OvmfPkg/Library/VmgExitLib/VmTdExitVeHandler.c

   1 /** @file
   2
   3   Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>
   4
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include <Library/BaseLib.h>
  10 #include <Library/DebugLib.h>
  11 #include "VmTdExitHandler.h"
  12 #include <Library/VmgExitLib.h>
  13 #include <Library/BaseMemoryLib.h>
  14 #include <IndustryStandard/Tdx.h>
  15 #include <IndustryStandard/InstructionParsing.h>
  16
  17 typedef union {
  18   struct {
  19     UINT32    Eax;
  20     UINT32    Edx;
  21   } Regs;
  22   UINT64    Val;
  23 } MSR_DATA;
  24
  25 typedef union {
  26   UINT8    Val;
  27   struct {
  28     UINT8    B : 1;
  29     UINT8    X : 1;
  30     UINT8    R : 1;
  31     UINT8    W : 1;
  32   } Bits;
  33 } REX;
  34
  35 typedef union {
  36   UINT8    Val;
  37   struct {
  38     UINT8    Rm  : 3;
  39     UINT8    Reg : 3;
  40     UINT8    Mod : 2;
  41   } Bits;
  42 } MODRM;
  43
  44 typedef struct {
  45   UINT64    Regs[4];
  46 } CPUID_DATA;
  47
  48 /**
  49   Handle an CPUID event.
  50
  51   Use the TDVMCALL instruction to handle cpuid #ve
  52
  53   @param[in, out] Regs             x64 processor context
  54   @param[in]      Veinfo           VE Info
  55
  56   @retval 0                        Event handled successfully
  57   @return                          New exception value to propagate
  58 **/
  59 STATIC
  60 UINT64
  61 EFIAPI
  62 CpuIdExit (
  63   IN EFI_SYSTEM_CONTEXT_X64     *Regs,
  64   IN TDCALL_VEINFO_RETURN_DATA  *Veinfo
  65   )
  66 {
  67   CPUID_DATA  CpuIdData;
  68   UINT64      Status;
  69
  70   Status = TdVmCallCpuid (Regs->Rax, Regs->Rcx, &CpuIdData);
  71
  72   if (Status == 0) {
  73     Regs->Rax = CpuIdData.Regs[0];
  74     Regs->Rbx = CpuIdData.Regs[1];
  75     Regs->Rcx = CpuIdData.Regs[2];
  76     Regs->Rdx = CpuIdData.Regs[3];
  77   }
  78
  79   return Status;
  80 }
  81
  82 /**
  83   Handle an IO event.
  84
  85   Use the TDVMCALL instruction to handle either an IO read or an IO write.
  86
  87   @param[in, out] Regs             x64 processor context
  88   @param[in]      Veinfo           VE Info
  89
  90   @retval 0                        Event handled successfully
  91   @return                          New exception value to propagate
  92 **/
  93 STATIC
  94 UINT64
  95 EFIAPI
  96 IoExit (
  97   IN OUT EFI_SYSTEM_CONTEXT_X64  *Regs,
  98   IN TDCALL_VEINFO_RETURN_DATA   *Veinfo
  99   )
 100 {
 101   BOOLEAN  Write;
 102   UINTN    Size;
 103   UINTN    Port;
 104   UINT64   Val;
 105   UINT64   RepCnt;
 106   UINT64   Status;
 107
 108   Val   = 0;
 109   Write = Veinfo->ExitQualification.Io.Direction ? FALSE : TRUE;
 110   Size  = Veinfo->ExitQualification.Io.Size + 1;
 111   Port  = Veinfo->ExitQualification.Io.Port;
 112
 113   if (Veinfo->ExitQualification.Io.String) {
 114     //
 115     // If REP is set, get rep-cnt from Rcx
 116     //
 117     RepCnt = Veinfo->ExitQualification.Io.Rep ? Regs->Rcx : 1;
 118
 119     while (RepCnt) {
 120       Val = 0;
 121       if (Write == TRUE) {
 122         CopyMem (&Val, (VOID *)Regs->Rsi, Size);
 123         Regs->Rsi += Size;
 124       }
 125
 126       Status = TdVmCall (EXIT_REASON_IO_INSTRUCTION, Size, Write, Port, Val, (Write ? NULL : &Val));
 127       if (Status != 0) {
 128         break;
 129       }
 130
 131       if (Write == FALSE) {
 132         CopyMem ((VOID *)Regs->Rdi, &Val, Size);
 133         Regs->Rdi += Size;
 134       }
 135
 136       if (Veinfo->ExitQualification.Io.Rep) {
 137         Regs->Rcx -= 1;
 138       }
 139
 140       RepCnt -= 1;
 141     }
 142   } else {
 143     if (Write == TRUE) {
 144       CopyMem (&Val, (VOID *)&Regs->Rax, Size);
 145     }
 146
 147     Status = TdVmCall (EXIT_REASON_IO_INSTRUCTION, Size, Write, Port, Val, (Write ? NULL : &Val));
 148     if ((Status == 0) && (Write == FALSE)) {
 149       CopyMem ((VOID *)&Regs->Rax, &Val, Size);
 150     }
 151   }
 152
 153   return Status;
