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/PcdLib.h>
  14 #include <Library/DebugLib.h>
  15 #include <Library/MemEncryptSevLib.h>
  16
  17 #include "SnpPageStateChange.h"
  18 #include "VirtualMemory.h"
  19
  20 typedef struct {
  21   UINT64    StartAddress;
  22   UINT64    EndAddress;
  23 } SNP_PRE_VALIDATED_RANGE;
  24
  25 STATIC SNP_PRE_VALIDATED_RANGE  mPreValidatedRange[] = {
  26   // The below address range was part of the SEV OVMF metadata, and range
  27   // should be pre-validated by the Hypervisor.
  28   {
  29     FixedPcdGet32 (PcdOvmfSecPageTablesBase),
  30     FixedPcdGet32 (PcdOvmfPeiMemFvBase),
  31   },
  32   // The below range is pre-validated by the Sec/SecMain.c
  33   {
  34     FixedPcdGet32 (PcdOvmfSecValidatedStart),
  35     FixedPcdGet32 (PcdOvmfSecValidatedEnd)
  36   },
  37 };
  38
  39 STATIC
  40 BOOLEAN
  41 DetectPreValidatedOverLap (
  42   IN    PHYSICAL_ADDRESS         StartAddress,
  43   IN    PHYSICAL_ADDRESS         EndAddress,
  44   OUT   SNP_PRE_VALIDATED_RANGE  *OverlapRange
  45   )
  46 {
  47   UINTN  i;
  48
  49   //
  50   // Check if the specified address range exist in pre-validated array.
  51   //
  52   for (i = 0; i < ARRAY_SIZE (mPreValidatedRange); i++) {
  53     if ((mPreValidatedRange[i].StartAddress < EndAddress) &&
  54         (StartAddress < mPreValidatedRange[i].EndAddress))
  55     {
  56       OverlapRange->StartAddress = mPreValidatedRange[i].StartAddress;
  57       OverlapRange->EndAddress   = mPreValidatedRange[i].EndAddress;
  58       return TRUE;
  59     }
  60   }
  61
  62   return FALSE;
  63 }
  64
  65 /**
  66   Pre-validate the system RAM when SEV-SNP is enabled in the guest VM.
  67
  68   @param[in]  BaseAddress             Base address
  69   @param[in]  NumPages                Number of pages starting from the base address
  70
  71 **/
  72 VOID
  73 EFIAPI
  74 MemEncryptSevSnpPreValidateSystemRam (
  75   IN PHYSICAL_ADDRESS  BaseAddress,
  76   IN UINTN             NumPages
  77   )
  78 {
  79   PHYSICAL_ADDRESS         EndAddress;
  80   SNP_PRE_VALIDATED_RANGE  OverlapRange;
  81   EFI_STATUS               Status;
  82
  83   if (!MemEncryptSevSnpIsEnabled ()) {
  84     return;
  85   }
  86
  87   EndAddress = BaseAddress + EFI_PAGES_TO_SIZE (NumPages);
  88
  89   //
  90   // The page table used in PEI can address up to 4GB memory. If we are asked to
  91   // validate a range above the 4GB, then create an identity mapping so that the
  92   // PVALIDATE instruction can execute correctly. If the page table entry is not
  93   // present then PVALIDATE will #GP.
  94   //
  95   if (BaseAddress >= SIZE_4GB) {
  96     Status = InternalMemEncryptSevCreateIdentityMap1G (
  97                0,
  98                BaseAddress,
  99                EFI_PAGES_TO_SIZE (NumPages)
 100                );
 101     if (EFI_ERROR (Status)) {
 102       ASSERT (FALSE);
 103       CpuDeadLoop ();
 104     }
 105   }
 106
 107   while (BaseAddress < EndAddress) {
 108     //
 109     // Check if the range overlaps with the pre-validated ranges.
 110     //
 111     if (DetectPreValidatedOverLap (BaseAddress, EndAddress, &OverlapRange)) {
 112       // Validate the non-overlap regions.
 113       if (BaseAddress < OverlapRange.StartAddress) {
 114         NumPages = EFI_SIZE_TO_PAGES (OverlapRange.StartAddress - BaseAddress);
 115
 116         InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE);
 117       }
 118
 119       BaseAddress = OverlapRange.EndAddress;
 120       continue;
 121     }
 122
 123     // Validate the remaining pages.
 124     NumPages = EFI_SIZE_TO_PAGES (EndAddress - BaseAddress);
 125     InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE);
 126     BaseAddress = EndAddress;
 127   }
 128 }