Re: [PATCH v7 08/43] UefiCpuPkg: Implement library support for VMGEXIT

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

On 5/8/20 8:06 PM, Dong, Eric wrote:
> Hi Tom,
> 
>> -----Original Message-----
>> From: Tom Lendacky <thomas.lendacky@amd.com>
>> Sent: Thursday, April 23, 2020 1:41 AM
>> To: devel@edk2.groups.io
>> Cc: Justen, Jordan L <jordan.l.justen@intel.com>; Laszlo Ersek
>> <lersek@redhat.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>; Kinney,
>> Michael D <michael.d.kinney@intel.com>; Gao, Liming
>> <liming.gao@intel.com>; Dong, Eric <eric.dong@intel.com>; Ni, Ray
>> <ray.ni@intel.com>; Brijesh Singh <brijesh.singh@amd.com>
>> Subject: [PATCH v7 08/43] UefiCpuPkg: Implement library support for
>> VMGEXIT
>>
>> BZ: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D2198&amp;data=02%7C01%7Cthomas.lendacky%40amd.com%7C263f75f798c64b75e23508d7f3b53108%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637245831845366269&amp;sdata=TndzK3JmXQFNGBHSfbsSPr%2BGY8NMVX%2B1Durfner4k1I%3D&amp;reserved=0
>>
>> To support issuing a VMGEXIT instruction, create a library that can be used to
>> perform GHCB and VMGEXIT related operations and to issue the actual
>> VMGEXIT instruction when using the GHCB.
>>
>> Additionally, two VMGEXIT / MMIO related functions are created to support
>> flash emulation. Flash emulation currently is done by marking the flash area
>> as read-only and taking a nested page fault to perform the emulation of the
>> instruction. However, emulation cannot be performed because there is no
>> instruction decode assist support when SEV-ES is enabled. Provide routines
>> to initiate an MMIO request to perform actual writes to flash.
>>
>> Cc: Eric Dong <eric.dong@intel.com>
>> Cc: Ray Ni <ray.ni@intel.com>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Acked-by: Laszlo Ersek <lersek@redhat.com>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>> ---
>>   UefiCpuPkg/UefiCpuPkg.dec                    |   3 +
>>   UefiCpuPkg/UefiCpuPkg.dsc                    |   2 +
>>   UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf |  33 +++
>>   UefiCpuPkg/Include/Library/VmgExitLib.h      | 117 ++++++++
>>   UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c   | 293
>> +++++++++++++++++++
>>   UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni |  15 +
>>   6 files changed, 463 insertions(+)
>>   create mode 100644 UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>>   create mode 100644 UefiCpuPkg/Include/Library/VmgExitLib.h
>>   create mode 100644 UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>>   create mode 100644 UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>>
>> diff --git a/UefiCpuPkg/UefiCpuPkg.dec b/UefiCpuPkg/UefiCpuPkg.dec
>> index df5d02bae6b4..cb92f34b6f55 100644
>> --- a/UefiCpuPkg/UefiCpuPkg.dec
>> +++ b/UefiCpuPkg/UefiCpuPkg.dec
>> @@ -53,6 +53,9 @@ [LibraryClasses.IA32, LibraryClasses.X64]
>>     ##
>>     MpInitLib|Include/Library/MpInitLib.h
>>
>> +  ##  @libraryclass  Provides function to support VMGEXIT processing.
