OvmfPkg/TpmMmioSevDecryptPei: Mark TPM MMIO range as unencrypted for SEV-ES

[mirror_edk2.git] / OvmfPkg / Tcg / TpmMmioSevDecryptPei / TpmMmioSevDecryptPeim.c

/** @file\r
  Map TPM MMIO range unencrypted when SEV-ES is active.\r
  Install gOvmfTpmMmioAccessiblePpiGuid unconditionally.\r
\r
  Copyright (C) 2021, Advanced Micro Devices, Inc.\r
\r
  SPDX-License-Identifier: BSD-2-Clause-Patent\r
**/\r
\r
\r
#include <PiPei.h>\r
\r
#include <Library/DebugLib.h>\r
#include <Library/MemEncryptSevLib.h>\r
#include <Library/PcdLib.h>\r
#include <Library/PeiServicesLib.h>\r
\r
STATIC CONST EFI_PEI_PPI_DESCRIPTOR  mTpmMmioRangeAccessible = {\r
  EFI_PEI_PPI_DESCRIPTOR_PPI | EFI_PEI_PPI_DESCRIPTOR_TERMINATE_LIST,\r
  &gOvmfTpmMmioAccessiblePpiGuid,\r
  NULL\r
};\r
\r
/**\r
  The entry point for TPM MMIO range mapping driver.\r
\r
  @param[in]  FileHandle   Handle of the file being invoked.\r
  @param[in]  PeiServices  Describes the list of possible PEI Services.\r
\r
  @retval  EFI_ABORTED  No need to keep this PEIM resident\r
**/\r
EFI_STATUS\r
EFIAPI\r
TpmMmioSevDecryptPeimEntryPoint (\r
  IN       EFI_PEI_FILE_HANDLE  FileHandle,\r
  IN CONST EFI_PEI_SERVICES     **PeiServices\r
  )\r
{\r
  RETURN_STATUS                   DecryptStatus;\r
  EFI_STATUS                      Status;\r
\r
  DEBUG ((DEBUG_INFO, "%a\n", __FUNCTION__));\r
\r
  //\r
  // If SEV is active, MMIO succeeds against an encrypted physical address\r
  // because the nested page fault (NPF) that occurs on access does not\r
  // include the encryption bit in the guest physical address provided to the\r
  // hypervisor.\r
  //\r
  // If SEV-ES is active, MMIO would succeed against an encrypted physical\r
  // address because the #VC handler uses the virtual address (which is an\r
  // identity mapped physical address without the encryption bit) as the guest\r
  // physical address of the MMIO target in the VMGEXIT.\r
  //\r
  // However, if SEV-ES is active, before performing the actual MMIO, an\r
  // additional MMIO mitigation check is performed in the #VC handler to ensure\r
  // that MMIO is being done to/from an unencrypted address. To prevent guest\r
  // termination in this scenario, mark the range unencrypted ahead of access.\r
  //\r
  if (MemEncryptSevEsIsEnabled ()) {\r
    DEBUG ((DEBUG_INFO,\r
      "%a: mapping TPM MMIO address range unencrypted\n",\r
      __FUNCTION__));\r
\r
    DecryptStatus = MemEncryptSevClearPageEncMask (\r
                      0,\r
                      FixedPcdGet64 (PcdTpmBaseAddress),\r
                      EFI_SIZE_TO_PAGES ((UINTN) 0x5000),\r
                      FALSE\r
                      );\r
\r
    if (RETURN_ERROR (DecryptStatus)) {\r
      DEBUG ((DEBUG_ERROR,\r
        "%a: failed to map TPM MMIO address range unencrypted\n",\r
        __FUNCTION__));\r
      ASSERT_RETURN_ERROR (DecryptStatus);\r
    }\r
  }\r
\r
  //\r
  // MMIO range available\r
  //\r
  Status = PeiServicesInstallPpi (&mTpmMmioRangeAccessible);\r
  ASSERT_EFI_ERROR (Status);\r
\r
  return EFI_ABORTED;\r
}\r