OvmfPkg/Library/BaseMemEncryptSevLib/DxeMemEncryptSevLibInternal.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/Amd/Cpuid.h>
  16 #include <Register/Amd/Msr.h>
  17 #include <Register/Cpuid.h>
  18 #include <Uefi/UefiBaseType.h>
  19
  20 STATIC BOOLEAN  mSevStatus        = FALSE;
  21 STATIC BOOLEAN  mSevEsStatus      = FALSE;
  22 STATIC BOOLEAN  mSevSnpStatus     = FALSE;
  23 STATIC BOOLEAN  mSevStatusChecked = FALSE;
  24
  25 STATIC UINT64   mSevEncryptionMask      = 0;
  26 STATIC BOOLEAN  mSevEncryptionMaskSaved = FALSE;
  27
  28 /**
  29   Reads and sets the status of SEV features.
  30
  31   **/
  32 STATIC
  33 VOID
  34 EFIAPI
  35 InternalMemEncryptSevStatus (
  36   VOID
  37   )
  38 {
  39   UINT32                            RegEax;
  40   MSR_SEV_STATUS_REGISTER           Msr;
  41   CPUID_MEMORY_ENCRYPTION_INFO_EAX  Eax;
  42   BOOLEAN                           ReadSevMsr;
  43   UINT64                            EncryptionMask;
  44
  45   ReadSevMsr = FALSE;
  46
  47   EncryptionMask = PcdGet64 (PcdPteMemoryEncryptionAddressOrMask);
  48   if (EncryptionMask != 0) {
  49     //
  50     // The MSR has been read before, so it is safe to read it again and avoid
  51     // having to validate the CPUID information.
  52     //
  53     ReadSevMsr = TRUE;
  54   } else {
  55     //
  56     // Check if memory encryption leaf exist
  57     //
  58     AsmCpuid (CPUID_EXTENDED_FUNCTION, &RegEax, NULL, NULL, NULL);
  59     if (RegEax >= CPUID_MEMORY_ENCRYPTION_INFO) {
  60       //
  61       // CPUID Fn8000_001F[EAX] Bit 1 (Sev supported)
  62       //
  63       AsmCpuid (CPUID_MEMORY_ENCRYPTION_INFO, &Eax.Uint32, NULL, NULL, NULL);
  64
  65       if (Eax.Bits.SevBit) {
  66         ReadSevMsr = TRUE;
  67       }
  68     }
  69   }
  70
  71   if (ReadSevMsr) {
  72     //
  73     // Check MSR_0xC0010131 Bit 0 (Sev Enabled)
  74     //
  75     Msr.Uint32 = AsmReadMsr32 (MSR_SEV_STATUS);
  76     if (Msr.Bits.SevBit) {
  77       mSevStatus = TRUE;
  78     }
  79
  80     //
  81     // Check MSR_0xC0010131 Bit 1 (Sev-Es Enabled)
  82     //
  83     if (Msr.Bits.SevEsBit) {
  84       mSevEsStatus = TRUE;
  85     }
  86
  87     //
  88     // Check MSR_0xC0010131 Bit 2 (Sev-Snp Enabled)
  89     //
  90     if (Msr.Bits.SevSnpBit) {
  91       mSevSnpStatus = TRUE;
  92     }
  93   }
  94
  95   mSevStatusChecked = TRUE;
  96 }
  97
  98 /**
  99   Returns a boolean to indicate whether SEV-SNP is enabled.
 100
 101   @retval TRUE           SEV-SNP is enabled
 102   @retval FALSE          SEV-SNP is not enabled
 103 **/
 104 BOOLEAN
 105 EFIAPI
 106 MemEncryptSevSnpIsEnabled (
 107   VOID
 108   )
 109 {
 110   if (!mSevStatusChecked) {
 111     InternalMemEncryptSevStatus ();
 112   }
 113
 114   return mSevSnpStatus;
 115 }
 116
 117 /**
 118   Returns a boolean to indicate whether SEV-ES is enabled.
 119
 120   @retval TRUE           SEV-ES is enabled
 121   @retval FALSE          SEV-ES is not enabled
 122 **/
 123 BOOLEAN
 124 EFIAPI
 125 MemEncryptSevEsIsEnabled (
 126   VOID
 127   )
 128 {
 129   if (!mSevStatusChecked) {
 130     InternalMemEncryptSevStatus ();
 131   }
 132
 133   return mSevEsStatus;
 134 }
 135
 136 /**
 137   Returns a boolean to indicate whether SEV is enabled.
 138
 139   @retval TRUE           SEV is enabled
 140   @retval FALSE          SEV is not enabled
 141 **/
 142 BOOLEAN
 143 EFIAPI
 144 MemEncryptSevIsEnabled (
 145   VOID
 146   )
 147 {
 148   if (!mSevStatusChecked) {
 149     InternalMemEncryptSevStatus ();
 150   }
 151
 152   return mSevStatus;
 153 }
 154
 155 /**
 156   Returns the SEV encryption mask.
 157
 158   @return  The SEV pagtable encryption mask
 159 **/
 160 UINT64
 161 EFIAPI
 162 MemEncryptSevGetEncryptionMask (
 163   VOID
 164   )
 165 {
 166   if (!mSevEncryptionMaskSaved) {
 167     mSevEncryptionMask      = PcdGet64 (PcdPteMemoryEncryptionAddressOrMask);
 168     mSevEncryptionMaskSaved = TRUE;
 169   }
 170
 171   return mSevEncryptionMask;
 172 }