>> +  VmgExitLib|Include/Library/VmgExitLib.h
>> +
>>   [Guids]
>>     gUefiCpuPkgTokenSpaceGuid      = { 0xac05bf33, 0x995a, 0x4ed4, { 0xaa,
>> 0xb8, 0xef, 0x7a, 0xe8, 0xf, 0x5c, 0xb0 }}
>>     gMsegSmramGuid                 = { 0x5802bce4, 0xeeee, 0x4e33, { 0xa1, 0x30,
>> 0xeb, 0xad, 0x27, 0xf0, 0xe4, 0x39 }}
>> diff --git a/UefiCpuPkg/UefiCpuPkg.dsc b/UefiCpuPkg/UefiCpuPkg.dsc index
>> d28cb5cccb52..997840452218 100644
>> --- a/UefiCpuPkg/UefiCpuPkg.dsc
>> +++ b/UefiCpuPkg/UefiCpuPkg.dsc
>> @@ -56,6 +56,7 @@ [LibraryClasses]
>>
>> PeCoffGetEntryPointLib|MdePkg/Library/BasePeCoffGetEntryPointLib/Base
>> PeCoffGetEntryPointLib.inf
>>
>> PeCoffExtraActionLib|MdePkg/Library/BasePeCoffExtraActionLibNull/BaseP
>> eCoffExtraActionLibNull.inf
>>
>> TpmMeasurementLib|MdeModulePkg/Library/TpmMeasurementLibNull/Tp
>> mMeasurementLibNull.inf
>> +  VmgExitLib|UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>>
>>   [LibraryClasses.common.SEC]
>>
>> PlatformSecLib|UefiCpuPkg/Library/PlatformSecLibNull/PlatformSecLibNull.i
>> nf
>> @@ -136,6 +137,7 @@ [Components.IA32, Components.X64]
>>
>> UefiCpuPkg/Library/SmmCpuPlatformHookLibNull/SmmCpuPlatformHookLib
>> Null.inf
>>     UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLib.inf
>>     UefiCpuPkg/Library/SmmCpuFeaturesLib/SmmCpuFeaturesLibStm.inf
>> +  UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>>     UefiCpuPkg/PiSmmCommunication/PiSmmCommunicationPei.inf
>>     UefiCpuPkg/PiSmmCommunication/PiSmmCommunicationSmm.inf
>>     UefiCpuPkg/SecCore/SecCore.inf
>> diff --git a/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> new file mode 100644
>> index 000000000000..6acfa779e75a
>> --- /dev/null
>> +++ b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.inf
>> @@ -0,0 +1,33 @@
>> +## @file
>> +#  VMGEXIT Support Library.
>> +#
>> +#  Copyright (c) 2019, Advanced Micro Devices, Inc. All rights
>> +reserved.<BR> #  SPDX-License-Identifier: BSD-2-Clause-Patent # ##
>> +
>> +[Defines]
>> +  INF_VERSION                    = 0x00010005
>> +  BASE_NAME                      = VmgExitLib
>> +  MODULE_UNI_FILE                = VmgExitLib.uni
>> +  FILE_GUID                      = 3cd7368f-ef9b-4a9b-9571-2ed93813677e
>> +  MODULE_TYPE                    = BASE
>> +  VERSION_STRING                 = 1.0
>> +  LIBRARY_CLASS                  = VmgExitLib
>> +
>> +#
>> +# The following information is for reference only and not required by the
>> build tools.
>> +#
>> +#  VALID_ARCHITECTURES           = IA32 X64
>> +#
>> +
>> +[Sources]
>> +  VmgExitLib.c
>> +
>> +[Packages]
>> +  MdePkg/MdePkg.dec
>> +  UefiCpuPkg/UefiCpuPkg.dec
>> +
>> +[LibraryClasses]
>> +  BaseLib
>> +
>> diff --git a/UefiCpuPkg/Include/Library/VmgExitLib.h
>> b/UefiCpuPkg/Include/Library/VmgExitLib.h
>> new file mode 100644
>> index 000000000000..3bf05bebd326
>> --- /dev/null
>> +++ b/UefiCpuPkg/Include/Library/VmgExitLib.h
>> @@ -0,0 +1,117 @@
>> +/** @file
>> +  Public header file for the VMGEXIT Support library class.
>> +
>> +  This library class defines some routines used when invoking the
>> + VMGEXIT  instruction in support of SEV-ES.
>> +
>> +  Copyright (c) 2019, Advanced Micro Devices, Inc. All rights
>> + reserved.<BR>
>> +  SPDX-License-Identifier: BSD-2-Clause-Patent
>> +
>> +**/
>> +
>> +#ifndef __VMG_EXIT_LIB_H__
>> +#define __VMG_EXIT_LIB_H__
>> +
>> +#include <Register/Amd/Ghcb.h>
>> +
>> +
>> +/**
>> +  Perform VMGEXIT.
