Re: [edk2-devel] [PATCH V1 1/1] MdeModulePkg: Add Definition of EDKII_PEI_VARIABLE_PPI

["Michael Kubacki" <mikuback@linux.microsoft.com>]

There's a lot of major pending changes I'm aware of in the variable 
stack. At least:

1. "Variable Protection" - Extensions for encryption and replay protection
https://github.com/judahvang/edk2/tree/rpmc-update

2. "Storage Agnostic Variables / UEFI Variable Router"
https://github.com/makubacki/edk2/tree/storage_agnostic_uefi_variables_w_runtime_cache

I've rebased this a few times and probably will again.

3. "PEI write support"
This email thread

4. Host-based UEFI variable testing we are working on at Microsoft

Each of these capabilities is nice but, the reality is, the UEFI 
variable driver already has so much technical debt that each of these 
individually are going to significantly impact others. From what I've 
observed, most large variable contributions tend to fix similar problems 
that affect their code - duplicated helper logic between PEI and DXE 
drivers, lack of modularity so individual functions are difficult to 
test and reuse, etc.  Major vendors often have driver overrides because 
variables have evolved over the years and they need improved 
traceability, data offload, security features, etc.

(4) is an attempt to manage some of the integration complexity to some 
extent by increasing test coverage in an quick and controlled manner.

Since these are all mostly new features, I would prefer to build them in 
a new clean design that considers modern use cases upfront rather than 
continuing to bolt onto the existing code (and at the minimum, introduce 
a lot of merge conflicts between everyone in the process).

It could reuse a lot of preexisting work but integrate things more 
cohesively and with better testing infrastructure in place.

Does anyone think a workstream or feature branch for that would be a 
better approach?

