Re: [edk2] ARM UEFI BIOS & Trusted firmware (SMM / Trustzone similitudes) - boot-architecture

6 Dec 2013

      Eugene and I usually attend, and it is Andrew Sloss running it on the ARM side.
Sent from my iPhone
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On Dec 6, 2013, at 2:14 PM, "Pant, Alok" Alok.Pant@amd.com wrote:
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. But as suggested Eugene, a discussion can be started in the UEFI Forum working groups. ABST (ARM Binding Sub-Team) might be a good place to get the initial feedbacks.
Hi Olivier,
  Thanks. Would you be able to bring this to ABST? Or what do you suggest the next steps?

From: Olivier Martin [mailto:olivier.martin@arm.com] 
Sent: Friday, December 06, 2013 2:05 PM
To: Pant, Alok; Cohen, Eugene; 'Tim Lewis'; edk2-devel@lists.sourceforge.net
Cc: boot-architecture@lists.linaro.org
Subject: RE: ARM UEFI BIOS & Trusted firmware (SMM / Trustzone similitudes)

I have not necessary got the background and the full picture of the industry in term of production firmware compare to some of you. But I have tried to give some answers to your questions.

#  Alok, two directions for Secure Monitor implementation?
The ARM recommendation is everything concerning secure world (EL3, Secure-EL1, Secure-EL0) should be implemented as part of the Trusted Firmware project.
ArmPlatformPkg/Sec has been ported to AArch64 as a temporary solution while waiting for an appropriate Trusted Firmware implementation. There is no plan to have a Secure Monitor implementation (BL31) in Tianocore project.
And I will not accept any patch that implements such feature in Tianocore. The reason is I do not think it is good thing to duplicate code between both projects supported by ARM. And the Trusted Firmware project is a better place for such features.

# Alok, some implementation starts the Trusted Firmware (in EL3) that launches SEC in El1/2 mode
ArmPlatformPkg/Sec should not run in EL2/EL1. As I said earlier, this is only a temporary solution that should be replaced by the Trusted Firmware project on most ARMv8 platforms.
The Trusted Firmware should launch UEFI that starts with either ArmPlatformPkg/PrePeiCore (if the UEFI firmware in XIP ROM) or ArmPlatformPkg/PrePi (if the UEFI firmware is started from DRAM).

# Alok, Should secure monitor (bl31) be launched before or during SEC phase?
Secure Monitor (BL31) is one of the first components loaded by the Trusted Firmware. The Secure Monitor will be available before the UEFI firmware starts.

# Alok/Eugene, Extending the PI SMM specification (Volume 4) for Trustzone
I had a look at the SMM PI spec. I can see a lot of similitude to the UEFI spec (an architecture and implementation agnostic interface).
I can also see some similitude between SMM and Trustzone technology (based on the ARM Secure Extension). And I am sure some SMM drivers will be ported to ARM Secure components (eg: authentification variable for secure boot).

One notable difference between SMM and ‘Trustzone’ is the initialization. SMM seems to be initialized during the DXE phase while the ARM Secure/Trusted environment is initialized prior to start the Non Secure/Non Trusted environment (including UEFI, u-boot bootloaders). And I do not see this initialization phase to be changed for the reason that the secure environment (Trusted Firmware, Trusted OS, SiP/ODM/OEM secure components) will setup the appropriate hardware privileges and initialize their environment prior to switch to the Non-Secure environment.

The concept of ‘extending the PI SMM spec to Trustzone’ or  'some form of SMM foundation glue code' is interesting. But it might be difficult to implement in the current situation (most of the solutions seem to be highly integrated without much interoperability). The level of standardization of the Secure/Trusted environment has not reached the API yet.
Obviously, to create a standard an initiative has to be started. I am probably not the best person (due to my limited knowledge of SMM and their real use cases) to start this initiative. But as suggested Eugene, a discussion can be started in the UEFI Forum working groups. ABST (ARM Binding Sub-Team) might be a good place to get the initial feedbacks.

# Tim, What happens when the secure OS is performing a secure task, but the other OS asks for a shutdown?
As you know PSCI (Power State Coordination Interface) is recommended by ARM for OS Power Management (OSPM). In this case, the Secure world is aware of the shutdown.
But the PSCI spec says 'a Trusted OS must not rely on the use of any notification, and must be resistant to any sudden loss of context'.
Trusted OS vendors are expected to provide a Rich OS driver to invoke their services. There are probably ways to signal a Rich OS shutdown to the Trusted OS using this driver.

Thanks,
Olivier

From: Pant, Alok [mailto:Alok.Pant@amd.com] 
Sent: 05 December 2013 18:08
To: edk2-devel@lists.sourceforge.net; Olivier Martin
Subject: RE: ARM UEFI BIOS & Trusted firmware

Hi Tim & Eugene,
  Thanks for the response. I agree current SMM foundation code gas some IA specific and there are various gotchas around SMM entry/exit (sync core , save restore etc, base protocol), however most of SMM foundation is generic and it provides a nice framework of independent driver and interaction via protocol and use common services; granted the DXE SMMipl role of launching and building initial SMM environment does not mesh well on ARM. In parallel there is separate work on ARM trusted firmware and seems there is no common ground between two. I am very must interested to hear how others are attempting to address such feature porting issue and the direction from industry toward runtime EL3 support (single monolithic TF binary+some proprietary form of RTOS “vs.” attempt to integrate UEFI SMM with trusted fw core). I am sure I am not the first one stumbling on this question and seeking how others attempted to solve the above and if this a broader issue that need to be further discussed in this forum.

