Re: [edk2-devel] [PATCH v3 2/5] OvmfPkg/VmgExitLib: Add support for new MMIO MOV opcodes

["Laszlo Ersek" <lersek@redhat.com>]

On 04/29/21 19:19, Lendacky, Thomas wrote:
> On 4/29/21 12:12 PM, Tom Lendacky wrote:
>> 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: c45f678a1ea2080344e125dc55b14e4b9f98483d
>> 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>
> 
> Sorry, Laszlo, I forgot to include your Acked-by: on this patch.

np

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

> 
> Tom
> 
>> ---
>>  OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c | 111 ++++++++++++++++++++
>>  1 file changed, 111 insertions(+)
>>
>> diff --git a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
>> index b716541ad170..41b0c8cc5312 100644
>> --- a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
>> +++ b/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);
>>    }
>>
> 
> 
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