Thanks,
Michael

On 6/22/2022 3:51 PM, Brian J. Johnson wrote:
> Nate,
> 
> FWIW I welcome having a standard interface to write EFI variables in 
> PEI.  Not all platforms store variables in flash, so they don't all have 
> tricky issues with fault-tolerant writes to h/w which is also being used 
> for code fetches.  And writing variables early makes it possible to 
> modify settings in response to h/w changes and external requests, 
> without having to boot all the way to DXE, write the variables, then 
> trigger a reset.
> 
> Brian J. Johnson
> -------- Original Message --------
> From: Nate DeSimone [mailto:nathaniel.l.desimone@intel.com]
> Sent: Monday, June 13, 2022, 4:31 PM
> To: Yao, Jiewen <jiewen.yao@intel.com>, devel@edk2.groups.io 
> <devel@edk2.groups.io>, michael.kubacki@outlook.com 
> <michael.kubacki@outlook.com>
> Cc: Wang, Jian J <jian.j.wang@intel.com>, Gao, Liming 
> <gaoliming@byosoft.com.cn>, Kinney, Michael D 
> <michael.d.kinney@intel.com>, Oram, Isaac W <isaac.w.oram@intel.com>, 
> Chiu, Chasel <chasel.chiu@intel.com>, Cheng, Gao <gao.cheng@intel.com>, 
> Zhang, Di <di.zhang@intel.com>, Bu, Daocheng <daocheng.bu@intel.com>, 
> Kubacki, Michael <michael.kubacki@microsoft.com>
> Subject: [edk2-devel] [PATCH V1 1/1] MdeModulePkg: Add Definition of 
> EDKII_PEI_VARIABLE_PPI
> 
> Hi Jiewen,
> 
> I am fine with deferring the submission of this to edk2 until the 
> implementation is ready for review. I just wanted to get feedback on the 
> API so that once the implementation patch series arrives we will at 
> least that that piece of the review done. I would say this thread 
> achieved that goal. Thank you for the pointer to the protected variable 
> code, we will review it and make sure that no issues would arise from 
> the pre-memory PEI implementation.
> 
> Thanks,
> Nate
> 
> -----Original Message-----
> From: Yao, Jiewen <jiewen.yao@intel.com>
> Sent: Friday, June 10, 2022 6:09 PM
> To: Desimone, Nathaniel L <nathaniel.l.desimone@intel.com>; 
> devel@edk2.groups.io; michael.kubacki@outlook.com
> Cc: Wang, Jian J <jian.j.wang@intel.com>; Gao, Liming 
> <gaoliming@byosoft.com.cn>; Kinney, Michael D 
> <michael.d.kinney@intel.com>; Oram, Isaac W <isaac.w.oram@intel.com>; 
> Chiu, Chasel <chasel.chiu@intel.com>; Cheng, Gao <gao.cheng@intel.com>; 
> Zhang, Di <di.zhang@intel.com>; Bu, Daocheng <daocheng.bu@intel.com>; 
> Kubacki, Michael <michael.kubacki@microsoft.com>
> Subject: RE: [edk2-devel] [PATCH V1 1/1] MdeModulePkg: Add Definition of 
> EDKII_PEI_VARIABLE_PPI
> 
> Thanks for the response.
> 
> 1) Why we need "enable UEFI variable write before permanent memory is 
> available"?
> 
> 2) If the implementation is not ready, I do have concern to add it so 
> early in EDKII.
> If I don’t have a big picture, I am not sure how to review the 
> completeness.
> 
> Can we put it to EDKII-staging 
> (https://github.com/tianocore/edk2-staging) for a moment?
> I don’t see the need to add the interface now for work-in-progress 
> feature, since there is no consumer and no producer.
> 
> Another reason is that I happen to know other feature (in EDKII stage) 
> is impacting variable driver.
> https://github.com/tianocore/edk2-staging/tree/ProtectedVariable/libs
> 
> Please do consider that as well - how to write a protected variable in 
> PEI phase.
> 
> Thank you
> Yao Jiewen
> 
>> -----Original Message-----
>> From: Desimone, Nathaniel L <nathaniel.l.desimone@intel.com>
>> Sent: Saturday, June 11, 2022 5:49 AM
>> To: Yao, Jiewen <jiewen.yao@intel.com>; devel@edk2.groups.io;
>> michael.kubacki@outlook.com
>> Cc: Wang, Jian J <jian.j.wang@intel.com>; Gao, Liming
>> <gaoliming@byosoft.com.cn>; Kinney, Michael D
