Re: [edk2-devel] [PATCH v2 0/6] Fix PEI Core issue during TemporaryRamMigration

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

On 2019-04-10 09:41:43, Ard Biesheuvel wrote:
> On Wed, 10 Apr 2019 at 01:41, Jordan Justen <jordan.l.justen@intel.com> wrote:
> >
> > https://github.com/jljusten/edk2.git temp-ram-support-v2
> >
> > https://github.com/jljusten/edk2/commits/temp-ram-support-v2
> >
> > v2:
> >  * Add AARCH64 and ARM assembly
> 
> Hi Jordan,
> 
> I'm not sure I'm following the reasoning behind this.

Did you see the explanation in patch 1 commit message? Could you reply
there with questions, or maybe I should try to expand on that?

> Does this fix an issue we currently have on ARM systems?

Yes, but I don't know of a case where it has been observed on
AARCH64/ARM. Nevertheless, as far as I can tell, a similar issue could
happen because the current implementation relies on non-spec'd
behavior of code gen within a C function. (Not the C calling
convention, but what code does with inside the function between
calls.)

> And how did you build and/or test OVMF for ARM?

I built ArmVirtPkg for AARCH64 and ARM on x86_64 Linux with a
cross-compiler, and ran it with qemu.

-Jordan

> 
> >  * Drop IA32 and X64 .S source files
> >  * Adjust PEI_CORE_TEMPORARY_RAM_TRANSITION pointer in the assembly
> >    code based on the stack pointer change before & after
> >    TemporaryRamSupport->TemporaryRamMigration
> >  * Drop extra cleanup patches for OvmfPkg & EmulatorPkg. These were
> >    just complicating the series.
> >
> > This series fixes an issue that, while rare, is possible based on the
> > way the TemporaryRamSupport PPI is defined along with how it is used
> > by the PEI Core.
> >
> > Liu Yu reported a boot issue with EmulatorPkg, which I believe was
> > caused by this issue.
> >
> > The details of the issue are described in the commit message of the
> > "MdeModulePkg/Core/Pei: Add interface for assembly based
> > TemporaryRamSupport" patch.
> >
> > Testing:
> >
> > I tested building and booting in several scenarios:
> >
> > * OVMF IA32 & X64 on Linux
> > * ArmVirtPkg AARCH64 & ARM on x86_64 Linux
> > * EmulatorPkg IA32 & X64 on Linux
> >
> > Untested:
> >
> > * My system does not reproduce the issue that Liu Yu reported with
> >   EmulatorPkg, so I can't say that I have verified that issue.
> > * Building on windows
> > * AARCH64/ARM TemporaryRamMigration.asm sources