Re: [PATCH edk2-platforms 6/7] Platform/DeveloperBox: add .DSC/.FDF description of MM components

[Leif Lindholm <leif.lindholm@linaro.org>]

On Thu, Jan 17, 2019 at 12:10:01PM +0100, Ard Biesheuvel wrote:
> > >  ################################################################################
> > >  #
> > > @@ -294,8 +295,10 @@ [PcdsFixedAtBuild.common]
> > >  !endif
> > >    gEfiMdeModulePkgTokenSpaceGuid.PcdFirmwareRevision|$(BUILD_NUMBER)
> > >
> > > -  gArmTokenSpaceGuid.PcdMmBufferBase|0xFFC00000
> > > -  gArmTokenSpaceGuid.PcdMmBufferSize|0x00200000
> > > +  gEfiSecurityPkgTokenSpaceGuid.PcdUserPhysicalPresence|TRUE
> >
> > So, I can see why you add this hard-wired for the purpose of testing.
> > But please, add a *very* conspicuous, and strongly worded, comment
> > statement preceding it.
> 
> Well, I was talking to Peter about this the other day: according to
> the spec, this setting should only matter before exit boot services,
> and since this platform only supports serial and GOP consoles, one
> could argue that only a physically present user could interact with it
> before that time.

But that also makes the Pcd pointless.

> The obvious way of implementing this non-trivially on this platform is
> to use a DIP switch, but that requires you to open the case to
> enroll/delete the platform key. Perhaps that does not matter, and it
> would in fact produce a less dangerous reference implementation.

I would be totally OK with that.
I would also be totally OK with a DynamicPcd settable through the UI
(which is what most machines I come across have).

But I would also be cool with a sufficiently evil "here be dragons"
statement, pointing out that we don't care that much
*on*this*specific*system* because the NOR isn't actually hw protected
anyway, and this implementation is all about exercising the software
stack..

/
    Leif