>> <michael.d.kinney@intel.com>; Oram, Isaac W <isaac.w.oram@intel.com>;
>> Chiu, Chasel <chasel.chiu@intel.com>; Cheng, Gao
>> <gao.cheng@intel.com>; Zhang, Di <di.zhang@intel.com>; Bu, Daocheng
>> <daocheng.bu@intel.com>; Kubacki, Michael
>> <michael.kubacki@microsoft.com>
>> Subject: RE: [edk2-devel] [PATCH V1 1/1] MdeModulePkg: Add Definition
>> of EDKII_PEI_VARIABLE_PPI
>>
>> Hi Jiewen,
>>
>> Thanks for the feedback, per your questions:
>>
>> 1. The primary use case for this is to enable UEFI variable writes
>> before permanent memory is available.
>> 2. The implementation is a work in progress. We will provide it
>> shortly. As this will be a rather large patch set, I would like to get
>> this piece in place beforehand so that the reviewers can focus on the
>> implementation separate from the API definition.
>> 3. No impact to secure boot. We are not going to support writing to
>> authenticated variables in PEI. As mentioned in the comments, if a
>> PEIM wishes to update any of the authenticated variables it must use
>> the existing HOB mechanism to have a later DXE phase perform the update.
>> 4. With regard to atomicity, we have a complete implementation of the
>> fault tolerant write services operational in Pre-Memory PEI.
>> 5. Good point on the S3 resume, we will need to add an SMI to have the
>> variable services re-initialize the mNvVariableCache.
>>
>> Hope that helps,
>> Nate
>>
>> -----Original Message-----
>> From: Yao, Jiewen <jiewen.yao@intel.com>
>> Sent: Friday, June 10, 2022 9:56 AM
>> To: devel@edk2.groups.io; michael.kubacki@outlook.com; Desimone,
>> Nathaniel L <nathaniel.l.desimone@intel.com>
>> Cc: Wang, Jian J <jian.j.wang@intel.com>; Gao, Liming
>> <gaoliming@byosoft.com.cn>; Kinney, Michael D
>> <michael.d.kinney@intel.com>; Oram, Isaac W <isaac.w.oram@intel.com>;
>> Chiu, Chasel <chasel.chiu@intel.com>; Cheng, Gao
>> <gao.cheng@intel.com>; Zhang, Di <di.zhang@intel.com>; Bu, Daocheng
>> <daocheng.bu@intel.com>; Kubacki, Michael
>> <michael.kubacki@microsoft.com>
>> Subject: RE: [edk2-devel] [PATCH V1 1/1] MdeModulePkg: Add Definition
>> of EDKII_PEI_VARIABLE_PPI
>>
>> Hi
>>
>> I am curious why we need this interface. Why we need write variable
>> capability in PEI phase?
>>
>> Where is the implementation of this? I prefer to see an implementation
>> submitted together with header file.
>> For example, what is the impact to secure boot related feature, how to
>> write auth variable in PEI, how PEI write variable cowork with SMM
>> version in S3 resume phase, how to support variable atomicity, etc.
>>
>> Thank you
>> Yao Jiewen
>>
>>
>>> -----Original Message-----
>>> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of
>>> Michael Kubacki
>>> Sent: Friday, June 10, 2022 10:00 AM
>>> To: devel@edk2.groups.io; Desimone, Nathaniel L
>>> <nathaniel.l.desimone@intel.com>
>>> Cc: Wang, Jian J <jian.j.wang@intel.com>; Gao, Liming
>>> <gaoliming@byosoft.com.cn>; Kinney, Michael D
>>> <michael.d.kinney@intel.com>; Oram, Isaac W
>>> <isaac.w.oram@intel.com>; Chiu, Chasel <chasel.chiu@intel.com>;
>>> Cheng, Gao <gao.cheng@intel.com>; Zhang, Di <di.zhang@intel.com>;
>>> Bu, Daocheng <daocheng.bu@intel.com>; Kubacki, Michael
>>> <michael.kubacki@microsoft.com>
>>> Subject: Re: [edk2-devel] [PATCH V1 1/1] MdeModulePkg: Add
>>> Definition of EDKII_PEI_VARIABLE_PPI
>>>
>>> Is this change just adding the interface to Tianocore or is there
>>> additional implementation planned as well?
>>>
>>> ---
>>>
>>> I thought we were following this convention now:
>>>
>>> "#ifndef __PEI_VARIABLE_PPI_H_" -> "#ifndef PEI_VARIABLE_PPI_H_"
>>>
>>> Some other comments are inline.
>>>
>>> Regards,
>>> Michael
>>>
>>> On 6/9/2022 9:17 PM, Nate DeSimone wrote:
