UefiCpuPkg/Library/MpInitLib/AmdSev.c

   1 /** @file
   2   CPU MP Initialize helper function for AMD SEV.
   3
   4   Copyright (c) 2021, AMD Inc. All rights reserved.<BR>
   5
   6   SPDX-License-Identifier: BSD-2-Clause-Patent
   7
   8 **/
   9
  10 #include "MpLib.h"
  11 #include <Library/VmgExitLib.h>
  12
  13 /**
  14   Get Protected mode code segment with 16-bit default addressing
  15   from current GDT table.
  16
  17   @return  Protected mode 16-bit code segment value.
  18 **/
  19 STATIC
  20 UINT16
  21 GetProtectedMode16CS (
  22   VOID
  23   )
  24 {
  25   IA32_DESCRIPTOR          GdtrDesc;
  26   IA32_SEGMENT_DESCRIPTOR  *GdtEntry;
  27   UINTN                    GdtEntryCount;
  28   UINT16                   Index;
  29
  30   Index = (UINT16)-1;
  31   AsmReadGdtr (&GdtrDesc);
  32   GdtEntryCount = (GdtrDesc.Limit + 1) / sizeof (IA32_SEGMENT_DESCRIPTOR);
  33   GdtEntry      = (IA32_SEGMENT_DESCRIPTOR *)GdtrDesc.Base;
  34   for (Index = 0; Index < GdtEntryCount; Index++) {
  35     if ((GdtEntry->Bits.L == 0) &&
  36         (GdtEntry->Bits.DB == 0) &&
  37         (GdtEntry->Bits.Type > 8))
  38     {
  39       break;
  40     }
  41
  42     GdtEntry++;
  43   }
  44
  45   ASSERT (Index != GdtEntryCount);
  46   return Index * 8;
  47 }
  48
  49 /**
  50   Get Protected mode code segment with 32-bit default addressing
  51   from current GDT table.
  52
  53   @return  Protected mode 32-bit code segment value.
  54 **/
  55 STATIC
  56 UINT16
  57 GetProtectedMode32CS (
  58   VOID
  59   )
  60 {
  61   IA32_DESCRIPTOR          GdtrDesc;
  62   IA32_SEGMENT_DESCRIPTOR  *GdtEntry;
  63   UINTN                    GdtEntryCount;
  64   UINT16                   Index;
  65
  66   Index = (UINT16)-1;
  67   AsmReadGdtr (&GdtrDesc);
  68   GdtEntryCount = (GdtrDesc.Limit + 1) / sizeof (IA32_SEGMENT_DESCRIPTOR);
  69   GdtEntry      = (IA32_SEGMENT_DESCRIPTOR *)GdtrDesc.Base;
  70   for (Index = 0; Index < GdtEntryCount; Index++) {
  71     if ((GdtEntry->Bits.L == 0) &&
  72         (GdtEntry->Bits.DB == 1) &&
  73         (GdtEntry->Bits.Type > 8))
  74     {
  75       break;
  76     }
  77
  78     GdtEntry++;
  79   }
  80
  81   ASSERT (Index != GdtEntryCount);
  82   return Index * 8;
  83 }
  84
  85 /**
  86   Reset an AP when in SEV-ES mode.
  87
  88   If successful, this function never returns.
  89
  90   @param[in] Ghcb                 Pointer to the GHCB
  91   @param[in] CpuMpData            Pointer to CPU MP Data
  92
  93 **/
  94 VOID
  95 MpInitLibSevEsAPReset (
  96   IN GHCB         *Ghcb,
  97   IN CPU_MP_DATA  *CpuMpData
  98   )
  99 {
 100   EFI_STATUS  Status;
 101   UINTN       ProcessorNumber;
 102   UINT16      Code16, Code32;
 103   AP_RESET    *APResetFn;
 104   UINTN       BufferStart;
 105   UINTN       StackStart;
 106
 107   Status = GetProcessorNumber (CpuMpData, &ProcessorNumber);
 108   ASSERT_EFI_ERROR (Status);
 109
 110   Code16 = GetProtectedMode16CS ();
 111   Code32 = GetProtectedMode32CS ();
 112
 113   if (CpuMpData->WakeupBufferHigh != 0) {
 114     APResetFn = (AP_RESET *)(CpuMpData->WakeupBufferHigh + CpuMpData->AddressMap.SwitchToRealNoNxOffset);
 115   } else {
 116     APResetFn = (AP_RESET *)(CpuMpData->MpCpuExchangeInfo->BufferStart + CpuMpData->AddressMap.SwitchToRealOffset);
 117   }
 118
 119   BufferStart = CpuMpData->MpCpuExchangeInfo->BufferStart;
 120   StackStart  = CpuMpData->SevEsAPResetStackStart -
 121                 (AP_RESET_STACK_SIZE * ProcessorNumber);
 122
 123   //
 124   // This call never returns.
