Re: [PATCH 00/10] Fix PEI Core issue during TemporaryRamMigration

[Jordan Justen <jordan.l.justen@intel.com>]

On 2019-02-20 16:15:59, Ni, Ray wrote:
> > -----Original Message-----
> > From: Justen, Jordan L <jordan.l.justen@intel.com>
> > Sent: Thursday, February 21, 2019 1:44 AM
> > To: Gao, Liming <liming.gao@intel.com>; Ni, Ray <ray.ni@intel.com>; edk2-
> > devel@lists.01.org
> > Cc: Wu, Hao A <hao.a.wu@intel.com>; Anthony Perard
> > <anthony.perard@citrix.com>; Laszlo Ersek <lersek@redhat.com>; Zeng,
> > Star <star.zeng@intel.com>
> > Subject: Re: [PATCH 00/10] Fix PEI Core issue during TemporaryRamMigration
> > 
> > On 2019-02-20 05:27:21, Ni, Ray wrote:
> > > On 2/19/2019 9:25 PM, Gao, Liming wrote:
> > > > Ray:
> > > >
> > > >      Now, real platform has no side effect. So, only TempRamDone
> > > >      PPI is produced. For emulator platform, is there any side
> > > >      effect when both Temporary RAM and Permanent RAM are enabled?
> > > >
> > >
> > > No side effect when both of T-RAM and P-RAM are enabled.
> > > Which means no side effect when neither of the PPIs is produced.
> > > But for demo purpose, I think producing TemporaryRamDone PPI makes
> > sense.
> > 
> > In addition to being a demo/sample, it also provides a check that no modules
> > are accessing temp-ram after temp-ram should no longer be used.
> > 
> > > I will work out patches for EmulatorPkg to produce TemoraryRamDone.
> > 
> > I think we should first fix TemporaryRamSupport usage. Otherwise, we are
> > just hiding the bug.
> > 
> > Have you tried these patches to verify that they fix the issue in your setup?
> > Have you taken a look at the patches to see what problem is being fixed?
> 
> I feel the change to PeiCore is a bit complex and introduce additional deps (assembly).

I asked about this last November, and as I recall, Andrew said we can
(and should) add assembly to PEI Core if it is required to meet the
specs.

> Behavior of ARM and x86 becomes different. (The patch only fixes x86 issue.)

Yes. Similar code should be written for ARM, but I don't have
experience with ARM assembly code.

> Given there is no real requirement on this,

Isn't the requirement to be compatible with the PI specification?

It seems that at least you and Liu Yu have encountered a build
environment that produces code for PEI Core that isn't compatible with
the PI specification.

It doesn't seem like the best response to this is to just change the
platform boot path and ignore the bug.

I do agree that after this issue is fixed, we can then consider
changing the platform. The downside to changing it then will be to
leave an untested code path, but at least we won't leave it with a
known bug present.

-Jordan

> I prefer to not change PeiCore.