>> +
>> +  Sets the necessary fields of the GHCB, invokes the VMGEXIT
>> + instruction and  then handles the return actions.
>> +
>> +  @param[in, out]  Ghcb       A pointer to the GHCB
>> +  @param[in]       ExitCode   VMGEXIT code to be assigned to the SwExitCode
>> +                              field of the GHCB.
>> +  @param[in]       ExitInfo1  VMGEXIT information to be assigned to the
>> +                              SwExitInfo1 field of the GHCB.
>> +  @param[in]       ExitInfo2  VMGEXIT information to be assigned to the
>> +                              SwExitInfo2 field of the GHCB.
>> +
>> +  @retval  0                  VMGEXIT succeeded.
>> +  @retval  Others             VMGEXIT processing did not succeed. Exception
>> +                              number to be propagated.
>> +
>> +**/
>> +UINT64
>> +EFIAPI
>> +VmgExit (
>> +  IN OUT GHCB                *Ghcb,
>> +  IN     UINT64              ExitCode,
>> +  IN     UINT64              ExitInfo1,
>> +  IN     UINT64              ExitInfo2
>> +  );
>> +
>> +/**
>> +  Perform pre-VMGEXIT initialization/preparation.
>> +
>> +  Performs the necessary steps in preparation for invoking VMGEXIT.
>> + Must be  called before setting any fields within the GHCB.
>> +
>> +  @param[in, out]  Ghcb       A pointer to the GHCB
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgInit (
>> +  IN OUT GHCB                *Ghcb
>> +  );
>> +
>> +/**
>> +  Perform post-VMGEXIT cleanup.
>> +
>> +  Performs the necessary steps to cleanup after invoking VMGEXIT. Must
>> + be  called after obtaining needed fields within the GHCB.
>> +
>> +  @param[in, out]  Ghcb       A pointer to the GHCB
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgDone (
>> +  IN OUT GHCB                *Ghcb
>> +  );
>> +
>> +#define VMGMMIO_READ   False
>> +#define VMGMMIO_WRITE  True
>> +
>> +/**
>> +  Perform MMIO write of a buffer to a non-MMIO marked range.
>> +
>> +  Performs an MMIO write without taking a #VC. This is useful  for
>> + Flash devices, which are marked read-only.
>> +
>> +  @param[in, out]  Dest       A pointer to the destination buffer
>> +  @param[in]       Src        A pointer to the source data to be written
>> +  @param[in]       Bytes      Number of bytes to write
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgMmioWrite (
>> +  IN OUT UINT8               *Dest,
>> +  IN     UINT8               *Src,
>> +  IN     UINTN                Bytes
>> +  );
>> +
>> +/**
>> +  Issue the GHCB set AP Jump Table VMGEXIT.
>> +
>> +  Performs a VMGEXIT using the GHCB AP Jump Table exit code to save the
>> + AP Jump Table address with the hypervisor for retrieval at a later time.
>> +
>> +  @param[in]  Address  Physical address of the AP Jump Table
>> +
>> +  @retval  0           VMGEXIT succeeded.
>> +  @retval  Others      VMGEXIT processing did not succeed. Exception
>> +                       number to be propagated.
>> +
>> +**/
>> +UINT64
>> +EFIAPI
>> +VmgExitSetAPJumpTable (
>> +  IN EFI_PHYSICAL_ADDRESS  Address
>> +  );
> 
> I think above two APIs should not been added to this library, they are not the basic actions for VmgExit.
> Remove these two APIs will make the library more stable.
> 
> Also, I check all the code in this patch series, only one caller for each API, so I think we can directly
> move these codes to the caller. If later more and more callers need to use these two APIs, we can
> create another service library to convenient the callers.

Ok, let me check into that. It should be very doable, especially with the 
change to a NULL library implementation that I want for the general case.

Thanks,
Tom

> 
> I ignore all the coding style related issues in this patch because I assume you have passed ECC
> checks in your new patches.