>>>> Adds definition of EDKII_PEI_VARIABLE_PPI, a pre-cursor to
>>>> enabling variable writes in the PEI environment.
>>>>
>>>> Cc: Jian J Wang <jian.j.wang@intel.com>
>>>> Cc: Liming Gao <gaoliming@byosoft.com.cn>
>>>> Cc: Michael D Kinney <michael.d.kinney@intel.com>
>>>> Cc: Isaac Oram <isaac.w.oram@intel.com>
>>>> Cc: Chasel Chiu <chasel.chiu@intel.com>
>>>> Cc: Gao Cheng <gao.cheng@intel.com>
>>>> Cc: Di Zhang <di.zhang@intel.com>
>>>> Cc: Daocheng Bu <daocheng.bu@intel.com>
>>>> Cc: Michael Kubacki <michael.kubacki@microsoft.com>
>>>> Signed-off-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
>>>> ---
>>>>    MdeModulePkg/Include/Ppi/Variable.h | 189
>>> ++++++++++++++++++++++++++++
>>>>    MdeModulePkg/MdeModulePkg.dec       |   3 +
>>>>    2 files changed, 192 insertions(+)
>>>>    create mode 100644 MdeModulePkg/Include/Ppi/Variable.h
>>>>
>>>> diff --git a/MdeModulePkg/Include/Ppi/Variable.h
>>> b/MdeModulePkg/Include/Ppi/Variable.h
>>>> new file mode 100644
>>>> index 0000000000..97dc7ceefa
>>>> --- /dev/null
>>>> +++ b/MdeModulePkg/Include/Ppi/Variable.h
>>>> @@ -0,0 +1,189 @@
>>>> +/** @file
>>>> +  EDKII PEI Variable Protocol provides an implementation of
>>>> +variables
>>>
>>> [MK] Was "EDKII PEI Variable PPI" intended?
>>>
>>>> +  intended for use as a means to store data in the PEI environment.
>>>> +
>>>> +  Copyright (c) 2022, Intel Corporation. All rights reserved.<BR>
>>>> +  SPDX-License-Identifier: BSD-2-Clause-Patent
>>>> +
>>>> +**/
>>>> +
>>>> +#ifndef __PEI_VARIABLE_PPI_H_
>>>> +#define __PEI_VARIABLE_PPI_H_
>>>> +
>>>> +#define EDKII_PEI_VARIABLE_PPI_GUID \
>>>> +  { \
>>>> +    0xe7b2cd04, 0x4b14, 0x44c2, { 0xb7, 0x48, 0xce, 0xaf, 0x2b,
>>>> +0x66, 0x4a,
>>> 0xb0 } \
>>>> +  }
>>>> +
>>>> +typedef struct _EDKII_PEI_VARIABLE_PPI EDKII_PEI_VARIABLE_PPI;
>>>> +
>>>> +/**
>>>> +  This service retrieves a variable's value using its name and GUID.
>>>> +
>>>> +  Read the specified variable from the UEFI variable store. If
>>>> + the Data  buffer is too small to hold the contents of the
>>>> + variable, the error EFI_BUFFER_TOO_SMALL is returned and
>>>> + DataSize is set to the  required buffer size to obtain the data.
>>>> +
>>>> +  @param[in]        This              A pointer to this instance of 
>>>> the
>>> EDKII_PEI_VARIABLE_PPI.
>>>> +  @param[in]        VariableName      A pointer to a 
>>>> null-terminated string that
>>> is the variable's name.
>>>> +  @param[in]        VariableGuid      A pointer to an EFI_GUID that 
>>>> is the
>>> variable's GUID. The combination of
>>>> +                                      VariableGuid and VariableName 
>>>> must be unique.
>>>> +  @param[out]       Attributes        If non-NULL, on return, 
>>>> points to the
>>> variable's attributes.
>>>> +  @param[in, out]   DataSize          On entry, points to the size 
>>>> in bytes of the
>>> Data buffer.
>>>> +                                      On return, points to the
>>>> + size of the data returned in
>> Data.
>>>> +  @param[out]       Data              Points to the buffer which 
>>>> will hold the
>>> returned variable value.
>>>> +                                      May be NULL with a zero
>>>> + DataSize in order to determine
>>> the size of the
>>>> +                                      buffer needed.
>>>> +
>>>> +  @retval EFI_SUCCESS                 The variable was read 
>>>> successfully.
>>>> +  @retval EFI_NOT_FOUND               The variable was not found.
>>>> +  @retval EFI_BUFFER_TOO_SMALL        The DataSize is too small for 
>>>> the
>>> resulting data.
>>>> +                                      DataSize is updated with the 
>>>> size required for
