OvmfPkg/Library/BaseMemEncryptSevLib/PeiDxeMemEncryptSevLibInternal.c

   1 /** @file
   2
   3   Secure Encrypted Virtualization (SEV) library helper function
   4
   5   Copyright (c) 2017 - 2020, AMD Incorporated. All rights reserved.<BR>
   6
   7   SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 #include <Library/BaseLib.h>
  12 #include <Library/DebugLib.h>
  13 #include <Library/MemEncryptSevLib.h>
  14 #include <Library/PcdLib.h>
  15 #include <Register/QemuSmramSaveStateMap.h>
  16 #include <Register/SmramSaveStateMap.h>
  17 #include <Uefi/UefiBaseType.h>
  18
  19 /**
  20   Locate the page range that covers the initial (pre-SMBASE-relocation) SMRAM
  21   Save State Map.
  22
  23   @param[out] BaseAddress     The base address of the lowest-address page that
  24                               covers the initial SMRAM Save State Map.
  25
  26   @param[out] NumberOfPages   The number of pages in the page range that covers
  27                               the initial SMRAM Save State Map.
  28
  29   @retval RETURN_SUCCESS      BaseAddress and NumberOfPages have been set on
  30                               output.
  31
  32   @retval RETURN_UNSUPPORTED  SMM is unavailable.
  33 **/
  34 RETURN_STATUS
  35 EFIAPI
  36 MemEncryptSevLocateInitialSmramSaveStateMapPages (
  37   OUT UINTN  *BaseAddress,
  38   OUT UINTN  *NumberOfPages
  39   )
  40 {
  41   UINTN  MapStart;
  42   UINTN  MapEnd;
  43   UINTN  MapPagesStart; // MapStart rounded down to page boundary
  44   UINTN  MapPagesEnd;   // MapEnd rounded up to page boundary
  45   UINTN  MapPagesSize;  // difference between MapPagesStart and MapPagesEnd
  46
  47   if (!FeaturePcdGet (PcdSmmSmramRequire)) {
  48     return RETURN_UNSUPPORTED;
  49   }
  50
  51   MapStart      = SMM_DEFAULT_SMBASE + SMRAM_SAVE_STATE_MAP_OFFSET;
  52   MapEnd        = MapStart + sizeof (QEMU_SMRAM_SAVE_STATE_MAP);
  53   MapPagesStart = MapStart & ~(UINTN)EFI_PAGE_MASK;
  54   MapPagesEnd   = ALIGN_VALUE (MapEnd, EFI_PAGE_SIZE);
  55   MapPagesSize  = MapPagesEnd - MapPagesStart;
  56
  57   ASSERT ((MapPagesSize & EFI_PAGE_MASK) == 0);
  58
  59   *BaseAddress   = MapPagesStart;
  60   *NumberOfPages = MapPagesSize >> EFI_PAGE_SHIFT;
  61
  62   return RETURN_SUCCESS;
  63 }