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

["Laszlo Ersek" <lersek@redhat.com>]

On 04/10/19 18:41, 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. Does this fix an
> issue we currently have on ARM systems?

IIUC, the PEI Core can only be updated to use the "safe path" (= the
assembly path) on IA32/X64 if that path (= the assembly path) *exists*
regardless of architecture.

This is anyway my understanding of the last commit message in the series.

I can't evaluate whether the problem statement, in the first commit
message in the series, would ever turn into an actual issue on
ARM/AARCH64, dependent on toolchain. On IA32/X64, we've seen examples
(although none of those have bit me personally), and AIUI the issue
could theoretically apply to all arches (again, dependent on toolchain).

(Apologies if I've only increased the confusion with this -- but at
least it could help me improve my own understanding.)

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

Hmmm, I'm unsure where this question / implication comes from. AIUI, the
new ARM/AARCH64 assembly is automatically put to use if you run the PEI
Core -- as part of a firmware platform that uses temp RAM migration --
on ARM/AARCH64.

Thanks,
Laszlo

> 
> 
>>  * 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
>>
>> Cc: Liu Yu <pedroa.liu@outlook.com>
>> Cc: Ray Ni <ray.ni@intel.com>
>> Cc: Andrew Fish <afish@apple.com>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Cc: Leif Lindholm <leif.lindholm@linaro.org>
>> Cc: Michael D Kinney <michael.d.kinney@intel.com>
>>
>> Jordan Justen (6):
>>   MdeModulePkg/Core/Pei: Add interface for assembly based
>>     TemporaryRamSupport
>>   MdeModulePkg/Core/Pei: Add AARCH64 assembly for TemporaryRamMigration
>>   MdeModulePkg/Core/Pei: Add ARM assembly for TemporaryRamMigration
>>   MdeModulePkg/Core/Pei: Add IA32 assembly for TemporaryRamMigration
>>   MdeModulePkg/Core/Pei: Add X64 assembly for TemporaryRamMigration
>>   MdeModulePkg/Core/Pei: Use code path for assembly based
>>     TemporaryRamSupport
>>
>>  .../AArch64/TemporaryRamMigration.S           | 63 +++++++++++++++
>>  .../AArch64/TemporaryRamMigration.asm         | 63 +++++++++++++++
>>  .../Dispatcher/Arm/TemporaryRamMigration.S    | 68 ++++++++++++++++
>>  .../Dispatcher/Arm/TemporaryRamMigration.asm  | 68 ++++++++++++++++
>>  MdeModulePkg/Core/Pei/Dispatcher/Dispatcher.c | 59 +++++++++-----
>>  .../Ia32/TemporaryRamMigration.nasm           | 77 +++++++++++++++++++
>>  .../Dispatcher/X64/TemporaryRamMigration.nasm | 74 ++++++++++++++++++
>>  MdeModulePkg/Core/Pei/PeiMain.h               | 52 +++++++++++++
>>  MdeModulePkg/Core/Pei/PeiMain.inf             | 15 ++++
>>  9 files changed, 518 insertions(+), 21 deletions(-)
>>  create mode 100644 MdeModulePkg/Core/Pei/Dispatcher/AArch64/TemporaryRamMigration.S
>>  create mode 100644 MdeModulePkg/Core/Pei/Dispatcher/AArch64/TemporaryRamMigration.asm
>>  create mode 100644 MdeModulePkg/Core/Pei/Dispatcher/Arm/TemporaryRamMigration.S
>>  create mode 100644 MdeModulePkg/Core/Pei/Dispatcher/Arm/TemporaryRamMigration.asm
>>  create mode 100644 MdeModulePkg/Core/Pei/Dispatcher/Ia32/TemporaryRamMigration.nasm
>>  create mode 100644 MdeModulePkg/Core/Pei/Dispatcher/X64/TemporaryRamMigration.nasm
>>
>> --
>> 2.20.1
>>
>>
>> 
>>