>>>> +                                      the specified variable.
>>>> +  @retval EFI_INVALID_PARAMETER       VariableName, VariableGuid,
>>> DataSize or Data is NULL.
>>>> +  @retval EFI_DEVICE_ERROR            The variable could not be 
>>>> retrieved
>>> because of a device error.
>>>> +
>>>> +**/
>>>> +typedef
>>>> +EFI_STATUS
>>>> +(EFIAPI *EDKII_PEI_GET_VARIABLE)(
>>>> +  IN CONST  EDKII_PEI_VARIABLE_PPI    *This,
>>>> +  IN CONST  CHAR16                    *VariableName,
>>>> +  IN CONST  EFI_GUID                  *VariableGuid,
>>>> +  OUT       UINT32                    *Attributes,
>>>
>>> [MK] Based on the description, Attributes should be marked "OPTIONAL".
>>>
>>>> +  IN OUT    UINTN                     *DataSize,
>>>> +  OUT       VOID                      *Data OPTIONAL
>>>> +  );
>>>> +
>>>> +/**
>>>> +  Return the next variable name and GUID.
>>>> +
>>>> +  This function is called multiple times to retrieve the
>>>> + VariableName  and VariableGuid of all variables currently
>>>> + available in the
>> system.
>>>> +  On each call, the previous results are passed into the
>>>> + interface, and, on return, the interface returns the data for
>>>> + the next interface. When the entire variable list has been
>>>> + returned, EFI_NOT_FOUND is returned.
>>>> +
>>>
>>> [MK] I know other descriptions don't usually have it but it would be
>>> nice to describe the initial calling values expected.
>>>
>>>> +  @param[in]        This              A pointer to this instance of 
>>>> the
>>> EDKII_PEI_VARIABLE_PPI.
>>>> +  @param[in, out]   VariableNameSize  On entry, points to the size 
>>>> of the
>>> buffer pointed to by VariableName.
>>>> +                                      On return, the size of the 
>>>> variable name buffer.
>>>> +  @param[in, out]   VariableName      On entry, a pointer to a null-
>> terminated
>>> string that is the variable's name.
>>>> +                                      On return, points to the
>>>> + next variable's null-terminated
>>> name string.
>>>> +  @param[in, out]   VariableGuid      On entry, a pointer to an 
>>>> EFI_GUID that
>> is
>>> the variable's GUID.
>>>> +                                      On return, a pointer to the 
>>>> next variable's GUID.
>>>> +
>>>> +  @retval EFI_SUCCESS                 The variable was read 
>>>> successfully.
>>>> +  @retval EFI_NOT_FOUND               The variable could not be found.
>>>> +  @retval EFI_BUFFER_TOO_SMALL        The VariableNameSize is too 
>>>> small
>> for
>>> the resulting
>>>> +                                      data. VariableNameSize is 
>>>> updated with the size
>>>> +                                      required for the specified 
>>>> variable.
>>>> +  @retval EFI_INVALID_PARAMETER       VariableName, VariableGuid or
>>>> +                                      VariableNameSize is NULL.
>>>> +  @retval EFI_DEVICE_ERROR            The variable could not be 
>>>> retrieved
>>> because of a device error.
>>>> +
>>>> +**/
>>>> +typedef
>>>> +EFI_STATUS
>>>> +(EFIAPI *EDKII_PEI_GET_NEXT_VARIABLE_NAME)(
>>>> +  IN CONST  EDKII_PEI_VARIABLE_PPI    *This,
>>>> +  IN OUT    UINTN                     *VariableNameSize,
>>>> +  IN OUT    CHAR16                    *VariableName,
>>>> +  IN OUT    EFI_GUID                  *VariableGuid
>>>> +  );
>>>> +
>>>> +/**
>>>> +  Sets the value of a variable.
>>>> +
>>>> +  @param[in]        This              A pointer to this instance of 
>>>> the
>>> EDKII_PEI_VARIABLE_PPI.
>>>> +  @param[in]        VariableName      A Null-terminated string that 
>>>> is the name
>>> of the vendor's variable.
>>>> +                                      Each VariableName is unique 
>>>> for each VendorGuid.
>>> VariableName must
