emit   0xC9
  36   }
  37 }
  38