Thanks
-Alok

From: Tim Lewis [mailto:tim.lewis@insyde.com] 
Sent: Thursday, December 05, 2013 11:39 AM
To: edk2-devel@lists.sourceforge.net; olivier.martin@arm.com
Subject: Re: [edk2] ARM UEFI BIOS & Trusted firmware

Eugene –

One of the issues for the SMM specification and TZ is the single-threaded nature. While most of ARM’s TrustZone infrastructure can be mapped easily to SMM, the possibility of having cores in TZ and out of TZ simultaneously, or more than one core in TZ at the same time raises some interesting issues (resource contention, etc.)

Tim

From: Cohen, Eugene [mailto:eugene@hp.com] 
Sent: Thursday, December 05, 2013 9:29 AM
To: edk2-devel@lists.sourceforge.net; olivier.martin@arm.com
Subject: Re: [edk2] ARM UEFI BIOS & Trusted firmware

Alok,

I agree -- there is value in the modular nature of the PI component approach extending to the ARM trusted firmware environment.

For SMM this is supported in the PI spec’s SMM core interface specification and in edk2 by the PiSmmCore module and accompanying libraries.  Unlike DXE and PEI, the SMM core, at least in name, is IA-specific as it refers to SMM, SMIs, SMRAM, etc.   When you look past the names though you can see that the functions it is providing is really architecture independent -- IO protocols, secure memory allocation, protocol management, and handler registration.  Given the current IA-specific naming, it would be difficult to recommend that ARM should simply adopt the “SMM” core architecture for the TZ/EL3/SecureMonitor implementation.

Perhaps this should be raised in the PI working group, specifically “is the SMM core interface spec really an IA-specific concept or something that should become architecture agnostic?”

Eugene

From: Pant, Alok [mailto:Alok.Pant@amd.com] 
Sent: Thursday, December 05, 2013 8:42 AM
To: edk2-devel@lists.sourceforge.net; olivier.martin@arm.com
Subject: [edk2] ARM UEFI BIOS & Trusted firmware

Changing topic..

Hi Oliver, Thanks. I also I have few separate questions wrt to Trusted firmware & UEFI ARM code and hope you/others can help answer

·         It seems there are two direction for SecureMonitor implementation. In one implementation the SEC code (ArmPlatformPkg\Sec\Sec.c) install the secure monitor ( when SEC start in El3) ; In other implementation the Trusted firmware start first install secure monitor (bl31) and launch SEC in El1/2 mode. My question is what is the preferred direction when both are possible? Should secure monitor (bl31) be launched before or during SEC phase?
·         Historically in x86 implementation the SMM mode hosts various runtime platform BIOS driver for feature such as authentication variable (for secure boot), platform runtime handing handling etc. EDKII has a good framework for SMM kernel and loading various independent SMM driver and interaction among those driver via protocol etc. In ARM based UEFI/Trusted firmware implementation what may be preferred way to deal with such need. Should all those UEFI SMM driver be ported to Trusted firmware which "today" is in primitive framework compare to SMM EDKII foundation code, or some form of SMM foundation can gel with  trusted firmware design to allow independent platform el3 code be developed at independent driver. Curious how others have attempted to solve this problem and if there can be standard way for all of us to adopt here. Before creating yet another method I was hoping to hear from experts on any common ground for such feature implementation

Thanks again for all your help and comments
-Alok

-----Original Message-----
From: Olivier Martin [mailto:olivier.martin@arm.com] 
Sent: Wednesday, December 04, 2013 7:40 AM
To: TigerLiu@viatech.com.cn; edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] SEC code support big.LITTLE tech?

Hi Tiger,

The ARM recommendation to manage secondary CPUs (the primary CPU is the CPU that runs UEFI and starts your OS kernel) is to use PSCI (Power State Coordination Interface - http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0022b/index.h
tml).
PSCI uses SMCs (Secure Memory Calls) to bring up secondary CPUs (CPU_UP / CPU_DOWN). This code runs in Secure World while UEFI runs in Non-Secure World.

For the story... I started to implement PSCI support in Tianocore source code (in ArmPlatformPkg/Sec). But the EDK2 framework (PCD/Library/INF/FDF
etc) had made the code quite hard to maintain.
So, I wrote a new secure firmware framework project to handle this support.
This firmware is not Open Source (available in binary format for TC2 only).
A new project has been started by ARM Ltd last month. It is an Open Source implementation of the Trusted/Secure Firmware:
https://github.com/ARM-software/arm-trusted-firmware
Unfortunately at this stage, 32bit is not supported (only AArch64 is supported). And as far as I know there is no plan to add 32bit support by ARM Ltd in the short term.

The current ArmPlatformPkg/Sec has support to hold the secondary cores in WFI. But it does not support PSCI. The current support might be sufficient enough for you at this stage.

Thanks,
Olivier
...
-----Original Message-----
From: TigerLiu@viatech.com.cn [mailto:TigerLiu@viatech.com.cn]
Sent: 04 December 2013 01:51
To: edk2-devel@lists.sourceforge.net
Cc: Olivier Martin
Subject: [edk2] SEC code support big.LITTLE tech?
Hi, Oliver:
Does current ArmPlatformPackage's sec code support big.LITTLE tech?
Such as :
An ARM SOC --- with 4 Cores Cortex-A15, 4 Cores Cortex-A7
So, if sec code support big.LITTLE tech, how does it let one core as
boot strap cpu, others go into wfe(or other sleeping state)?
Best wishes,

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