 154 }
 155
 156 /**
 157   Handle an READ MSR event.
 158
 159   Use the TDVMCALL instruction to handle msr read
 160
 161   @param[in, out] Regs             x64 processor context
 162   @param[in]      Veinfo           VE Info
 163
 164   @retval 0                        Event handled successfully
 165   @return                          New exception value to propagate
 166 **/
 167 STATIC
 168 UINT64
 169 ReadMsrExit (
 170   IN OUT EFI_SYSTEM_CONTEXT_X64  *Regs,
 171   IN TDCALL_VEINFO_RETURN_DATA   *Veinfo
 172   )
 173 {
 174   MSR_DATA  Data;
 175   UINT64    Status;
 176
 177   Status = TdVmCall (EXIT_REASON_MSR_READ, Regs->Rcx, 0, 0, 0, &Data);
 178   if (Status == 0) {
 179     Regs->Rax = Data.Regs.Eax;
 180     Regs->Rdx = Data.Regs.Edx;
 181   }
 182
 183   return Status;
 184 }
 185
 186 /**
 187   Handle an WRITE MSR event.
 188
 189   Use the TDVMCALL instruction to handle msr write
 190
 191   @param[in, out] Regs             x64 processor context
 192   @param[in]      Veinfo           VE Info
 193
 194   @retval 0                        Event handled successfully
 195   @return                          New exception value to propagate
 196 **/
 197 STATIC
 198 UINT64
 199 WriteMsrExit (
 200   IN OUT EFI_SYSTEM_CONTEXT_X64  *Regs,
 201   IN TDCALL_VEINFO_RETURN_DATA   *Veinfo
 202   )
 203 {
 204   UINT64    Status;
 205   MSR_DATA  Data;
 206
 207   Data.Regs.Eax = (UINT32)Regs->Rax;
 208   Data.Regs.Edx = (UINT32)Regs->Rdx;
 209
 210   Status =  TdVmCall (EXIT_REASON_MSR_WRITE, Regs->Rcx, Data.Val, 0, 0, NULL);
 211
 212   return Status;
 213 }
 214
 215 STATIC
 216 VOID
 217 EFIAPI
 218 TdxDecodeInstruction (
 219   IN UINT8  *Rip
 220   )
 221 {
 222   UINTN  i;
 223
 224   DEBUG ((DEBUG_INFO, "TDX: #TD[EPT] instruction (%p):", Rip));
 225   for (i = 0; i < 15; i++) {
 226     DEBUG ((DEBUG_INFO, "%02x:", Rip[i]));
 227   }
 228
 229   DEBUG ((DEBUG_INFO, "\n"));
 230 }
 231
 232 #define TDX_DECODER_BUG_ON(x)               \
 233   if ((x)) {                                \
 234     TdxDecodeInstruction(Rip);              \
 235     TdVmCall(TDVMCALL_HALT, 0, 0, 0, 0, 0); \
 236   }
 237
 238 STATIC
 239 UINT64 *
 240 EFIAPI
 241 GetRegFromContext (
 242   IN EFI_SYSTEM_CONTEXT_X64  *Regs,
 243   IN UINTN                   RegIndex
 244   )
 245 {
 246   switch (RegIndex) {
 247     case 0: return &Regs->Rax;
 248       break;
 249     case 1: return &Regs->Rcx;
 250       break;
 251     case 2: return &Regs->Rdx;
 252       break;
 253     case 3: return &Regs->Rbx;
 254       break;
 255     case 4: return &Regs->Rsp;
 256       break;
 257     case 5: return &Regs->Rbp;
 258       break;
 259     case 6: return &Regs->Rsi;
 260       break;
 261     case 7: return &Regs->Rdi;
 262       break;
 263     case 8: return &Regs->R8;
 264       break;
 265     case 9: return &Regs->R9;
 266       break;
 267     case 10: return &Regs->R10;
 268       break;
 269     case 11: return &Regs->R11;
 270       break;
 271     case 12: return &Regs->R12;
 272       break;
 273     case 13: return &Regs->R13;
 274       break;
 275     case 14: return &Regs->R14;
 276       break;
 277     case 15: return &Regs->R15;
 278       break;
 279   }
 280
 281   return NULL;
