MdePkg/Library/BaseLib/X86SpeculationBarrier.c

   1 /** @file
   2   SpeculationBarrier() function for IA32 and x64.
   3
   4   Copyright (C) 2018 - 2019, Intel Corporation. All rights reserved.<BR>
   5
   6   SPDX-License-Identifier: BSD-2-Clause-Patent
   7
   8 **/
   9
  10 #include <Library/BaseLib.h>
  11
  12 /**
  13   Uses as a barrier to stop speculative execution.
  14
  15   Ensures that no later instruction will execute speculatively, until all prior
  16   instructions have completed.
  17
  18 **/
  19 VOID
  20 EFIAPI
  21 SpeculationBarrier (
  22   VOID
  23   )
  24 {
  25   if (PcdGet8 (PcdSpeculationBarrierType) == 0x01) {
  26     AsmLfence ();
  27   } else if (PcdGet8 (PcdSpeculationBarrierType) == 0x02) {
  28     AsmCpuid (0x01, NULL, NULL, NULL, NULL);
  29   }
  30 }