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   SPDX-License-Identifier: BSD-2-Clause-Patent
   7
   8 **/
   9
  10 #include <Library/BaseMemoryLib.h>
  11 #include <Library/DebugLib.h>
  12 #include <Library/PcdLib.h>
  13 #include <Library/MemEncryptSevLib.h>
  14
  15 #include "QemuFlash.h"
  16
  17 VOID
  18 QemuFlashBeforeProbe (
  19   IN  EFI_PHYSICAL_ADDRESS  BaseAddress,
  20   IN  UINTN                 FdBlockSize,
  21   IN  UINTN                 FdBlockCount
  22   )
  23 {
  24   EFI_STATUS  Status;
  25
  26   ASSERT (FeaturePcdGet (PcdSmmSmramRequire));
  27
  28   if (!MemEncryptSevIsEnabled ()) {
  29     return;
  30   }
  31
  32   //
  33   // When SEV is enabled, AmdSevDxe runs early in DXE phase and clears the
  34   // C-bit from the NonExistent entry -- which is later split and accommodate
  35   // the flash MMIO but the driver runs in non SMM context hence it cleared the
  36   // flash ranges from non SMM page table. When SMM is enabled, the flash
  37   // services are accessed from the SMM mode hence we explicitly clear the
  38   // C-bit on flash ranges from SMM page table.
  39   //
  40
  41   Status = MemEncryptSevClearMmioPageEncMask (
  42              0,
  43              BaseAddress,
  44              EFI_SIZE_TO_PAGES (FdBlockSize * FdBlockCount)
  45              );
  46   ASSERT_EFI_ERROR (Status);
  47 }
  48
  49 /**
  50   Write to QEMU Flash
  51
  52   @param[in] Ptr    Pointer to the location to write.
  53   @param[in] Value  The value to write.
  54
  55 **/
  56 VOID
  57 QemuFlashPtrWrite (
  58   IN        volatile UINT8  *Ptr,
  59   IN        UINT8           Value
  60   )
  61 {
  62   *Ptr = Value;
  63 }