 282 }
 283
 284 /**
 285   Handle an MMIO event.
 286
 287   Use the TDVMCALL instruction to handle either an mmio read or an mmio write.
 288
 289   @param[in, out] Regs             x64 processor context
 290   @param[in]      Veinfo           VE Info
 291
 292   @retval 0                        Event handled successfully
 293   @return                          New exception value to propagate
 294 **/
 295 STATIC
 296 INTN
 297 EFIAPI
 298 MmioExit (
 299   IN OUT EFI_SYSTEM_CONTEXT_X64  *Regs,
 300   IN TDCALL_VEINFO_RETURN_DATA   *Veinfo
 301   )
 302 {
 303   UINT64          Status;
 304   UINT32          MmioSize;
 305   UINT32          RegSize;
 306   UINT8           OpCode;
 307   BOOLEAN         SeenRex;
 308   UINT64          *Reg;
 309   UINT8           *Rip;
 310   UINT64          Val;
 311   UINT32          OpSize;
 312   MODRM           ModRm;
 313   REX             Rex;
 314   TD_RETURN_DATA  TdReturnData;
 315   UINT8           Gpaw;
 316   UINT64          TdSharedPageMask;
 317
 318   Rip     = (UINT8 *)Regs->Rip;
 319   Val     = 0;
 320   Rex.Val = 0;
 321   SeenRex = FALSE;
 322
 323   Status = TdCall (TDCALL_TDINFO, 0, 0, 0, &TdReturnData);
 324   if (Status == TDX_EXIT_REASON_SUCCESS) {
 325     Gpaw             = (UINT8)(TdReturnData.TdInfo.Gpaw & 0x3f);
 326     TdSharedPageMask = 1ULL << (Gpaw - 1);
 327   } else {
 328     DEBUG ((DEBUG_ERROR, "TDCALL failed with status=%llx\n", Status));
 329     return Status;
 330   }
 331
 332   if ((Veinfo->GuestPA & TdSharedPageMask) == 0) {
 333     DEBUG ((DEBUG_ERROR, "EPT-violation #VE on private memory is not allowed!"));
 334     TdVmCall (TDVMCALL_HALT, 0, 0, 0, 0, 0);
 335     CpuDeadLoop ();
 336   }
 337
 338   //
 339   // Default to 32bit transfer
 340   //
 341   OpSize = 4;
 342
 343   do {
 344     OpCode = *Rip++;
 345     if (OpCode == 0x66) {
 346       OpSize = 2;
 347     } else if ((OpCode == 0x64) || (OpCode == 0x65) || (OpCode == 0x67)) {
 348       continue;
 349     } else if ((OpCode >= 0x40) && (OpCode <= 0x4f)) {
 350       SeenRex = TRUE;
 351       Rex.Val = OpCode;
 352     } else {
 353       break;
 354     }
 355   } while (TRUE);
 356
 357   //
 358   // We need to have at least 2 more bytes for this instruction
 359   //
 360   TDX_DECODER_BUG_ON (((UINT64)Rip - Regs->Rip) > 13);
 361
 362   OpCode = *Rip++;
 363   //
 364   // Two-byte opecode, get next byte
 365   //
 366   if (OpCode == 0x0F) {
 367     OpCode = *Rip++;
 368   }
 369
 370   switch (OpCode) {
 371     case 0x88:
 372     case 0x8A:
 373     case 0xB6:
 374       MmioSize = 1;
