audk/OvmfPkg/PlatformPei/AmdSev.c

/**@file
  Initialize Secure Encrypted Virtualization (SEV) support

  Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>

  This program and the accompanying materials
  are licensed and made available under the terms and conditions of the BSD
  License which accompanies this distribution.  The full text of the license
  may be found at http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/
//
// The package level header files this module uses
//
#include <PiPei.h>

#include <Library/DebugLib.h>
#include <Library/PcdLib.h>
#include <Register/Cpuid.h>
#include <Register/Amd/Cpuid.h>
#include <Library/MemEncryptSevLib.h>

/**

  Function checks if SEV support is available, if present then it sets
  the dynamic PcdPteMemoryEncryptionAddressOrMask with memory encryption mask.

  **/
VOID
EFIAPI
AmdSevInitialize (
  VOID
  )
{
  CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
  UINT64                            EncryptionMask;
  RETURN_STATUS                     PcdStatus;

  //
  // Check if SEV is enabled
  //
  if (!MemEncryptSevIsEnabled ()) {
    return;
  }

  //
  // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
  //
  AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
  EncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);

  //
  // Set Memory Encryption Mask PCD
  //
  PcdStatus = PcdSet64S (PcdPteMemoryEncryptionAddressOrMask, EncryptionMask);
  ASSERT_RETURN_ERROR (PcdStatus);

  DEBUG ((DEBUG_INFO, "SEV is enabled (mask 0x%lx)\n", EncryptionMask));

  //
  // Set Pcd to Deny the execution of option ROM when security
  // violation.
  //
  PcdStatus = PcdSet32S (PcdOptionRomImageVerificationPolicy, 0x4);
  ASSERT_RETURN_ERROR (PcdStatus);
}