OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlashSmm.c

   1 /** @file
   2   Define the module hooks used while probing the QEMU flash device.
   3
   4   Copyright (C) 2018, Advanced Micro Devices. All rights reserved.
   5
   6   This program and the accompanying materials are licensed and made available
   7   under the terms and conditions of the BSD License which accompanies this
   8   distribution.  The full text of the license may be found at
   9   http://opensource.org/licenses/bsd-license.php
  10
  11   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 #include <Library/BaseMemoryLib.h>
  17 #include <Library/DebugLib.h>
  18 #include <Library/PcdLib.h>
  19 #include <Library/MemEncryptSevLib.h>
  20
  21 #include "QemuFlash.h"
  22
  23 VOID
  24 QemuFlashBeforeProbe (
  25   IN  EFI_PHYSICAL_ADDRESS    BaseAddress,
  26   IN  UINTN                   FdBlockSize,
  27   IN  UINTN                   FdBlockCount
  28   )
  29 {
  30   EFI_STATUS              Status;
  31
  32   ASSERT (FeaturePcdGet (PcdSmmSmramRequire));
  33
  34   if (!MemEncryptSevIsEnabled ()) {
  35     return;
  36   }
  37
  38   //
  39   // When SEV is enabled, AmdSevDxe runs early in DXE phase and clears the
  40   // C-bit from the NonExistent entry -- which is later split and accommodate
  41   // the flash MMIO but the driver runs in non SMM context hence it cleared the
  42   // flash ranges from non SMM page table. When SMM is enabled, the flash
  43   // services are accessed from the SMM mode hence we explicitly clear the
  44   // C-bit on flash ranges from SMM page table.
  45   //
  46
  47   Status = MemEncryptSevClearPageEncMask (
  48              0,
  49              BaseAddress,
  50              EFI_SIZE_TO_PAGES (FdBlockSize * FdBlockCount),
  51              FALSE
  52              );
  53   ASSERT_EFI_ERROR (Status);
  54 }