OvmfPkg/VmgExitLib: Add support for new MMIO MOV opcodes

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3345

Enabling TPM support results in guest termination of an SEV-ES guest
because it uses MMIO opcodes that are not currently supported.

Add support for the new MMIO opcodes (0xA0 - 0xA3), MOV instructions which
use a memory offset directly encoded in the instruction. Also, add a DEBUG
statement to identify an unsupported MMIO opcode being used.

Fixes: c45f678a1e
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <2fdde57707b52ae39c49341c9d97053aaff56e4a.1619716333.git.thomas.lendacky@amd.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>

OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c

@@ -680,6 +680,7 @@ MmioExit (
   UINTN   Bytes;
   UINT64  *Register;
   UINT8   OpCode, SignByte;
+  UINTN   Address;
 
   Bytes = 0;
 
@@ -729,6 +730,57 @@ MmioExit (
     }
     break;
 
+  //
+  // MMIO write (MOV moffsetX, aX)
+  //
+  case 0xA2:
+    Bytes = 1;
+    //
+    // fall through
+    //
+  case 0xA3:
+    Bytes = ((Bytes != 0) ? Bytes :
+             (InstructionData->DataSize == Size16Bits) ? 2 :
+             (InstructionData->DataSize == Size32Bits) ? 4 :
+             (InstructionData->DataSize == Size64Bits) ? 8 :
+             0);
+
+    InstructionData->ImmediateSize = (UINTN) (1 << InstructionData->AddrSize);
+    InstructionData->End += InstructionData->ImmediateSize;
+
+    //
+    // This code is X64 only, so a possible 8-byte copy to a UINTN is ok.
+    // Use a STATIC_ASSERT to be certain the code is being built as X64.
+    //
+    STATIC_ASSERT (
+      sizeof (UINTN) == sizeof (UINT64),
+      "sizeof (UINTN) != sizeof (UINT64), this file must be built as X64"
+      );
+
+    Address = 0;
+    CopyMem (
+      &Address,
+      InstructionData->Immediate,
+      InstructionData->ImmediateSize
+      );
+
+    Status = ValidateMmioMemory (Ghcb, Address, Bytes);
+    if (Status != 0) {
+      return Status;
+    }
+
+    ExitInfo1 = Address;
+    ExitInfo2 = Bytes;
+    CopyMem (Ghcb->SharedBuffer, &Regs->Rax, Bytes);
+
+    Ghcb->SaveArea.SwScratch = (UINT64) Ghcb->SharedBuffer;
+    VmgSetOffsetValid (Ghcb, GhcbSwScratch);
+    Status = VmgExit (Ghcb, SVM_EXIT_MMIO_WRITE, ExitInfo1, ExitInfo2);
+    if (Status != 0) {
+      return Status;
+    }
+    break;
+
   //
   // MMIO write (MOV reg/memX, immX)
   //
@@ -811,6 +863,64 @@ MmioExit (
     CopyMem (Register, Ghcb->SharedBuffer, Bytes);
     break;
 
+  //
+  // MMIO read (MOV aX, moffsetX)
+  //
+  case 0xA0:
+    Bytes = 1;
+    //
+    // fall through
+    //
+  case 0xA1:
+    Bytes = ((Bytes != 0) ? Bytes :
+             (InstructionData->DataSize == Size16Bits) ? 2 :
+             (InstructionData->DataSize == Size32Bits) ? 4 :
+             (InstructionData->DataSize == Size64Bits) ? 8 :
+             0);
+
+    InstructionData->ImmediateSize = (UINTN) (1 << InstructionData->AddrSize);
+    InstructionData->End += InstructionData->ImmediateSize;
+
+    //
+    // This code is X64 only, so a possible 8-byte copy to a UINTN is ok.
+    // Use a STATIC_ASSERT to be certain the code is being built as X64.
+    //
+    STATIC_ASSERT (
+      sizeof (UINTN) == sizeof (UINT64),
+      "sizeof (UINTN) != sizeof (UINT64), this file must be built as X64"
+      );
+
+    Address = 0;
+    CopyMem (
+      &Address,
+      InstructionData->Immediate,
+      InstructionData->ImmediateSize
+      );
+
+    Status = ValidateMmioMemory (Ghcb, Address, Bytes);
+    if (Status != 0) {
+      return Status;
+    }
+
+    ExitInfo1 = Address;
+    ExitInfo2 = Bytes;
+
+    Ghcb->SaveArea.SwScratch = (UINT64) Ghcb->SharedBuffer;
+    VmgSetOffsetValid (Ghcb, GhcbSwScratch);
+    Status = VmgExit (Ghcb, SVM_EXIT_MMIO_READ, ExitInfo1, ExitInfo2);
+    if (Status != 0) {
+      return Status;
+    }
+
+    if (Bytes == 4) {
+      //
+      // Zero-extend for 32-bit operation
+      //
+      Regs->Rax = 0;
+    }
+    CopyMem (&Regs->Rax, Ghcb->SharedBuffer, Bytes);
+    break;
+
   //
   // MMIO read w/ zero-extension ((MOVZX regX, reg/memX)
   //
@@ -888,6 +998,7 @@ MmioExit (
     break;
 
   default:
+    DEBUG ((DEBUG_ERROR, "Invalid MMIO opcode (%x)\n", OpCode));
     Status = GP_EXCEPTION;
     ASSERT (FALSE);
   }