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