OvmfPkg/Library/BaseMemEncryptSevLib/X64/PeiSnpSystemRamValidate.c

   1 /** @file
   2
   3   SEV-SNP Page Validation functions.
   4
   5   Copyright (c) 2021 AMD Incorporated. All rights reserved.<BR>
   6
   7   SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 #include <Uefi/UefiBaseType.h>
  12 #include <Library/BaseLib.h>
  13 #include <Library/MemEncryptSevLib.h>
  14
  15 #include "SnpPageStateChange.h"
  16
  17 typedef struct {
  18   UINT64    StartAddress;
  19   UINT64    EndAddress;
  20 } SNP_PRE_VALIDATED_RANGE;
  21
  22 STATIC SNP_PRE_VALIDATED_RANGE  mPreValidatedRange[] = {
  23   // The below address range was part of the SEV OVMF metadata, and range
  24   // should be pre-validated by the Hypervisor.
  25   {
  26     FixedPcdGet32 (PcdOvmfSecPageTablesBase),
  27     FixedPcdGet32 (PcdOvmfPeiMemFvBase),
  28   },
  29 };
  30
  31 STATIC
  32 BOOLEAN
  33 DetectPreValidatedOverLap (
  34   IN    PHYSICAL_ADDRESS         StartAddress,
  35   IN    PHYSICAL_ADDRESS         EndAddress,
  36   OUT   SNP_PRE_VALIDATED_RANGE  *OverlapRange
  37   )
  38 {
  39   UINTN  i;
  40
  41   //
  42   // Check if the specified address range exist in pre-validated array.
  43   //
  44   for (i = 0; i < ARRAY_SIZE (mPreValidatedRange); i++) {
  45     if ((mPreValidatedRange[i].StartAddress < EndAddress) &&
  46         (StartAddress < mPreValidatedRange[i].EndAddress))
  47     {
  48       OverlapRange->StartAddress = mPreValidatedRange[i].StartAddress;
  49       OverlapRange->EndAddress   = mPreValidatedRange[i].EndAddress;
  50       return TRUE;
  51     }
  52   }
  53
  54   return FALSE;
  55 }
  56
  57 /**
  58   Pre-validate the system RAM when SEV-SNP is enabled in the guest VM.
  59
  60   @param[in]  BaseAddress             Base address
  61   @param[in]  NumPages                Number of pages starting from the base address
  62
  63 **/
  64 VOID
  65 EFIAPI
  66 MemEncryptSevSnpPreValidateSystemRam (
  67   IN PHYSICAL_ADDRESS  BaseAddress,
  68   IN UINTN             NumPages
  69   )
  70 {
  71   PHYSICAL_ADDRESS         EndAddress;
  72   SNP_PRE_VALIDATED_RANGE  OverlapRange;
  73
  74   if (!MemEncryptSevSnpIsEnabled ()) {
  75     return;
  76   }
  77
  78   EndAddress = BaseAddress + EFI_PAGES_TO_SIZE (NumPages);
  79
  80   while (BaseAddress < EndAddress) {
  81     //
  82     // Check if the range overlaps with the pre-validated ranges.
  83     //
  84     if (DetectPreValidatedOverLap (BaseAddress, EndAddress, &OverlapRange)) {
  85       // Validate the non-overlap regions.
  86       if (BaseAddress < OverlapRange.StartAddress) {
  87         NumPages = EFI_SIZE_TO_PAGES (OverlapRange.StartAddress - BaseAddress);
  88
  89         InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE);
  90       }
  91
  92       BaseAddress = OverlapRange.EndAddress;
  93       continue;
  94     }
  95
  96     // Validate the remaining pages.
  97     NumPages = EFI_SIZE_TO_PAGES (EndAddress - BaseAddress);
  98     InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE);
  99     BaseAddress = EndAddress;
 100   }
 101 }