>>>> +                                      contain 1 or more characters.
>>>> + If VariableName is an
>>> empty string,
>>>> +                                      then EFI_INVALID_PARAMETER is 
>>>> returned.
>>>> +  @param[in]        VendorGuid        A unique identifier for the 
>>>> vendor.
>>>> +  @param[in]        Attributes        Attributes bitmask to set for 
>>>> the variable.
>>>> +  @param[in]        DataSize          The size in bytes of the Data 
>>>> buffer. Unless
>>> the EFI_VARIABLE_APPEND_WRITE
>>>> +                                      attribute is set, a size of
>>>> + zero causes the variable to be
>>> deleted. When the
>>>> +                                      EFI_VARIABLE_APPEND_WRITE
>>>> + attribute is set, then a
>>> SetVariable() call with a
>>>> +                                      DataSize of zero will not
>>>> + cause any change to the
>>> variable value.
>>>> +  @param[in]        Data              The contents for the variable.
>>>> +
>>>> +  @retval EFI_SUCCESS                 The firmware has successfully 
>>>> stored the
>>> variable and its data as
>>>> +                                      defined by the Attributes.
>>>> +  @retval EFI_INVALID_PARAMETER       An invalid combination of 
>>>> attribute
>>> bits, name, and GUID was supplied, or the
>>>> +                                      DataSize exceeds the maximum 
>>>> allowed.
>>>> +  @retval EFI_INVALID_PARAMETER       VariableName is an empty string.
>>>> +  @retval EFI_OUT_OF_RESOURCES        Not enough storage is 
>>>> available to
>>> hold the variable and its data.
>>>> +  @retval EFI_DEVICE_ERROR            The variable could not be 
>>>> retrieved due
>>> to a hardware error.
>>>> +  @retval EFI_WRITE_PROTECTED         The variable in question is 
>>>> read-only.
>>>> +  @retval EFI_WRITE_PROTECTED         The variable in question 
>>>> cannot be
>>> deleted.
>>>> +  @retval EFI_SECURITY_VIOLATION      The variable could not be 
>>>> written
>> due
>>> to EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS,
>>>> +                                      or
>>> EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS, or
>>>> +
>>>> + EFI_VARIABLE_ENHANCED_AUTHENTICATED_ACCESS
>>> being set. Writing to authenticated
>>>> +                                      variables is not supported in 
>>>> the PEI environment.
>>> Updates to authenticated
>>>> +                                      variables can be requested
>>>> + during PEI via the
>>> EFI_AUTHENTICATED_VARIABLE_HOB, but
>>>> +                                      these updates won't be
>>>> + written to non-volatile storage
>>> until later in DXE. See
>>>> +
>>>> + MdeModulePkg/Include/Guid/VariableFormat.h for
>>> more details on
>>>> +                                      EFI_AUTHENTICATED_VARIABLE_HOB.
>>>
>>> [MK] I didn't see "EFI_AUTHENTICATED_VARIABLE_HOB" mentioned in
>>> VariableFormat.h.
>>>
>>> [MK] It seems that if a contract for producing and then consuming
>>> this HOB is going to be defined between the HOB producer and
>>> consumer phase, it should be described in something like the PI Spec.
>>>
>>>> +  @retval EFI_NOT_FOUND               The variable trying to be 
>>>> updated or
>>> deleted was not found.
>>>> +
>>>> +**/
>>>> +typedef
>>>> +EFI_STATUS
>>>> +(EFIAPI *EDKII_PEI_SET_VARIABLE)(
>>>> +  IN CONST  EDKII_PEI_VARIABLE_PPI    *This,
>>>> +  IN        CHAR16                    *VariableName,
>>>> +  IN        EFI_GUID                  *VendorGuid,
>>>> +  IN        UINT32                    Attributes,
>>>> +  IN        UINTN                     DataSize,
>>>> +  IN        VOID                      *Data
>>>> +  );
>>>> +
>>>> +/**