 125   //
 126   APResetFn (BufferStart, Code16, Code32, StackStart);
 127 }
 128
 129 /**
 130   Allocate the SEV-ES AP jump table buffer.
 131
 132   @param[in, out]  CpuMpData  The pointer to CPU MP Data structure.
 133 **/
 134 VOID
 135 AllocateSevEsAPMemory (
 136   IN OUT CPU_MP_DATA  *CpuMpData
 137   )
 138 {
 139   if (CpuMpData->SevEsAPBuffer == (UINTN)-1) {
 140     CpuMpData->SevEsAPBuffer =
 141       CpuMpData->SevEsIsEnabled ? GetSevEsAPMemory () : 0;
 142   }
 143 }
 144
 145 /**
 146   Program the SEV-ES AP jump table buffer.
 147
 148   @param[in]  SipiVector  The SIPI vector used for the AP Reset
 149 **/
 150 VOID
 151 SetSevEsJumpTable (
 152   IN UINTN  SipiVector
 153   )
 154 {
 155   SEV_ES_AP_JMP_FAR  *JmpFar;
 156   UINT32             Offset, InsnByte;
 157   UINT8              LoNib, HiNib;
 158
 159   JmpFar = (SEV_ES_AP_JMP_FAR *)(UINTN)FixedPcdGet32 (PcdSevEsWorkAreaBase);
 160   ASSERT (JmpFar != NULL);
 161
 162   //
 163   // Obtain the address of the Segment/Rip location in the workarea.
 164   // This will be set to a value derived from the SIPI vector and will
 165   // be the memory address used for the far jump below.
 166   //
 167   Offset  = FixedPcdGet32 (PcdSevEsWorkAreaBase);
 168   Offset += sizeof (JmpFar->InsnBuffer);
 169   LoNib   = (UINT8)Offset;
 170   HiNib   = (UINT8)(Offset >> 8);
 171
 172   //
 173   // Program the workarea (which is the initial AP boot address) with
 174   // far jump to the SIPI vector (where XX and YY represent the
 175   // address of where the SIPI vector is stored.
 176   //
 177   //   JMP FAR [CS:XXYY] => 2E FF 2E YY XX
 178   //
 179   InsnByte                       = 0;
 180   JmpFar->InsnBuffer[InsnByte++] = 0x2E;  // CS override prefix
 181   JmpFar->InsnBuffer[InsnByte++] = 0xFF;  // JMP (FAR)
 182   JmpFar->InsnBuffer[InsnByte++] = 0x2E;  // ModRM (JMP memory location)
 183   JmpFar->InsnBuffer[InsnByte++] = LoNib; // YY offset ...
 184   JmpFar->InsnBuffer[InsnByte++] = HiNib; // XX offset ...
 185
 186   //
 187   // Program the Segment/Rip based on the SIPI vector (always at least
 188   // 16-byte aligned, so Rip is set to 0).
 189   //
 190   JmpFar->Rip     = 0;
 191   JmpFar->Segment = (UINT16)(SipiVector >> 4);
 192 }
 193
 194 /**
 195   The function puts the AP in halt loop.
 196
 197   @param[in]  CpuMpData  The pointer to CPU MP Data structure.
 198 **/
 199 VOID
 200 SevEsPlaceApHlt (
 201   CPU_MP_DATA  *CpuMpData
 202   )
 203 {
 204   MSR_SEV_ES_GHCB_REGISTER  Msr;
 205   GHCB                      *Ghcb;
 206   UINT64                    Status;
 207   BOOLEAN                   DoDecrement;
 208   BOOLEAN                   InterruptState;
 209
 210   DoDecrement = (BOOLEAN)(CpuMpData->InitFlag == ApInitConfig);
 211
 212   while (TRUE) {
 213     Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
 214     Ghcb                    = Msr.Ghcb;
 215
 216     VmgInit (Ghcb, &InterruptState);
 217
 218     if (DoDecrement) {
 219       DoDecrement = FALSE;
 220
 221       //
 222       // Perform the delayed decrement just before issuing the first
 223       // VMGEXIT with AP_RESET_HOLD.
 224       //
 225       InterlockedDecrement ((UINT32 *)&CpuMpData->MpCpuExchangeInfo->NumApsExecuting);
 226     }
 227
 228     Status = VmgExit (Ghcb, SVM_EXIT_AP_RESET_HOLD, 0, 0);
 229     if ((Status == 0) && (Ghcb->SaveArea.SwExitInfo2 != 0)) {
 230       VmgDone (Ghcb, InterruptState);
 231       break;
 232     }
 233
 234     VmgDone (Ghcb, InterruptState);
 235   }
 236
 237   //
 238   // Awakened in a new phase? Use the new CpuMpData
 239   //
 240   if (CpuMpData->NewCpuMpData != NULL) {
 241     CpuMpData = CpuMpData->NewCpuMpData;
 242   }
 243
 244   MpInitLibSevEsAPReset (Ghcb, CpuMpData);
 245 }