 375       break;
 376     case 0xB7:
 377       MmioSize = 2;
 378       break;
 379     default:
 380       MmioSize = Rex.Bits.W ? 8 : OpSize;
 381       break;
 382   }
 383
 384   /* Punt on AH/BH/CH/DH unless it shows up. */
 385   ModRm.Val = *Rip++;
 386   TDX_DECODER_BUG_ON (MmioSize == 1 && ModRm.Bits.Reg > 4 && !SeenRex && OpCode != 0xB6);
 387   Reg = GetRegFromContext (Regs, ModRm.Bits.Reg | ((int)Rex.Bits.R << 3));
 388   TDX_DECODER_BUG_ON (!Reg);
 389
 390   if (ModRm.Bits.Rm == 4) {
 391     ++Rip; /* SIB byte */
 392   }
 393
 394   if ((ModRm.Bits.Mod == 2) || ((ModRm.Bits.Mod == 0) && (ModRm.Bits.Rm == 5))) {
 395     Rip += 4; /* DISP32 */
 396   } else if (ModRm.Bits.Mod == 1) {
 397     ++Rip;  /* DISP8 */
 398   }
 399
 400   switch (OpCode) {
 401     case 0x88:
 402     case 0x89:
 403       CopyMem ((void *)&Val, Reg, MmioSize);
 404       Status = TdVmCall (TDVMCALL_MMIO, MmioSize, 1, Veinfo->GuestPA, Val, 0);
 405       break;
 406     case 0xC7:
 407       CopyMem ((void *)&Val, Rip, OpSize);
 408       Status = TdVmCall (TDVMCALL_MMIO, MmioSize, 1, Veinfo->GuestPA, Val, 0);
 409       Rip   += OpSize;
 410     default:
 411       //
 412       // 32-bit write registers are zero extended to the full register
 413       // Hence 'MOVZX r[32/64], r/m16' is
 414       // hardcoded to reg size 8, and the straight MOV case has a reg
 415       // size of 8 in the 32-bit read case.
 416       //
 417       switch (OpCode) {
 418         case 0xB6:
 419           RegSize = Rex.Bits.W ? 8 : OpSize;
 420           break;
 421         case 0xB7:
 422           RegSize =  8;
 423           break;
 424         default:
 425           RegSize = MmioSize == 4 ? 8 : MmioSize;
 426           break;
 427       }
 428
 429       Status = TdVmCall (TDVMCALL_MMIO, MmioSize, 0, Veinfo->GuestPA, 0, &Val);
 430       if (Status == 0) {
 431         ZeroMem (Reg, RegSize);
 432         CopyMem (Reg, (void *)&Val, MmioSize);
 433       }
 434   }
 435
 436   if (Status == 0) {
 437     TDX_DECODER_BUG_ON (((UINT64)Rip - Regs->Rip) > 15);
 438
 439     //
 440     // We change instruction length to reflect true size so handler can
 441     // bump rip
 442     //
 443     Veinfo->ExitInstructionLength =  (UINT32)((UINT64)Rip - Regs->Rip);
 444   }
 445
 446   return Status;
 447 }
 448
 449 /**
 450   Handle a #VE exception.
 451
 452   Performs the necessary processing to handle a #VE exception.
 453
 454   @param[in, out]  ExceptionType  Pointer to an EFI_EXCEPTION_TYPE to be set
 455                                   as value to use on error.