>>>> +  Returns information about the UEFI variables.
>>>> +
>>>> +  @param[in]        This                          A pointer to this 
>>>> instance of the
>>> EDKII_PEI_VARIABLE_PPI.
>>>> +  @param[in]        Attributes                    Attributes 
>>>> bitmask to specify the type
>>> of variables on
>>>> +                                                  which to return 
>>>> information.
>>>> +  @param[out]       MaximumVariableStorageSize    On output the 
>>>> maximum
>>> size of the storage space
>>>> +                                                  available for
>>>> + the EFI variables associated with
>> the
>>>> +                                                  attributes 
>>>> specified.
>>>> +  @param[out]       RemainingVariableStorageSize  Returns the 
>>>> remaining
>> size
>>> of the storage space
>>>> +                                                  available for
>>>> + the EFI variables associated with
>> the
>>>> +                                                  attributes 
>>>> specified.
>>>> +  @param[out]       MaximumVariableSize           Returns the 
>>>> maximum size of
>>> the individual EFI
>>>> +                                                  variables
>>>> + associated with the attributes
>> specified.
>>>> +
>>>> +  @retval EFI_SUCCESS                             Valid answer 
>>>> returned.
>>>> +  @retval EFI_INVALID_PARAMETER                   An invalid 
>>>> combination of
>>> attribute bits was supplied
>>>> +  @retval EFI_UNSUPPORTED                         The attribute is 
>>>> not supported
>> on
>>> this platform, and the
>>>> +
>>>> + MaximumVariableStorageSize,
>>>> +
>>>> + RemainingVariableStorageSize,
>>> MaximumVariableSize
>>>> +                                                  are undefined.
>>>> +
>>>> +**/
>>>> +typedef
>>>> +EFI_STATUS
>>>> +(EFIAPI *EDKII_PEI_QUERY_VARIABLE_INFO)(
>>>> +  IN CONST  EDKII_PEI_VARIABLE_PPI    *This,
>>>> +  IN        UINT32                    Attributes,
>>>> +  OUT       UINT64                    *MaximumVariableStorageSize,
>>>> +  OUT       UINT64                    *RemainingVariableStorageSize,
>>>> +  OUT       UINT64                    *MaximumVariableSize
>>>> +  );
>>>> +
>>>> +///
>>>> +/// PEI Variable Protocol is intended for use as a means
>>>
>>> [MK] Was "PEI Variable PPI" intended?
>>>
>>>> +/// to store data in the PEI environment.
>>>> +///
>>>> +struct _EDKII_PEI_VARIABLE_PPI {
>>>> +  EDKII_PEI_GET_VARIABLE            GetVariable;
>>>> +  EDKII_PEI_GET_NEXT_VARIABLE_NAME  GetNextVariableName;
>>>> +  EDKII_PEI_SET_VARIABLE            SetVariable;
>>>> +  EDKII_PEI_QUERY_VARIABLE_INFO     QueryVariableInfo;
>>>> +};
>>>> +
>>>> +extern EFI_GUID  gEdkiiPeiVariablePpiGuid;
>>>> +
>>>> +#endif
>>>> diff --git a/MdeModulePkg/MdeModulePkg.dec
>>> b/MdeModulePkg/MdeModulePkg.dec
>>>> index 2bcb9f9453..4f4c48b81f 100644
>>>> --- a/MdeModulePkg/MdeModulePkg.dec
>>>> +++ b/MdeModulePkg/MdeModulePkg.dec
>>>> @@ -513,6 +513,9 @@
>>>>      gEdkiiPeiCapsuleOnDiskPpiGuid             = { 0x71a9ea61, 
>>>> 0x5a35, 0x4a5d,
>>> { 0xac, 0xef, 0x9c, 0xf8, 0x6d, 0x6d, 0x67, 0xe0 } }
>>>>      gEdkiiPeiBootInCapsuleOnDiskModePpiGuid   = { 0xb08a11e4, 0xe2b7,
>>> 0x4b75, { 0xb5, 0x15, 0xaf, 0x61, 0x6, 0x68, 0xbf, 0xd1  } }
>>>>
>>>> +  ## Include/Ppi/Variable.h
>>>> +  gEdkiiPeiVariablePpiGuid                  = { 0xe7b2cd04, 0x4b14, 
>>>> 0x44c2, { 0xb7,
>>> 0x48, 0xce, 0xaf, 0x2b, 0x66, 0x4a, 0xb0 } }
>>>> +
>>>>    [Protocols]
>>>>      ## Load File protocol provides capability to load and unload
>>>> EFI image into
>>> memory and execute it.
>>>>      #  Include/Protocol/LoadPe32Image.h
>>>
>>>
>>>
>>>
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