OvmfPkg/Library/BaseMemEncryptSevLib/SecMemEncryptSevLibInternal.c

   1 /** @file
   2
   3   Secure Encrypted Virtualization (SEV) library helper function
   4
   5   Copyright (c) 2020, Advanced Micro Devices, Inc. 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/Amd/Cpuid.h>
  16 #include <Register/Amd/Msr.h>
  17 #include <Register/Cpuid.h>
  18 #include <Uefi/UefiBaseType.h>
  19
  20 /**
  21   Reads and sets the status of SEV features.
  22
  23   **/
  24 STATIC
  25 UINT32
  26 EFIAPI
  27 InternalMemEncryptSevStatus (
  28   VOID
  29   )
  30 {
  31   UINT32                            RegEax;
  32   CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
  33   BOOLEAN                           ReadSevMsr;
  34   SEC_SEV_ES_WORK_AREA              *SevEsWorkArea;
  35
  36   ReadSevMsr = FALSE;
  37
  38   SevEsWorkArea = (SEC_SEV_ES_WORK_AREA *)FixedPcdGet32 (PcdSevEsWorkAreaBase);
  39   if ((SevEsWorkArea != NULL) && (SevEsWorkArea->EncryptionMask != 0)) {
  40     //
  41     // The MSR has been read before, so it is safe to read it again and avoid
  42     // having to validate the CPUID information.
  43     //
  44     ReadSevMsr = TRUE;
  45   } else {
  46     //
  47     // Check if memory encryption leaf exist
  48     //
  49     AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
  50     if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
  51       //
  52       // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
  53       //
  54       AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL);
  55
  56       if (Eax.Bits.SevBit) {
  57         ReadSevMsr = TRUE;
  58       }
  59     }
  60   }
  61
  62   return ReadSevMsr ? AsmReadMsr32 (MSR_SEV_STATUS) : 0;
  63 }
  64
  65 /**
  66   Returns a boolean to indicate whether SEV-ES is enabled.
  67
  68   @retval TRUE           SEV-ES is enabled
  69   @retval FALSE          SEV-ES is not enabled
  70 **/
  71 BOOLEAN
  72 EFIAPI
  73 MemEncryptSevEsIsEnabled (
  74   VOID
  75   )
  76 {
  77   MSR_SEV_STATUS_REGISTER  Msr;
  78
  79   Msr.Uint32 = InternalMemEncryptSevStatus ();
  80
  81   return Msr.Bits.SevEsBit ? TRUE : FALSE;
  82 }
  83
  84 /**
  85   Returns a boolean to indicate whether SEV is enabled.
  86
  87   @retval TRUE           SEV is enabled
  88   @retval FALSE          SEV is not enabled
  89 **/
  90 BOOLEAN
  91 EFIAPI
  92 MemEncryptSevIsEnabled (
  93   VOID
  94   )
  95 {
  96   MSR_SEV_STATUS_REGISTER  Msr;
  97
  98   Msr.Uint32 = InternalMemEncryptSevStatus ();
  99
 100   return Msr.Bits.SevBit ? TRUE : FALSE;
 101 }
 102
 103 /**
 104   Returns the SEV encryption mask.
 105
 106   @return  The SEV pagtable encryption mask
 107 **/
 108 UINT64
 109 EFIAPI
 110 MemEncryptSevGetEncryptionMask (
 111   VOID
 112   )
 113 {
 114   CPUID_MEMORY_ENCRYPTION_INFO_EBX  Ebx;
 115   SEC_SEV_ES_WORK_AREA              *SevEsWorkArea;
 116   UINT64                            EncryptionMask;
 117
 118   SevEsWorkArea = (SEC_SEV_ES_WORK_AREA *)FixedPcdGet32 (PcdSevEsWorkAreaBase);
 119   if (SevEsWorkArea != NULL) {
 120     EncryptionMask = SevEsWorkArea->EncryptionMask;
 121   } else {
 122     //
 123     // CPUID Fn8000_001F[EBX] Bit 0:5 (memory encryption bit position)
 124     //
 125     AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, NULL, &Ebx.Uint32, NULL, NULL);
 126     EncryptionMask = LShiftU64 (1, Ebx.Bits.PtePosBits);
 127   }
 128
 129   return EncryptionMask;
 130 }
 131
 132 /**
 133   Locate the page range that covers the initial (pre-SMBASE-relocation) SMRAM
 134   Save State Map.
 135
 136   @param[out] BaseAddress     The base address of the lowest-address page that
 137                               covers the initial SMRAM Save State Map.
 138
 139   @param[out] NumberOfPages   The number of pages in the page range that covers
 140                               the initial SMRAM Save State Map.
 141
 142   @retval RETURN_SUCCESS      BaseAddress and NumberOfPages have been set on
 143                               output.
 144
 145   @retval RETURN_UNSUPPORTED  SMM is unavailable.
 146 **/
 147 RETURN_STATUS
 148 EFIAPI
 149 MemEncryptSevLocateInitialSmramSaveStateMapPages (
 150   OUT UINTN  *BaseAddress,
 151   OUT UINTN  *NumberOfPages
 152   )
 153 {
 154   return RETURN_UNSUPPORTED;
 155 }