> 
> Thanks,
> Eric
>> +
>> +#endif
>> diff --git a/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>> b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>> new file mode 100644
>> index 000000000000..6137b1a0eb64
>> --- /dev/null
>> +++ b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.c
>> @@ -0,0 +1,293 @@
>> +/** @file
>> +  VMGEXIT Support Library.
>> +
>> +  Copyright (c) 2019, Advanced Micro Devices, Inc. All rights
>> + reserved.<BR>
>> +  SPDX-License-Identifier: BSD-2-Clause-Patent
>> +
>> +**/
>> +
>> +#include <Base.h>
>> +#include <Uefi.h>
>> +#include <Library/BaseMemoryLib.h>
>> +#include <Register/Amd/Ghcb.h>
>> +#include <Register/Amd/Msr.h>
>> +
>> +/**
>> +  Check for VMGEXIT error
>> +
>> +  Check if the hypervisor has returned an error after completion of the
>> + VMGEXIT  by examining the SwExitInfo1 field of the GHCB.
>> +
>> +  @param[in]  Ghcb       A pointer to the GHCB
>> +
>> +  @retval  0             VMGEXIT succeeded.
>> +  @retval  Others        VMGEXIT processing did not succeed. Exception
>> number to
>> +                         be propagated.
>> +
>> +**/
>> +STATIC
>> +UINT64
>> +VmgExitErrorCheck (
>> +  IN GHCB                *Ghcb
>> +  )
>> +{
>> +  GHCB_EVENT_INJECTION  Event;
>> +  GHCB_EXIT_INFO        ExitInfo;
>> +  UINT64                Status;
>> +
>> +  ExitInfo.Uint64 = Ghcb->SaveArea.SwExitInfo1;  ASSERT
>> + ((ExitInfo.Elements.Lower32Bits == 0) ||
>> +          (ExitInfo.Elements.Lower32Bits == 1));
>> +
>> +  Status = 0;
>> +  if (ExitInfo.Elements.Lower32Bits == 0) {
>> +    return Status;
>> +  }
>> +
>> +  if (ExitInfo.Elements.Lower32Bits == 1) {
>> +    ASSERT (Ghcb->SaveArea.SwExitInfo2 != 0);
>> +
>> +    // Check that the return event is valid
>> +    Event.Uint64 = Ghcb->SaveArea.SwExitInfo2;
>> +    if (Event.Elements.Valid &&
>> +        Event.Elements.Type == GHCB_EVENT_INJECTION_TYPE_EXCEPTION) {
>> +      switch (Event.Elements.Vector) {
>> +      case GP_EXCEPTION:
>> +      case UD_EXCEPTION:
>> +        // Use returned event as return code
>> +        Status = Event.Uint64;
>> +      }
>> +    }
>> +  }
>> +
>> +  if (Status == 0) {
>> +    GHCB_EVENT_INJECTION  Event;
>> +
>> +    Event.Uint64 = 0;
>> +    Event.Elements.Vector = GP_EXCEPTION;
>> +    Event.Elements.Type   = GHCB_EVENT_INJECTION_TYPE_EXCEPTION;
>> +    Event.Elements.Valid  = 1;
>> +
>> +    Status = Event.Uint64;
>> +  }
>> +
>> +  return Status;
>> +}
>> +
>> +/**
>> +  Perform VMGEXIT.
>> +
>> +  Sets the necessary fields of the GHCB, invokes the VMGEXIT
>> + instruction and  then handles the return actions.
>> +
>> +  @param[in, out]  Ghcb       A pointer to the GHCB
>> +  @param[in]       ExitCode   VMGEXIT code to be assigned to the SwExitCode
>> +                              field of the GHCB.
>> +  @param[in]       ExitInfo1  VMGEXIT information to be assigned to the
>> +                              SwExitInfo1 field of the GHCB.
>> +  @param[in]       ExitInfo2  VMGEXIT information to be assigned to the
>> +                              SwExitInfo2 field of the GHCB.
>> +
>> +  @retval  0                  VMGEXIT succeeded.
>> +  @retval  Others             VMGEXIT processing did not succeed. Exception
>> +                              number to be propagated.
