Re: [PATCH 00/13] Extend secure variable service to be usable from Standalone MM

From: Jagadeesh Ujja <jagadeesh.ujja@arm.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: "Gao, Liming" <liming.gao@intel.com>,
	 "edk2-devel@lists.01.org" <edk2-devel@lists.01.org>,
	"Zhang, Chao B" <chao.b.zhang@intel.com>
Subject: Re: [PATCH 00/13] Extend secure variable service to be usable from Standalone MM
Date: Thu, 3 Jan 2019 13:13:45 +0530	[thread overview]
Message-ID: <CADpYukY+UGz1oNoYcuf2t67iSWt2bHOqciUV0ML7d23V0WgB=w@mail.gmail.com> (raw)
In-Reply-To: <CAKv+Gu81m3JubLA1=64ePjc3bu6VJ=xTQGpCgDTHf7a4gm6eCA@mail.gmail.com>

hi Ard

On Wed, Jan 2, 2019 at 10:45 PM Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
>
> On Thu, 20 Dec 2018 at 15:23, Gao, Liming <liming.gao@intel.com> wrote:
> >
> > Jagadeesh:
> >   MdeModulePkg Variable service/Fault tolerant/Nor Flash driver depends on StandaloneMmServicesTableLib library class header file. This header file is added into MdePkg. It has two interfaces. One is global gMmst, another is function InMm(). So, there is no dependency issue here.
> > And, MdePkg adds one StandaloneMmServicesTableLib library INF with empty implementation, this library is just for build. It sets gMmst=NULL, and always return FASLE in InMm(). This library can be used in MdeModulePkg.dsc to make Variable driver pass build. There is also no dependency issue here. Last, Platform DSC file will refer to the real StandaloneMmServicesTableLib library INF from StandaloneMmPkg.
> >
>
> I think we should avoid the need for InMm() altogether for standalone
> MM. It will always return TRUE for standalone MM modules, and it will
> always return FALSE for other modules, so the distinction should be
> made at build time.
>
> This means that we need to refactor the SMM 'server' modules and/or
> libraries so that any code they cannot share (like boot services
> invocations) are only included in the classic SMM versions.
>
> I have pushed my own prototype code here:
> https://github.com/ardbiesheuvel/edk2/commits/standalone-mm
>
> There is some overlap with Jagadeesh's work. I will work with him
> directly to resolve this before posting any new revisions.
>
InMm()”  and “PcdStandaloneMmVariableEnabled” are defined to reuse the
existing code as much as possible.
Initially I have done separate copy of the file to avoid “if..else”
but had a comment about “duplicating code primarily due to the
maintenance overhead”

So we are using “InMm()” and “PcdStandaloneMmVariableEnabled” PCD flag
and trying to use the same code as much as possible.

The patchset “Extend secure variable service to be usable from
Standalone MM” as POC was submitted as RFC patches on “October 31,
2018”.
Subsequent comments are fixed and we had 7 version of the patch set
under review.

Thanks
Jagadeesh
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