Re: [PATCH 4/6] MdeModulePkg/FaultTolerantWriteDxe: implement standalone MM version

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On Thu, 10 Jan 2019 at 14:03, Laszlo Ersek <lersek@redhat.com> wrote:
>
> On 01/10/19 08:59, Zeng, Star wrote:
> > On 2019/1/10 15:33, Ard Biesheuvel wrote:
> >> On Thu, 10 Jan 2019 at 08:30, Zeng, Star <star.zeng@intel.com> wrote:
> >>>
> >>> Hi Ard,
> >>>
> >>> Another minor feedback.
> >>>
> >>> On 2019/1/10 14:47, Zeng, Star wrote:
> >>>> Hi Ard,
> >>>>
> >>>> Some minor feedback added inline.
> >>>>
> >>>> On 2019/1/4 2:28, Ard Biesheuvel wrote:
> >>>>> Implement a new version of the fault tolerant write driver that can
> >>>>> be used in the context of a standalone MM implementation.
> >>>>>
> >>>>> Contributed-under: TianoCore Contribution Agreement 1.1
> >>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>>>> ---
> >>>>>
> >>>>> MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteStandaloneMm.c
> >>>>>
> >>>>> | 70 +++++++++++++++
> >>>>>
> >>>>> MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWriteStandaloneMm.inf
> >>>>>
> >>>>> | 90 ++++++++++++++++++++
> >>>>>    2 files changed, 160 insertions(+)
> >>>
> >>> Please add it into MdeModulePkg.dsc for package build verification.
> >>>
> >>
> >> Hello Star,
> >>
> >> Thanks for all the feedback. I will respond in more detail later.
> >>
> >> However, to the point raised here: it is not possible to add these
> >> drivers to MdeModulePkg.dsc unless we add a dummy implementation of
> >> StandaloneMmDriverEntryPoint to MdeModulePkg. Do you think we should
> >> do that?
> >
> > Oh, good information.
> > To have full code building coverage for the package, personally I think
> > we can move StandaloneMmDriverEntryPoint library class and instance into
> > MdePkg, and even the MmServicesTableLib for MM_STANDALONE, they should
> > be generic enough.
> >
> > I do not want to block this patch set because of this. So let's discuss
> > this in parallel as separated topic.
> >
> > Mike, Liming, Laszlo, Jian and Hao,\
> > What's your opinion?
>
> It should be possible to build all library instances in a central
> Package (well, all Packages really), using the Package's DSC file. To my
> understanding, libraries built like this are not expected to be used in
> actual (shipped) drivers / applications, nor is their indiscriminate
> distribution (as LIBs) expected. For example, shipping a BaseXxxLibNull
> library instance in binary form seems quite useless.
>
> With that in mind, I think a Null instance for the entry point in
> question makes sense, under MdeModulePkg.
>

I will look into this a bit deeper next week. I think it makes sense
for the core PI architected pieces to all live in MdePkg rather than
StandaloneMmPkg. For instance, MmServicesTableLib for standalone MM
should live there, MmEntryPoint should live there (and have
traditional and standalone MM implementation) and perhaps some other
core pieces as well.

This may be a slippery slope, so I will dedicate some time to look
into this carefully, at least with the goal to make the
FaultTolerantWrite and Variable driver buildable from within
MdeModulePkg.