>> +
>> +**/
>> +UINT64
>> +EFIAPI
>> +VmgExit (
>> +  IN OUT GHCB                *Ghcb,
>> +  IN     UINT64              ExitCode,
>> +  IN     UINT64              ExitInfo1,
>> +  IN     UINT64              ExitInfo2
>> +  )
>> +{
>> +  Ghcb->SaveArea.SwExitCode = ExitCode;
>> +  Ghcb->SaveArea.SwExitInfo1 = ExitInfo1;
>> +  Ghcb->SaveArea.SwExitInfo2 = ExitInfo2;
>> +
>> +  //
>> +  // Guest memory is used for the guest-hypervisor communication, so
>> + fence  // the invocation of the VMGEXIT instruction to ensure GHCB
>> + accesses are  // synchronized properly.
>> +  //
>> +  MemoryFence ();
>> +  AsmVmgExit ();
>> +  MemoryFence ();
>> +
>> +  return VmgExitErrorCheck (Ghcb);
>> +}
>> +
>> +/**
>> +  Perform pre-VMGEXIT initialization/preparation.
>> +
>> +  Performs the necessary steps in preparation for invoking VMGEXIT.
>> + Must be  called before setting any fields within the GHCB.
>> +
>> +  @param[in, out]  Ghcb       A pointer to the GHCB
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgInit (
>> +  IN OUT GHCB                *Ghcb
>> +  )
>> +{
>> +  SetMem (&Ghcb->SaveArea, sizeof (Ghcb->SaveArea), 0); }
>> +
>> +/**
>> +  Perform post-VMGEXIT cleanup.
>> +
>> +  Performs the necessary steps to cleanup after invoking VMGEXIT. Must
>> + be  called after obtaining needed fields within the GHCB.
>> +
>> +  @param[in, out]  Ghcb       A pointer to the GHCB
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgDone (
>> +  IN OUT GHCB                *Ghcb
>> +  )
>> +{
>> +}
>> +
>> +/**
>> +  Perform VMGEXIT MMIO read or write.
>> +
>> +  Performs the requested MMIO read or write using the VMGEXIT
>> instruction.
>> +
>> +  For an MMIO read, the data that has been read during the VMGEXIT is
>> + placed in  the SharedBuffer area of the GHCB. This is then copied to
>> + the actual  destination buffer within the guest.
>> +
>> +  For an MMIO write, the data to be written is copied into the
>> + SharedBuffer area  of the GHCB by the guest. This is then copied to
>> + the actual destination buffer  by the hypervisor during the VMGEXIT.
>> +
>> +  @param[in, out]  MmioAddress  A pointer to the MMIO buffer to be
>> read/written
>> +  @param[in, out]  Buffer       A pointer to the buffer to hold the data thas
>> +                                has been read or hold the data to be written
>> +  @param[in]       Bytes        Number of bytes to read or write
>> +  @param[in]       Write        If set, the request is for an MMIO write, else
>> +                                it is an MMIO read.
>> +
>> +  @retval  0                    VMGEXIT succeeded.
>> +  @retval  Others               VMGEXIT processing did not succeed. Exception
>> +                                number to be propagated.
>> +
>> +**/
>> +STATIC
>> +UINT64
>> +EFIAPI
>> +VmgMmio (
>> +  IN OUT UINT8               *MmioAddress,
>> +  IN OUT UINT8               *Buffer,
>> +  IN     UINTN               Bytes,
>> +  IN     BOOLEAN             Write
>> +  )
>> +{
>> +  UINT64                    MmioOp, ExitInfo1, ExitInfo2, Status;
>> +  GHCB                      *Ghcb;
>> +  MSR_SEV_ES_GHCB_REGISTER  Msr;
>> +
>> +  Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);  Ghcb
>> =
>> + Msr.Ghcb;
>> +
>> +  //
>> +  // This function is about to set fields in the GHCB. Do not execute
>> + // anything that will cause a #VC before issuing the VmgExit(). Any
>> + #VC  // will result in all GHCB settings being overwritten (this
>> + means, e.g.,  // do not add DEBUG() statements).