 456   @param[in, out]  SystemContext  Pointer to EFI_SYSTEM_CONTEXT
 457
 458   @retval  EFI_SUCCESS            Exception handled
 459   @retval  EFI_UNSUPPORTED        #VE not supported, (new) exception value to
 460                                   propagate provided
 461   @retval  EFI_PROTOCOL_ERROR     #VE handling failed, (new) exception value to
 462                                   propagate provided
 463
 464 **/
 465 EFI_STATUS
 466 EFIAPI
 467 VmTdExitHandleVe (
 468   IN OUT EFI_EXCEPTION_TYPE  *ExceptionType,
 469   IN OUT EFI_SYSTEM_CONTEXT  SystemContext
 470   )
 471 {
 472   UINT64                  Status;
 473   TD_RETURN_DATA          ReturnData;
 474   EFI_SYSTEM_CONTEXT_X64  *Regs;
 475
 476   Regs   = SystemContext.SystemContextX64;
 477   Status = TdCall (TDCALL_TDGETVEINFO, 0, 0, 0, &ReturnData);
 478   ASSERT (Status == 0);
 479   if (Status != 0) {
 480     DEBUG ((DEBUG_ERROR, "#VE happened. TDGETVEINFO failed with Status = 0x%llx\n", Status));
 481     TdVmCall (TDVMCALL_HALT, 0, 0, 0, 0, 0);
 482   }
 483
 484   switch (ReturnData.VeInfo.ExitReason) {
 485     case EXIT_REASON_CPUID:
 486       Status = CpuIdExit (Regs, &ReturnData.VeInfo);
 487       DEBUG ((
 488         DEBUG_VERBOSE,
 489         "CPUID #VE happened, ExitReasion is %d, ExitQualification = 0x%x.\n",
 490         ReturnData.VeInfo.ExitReason,
 491         ReturnData.VeInfo.ExitQualification.Val
 492         ));
 493       break;
 494
 495     case EXIT_REASON_HLT:
 496       Status = TdVmCall (EXIT_REASON_HLT, 0, 0, 0, 0, 0);
 497       break;
 498
 499     case EXIT_REASON_IO_INSTRUCTION:
 500       Status = IoExit (Regs, &ReturnData.VeInfo);
 501       DEBUG ((
 502         DEBUG_VERBOSE,
 503         "IO_Instruction #VE happened, ExitReasion is %d, ExitQualification = 0x%x.\n",
 504         ReturnData.VeInfo.ExitReason,
 505         ReturnData.VeInfo.ExitQualification.Val
 506         ));
 507       break;
 508
 509     case EXIT_REASON_MSR_READ:
 510       Status = ReadMsrExit (Regs, &ReturnData.VeInfo);
 511       DEBUG ((
 512         DEBUG_VERBOSE,
 513         "RDMSR #VE happened, ExitReasion is %d, ExitQualification = 0x%x. Regs->Rcx=0x%llx, Status = 0x%llx\n",
 514         ReturnData.VeInfo.ExitReason,
 515         ReturnData.VeInfo.ExitQualification.Val,
 516         Regs->Rcx,
 517         Status
 518         ));
 519       break;
 520
 521     case EXIT_REASON_MSR_WRITE:
 522       Status = WriteMsrExit (Regs, &ReturnData.VeInfo);
 523       DEBUG ((
 524         DEBUG_VERBOSE,
 525         "WRMSR #VE happened, ExitReasion is %d, ExitQualification = 0x%x. Regs->Rcx=0x%llx, Status = 0x%llx\n",
 526         ReturnData.VeInfo.ExitReason,
 527         ReturnData.VeInfo.ExitQualification.Val,
 528         Regs->Rcx,
 529         Status
 530         ));
 531       break;
 532
 533     case EXIT_REASON_EPT_VIOLATION:
 534       Status = MmioExit (Regs, &ReturnData.VeInfo);
 535       DEBUG ((
 536         DEBUG_VERBOSE,
 537         "MMIO #VE happened, ExitReasion is %d, ExitQualification = 0x%x.\n",
 538         ReturnData.VeInfo.ExitReason,
 539         ReturnData.VeInfo.ExitQualification.Val
 540         ));
 541       break;
 542
 543     case EXIT_REASON_VMCALL:
 544     case EXIT_REASON_MWAIT_INSTRUCTION:
 545     case EXIT_REASON_MONITOR_INSTRUCTION:
 546     case EXIT_REASON_WBINVD:
 547     case EXIT_REASON_RDPMC:
 548       /* Handle as nops. */
 549       break;
 550
 551     default:
 552       DEBUG ((
 553         DEBUG_ERROR,
 554         "Unsupported #VE happened, ExitReason is %d, ExitQualification = 0x%x.\n",
 555         ReturnData.VeInfo.ExitReason,
 556         ReturnData.VeInfo.ExitQualification.Val
 557         ));
 558
 559       ASSERT (FALSE);
 560       CpuDeadLoop ();
 561   }
 562
 563   if (Status) {
 564     DEBUG ((
 565       DEBUG_ERROR,
 566       "#VE Error (0x%llx) returned from host, ExitReason is %d, ExitQualification = 0x%x.\n",
 567       Status,
 568       ReturnData.VeInfo.ExitReason,
 569       ReturnData.VeInfo.ExitQualification.Val
 570       ));
 571
 572     TdVmCall (TDVMCALL_HALT, 0, 0, 0, 0, 0);
 573   }
 574
 575   SystemContext.SystemContextX64->Rip += ReturnData.VeInfo.ExitInstructionLength;
 576   return EFI_SUCCESS;
 577 }