>> +  //
>> +  VmgInit (Ghcb);
>> +
>> +  if (Write) {
>> +    MmioOp = SvmExitMmioWrite;
>> +  } else {
>> +    MmioOp = SvmExitMmioRead;
>> +  }
>> +
>> +  ExitInfo1 = (UINT64) (UINTN) MmioAddress;
>> +  ExitInfo2 = Bytes;
>> +
>> +  if (Write) {
>> +    CopyMem (Ghcb->SharedBuffer, Buffer, Bytes);  }
>> +
>> +  Ghcb->SaveArea.SwScratch = (UINT64) (UINTN) Ghcb->SharedBuffer;
>> + Status = VmgExit (Ghcb, MmioOp, ExitInfo1, ExitInfo2);  if (Status !=
>> + 0) {
>> +    return Status;
>> +  }
>> +
>> +  if (!Write) {
>> +    CopyMem (Buffer, Ghcb->SharedBuffer, Bytes);  }
>> +
>> +  VmgDone (Ghcb);
>> +
>> +  return 0;
>> +}
>> +
>> +/**
>> +  Perform MMIO write of a buffer to a non-MMIO marked range.
>> +
>> +  Performs an MMIO write without taking a #VC. This is useful  for
>> + Flash devices, which are marked read-only.
>> +
>> +  @param[in, out]  Dest       A pointer to the destination buffer
>> +  @param[in]       Src        A pointer to the source data to be written
>> +  @param[in]       Bytes      Number of bytes to write
>> +
>> +**/
>> +VOID
>> +EFIAPI
>> +VmgMmioWrite (
>> +  IN OUT UINT8               *Dest,
>> +  IN     UINT8               *Src,
>> +  IN     UINTN                Bytes
>> +  )
>> +{
>> +  VmgMmio (Dest, Src, Bytes, TRUE);
>> +}
>> +
>> +/**
>> +  Issue the GHCB set AP Jump Table VMGEXIT.
>> +
>> +  Performs a VMGEXIT using the GHCB AP Jump Table exit code to save the
>> + AP Jump Table address with the hypervisor for retrieval at a later time.
>> +
>> +  @param[in]  Address  Physical address of the AP Jump Table
>> +
>> +  @retval  0           VMGEXIT succeeded.
>> +  @retval  Others      VMGEXIT processing did not succeed. Exception
>> +                       number to be propagated.
>> +
>> +**/
>> +UINT64
>> +EFIAPI
>> +VmgExitSetAPJumpTable (
>> +  IN EFI_PHYSICAL_ADDRESS  Address
>> +  )
>> +{
>> +  UINT64                    ExitInfo1, ExitInfo2, Status;
>> +  GHCB                      *Ghcb;
>> +  MSR_SEV_ES_GHCB_REGISTER  Msr;
>> +
>> +  Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);  Ghcb
>> =
>> + Msr.Ghcb;
>> +
>> +  VmgInit (Ghcb);
>> +
>> +  ExitInfo1 = 0;
>> +  ExitInfo2 = (UINT64) (UINTN) Address;
>> +
>> +  Status = VmgExit (Ghcb, SvmExitApJumpTable, ExitInfo1, ExitInfo2);
>> +
>> +  VmgDone (Ghcb);
>> +
>> +  return Status;
>> +}
>> +
>> diff --git a/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>> b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>> new file mode 100644
>> index 000000000000..e8656aae4726
>> --- /dev/null
>> +++ b/UefiCpuPkg/Library/VmgExitLib/VmgExitLib.uni
>> @@ -0,0 +1,15 @@
>> +// /** @file
>> +// VMGEXIT support library instance.
>> +//
>> +// VMGEXIT support library instance.
>> +//
>> +// Copyright (c) 2019, Advanced Micro Devices, Inc. All rights
>> +reserved.<BR> // SPDX-License-Identifier: BSD-2-Clause-Patent // // **/
>> +
>> +
>> +#string STR_MODULE_ABSTRACT             #language en-US "VMGEXIT
>> Support Library."
>> +
>> +#string STR_MODULE_DESCRIPTION          #language en-US "VMGEXIT
>> Support Library."
>> +
>> --
>> 2.17.1
>